delayacct: track delays from memory compact

[linux.git] / mm / page_alloc.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/mm/page_alloc.c
 *
 *  Manages the free list, the system allocates free pages here.
 *  Note that kmalloc() lives in slab.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 *  Reshaped it to be a zoned allocator, Ingo Molnar, Red Hat, 1999
 *  Discontiguous memory support, Kanoj Sarcar, SGI, Nov 1999
 *  Zone balancing, Kanoj Sarcar, SGI, Jan 2000
 *  Per cpu hot/cold page lists, bulk allocation, Martin J. Bligh, Sept 2002
 *          (lots of bits borrowed from Ingo Molnar & Andrew Morton)
 */

#include <linux/stddef.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/interrupt.h>
#include <linux/pagemap.h>
#include <linux/jiffies.h>
#include <linux/memblock.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/kasan.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>
#include <linux/oom.h>
#include <linux/topology.h>
#include <linux/sysctl.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/memory_hotplug.h>
#include <linux/nodemask.h>
#include <linux/vmalloc.h>
#include <linux/vmstat.h>
#include <linux/mempolicy.h>
#include <linux/memremap.h>
#include <linux/stop_machine.h>
#include <linux/random.h>
#include <linux/sort.h>
#include <linux/pfn.h>
#include <linux/backing-dev.h>
#include <linux/fault-inject.h>
#include <linux/page-isolation.h>
#include <linux/debugobjects.h>
#include <linux/kmemleak.h>
#include <linux/compaction.h>
#include <trace/events/kmem.h>
#include <trace/events/oom.h>
#include <linux/prefetch.h>
#include <linux/mm_inline.h>
#include <linux/mmu_notifier.h>
#include <linux/migrate.h>
#include <linux/hugetlb.h>
#include <linux/sched/rt.h>
#include <linux/sched/mm.h>
#include <linux/page_owner.h>
#include <linux/kthread.h>
#include <linux/memcontrol.h>
#include <linux/ftrace.h>
#include <linux/lockdep.h>
#include <linux/nmi.h>
#include <linux/psi.h>
#include <linux/padata.h>
#include <linux/khugepaged.h>
#include <linux/buffer_head.h>
#include <linux/delayacct.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
#include "internal.h"
#include "shuffle.h"
#include "page_reporting.h"

/* Free Page Internal flags: for internal, non-pcp variants of free_pages(). */
typedef int __bitwise fpi_t;

/* No special request */
#define FPI_NONE                ((__force fpi_t)0)

/*
 * Skip free page reporting notification for the (possibly merged) page.
 * This does not hinder free page reporting from grabbing the page,
 * reporting it and marking it "reported" -  it only skips notifying
 * the free page reporting infrastructure about a newly freed page. For
 * example, used when temporarily pulling a page from a freelist and
 * putting it back unmodified.
 */
#define FPI_SKIP_REPORT_NOTIFY  ((__force fpi_t)BIT(0))

/*
 * Place the (possibly merged) page to the tail of the freelist. Will ignore
 * page shuffling (relevant code - e.g., memory onlining - is expected to
 * shuffle the whole zone).
 *
 * Note: No code should rely on this flag for correctness - it's purely
 *       to allow for optimizations when handing back either fresh pages
 *       (memory onlining) or untouched pages (page isolation, free page
 *       reporting).
 */
#define FPI_TO_TAIL             ((__force fpi_t)BIT(1))

/*
 * Don't poison memory with KASAN (only for the tag-based modes).
 * During boot, all non-reserved memblock memory is exposed to page_alloc.
 * Poisoning all that memory lengthens boot time, especially on systems with
 * large amount of RAM. This flag is used to skip that poisoning.
 * This is only done for the tag-based KASAN modes, as those are able to
 * detect memory corruptions with the memory tags assigned by default.
 * All memory allocated normally after boot gets poisoned as usual.
 */
#define FPI_SKIP_KASAN_POISON   ((__force fpi_t)BIT(2))

/* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
static DEFINE_MUTEX(pcp_batch_high_lock);
#define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)

struct pagesets {
        local_lock_t lock;
};
static DEFINE_PER_CPU(struct pagesets, pagesets) = {
        .lock = INIT_LOCAL_LOCK(lock),
};

#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node);
#endif

DEFINE_STATIC_KEY_TRUE(vm_numa_stat_key);

#ifdef CONFIG_HAVE_MEMORYLESS_NODES
/*
 * N.B., Do NOT reference the '_numa_mem_' per cpu variable directly.
 * It will not be defined when CONFIG_HAVE_MEMORYLESS_NODES is not defined.
 * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem()
 * defined in <linux/topology.h>.
 */
DEFINE_PER_CPU(int, _numa_mem_);                /* Kernel "local memory" node */
EXPORT_PER_CPU_SYMBOL(_numa_mem_);
#endif

/* work_structs for global per-cpu drains */
struct pcpu_drain {
        struct zone *zone;
        struct work_struct work;
};
static DEFINE_MUTEX(pcpu_drain_mutex);
static DEFINE_PER_CPU(struct pcpu_drain, pcpu_drain);

#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
volatile unsigned long latent_entropy __latent_entropy;
EXPORT_SYMBOL(latent_entropy);
#endif

/*
 * Array of node states.
 */
nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
        [N_POSSIBLE] = NODE_MASK_ALL,
        [N_ONLINE] = { { [0] = 1UL } },
#ifndef CONFIG_NUMA
        [N_NORMAL_MEMORY] = { { [0] = 1UL } },
#ifdef CONFIG_HIGHMEM
        [N_HIGH_MEMORY] = { { [0] = 1UL } },
#endif
        [N_MEMORY] = { { [0] = 1UL } },
        [N_CPU] = { { [0] = 1UL } },
#endif  /* NUMA */
};
EXPORT_SYMBOL(node_states);

atomic_long_t _totalram_pages __read_mostly;
EXPORT_SYMBOL(_totalram_pages);
unsigned long totalreserve_pages __read_mostly;
unsigned long totalcma_pages __read_mostly;

int percpu_pagelist_high_fraction;
gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
EXPORT_SYMBOL(init_on_alloc);

DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
EXPORT_SYMBOL(init_on_free);

static bool _init_on_alloc_enabled_early __read_mostly
                                = IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON);
static int __init early_init_on_alloc(char *buf)
{

        return kstrtobool(buf, &_init_on_alloc_enabled_early);
}
early_param("init_on_alloc", early_init_on_alloc);

static bool _init_on_free_enabled_early __read_mostly
                                = IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON);
static int __init early_init_on_free(char *buf)
{
        return kstrtobool(buf, &_init_on_free_enabled_early);
}
early_param("init_on_free", early_init_on_free);

/*
 * A cached value of the page's pageblock's migratetype, used when the page is
 * put on a pcplist. Used to avoid the pageblock migratetype lookup when
 * freeing from pcplists in most cases, at the cost of possibly becoming stale.
 * Also the migratetype set in the page does not necessarily match the pcplist
 * index, e.g. page might have MIGRATE_CMA set but be on a pcplist with any
 * other index - this ensures that it will be put on the correct CMA freelist.
 */
static inline int get_pcppage_migratetype(struct page *page)
{
        return page->index;
}

static inline void set_pcppage_migratetype(struct page *page, int migratetype)
{
        page->index = migratetype;
}

#ifdef CONFIG_PM_SLEEP
/*
 * The following functions are used by the suspend/hibernate code to temporarily
 * change gfp_allowed_mask in order to avoid using I/O during memory allocations
 * while devices are suspended.  To avoid races with the suspend/hibernate code,
 * they should always be called with system_transition_mutex held
 * (gfp_allowed_mask also should only be modified with system_transition_mutex
 * held, unless the suspend/hibernate code is guaranteed not to run in parallel
 * with that modification).
 */

static gfp_t saved_gfp_mask;

void pm_restore_gfp_mask(void)
{
        WARN_ON(!mutex_is_locked(&system_transition_mutex));
        if (saved_gfp_mask) {
                gfp_allowed_mask = saved_gfp_mask;
                saved_gfp_mask = 0;
        }
}

void pm_restrict_gfp_mask(void)
{
        WARN_ON(!mutex_is_locked(&system_transition_mutex));
        WARN_ON(saved_gfp_mask);
        saved_gfp_mask = gfp_allowed_mask;
        gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);
}

bool pm_suspended_storage(void)
{
        if ((gfp_allowed_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
                return false;
        return true;
}
#endif /* CONFIG_PM_SLEEP */

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
unsigned int pageblock_order __read_mostly;
#endif

static void __free_pages_ok(struct page *page, unsigned int order,
                            fpi_t fpi_flags);

/*
 * results with 256, 32 in the lowmem_reserve sysctl:
 *      1G machine -> (16M dma, 800M-16M normal, 1G-800M high)
 *      1G machine -> (16M dma, 784M normal, 224M high)
 *      NORMAL allocation will leave 784M/256 of ram reserved in the ZONE_DMA
 *      HIGHMEM allocation will leave 224M/32 of ram reserved in ZONE_NORMAL
 *      HIGHMEM allocation will leave (224M+784M)/256 of ram reserved in ZONE_DMA
 *
 * TBD: should special case ZONE_DMA32 machines here - in those we normally
 * don't need any ZONE_NORMAL reservation
 */
int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = {
#ifdef CONFIG_ZONE_DMA
        [ZONE_DMA] = 256,
#endif
#ifdef CONFIG_ZONE_DMA32
        [ZONE_DMA32] = 256,
#endif
        [ZONE_NORMAL] = 32,
#ifdef CONFIG_HIGHMEM
        [ZONE_HIGHMEM] = 0,
#endif
        [ZONE_MOVABLE] = 0,
};

static char * const zone_names[MAX_NR_ZONES] = {
#ifdef CONFIG_ZONE_DMA
         "DMA",
#endif
#ifdef CONFIG_ZONE_DMA32
         "DMA32",
#endif
         "Normal",
#ifdef CONFIG_HIGHMEM
         "HighMem",
#endif
         "Movable",
#ifdef CONFIG_ZONE_DEVICE
         "Device",
#endif
};

const char * const migratetype_names[MIGRATE_TYPES] = {
        "Unmovable",
        "Movable",
        "Reclaimable",
        "HighAtomic",
#ifdef CONFIG_CMA
        "CMA",
#endif
#ifdef CONFIG_MEMORY_ISOLATION
        "Isolate",
#endif
};

compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {
        [NULL_COMPOUND_DTOR] = NULL,
        [COMPOUND_PAGE_DTOR] = free_compound_page,
#ifdef CONFIG_HUGETLB_PAGE
        [HUGETLB_PAGE_DTOR] = free_huge_page,
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        [TRANSHUGE_PAGE_DTOR] = free_transhuge_page,
#endif
};

int min_free_kbytes = 1024;
int user_min_free_kbytes = -1;
int watermark_boost_factor __read_mostly = 15000;
int watermark_scale_factor = 10;

static unsigned long nr_kernel_pages __initdata;
static unsigned long nr_all_pages __initdata;
static unsigned long dma_reserve __initdata;

static unsigned long arch_zone_lowest_possible_pfn[MAX_NR_ZONES] __initdata;
static unsigned long arch_zone_highest_possible_pfn[MAX_NR_ZONES] __initdata;
static unsigned long required_kernelcore __initdata;
static unsigned long required_kernelcore_percent __initdata;
static unsigned long required_movablecore __initdata;
static unsigned long required_movablecore_percent __initdata;
static unsigned long zone_movable_pfn[MAX_NUMNODES] __initdata;
static bool mirrored_kernelcore __meminitdata;

/* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
int movable_zone;
EXPORT_SYMBOL(movable_zone);

#if MAX_NUMNODES > 1
unsigned int nr_node_ids __read_mostly = MAX_NUMNODES;
unsigned int nr_online_nodes __read_mostly = 1;
EXPORT_SYMBOL(nr_node_ids);
EXPORT_SYMBOL(nr_online_nodes);
#endif

int page_group_by_mobility_disabled __read_mostly;

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
/*
 * During boot we initialize deferred pages on-demand, as needed, but once
 * page_alloc_init_late() has finished, the deferred pages are all initialized,
 * and we can permanently disable that path.
 */
static DEFINE_STATIC_KEY_TRUE(deferred_pages);

/*
 * Calling kasan_poison_pages() only after deferred memory initialization
 * has completed. Poisoning pages during deferred memory init will greatly
 * lengthen the process and cause problem in large memory systems as the
 * deferred pages initialization is done with interrupt disabled.
 *
 * Assuming that there will be no reference to those newly initialized
 * pages before they are ever allocated, this should have no effect on
 * KASAN memory tracking as the poison will be properly inserted at page
 * allocation time. The only corner case is when pages are allocated by
 * on-demand allocation and then freed again before the deferred pages
 * initialization is done, but this is not likely to happen.
 */
static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
{
        return static_branch_unlikely(&deferred_pages) ||
               (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
                (fpi_flags & FPI_SKIP_KASAN_POISON)) ||
               PageSkipKASanPoison(page);
}

/* Returns true if the struct page for the pfn is uninitialised */
static inline bool __meminit early_page_uninitialised(unsigned long pfn)
{
        int nid = early_pfn_to_nid(pfn);

        if (node_online(nid) && pfn >= NODE_DATA(nid)->first_deferred_pfn)
                return true;

        return false;
}

/*
 * Returns true when the remaining initialisation should be deferred until
 * later in the boot cycle when it can be parallelised.
 */
static bool __meminit
defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
{
        static unsigned long prev_end_pfn, nr_initialised;

        /*
         * prev_end_pfn static that contains the end of previous zone
         * No need to protect because called very early in boot before smp_init.
         */
        if (prev_end_pfn != end_pfn) {
                prev_end_pfn = end_pfn;
                nr_initialised = 0;
        }

        /* Always populate low zones for address-constrained allocations */
        if (end_pfn < pgdat_end_pfn(NODE_DATA(nid)))
                return false;

        if (NODE_DATA(nid)->first_deferred_pfn != ULONG_MAX)
                return true;
        /*
         * We start only with one section of pages, more pages are added as
         * needed until the rest of deferred pages are initialized.
         */
        nr_initialised++;
        if ((nr_initialised > PAGES_PER_SECTION) &&
            (pfn & (PAGES_PER_SECTION - 1)) == 0) {
                NODE_DATA(nid)->first_deferred_pfn = pfn;
                return true;
        }
        return false;
}
#else
static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
{
        return (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
                (fpi_flags & FPI_SKIP_KASAN_POISON)) ||
               PageSkipKASanPoison(page);
}

static inline bool early_page_uninitialised(unsigned long pfn)
{
        return false;
}

static inline bool defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
{
        return false;
}
#endif

/* Return a pointer to the bitmap storing bits affecting a block of pages */
static inline unsigned long *get_pageblock_bitmap(const struct page *page,
                                                        unsigned long pfn)
{
#ifdef CONFIG_SPARSEMEM
        return section_to_usemap(__pfn_to_section(pfn));
#else
        return page_zone(page)->pageblock_flags;
#endif /* CONFIG_SPARSEMEM */
}

static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn)
{
#ifdef CONFIG_SPARSEMEM
        pfn &= (PAGES_PER_SECTION-1);
#else
        pfn = pfn - round_down(page_zone(page)->zone_start_pfn, pageblock_nr_pages);
#endif /* CONFIG_SPARSEMEM */
        return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
}

static __always_inline
unsigned long __get_pfnblock_flags_mask(const struct page *page,
                                        unsigned long pfn,
                                        unsigned long mask)
{
        unsigned long *bitmap;
        unsigned long bitidx, word_bitidx;
        unsigned long word;

        bitmap = get_pageblock_bitmap(page, pfn);
        bitidx = pfn_to_bitidx(page, pfn);
        word_bitidx = bitidx / BITS_PER_LONG;
        bitidx &= (BITS_PER_LONG-1);

        word = bitmap[word_bitidx];
        return (word >> bitidx) & mask;
}

/**
 * get_pfnblock_flags_mask - Return the requested group of flags for the pageblock_nr_pages block of pages
 * @page: The page within the block of interest
 * @pfn: The target page frame number
 * @mask: mask of bits that the caller is interested in
 *
 * Return: pageblock_bits flags
 */
unsigned long get_pfnblock_flags_mask(const struct page *page,
                                        unsigned long pfn, unsigned long mask)
{
        return __get_pfnblock_flags_mask(page, pfn, mask);
}

static __always_inline int get_pfnblock_migratetype(const struct page *page,
                                        unsigned long pfn)
{
        return __get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK);
}

/**
 * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
 * @page: The page within the block of interest
 * @flags: The flags to set
 * @pfn: The target page frame number
 * @mask: mask of bits that the caller is interested in
 */
void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
                                        unsigned long pfn,
                                        unsigned long mask)
{
        unsigned long *bitmap;
        unsigned long bitidx, word_bitidx;
        unsigned long old_word, word;

        BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
        BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));

        bitmap = get_pageblock_bitmap(page, pfn);
        bitidx = pfn_to_bitidx(page, pfn);
        word_bitidx = bitidx / BITS_PER_LONG;
        bitidx &= (BITS_PER_LONG-1);

        VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);

        mask <<= bitidx;
        flags <<= bitidx;

        word = READ_ONCE(bitmap[word_bitidx]);
        for (;;) {
                old_word = cmpxchg(&bitmap[word_bitidx], word, (word & ~mask) | flags);
                if (word == old_word)
                        break;
                word = old_word;
        }
}

void set_pageblock_migratetype(struct page *page, int migratetype)
{
        if (unlikely(page_group_by_mobility_disabled &&
                     migratetype < MIGRATE_PCPTYPES))
                migratetype = MIGRATE_UNMOVABLE;

        set_pfnblock_flags_mask(page, (unsigned long)migratetype,
                                page_to_pfn(page), MIGRATETYPE_MASK);
}

#ifdef CONFIG_DEBUG_VM
static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
{
        int ret = 0;
        unsigned seq;
        unsigned long pfn = page_to_pfn(page);
        unsigned long sp, start_pfn;

        do {
                seq = zone_span_seqbegin(zone);
                start_pfn = zone->zone_start_pfn;
                sp = zone->spanned_pages;
                if (!zone_spans_pfn(zone, pfn))
                        ret = 1;
        } while (zone_span_seqretry(zone, seq));

        if (ret)
                pr_err("page 0x%lx outside node %d zone %s [ 0x%lx - 0x%lx ]\n",
                        pfn, zone_to_nid(zone), zone->name,
                        start_pfn, start_pfn + sp);

        return ret;
}

static int page_is_consistent(struct zone *zone, struct page *page)
{
        if (zone != page_zone(page))
                return 0;

        return 1;
}
/*
 * Temporary debugging check for pages not lying within a given zone.
 */
static int __maybe_unused bad_range(struct zone *zone, struct page *page)
{
        if (page_outside_zone_boundaries(zone, page))
                return 1;
        if (!page_is_consistent(zone, page))
                return 1;

        return 0;
}
#else
static inline int __maybe_unused bad_range(struct zone *zone, struct page *page)
{
        return 0;
}
#endif

static void bad_page(struct page *page, const char *reason)
{
        static unsigned long resume;
        static unsigned long nr_shown;
        static unsigned long nr_unshown;

        /*
         * Allow a burst of 60 reports, then keep quiet for that minute;
         * or allow a steady drip of one report per second.
         */
        if (nr_shown == 60) {
                if (time_before(jiffies, resume)) {
                        nr_unshown++;
                        goto out;
                }
                if (nr_unshown) {
                        pr_alert(
                              "BUG: Bad page state: %lu messages suppressed\n",
                                nr_unshown);
                        nr_unshown = 0;
                }
                nr_shown = 0;
        }
        if (nr_shown++ == 0)
                resume = jiffies + 60 * HZ;

        pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
                current->comm, page_to_pfn(page));
        dump_page(page, reason);

        print_modules();
        dump_stack();
out:
        /* Leave bad fields for debug, except PageBuddy could make trouble */
        page_mapcount_reset(page); /* remove PageBuddy */
        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}

static inline unsigned int order_to_pindex(int migratetype, int order)
{
        int base = order;

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        if (order > PAGE_ALLOC_COSTLY_ORDER) {
                VM_BUG_ON(order != pageblock_order);
                base = PAGE_ALLOC_COSTLY_ORDER + 1;
        }
#else
        VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
#endif

        return (MIGRATE_PCPTYPES * base) + migratetype;
}

static inline int pindex_to_order(unsigned int pindex)
{
        int order = pindex / MIGRATE_PCPTYPES;

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        if (order > PAGE_ALLOC_COSTLY_ORDER)
                order = pageblock_order;
#else
        VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
#endif

        return order;
}

static inline bool pcp_allowed_order(unsigned int order)
{
        if (order <= PAGE_ALLOC_COSTLY_ORDER)
                return true;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        if (order == pageblock_order)
                return true;
#endif
        return false;
}

static inline void free_the_page(struct page *page, unsigned int order)
{
        if (pcp_allowed_order(order))           /* Via pcp? */
                free_unref_page(page, order);
        else
                __free_pages_ok(page, order, FPI_NONE);
}

/*
 * Higher-order pages are called "compound pages".  They are structured thusly:
 *
 * The first PAGE_SIZE page is called the "head page" and have PG_head set.
 *
 * The remaining PAGE_SIZE pages are called "tail pages". PageTail() is encoded
 * in bit 0 of page->compound_head. The rest of bits is pointer to head page.
 *
 * The first tail page's ->compound_dtor holds the offset in array of compound
 * page destructors. See compound_page_dtors.
 *
 * The first tail page's ->compound_order holds the order of allocation.
 * This usage means that zero-order pages may not be compound.
 */

void free_compound_page(struct page *page)
{
        mem_cgroup_uncharge(page_folio(page));
        free_the_page(page, compound_order(page));
}

void prep_compound_page(struct page *page, unsigned int order)
{
        int i;
        int nr_pages = 1 << order;

        __SetPageHead(page);
        for (i = 1; i < nr_pages; i++) {
                struct page *p = page + i;
                p->mapping = TAIL_MAPPING;
                set_compound_head(p, page);
        }

        set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
        set_compound_order(page, order);
        atomic_set(compound_mapcount_ptr(page), -1);
        if (hpage_pincount_available(page))
                atomic_set(compound_pincount_ptr(page), 0);
}

#ifdef CONFIG_DEBUG_PAGEALLOC
unsigned int _debug_guardpage_minorder;

bool _debug_pagealloc_enabled_early __read_mostly
                        = IS_ENABLED(CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT);
EXPORT_SYMBOL(_debug_pagealloc_enabled_early);
DEFINE_STATIC_KEY_FALSE(_debug_pagealloc_enabled);
EXPORT_SYMBOL(_debug_pagealloc_enabled);

DEFINE_STATIC_KEY_FALSE(_debug_guardpage_enabled);

static int __init early_debug_pagealloc(char *buf)
{
        return kstrtobool(buf, &_debug_pagealloc_enabled_early);
}
early_param("debug_pagealloc", early_debug_pagealloc);

static int __init debug_guardpage_minorder_setup(char *buf)
{
        unsigned long res;

        if (kstrtoul(buf, 10, &res) < 0 ||  res > MAX_ORDER / 2) {
                pr_err("Bad debug_guardpage_minorder value\n");
                return 0;
        }
        _debug_guardpage_minorder = res;
        pr_info("Setting debug_guardpage_minorder to %lu\n", res);
        return 0;
}
early_param("debug_guardpage_minorder", debug_guardpage_minorder_setup);

static inline bool set_page_guard(struct zone *zone, struct page *page,
                                unsigned int order, int migratetype)
{
        if (!debug_guardpage_enabled())
                return false;

        if (order >= debug_guardpage_minorder())
                return false;

        __SetPageGuard(page);
        INIT_LIST_HEAD(&page->lru);
        set_page_private(page, order);
        /* Guard pages are not available for any usage */
        __mod_zone_freepage_state(zone, -(1 << order), migratetype);

        return true;
}

static inline void clear_page_guard(struct zone *zone, struct page *page,
                                unsigned int order, int migratetype)
{
        if (!debug_guardpage_enabled())
                return;

        __ClearPageGuard(page);

        set_page_private(page, 0);
        if (!is_migrate_isolate(migratetype))
                __mod_zone_freepage_state(zone, (1 << order), migratetype);
}
#else
static inline bool set_page_guard(struct zone *zone, struct page *page,
                        unsigned int order, int migratetype) { return false; }
static inline void clear_page_guard(struct zone *zone, struct page *page,
                                unsigned int order, int migratetype) {}
#endif

/*
 * Enable static keys related to various memory debugging and hardening options.
 * Some override others, and depend on early params that are evaluated in the
 * order of appearance. So we need to first gather the full picture of what was
 * enabled, and then make decisions.
 */
void init_mem_debugging_and_hardening(void)
{
        bool page_poisoning_requested = false;

#ifdef CONFIG_PAGE_POISONING
        /*
         * Page poisoning is debug page alloc for some arches. If
         * either of those options are enabled, enable poisoning.
         */
        if (page_poisoning_enabled() ||
             (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
              debug_pagealloc_enabled())) {
                static_branch_enable(&_page_poisoning_enabled);
                page_poisoning_requested = true;
        }
#endif

        if ((_init_on_alloc_enabled_early || _init_on_free_enabled_early) &&
            page_poisoning_requested) {
                pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
                        "will take precedence over init_on_alloc and init_on_free\n");
                _init_on_alloc_enabled_early = false;
                _init_on_free_enabled_early = false;
        }

        if (_init_on_alloc_enabled_early)
                static_branch_enable(&init_on_alloc);
        else
                static_branch_disable(&init_on_alloc);

        if (_init_on_free_enabled_early)
                static_branch_enable(&init_on_free);
        else
                static_branch_disable(&init_on_free);

#ifdef CONFIG_DEBUG_PAGEALLOC
        if (!debug_pagealloc_enabled())
                return;

        static_branch_enable(&_debug_pagealloc_enabled);

        if (!debug_guardpage_minorder())
                return;

        static_branch_enable(&_debug_guardpage_enabled);
#endif
}

static inline void set_buddy_order(struct page *page, unsigned int order)
{
        set_page_private(page, order);
        __SetPageBuddy(page);
}

/*
 * This function checks whether a page is free && is the buddy
 * we can coalesce a page and its buddy if
 * (a) the buddy is not in a hole (check before calling!) &&
 * (b) the buddy is in the buddy system &&
 * (c) a page and its buddy have the same order &&
 * (d) a page and its buddy are in the same zone.
 *
 * For recording whether a page is in the buddy system, we set PageBuddy.
 * Setting, clearing, and testing PageBuddy is serialized by zone->lock.
 *
 * For recording page's order, we use page_private(page).
 */
static inline bool page_is_buddy(struct page *page, struct page *buddy,
                                                        unsigned int order)
{
        if (!page_is_guard(buddy) && !PageBuddy(buddy))
                return false;

        if (buddy_order(buddy) != order)
                return false;

        /*
         * zone check is done late to avoid uselessly calculating
         * zone/node ids for pages that could never merge.
         */
        if (page_zone_id(page) != page_zone_id(buddy))
                return false;

        VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);

        return true;
}

#ifdef CONFIG_COMPACTION
static inline struct capture_control *task_capc(struct zone *zone)
{
        struct capture_control *capc = current->capture_control;

        return unlikely(capc) &&
                !(current->flags & PF_KTHREAD) &&
                !capc->page &&
                capc->cc->zone == zone ? capc : NULL;
}

static inline bool
compaction_capture(struct capture_control *capc, struct page *page,
                   int order, int migratetype)
{
        if (!capc || order != capc->cc->order)
                return false;

        /* Do not accidentally pollute CMA or isolated regions*/
        if (is_migrate_cma(migratetype) ||
            is_migrate_isolate(migratetype))
                return false;

        /*
         * Do not let lower order allocations pollute a movable pageblock.
         * This might let an unmovable request use a reclaimable pageblock
         * and vice-versa but no more than normal fallback logic which can
         * have trouble finding a high-order free page.
         */
        if (order < pageblock_order && migratetype == MIGRATE_MOVABLE)
                return false;

        capc->page = page;
        return true;
}

#else
static inline struct capture_control *task_capc(struct zone *zone)
{
        return NULL;
}

static inline bool
compaction_capture(struct capture_control *capc, struct page *page,
                   int order, int migratetype)
{
        return false;
}
#endif /* CONFIG_COMPACTION */

/* Used for pages not on another list */
static inline void add_to_free_list(struct page *page, struct zone *zone,
                                    unsigned int order, int migratetype)
{
        struct free_area *area = &zone->free_area[order];

        list_add(&page->lru, &area->free_list[migratetype]);
        area->nr_free++;
}

/* Used for pages not on another list */
static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
                                         unsigned int order, int migratetype)
{
        struct free_area *area = &zone->free_area[order];

        list_add_tail(&page->lru, &area->free_list[migratetype]);
        area->nr_free++;
}

/*
 * Used for pages which are on another list. Move the pages to the tail
 * of the list - so the moved pages won't immediately be considered for
 * allocation again (e.g., optimization for memory onlining).
 */
static inline void move_to_free_list(struct page *page, struct zone *zone,
                                     unsigned int order, int migratetype)
{
        struct free_area *area = &zone->free_area[order];

        list_move_tail(&page->lru, &area->free_list[migratetype]);
}

static inline void del_page_from_free_list(struct page *page, struct zone *zone,
                                           unsigned int order)
{
        /* clear reported state and update reported page count */
        if (page_reported(page))
                __ClearPageReported(page);

        list_del(&page->lru);
        __ClearPageBuddy(page);
        set_page_private(page, 0);
        zone->free_area[order].nr_free--;
}

/*
 * If this is not the largest possible page, check if the buddy
 * of the next-highest order is free. If it is, it's possible
 * that pages are being freed that will coalesce soon. In case,
 * that is happening, add the free page to the tail of the list
 * so it's less likely to be used soon and more likely to be merged
 * as a higher order page
 */
static inline bool
buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
                   struct page *page, unsigned int order)
{
        struct page *higher_page, *higher_buddy;
        unsigned long combined_pfn;

        if (order >= MAX_ORDER - 2)
                return false;

        combined_pfn = buddy_pfn & pfn;
        higher_page = page + (combined_pfn - pfn);
        buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1);
        higher_buddy = higher_page + (buddy_pfn - combined_pfn);

        return page_is_buddy(higher_page, higher_buddy, order + 1);
}

/*
 * Freeing function for a buddy system allocator.
 *
 * The concept of a buddy system is to maintain direct-mapped table
 * (containing bit values) for memory blocks of various "orders".
 * The bottom level table contains the map for the smallest allocatable
 * units of memory (here, pages), and each level above it describes
 * pairs of units from the levels below, hence, "buddies".
 * At a high level, all that happens here is marking the table entry
 * at the bottom level available, and propagating the changes upward
 * as necessary, plus some accounting needed to play nicely with other
 * parts of the VM system.
 * At each level, we keep a list of pages, which are heads of continuous
 * free pages of length of (1 << order) and marked with PageBuddy.
 * Page's order is recorded in page_private(page) field.
 * So when we are allocating or freeing one, we can derive the state of the
 * other.  That is, if we allocate a small block, and both were
 * free, the remainder of the region must be split into blocks.
 * If a block is freed, and its buddy is also free, then this
 * triggers coalescing into a block of larger size.
 *
 * -- nyc
 */

static inline void __free_one_page(struct page *page,
                unsigned long pfn,
                struct zone *zone, unsigned int order,
                int migratetype, fpi_t fpi_flags)
{
        struct capture_control *capc = task_capc(zone);
        unsigned long buddy_pfn;
        unsigned long combined_pfn;
        unsigned int max_order;
        struct page *buddy;
        bool to_tail;

        max_order = min_t(unsigned int, MAX_ORDER - 1, pageblock_order);

        VM_BUG_ON(!zone_is_initialized(zone));
        VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);

        VM_BUG_ON(migratetype == -1);
        if (likely(!is_migrate_isolate(migratetype)))
                __mod_zone_freepage_state(zone, 1 << order, migratetype);

        VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
        VM_BUG_ON_PAGE(bad_range(zone, page), page);

continue_merging:
        while (order < max_order) {
                if (compaction_capture(capc, page, order, migratetype)) {
                        __mod_zone_freepage_state(zone, -(1 << order),
                                                                migratetype);
                        return;
                }
                buddy_pfn = __find_buddy_pfn(pfn, order);
                buddy = page + (buddy_pfn - pfn);

                if (!page_is_buddy(page, buddy, order))
                        goto done_merging;
                /*
                 * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
                 * merge with it and move up one order.
                 */
                if (page_is_guard(buddy))
                        clear_page_guard(zone, buddy, order, migratetype);
                else
                        del_page_from_free_list(buddy, zone, order);
                combined_pfn = buddy_pfn & pfn;
                page = page + (combined_pfn - pfn);
                pfn = combined_pfn;
                order++;
        }
        if (order < MAX_ORDER - 1) {
                /* If we are here, it means order is >= pageblock_order.
                 * We want to prevent merge between freepages on isolate
                 * pageblock and normal pageblock. Without this, pageblock
                 * isolation could cause incorrect freepage or CMA accounting.
                 *
                 * We don't want to hit this code for the more frequent
                 * low-order merging.
                 */
                if (unlikely(has_isolate_pageblock(zone))) {
                        int buddy_mt;

                        buddy_pfn = __find_buddy_pfn(pfn, order);
                        buddy = page + (buddy_pfn - pfn);
                        buddy_mt = get_pageblock_migratetype(buddy);

                        if (migratetype != buddy_mt
                                        && (is_migrate_isolate(migratetype) ||
                                                is_migrate_isolate(buddy_mt)))
                                goto done_merging;
                }
                max_order = order + 1;
                goto continue_merging;
        }

done_merging:
        set_buddy_order(page, order);

        if (fpi_flags & FPI_TO_TAIL)
                to_tail = true;
        else if (is_shuffle_order(order))
                to_tail = shuffle_pick_tail();
        else
                to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order);

        if (to_tail)
                add_to_free_list_tail(page, zone, order, migratetype);
        else
                add_to_free_list(page, zone, order, migratetype);

        /* Notify page reporting subsystem of freed page */
        if (!(fpi_flags & FPI_SKIP_REPORT_NOTIFY))
                page_reporting_notify_free(order);
}

/*
 * A bad page could be due to a number of fields. Instead of multiple branches,
 * try and check multiple fields with one check. The caller must do a detailed
 * check if necessary.
 */
static inline bool page_expected_state(struct page *page,
                                        unsigned long check_flags)
{
        if (unlikely(atomic_read(&page->_mapcount) != -1))
                return false;

        if (unlikely((unsigned long)page->mapping |
                        page_ref_count(page) |
#ifdef CONFIG_MEMCG
                        page->memcg_data |
#endif
                        (page->flags & check_flags)))
                return false;

        return true;
}

static const char *page_bad_reason(struct page *page, unsigned long flags)
{
        const char *bad_reason = NULL;

        if (unlikely(atomic_read(&page->_mapcount) != -1))
                bad_reason = "nonzero mapcount";
        if (unlikely(page->mapping != NULL))
                bad_reason = "non-NULL mapping";
        if (unlikely(page_ref_count(page) != 0))
                bad_reason = "nonzero _refcount";
        if (unlikely(page->flags & flags)) {
                if (flags == PAGE_FLAGS_CHECK_AT_PREP)
                        bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag(s) set";
                else
                        bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
        }
#ifdef CONFIG_MEMCG
        if (unlikely(page->memcg_data))
                bad_reason = "page still charged to cgroup";
#endif
        return bad_reason;
}

static void check_free_page_bad(struct page *page)
{
        bad_page(page,
                 page_bad_reason(page, PAGE_FLAGS_CHECK_AT_FREE));
}

static inline int check_free_page(struct page *page)
{
        if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
                return 0;

        /* Something has gone sideways, find it */
        check_free_page_bad(page);
        return 1;
}

static int free_tail_pages_check(struct page *head_page, struct page *page)
{
        int ret = 1;

        /*
         * We rely page->lru.next never has bit 0 set, unless the page
         * is PageTail(). Let's make sure that's true even for poisoned ->lru.
         */
        BUILD_BUG_ON((unsigned long)LIST_POISON1 & 1);

        if (!IS_ENABLED(CONFIG_DEBUG_VM)) {
                ret = 0;
                goto out;
        }
        switch (page - head_page) {
        case 1:
                /* the first tail page: ->mapping may be compound_mapcount() */
                if (unlikely(compound_mapcount(page))) {
                        bad_page(page, "nonzero compound_mapcount");
                        goto out;
                }
                break;
        case 2:
                /*
                 * the second tail page: ->mapping is
                 * deferred_list.next -- ignore value.
                 */
                break;
        default:
                if (page->mapping != TAIL_MAPPING) {
                        bad_page(page, "corrupted mapping in tail page");
                        goto out;
                }
                break;
        }
        if (unlikely(!PageTail(page))) {
                bad_page(page, "PageTail not set");
                goto out;
        }
        if (unlikely(compound_head(page) != head_page)) {
                bad_page(page, "compound_head not consistent");
                goto out;
        }
        ret = 0;
out:
        page->mapping = NULL;
        clear_compound_head(page);
        return ret;
}

static void kernel_init_free_pages(struct page *page, int numpages, bool zero_tags)
{
        int i;

        if (zero_tags) {
                for (i = 0; i < numpages; i++)
                        tag_clear_highpage(page + i);
                return;
        }

        /* s390's use of memset() could override KASAN redzones. */
        kasan_disable_current();
        for (i = 0; i < numpages; i++) {
                u8 tag = page_kasan_tag(page + i);
                page_kasan_tag_reset(page + i);
                clear_highpage(page + i);
                page_kasan_tag_set(page + i, tag);
        }
        kasan_enable_current();
}

static __always_inline bool free_pages_prepare(struct page *page,
                        unsigned int order, bool check_free, fpi_t fpi_flags)
{
        int bad = 0;
        bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags);

        VM_BUG_ON_PAGE(PageTail(page), page);

        trace_mm_page_free(page, order);

        if (unlikely(PageHWPoison(page)) && !order) {
                /*
                 * Do not let hwpoison pages hit pcplists/buddy
                 * Untie memcg state and reset page's owner
                 */
                if (memcg_kmem_enabled() && PageMemcgKmem(page))
                        __memcg_kmem_uncharge_page(page, order);
                reset_page_owner(page, order);
                return false;
        }

        /*
         * Check tail pages before head page information is cleared to
         * avoid checking PageCompound for order-0 pages.
         */
        if (unlikely(order)) {
                bool compound = PageCompound(page);
                int i;

                VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);

                if (compound) {
                        ClearPageDoubleMap(page);
                        ClearPageHasHWPoisoned(page);
                }
                for (i = 1; i < (1 << order); i++) {
                        if (compound)
                                bad += free_tail_pages_check(page, page + i);
                        if (unlikely(check_free_page(page + i))) {
                                bad++;
                                continue;
                        }
                        (page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
                }
        }
        if (PageMappingFlags(page))
                page->mapping = NULL;
        if (memcg_kmem_enabled() && PageMemcgKmem(page))
                __memcg_kmem_uncharge_page(page, order);
        if (check_free)
                bad += check_free_page(page);
        if (bad)
                return false;

        page_cpupid_reset_last(page);
        page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
        reset_page_owner(page, order);

        if (!PageHighMem(page)) {
                debug_check_no_locks_freed(page_address(page),
                                           PAGE_SIZE << order);
                debug_check_no_obj_freed(page_address(page),
                                           PAGE_SIZE << order);
        }

        kernel_poison_pages(page, 1 << order);

        /*
         * As memory initialization might be integrated into KASAN,
         * kasan_free_pages and kernel_init_free_pages must be
         * kept together to avoid discrepancies in behavior.
         *
         * With hardware tag-based KASAN, memory tags must be set before the
         * page becomes unavailable via debug_pagealloc or arch_free_page.
         */
        if (kasan_has_integrated_init()) {
                if (!skip_kasan_poison)
                        kasan_free_pages(page, order);
        } else {
                bool init = want_init_on_free();

                if (init)
                        kernel_init_free_pages(page, 1 << order, false);
                if (!skip_kasan_poison)
                        kasan_poison_pages(page, order, init);
        }

        /*
         * arch_free_page() can make the page's contents inaccessible.  s390
         * does this.  So nothing which can access the page's contents should
         * happen after this.
         */
        arch_free_page(page, order);

        debug_pagealloc_unmap_pages(page, 1 << order);

        return true;
}

#ifdef CONFIG_DEBUG_VM
/*
 * With DEBUG_VM enabled, order-0 pages are checked immediately when being freed
 * to pcp lists. With debug_pagealloc also enabled, they are also rechecked when
 * moved from pcp lists to free lists.
 */
static bool free_pcp_prepare(struct page *page, unsigned int order)
{
        return free_pages_prepare(page, order, true, FPI_NONE);
}

static bool bulkfree_pcp_prepare(struct page *page)
{
        if (debug_pagealloc_enabled_static())
                return check_free_page(page);
        else
                return false;
}
#else
/*
 * With DEBUG_VM disabled, order-0 pages being freed are checked only when
 * moving from pcp lists to free list in order to reduce overhead. With
 * debug_pagealloc enabled, they are checked also immediately when being freed
 * to the pcp lists.
 */
static bool free_pcp_prepare(struct page *page, unsigned int order)
{
        if (debug_pagealloc_enabled_static())
                return free_pages_prepare(page, order, true, FPI_NONE);
        else
                return free_pages_prepare(page, order, false, FPI_NONE);
}

static bool bulkfree_pcp_prepare(struct page *page)
{
        return check_free_page(page);
}
#endif /* CONFIG_DEBUG_VM */

static inline void prefetch_buddy(struct page *page)
{
        unsigned long pfn = page_to_pfn(page);
        unsigned long buddy_pfn = __find_buddy_pfn(pfn, 0);
        struct page *buddy = page + (buddy_pfn - pfn);

        prefetch(buddy);
}

/*
 * Frees a number of pages from the PCP lists
 * Assumes all pages on list are in same zone.
 * count is the number of pages to free.
 */
static void free_pcppages_bulk(struct zone *zone, int count,
                                        struct per_cpu_pages *pcp)
{
        int pindex = 0;
        int batch_free = 0;
        int nr_freed = 0;
        unsigned int order;
        int prefetch_nr = READ_ONCE(pcp->batch);
        bool isolated_pageblocks;
        struct page *page, *tmp;
        LIST_HEAD(head);

        /*
         * Ensure proper count is passed which otherwise would stuck in the
         * below while (list_empty(list)) loop.
         */
        count = min(pcp->count, count);
        while (count > 0) {
                struct list_head *list;

                /*
                 * Remove pages from lists in a round-robin fashion. A
                 * batch_free count is maintained that is incremented when an
                 * empty list is encountered.  This is so more pages are freed
                 * off fuller lists instead of spinning excessively around empty
                 * lists
                 */
                do {
                        batch_free++;
                        if (++pindex == NR_PCP_LISTS)
                                pindex = 0;
                        list = &pcp->lists[pindex];
                } while (list_empty(list));

                /* This is the only non-empty list. Free them all. */
                if (batch_free == NR_PCP_LISTS)
                        batch_free = count;

                order = pindex_to_order(pindex);
                BUILD_BUG_ON(MAX_ORDER >= (1<<NR_PCP_ORDER_WIDTH));
                do {
                        page = list_last_entry(list, struct page, lru);
                        /* must delete to avoid corrupting pcp list */
                        list_del(&page->lru);
                        nr_freed += 1 << order;
                        count -= 1 << order;

                        if (bulkfree_pcp_prepare(page))
                                continue;

                        /* Encode order with the migratetype */
                        page->index <<= NR_PCP_ORDER_WIDTH;
                        page->index |= order;

                        list_add_tail(&page->lru, &head);

                        /*
                         * We are going to put the page back to the global
                         * pool, prefetch its buddy to speed up later access
                         * under zone->lock. It is believed the overhead of
                         * an additional test and calculating buddy_pfn here
                         * can be offset by reduced memory latency later. To
                         * avoid excessive prefetching due to large count, only
                         * prefetch buddy for the first pcp->batch nr of pages.
                         */
                        if (prefetch_nr) {
                                prefetch_buddy(page);
                                prefetch_nr--;
                        }
                } while (count > 0 && --batch_free && !list_empty(list));
        }
        pcp->count -= nr_freed;

        /*
         * local_lock_irq held so equivalent to spin_lock_irqsave for
         * both PREEMPT_RT and non-PREEMPT_RT configurations.
         */
        spin_lock(&zone->lock);
        isolated_pageblocks = has_isolate_pageblock(zone);

        /*
         * Use safe version since after __free_one_page(),
         * page->lru.next will not point to original list.
         */
        list_for_each_entry_safe(page, tmp, &head, lru) {
                int mt = get_pcppage_migratetype(page);

                /* mt has been encoded with the order (see above) */
                order = mt & NR_PCP_ORDER_MASK;
                mt >>= NR_PCP_ORDER_WIDTH;

                /* MIGRATE_ISOLATE page should not go to pcplists */
                VM_BUG_ON_PAGE(is_migrate_isolate(mt), page);
                /* Pageblock could have been isolated meanwhile */
                if (unlikely(isolated_pageblocks))
                        mt = get_pageblock_migratetype(page);

                __free_one_page(page, page_to_pfn(page), zone, order, mt, FPI_NONE);
                trace_mm_page_pcpu_drain(page, order, mt);
        }
        spin_unlock(&zone->lock);
}

static void free_one_page(struct zone *zone,
                                struct page *page, unsigned long pfn,
                                unsigned int order,
                                int migratetype, fpi_t fpi_flags)
{
        unsigned long flags;

        spin_lock_irqsave(&zone->lock, flags);
        if (unlikely(has_isolate_pageblock(zone) ||
                is_migrate_isolate(migratetype))) {
                migratetype = get_pfnblock_migratetype(page, pfn);
        }
        __free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
        spin_unlock_irqrestore(&zone->lock, flags);
}

static void __meminit __init_single_page(struct page *page, unsigned long pfn,
                                unsigned long zone, int nid)
{
        mm_zero_struct_page(page);
        set_page_links(page, zone, nid, pfn);
        init_page_count(page);
        page_mapcount_reset(page);
        page_cpupid_reset_last(page);
        page_kasan_tag_reset(page);

        INIT_LIST_HEAD(&page->lru);
#ifdef WANT_PAGE_VIRTUAL
        /* The shift won't overflow because ZONE_NORMAL is below 4G. */
        if (!is_highmem_idx(zone))
                set_page_address(page, __va(pfn << PAGE_SHIFT));
#endif
}

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
static void __meminit init_reserved_page(unsigned long pfn)
{
        pg_data_t *pgdat;
        int nid, zid;

        if (!early_page_uninitialised(pfn))
                return;

        nid = early_pfn_to_nid(pfn);
        pgdat = NODE_DATA(nid);

        for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                struct zone *zone = &pgdat->node_zones[zid];

                if (zone_spans_pfn(zone, pfn))
                        break;
        }
        __init_single_page(pfn_to_page(pfn), pfn, zid, nid);
}
#else
static inline void init_reserved_page(unsigned long pfn)
{
}
#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */

/*
 * Initialised pages do not have PageReserved set. This function is
 * called for each range allocated by the bootmem allocator and
 * marks the pages PageReserved. The remaining valid pages are later
 * sent to the buddy page allocator.
 */
void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
{
        unsigned long start_pfn = PFN_DOWN(start);
        unsigned long end_pfn = PFN_UP(end);

        for (; start_pfn < end_pfn; start_pfn++) {
                if (pfn_valid(start_pfn)) {
                        struct page *page = pfn_to_page(start_pfn);

                        init_reserved_page(start_pfn);

                        /* Avoid false-positive PageTail() */
                        INIT_LIST_HEAD(&page->lru);

                        /*
                         * no need for atomic set_bit because the struct
                         * page is not visible yet so nobody should
                         * access it yet.
                         */
                        __SetPageReserved(page);
                }
        }
}

static void __free_pages_ok(struct page *page, unsigned int order,
                            fpi_t fpi_flags)
{
        unsigned long flags;
        int migratetype;
        unsigned long pfn = page_to_pfn(page);
        struct zone *zone = page_zone(page);

        if (!free_pages_prepare(page, order, true, fpi_flags))
                return;

        migratetype = get_pfnblock_migratetype(page, pfn);

        spin_lock_irqsave(&zone->lock, flags);
        if (unlikely(has_isolate_pageblock(zone) ||
                is_migrate_isolate(migratetype))) {
                migratetype = get_pfnblock_migratetype(page, pfn);
        }
        __free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
        spin_unlock_irqrestore(&zone->lock, flags);

        __count_vm_events(PGFREE, 1 << order);
}

void __free_pages_core(struct page *page, unsigned int order)
{
        unsigned int nr_pages = 1 << order;
        struct page *p = page;
        unsigned int loop;

        /*
         * When initializing the memmap, __init_single_page() sets the refcount
         * of all pages to 1 ("allocated"/"not free"). We have to set the
         * refcount of all involved pages to 0.
         */
        prefetchw(p);
        for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
                prefetchw(p + 1);
                __ClearPageReserved(p);
                set_page_count(p, 0);
        }
        __ClearPageReserved(p);
        set_page_count(p, 0);

        atomic_long_add(nr_pages, &page_zone(page)->managed_pages);

        /*
         * Bypass PCP and place fresh pages right to the tail, primarily
         * relevant for memory onlining.
         */
        __free_pages_ok(page, order, FPI_TO_TAIL | FPI_SKIP_KASAN_POISON);
}

#ifdef CONFIG_NUMA

/*
 * During memory init memblocks map pfns to nids. The search is expensive and
 * this caches recent lookups. The implementation of __early_pfn_to_nid
 * treats start/end as pfns.
 */
struct mminit_pfnnid_cache {
        unsigned long last_start;
        unsigned long last_end;
        int last_nid;
};

static struct mminit_pfnnid_cache early_pfnnid_cache __meminitdata;

/*
 * Required by SPARSEMEM. Given a PFN, return what node the PFN is on.
 */
static int __meminit __early_pfn_to_nid(unsigned long pfn,
                                        struct mminit_pfnnid_cache *state)
{
        unsigned long start_pfn, end_pfn;
        int nid;

        if (state->last_start <= pfn && pfn < state->last_end)
                return state->last_nid;

        nid = memblock_search_pfn_nid(pfn, &start_pfn, &end_pfn);
        if (nid != NUMA_NO_NODE) {
                state->last_start = start_pfn;
                state->last_end = end_pfn;
                state->last_nid = nid;
        }

        return nid;
}

int __meminit early_pfn_to_nid(unsigned long pfn)
{
        static DEFINE_SPINLOCK(early_pfn_lock);
        int nid;

        spin_lock(&early_pfn_lock);
        nid = __early_pfn_to_nid(pfn, &early_pfnnid_cache);
        if (nid < 0)
                nid = first_online_node;
        spin_unlock(&early_pfn_lock);

        return nid;
}
#endif /* CONFIG_NUMA */

void __init memblock_free_pages(struct page *page, unsigned long pfn,
                                                        unsigned int order)
{
        if (early_page_uninitialised(pfn))
                return;
        __free_pages_core(page, order);
}

/*
 * Check that the whole (or subset of) a pageblock given by the interval of
 * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
 * with the migration of free compaction scanner.
 *
 * Return struct page pointer of start_pfn, or NULL if checks were not passed.
 *
 * It's possible on some configurations to have a setup like node0 node1 node0
 * i.e. it's possible that all pages within a zones range of pages do not
 * belong to a single zone. We assume that a border between node0 and node1
 * can occur within a single pageblock, but not a node0 node1 node0
 * interleaving within a single pageblock. It is therefore sufficient to check
 * the first and last page of a pageblock and avoid checking each individual
 * page in a pageblock.
 */
struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
                                     unsigned long end_pfn, struct zone *zone)
{
        struct page *start_page;
        struct page *end_page;

        /* end_pfn is one past the range we are checking */
        end_pfn--;

        if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
                return NULL;

        start_page = pfn_to_online_page(start_pfn);
        if (!start_page)
                return NULL;

        if (page_zone(start_page) != zone)
                return NULL;

        end_page = pfn_to_page(end_pfn);

        /* This gives a shorter code than deriving page_zone(end_page) */
        if (page_zone_id(start_page) != page_zone_id(end_page))
                return NULL;

        return start_page;
}

void set_zone_contiguous(struct zone *zone)
{
        unsigned long block_start_pfn = zone->zone_start_pfn;
        unsigned long block_end_pfn;

        block_end_pfn = ALIGN(block_start_pfn + 1, pageblock_nr_pages);
        for (; block_start_pfn < zone_end_pfn(zone);
                        block_start_pfn = block_end_pfn,
                         block_end_pfn += pageblock_nr_pages) {

                block_end_pfn = min(block_end_pfn, zone_end_pfn(zone));

                if (!__pageblock_pfn_to_page(block_start_pfn,
                                             block_end_pfn, zone))
                        return;
                cond_resched();
        }

        /* We confirm that there is no hole */
        zone->contiguous = true;
}

void clear_zone_contiguous(struct zone *zone)
{
        zone->contiguous = false;
}

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
static void __init deferred_free_range(unsigned long pfn,
                                       unsigned long nr_pages)
{
        struct page *page;
        unsigned long i;

        if (!nr_pages)
                return;

        page = pfn_to_page(pfn);

        /* Free a large naturally-aligned chunk if possible */
        if (nr_pages == pageblock_nr_pages &&
            (pfn & (pageblock_nr_pages - 1)) == 0) {
                set_pageblock_migratetype(page, MIGRATE_MOVABLE);
                __free_pages_core(page, pageblock_order);
                return;
        }

        for (i = 0; i < nr_pages; i++, page++, pfn++) {
                if ((pfn & (pageblock_nr_pages - 1)) == 0)
                        set_pageblock_migratetype(page, MIGRATE_MOVABLE);
                __free_pages_core(page, 0);
        }
}

/* Completion tracking for deferred_init_memmap() threads */
static atomic_t pgdat_init_n_undone __initdata;
static __initdata DECLARE_COMPLETION(pgdat_init_all_done_comp);

static inline void __init pgdat_init_report_one_done(void)
{
        if (atomic_dec_and_test(&pgdat_init_n_undone))
                complete(&pgdat_init_all_done_comp);
}

/*
 * Returns true if page needs to be initialized or freed to buddy allocator.
 *
 * First we check if pfn is valid on architectures where it is possible to have
 * holes within pageblock_nr_pages. On systems where it is not possible, this
 * function is optimized out.
 *
 * Then, we check if a current large page is valid by only checking the validity
 * of the head pfn.
 */
static inline bool __init deferred_pfn_valid(unsigned long pfn)
{
        if (!(pfn & (pageblock_nr_pages - 1)) && !pfn_valid(pfn))
                return false;
        return true;
}

/*
 * Free pages to buddy allocator. Try to free aligned pages in
 * pageblock_nr_pages sizes.
 */
static void __init deferred_free_pages(unsigned long pfn,
                                       unsigned long end_pfn)
{
        unsigned long nr_pgmask = pageblock_nr_pages - 1;
        unsigned long nr_free = 0;

        for (; pfn < end_pfn; pfn++) {
                if (!deferred_pfn_valid(pfn)) {
                        deferred_free_range(pfn - nr_free, nr_free);
                        nr_free = 0;
                } else if (!(pfn & nr_pgmask)) {
                        deferred_free_range(pfn - nr_free, nr_free);
                        nr_free = 1;
                } else {
                        nr_free++;
                }
        }
        /* Free the last block of pages to allocator */
        deferred_free_range(pfn - nr_free, nr_free);
}

/*
 * Initialize struct pages.  We minimize pfn page lookups and scheduler checks
 * by performing it only once every pageblock_nr_pages.
 * Return number of pages initialized.
 */
static unsigned long  __init deferred_init_pages(struct zone *zone,
                                                 unsigned long pfn,
                                                 unsigned long end_pfn)
{
        unsigned long nr_pgmask = pageblock_nr_pages - 1;
        int nid = zone_to_nid(zone);
        unsigned long nr_pages = 0;
        int zid = zone_idx(zone);
        struct page *page = NULL;

        for (; pfn < end_pfn; pfn++) {
                if (!deferred_pfn_valid(pfn)) {
                        page = NULL;
                        continue;
                } else if (!page || !(pfn & nr_pgmask)) {
                        page = pfn_to_page(pfn);
                } else {
                        page++;
                }
                __init_single_page(page, pfn, zid, nid);
                nr_pages++;
        }
        return (nr_pages);
}

/*
 * This function is meant to pre-load the iterator for the zone init.
 * Specifically it walks through the ranges until we are caught up to the
 * first_init_pfn value and exits there. If we never encounter the value we
 * return false indicating there are no valid ranges left.
 */
static bool __init
deferred_init_mem_pfn_range_in_zone(u64 *i, struct zone *zone,
                                    unsigned long *spfn, unsigned long *epfn,
                                    unsigned long first_init_pfn)
{
        u64 j;

        /*
         * Start out by walking through the ranges in this zone that have
         * already been initialized. We don't need to do anything with them
         * so we just need to flush them out of the system.
         */
        for_each_free_mem_pfn_range_in_zone(j, zone, spfn, epfn) {
                if (*epfn <= first_init_pfn)
                        continue;
                if (*spfn < first_init_pfn)
                        *spfn = first_init_pfn;
                *i = j;
                return true;
        }

        return false;
}

/*
 * Initialize and free pages. We do it in two loops: first we initialize
 * struct page, then free to buddy allocator, because while we are
 * freeing pages we can access pages that are ahead (computing buddy
 * page in __free_one_page()).
 *
 * In order to try and keep some memory in the cache we have the loop
 * broken along max page order boundaries. This way we will not cause
 * any issues with the buddy page computation.
 */
static unsigned long __init
deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn,
                       unsigned long *end_pfn)
{
        unsigned long mo_pfn = ALIGN(*start_pfn + 1, MAX_ORDER_NR_PAGES);
        unsigned long spfn = *start_pfn, epfn = *end_pfn;
        unsigned long nr_pages = 0;
        u64 j = *i;

        /* First we loop through and initialize the page values */
        for_each_free_mem_pfn_range_in_zone_from(j, zone, start_pfn, end_pfn) {
                unsigned long t;

                if (mo_pfn <= *start_pfn)
                        break;

                t = min(mo_pfn, *end_pfn);
                nr_pages += deferred_init_pages(zone, *start_pfn, t);

                if (mo_pfn < *end_pfn) {
                        *start_pfn = mo_pfn;
                        break;
                }
        }

        /* Reset values and now loop through freeing pages as needed */
        swap(j, *i);

        for_each_free_mem_pfn_range_in_zone_from(j, zone, &spfn, &epfn) {
                unsigned long t;

                if (mo_pfn <= spfn)
                        break;

                t = min(mo_pfn, epfn);
                deferred_free_pages(spfn, t);

                if (mo_pfn <= epfn)
                        break;
        }

        return nr_pages;
}

static void __init
deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
                           void *arg)
{
        unsigned long spfn, epfn;
        struct zone *zone = arg;
        u64 i;

        deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, start_pfn);

        /*
         * Initialize and free pages in MAX_ORDER sized increments so that we
         * can avoid introducing any issues with the buddy allocator.
         */
        while (spfn < end_pfn) {
                deferred_init_maxorder(&i, zone, &spfn, &epfn);
                cond_resched();
        }
}

/* An arch may override for more concurrency. */
__weak int __init
deferred_page_init_max_threads(const struct cpumask *node_cpumask)
{
        return 1;
}

/* Initialise remaining memory on a node */
static int __init deferred_init_memmap(void *data)
{
        pg_data_t *pgdat = data;
        const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
        unsigned long spfn = 0, epfn = 0;
        unsigned long first_init_pfn, flags;
        unsigned long start = jiffies;
        struct zone *zone;
        int zid, max_threads;
        u64 i;

        /* Bind memory initialisation thread to a local node if possible */
        if (!cpumask_empty(cpumask))
                set_cpus_allowed_ptr(current, cpumask);

        pgdat_resize_lock(pgdat, &flags);
        first_init_pfn = pgdat->first_deferred_pfn;
        if (first_init_pfn == ULONG_MAX) {
                pgdat_resize_unlock(pgdat, &flags);
                pgdat_init_report_one_done();
                return 0;
        }

        /* Sanity check boundaries */
        BUG_ON(pgdat->first_deferred_pfn < pgdat->node_start_pfn);
        BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat));
        pgdat->first_deferred_pfn = ULONG_MAX;

        /*
         * Once we unlock here, the zone cannot be grown anymore, thus if an
         * interrupt thread must allocate this early in boot, zone must be
         * pre-grown prior to start of deferred page initialization.
         */
        pgdat_resize_unlock(pgdat, &flags);

        /* Only the highest zone is deferred so find it */
        for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                zone = pgdat->node_zones + zid;
                if (first_init_pfn < zone_end_pfn(zone))
                        break;
        }

        /* If the zone is empty somebody else may have cleared out the zone */
        if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
                                                 first_init_pfn))
                goto zone_empty;

        max_threads = deferred_page_init_max_threads(cpumask);

        while (spfn < epfn) {
                unsigned long epfn_align = ALIGN(epfn, PAGES_PER_SECTION);
                struct padata_mt_job job = {
                        .thread_fn   = deferred_init_memmap_chunk,
                        .fn_arg      = zone,
                        .start       = spfn,
                        .size        = epfn_align - spfn,
                        .align       = PAGES_PER_SECTION,
                        .min_chunk   = PAGES_PER_SECTION,
                        .max_threads = max_threads,
                };

                padata_do_multithreaded(&job);
                deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
                                                    epfn_align);
        }
zone_empty:
        /* Sanity check that the next zone really is unpopulated */
        WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone));

        pr_info("node %d deferred pages initialised in %ums\n",
                pgdat->node_id, jiffies_to_msecs(jiffies - start));

        pgdat_init_report_one_done();
        return 0;
}

/*
 * If this zone has deferred pages, try to grow it by initializing enough
 * deferred pages to satisfy the allocation specified by order, rounded up to
 * the nearest PAGES_PER_SECTION boundary.  So we're adding memory in increments
 * of SECTION_SIZE bytes by initializing struct pages in increments of
 * PAGES_PER_SECTION * sizeof(struct page) bytes.
 *
 * Return true when zone was grown, otherwise return false. We return true even
 * when we grow less than requested, to let the caller decide if there are
 * enough pages to satisfy the allocation.
 *
 * Note: We use noinline because this function is needed only during boot, and
 * it is called from a __ref function _deferred_grow_zone. This way we are
 * making sure that it is not inlined into permanent text section.
 */
static noinline bool __init
deferred_grow_zone(struct zone *zone, unsigned int order)
{
        unsigned long nr_pages_needed = ALIGN(1 << order, PAGES_PER_SECTION);
        pg_data_t *pgdat = zone->zone_pgdat;
        unsigned long first_deferred_pfn = pgdat->first_deferred_pfn;
        unsigned long spfn, epfn, flags;
        unsigned long nr_pages = 0;
        u64 i;

        /* Only the last zone may have deferred pages */
        if (zone_end_pfn(zone) != pgdat_end_pfn(pgdat))
                return false;

        pgdat_resize_lock(pgdat, &flags);

        /*
         * If someone grew this zone while we were waiting for spinlock, return
         * true, as there might be enough pages already.
         */
        if (first_deferred_pfn != pgdat->first_deferred_pfn) {
                pgdat_resize_unlock(pgdat, &flags);
                return true;
        }

        /* If the zone is empty somebody else may have cleared out the zone */
        if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
                                                 first_deferred_pfn)) {
                pgdat->first_deferred_pfn = ULONG_MAX;
                pgdat_resize_unlock(pgdat, &flags);
                /* Retry only once. */
                return first_deferred_pfn != ULONG_MAX;
        }

        /*
         * Initialize and free pages in MAX_ORDER sized increments so
         * that we can avoid introducing any issues with the buddy
         * allocator.
         */
        while (spfn < epfn) {
                /* update our first deferred PFN for this section */
                first_deferred_pfn = spfn;

                nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
                touch_nmi_watchdog();

                /* We should only stop along section boundaries */
                if ((first_deferred_pfn ^ spfn) < PAGES_PER_SECTION)
                        continue;

                /* If our quota has been met we can stop here */
                if (nr_pages >= nr_pages_needed)
                        break;
        }

        pgdat->first_deferred_pfn = spfn;
        pgdat_resize_unlock(pgdat, &flags);

        return nr_pages > 0;
}

/*
 * deferred_grow_zone() is __init, but it is called from
 * get_page_from_freelist() during early boot until deferred_pages permanently
 * disables this call. This is why we have refdata wrapper to avoid warning,
 * and to ensure that the function body gets unloaded.
 */
static bool __ref
_deferred_grow_zone(struct zone *zone, unsigned int order)
{
        return deferred_grow_zone(zone, order);
}

#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */

void __init page_alloc_init_late(void)
{
        struct zone *zone;
        int nid;

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT

        /* There will be num_node_state(N_MEMORY) threads */
        atomic_set(&pgdat_init_n_undone, num_node_state(N_MEMORY));
        for_each_node_state(nid, N_MEMORY) {
                kthread_run(deferred_init_memmap, NODE_DATA(nid), "pgdatinit%d", nid);
        }

        /* Block until all are initialised */
        wait_for_completion(&pgdat_init_all_done_comp);

        /*
         * We initialized the rest of the deferred pages.  Permanently disable
         * on-demand struct page initialization.
         */
        static_branch_disable(&deferred_pages);

        /* Reinit limits that are based on free pages after the kernel is up */
        files_maxfiles_init();
#endif

        buffer_init();

        /* Discard memblock private memory */
        memblock_discard();

        for_each_node_state(nid, N_MEMORY)
                shuffle_free_memory(NODE_DATA(nid));

        for_each_populated_zone(zone)
                set_zone_contiguous(zone);
}

#ifdef CONFIG_CMA
/* Free whole pageblock and set its migration type to MIGRATE_CMA. */
void __init init_cma_reserved_pageblock(struct page *page)
{
        unsigned i = pageblock_nr_pages;
        struct page *p = page;

        do {
                __ClearPageReserved(p);
                set_page_count(p, 0);
        } while (++p, --i);

        set_pageblock_migratetype(page, MIGRATE_CMA);

        if (pageblock_order >= MAX_ORDER) {
                i = pageblock_nr_pages;
                p = page;
                do {
                        set_page_refcounted(p);
                        __free_pages(p, MAX_ORDER - 1);
                        p += MAX_ORDER_NR_PAGES;
                } while (i -= MAX_ORDER_NR_PAGES);
        } else {
                set_page_refcounted(page);
                __free_pages(page, pageblock_order);
        }

        adjust_managed_page_count(page, pageblock_nr_pages);
        page_zone(page)->cma_pages += pageblock_nr_pages;
}
#endif

/*
 * The order of subdivision here is critical for the IO subsystem.
 * Please do not alter this order without good reasons and regression
 * testing. Specifically, as large blocks of memory are subdivided,
 * the order in which smaller blocks are delivered depends on the order
 * they're subdivided in this function. This is the primary factor
 * influencing the order in which pages are delivered to the IO
 * subsystem according to empirical testing, and this is also justified
 * by considering the behavior of a buddy system containing a single
 * large block of memory acted on by a series of small allocations.
 * This behavior is a critical factor in sglist merging's success.
 *
 * -- nyc
 */
static inline void expand(struct zone *zone, struct page *page,
        int low, int high, int migratetype)
{
        unsigned long size = 1 << high;

        while (high > low) {
                high--;
                size >>= 1;
                VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);

                /*
                 * Mark as guard pages (or page), that will allow to
                 * merge back to allocator when buddy will be freed.
                 * Corresponding page table entries will not be touched,
                 * pages will stay not present in virtual address space
                 */
                if (set_page_guard(zone, &page[size], high, migratetype))
                        continue;

                add_to_free_list(&page[size], zone, high, migratetype);
                set_buddy_order(&page[size], high);
        }
}

static void check_new_page_bad(struct page *page)
{
        if (unlikely(page->flags & __PG_HWPOISON)) {
                /* Don't complain about hwpoisoned pages */
                page_mapcount_reset(page); /* remove PageBuddy */
                return;
        }

        bad_page(page,
                 page_bad_reason(page, PAGE_FLAGS_CHECK_AT_PREP));
}

/*
 * This page is about to be returned from the page allocator
 */
static inline int check_new_page(struct page *page)
{
        if (likely(page_expected_state(page,
                                PAGE_FLAGS_CHECK_AT_PREP|__PG_HWPOISON)))
                return 0;

        check_new_page_bad(page);
        return 1;
}

#ifdef CONFIG_DEBUG_VM
/*
 * With DEBUG_VM enabled, order-0 pages are checked for expected state when
 * being allocated from pcp lists. With debug_pagealloc also enabled, they are
 * also checked when pcp lists are refilled from the free lists.
 */
static inline bool check_pcp_refill(struct page *page)
{
        if (debug_pagealloc_enabled_static())
                return check_new_page(page);
        else
                return false;
}

static inline bool check_new_pcp(struct page *page)
{
        return check_new_page(page);
}
#else
/*
 * With DEBUG_VM disabled, free order-0 pages are checked for expected state
 * when pcp lists are being refilled from the free lists. With debug_pagealloc
 * enabled, they are also checked when being allocated from the pcp lists.
 */
static inline bool check_pcp_refill(struct page *page)
{
        return check_new_page(page);
}
static inline bool check_new_pcp(struct page *page)
{
        if (debug_pagealloc_enabled_static())
                return check_new_page(page);
        else
                return false;
}
#endif /* CONFIG_DEBUG_VM */

static bool check_new_pages(struct page *page, unsigned int order)
{
        int i;
        for (i = 0; i < (1 << order); i++) {
                struct page *p = page + i;

                if (unlikely(check_new_page(p)))
                        return true;
        }

        return false;
}

inline void post_alloc_hook(struct page *page, unsigned int order,
                                gfp_t gfp_flags)
{
        set_page_private(page, 0);
        set_page_refcounted(page);

        arch_alloc_page(page, order);
        debug_pagealloc_map_pages(page, 1 << order);

        /*
         * Page unpoisoning must happen before memory initialization.
         * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
         * allocations and the page unpoisoning code will complain.
         */
        kernel_unpoison_pages(page, 1 << order);

        /*
         * As memory initialization might be integrated into KASAN,
         * kasan_alloc_pages and kernel_init_free_pages must be
         * kept together to avoid discrepancies in behavior.
         */
        if (kasan_has_integrated_init()) {
                kasan_alloc_pages(page, order, gfp_flags);
        } else {
                bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags);

                kasan_unpoison_pages(page, order, init);
                if (init)
                        kernel_init_free_pages(page, 1 << order,
                                               gfp_flags & __GFP_ZEROTAGS);
        }

        set_page_owner(page, order, gfp_flags);
}

static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
                                                        unsigned int alloc_flags)
{
        post_alloc_hook(page, order, gfp_flags);

        if (order && (gfp_flags & __GFP_COMP))
                prep_compound_page(page, order);

        /*
         * page is set pfmemalloc when ALLOC_NO_WATERMARKS was necessary to
         * allocate the page. The expectation is that the caller is taking
         * steps that will free more memory. The caller should avoid the page
         * being used for !PFMEMALLOC purposes.
         */
        if (alloc_flags & ALLOC_NO_WATERMARKS)
                set_page_pfmemalloc(page);
        else
                clear_page_pfmemalloc(page);
}

/*
 * Go through the free lists for the given migratetype and remove
 * the smallest available page from the freelists
 */
static __always_inline
struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
                                                int migratetype)
{
        unsigned int current_order;
        struct free_area *area;
        struct page *page;

        /* Find a page of the appropriate size in the preferred list */
        for (current_order = order; current_order < MAX_ORDER; ++current_order) {
                area = &(zone->free_area[current_order]);
                page = get_page_from_free_area(area, migratetype);
                if (!page)
                        continue;
                del_page_from_free_list(page, zone, current_order);
                expand(zone, page, order, current_order, migratetype);
                set_pcppage_migratetype(page, migratetype);
                return page;
        }

        return NULL;
}


/*
 * This array describes the order lists are fallen back to when
 * the free lists for the desirable migrate type are depleted
 */
static int fallbacks[MIGRATE_TYPES][3] = {
        [MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_TYPES },
        [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
        [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_TYPES },
#ifdef CONFIG_CMA
        [MIGRATE_CMA]         = { MIGRATE_TYPES }, /* Never used */
#endif
#ifdef CONFIG_MEMORY_ISOLATION
        [MIGRATE_ISOLATE]     = { MIGRATE_TYPES }, /* Never used */
#endif
};

#ifdef CONFIG_CMA
static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone,
                                        unsigned int order)
{
        return __rmqueue_smallest(zone, order, MIGRATE_CMA);
}
#else
static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
                                        unsigned int order) { return NULL; }
#endif

/*
 * Move the free pages in a range to the freelist tail of the requested type.
 * Note that start_page and end_pages are not aligned on a pageblock
 * boundary. If alignment is required, use move_freepages_block()
 */
static int move_freepages(struct zone *zone,
                          unsigned long start_pfn, unsigned long end_pfn,
                          int migratetype, int *num_movable)
{
        struct page *page;
        unsigned long pfn;
        unsigned int order;
        int pages_moved = 0;

        for (pfn = start_pfn; pfn <= end_pfn;) {
                page = pfn_to_page(pfn);
                if (!PageBuddy(page)) {
                        /*
                         * We assume that pages that could be isolated for
                         * migration are movable. But we don't actually try
                         * isolating, as that would be expensive.
                         */
                        if (num_movable &&
                                        (PageLRU(page) || __PageMovable(page)))
                                (*num_movable)++;
                        pfn++;
                        continue;
                }

                /* Make sure we are not inadvertently changing nodes */
                VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
                VM_BUG_ON_PAGE(page_zone(page) != zone, page);

                order = buddy_order(page);
                move_to_free_list(page, zone, order, migratetype);
                pfn += 1 << order;
                pages_moved += 1 << order;
        }

        return pages_moved;
}

int move_freepages_block(struct zone *zone, struct page *page,
                                int migratetype, int *num_movable)
{
        unsigned long start_pfn, end_pfn, pfn;

        if (num_movable)
                *num_movable = 0;

        pfn = page_to_pfn(page);
        start_pfn = pfn & ~(pageblock_nr_pages - 1);
        end_pfn = start_pfn + pageblock_nr_pages - 1;

        /* Do not cross zone boundaries */
        if (!zone_spans_pfn(zone, start_pfn))
                start_pfn = pfn;
        if (!zone_spans_pfn(zone, end_pfn))
                return 0;

        return move_freepages(zone, start_pfn, end_pfn, migratetype,
                                                                num_movable);
}

static void change_pageblock_range(struct page *pageblock_page,
                                        int start_order, int migratetype)
{
        int nr_pageblocks = 1 << (start_order - pageblock_order);

        while (nr_pageblocks--) {
                set_pageblock_migratetype(pageblock_page, migratetype);
                pageblock_page += pageblock_nr_pages;
        }
}

/*
 * When we are falling back to another migratetype during allocation, try to
 * steal extra free pages from the same pageblocks to satisfy further
 * allocations, instead of polluting multiple pageblocks.
 *
 * If we are stealing a relatively large buddy page, it is likely there will
 * be more free pages in the pageblock, so try to steal them all. For
 * reclaimable and unmovable allocations, we steal regardless of page size,
 * as fragmentation caused by those allocations polluting movable pageblocks
 * is worse than movable allocations stealing from unmovable and reclaimable
 * pageblocks.
 */
static bool can_steal_fallback(unsigned int order, int start_mt)
{
        /*
         * Leaving this order check is intended, although there is
         * relaxed order check in next check. The reason is that
         * we can actually steal whole pageblock if this condition met,
         * but, below check doesn't guarantee it and that is just heuristic
         * so could be changed anytime.
         */
        if (order >= pageblock_order)
                return true;

        if (order >= pageblock_order / 2 ||
                start_mt == MIGRATE_RECLAIMABLE ||
                start_mt == MIGRATE_UNMOVABLE ||
                page_group_by_mobility_disabled)
                return true;

        return false;
}

static inline bool boost_watermark(struct zone *zone)
{
        unsigned long max_boost;

        if (!watermark_boost_factor)
                return false;
        /*
         * Don't bother in zones that are unlikely to produce results.
         * On small machines, including kdump capture kernels running
         * in a small area, boosting the watermark can cause an out of
         * memory situation immediately.
         */
        if ((pageblock_nr_pages * 4) > zone_managed_pages(zone))
                return false;

        max_boost = mult_frac(zone->_watermark[WMARK_HIGH],
                        watermark_boost_factor, 10000);

        /*
         * high watermark may be uninitialised if fragmentation occurs
         * very early in boot so do not boost. We do not fall
         * through and boost by pageblock_nr_pages as failing
         * allocations that early means that reclaim is not going
         * to help and it may even be impossible to reclaim the
         * boosted watermark resulting in a hang.
         */
        if (!max_boost)
                return false;

        max_boost = max(pageblock_nr_pages, max_boost);

        zone->watermark_boost = min(zone->watermark_boost + pageblock_nr_pages,
                max_boost);

        return true;
}

/*
 * This function implements actual steal behaviour. If order is large enough,
 * we can steal whole pageblock. If not, we first move freepages in this
 * pageblock to our migratetype and determine how many already-allocated pages
 * are there in the pageblock with a compatible migratetype. If at least half
 * of pages are free or compatible, we can change migratetype of the pageblock
 * itself, so pages freed in the future will be put on the correct free list.
 */
static void steal_suitable_fallback(struct zone *zone, struct page *page,
                unsigned int alloc_flags, int start_type, bool whole_block)
{
        unsigned int current_order = buddy_order(page);
        int free_pages, movable_pages, alike_pages;
        int old_block_type;

        old_block_type = get_pageblock_migratetype(page);

        /*
         * This can happen due to races and we want to prevent broken
         * highatomic accounting.
         */
        if (is_migrate_highatomic(old_block_type))
                goto single_page;

        /* Take ownership for orders >= pageblock_order */
        if (current_order >= pageblock_order) {
                change_pageblock_range(page, current_order, start_type);
                goto single_page;
        }

        /*
         * Boost watermarks to increase reclaim pressure to reduce the
         * likelihood of future fallbacks. Wake kswapd now as the node
         * may be balanced overall and kswapd will not wake naturally.
         */
        if (boost_watermark(zone) && (alloc_flags & ALLOC_KSWAPD))
                set_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);

        /* We are not allowed to try stealing from the whole block */
        if (!whole_block)
                goto single_page;

        free_pages = move_freepages_block(zone, page, start_type,
                                                &movable_pages);
        /*
         * Determine how many pages are compatible with our allocation.
         * For movable allocation, it's the number of movable pages which
         * we just obtained. For other types it's a bit more tricky.
         */
        if (start_type == MIGRATE_MOVABLE) {
                alike_pages = movable_pages;
        } else {
                /*
                 * If we are falling back a RECLAIMABLE or UNMOVABLE allocation
                 * to MOVABLE pageblock, consider all non-movable pages as
                 * compatible. If it's UNMOVABLE falling back to RECLAIMABLE or
                 * vice versa, be conservative since we can't distinguish the
                 * exact migratetype of non-movable pages.
                 */
                if (old_block_type == MIGRATE_MOVABLE)
                        alike_pages = pageblock_nr_pages
                                                - (free_pages + movable_pages);
                else
                        alike_pages = 0;
        }

        /* moving whole block can fail due to zone boundary conditions */
        if (!free_pages)
                goto single_page;

        /*
         * If a sufficient number of pages in the block are either free or of
         * comparable migratability as our allocation, claim the whole block.
         */
        if (free_pages + alike_pages >= (1 << (pageblock_order-1)) ||
                        page_group_by_mobility_disabled)
                set_pageblock_migratetype(page, start_type);

        return;

single_page:
        move_to_free_list(page, zone, current_order, start_type);
}

/*
 * Check whether there is a suitable fallback freepage with requested order.
 * If only_stealable is true, this function returns fallback_mt only if
 * we can steal other freepages all together. This would help to reduce
 * fragmentation due to mixed migratetype pages in one pageblock.
 */
int find_suitable_fallback(struct free_area *area, unsigned int order,
                        int migratetype, bool only_stealable, bool *can_steal)
{
        int i;
        int fallback_mt;

        if (area->nr_free == 0)
                return -1;

        *can_steal = false;
        for (i = 0;; i++) {
                fallback_mt = fallbacks[migratetype][i];
                if (fallback_mt == MIGRATE_TYPES)
                        break;

                if (free_area_empty(area, fallback_mt))
                        continue;

                if (can_steal_fallback(order, migratetype))
                        *can_steal = true;

                if (!only_stealable)
                        return fallback_mt;

                if (*can_steal)
                        return fallback_mt;
        }

        return -1;
}

/*
 * Reserve a pageblock for exclusive use of high-order atomic allocations if
 * there are no empty page blocks that contain a page with a suitable order
 */
static void reserve_highatomic_pageblock(struct page *page, struct zone *zone,
                                unsigned int alloc_order)
{
        int mt;
        unsigned long max_managed, flags;

        /*
         * Limit the number reserved to 1 pageblock or roughly 1% of a zone.
         * Check is race-prone but harmless.
         */
        max_managed = (zone_managed_pages(zone) / 100) + pageblock_nr_pages;
        if (zone->nr_reserved_highatomic >= max_managed)
                return;

        spin_lock_irqsave(&zone->lock, flags);

        /* Recheck the nr_reserved_highatomic limit under the lock */
        if (zone->nr_reserved_highatomic >= max_managed)
                goto out_unlock;

        /* Yoink! */
        mt = get_pageblock_migratetype(page);
        if (!is_migrate_highatomic(mt) && !is_migrate_isolate(mt)
            && !is_migrate_cma(mt)) {
                zone->nr_reserved_highatomic += pageblock_nr_pages;
                set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
                move_freepages_block(zone, page, MIGRATE_HIGHATOMIC, NULL);
        }

out_unlock:
        spin_unlock_irqrestore(&zone->lock, flags);
}

/*
 * Used when an allocation is about to fail under memory pressure. This
 * potentially hurts the reliability of high-order allocations when under
 * intense memory pressure but failed atomic allocations should be easier
 * to recover from than an OOM.
 *
 * If @force is true, try to unreserve a pageblock even though highatomic
 * pageblock is exhausted.
 */
static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
                                                bool force)
{
        struct zonelist *zonelist = ac->zonelist;
        unsigned long flags;
        struct zoneref *z;
        struct zone *zone;
        struct page *page;
        int order;
        bool ret;

        for_each_zone_zonelist_nodemask(zone, z, zonelist, ac->highest_zoneidx,
                                                                ac->nodemask) {
                /*
                 * Preserve at least one pageblock unless memory pressure
                 * is really high.
                 */
                if (!force && zone->nr_reserved_highatomic <=
                                        pageblock_nr_pages)
                        continue;

                spin_lock_irqsave(&zone->lock, flags);
                for (order = 0; order < MAX_ORDER; order++) {
                        struct free_area *area = &(zone->free_area[order]);

                        page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);
                        if (!page)
                                continue;

                        /*
                         * In page freeing path, migratetype change is racy so
                         * we can counter several free pages in a pageblock
                         * in this loop although we changed the pageblock type
                         * from highatomic to ac->migratetype. So we should
                         * adjust the count once.
                         */
                        if (is_migrate_highatomic_page(page)) {
                                /*
                                 * It should never happen but changes to
                                 * locking could inadvertently allow a per-cpu
                                 * drain to add pages to MIGRATE_HIGHATOMIC
                                 * while unreserving so be safe and watch for
                                 * underflows.
                                 */
                                zone->nr_reserved_highatomic -= min(
                                                pageblock_nr_pages,
                                                zone->nr_reserved_highatomic);
                        }

                        /*
                         * Convert to ac->migratetype and avoid the normal
                         * pageblock stealing heuristics. Minimally, the caller
                         * is doing the work and needs the pages. More
                         * importantly, if the block was always converted to
                         * MIGRATE_UNMOVABLE or another type then the number
                         * of pageblocks that cannot be completely freed
                         * may increase.
                         */
                        set_pageblock_migratetype(page, ac->migratetype);
                        ret = move_freepages_block(zone, page, ac->migratetype,
                                                                        NULL);
                        if (ret) {
                                spin_unlock_irqrestore(&zone->lock, flags);
                                return ret;
                        }
                }
                spin_unlock_irqrestore(&zone->lock, flags);
        }

        return false;
}

/*
 * Try finding a free buddy page on the fallback list and put it on the free
 * list of requested migratetype, possibly along with other pages from the same
 * block, depending on fragmentation avoidance heuristics. Returns true if
 * fallback was found so that __rmqueue_smallest() can grab it.
 *
 * The use of signed ints for order and current_order is a deliberate
 * deviation from the rest of this file, to make the for loop
 * condition simpler.
 */
static __always_inline bool
__rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
                                                unsigned int alloc_flags)
{
        struct free_area *area;
        int current_order;
        int min_order = order;
        struct page *page;
        int fallback_mt;
        bool can_steal;

        /*
         * Do not steal pages from freelists belonging to other pageblocks
         * i.e. orders < pageblock_order. If there are no local zones free,
         * the zonelists will be reiterated without ALLOC_NOFRAGMENT.
         */
        if (alloc_flags & ALLOC_NOFRAGMENT)
                min_order = pageblock_order;

        /*
         * Find the largest available free page in the other list. This roughly
         * approximates finding the pageblock with the most free pages, which
         * would be too costly to do exactly.
         */
        for (current_order = MAX_ORDER - 1; current_order >= min_order;
                                --current_order) {
                area = &(zone->free_area[current_order]);
                fallback_mt = find_suitable_fallback(area, current_order,
                                start_migratetype, false, &can_steal);
                if (fallback_mt == -1)
                        continue;

                /*
                 * We cannot steal all free pages from the pageblock and the
                 * requested migratetype is movable. In that case it's better to
                 * steal and split the smallest available page instead of the
                 * largest available page, because even if the next movable
                 * allocation falls back into a different pageblock than this
                 * one, it won't cause permanent fragmentation.
                 */
                if (!can_steal && start_migratetype == MIGRATE_MOVABLE
                                        && current_order > order)
                        goto find_smallest;

                goto do_steal;
        }

        return false;

find_smallest:
        for (current_order = order; current_order < MAX_ORDER;
                                                        current_order++) {
                area = &(zone->free_area[current_order]);
                fallback_mt = find_suitable_fallback(area, current_order,
                                start_migratetype, false, &can_steal);
                if (fallback_mt != -1)
                        break;
        }

        /*
         * This should not happen - we already found a suitable fallback
         * when looking for the largest page.
         */
        VM_BUG_ON(current_order == MAX_ORDER);

do_steal:
        page = get_page_from_free_area(area, fallback_mt);

        steal_suitable_fallback(zone, page, alloc_flags, start_migratetype,
                                                                can_steal);

        trace_mm_page_alloc_extfrag(page, order, current_order,
                start_migratetype, fallback_mt);

        return true;

}

/*
 * Do the hard work of removing an element from the buddy allocator.
 * Call me with the zone->lock already held.
 */
static __always_inline struct page *
__rmqueue(struct zone *zone, unsigned int order, int migratetype,
                                                unsigned int alloc_flags)
{
        struct page *page;

        if (IS_ENABLED(CONFIG_CMA)) {
                /*
                 * Balance movable allocations between regular and CMA areas by
                 * allocating from CMA when over half of the zone's free memory
                 * is in the CMA area.
                 */
                if (alloc_flags & ALLOC_CMA &&
                    zone_page_state(zone, NR_FREE_CMA_PAGES) >
                    zone_page_state(zone, NR_FREE_PAGES) / 2) {
                        page = __rmqueue_cma_fallback(zone, order);
                        if (page)
                                goto out;
                }
        }
retry:
        page = __rmqueue_smallest(zone, order, migratetype);
        if (unlikely(!page)) {
                if (alloc_flags & ALLOC_CMA)
                        page = __rmqueue_cma_fallback(zone, order);

                if (!page && __rmqueue_fallback(zone, order, migratetype,
                                                                alloc_flags))
                        goto retry;
        }
out:
        if (page)
                trace_mm_page_alloc_zone_locked(page, order, migratetype);
        return page;
}

/*
 * Obtain a specified number of elements from the buddy allocator, all under
 * a single hold of the lock, for efficiency.  Add them to the supplied list.
 * Returns the number of new pages which were placed at *list.
 */
static int rmqueue_bulk(struct zone *zone, unsigned int order,
                        unsigned long count, struct list_head *list,
                        int migratetype, unsigned int alloc_flags)
{
        int i, allocated = 0;

        /*
         * local_lock_irq held so equivalent to spin_lock_irqsave for
         * both PREEMPT_RT and non-PREEMPT_RT configurations.
         */
        spin_lock(&zone->lock);
        for (i = 0; i < count; ++i) {
                struct page *page = __rmqueue(zone, order, migratetype,
                                                                alloc_flags);
                if (unlikely(page == NULL))
                        break;

                if (unlikely(check_pcp_refill(page)))
                        continue;

                /*
                 * Split buddy pages returned by expand() are received here in
                 * physical page order. The page is added to the tail of
                 * caller's list. From the callers perspective, the linked list
                 * is ordered by page number under some conditions. This is
                 * useful for IO devices that can forward direction from the
                 * head, thus also in the physical page order. This is useful
                 * for IO devices that can merge IO requests if the physical
                 * pages are ordered properly.
                 */
                list_add_tail(&page->lru, list);
                allocated++;
                if (is_migrate_cma(get_pcppage_migratetype(page)))
                        __mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
                                              -(1 << order));
        }

        /*
         * i pages were removed from the buddy list even if some leak due
         * to check_pcp_refill failing so adjust NR_FREE_PAGES based
         * on i. Do not confuse with 'allocated' which is the number of
         * pages added to the pcp list.
         */
        __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
        spin_unlock(&zone->lock);
        return allocated;
}

#ifdef CONFIG_NUMA
/*
 * Called from the vmstat counter updater to drain pagesets of this
 * currently executing processor on remote nodes after they have
 * expired.
 *
 * Note that this function must be called with the thread pinned to
 * a single processor.
 */
void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
{
        unsigned long flags;
        int to_drain, batch;

        local_lock_irqsave(&pagesets.lock, flags);
        batch = READ_ONCE(pcp->batch);
        to_drain = min(pcp->count, batch);
        if (to_drain > 0)
                free_pcppages_bulk(zone, to_drain, pcp);
        local_unlock_irqrestore(&pagesets.lock, flags);
}
#endif

/*
 * Drain pcplists of the indicated processor and zone.
 *
 * The processor must either be the current processor and the
 * thread pinned to the current processor or a processor that
 * is not online.
 */
static void drain_pages_zone(unsigned int cpu, struct zone *zone)
{
        unsigned long flags;
        struct per_cpu_pages *pcp;

        local_lock_irqsave(&pagesets.lock, flags);

        pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
        if (pcp->count)
                free_pcppages_bulk(zone, pcp->count, pcp);

        local_unlock_irqrestore(&pagesets.lock, flags);
}

/*
 * Drain pcplists of all zones on the indicated processor.
 *
 * The processor must either be the current processor and the
 * thread pinned to the current processor or a processor that
 * is not online.
 */
static void drain_pages(unsigned int cpu)
{
        struct zone *zone;

        for_each_populated_zone(zone) {
                drain_pages_zone(cpu, zone);
        }
}

/*
 * Spill all of this CPU's per-cpu pages back into the buddy allocator.
 *
 * The CPU has to be pinned. When zone parameter is non-NULL, spill just
 * the single zone's pages.
 */
void drain_local_pages(struct zone *zone)
{
        int cpu = smp_processor_id();

        if (zone)
                drain_pages_zone(cpu, zone);
        else
                drain_pages(cpu);
}

static void drain_local_pages_wq(struct work_struct *work)
{
        struct pcpu_drain *drain;

        drain = container_of(work, struct pcpu_drain, work);

        /*
         * drain_all_pages doesn't use proper cpu hotplug protection so
         * we can race with cpu offline when the WQ can move this from
         * a cpu pinned worker to an unbound one. We can operate on a different
         * cpu which is alright but we also have to make sure to not move to
         * a different one.
         */
        migrate_disable();
        drain_local_pages(drain->zone);
        migrate_enable();
}

/*
 * The implementation of drain_all_pages(), exposing an extra parameter to
 * drain on all cpus.
 *
 * drain_all_pages() is optimized to only execute on cpus where pcplists are
 * not empty. The check for non-emptiness can however race with a free to
 * pcplist that has not yet increased the pcp->count from 0 to 1. Callers
 * that need the guarantee that every CPU has drained can disable the
 * optimizing racy check.
 */
static void __drain_all_pages(struct zone *zone, bool force_all_cpus)
{
        int cpu;

        /*
         * Allocate in the BSS so we won't require allocation in
         * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
         */
        static cpumask_t cpus_with_pcps;

        /*
         * Make sure nobody triggers this path before mm_percpu_wq is fully
         * initialized.
         */
        if (WARN_ON_ONCE(!mm_percpu_wq))
                return;

        /*
         * Do not drain if one is already in progress unless it's specific to
         * a zone. Such callers are primarily CMA and memory hotplug and need
         * the drain to be complete when the call returns.
         */
        if (unlikely(!mutex_trylock(&pcpu_drain_mutex))) {
                if (!zone)
                        return;
                mutex_lock(&pcpu_drain_mutex);
        }

        /*
         * We don't care about racing with CPU hotplug event
         * as offline notification will cause the notified
         * cpu to drain that CPU pcps and on_each_cpu_mask
         * disables preemption as part of its processing
         */
        for_each_online_cpu(cpu) {
                struct per_cpu_pages *pcp;
                struct zone *z;
                bool has_pcps = false;

                if (force_all_cpus) {
                        /*
                         * The pcp.count check is racy, some callers need a
                         * guarantee that no cpu is missed.
                         */
                        has_pcps = true;
                } else if (zone) {
                        pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
                        if (pcp->count)
                                has_pcps = true;
                } else {
                        for_each_populated_zone(z) {
                                pcp = per_cpu_ptr(z->per_cpu_pageset, cpu);
                                if (pcp->count) {
                                        has_pcps = true;
                                        break;
                                }
                        }
                }

                if (has_pcps)
                        cpumask_set_cpu(cpu, &cpus_with_pcps);
                else
                        cpumask_clear_cpu(cpu, &cpus_with_pcps);
        }

        for_each_cpu(cpu, &cpus_with_pcps) {
                struct pcpu_drain *drain = per_cpu_ptr(&pcpu_drain, cpu);

                drain->zone = zone;
                INIT_WORK(&drain->work, drain_local_pages_wq);
                queue_work_on(cpu, mm_percpu_wq, &drain->work);
        }
        for_each_cpu(cpu, &cpus_with_pcps)
                flush_work(&per_cpu_ptr(&pcpu_drain, cpu)->work);

        mutex_unlock(&pcpu_drain_mutex);
}

/*
 * Spill all the per-cpu pages from all CPUs back into the buddy allocator.
 *
 * When zone parameter is non-NULL, spill just the single zone's pages.
 *
 * Note that this can be extremely slow as the draining happens in a workqueue.
 */
void drain_all_pages(struct zone *zone)
{
        __drain_all_pages(zone, false);
}

#ifdef CONFIG_HIBERNATION

/*
 * Touch the watchdog for every WD_PAGE_COUNT pages.
 */
#define WD_PAGE_COUNT   (128*1024)

void mark_free_pages(struct zone *zone)
{
        unsigned long pfn, max_zone_pfn, page_count = WD_PAGE_COUNT;
        unsigned long flags;
        unsigned int order, t;
        struct page *page;

        if (zone_is_empty(zone))
                return;

        spin_lock_irqsave(&zone->lock, flags);

        max_zone_pfn = zone_end_pfn(zone);
        for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
                if (pfn_valid(pfn)) {
                        page = pfn_to_page(pfn);

                        if (!--page_count) {
                                touch_nmi_watchdog();
                                page_count = WD_PAGE_COUNT;
                        }

                        if (page_zone(page) != zone)
                                continue;

                        if (!swsusp_page_is_forbidden(page))
                                swsusp_unset_page_free(page);
                }

        for_each_migratetype_order(order, t) {
                list_for_each_entry(page,
                                &zone->free_area[order].free_list[t], lru) {
                        unsigned long i;

                        pfn = page_to_pfn(page);
                        for (i = 0; i < (1UL << order); i++) {
                                if (!--page_count) {
                                        touch_nmi_watchdog();
                                        page_count = WD_PAGE_COUNT;
                                }
                                swsusp_set_page_free(pfn_to_page(pfn + i));
                        }
                }
        }
        spin_unlock_irqrestore(&zone->lock, flags);
}
#endif /* CONFIG_PM */

static bool free_unref_page_prepare(struct page *page, unsigned long pfn,
                                                        unsigned int order)
{
        int migratetype;

        if (!free_pcp_prepare(page, order))
                return false;

        migratetype = get_pfnblock_migratetype(page, pfn);
        set_pcppage_migratetype(page, migratetype);
        return true;
}

static int nr_pcp_free(struct per_cpu_pages *pcp, int high, int batch)
{
        int min_nr_free, max_nr_free;

        /* Check for PCP disabled or boot pageset */
        if (unlikely(high < batch))
                return 1;

        /* Leave at least pcp->batch pages on the list */
        min_nr_free = batch;
        max_nr_free = high - batch;

        /*
         * Double the number of pages freed each time there is subsequent
         * freeing of pages without any allocation.
         */
        batch <<= pcp->free_factor;
        if (batch < max_nr_free)
                pcp->free_factor++;
        batch = clamp(batch, min_nr_free, max_nr_free);

        return batch;
}

static int nr_pcp_high(struct per_cpu_pages *pcp, struct zone *zone)
{
        int high = READ_ONCE(pcp->high);

        if (unlikely(!high))
                return 0;

        if (!test_bit(ZONE_RECLAIM_ACTIVE, &zone->flags))
                return high;

        /*
         * If reclaim is active, limit the number of pages that can be
         * stored on pcp lists
         */
        return min(READ_ONCE(pcp->batch) << 2, high);
}

static void free_unref_page_commit(struct page *page, unsigned long pfn,
                                   int migratetype, unsigned int order)
{
        struct zone *zone = page_zone(page);
        struct per_cpu_pages *pcp;
        int high;
        int pindex;

        __count_vm_event(PGFREE);
        pcp = this_cpu_ptr(zone->per_cpu_pageset);
        pindex = order_to_pindex(migratetype, order);
        list_add(&page->lru, &pcp->lists[pindex]);
        pcp->count += 1 << order;
        high = nr_pcp_high(pcp, zone);
        if (pcp->count >= high) {
                int batch = READ_ONCE(pcp->batch);

                free_pcppages_bulk(zone, nr_pcp_free(pcp, high, batch), pcp);
        }
}

/*
 * Free a pcp page
 */
void free_unref_page(struct page *page, unsigned int order)
{
        unsigned long flags;
        unsigned long pfn = page_to_pfn(page);
        int migratetype;

        if (!free_unref_page_prepare(page, pfn, order))
                return;

        /*
         * We only track unmovable, reclaimable and movable on pcp lists.
         * Place ISOLATE pages on the isolated list because they are being
         * offlined but treat HIGHATOMIC as movable pages so we can get those
         * areas back if necessary. Otherwise, we may have to free
         * excessively into the page allocator
         */
        migratetype = get_pcppage_migratetype(page);
        if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
                if (unlikely(is_migrate_isolate(migratetype))) {
                        free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_NONE);
                        return;
                }
                migratetype = MIGRATE_MOVABLE;
        }

        local_lock_irqsave(&pagesets.lock, flags);
        free_unref_page_commit(page, pfn, migratetype, order);
        local_unlock_irqrestore(&pagesets.lock, flags);
}

/*
 * Free a list of 0-order pages
 */
void free_unref_page_list(struct list_head *list)
{
        struct page *page, *next;
        unsigned long flags, pfn;
        int batch_count = 0;
        int migratetype;

        /* Prepare pages for freeing */
        list_for_each_entry_safe(page, next, list, lru) {
                pfn = page_to_pfn(page);
                if (!free_unref_page_prepare(page, pfn, 0)) {
                        list_del(&page->lru);
                        continue;
                }

                /*
                 * Free isolated pages directly to the allocator, see
                 * comment in free_unref_page.
                 */
                migratetype = get_pcppage_migratetype(page);
                if (unlikely(is_migrate_isolate(migratetype))) {
                        list_del(&page->lru);
                        free_one_page(page_zone(page), page, pfn, 0, migratetype, FPI_NONE);
                        continue;
                }

                set_page_private(page, pfn);
        }

        local_lock_irqsave(&pagesets.lock, flags);
        list_for_each_entry_safe(page, next, list, lru) {
                pfn = page_private(page);
                set_page_private(page, 0);

                /*
                 * Non-isolated types over MIGRATE_PCPTYPES get added
                 * to the MIGRATE_MOVABLE pcp list.
                 */
                migratetype = get_pcppage_migratetype(page);
                if (unlikely(migratetype >= MIGRATE_PCPTYPES))
                        migratetype = MIGRATE_MOVABLE;

                trace_mm_page_free_batched(page);
                free_unref_page_commit(page, pfn, migratetype, 0);

                /*
                 * Guard against excessive IRQ disabled times when we get
                 * a large list of pages to free.
                 */
                if (++batch_count == SWAP_CLUSTER_MAX) {
                        local_unlock_irqrestore(&pagesets.lock, flags);
                        batch_count = 0;
                        local_lock_irqsave(&pagesets.lock, flags);
                }
        }
        local_unlock_irqrestore(&pagesets.lock, flags);
}

/*
 * split_page takes a non-compound higher-order page, and splits it into
 * n (1<<order) sub-pages: page[0..n]
 * Each sub-page must be freed individually.
 *
 * Note: this is probably too low level an operation for use in drivers.
 * Please consult with lkml before using this in your driver.
 */
void split_page(struct page *page, unsigned int order)
{
        int i;

        VM_BUG_ON_PAGE(PageCompound(page), page);
        VM_BUG_ON_PAGE(!page_count(page), page);

        for (i = 1; i < (1 << order); i++)
                set_page_refcounted(page + i);
        split_page_owner(page, 1 << order);
        split_page_memcg(page, 1 << order);
}
EXPORT_SYMBOL_GPL(split_page);

int __isolate_free_page(struct page *page, unsigned int order)
{
        unsigned long watermark;
        struct zone *zone;
        int mt;

        BUG_ON(!PageBuddy(page));

        zone = page_zone(page);
        mt = get_pageblock_migratetype(page);

        if (!is_migrate_isolate(mt)) {
                /*
                 * Obey watermarks as if the page was being allocated. We can
                 * emulate a high-order watermark check with a raised order-0
                 * watermark, because we already know our high-order page
                 * exists.
                 */
                watermark = zone->_watermark[WMARK_MIN] + (1UL << order);
                if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
                        return 0;

                __mod_zone_freepage_state(zone, -(1UL << order), mt);
        }

        /* Remove page from free list */

        del_page_from_free_list(page, zone, order);

        /*
         * Set the pageblock if the isolated page is at least half of a
         * pageblock
         */
        if (order >= pageblock_order - 1) {
                struct page *endpage = page + (1 << order) - 1;
                for (; page < endpage; page += pageblock_nr_pages) {
                        int mt = get_pageblock_migratetype(page);
                        if (!is_migrate_isolate(mt) && !is_migrate_cma(mt)
                            && !is_migrate_highatomic(mt))
                                set_pageblock_migratetype(page,
                                                          MIGRATE_MOVABLE);
                }
        }


        return 1UL << order;
}

/**
 * __putback_isolated_page - Return a now-isolated page back where we got it
 * @page: Page that was isolated
 * @order: Order of the isolated page
 * @mt: The page's pageblock's migratetype
 *
 * This function is meant to return a page pulled from the free lists via
 * __isolate_free_page back to the free lists they were pulled from.
 */
void __putback_isolated_page(struct page *page, unsigned int order, int mt)
{
        struct zone *zone = page_zone(page);

        /* zone lock should be held when this function is called */
        lockdep_assert_held(&zone->lock);

        /* Return isolated page to tail of freelist. */
        __free_one_page(page, page_to_pfn(page), zone, order, mt,
                        FPI_SKIP_REPORT_NOTIFY | FPI_TO_TAIL);
}

/*
 * Update NUMA hit/miss statistics
 *
 * Must be called with interrupts disabled.
 */
static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
                                   long nr_account)
{
#ifdef CONFIG_NUMA
        enum numa_stat_item local_stat = NUMA_LOCAL;

        /* skip numa counters update if numa stats is disabled */
        if (!static_branch_likely(&vm_numa_stat_key))
                return;

        if (zone_to_nid(z) != numa_node_id())
                local_stat = NUMA_OTHER;

        if (zone_to_nid(z) == zone_to_nid(preferred_zone))
                __count_numa_events(z, NUMA_HIT, nr_account);
        else {
                __count_numa_events(z, NUMA_MISS, nr_account);
                __count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);
        }
        __count_numa_events(z, local_stat, nr_account);
#endif
}

/* Remove page from the per-cpu list, caller must protect the list */
static inline
struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
                        int migratetype,
                        unsigned int alloc_flags,
                        struct per_cpu_pages *pcp,
                        struct list_head *list)
{
        struct page *page;

        do {
                if (list_empty(list)) {
                        int batch = READ_ONCE(pcp->batch);
                        int alloced;

                        /*
                         * Scale batch relative to order if batch implies
                         * free pages can be stored on the PCP. Batch can
                         * be 1 for small zones or for boot pagesets which
                         * should never store free pages as the pages may
                         * belong to arbitrary zones.
                         */
                        if (batch > 1)
                                batch = max(batch >> order, 2);
                        alloced = rmqueue_bulk(zone, order,
                                        batch, list,
                                        migratetype, alloc_flags);

                        pcp->count += alloced << order;
                        if (unlikely(list_empty(list)))
                                return NULL;
                }

                page = list_first_entry(list, struct page, lru);
                list_del(&page->lru);
                pcp->count -= 1 << order;
        } while (check_new_pcp(page));

        return page;
}

/* Lock and remove page from the per-cpu list */
static struct page *rmqueue_pcplist(struct zone *preferred_zone,
                        struct zone *zone, unsigned int order,
                        gfp_t gfp_flags, int migratetype,
                        unsigned int alloc_flags)
{
        struct per_cpu_pages *pcp;
        struct list_head *list;
        struct page *page;
        unsigned long flags;

        local_lock_irqsave(&pagesets.lock, flags);

        /*
         * On allocation, reduce the number of pages that are batch freed.
         * See nr_pcp_free() where free_factor is increased for subsequent
         * frees.
         */
        pcp = this_cpu_ptr(zone->per_cpu_pageset);
        pcp->free_factor >>= 1;
        list = &pcp->lists[order_to_pindex(migratetype, order)];
        page = __rmqueue_pcplist(zone, order, migratetype, alloc_flags, pcp, list);
        local_unlock_irqrestore(&pagesets.lock, flags);
        if (page) {
                __count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
                zone_statistics(preferred_zone, zone, 1);
        }
        return page;
}

/*
 * Allocate a page from the given zone. Use pcplists for order-0 allocations.
 */
static inline
struct page *rmqueue(struct zone *preferred_zone,
                        struct zone *zone, unsigned int order,
                        gfp_t gfp_flags, unsigned int alloc_flags,
                        int migratetype)
{
        unsigned long flags;
        struct page *page;

        if (likely(pcp_allowed_order(order))) {
                /*
                 * MIGRATE_MOVABLE pcplist could have the pages on CMA area and
                 * we need to skip it when CMA area isn't allowed.
                 */
                if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA ||
                                migratetype != MIGRATE_MOVABLE) {
                        page = rmqueue_pcplist(preferred_zone, zone, order,
                                        gfp_flags, migratetype, alloc_flags);
                        goto out;
                }
        }

        /*
         * We most definitely don't want callers attempting to
         * allocate greater than order-1 page units with __GFP_NOFAIL.
         */
        WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
        spin_lock_irqsave(&zone->lock, flags);

        do {
                page = NULL;
                /*
                 * order-0 request can reach here when the pcplist is skipped
                 * due to non-CMA allocation context. HIGHATOMIC area is
                 * reserved for high-order atomic allocation, so order-0
                 * request should skip it.
                 */
                if (order > 0 && alloc_flags & ALLOC_HARDER) {
                        page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
                        if (page)
                                trace_mm_page_alloc_zone_locked(page, order, migratetype);
                }
                if (!page)
                        page = __rmqueue(zone, order, migratetype, alloc_flags);
        } while (page && check_new_pages(page, order));
        if (!page)
                goto failed;

        __mod_zone_freepage_state(zone, -(1 << order),
                                  get_pcppage_migratetype(page));
        spin_unlock_irqrestore(&zone->lock, flags);

        __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
        zone_statistics(preferred_zone, zone, 1);

out:
        /* Separate test+clear to avoid unnecessary atomics */
        if (test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags)) {
                clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
                wakeup_kswapd(zone, 0, 0, zone_idx(zone));
        }

        VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
        return page;

failed:
        spin_unlock_irqrestore(&zone->lock, flags);
        return NULL;
}

#ifdef CONFIG_FAIL_PAGE_ALLOC

static struct {
        struct fault_attr attr;

        bool ignore_gfp_highmem;
        bool ignore_gfp_reclaim;
        u32 min_order;
} fail_page_alloc = {
        .attr = FAULT_ATTR_INITIALIZER,
        .ignore_gfp_reclaim = true,
        .ignore_gfp_highmem = true,
        .min_order = 1,
};

static int __init setup_fail_page_alloc(char *str)
{
        return setup_fault_attr(&fail_page_alloc.attr, str);
}
__setup("fail_page_alloc=", setup_fail_page_alloc);

static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
{
        if (order < fail_page_alloc.min_order)
                return false;
        if (gfp_mask & __GFP_NOFAIL)
                return false;
        if (fail_page_alloc.ignore_gfp_highmem && (gfp_mask & __GFP_HIGHMEM))
                return false;
        if (fail_page_alloc.ignore_gfp_reclaim &&
                        (gfp_mask & __GFP_DIRECT_RECLAIM))
                return false;

        return should_fail(&fail_page_alloc.attr, 1 << order);
}

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS

static int __init fail_page_alloc_debugfs(void)
{
        umode_t mode = S_IFREG | 0600;
        struct dentry *dir;

        dir = fault_create_debugfs_attr("fail_page_alloc", NULL,
                                        &fail_page_alloc.attr);

        debugfs_create_bool("ignore-gfp-wait", mode, dir,
                            &fail_page_alloc.ignore_gfp_reclaim);
        debugfs_create_bool("ignore-gfp-highmem", mode, dir,
                            &fail_page_alloc.ignore_gfp_highmem);
        debugfs_create_u32("min-order", mode, dir, &fail_page_alloc.min_order);

        return 0;
}

late_initcall(fail_page_alloc_debugfs);

#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */

#else /* CONFIG_FAIL_PAGE_ALLOC */

static inline bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
{
        return false;
}

#endif /* CONFIG_FAIL_PAGE_ALLOC */

noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
{
        return __should_fail_alloc_page(gfp_mask, order);
}
ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE);

static inline long __zone_watermark_unusable_free(struct zone *z,
                                unsigned int order, unsigned int alloc_flags)
{
        const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));
        long unusable_free = (1 << order) - 1;

        /*
         * If the caller does not have rights to ALLOC_HARDER then subtract
         * the high-atomic reserves. This will over-estimate the size of the
         * atomic reserve but it avoids a search.
         */
        if (likely(!alloc_harder))
                unusable_free += z->nr_reserved_highatomic;

#ifdef CONFIG_CMA
        /* If allocation can't use CMA areas don't use free CMA pages */
        if (!(alloc_flags & ALLOC_CMA))
                unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
#endif

        return unusable_free;
}

/*
 * Return true if free base pages are above 'mark'. For high-order checks it
 * will return true of the order-0 watermark is reached and there is at least
 * one free page of a suitable size. Checking now avoids taking the zone lock
 * to check in the allocation paths if no pages are free.
 */
bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
                         int highest_zoneidx, unsigned int alloc_flags,
                         long free_pages)
{
        long min = mark;
        int o;
        const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));

        /* free_pages may go negative - that's OK */
        free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);

        if (alloc_flags & ALLOC_HIGH)
                min -= min / 2;

        if (unlikely(alloc_harder)) {
                /*
                 * OOM victims can try even harder than normal ALLOC_HARDER
                 * users on the grounds that it's definitely going to be in
                 * the exit path shortly and free memory. Any allocation it
                 * makes during the free path will be small and short-lived.
                 */
                if (alloc_flags & ALLOC_OOM)
                        min -= min / 2;
                else
                        min -= min / 4;
        }

        /*
         * Check watermarks for an order-0 allocation request. If these
         * are not met, then a high-order request also cannot go ahead
         * even if a suitable page happened to be free.
         */
        if (free_pages <= min + z->lowmem_reserve[highest_zoneidx])
                return false;

        /* If this is an order-0 request then the watermark is fine */
        if (!order)
                return true;

        /* For a high-order request, check at least one suitable page is free */
        for (o = order; o < MAX_ORDER; o++) {
                struct free_area *area = &z->free_area[o];
                int mt;

                if (!area->nr_free)
                        continue;

                for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
                        if (!free_area_empty(area, mt))
                                return true;
                }

#ifdef CONFIG_CMA
                if ((alloc_flags & ALLOC_CMA) &&
                    !free_area_empty(area, MIGRATE_CMA)) {
                        return true;
                }
#endif
                if (alloc_harder && !free_area_empty(area, MIGRATE_HIGHATOMIC))
                        return true;
        }
        return false;
}

bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
                      int highest_zoneidx, unsigned int alloc_flags)
{
        return __zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
                                        zone_page_state(z, NR_FREE_PAGES));
}

static inline bool zone_watermark_fast(struct zone *z, unsigned int order,
                                unsigned long mark, int highest_zoneidx,
                                unsigned int alloc_flags, gfp_t gfp_mask)
{
        long free_pages;

        free_pages = zone_page_state(z, NR_FREE_PAGES);

        /*
         * Fast check for order-0 only. If this fails then the reserves
         * need to be calculated.
         */
        if (!order) {
                long fast_free;

                fast_free = free_pages;
                fast_free -= __zone_watermark_unusable_free(z, 0, alloc_flags);
                if (fast_free > mark + z->lowmem_reserve[highest_zoneidx])
                        return true;
        }

        if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
                                        free_pages))
                return true;
        /*
         * Ignore watermark boosting for GFP_ATOMIC order-0 allocations
         * when checking the min watermark. The min watermark is the
         * point where boosting is ignored so that kswapd is woken up
         * when below the low watermark.
         */
        if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost
                && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) {
                mark = z->_watermark[WMARK_MIN];
                return __zone_watermark_ok(z, order, mark, highest_zoneidx,
                                        alloc_flags, free_pages);
        }

        return false;
}

bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
                        unsigned long mark, int highest_zoneidx)
{
        long free_pages = zone_page_state(z, NR_FREE_PAGES);

        if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark)
                free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES);

        return __zone_watermark_ok(z, order, mark, highest_zoneidx, 0,
                                                                free_pages);
}

#ifdef CONFIG_NUMA
int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE;

static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
        return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
                                node_reclaim_distance;
}
#else   /* CONFIG_NUMA */
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
        return true;
}
#endif  /* CONFIG_NUMA */

/*
 * The restriction on ZONE_DMA32 as being a suitable zone to use to avoid
 * fragmentation is subtle. If the preferred zone was HIGHMEM then
 * premature use of a lower zone may cause lowmem pressure problems that
 * are worse than fragmentation. If the next zone is ZONE_DMA then it is
 * probably too small. It only makes sense to spread allocations to avoid
 * fragmentation between the Normal and DMA32 zones.
 */
static inline unsigned int
alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
{
        unsigned int alloc_flags;

        /*
         * __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
         * to save a branch.
         */
        alloc_flags = (__force int) (gfp_mask & __GFP_KSWAPD_RECLAIM);

#ifdef CONFIG_ZONE_DMA32
        if (!zone)
                return alloc_flags;

        if (zone_idx(zone) != ZONE_NORMAL)
                return alloc_flags;

        /*
         * If ZONE_DMA32 exists, assume it is the one after ZONE_NORMAL and
         * the pointer is within zone->zone_pgdat->node_zones[]. Also assume
         * on UMA that if Normal is populated then so is DMA32.
         */
        BUILD_BUG_ON(ZONE_NORMAL - ZONE_DMA32 != 1);
        if (nr_online_nodes > 1 && !populated_zone(--zone))
                return alloc_flags;

        alloc_flags |= ALLOC_NOFRAGMENT;
#endif /* CONFIG_ZONE_DMA32 */
        return alloc_flags;
}

/* Must be called after current_gfp_context() which can change gfp_mask */
static inline unsigned int gfp_to_alloc_flags_cma(gfp_t gfp_mask,
                                                  unsigned int alloc_flags)
{
#ifdef CONFIG_CMA
        if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
                alloc_flags |= ALLOC_CMA;
#endif
        return alloc_flags;
}

/*
 * get_page_from_freelist goes through the zonelist trying to allocate
 * a page.
 */
static struct page *
get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
                                                const struct alloc_context *ac)
{
        struct zoneref *z;
        struct zone *zone;
        struct pglist_data *last_pgdat_dirty_limit = NULL;
        bool no_fallback;

retry:
        /*
         * Scan zonelist, looking for a zone with enough free.
         * See also __cpuset_node_allowed() comment in kernel/cpuset.c.
         */
        no_fallback = alloc_flags & ALLOC_NOFRAGMENT;
        z = ac->preferred_zoneref;
        for_next_zone_zonelist_nodemask(zone, z, ac->highest_zoneidx,
                                        ac->nodemask) {
                struct page *page;
                unsigned long mark;

                if (cpusets_enabled() &&
                        (alloc_flags & ALLOC_CPUSET) &&
                        !__cpuset_zone_allowed(zone, gfp_mask))
                                continue;
                /*
                 * When allocating a page cache page for writing, we
                 * want to get it from a node that is within its dirty
                 * limit, such that no single node holds more than its
                 * proportional share of globally allowed dirty pages.
                 * The dirty limits take into account the node's
                 * lowmem reserves and high watermark so that kswapd
                 * should be able to balance it without having to
                 * write pages from its LRU list.
                 *
                 * XXX: For now, allow allocations to potentially
                 * exceed the per-node dirty limit in the slowpath
                 * (spread_dirty_pages unset) before going into reclaim,
                 * which is important when on a NUMA setup the allowed
                 * nodes are together not big enough to reach the
                 * global limit.  The proper fix for these situations
                 * will require awareness of nodes in the
                 * dirty-throttling and the flusher threads.
                 */
                if (ac->spread_dirty_pages) {
                        if (last_pgdat_dirty_limit == zone->zone_pgdat)
                                continue;

                        if (!node_dirty_ok(zone->zone_pgdat)) {
                                last_pgdat_dirty_limit = zone->zone_pgdat;
                                continue;
                        }
                }

                if (no_fallback && nr_online_nodes > 1 &&
                    zone != ac->preferred_zoneref->zone) {
                        int local_nid;

                        /*
                         * If moving to a remote node, retry but allow
                         * fragmenting fallbacks. Locality is more important
                         * than fragmentation avoidance.
                         */
                        local_nid = zone_to_nid(ac->preferred_zoneref->zone);
                        if (zone_to_nid(zone) != local_nid) {
                                alloc_flags &= ~ALLOC_NOFRAGMENT;
                                goto retry;
                        }
                }

                mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
                if (!zone_watermark_fast(zone, order, mark,
                                       ac->highest_zoneidx, alloc_flags,
                                       gfp_mask)) {
                        int ret;

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
                        /*
                         * Watermark failed for this zone, but see if we can
                         * grow this zone if it contains deferred pages.
                         */
                        if (static_branch_unlikely(&deferred_pages)) {
                                if (_deferred_grow_zone(zone, order))
                                        goto try_this_zone;
                        }
#endif
                        /* Checked here to keep the fast path fast */
                        BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
                        if (alloc_flags & ALLOC_NO_WATERMARKS)
                                goto try_this_zone;

                        if (!node_reclaim_enabled() ||
                            !zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
                                continue;

                        ret = node_reclaim(zone->zone_pgdat, gfp_mask, order);
                        switch (ret) {
                        case NODE_RECLAIM_NOSCAN:
                                /* did not scan */
                                continue;
                        case NODE_RECLAIM_FULL:
                                /* scanned but unreclaimable */
                                continue;
                        default:
                                /* did we reclaim enough */
                                if (zone_watermark_ok(zone, order, mark,
                                        ac->highest_zoneidx, alloc_flags))
                                        goto try_this_zone;

                                continue;
                        }
                }

try_this_zone:
                page = rmqueue(ac->preferred_zoneref->zone, zone, order,
                                gfp_mask, alloc_flags, ac->migratetype);
                if (page) {
                        prep_new_page(page, order, gfp_mask, alloc_flags);

                        /*
                         * If this is a high-order atomic allocation then check
                         * if the pageblock should be reserved for the future
                         */
                        if (unlikely(order && (alloc_flags & ALLOC_HARDER)))
                                reserve_highatomic_pageblock(page, zone, order);

                        return page;
                } else {
#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
                        /* Try again if zone has deferred pages */
                        if (static_branch_unlikely(&deferred_pages)) {
                                if (_deferred_grow_zone(zone, order))
                                        goto try_this_zone;
                        }
#endif
                }
        }

        /*
         * It's possible on a UMA machine to get through all zones that are
         * fragmented. If avoiding fragmentation, reset and try again.
         */
        if (no_fallback) {
                alloc_flags &= ~ALLOC_NOFRAGMENT;
                goto retry;
        }

        return NULL;
}

static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
{
        unsigned int filter = SHOW_MEM_FILTER_NODES;

        /*
         * This documents exceptions given to allocations in certain
         * contexts that are allowed to allocate outside current's set
         * of allowed nodes.
         */
        if (!(gfp_mask & __GFP_NOMEMALLOC))
                if (tsk_is_oom_victim(current) ||
                    (current->flags & (PF_MEMALLOC | PF_EXITING)))
                        filter &= ~SHOW_MEM_FILTER_NODES;
        if (!in_task() || !(gfp_mask & __GFP_DIRECT_RECLAIM))
                filter &= ~SHOW_MEM_FILTER_NODES;

        show_mem(filter, nodemask);
}

void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
{
        struct va_format vaf;
        va_list args;
        static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);

        if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs))
                return;

        va_start(args, fmt);
        vaf.fmt = fmt;
        vaf.va = &args;
        pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl",
                        current->comm, &vaf, gfp_mask, &gfp_mask,
                        nodemask_pr_args(nodemask));
        va_end(args);

        cpuset_print_current_mems_allowed();
        pr_cont("\n");
        dump_stack();
        warn_alloc_show_mem(gfp_mask, nodemask);
}

static inline struct page *
__alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order,
                              unsigned int alloc_flags,
                              const struct alloc_context *ac)
{
        struct page *page;

        page = get_page_from_freelist(gfp_mask, order,
                        alloc_flags|ALLOC_CPUSET, ac);
        /*
         * fallback to ignore cpuset restriction if our nodes
         * are depleted
         */
        if (!page)
                page = get_page_from_freelist(gfp_mask, order,
                                alloc_flags, ac);

        return page;
}

static inline struct page *
__alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
        const struct alloc_context *ac, unsigned long *did_some_progress)
{
        struct oom_control oc = {
                .zonelist = ac->zonelist,
                .nodemask = ac->nodemask,
                .memcg = NULL,
                .gfp_mask = gfp_mask,
                .order = order,
        };
        struct page *page;

        *did_some_progress = 0;

        /*
         * Acquire the oom lock.  If that fails, somebody else is
         * making progress for us.
         */
        if (!mutex_trylock(&oom_lock)) {
                *did_some_progress = 1;
                schedule_timeout_uninterruptible(1);
                return NULL;
        }

        /*
         * Go through the zonelist yet one more time, keep very high watermark
         * here, this is only to catch a parallel oom killing, we must fail if
         * we're still under heavy pressure. But make sure that this reclaim
         * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY
         * allocation which will never fail due to oom_lock already held.
         */
        page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) &
                                      ~__GFP_DIRECT_RECLAIM, order,
                                      ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
        if (page)
                goto out;

        /* Coredumps can quickly deplete all memory reserves */
        if (current->flags & PF_DUMPCORE)
                goto out;
        /* The OOM killer will not help higher order allocs */
        if (order > PAGE_ALLOC_COSTLY_ORDER)
                goto out;
        /*
         * We have already exhausted all our reclaim opportunities without any
         * success so it is time to admit defeat. We will skip the OOM killer
         * because it is very likely that the caller has a more reasonable
         * fallback than shooting a random task.
         *
         * The OOM killer may not free memory on a specific node.
         */
        if (gfp_mask & (__GFP_RETRY_MAYFAIL | __GFP_THISNODE))
                goto out;
        /* The OOM killer does not needlessly kill tasks for lowmem */
        if (ac->highest_zoneidx < ZONE_NORMAL)
                goto out;
        if (pm_suspended_storage())
                goto out;
        /*
         * XXX: GFP_NOFS allocations should rather fail than rely on
         * other request to make a forward progress.
         * We are in an unfortunate situation where out_of_memory cannot
         * do much for this context but let's try it to at least get
         * access to memory reserved if the current task is killed (see
         * out_of_memory). Once filesystems are ready to handle allocation
         * failures more gracefully we should just bail out here.
         */

        /* Exhausted what can be done so it's blame time */
        if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
                *did_some_progress = 1;

                /*
                 * Help non-failing allocations by giving them access to memory
                 * reserves
                 */
                if (gfp_mask & __GFP_NOFAIL)
                        page = __alloc_pages_cpuset_fallback(gfp_mask, order,
                                        ALLOC_NO_WATERMARKS, ac);
        }
out:
        mutex_unlock(&oom_lock);
        return page;
}

/*
 * Maximum number of compaction retries with a progress before OOM
 * killer is consider as the only way to move forward.
 */
#define MAX_COMPACT_RETRIES 16

#ifdef CONFIG_COMPACTION
/* Try memory compaction for high-order allocations before reclaim */
static struct page *
__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
                unsigned int alloc_flags, const struct alloc_context *ac,
                enum compact_priority prio, enum compact_result *compact_result)
{
        struct page *page = NULL;
        unsigned long pflags;
        unsigned int noreclaim_flag;

        if (!order)
                return NULL;

        psi_memstall_enter(&pflags);
        delayacct_compact_start();
        noreclaim_flag = memalloc_noreclaim_save();

        *compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
                                                                prio, &page);

        memalloc_noreclaim_restore(noreclaim_flag);
        psi_memstall_leave(&pflags);
        delayacct_compact_end();

        if (*compact_result == COMPACT_SKIPPED)
                return NULL;
        /*
         * At least in one zone compaction wasn't deferred or skipped, so let's
         * count a compaction stall
         */
        count_vm_event(COMPACTSTALL);

        /* Prep a captured page if available */
        if (page)
                prep_new_page(page, order, gfp_mask, alloc_flags);

        /* Try get a page from the freelist if available */
        if (!page)
                page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);

        if (page) {
                struct zone *zone = page_zone(page);

                zone->compact_blockskip_flush = false;
                compaction_defer_reset(zone, order, true);
                count_vm_event(COMPACTSUCCESS);
                return page;
        }

        /*
         * It's bad if compaction run occurs and fails. The most likely reason
         * is that pages exist, but not enough to satisfy watermarks.
         */
        count_vm_event(COMPACTFAIL);

        cond_resched();

        return NULL;
}

static inline bool
should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
                     enum compact_result compact_result,
                     enum compact_priority *compact_priority,
                     int *compaction_retries)
{
        int max_retries = MAX_COMPACT_RETRIES;
        int min_priority;
        bool ret = false;
        int retries = *compaction_retries;
        enum compact_priority priority = *compact_priority;

        if (!order)
                return false;

        if (fatal_signal_pending(current))
                return false;

        if (compaction_made_progress(compact_result))
                (*compaction_retries)++;

        /*
         * compaction considers all the zone as desperately out of memory
         * so it doesn't really make much sense to retry except when the
         * failure could be caused by insufficient priority
         */
        if (compaction_failed(compact_result))
                goto check_priority;

        /*
         * compaction was skipped because there are not enough order-0 pages
         * to work with, so we retry only if it looks like reclaim can help.
         */
        if (compaction_needs_reclaim(compact_result)) {
                ret = compaction_zonelist_suitable(ac, order, alloc_flags);
                goto out;
        }

        /*
         * make sure the compaction wasn't deferred or didn't bail out early
         * due to locks contention before we declare that we should give up.
         * But the next retry should use a higher priority if allowed, so
         * we don't just keep bailing out endlessly.
         */
        if (compaction_withdrawn(compact_result)) {
                goto check_priority;
        }

        /*
         * !costly requests are much more important than __GFP_RETRY_MAYFAIL
         * costly ones because they are de facto nofail and invoke OOM
         * killer to move on while costly can fail and users are ready
         * to cope with that. 1/4 retries is rather arbitrary but we
         * would need much more detailed feedback from compaction to
         * make a better decision.
         */
        if (order > PAGE_ALLOC_COSTLY_ORDER)
                max_retries /= 4;
        if (*compaction_retries <= max_retries) {
                ret = true;
                goto out;
        }

        /*
         * Make sure there are attempts at the highest priority if we exhausted
         * all retries or failed at the lower priorities.
         */
check_priority:
        min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
                        MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;

        if (*compact_priority > min_priority) {
                (*compact_priority)--;
                *compaction_retries = 0;
                ret = true;
        }
out:
        trace_compact_retry(order, priority, compact_result, retries, max_retries, ret);
        return ret;
}
#else
static inline struct page *
__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
                unsigned int alloc_flags, const struct alloc_context *ac,
                enum compact_priority prio, enum compact_result *compact_result)
{
        *compact_result = COMPACT_SKIPPED;
        return NULL;
}

static inline bool
should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags,
                     enum compact_result compact_result,
                     enum compact_priority *compact_priority,
                     int *compaction_retries)
{
        struct zone *zone;
        struct zoneref *z;

        if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
                return false;

        /*
         * There are setups with compaction disabled which would prefer to loop
         * inside the allocator rather than hit the oom killer prematurely.
         * Let's give them a good hope and keep retrying while the order-0
         * watermarks are OK.
         */
        for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                                ac->highest_zoneidx, ac->nodemask) {
                if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
                                        ac->highest_zoneidx, alloc_flags))
                        return true;
        }
        return false;
}
#endif /* CONFIG_COMPACTION */

#ifdef CONFIG_LOCKDEP
static struct lockdep_map __fs_reclaim_map =
        STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);

static bool __need_reclaim(gfp_t gfp_mask)
{
        /* no reclaim without waiting on it */
        if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
                return false;

        /* this guy won't enter reclaim */
        if (current->flags & PF_MEMALLOC)
                return false;

        if (gfp_mask & __GFP_NOLOCKDEP)
                return false;

        return true;
}

void __fs_reclaim_acquire(unsigned long ip)
{
        lock_acquire_exclusive(&__fs_reclaim_map, 0, 0, NULL, ip);
}

void __fs_reclaim_release(unsigned long ip)
{
        lock_release(&__fs_reclaim_map, ip);
}

void fs_reclaim_acquire(gfp_t gfp_mask)
{
        gfp_mask = current_gfp_context(gfp_mask);

        if (__need_reclaim(gfp_mask)) {
                if (gfp_mask & __GFP_FS)
                        __fs_reclaim_acquire(_RET_IP_);

#ifdef CONFIG_MMU_NOTIFIER
                lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
                lock_map_release(&__mmu_notifier_invalidate_range_start_map);
#endif

        }
}
EXPORT_SYMBOL_GPL(fs_reclaim_acquire);

void fs_reclaim_release(gfp_t gfp_mask)
{
        gfp_mask = current_gfp_context(gfp_mask);

        if (__need_reclaim(gfp_mask)) {
                if (gfp_mask & __GFP_FS)
                        __fs_reclaim_release(_RET_IP_);
        }
}
EXPORT_SYMBOL_GPL(fs_reclaim_release);
#endif

/* Perform direct synchronous page reclaim */
static unsigned long
__perform_reclaim(gfp_t gfp_mask, unsigned int order,
                                        const struct alloc_context *ac)
{
        unsigned int noreclaim_flag;
        unsigned long pflags, progress;

        cond_resched();

        /* We now go into synchronous reclaim */
        cpuset_memory_pressure_bump();
        psi_memstall_enter(&pflags);
        fs_reclaim_acquire(gfp_mask);
        noreclaim_flag = memalloc_noreclaim_save();

        progress = try_to_free_pages(ac->zonelist, order, gfp_mask,
                                                                ac->nodemask);

        memalloc_noreclaim_restore(noreclaim_flag);
        fs_reclaim_release(gfp_mask);
        psi_memstall_leave(&pflags);

        cond_resched();

        return progress;
}

/* The really slow allocator path where we enter direct reclaim */
static inline struct page *
__alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
                unsigned int alloc_flags, const struct alloc_context *ac,
                unsigned long *did_some_progress)
{
        struct page *page = NULL;
        bool drained = false;

        *did_some_progress = __perform_reclaim(gfp_mask, order, ac);
        if (unlikely(!(*did_some_progress)))
                return NULL;

retry:
        page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);

        /*
         * If an allocation failed after direct reclaim, it could be because
         * pages are pinned on the per-cpu lists or in high alloc reserves.
         * Shrink them and try again
         */
        if (!page && !drained) {
                unreserve_highatomic_pageblock(ac, false);
                drain_all_pages(NULL);
                drained = true;
                goto retry;
        }

        return page;
}

static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,
                             const struct alloc_context *ac)
{
        struct zoneref *z;
        struct zone *zone;
        pg_data_t *last_pgdat = NULL;
        enum zone_type highest_zoneidx = ac->highest_zoneidx;

        for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, highest_zoneidx,
                                        ac->nodemask) {
                if (last_pgdat != zone->zone_pgdat)
                        wakeup_kswapd(zone, gfp_mask, order, highest_zoneidx);
                last_pgdat = zone->zone_pgdat;
        }
}

static inline unsigned int
gfp_to_alloc_flags(gfp_t gfp_mask)
{
        unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;

        /*
         * __GFP_HIGH is assumed to be the same as ALLOC_HIGH
         * and __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
         * to save two branches.
         */
        BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_HIGH);
        BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);

        /*
         * The caller may dip into page reserves a bit more if the caller
         * cannot run direct reclaim, or if the caller has realtime scheduling
         * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
         * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_HIGH (__GFP_HIGH).
         */
        alloc_flags |= (__force int)
                (gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));

        if (gfp_mask & __GFP_ATOMIC) {
                /*
                 * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
                 * if it can't schedule.
                 */
                if (!(gfp_mask & __GFP_NOMEMALLOC))
                        alloc_flags |= ALLOC_HARDER;
                /*
                 * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the
                 * comment for __cpuset_node_allowed().
                 */
                alloc_flags &= ~ALLOC_CPUSET;
        } else if (unlikely(rt_task(current)) && in_task())
                alloc_flags |= ALLOC_HARDER;

        alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, alloc_flags);

        return alloc_flags;
}

static bool oom_reserves_allowed(struct task_struct *tsk)
{
        if (!tsk_is_oom_victim(tsk))
                return false;

        /*
         * !MMU doesn't have oom reaper so give access to memory reserves
         * only to the thread with TIF_MEMDIE set
         */
        if (!IS_ENABLED(CONFIG_MMU) && !test_thread_flag(TIF_MEMDIE))
                return false;

        return true;
}

/*
 * Distinguish requests which really need access to full memory
 * reserves from oom victims which can live with a portion of it
 */
static inline int __gfp_pfmemalloc_flags(gfp_t gfp_mask)
{
        if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
                return 0;
        if (gfp_mask & __GFP_MEMALLOC)
                return ALLOC_NO_WATERMARKS;
        if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
                return ALLOC_NO_WATERMARKS;
        if (!in_interrupt()) {
                if (current->flags & PF_MEMALLOC)
                        return ALLOC_NO_WATERMARKS;
                else if (oom_reserves_allowed(current))
                        return ALLOC_OOM;
        }

        return 0;
}

bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
{
        return !!__gfp_pfmemalloc_flags(gfp_mask);
}

/*
 * Checks whether it makes sense to retry the reclaim to make a forward progress
 * for the given allocation request.
 *
 * We give up when we either have tried MAX_RECLAIM_RETRIES in a row
 * without success, or when we couldn't even meet the watermark if we
 * reclaimed all remaining pages on the LRU lists.
 *
 * Returns true if a retry is viable or false to enter the oom path.
 */
static inline bool
should_reclaim_retry(gfp_t gfp_mask, unsigned order,
                     struct alloc_context *ac, int alloc_flags,
                     bool did_some_progress, int *no_progress_loops)
{
        struct zone *zone;
        struct zoneref *z;
        bool ret = false;

        /*
         * Costly allocations might have made a progress but this doesn't mean
         * their order will become available due to high fragmentation so
         * always increment the no progress counter for them
         */
        if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
                *no_progress_loops = 0;
        else
                (*no_progress_loops)++;

        /*
         * Make sure we converge to OOM if we cannot make any progress
         * several times in the row.
         */
        if (*no_progress_loops > MAX_RECLAIM_RETRIES) {
                /* Before OOM, exhaust highatomic_reserve */
                return unreserve_highatomic_pageblock(ac, true);
        }

        /*
         * Keep reclaiming pages while there is a chance this will lead
         * somewhere.  If none of the target zones can satisfy our allocation
         * request even if all reclaimable pages are considered then we are
         * screwed and have to go OOM.
         */
        for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                                ac->highest_zoneidx, ac->nodemask) {
                unsigned long available;
                unsigned long reclaimable;
                unsigned long min_wmark = min_wmark_pages(zone);
                bool wmark;

                available = reclaimable = zone_reclaimable_pages(zone);
                available += zone_page_state_snapshot(zone, NR_FREE_PAGES);

                /*
                 * Would the allocation succeed if we reclaimed all
                 * reclaimable pages?
                 */
                wmark = __zone_watermark_ok(zone, order, min_wmark,
                                ac->highest_zoneidx, alloc_flags, available);
                trace_reclaim_retry_zone(z, order, reclaimable,
                                available, min_wmark, *no_progress_loops, wmark);
                if (wmark) {
                        ret = true;
                        break;
                }
        }

        /*
         * Memory allocation/reclaim might be called from a WQ context and the
         * current implementation of the WQ concurrency control doesn't
         * recognize that a particular WQ is congested if the worker thread is
         * looping without ever sleeping. Therefore we have to do a short sleep
         * here rather than calling cond_resched().
         */
        if (current->flags & PF_WQ_WORKER)
                schedule_timeout_uninterruptible(1);
        else
                cond_resched();
        return ret;
}

static inline bool
check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)
{
        /*
         * It's possible that cpuset's mems_allowed and the nodemask from
         * mempolicy don't intersect. This should be normally dealt with by
         * policy_nodemask(), but it's possible to race with cpuset update in
         * such a way the check therein was true, and then it became false
         * before we got our cpuset_mems_cookie here.
         * This assumes that for all allocations, ac->nodemask can come only
         * from MPOL_BIND mempolicy (whose documented semantics is to be ignored
         * when it does not intersect with the cpuset restrictions) or the
         * caller can deal with a violated nodemask.
         */
        if (cpusets_enabled() && ac->nodemask &&
                        !cpuset_nodemask_valid_mems_allowed(ac->nodemask)) {
                ac->nodemask = NULL;
                return true;
        }

        /*
         * When updating a task's mems_allowed or mempolicy nodemask, it is
         * possible to race with parallel threads in such a way that our
         * allocation can fail while the mask is being updated. If we are about
         * to fail, check if the cpuset changed during allocation and if so,
         * retry.
         */
        if (read_mems_allowed_retry(cpuset_mems_cookie))
                return true;

        return false;
}

static inline struct page *
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
                                                struct alloc_context *ac)
{
        bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
        const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER;
        struct page *page = NULL;
        unsigned int alloc_flags;
        unsigned long did_some_progress;
        enum compact_priority compact_priority;
        enum compact_result compact_result;
        int compaction_retries;
        int no_progress_loops;
        unsigned int cpuset_mems_cookie;
        int reserve_flags;

        /*
         * We also sanity check to catch abuse of atomic reserves being used by
         * callers that are not in atomic context.
         */
        if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
                                (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
                gfp_mask &= ~__GFP_ATOMIC;

retry_cpuset:
        compaction_retries = 0;
        no_progress_loops = 0;
        compact_priority = DEF_COMPACT_PRIORITY;
        cpuset_mems_cookie = read_mems_allowed_begin();

        /*
         * The fast path uses conservative alloc_flags to succeed only until
         * kswapd needs to be woken up, and to avoid the cost of setting up
         * alloc_flags precisely. So we do that now.
         */
        alloc_flags = gfp_to_alloc_flags(gfp_mask);

        /*
         * We need to recalculate the starting point for the zonelist iterator
         * because we might have used different nodemask in the fast path, or
         * there was a cpuset modification and we are retrying - otherwise we
         * could end up iterating over non-eligible zones endlessly.
         */
        ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                        ac->highest_zoneidx, ac->nodemask);
        if (!ac->preferred_zoneref->zone)
                goto nopage;

        /*
         * Check for insane configurations where the cpuset doesn't contain
         * any suitable zone to satisfy the request - e.g. non-movable
         * GFP_HIGHUSER allocations from MOVABLE nodes only.
         */
        if (cpusets_insane_config() && (gfp_mask & __GFP_HARDWALL)) {
                struct zoneref *z = first_zones_zonelist(ac->zonelist,
                                        ac->highest_zoneidx,
                                        &cpuset_current_mems_allowed);
                if (!z->zone)
                        goto nopage;
        }

        if (alloc_flags & ALLOC_KSWAPD)
                wake_all_kswapds(order, gfp_mask, ac);

        /*
         * The adjusted alloc_flags might result in immediate success, so try
         * that first
         */
        page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
        if (page)
                goto got_pg;

        /*
         * For costly allocations, try direct compaction first, as it's likely
         * that we have enough base pages and don't need to reclaim. For non-
         * movable high-order allocations, do that as well, as compaction will
         * try prevent permanent fragmentation by migrating from blocks of the
         * same migratetype.
         * Don't try this for allocations that are allowed to ignore
         * watermarks, as the ALLOC_NO_WATERMARKS attempt didn't yet happen.
         */
        if (can_direct_reclaim &&
                        (costly_order ||
                           (order > 0 && ac->migratetype != MIGRATE_MOVABLE))
                        && !gfp_pfmemalloc_allowed(gfp_mask)) {
                page = __alloc_pages_direct_compact(gfp_mask, order,
                                                alloc_flags, ac,
                                                INIT_COMPACT_PRIORITY,
                                                &compact_result);
                if (page)
                        goto got_pg;

                /*
                 * Checks for costly allocations with __GFP_NORETRY, which
                 * includes some THP page fault allocations
                 */
                if (costly_order && (gfp_mask & __GFP_NORETRY)) {
                        /*
                         * If allocating entire pageblock(s) and compaction
                         * failed because all zones are below low watermarks
                         * or is prohibited because it recently failed at this
                         * order, fail immediately unless the allocator has
                         * requested compaction and reclaim retry.
                         *
                         * Reclaim is
                         *  - potentially very expensive because zones are far
                         *    below their low watermarks or this is part of very
                         *    bursty high order allocations,
                         *  - not guaranteed to help because isolate_freepages()
                         *    may not iterate over freed pages as part of its
                         *    linear scan, and
                         *  - unlikely to make entire pageblocks free on its
                         *    own.
                         */
                        if (compact_result == COMPACT_SKIPPED ||
                            compact_result == COMPACT_DEFERRED)
                                goto nopage;

                        /*
                         * Looks like reclaim/compaction is worth trying, but
                         * sync compaction could be very expensive, so keep
                         * using async compaction.
                         */
                        compact_priority = INIT_COMPACT_PRIORITY;
                }
        }

retry:
        /* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
        if (alloc_flags & ALLOC_KSWAPD)
                wake_all_kswapds(order, gfp_mask, ac);

        reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
        if (reserve_flags)
                alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags);

        /*
         * Reset the nodemask and zonelist iterators if memory policies can be
         * ignored. These allocations are high priority and system rather than
         * user oriented.
         */
        if (!(alloc_flags & ALLOC_CPUSET) || reserve_flags) {
                ac->nodemask = NULL;
                ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                        ac->highest_zoneidx, ac->nodemask);
        }

        /* Attempt with potentially adjusted zonelist and alloc_flags */
        page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
        if (page)
                goto got_pg;

        /* Caller is not willing to reclaim, we can't balance anything */
        if (!can_direct_reclaim)
                goto nopage;

        /* Avoid recursion of direct reclaim */
        if (current->flags & PF_MEMALLOC)
                goto nopage;

        /* Try direct reclaim and then allocating */
        page = __alloc_pages_direct_reclaim(gfp_mask, order, alloc_flags, ac,
                                                        &did_some_progress);
        if (page)
                goto got_pg;

        /* Try direct compaction and then allocating */
        page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac,
                                        compact_priority, &compact_result);
        if (page)
                goto got_pg;

        /* Do not loop if specifically requested */
        if (gfp_mask & __GFP_NORETRY)
                goto nopage;

        /*
         * Do not retry costly high order allocations unless they are
         * __GFP_RETRY_MAYFAIL
         */
        if (costly_order && !(gfp_mask & __GFP_RETRY_MAYFAIL))
                goto nopage;

        if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
                                 did_some_progress > 0, &no_progress_loops))
                goto retry;

        /*
         * It doesn't make any sense to retry for the compaction if the order-0
         * reclaim is not able to make any progress because the current
         * implementation of the compaction depends on the sufficient amount
         * of free memory (see __compaction_suitable)
         */
        if (did_some_progress > 0 &&
                        should_compact_retry(ac, order, alloc_flags,
                                compact_result, &compact_priority,
                                &compaction_retries))
                goto retry;


        /* Deal with possible cpuset update races before we start OOM killing */
        if (check_retry_cpuset(cpuset_mems_cookie, ac))
                goto retry_cpuset;

        /* Reclaim has failed us, start killing things */
        page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
        if (page)
                goto got_pg;

        /* Avoid allocations with no watermarks from looping endlessly */
        if (tsk_is_oom_victim(current) &&
            (alloc_flags & ALLOC_OOM ||
             (gfp_mask & __GFP_NOMEMALLOC)))
                goto nopage;

        /* Retry as long as the OOM killer is making progress */
        if (did_some_progress) {
                no_progress_loops = 0;
                goto retry;
        }

nopage:
        /* Deal with possible cpuset update races before we fail */
        if (check_retry_cpuset(cpuset_mems_cookie, ac))
                goto retry_cpuset;

        /*
         * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
         * we always retry
         */
        if (gfp_mask & __GFP_NOFAIL) {
                /*
                 * All existing users of the __GFP_NOFAIL are blockable, so warn
                 * of any new users that actually require GFP_NOWAIT
                 */
                if (WARN_ON_ONCE(!can_direct_reclaim))
                        goto fail;

                /*
                 * PF_MEMALLOC request from this context is rather bizarre
                 * because we cannot reclaim anything and only can loop waiting
                 * for somebody to do a work for us
                 */
                WARN_ON_ONCE(current->flags & PF_MEMALLOC);

                /*
                 * non failing costly orders are a hard requirement which we
                 * are not prepared for much so let's warn about these users
                 * so that we can identify them and convert them to something
                 * else.
                 */
                WARN_ON_ONCE(order > PAGE_ALLOC_COSTLY_ORDER);

                /*
                 * Help non-failing allocations by giving them access to memory
                 * reserves but do not use ALLOC_NO_WATERMARKS because this
                 * could deplete whole memory reserves which would just make
                 * the situation worse
                 */
                page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_HARDER, ac);
                if (page)
                        goto got_pg;

                cond_resched();
                goto retry;
        }
fail:
        warn_alloc(gfp_mask, ac->nodemask,
                        "page allocation failure: order:%u", order);
got_pg:
        return page;
}

static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
                int preferred_nid, nodemask_t *nodemask,
                struct alloc_context *ac, gfp_t *alloc_gfp,
                unsigned int *alloc_flags)
{
        ac->highest_zoneidx = gfp_zone(gfp_mask);
        ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
        ac->nodemask = nodemask;
        ac->migratetype = gfp_migratetype(gfp_mask);

        if (cpusets_enabled()) {
                *alloc_gfp |= __GFP_HARDWALL;
                /*
                 * When we are in the interrupt context, it is irrelevant
                 * to the current task context. It means that any node ok.
                 */
                if (in_task() && !ac->nodemask)
                        ac->nodemask = &cpuset_current_mems_allowed;
                else
                        *alloc_flags |= ALLOC_CPUSET;
        }

        fs_reclaim_acquire(gfp_mask);
        fs_reclaim_release(gfp_mask);

        might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);

        if (should_fail_alloc_page(gfp_mask, order))
                return false;

        *alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, *alloc_flags);

        /* Dirty zone balancing only done in the fast path */
        ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);

        /*
         * The preferred zone is used for statistics but crucially it is
         * also used as the starting point for the zonelist iterator. It
         * may get reset for allocations that ignore memory policies.
         */
        ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                        ac->highest_zoneidx, ac->nodemask);

        return true;
}

/*
 * __alloc_pages_bulk - Allocate a number of order-0 pages to a list or array
 * @gfp: GFP flags for the allocation
 * @preferred_nid: The preferred NUMA node ID to allocate from
 * @nodemask: Set of nodes to allocate from, may be NULL
 * @nr_pages: The number of pages desired on the list or array
 * @page_list: Optional list to store the allocated pages
 * @page_array: Optional array to store the pages
 *
 * This is a batched version of the page allocator that attempts to
 * allocate nr_pages quickly. Pages are added to page_list if page_list
 * is not NULL, otherwise it is assumed that the page_array is valid.
 *
 * For lists, nr_pages is the number of pages that should be allocated.
 *
 * For arrays, only NULL elements are populated with pages and nr_pages
 * is the maximum number of pages that will be stored in the array.
 *
 * Returns the number of pages on the list or array.
 */
unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
                        nodemask_t *nodemask, int nr_pages,
                        struct list_head *page_list,
                        struct page **page_array)
{
        struct page *page;
        unsigned long flags;
        struct zone *zone;
        struct zoneref *z;
        struct per_cpu_pages *pcp;
        struct list_head *pcp_list;
        struct alloc_context ac;
        gfp_t alloc_gfp;
        unsigned int alloc_flags = ALLOC_WMARK_LOW;
        int nr_populated = 0, nr_account = 0;

        /*
         * Skip populated array elements to determine if any pages need
         * to be allocated before disabling IRQs.
         */
        while (page_array && nr_populated < nr_pages && page_array[nr_populated])
                nr_populated++;

        /* No pages requested? */
        if (unlikely(nr_pages <= 0))
                goto out;

        /* Already populated array? */
        if (unlikely(page_array && nr_pages - nr_populated == 0))
                goto out;

        /* Bulk allocator does not support memcg accounting. */
        if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT))
                goto failed;

        /* Use the single page allocator for one page. */
        if (nr_pages - nr_populated == 1)
                goto failed;

#ifdef CONFIG_PAGE_OWNER
        /*
         * PAGE_OWNER may recurse into the allocator to allocate space to
         * save the stack with pagesets.lock held. Releasing/reacquiring
         * removes much of the performance benefit of bulk allocation so
         * force the caller to allocate one page at a time as it'll have
         * similar performance to added complexity to the bulk allocator.
         */
        if (static_branch_unlikely(&page_owner_inited))
                goto failed;
#endif

        /* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
        gfp &= gfp_allowed_mask;
        alloc_gfp = gfp;
        if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags))
                goto out;
        gfp = alloc_gfp;

        /* Find an allowed local zone that meets the low watermark. */
        for_each_zone_zonelist_nodemask(zone, z, ac.zonelist, ac.highest_zoneidx, ac.nodemask) {
                unsigned long mark;

                if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
                    !__cpuset_zone_allowed(zone, gfp)) {
                        continue;
                }

                if (nr_online_nodes > 1 && zone != ac.preferred_zoneref->zone &&
                    zone_to_nid(zone) != zone_to_nid(ac.preferred_zoneref->zone)) {
                        goto failed;
                }

                mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages;
                if (zone_watermark_fast(zone, 0,  mark,
                                zonelist_zone_idx(ac.preferred_zoneref),
                                alloc_flags, gfp)) {
                        break;
                }
        }

        /*
         * If there are no allowed local zones that meets the watermarks then
         * try to allocate a single page and reclaim if necessary.
         */
        if (unlikely(!zone))
                goto failed;

        /* Attempt the batch allocation */
        local_lock_irqsave(&pagesets.lock, flags);
        pcp = this_cpu_ptr(zone->per_cpu_pageset);
        pcp_list = &pcp->lists[order_to_pindex(ac.migratetype, 0)];

        while (nr_populated < nr_pages) {

                /* Skip existing pages */
                if (page_array && page_array[nr_populated]) {
                        nr_populated++;
                        continue;
                }

                page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
                                                                pcp, pcp_list);
                if (unlikely(!page)) {
                        /* Try and get at least one page */
                        if (!nr_populated)
                                goto failed_irq;
                        break;
                }
                nr_account++;

                prep_new_page(page, 0, gfp, 0);
                if (page_list)
                        list_add(&page->lru, page_list);
                else
                        page_array[nr_populated] = page;
                nr_populated++;
        }

        local_unlock_irqrestore(&pagesets.lock, flags);

        __count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
        zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);

out:
        return nr_populated;

failed_irq:
        local_unlock_irqrestore(&pagesets.lock, flags);

failed:
        page = __alloc_pages(gfp, 0, preferred_nid, nodemask);
        if (page) {
                if (page_list)
                        list_add(&page->lru, page_list);
                else
                        page_array[nr_populated] = page;
                nr_populated++;
        }

        goto out;
}
EXPORT_SYMBOL_GPL(__alloc_pages_bulk);

/*
 * This is the 'heart' of the zoned buddy allocator.
 */
struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
                                                        nodemask_t *nodemask)
{
        struct page *page;
        unsigned int alloc_flags = ALLOC_WMARK_LOW;
        gfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */
        struct alloc_context ac = { };

        /*
         * There are several places where we assume that the order value is sane
         * so bail out early if the request is out of bound.
         */
        if (unlikely(order >= MAX_ORDER)) {
                WARN_ON_ONCE(!(gfp & __GFP_NOWARN));
                return NULL;
        }

        gfp &= gfp_allowed_mask;
        /*
         * Apply scoped allocation constraints. This is mainly about GFP_NOFS
         * resp. GFP_NOIO which has to be inherited for all allocation requests
         * from a particular context which has been marked by
         * memalloc_no{fs,io}_{save,restore}. And PF_MEMALLOC_PIN which ensures
         * movable zones are not used during allocation.
         */
        gfp = current_gfp_context(gfp);
        alloc_gfp = gfp;
        if (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, &ac,
                        &alloc_gfp, &alloc_flags))
                return NULL;

        /*
         * Forbid the first pass from falling back to types that fragment
         * memory until all local zones are considered.
         */
        alloc_flags |= alloc_flags_nofragment(ac.preferred_zoneref->zone, gfp);

        /* First allocation attempt */
        page = get_page_from_freelist(alloc_gfp, order, alloc_flags, &ac);
        if (likely(page))
                goto out;

        alloc_gfp = gfp;
        ac.spread_dirty_pages = false;

        /*
         * Restore the original nodemask if it was potentially replaced with
         * &cpuset_current_mems_allowed to optimize the fast-path attempt.
         */
        ac.nodemask = nodemask;

        page = __alloc_pages_slowpath(alloc_gfp, order, &ac);

out:
        if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT) && page &&
            unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {
                __free_pages(page, order);
                page = NULL;
        }

        trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);

        return page;
}
EXPORT_SYMBOL(__alloc_pages);

struct folio *__folio_alloc(gfp_t gfp, unsigned int order, int preferred_nid,
                nodemask_t *nodemask)
{
        struct page *page = __alloc_pages(gfp | __GFP_COMP, order,
                        preferred_nid, nodemask);

        if (page && order > 1)
                prep_transhuge_page(page);
        return (struct folio *)page;
}
EXPORT_SYMBOL(__folio_alloc);

/*
 * Common helper functions. Never use with __GFP_HIGHMEM because the returned
 * address cannot represent highmem pages. Use alloc_pages and then kmap if
 * you need to access high mem.
 */
unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
{
        struct page *page;

        page = alloc_pages(gfp_mask & ~__GFP_HIGHMEM, order);
        if (!page)
                return 0;
        return (unsigned long) page_address(page);
}
EXPORT_SYMBOL(__get_free_pages);

unsigned long get_zeroed_page(gfp_t gfp_mask)
{
        return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
}
EXPORT_SYMBOL(get_zeroed_page);

/**
 * __free_pages - Free pages allocated with alloc_pages().
 * @page: The page pointer returned from alloc_pages().
 * @order: The order of the allocation.
 *
 * This function can free multi-page allocations that are not compound
 * pages.  It does not check that the @order passed in matches that of
 * the allocation, so it is easy to leak memory.  Freeing more memory
 * than was allocated will probably emit a warning.
 *
 * If the last reference to this page is speculative, it will be released
 * by put_page() which only frees the first page of a non-compound
 * allocation.  To prevent the remaining pages from being leaked, we free
 * the subsequent pages here.  If you want to use the page's reference
 * count to decide when to free the allocation, you should allocate a
 * compound page, and use put_page() instead of __free_pages().
 *
 * Context: May be called in interrupt context or while holding a normal
 * spinlock, but not in NMI context or while holding a raw spinlock.
 */
void __free_pages(struct page *page, unsigned int order)
{
        if (put_page_testzero(page))
                free_the_page(page, order);
        else if (!PageHead(page))
                while (order-- > 0)
                        free_the_page(page + (1 << order), order);
}
EXPORT_SYMBOL(__free_pages);

void free_pages(unsigned long addr, unsigned int order)
{
        if (addr != 0) {
                VM_BUG_ON(!virt_addr_valid((void *)addr));
                __free_pages(virt_to_page((void *)addr), order);
        }
}

EXPORT_SYMBOL(free_pages);

/*
 * Page Fragment:
 *  An arbitrary-length arbitrary-offset area of memory which resides
 *  within a 0 or higher order page.  Multiple fragments within that page
 *  are individually refcounted, in the page's reference counter.
 *
 * The page_frag functions below provide a simple allocation framework for
 * page fragments.  This is used by the network stack and network device
 * drivers to provide a backing region of memory for use as either an
 * sk_buff->head, or to be used in the "frags" portion of skb_shared_info.
 */
static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
                                             gfp_t gfp_mask)
{
        struct page *page = NULL;
        gfp_t gfp = gfp_mask;

#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
        gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
                    __GFP_NOMEMALLOC;
        page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
                                PAGE_FRAG_CACHE_MAX_ORDER);
        nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
#endif
        if (unlikely(!page))
                page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);

        nc->va = page ? page_address(page) : NULL;

        return page;
}

void __page_frag_cache_drain(struct page *page, unsigned int count)
{
        VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);

        if (page_ref_sub_and_test(page, count))
                free_the_page(page, compound_order(page));
}
EXPORT_SYMBOL(__page_frag_cache_drain);

void *page_frag_alloc_align(struct page_frag_cache *nc,
                      unsigned int fragsz, gfp_t gfp_mask,
                      unsigned int align_mask)
{
        unsigned int size = PAGE_SIZE;
        struct page *page;
        int offset;

        if (unlikely(!nc->va)) {
refill:
                page = __page_frag_cache_refill(nc, gfp_mask);
                if (!page)
                        return NULL;

#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
                /* if size can vary use size else just use PAGE_SIZE */
                size = nc->size;
#endif
                /* Even if we own the page, we do not use atomic_set().
                 * This would break get_page_unless_zero() users.
                 */
                page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);

                /* reset page count bias and offset to start of new frag */
                nc->pfmemalloc = page_is_pfmemalloc(page);
                nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
                nc->offset = size;
        }

        offset = nc->offset - fragsz;
        if (unlikely(offset < 0)) {
                page = virt_to_page(nc->va);

                if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
                        goto refill;

                if (unlikely(nc->pfmemalloc)) {
                        free_the_page(page, compound_order(page));
                        goto refill;
                }

#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
                /* if size can vary use size else just use PAGE_SIZE */
                size = nc->size;
#endif
                /* OK, page count is 0, we can safely set it */
                set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);

                /* reset page count bias and offset to start of new frag */
                nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
                offset = size - fragsz;
        }

        nc->pagecnt_bias--;
        offset &= align_mask;
        nc->offset = offset;

        return nc->va + offset;
}
EXPORT_SYMBOL(page_frag_alloc_align);

/*
 * Frees a page fragment allocated out of either a compound or order 0 page.
 */
void page_frag_free(void *addr)
{
        struct page *page = virt_to_head_page(addr);

        if (unlikely(put_page_testzero(page)))
                free_the_page(page, compound_order(page));
}
EXPORT_SYMBOL(page_frag_free);

static void *make_alloc_exact(unsigned long addr, unsigned int order,
                size_t size)
{
        if (addr) {
                unsigned long alloc_end = addr + (PAGE_SIZE << order);
                unsigned long used = addr + PAGE_ALIGN(size);

                split_page(virt_to_page((void *)addr), order);
                while (used < alloc_end) {
                        free_page(used);
                        used += PAGE_SIZE;
                }
        }
        return (void *)addr;
}

/**
 * alloc_pages_exact - allocate an exact number physically-contiguous pages.
 * @size: the number of bytes to allocate
 * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
 *
 * This function is similar to alloc_pages(), except that it allocates the
 * minimum number of pages to satisfy the request.  alloc_pages() can only
 * allocate memory in power-of-two pages.
 *
 * This function is also limited by MAX_ORDER.
 *
 * Memory allocated by this function must be released by free_pages_exact().
 *
 * Return: pointer to the allocated area or %NULL in case of error.
 */
void *alloc_pages_exact(size_t size, gfp_t gfp_mask)
{
        unsigned int order = get_order(size);
        unsigned long addr;

        if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
                gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);

        addr = __get_free_pages(gfp_mask, order);
        return make_alloc_exact(addr, order, size);
}
EXPORT_SYMBOL(alloc_pages_exact);

/**
 * alloc_pages_exact_nid - allocate an exact number of physically-contiguous
 *                         pages on a node.
 * @nid: the preferred node ID where memory should be allocated
 * @size: the number of bytes to allocate
 * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
 *
 * Like alloc_pages_exact(), but try to allocate on node nid first before falling
 * back.
 *
 * Return: pointer to the allocated area or %NULL in case of error.
 */
void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
{
        unsigned int order = get_order(size);
        struct page *p;

        if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
                gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);

        p = alloc_pages_node(nid, gfp_mask, order);
        if (!p)
                return NULL;
        return make_alloc_exact((unsigned long)page_address(p), order, size);
}

/**
 * free_pages_exact - release memory allocated via alloc_pages_exact()
 * @virt: the value returned by alloc_pages_exact.
 * @size: size of allocation, same value as passed to alloc_pages_exact().
 *
 * Release the memory allocated by a previous call to alloc_pages_exact.
 */
void free_pages_exact(void *virt, size_t size)
{
        unsigned long addr = (unsigned long)virt;
        unsigned long end = addr + PAGE_ALIGN(size);

        while (addr < end) {
                free_page(addr);
                addr += PAGE_SIZE;
        }
}
EXPORT_SYMBOL(free_pages_exact);

/**
 * nr_free_zone_pages - count number of pages beyond high watermark
 * @offset: The zone index of the highest zone
 *
 * nr_free_zone_pages() counts the number of pages which are beyond the
 * high watermark within all zones at or below a given zone index.  For each
 * zone, the number of pages is calculated as:
 *
 *     nr_free_zone_pages = managed_pages - high_pages
 *
 * Return: number of pages beyond high watermark.
 */
static unsigned long nr_free_zone_pages(int offset)
{
        struct zoneref *z;
        struct zone *zone;

        /* Just pick one node, since fallback list is circular */
        unsigned long sum = 0;

        struct zonelist *zonelist = node_zonelist(numa_node_id(), GFP_KERNEL);

        for_each_zone_zonelist(zone, z, zonelist, offset) {
                unsigned long size = zone_managed_pages(zone);
                unsigned long high = high_wmark_pages(zone);
                if (size > high)
                        sum += size - high;
        }

        return sum;
}

/**
 * nr_free_buffer_pages - count number of pages beyond high watermark
 *
 * nr_free_buffer_pages() counts the number of pages which are beyond the high
 * watermark within ZONE_DMA and ZONE_NORMAL.
 *
 * Return: number of pages beyond high watermark within ZONE_DMA and
 * ZONE_NORMAL.
 */
unsigned long nr_free_buffer_pages(void)
{
        return nr_free_zone_pages(gfp_zone(GFP_USER));
}
EXPORT_SYMBOL_GPL(nr_free_buffer_pages);

static inline void show_node(struct zone *zone)
{
        if (IS_ENABLED(CONFIG_NUMA))
                printk("Node %d ", zone_to_nid(zone));
}

long si_mem_available(void)
{
        long available;
        unsigned long pagecache;
        unsigned long wmark_low = 0;
        unsigned long pages[NR_LRU_LISTS];
        unsigned long reclaimable;
        struct zone *zone;
        int lru;

        for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
                pages[lru] = global_node_page_state(NR_LRU_BASE + lru);

        for_each_zone(zone)
                wmark_low += low_wmark_pages(zone);

        /*
         * Estimate the amount of memory available for userspace allocations,
         * without causing swapping.
         */
        available = global_zone_page_state(NR_FREE_PAGES) - totalreserve_pages;

        /*
         * Not all the page cache can be freed, otherwise the system will
         * start swapping. Assume at least half of the page cache, or the
         * low watermark worth of cache, needs to stay.
         */
        pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
        pagecache -= min(pagecache / 2, wmark_low);
        available += pagecache;

        /*
         * Part of the reclaimable slab and other kernel memory consists of
         * items that are in use, and cannot be freed. Cap this estimate at the
         * low watermark.
         */
        reclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B) +
                global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE);
        available += reclaimable - min(reclaimable / 2, wmark_low);

        if (available < 0)
                available = 0;
        return available;
}
EXPORT_SYMBOL_GPL(si_mem_available);

void si_meminfo(struct sysinfo *val)
{
        val->totalram = totalram_pages();
        val->sharedram = global_node_page_state(NR_SHMEM);
        val->freeram = global_zone_page_state(NR_FREE_PAGES);
        val->bufferram = nr_blockdev_pages();
        val->totalhigh = totalhigh_pages();
        val->freehigh = nr_free_highpages();
        val->mem_unit = PAGE_SIZE;
}

EXPORT_SYMBOL(si_meminfo);

#ifdef CONFIG_NUMA
void si_meminfo_node(struct sysinfo *val, int nid)
{
        int zone_type;          /* needs to be signed */
        unsigned long managed_pages = 0;
        unsigned long managed_highpages = 0;
        unsigned long free_highpages = 0;
        pg_data_t *pgdat = NODE_DATA(nid);

        for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++)
                managed_pages += zone_managed_pages(&pgdat->node_zones[zone_type]);
        val->totalram = managed_pages;
        val->sharedram = node_page_state(pgdat, NR_SHMEM);
        val->freeram = sum_zone_node_page_state(nid, NR_FREE_PAGES);
#ifdef CONFIG_HIGHMEM
        for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
                struct zone *zone = &pgdat->node_zones[zone_type];

                if (is_highmem(zone)) {
                        managed_highpages += zone_managed_pages(zone);
                        free_highpages += zone_page_state(zone, NR_FREE_PAGES);
                }
        }
        val->totalhigh = managed_highpages;
        val->freehigh = free_highpages;
#else
        val->totalhigh = managed_highpages;
        val->freehigh = free_highpages;
#endif
        val->mem_unit = PAGE_SIZE;
}
#endif

/*
 * Determine whether the node should be displayed or not, depending on whether
 * SHOW_MEM_FILTER_NODES was passed to show_free_areas().
 */
static bool show_mem_node_skip(unsigned int flags, int nid, nodemask_t *nodemask)
{
        if (!(flags & SHOW_MEM_FILTER_NODES))
                return false;

        /*
         * no node mask - aka implicit memory numa policy. Do not bother with
         * the synchronization - read_mems_allowed_begin - because we do not
         * have to be precise here.
         */
        if (!nodemask)
                nodemask = &cpuset_current_mems_allowed;

        return !node_isset(nid, *nodemask);
}

#define K(x) ((x) << (PAGE_SHIFT-10))

static void show_migration_types(unsigned char type)
{
        static const char types[MIGRATE_TYPES] = {
                [MIGRATE_UNMOVABLE]     = 'U',
                [MIGRATE_MOVABLE]       = 'M',
                [MIGRATE_RECLAIMABLE]   = 'E',
                [MIGRATE_HIGHATOMIC]    = 'H',
#ifdef CONFIG_CMA
                [MIGRATE_CMA]           = 'C',
#endif
#ifdef CONFIG_MEMORY_ISOLATION
                [MIGRATE_ISOLATE]       = 'I',
#endif
        };
        char tmp[MIGRATE_TYPES + 1];
        char *p = tmp;
        int i;

        for (i = 0; i < MIGRATE_TYPES; i++) {
                if (type & (1 << i))
                        *p++ = types[i];
        }

        *p = '\0';
        printk(KERN_CONT "(%s) ", tmp);
}

/*
 * Show free area list (used inside shift_scroll-lock stuff)
 * We also calculate the percentage fragmentation. We do this by counting the
 * memory on each free list with the exception of the first item on the list.
 *
 * Bits in @filter:
 * SHOW_MEM_FILTER_NODES: suppress nodes that are not allowed by current's
 *   cpuset.
 */
void show_free_areas(unsigned int filter, nodemask_t *nodemask)
{
        unsigned long free_pcp = 0;
        int cpu;
        struct zone *zone;
        pg_data_t *pgdat;

        for_each_populated_zone(zone) {
                if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
                        continue;

                for_each_online_cpu(cpu)
                        free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
        }

        printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
                " active_file:%lu inactive_file:%lu isolated_file:%lu\n"
                " unevictable:%lu dirty:%lu writeback:%lu\n"
                " slab_reclaimable:%lu slab_unreclaimable:%lu\n"
                " mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
                " kernel_misc_reclaimable:%lu\n"
                " free:%lu free_pcp:%lu free_cma:%lu\n",
                global_node_page_state(NR_ACTIVE_ANON),
                global_node_page_state(NR_INACTIVE_ANON),
                global_node_page_state(NR_ISOLATED_ANON),
                global_node_page_state(NR_ACTIVE_FILE),
                global_node_page_state(NR_INACTIVE_FILE),
                global_node_page_state(NR_ISOLATED_FILE),
                global_node_page_state(NR_UNEVICTABLE),
                global_node_page_state(NR_FILE_DIRTY),
                global_node_page_state(NR_WRITEBACK),
                global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B),
                global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B),
                global_node_page_state(NR_FILE_MAPPED),
                global_node_page_state(NR_SHMEM),
                global_node_page_state(NR_PAGETABLE),
                global_zone_page_state(NR_BOUNCE),
                global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE),
                global_zone_page_state(NR_FREE_PAGES),
                free_pcp,
                global_zone_page_state(NR_FREE_CMA_PAGES));

        for_each_online_pgdat(pgdat) {
                if (show_mem_node_skip(filter, pgdat->node_id, nodemask))
                        continue;

                printk("Node %d"
                        " active_anon:%lukB"
                        " inactive_anon:%lukB"
                        " active_file:%lukB"
                        " inactive_file:%lukB"
                        " unevictable:%lukB"
                        " isolated(anon):%lukB"
                        " isolated(file):%lukB"
                        " mapped:%lukB"
                        " dirty:%lukB"
                        " writeback:%lukB"
                        " shmem:%lukB"
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
                        " shmem_thp: %lukB"
                        " shmem_pmdmapped: %lukB"
                        " anon_thp: %lukB"
#endif
                        " writeback_tmp:%lukB"
                        " kernel_stack:%lukB"
#ifdef CONFIG_SHADOW_CALL_STACK
                        " shadow_call_stack:%lukB"
#endif
                        " pagetables:%lukB"
                        " all_unreclaimable? %s"
                        "\n",
                        pgdat->node_id,
                        K(node_page_state(pgdat, NR_ACTIVE_ANON)),
                        K(node_page_state(pgdat, NR_INACTIVE_ANON)),
                        K(node_page_state(pgdat, NR_ACTIVE_FILE)),
                        K(node_page_state(pgdat, NR_INACTIVE_FILE)),
                        K(node_page_state(pgdat, NR_UNEVICTABLE)),
                        K(node_page_state(pgdat, NR_ISOLATED_ANON)),
                        K(node_page_state(pgdat, NR_ISOLATED_FILE)),
                        K(node_page_state(pgdat, NR_FILE_MAPPED)),
                        K(node_page_state(pgdat, NR_FILE_DIRTY)),
                        K(node_page_state(pgdat, NR_WRITEBACK)),
                        K(node_page_state(pgdat, NR_SHMEM)),
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
                        K(node_page_state(pgdat, NR_SHMEM_THPS)),
                        K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)),
                        K(node_page_state(pgdat, NR_ANON_THPS)),
#endif
                        K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
                        node_page_state(pgdat, NR_KERNEL_STACK_KB),
#ifdef CONFIG_SHADOW_CALL_STACK
                        node_page_state(pgdat, NR_KERNEL_SCS_KB),
#endif
                        K(node_page_state(pgdat, NR_PAGETABLE)),
                        pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
                                "yes" : "no");
        }

        for_each_populated_zone(zone) {
                int i;

                if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
                        continue;

                free_pcp = 0;
                for_each_online_cpu(cpu)
                        free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;

                show_node(zone);
                printk(KERN_CONT
                        "%s"
                        " free:%lukB"
                        " boost:%lukB"
                        " min:%lukB"
                        " low:%lukB"
                        " high:%lukB"
                        " reserved_highatomic:%luKB"
                        " active_anon:%lukB"
                        " inactive_anon:%lukB"
                        " active_file:%lukB"
                        " inactive_file:%lukB"
                        " unevictable:%lukB"
                        " writepending:%lukB"
                        " present:%lukB"
                        " managed:%lukB"
                        " mlocked:%lukB"
                        " bounce:%lukB"
                        " free_pcp:%lukB"
                        " local_pcp:%ukB"
                        " free_cma:%lukB"
                        "\n",
                        zone->name,
                        K(zone_page_state(zone, NR_FREE_PAGES)),
                        K(zone->watermark_boost),
                        K(min_wmark_pages(zone)),
                        K(low_wmark_pages(zone)),
                        K(high_wmark_pages(zone)),
                        K(zone->nr_reserved_highatomic),
                        K(zone_page_state(zone, NR_ZONE_ACTIVE_ANON)),
                        K(zone_page_state(zone, NR_ZONE_INACTIVE_ANON)),
                        K(zone_page_state(zone, NR_ZONE_ACTIVE_FILE)),
                        K(zone_page_state(zone, NR_ZONE_INACTIVE_FILE)),
                        K(zone_page_state(zone, NR_ZONE_UNEVICTABLE)),
                        K(zone_page_state(zone, NR_ZONE_WRITE_PENDING)),
                        K(zone->present_pages),
                        K(zone_managed_pages(zone)),
                        K(zone_page_state(zone, NR_MLOCK)),
                        K(zone_page_state(zone, NR_BOUNCE)),
                        K(free_pcp),
                        K(this_cpu_read(zone->per_cpu_pageset->count)),
                        K(zone_page_state(zone, NR_FREE_CMA_PAGES)));
                printk("lowmem_reserve[]:");
                for (i = 0; i < MAX_NR_ZONES; i++)
                        printk(KERN_CONT " %ld", zone->lowmem_reserve[i]);
                printk(KERN_CONT "\n");
        }

        for_each_populated_zone(zone) {
                unsigned int order;
                unsigned long nr[MAX_ORDER], flags, total = 0;
                unsigned char types[MAX_ORDER];

                if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
                        continue;
                show_node(zone);
                printk(KERN_CONT "%s: ", zone->name);

                spin_lock_irqsave(&zone->lock, flags);
                for (order = 0; order < MAX_ORDER; order++) {
                        struct free_area *area = &zone->free_area[order];
                        int type;

                        nr[order] = area->nr_free;
                        total += nr[order] << order;

                        types[order] = 0;
                        for (type = 0; type < MIGRATE_TYPES; type++) {
                                if (!free_area_empty(area, type))
                                        types[order] |= 1 << type;
                        }
                }
                spin_unlock_irqrestore(&zone->lock, flags);
                for (order = 0; order < MAX_ORDER; order++) {
                        printk(KERN_CONT "%lu*%lukB ",
                               nr[order], K(1UL) << order);
                        if (nr[order])
                                show_migration_types(types[order]);
                }
                printk(KERN_CONT "= %lukB\n", K(total));
        }

        hugetlb_show_meminfo();

        printk("%ld total pagecache pages\n", global_node_page_state(NR_FILE_PAGES));

        show_swap_cache_info();
}

static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
{
        zoneref->zone = zone;
        zoneref->zone_idx = zone_idx(zone);
}

/*
 * Builds allocation fallback zone lists.
 *
 * Add all populated zones of a node to the zonelist.
 */
static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)
{
        struct zone *zone;
        enum zone_type zone_type = MAX_NR_ZONES;
        int nr_zones = 0;

        do {
                zone_type--;
                zone = pgdat->node_zones + zone_type;
                if (managed_zone(zone)) {
                        zoneref_set_zone(zone, &zonerefs[nr_zones++]);
                        check_highest_zone(zone_type);
                }
        } while (zone_type);

        return nr_zones;
}

#ifdef CONFIG_NUMA

static int __parse_numa_zonelist_order(char *s)
{
        /*
         * We used to support different zonelists modes but they turned
         * out to be just not useful. Let's keep the warning in place
         * if somebody still use the cmd line parameter so that we do
         * not fail it silently
         */
        if (!(*s == 'd' || *s == 'D' || *s == 'n' || *s == 'N')) {
                pr_warn("Ignoring unsupported numa_zonelist_order value:  %s\n", s);
                return -EINVAL;
        }
        return 0;
}

char numa_zonelist_order[] = "Node";

/*
 * sysctl handler for numa_zonelist_order
 */
int numa_zonelist_order_handler(struct ctl_table *table, int write,
                void *buffer, size_t *length, loff_t *ppos)
{
        if (write)
                return __parse_numa_zonelist_order(buffer);
        return proc_dostring(table, write, buffer, length, ppos);
}


#define MAX_NODE_LOAD (nr_online_nodes)
static int node_load[MAX_NUMNODES];

/**
 * find_next_best_node - find the next node that should appear in a given node's fallback list
 * @node: node whose fallback list we're appending
 * @used_node_mask: nodemask_t of already used nodes
 *
 * We use a number of factors to determine which is the next node that should
 * appear on a given node's fallback list.  The node should not have appeared
 * already in @node's fallback list, and it should be the next closest node
 * according to the distance array (which contains arbitrary distance values
 * from each node to each node in the system), and should also prefer nodes
 * with no CPUs, since presumably they'll have very little allocation pressure
 * on them otherwise.
 *
 * Return: node id of the found node or %NUMA_NO_NODE if no node is found.
 */
int find_next_best_node(int node, nodemask_t *used_node_mask)
{
        int n, val;
        int min_val = INT_MAX;
        int best_node = NUMA_NO_NODE;

        /* Use the local node if we haven't already */
        if (!node_isset(node, *used_node_mask)) {
                node_set(node, *used_node_mask);
                return node;
        }

        for_each_node_state(n, N_MEMORY) {

                /* Don't want a node to appear more than once */
                if (node_isset(n, *used_node_mask))
                        continue;

                /* Use the distance array to find the distance */
                val = node_distance(node, n);

                /* Penalize nodes under us ("prefer the next node") */
                val += (n < node);

                /* Give preference to headless and unused nodes */
                if (!cpumask_empty(cpumask_of_node(n)))
                        val += PENALTY_FOR_NODE_WITH_CPUS;

                /* Slight preference for less loaded node */
                val *= (MAX_NODE_LOAD*MAX_NUMNODES);
                val += node_load[n];

                if (val < min_val) {
                        min_val = val;
                        best_node = n;
                }
        }

        if (best_node >= 0)
                node_set(best_node, *used_node_mask);

        return best_node;
}


/*
 * Build zonelists ordered by node and zones within node.
 * This results in maximum locality--normal zone overflows into local
 * DMA zone, if any--but risks exhausting DMA zone.
 */
static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
                unsigned nr_nodes)
{
        struct zoneref *zonerefs;
        int i;

        zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;

        for (i = 0; i < nr_nodes; i++) {
                int nr_zones;

                pg_data_t *node = NODE_DATA(node_order[i]);

                nr_zones = build_zonerefs_node(node, zonerefs);
                zonerefs += nr_zones;
        }
        zonerefs->zone = NULL;
        zonerefs->zone_idx = 0;
}

/*
 * Build gfp_thisnode zonelists
 */
static void build_thisnode_zonelists(pg_data_t *pgdat)
{
        struct zoneref *zonerefs;
        int nr_zones;

        zonerefs = pgdat->node_zonelists[ZONELIST_NOFALLBACK]._zonerefs;
        nr_zones = build_zonerefs_node(pgdat, zonerefs);
        zonerefs += nr_zones;
        zonerefs->zone = NULL;
        zonerefs->zone_idx = 0;
}

/*
 * Build zonelists ordered by zone and nodes within zones.
 * This results in conserving DMA zone[s] until all Normal memory is
 * exhausted, but results in overflowing to remote node while memory
 * may still exist in local DMA zone.
 */

static void build_zonelists(pg_data_t *pgdat)
{
        static int node_order[MAX_NUMNODES];
        int node, load, nr_nodes = 0;
        nodemask_t used_mask = NODE_MASK_NONE;
        int local_node, prev_node;

        /* NUMA-aware ordering of nodes */
        local_node = pgdat->node_id;
        load = nr_online_nodes;
        prev_node = local_node;

        memset(node_order, 0, sizeof(node_order));
        while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
                /*
                 * We don't want to pressure a particular node.
                 * So adding penalty to the first node in same
                 * distance group to make it round-robin.
                 */
                if (node_distance(local_node, node) !=
                    node_distance(local_node, prev_node))
                        node_load[node] += load;

                node_order[nr_nodes++] = node;
                prev_node = node;
                load--;
        }

        build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
        build_thisnode_zonelists(pgdat);
        pr_info("Fallback order for Node %d: ", local_node);
        for (node = 0; node < nr_nodes; node++)
                pr_cont("%d ", node_order[node]);
        pr_cont("\n");
}

#ifdef CONFIG_HAVE_MEMORYLESS_NODES
/*
 * Return node id of node used for "local" allocations.
 * I.e., first node id of first zone in arg node's generic zonelist.
 * Used for initializing percpu 'numa_mem', which is used primarily
 * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.
 */
int local_memory_node(int node)
{
        struct zoneref *z;

        z = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
                                   gfp_zone(GFP_KERNEL),
                                   NULL);
        return zone_to_nid(z->zone);
}
#endif

static void setup_min_unmapped_ratio(void);
static void setup_min_slab_ratio(void);
#else   /* CONFIG_NUMA */

static void build_zonelists(pg_data_t *pgdat)
{
        int node, local_node;
        struct zoneref *zonerefs;
        int nr_zones;

        local_node = pgdat->node_id;

        zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
        nr_zones = build_zonerefs_node(pgdat, zonerefs);
        zonerefs += nr_zones;

        /*
         * Now we build the zonelist so that it contains the zones
         * of all the other nodes.
         * We don't want to pressure a particular node, so when
         * building the zones for node N, we make sure that the
         * zones coming right after the local ones are those from
         * node N+1 (modulo N)
         */
        for (node = local_node + 1; node < MAX_NUMNODES; node++) {
                if (!node_online(node))
                        continue;
                nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
                zonerefs += nr_zones;
        }
        for (node = 0; node < local_node; node++) {
                if (!node_online(node))
                        continue;
                nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
                zonerefs += nr_zones;
        }

        zonerefs->zone = NULL;
        zonerefs->zone_idx = 0;
}

#endif  /* CONFIG_NUMA */

/*
 * Boot pageset table. One per cpu which is going to be used for all
 * zones and all nodes. The parameters will be set in such a way
 * that an item put on a list will immediately be handed over to
 * the buddy list. This is safe since pageset manipulation is done
 * with interrupts disabled.
 *
 * The boot_pagesets must be kept even after bootup is complete for
 * unused processors and/or zones. They do play a role for bootstrapping
 * hotplugged processors.
 *
 * zoneinfo_show() and maybe other functions do
 * not check if the processor is online before following the pageset pointer.
 * Other parts of the kernel may not check if the zone is available.
 */
static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats);
/* These effectively disable the pcplists in the boot pageset completely */
#define BOOT_PAGESET_HIGH       0
#define BOOT_PAGESET_BATCH      1
static DEFINE_PER_CPU(struct per_cpu_pages, boot_pageset);
static DEFINE_PER_CPU(struct per_cpu_zonestat, boot_zonestats);
static DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);

static void __build_all_zonelists(void *data)
{
        int nid;
        int __maybe_unused cpu;
        pg_data_t *self = data;
        static DEFINE_SPINLOCK(lock);

        spin_lock(&lock);

#ifdef CONFIG_NUMA
        memset(node_load, 0, sizeof(node_load));
#endif

        /*
         * This node is hotadded and no memory is yet present.   So just
         * building zonelists is fine - no need to touch other nodes.
         */
        if (self && !node_online(self->node_id)) {
                build_zonelists(self);
        } else {
                for_each_online_node(nid) {
                        pg_data_t *pgdat = NODE_DATA(nid);

                        build_zonelists(pgdat);
                }

#ifdef CONFIG_HAVE_MEMORYLESS_NODES
                /*
                 * We now know the "local memory node" for each node--
                 * i.e., the node of the first zone in the generic zonelist.
                 * Set up numa_mem percpu variable for on-line cpus.  During
                 * boot, only the boot cpu should be on-line;  we'll init the
                 * secondary cpus' numa_mem as they come on-line.  During
                 * node/memory hotplug, we'll fixup all on-line cpus.
                 */
                for_each_online_cpu(cpu)
                        set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
#endif
        }

        spin_unlock(&lock);
}

static noinline void __init
build_all_zonelists_init(void)
{
        int cpu;

        __build_all_zonelists(NULL);

        /*
         * Initialize the boot_pagesets that are going to be used
         * for bootstrapping processors. The real pagesets for
         * each zone will be allocated later when the per cpu
         * allocator is available.
         *
         * boot_pagesets are used also for bootstrapping offline
         * cpus if the system is already booted because the pagesets
         * are needed to initialize allocators on a specific cpu too.
         * F.e. the percpu allocator needs the page allocator which
         * needs the percpu allocator in order to allocate its pagesets
         * (a chicken-egg dilemma).
         */
        for_each_possible_cpu(cpu)
                per_cpu_pages_init(&per_cpu(boot_pageset, cpu), &per_cpu(boot_zonestats, cpu));

        mminit_verify_zonelist();
        cpuset_init_current_mems_allowed();
}

/*
 * unless system_state == SYSTEM_BOOTING.
 *
 * __ref due to call of __init annotated helper build_all_zonelists_init
 * [protected by SYSTEM_BOOTING].
 */
void __ref build_all_zonelists(pg_data_t *pgdat)
{
        unsigned long vm_total_pages;

        if (system_state == SYSTEM_BOOTING) {
                build_all_zonelists_init();
        } else {
                __build_all_zonelists(pgdat);
                /* cpuset refresh routine should be here */
        }
        /* Get the number of free pages beyond high watermark in all zones. */
        vm_total_pages = nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
        /*
         * Disable grouping by mobility if the number of pages in the
         * system is too low to allow the mechanism to work. It would be
         * more accurate, but expensive to check per-zone. This check is
         * made on memory-hotadd so a system can start with mobility
         * disabled and enable it later
         */
        if (vm_total_pages < (pageblock_nr_pages * MIGRATE_TYPES))
                page_group_by_mobility_disabled = 1;
        else
                page_group_by_mobility_disabled = 0;

        pr_info("Built %u zonelists, mobility grouping %s.  Total pages: %ld\n",
                nr_online_nodes,
                page_group_by_mobility_disabled ? "off" : "on",
                vm_total_pages);
#ifdef CONFIG_NUMA
        pr_info("Policy zone: %s\n", zone_names[policy_zone]);
#endif
}

/* If zone is ZONE_MOVABLE but memory is mirrored, it is an overlapped init */
static bool __meminit
overlap_memmap_init(unsigned long zone, unsigned long *pfn)
{
        static struct memblock_region *r;

        if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
                if (!r || *pfn >= memblock_region_memory_end_pfn(r)) {
                        for_each_mem_region(r) {
                                if (*pfn < memblock_region_memory_end_pfn(r))
                                        break;
                        }
                }
                if (*pfn >= memblock_region_memory_base_pfn(r) &&
                    memblock_is_mirror(r)) {
                        *pfn = memblock_region_memory_end_pfn(r);
                        return true;
                }
        }
        return false;
}

/*
 * Initially all pages are reserved - free ones are freed
 * up by memblock_free_all() once the early boot process is
 * done. Non-atomic initialization, single-pass.
 *
 * All aligned pageblocks are initialized to the specified migratetype
 * (usually MIGRATE_MOVABLE). Besides setting the migratetype, no related
 * zone stats (e.g., nr_isolate_pageblock) are touched.
 */
void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone,
                unsigned long start_pfn, unsigned long zone_end_pfn,
                enum meminit_context context,
                struct vmem_altmap *altmap, int migratetype)
{
        unsigned long pfn, end_pfn = start_pfn + size;
        struct page *page;

        if (highest_memmap_pfn < end_pfn - 1)
                highest_memmap_pfn = end_pfn - 1;

#ifdef CONFIG_ZONE_DEVICE
        /*
         * Honor reservation requested by the driver for this ZONE_DEVICE
         * memory. We limit the total number of pages to initialize to just
         * those that might contain the memory mapping. We will defer the
         * ZONE_DEVICE page initialization until after we have released
         * the hotplug lock.
         */
        if (zone == ZONE_DEVICE) {
                if (!altmap)
                        return;

                if (start_pfn == altmap->base_pfn)
                        start_pfn += altmap->reserve;
                end_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
        }
#endif

        for (pfn = start_pfn; pfn < end_pfn; ) {
                /*
                 * There can be holes in boot-time mem_map[]s handed to this
                 * function.  They do not exist on hotplugged memory.
                 */
                if (context == MEMINIT_EARLY) {
                        if (overlap_memmap_init(zone, &pfn))
                                continue;
                        if (defer_init(nid, pfn, zone_end_pfn))
                                break;
                }

                page = pfn_to_page(pfn);
                __init_single_page(page, pfn, zone, nid);
                if (context == MEMINIT_HOTPLUG)
                        __SetPageReserved(page);

                /*
                 * Usually, we want to mark the pageblock MIGRATE_MOVABLE,
                 * such that unmovable allocations won't be scattered all
                 * over the place during system boot.
                 */
                if (IS_ALIGNED(pfn, pageblock_nr_pages)) {
                        set_pageblock_migratetype(page, migratetype);
                        cond_resched();
                }
                pfn++;
        }
}

#ifdef CONFIG_ZONE_DEVICE
void __ref memmap_init_zone_device(struct zone *zone,
                                   unsigned long start_pfn,
                                   unsigned long nr_pages,
                                   struct dev_pagemap *pgmap)
{
        unsigned long pfn, end_pfn = start_pfn + nr_pages;
        struct pglist_data *pgdat = zone->zone_pgdat;
        struct vmem_altmap *altmap = pgmap_altmap(pgmap);
        unsigned long zone_idx = zone_idx(zone);
        unsigned long start = jiffies;
        int nid = pgdat->node_id;

        if (WARN_ON_ONCE(!pgmap || zone_idx(zone) != ZONE_DEVICE))
                return;

        /*
         * The call to memmap_init should have already taken care
         * of the pages reserved for the memmap, so we can just jump to
         * the end of that region and start processing the device pages.
         */
        if (altmap) {
                start_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
                nr_pages = end_pfn - start_pfn;
        }

        for (pfn = start_pfn; pfn < end_pfn; pfn++) {
                struct page *page = pfn_to_page(pfn);

                __init_single_page(page, pfn, zone_idx, nid);

                /*
                 * Mark page reserved as it will need to wait for onlining
                 * phase for it to be fully associated with a zone.
                 *
                 * We can use the non-atomic __set_bit operation for setting
                 * the flag as we are still initializing the pages.
                 */
                __SetPageReserved(page);

                /*
                 * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
                 * and zone_device_data.  It is a bug if a ZONE_DEVICE page is
                 * ever freed or placed on a driver-private list.
                 */
                page->pgmap = pgmap;
                page->zone_device_data = NULL;

                /*
                 * Mark the block movable so that blocks are reserved for
                 * movable at startup. This will force kernel allocations
                 * to reserve their blocks rather than leaking throughout
                 * the address space during boot when many long-lived
                 * kernel allocations are made.
                 *
                 * Please note that MEMINIT_HOTPLUG path doesn't clear memmap
                 * because this is done early in section_activate()
                 */
                if (IS_ALIGNED(pfn, pageblock_nr_pages)) {
                        set_pageblock_migratetype(page, MIGRATE_MOVABLE);
                        cond_resched();
                }
        }

        pr_info("%s initialised %lu pages in %ums\n", __func__,
                nr_pages, jiffies_to_msecs(jiffies - start));
}

#endif
static void __meminit zone_init_free_lists(struct zone *zone)
{
        unsigned int order, t;
        for_each_migratetype_order(order, t) {
                INIT_LIST_HEAD(&zone->free_area[order].free_list[t]);
                zone->free_area[order].nr_free = 0;
        }
}

/*
 * Only struct pages that correspond to ranges defined by memblock.memory
 * are zeroed and initialized by going through __init_single_page() during
 * memmap_init_zone_range().
 *
 * But, there could be struct pages that correspond to holes in
 * memblock.memory. This can happen because of the following reasons:
 * - physical memory bank size is not necessarily the exact multiple of the
 *   arbitrary section size
 * - early reserved memory may not be listed in memblock.memory
 * - memory layouts defined with memmap= kernel parameter may not align
 *   nicely with memmap sections
 *
 * Explicitly initialize those struct pages so that:
 * - PG_Reserved is set
 * - zone and node links point to zone and node that span the page if the
 *   hole is in the middle of a zone
 * - zone and node links point to adjacent zone/node if the hole falls on
 *   the zone boundary; the pages in such holes will be prepended to the
 *   zone/node above the hole except for the trailing pages in the last
 *   section that will be appended to the zone/node below.
 */
static void __init init_unavailable_range(unsigned long spfn,
                                          unsigned long epfn,
                                          int zone, int node)
{
        unsigned long pfn;
        u64 pgcnt = 0;

        for (pfn = spfn; pfn < epfn; pfn++) {
                if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) {
                        pfn = ALIGN_DOWN(pfn, pageblock_nr_pages)
                                + pageblock_nr_pages - 1;
                        continue;
                }
                __init_single_page(pfn_to_page(pfn), pfn, zone, node);
                __SetPageReserved(pfn_to_page(pfn));
                pgcnt++;
        }

        if (pgcnt)
                pr_info("On node %d, zone %s: %lld pages in unavailable ranges",
                        node, zone_names[zone], pgcnt);
}

static void __init memmap_init_zone_range(struct zone *zone,
                                          unsigned long start_pfn,
                                          unsigned long end_pfn,
                                          unsigned long *hole_pfn)
{
        unsigned long zone_start_pfn = zone->zone_start_pfn;
        unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages;
        int nid = zone_to_nid(zone), zone_id = zone_idx(zone);

        start_pfn = clamp(start_pfn, zone_start_pfn, zone_end_pfn);
        end_pfn = clamp(end_pfn, zone_start_pfn, zone_end_pfn);

        if (start_pfn >= end_pfn)
                return;

        memmap_init_range(end_pfn - start_pfn, nid, zone_id, start_pfn,
                          zone_end_pfn, MEMINIT_EARLY, NULL, MIGRATE_MOVABLE);

        if (*hole_pfn < start_pfn)
                init_unavailable_range(*hole_pfn, start_pfn, zone_id, nid);

        *hole_pfn = end_pfn;
}

static void __init memmap_init(void)
{
        unsigned long start_pfn, end_pfn;
        unsigned long hole_pfn = 0;
        int i, j, zone_id = 0, nid;

        for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
                struct pglist_data *node = NODE_DATA(nid);

                for (j = 0; j < MAX_NR_ZONES; j++) {
                        struct zone *zone = node->node_zones + j;

                        if (!populated_zone(zone))
                                continue;

                        memmap_init_zone_range(zone, start_pfn, end_pfn,
                                               &hole_pfn);
                        zone_id = j;
                }
        }

#ifdef CONFIG_SPARSEMEM
        /*
         * Initialize the memory map for hole in the range [memory_end,
         * section_end].
         * Append the pages in this hole to the highest zone in the last
         * node.
         * The call to init_unavailable_range() is outside the ifdef to
         * silence the compiler warining about zone_id set but not used;
         * for FLATMEM it is a nop anyway
         */
        end_pfn = round_up(end_pfn, PAGES_PER_SECTION);
        if (hole_pfn < end_pfn)
#endif
                init_unavailable_range(hole_pfn, end_pfn, zone_id, nid);
}

void __init *memmap_alloc(phys_addr_t size, phys_addr_t align,
                          phys_addr_t min_addr, int nid, bool exact_nid)
{
        void *ptr;

        if (exact_nid)
                ptr = memblock_alloc_exact_nid_raw(size, align, min_addr,
                                                   MEMBLOCK_ALLOC_ACCESSIBLE,
                                                   nid);
        else
                ptr = memblock_alloc_try_nid_raw(size, align, min_addr,
                                                 MEMBLOCK_ALLOC_ACCESSIBLE,
                                                 nid);

        if (ptr && size > 0)
                page_init_poison(ptr, size);

        return ptr;
}

static int zone_batchsize(struct zone *zone)
{
#ifdef CONFIG_MMU
        int batch;

        /*
         * The number of pages to batch allocate is either ~0.1%
         * of the zone or 1MB, whichever is smaller. The batch
         * size is striking a balance between allocation latency
         * and zone lock contention.
         */
        batch = min(zone_managed_pages(zone) >> 10, (1024 * 1024) / PAGE_SIZE);
        batch /= 4;             /* We effectively *= 4 below */
        if (batch < 1)
                batch = 1;

        /*
         * Clamp the batch to a 2^n - 1 value. Having a power
         * of 2 value was found to be more likely to have
         * suboptimal cache aliasing properties in some cases.
         *
         * For example if 2 tasks are alternately allocating
         * batches of pages, one task can end up with a lot
         * of pages of one half of the possible page colors
         * and the other with pages of the other colors.
         */
        batch = rounddown_pow_of_two(batch + batch/2) - 1;

        return batch;

#else
        /* The deferral and batching of frees should be suppressed under NOMMU
         * conditions.
         *
         * The problem is that NOMMU needs to be able to allocate large chunks
         * of contiguous memory as there's no hardware page translation to
         * assemble apparent contiguous memory from discontiguous pages.
         *
         * Queueing large contiguous runs of pages for batching, however,
         * causes the pages to actually be freed in smaller chunks.  As there
         * can be a significant delay between the individual batches being
         * recycled, this leads to the once large chunks of space being
         * fragmented and becoming unavailable for high-order allocations.
         */
        return 0;
#endif
}

static int zone_highsize(struct zone *zone, int batch, int cpu_online)
{
#ifdef CONFIG_MMU
        int high;
        int nr_split_cpus;
        unsigned long total_pages;

        if (!percpu_pagelist_high_fraction) {
                /*
                 * By default, the high value of the pcp is based on the zone
                 * low watermark so that if they are full then background
                 * reclaim will not be started prematurely.
                 */
                total_pages = low_wmark_pages(zone);
        } else {
                /*
                 * If percpu_pagelist_high_fraction is configured, the high
                 * value is based on a fraction of the managed pages in the
                 * zone.
                 */
                total_pages = zone_managed_pages(zone) / percpu_pagelist_high_fraction;
        }

        /*
         * Split the high value across all online CPUs local to the zone. Note
         * that early in boot that CPUs may not be online yet and that during
         * CPU hotplug that the cpumask is not yet updated when a CPU is being
         * onlined. For memory nodes that have no CPUs, split pcp->high across
         * all online CPUs to mitigate the risk that reclaim is triggered
         * prematurely due to pages stored on pcp lists.
         */
        nr_split_cpus = cpumask_weight(cpumask_of_node(zone_to_nid(zone))) + cpu_online;
        if (!nr_split_cpus)
                nr_split_cpus = num_online_cpus();
        high = total_pages / nr_split_cpus;

        /*
         * Ensure high is at least batch*4. The multiple is based on the
         * historical relationship between high and batch.
         */
        high = max(high, batch << 2);

        return high;
#else
        return 0;
#endif
}

/*
 * pcp->high and pcp->batch values are related and generally batch is lower
 * than high. They are also related to pcp->count such that count is lower
 * than high, and as soon as it reaches high, the pcplist is flushed.
 *
 * However, guaranteeing these relations at all times would require e.g. write
 * barriers here but also careful usage of read barriers at the read side, and
 * thus be prone to error and bad for performance. Thus the update only prevents
 * store tearing. Any new users of pcp->batch and pcp->high should ensure they
 * can cope with those fields changing asynchronously, and fully trust only the
 * pcp->count field on the local CPU with interrupts disabled.
 *
 * mutex_is_locked(&pcp_batch_high_lock) required when calling this function
 * outside of boot time (or some other assurance that no concurrent updaters
 * exist).
 */
static void pageset_update(struct per_cpu_pages *pcp, unsigned long high,
                unsigned long batch)
{
        WRITE_ONCE(pcp->batch, batch);
        WRITE_ONCE(pcp->high, high);
}

static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats)
{
        int pindex;

        memset(pcp, 0, sizeof(*pcp));
        memset(pzstats, 0, sizeof(*pzstats));

        for (pindex = 0; pindex < NR_PCP_LISTS; pindex++)
                INIT_LIST_HEAD(&pcp->lists[pindex]);

        /*
         * Set batch and high values safe for a boot pageset. A true percpu
         * pageset's initialization will update them subsequently. Here we don't
         * need to be as careful as pageset_update() as nobody can access the
         * pageset yet.
         */
        pcp->high = BOOT_PAGESET_HIGH;
        pcp->batch = BOOT_PAGESET_BATCH;
        pcp->free_factor = 0;
}

static void __zone_set_pageset_high_and_batch(struct zone *zone, unsigned long high,
                unsigned long batch)
{
        struct per_cpu_pages *pcp;
        int cpu;

        for_each_possible_cpu(cpu) {
                pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
                pageset_update(pcp, high, batch);
        }
}

/*
 * Calculate and set new high and batch values for all per-cpu pagesets of a
 * zone based on the zone's size.
 */
static void zone_set_pageset_high_and_batch(struct zone *zone, int cpu_online)
{
        int new_high, new_batch;

        new_batch = max(1, zone_batchsize(zone));
        new_high = zone_highsize(zone, new_batch, cpu_online);

        if (zone->pageset_high == new_high &&
            zone->pageset_batch == new_batch)
                return;

        zone->pageset_high = new_high;
        zone->pageset_batch = new_batch;

        __zone_set_pageset_high_and_batch(zone, new_high, new_batch);
}

void __meminit setup_zone_pageset(struct zone *zone)
{
        int cpu;

        /* Size may be 0 on !SMP && !NUMA */
        if (sizeof(struct per_cpu_zonestat) > 0)
                zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);

        zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
        for_each_possible_cpu(cpu) {
                struct per_cpu_pages *pcp;
                struct per_cpu_zonestat *pzstats;

                pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
                pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
                per_cpu_pages_init(pcp, pzstats);
        }

        zone_set_pageset_high_and_batch(zone, 0);
}

/*
 * Allocate per cpu pagesets and initialize them.
 * Before this call only boot pagesets were available.
 */
void __init setup_per_cpu_pageset(void)
{
        struct pglist_data *pgdat;
        struct zone *zone;
        int __maybe_unused cpu;

        for_each_populated_zone(zone)
                setup_zone_pageset(zone);

#ifdef CONFIG_NUMA
        /*
         * Unpopulated zones continue using the boot pagesets.
         * The numa stats for these pagesets need to be reset.
         * Otherwise, they will end up skewing the stats of
         * the nodes these zones are associated with.
         */
        for_each_possible_cpu(cpu) {
                struct per_cpu_zonestat *pzstats = &per_cpu(boot_zonestats, cpu);
                memset(pzstats->vm_numa_event, 0,
                       sizeof(pzstats->vm_numa_event));
        }
#endif

        for_each_online_pgdat(pgdat)
                pgdat->per_cpu_nodestats =
                        alloc_percpu(struct per_cpu_nodestat);
}

static __meminit void zone_pcp_init(struct zone *zone)
{
        /*
         * per cpu subsystem is not up at this point. The following code
         * relies on the ability of the linker to provide the
         * offset of a (static) per cpu variable into the per cpu area.
         */
        zone->per_cpu_pageset = &boot_pageset;
        zone->per_cpu_zonestats = &boot_zonestats;
        zone->pageset_high = BOOT_PAGESET_HIGH;
        zone->pageset_batch = BOOT_PAGESET_BATCH;

        if (populated_zone(zone))
                pr_debug("  %s zone: %lu pages, LIFO batch:%u\n", zone->name,
                         zone->present_pages, zone_batchsize(zone));
}

void __meminit init_currently_empty_zone(struct zone *zone,
                                        unsigned long zone_start_pfn,
                                        unsigned long size)
{
        struct pglist_data *pgdat = zone->zone_pgdat;
        int zone_idx = zone_idx(zone) + 1;

        if (zone_idx > pgdat->nr_zones)
                pgdat->nr_zones = zone_idx;

        zone->zone_start_pfn = zone_start_pfn;

        mminit_dprintk(MMINIT_TRACE, "memmap_init",
                        "Initialising map node %d zone %lu pfns %lu -> %lu\n",
                        pgdat->node_id,
                        (unsigned long)zone_idx(zone),
                        zone_start_pfn, (zone_start_pfn + size));

        zone_init_free_lists(zone);
        zone->initialized = 1;
}

/**
 * get_pfn_range_for_nid - Return the start and end page frames for a node
 * @nid: The nid to return the range for. If MAX_NUMNODES, the min and max PFN are returned.
 * @start_pfn: Passed by reference. On return, it will have the node start_pfn.
 * @end_pfn: Passed by reference. On return, it will have the node end_pfn.
 *
 * It returns the start and end page frame of a node based on information
 * provided by memblock_set_node(). If called for a node
 * with no available memory, a warning is printed and the start and end
 * PFNs will be 0.
 */
void __init get_pfn_range_for_nid(unsigned int nid,
                        unsigned long *start_pfn, unsigned long *end_pfn)
{
        unsigned long this_start_pfn, this_end_pfn;
        int i;

        *start_pfn = -1UL;
        *end_pfn = 0;

        for_each_mem_pfn_range(i, nid, &this_start_pfn, &this_end_pfn, NULL) {
                *start_pfn = min(*start_pfn, this_start_pfn);
                *end_pfn = max(*end_pfn, this_end_pfn);
        }

        if (*start_pfn == -1UL)
                *start_pfn = 0;
}

/*
 * This finds a zone that can be used for ZONE_MOVABLE pages. The
 * assumption is made that zones within a node are ordered in monotonic
 * increasing memory addresses so that the "highest" populated zone is used
 */
static void __init find_usable_zone_for_movable(void)
{
        int zone_index;
        for (zone_index = MAX_NR_ZONES - 1; zone_index >= 0; zone_index--) {
                if (zone_index == ZONE_MOVABLE)
                        continue;

                if (arch_zone_highest_possible_pfn[zone_index] >
                                arch_zone_lowest_possible_pfn[zone_index])
                        break;
        }

        VM_BUG_ON(zone_index == -1);
        movable_zone = zone_index;
}

/*
 * The zone ranges provided by the architecture do not include ZONE_MOVABLE
 * because it is sized independent of architecture. Unlike the other zones,
 * the starting point for ZONE_MOVABLE is not fixed. It may be different
 * in each node depending on the size of each node and how evenly kernelcore
 * is distributed. This helper function adjusts the zone ranges
 * provided by the architecture for a given node by using the end of the
 * highest usable zone for ZONE_MOVABLE. This preserves the assumption that
 * zones within a node are in order of monotonic increases memory addresses
 */
static void __init adjust_zone_range_for_zone_movable(int nid,
                                        unsigned long zone_type,
                                        unsigned long node_start_pfn,
                                        unsigned long node_end_pfn,
                                        unsigned long *zone_start_pfn,
                                        unsigned long *zone_end_pfn)
{
        /* Only adjust if ZONE_MOVABLE is on this node */
        if (zone_movable_pfn[nid]) {
                /* Size ZONE_MOVABLE */
                if (zone_type == ZONE_MOVABLE) {
                        *zone_start_pfn = zone_movable_pfn[nid];
                        *zone_end_pfn = min(node_end_pfn,
                                arch_zone_highest_possible_pfn[movable_zone]);

                /* Adjust for ZONE_MOVABLE starting within this range */
                } else if (!mirrored_kernelcore &&
                        *zone_start_pfn < zone_movable_pfn[nid] &&
                        *zone_end_pfn > zone_movable_pfn[nid]) {
                        *zone_end_pfn = zone_movable_pfn[nid];

                /* Check if this whole range is within ZONE_MOVABLE */
                } else if (*zone_start_pfn >= zone_movable_pfn[nid])
                        *zone_start_pfn = *zone_end_pfn;
        }
}

/*
 * Return the number of pages a zone spans in a node, including holes
 * present_pages = zone_spanned_pages_in_node() - zone_absent_pages_in_node()
 */
static unsigned long __init zone_spanned_pages_in_node(int nid,
                                        unsigned long zone_type,
                                        unsigned long node_start_pfn,
                                        unsigned long node_end_pfn,
                                        unsigned long *zone_start_pfn,
                                        unsigned long *zone_end_pfn)
{
        unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
        unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
        /* When hotadd a new node from cpu_up(), the node should be empty */
        if (!node_start_pfn && !node_end_pfn)
                return 0;

        /* Get the start and end of the zone */
        *zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
        *zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
        adjust_zone_range_for_zone_movable(nid, zone_type,
                                node_start_pfn, node_end_pfn,
                                zone_start_pfn, zone_end_pfn);

        /* Check that this node has pages within the zone's required range */
        if (*zone_end_pfn < node_start_pfn || *zone_start_pfn > node_end_pfn)
                return 0;

        /* Move the zone boundaries inside the node if necessary */
        *zone_end_pfn = min(*zone_end_pfn, node_end_pfn);
        *zone_start_pfn = max(*zone_start_pfn, node_start_pfn);

        /* Return the spanned pages */
        return *zone_end_pfn - *zone_start_pfn;
}

/*
 * Return the number of holes in a range on a node. If nid is MAX_NUMNODES,
 * then all holes in the requested range will be accounted for.
 */
unsigned long __init __absent_pages_in_range(int nid,
                                unsigned long range_start_pfn,
                                unsigned long range_end_pfn)
{
        unsigned long nr_absent = range_end_pfn - range_start_pfn;
        unsigned long start_pfn, end_pfn;
        int i;

        for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
                start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
                end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
                nr_absent -= end_pfn - start_pfn;
        }
        return nr_absent;
}

/**
 * absent_pages_in_range - Return number of page frames in holes within a range
 * @start_pfn: The start PFN to start searching for holes
 * @end_pfn: The end PFN to stop searching for holes
 *
 * Return: the number of pages frames in memory holes within a range.
 */
unsigned long __init absent_pages_in_range(unsigned long start_pfn,
                                                        unsigned long end_pfn)
{
        return __absent_pages_in_range(MAX_NUMNODES, start_pfn, end_pfn);
}

/* Return the number of page frames in holes in a zone on a node */
static unsigned long __init zone_absent_pages_in_node(int nid,
                                        unsigned long zone_type,
                                        unsigned long node_start_pfn,
                                        unsigned long node_end_pfn)
{
        unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
        unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
        unsigned long zone_start_pfn, zone_end_pfn;
        unsigned long nr_absent;

        /* When hotadd a new node from cpu_up(), the node should be empty */
        if (!node_start_pfn && !node_end_pfn)
                return 0;

        zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
        zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);

        adjust_zone_range_for_zone_movable(nid, zone_type,
                        node_start_pfn, node_end_pfn,
                        &zone_start_pfn, &zone_end_pfn);
        nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);

        /*
         * ZONE_MOVABLE handling.
         * Treat pages to be ZONE_MOVABLE in ZONE_NORMAL as absent pages
         * and vice versa.
         */
        if (mirrored_kernelcore && zone_movable_pfn[nid]) {
                unsigned long start_pfn, end_pfn;
                struct memblock_region *r;

                for_each_mem_region(r) {
                        start_pfn = clamp(memblock_region_memory_base_pfn(r),
                                          zone_start_pfn, zone_end_pfn);
                        end_pfn = clamp(memblock_region_memory_end_pfn(r),
                                        zone_start_pfn, zone_end_pfn);

                        if (zone_type == ZONE_MOVABLE &&
                            memblock_is_mirror(r))
                                nr_absent += end_pfn - start_pfn;

                        if (zone_type == ZONE_NORMAL &&
                            !memblock_is_mirror(r))
                                nr_absent += end_pfn - start_pfn;
                }
        }

        return nr_absent;
}

static void __init calculate_node_totalpages(struct pglist_data *pgdat,
                                                unsigned long node_start_pfn,
                                                unsigned long node_end_pfn)
{
        unsigned long realtotalpages = 0, totalpages = 0;
        enum zone_type i;

        for (i = 0; i < MAX_NR_ZONES; i++) {
                struct zone *zone = pgdat->node_zones + i;
                unsigned long zone_start_pfn, zone_end_pfn;
                unsigned long spanned, absent;
                unsigned long size, real_size;

                spanned = zone_spanned_pages_in_node(pgdat->node_id, i,
                                                     node_start_pfn,
                                                     node_end_pfn,
                                                     &zone_start_pfn,
                                                     &zone_end_pfn);
                absent = zone_absent_pages_in_node(pgdat->node_id, i,
                                                   node_start_pfn,
                                                   node_end_pfn);

                size = spanned;
                real_size = size - absent;

                if (size)
                        zone->zone_start_pfn = zone_start_pfn;
                else
                        zone->zone_start_pfn = 0;
                zone->spanned_pages = size;
                zone->present_pages = real_size;
#if defined(CONFIG_MEMORY_HOTPLUG)
                zone->present_early_pages = real_size;
#endif

                totalpages += size;
                realtotalpages += real_size;
        }

        pgdat->node_spanned_pages = totalpages;
        pgdat->node_present_pages = realtotalpages;
        pr_debug("On node %d totalpages: %lu\n", pgdat->node_id, realtotalpages);
}

#ifndef CONFIG_SPARSEMEM
/*
 * Calculate the size of the zone->blockflags rounded to an unsigned long
 * Start by making sure zonesize is a multiple of pageblock_order by rounding
 * up. Then use 1 NR_PAGEBLOCK_BITS worth of bits per pageblock, finally
 * round what is now in bits to nearest long in bits, then return it in
 * bytes.
 */
static unsigned long __init usemap_size(unsigned long zone_start_pfn, unsigned long zonesize)
{
        unsigned long usemapsize;

        zonesize += zone_start_pfn & (pageblock_nr_pages-1);
        usemapsize = roundup(zonesize, pageblock_nr_pages);
        usemapsize = usemapsize >> pageblock_order;
        usemapsize *= NR_PAGEBLOCK_BITS;
        usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long));

        return usemapsize / 8;
}

static void __ref setup_usemap(struct zone *zone)
{
        unsigned long usemapsize = usemap_size(zone->zone_start_pfn,
                                               zone->spanned_pages);
        zone->pageblock_flags = NULL;
        if (usemapsize) {
                zone->pageblock_flags =
                        memblock_alloc_node(usemapsize, SMP_CACHE_BYTES,
                                            zone_to_nid(zone));
                if (!zone->pageblock_flags)
                        panic("Failed to allocate %ld bytes for zone %s pageblock flags on node %d\n",
                              usemapsize, zone->name, zone_to_nid(zone));
        }
}
#else
static inline void setup_usemap(struct zone *zone) {}
#endif /* CONFIG_SPARSEMEM */

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE

/* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
void __init set_pageblock_order(void)
{
        unsigned int order;

        /* Check that pageblock_nr_pages has not already been setup */
        if (pageblock_order)
                return;

        if (HPAGE_SHIFT > PAGE_SHIFT)
                order = HUGETLB_PAGE_ORDER;
        else
                order = MAX_ORDER - 1;

        /*
         * Assume the largest contiguous order of interest is a huge page.
         * This value may be variable depending on boot parameters on IA64 and
         * powerpc.
         */
        pageblock_order = order;
}
#else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

/*
 * When CONFIG_HUGETLB_PAGE_SIZE_VARIABLE is not set, set_pageblock_order()
 * is unused as pageblock_order is set at compile-time. See
 * include/linux/pageblock-flags.h for the values of pageblock_order based on
 * the kernel config
 */
void __init set_pageblock_order(void)
{
}

#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

static unsigned long __init calc_memmap_size(unsigned long spanned_pages,
                                                unsigned long present_pages)
{
        unsigned long pages = spanned_pages;

        /*
         * Provide a more accurate estimation if there are holes within
         * the zone and SPARSEMEM is in use. If there are holes within the
         * zone, each populated memory region may cost us one or two extra
         * memmap pages due to alignment because memmap pages for each
         * populated regions may not be naturally aligned on page boundary.
         * So the (present_pages >> 4) heuristic is a tradeoff for that.
         */
        if (spanned_pages > present_pages + (present_pages >> 4) &&
            IS_ENABLED(CONFIG_SPARSEMEM))
                pages = present_pages;

        return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void pgdat_init_split_queue(struct pglist_data *pgdat)
{
        struct deferred_split *ds_queue = &pgdat->deferred_split_queue;

        spin_lock_init(&ds_queue->split_queue_lock);
        INIT_LIST_HEAD(&ds_queue->split_queue);
        ds_queue->split_queue_len = 0;
}
#else
static void pgdat_init_split_queue(struct pglist_data *pgdat) {}
#endif

#ifdef CONFIG_COMPACTION
static void pgdat_init_kcompactd(struct pglist_data *pgdat)
{
        init_waitqueue_head(&pgdat->kcompactd_wait);
}
#else
static void pgdat_init_kcompactd(struct pglist_data *pgdat) {}
#endif

static void __meminit pgdat_init_internals(struct pglist_data *pgdat)
{
        int i;

        pgdat_resize_init(pgdat);

        pgdat_init_split_queue(pgdat);
        pgdat_init_kcompactd(pgdat);

        init_waitqueue_head(&pgdat->kswapd_wait);
        init_waitqueue_head(&pgdat->pfmemalloc_wait);

        for (i = 0; i < NR_VMSCAN_THROTTLE; i++)
                init_waitqueue_head(&pgdat->reclaim_wait[i]);

        pgdat_page_ext_init(pgdat);
        lruvec_init(&pgdat->__lruvec);
}

static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx, int nid,
                                                        unsigned long remaining_pages)
{
        atomic_long_set(&zone->managed_pages, remaining_pages);
        zone_set_nid(zone, nid);
        zone->name = zone_names[idx];
        zone->zone_pgdat = NODE_DATA(nid);
        spin_lock_init(&zone->lock);
        zone_seqlock_init(zone);
        zone_pcp_init(zone);
}

/*
 * Set up the zone data structures
 * - init pgdat internals
 * - init all zones belonging to this node
 *
 * NOTE: this function is only called during memory hotplug
 */
#ifdef CONFIG_MEMORY_HOTPLUG
void __ref free_area_init_core_hotplug(int nid)
{
        enum zone_type z;
        pg_data_t *pgdat = NODE_DATA(nid);

        pgdat_init_internals(pgdat);
        for (z = 0; z < MAX_NR_ZONES; z++)
                zone_init_internals(&pgdat->node_zones[z], z, nid, 0);
}
#endif

/*
 * Set up the zone data structures:
 *   - mark all pages reserved
 *   - mark all memory queues empty
 *   - clear the memory bitmaps
 *
 * NOTE: pgdat should get zeroed by caller.
 * NOTE: this function is only called during early init.
 */
static void __init free_area_init_core(struct pglist_data *pgdat)
{
        enum zone_type j;
        int nid = pgdat->node_id;

        pgdat_init_internals(pgdat);
        pgdat->per_cpu_nodestats = &boot_nodestats;

        for (j = 0; j < MAX_NR_ZONES; j++) {
                struct zone *zone = pgdat->node_zones + j;
                unsigned long size, freesize, memmap_pages;

                size = zone->spanned_pages;
                freesize = zone->present_pages;

                /*
                 * Adjust freesize so that it accounts for how much memory
                 * is used by this zone for memmap. This affects the watermark
                 * and per-cpu initialisations
                 */
                memmap_pages = calc_memmap_size(size, freesize);
                if (!is_highmem_idx(j)) {
                        if (freesize >= memmap_pages) {
                                freesize -= memmap_pages;
                                if (memmap_pages)
                                        pr_debug("  %s zone: %lu pages used for memmap\n",
                                                 zone_names[j], memmap_pages);
                        } else
                                pr_warn("  %s zone: %lu memmap pages exceeds freesize %lu\n",
                                        zone_names[j], memmap_pages, freesize);
                }

                /* Account for reserved pages */
                if (j == 0 && freesize > dma_reserve) {
                        freesize -= dma_reserve;
                        pr_debug("  %s zone: %lu pages reserved\n", zone_names[0], dma_reserve);
                }

                if (!is_highmem_idx(j))
                        nr_kernel_pages += freesize;
                /* Charge for highmem memmap if there are enough kernel pages */
                else if (nr_kernel_pages > memmap_pages * 2)
                        nr_kernel_pages -= memmap_pages;
                nr_all_pages += freesize;

                /*
                 * Set an approximate value for lowmem here, it will be adjusted
                 * when the bootmem allocator frees pages into the buddy system.
                 * And all highmem pages will be managed by the buddy system.
                 */
                zone_init_internals(zone, j, nid, freesize);

                if (!size)
                        continue;

                set_pageblock_order();
                setup_usemap(zone);
                init_currently_empty_zone(zone, zone->zone_start_pfn, size);
        }
}

#ifdef CONFIG_FLATMEM
static void __init alloc_node_mem_map(struct pglist_data *pgdat)
{
        unsigned long __maybe_unused start = 0;
        unsigned long __maybe_unused offset = 0;

        /* Skip empty nodes */
        if (!pgdat->node_spanned_pages)
                return;

        start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
        offset = pgdat->node_start_pfn - start;
        /* ia64 gets its own node_mem_map, before this, without bootmem */
        if (!pgdat->node_mem_map) {
                unsigned long size, end;
                struct page *map;

                /*
                 * The zone's endpoints aren't required to be MAX_ORDER
                 * aligned but the node_mem_map endpoints must be in order
                 * for the buddy allocator to function correctly.
                 */
                end = pgdat_end_pfn(pgdat);
                end = ALIGN(end, MAX_ORDER_NR_PAGES);
                size =  (end - start) * sizeof(struct page);
                map = memmap_alloc(size, SMP_CACHE_BYTES, MEMBLOCK_LOW_LIMIT,
                                   pgdat->node_id, false);
                if (!map)
                        panic("Failed to allocate %ld bytes for node %d memory map\n",
                              size, pgdat->node_id);
                pgdat->node_mem_map = map + offset;
        }
        pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
                                __func__, pgdat->node_id, (unsigned long)pgdat,
                                (unsigned long)pgdat->node_mem_map);
#ifndef CONFIG_NUMA
        /*
         * With no DISCONTIG, the global mem_map is just set as node 0's
         */
        if (pgdat == NODE_DATA(0)) {
                mem_map = NODE_DATA(0)->node_mem_map;
                if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
                        mem_map -= offset;
        }
#endif
}
#else
static inline void alloc_node_mem_map(struct pglist_data *pgdat) { }
#endif /* CONFIG_FLATMEM */

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
static inline void pgdat_set_deferred_range(pg_data_t *pgdat)
{
        pgdat->first_deferred_pfn = ULONG_MAX;
}
#else
static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {}
#endif

static void __init free_area_init_node(int nid)
{
        pg_data_t *pgdat = NODE_DATA(nid);
        unsigned long start_pfn = 0;
        unsigned long end_pfn = 0;

        /* pg_data_t should be reset to zero when it's allocated */
        WARN_ON(pgdat->nr_zones || pgdat->kswapd_highest_zoneidx);

        get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);

        pgdat->node_id = nid;
        pgdat->node_start_pfn = start_pfn;
        pgdat->per_cpu_nodestats = NULL;

        pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
                (u64)start_pfn << PAGE_SHIFT,
                end_pfn ? ((u64)end_pfn << PAGE_SHIFT) - 1 : 0);
        calculate_node_totalpages(pgdat, start_pfn, end_pfn);

        alloc_node_mem_map(pgdat);
        pgdat_set_deferred_range(pgdat);

        free_area_init_core(pgdat);
}

void __init free_area_init_memoryless_node(int nid)
{
        free_area_init_node(nid);
}

#if MAX_NUMNODES > 1
/*
 * Figure out the number of possible node ids.
 */
void __init setup_nr_node_ids(void)
{
        unsigned int highest;

        highest = find_last_bit(node_possible_map.bits, MAX_NUMNODES);
        nr_node_ids = highest + 1;
}
#endif

/**
 * node_map_pfn_alignment - determine the maximum internode alignment
 *
 * This function should be called after node map is populated and sorted.
 * It calculates the maximum power of two alignment which can distinguish
 * all the nodes.
 *
 * For example, if all nodes are 1GiB and aligned to 1GiB, the return value
 * would indicate 1GiB alignment with (1 << (30 - PAGE_SHIFT)).  If the
 * nodes are shifted by 256MiB, 256MiB.  Note that if only the last node is
 * shifted, 1GiB is enough and this function will indicate so.
 *
 * This is used to test whether pfn -> nid mapping of the chosen memory
 * model has fine enough granularity to avoid incorrect mapping for the
 * populated node map.
 *
 * Return: the determined alignment in pfn's.  0 if there is no alignment
 * requirement (single node).
 */
unsigned long __init node_map_pfn_alignment(void)
{
        unsigned long accl_mask = 0, last_end = 0;
        unsigned long start, end, mask;
        int last_nid = NUMA_NO_NODE;
        int i, nid;

        for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid) {
                if (!start || last_nid < 0 || last_nid == nid) {
                        last_nid = nid;
                        last_end = end;
                        continue;
                }

                /*
                 * Start with a mask granular enough to pin-point to the
                 * start pfn and tick off bits one-by-one until it becomes
                 * too coarse to separate the current node from the last.
                 */
                mask = ~((1 << __ffs(start)) - 1);
                while (mask && last_end <= (start & (mask << 1)))
                        mask <<= 1;

                /* accumulate all internode masks */
                accl_mask |= mask;
        }

        /* convert mask to number of pages */
        return ~accl_mask + 1;
}

/**
 * find_min_pfn_with_active_regions - Find the minimum PFN registered
 *
 * Return: the minimum PFN based on information provided via
 * memblock_set_node().
 */
unsigned long __init find_min_pfn_with_active_regions(void)
{
        return PHYS_PFN(memblock_start_of_DRAM());
}

/*
 * early_calculate_totalpages()
 * Sum pages in active regions for movable zone.
 * Populate N_MEMORY for calculating usable_nodes.
 */
static unsigned long __init early_calculate_totalpages(void)
{
        unsigned long totalpages = 0;
        unsigned long start_pfn, end_pfn;
        int i, nid;

        for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
                unsigned long pages = end_pfn - start_pfn;

                totalpages += pages;
                if (pages)
                        node_set_state(nid, N_MEMORY);
        }
        return totalpages;
}

/*
 * Find the PFN the Movable zone begins in each node. Kernel memory
 * is spread evenly between nodes as long as the nodes have enough
 * memory. When they don't, some nodes will have more kernelcore than
 * others
 */
static void __init find_zone_movable_pfns_for_nodes(void)
{
        int i, nid;
        unsigned long usable_startpfn;
        unsigned long kernelcore_node, kernelcore_remaining;
        /* save the state before borrow the nodemask */
        nodemask_t saved_node_state = node_states[N_MEMORY];
        unsigned long totalpages = early_calculate_totalpages();
        int usable_nodes = nodes_weight(node_states[N_MEMORY]);
        struct memblock_region *r;

        /* Need to find movable_zone earlier when movable_node is specified. */
        find_usable_zone_for_movable();

        /*
         * If movable_node is specified, ignore kernelcore and movablecore
         * options.
         */
        if (movable_node_is_enabled()) {
                for_each_mem_region(r) {
                        if (!memblock_is_hotpluggable(r))
                                continue;

                        nid = memblock_get_region_node(r);

                        usable_startpfn = PFN_DOWN(r->base);
                        zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
                                min(usable_startpfn, zone_movable_pfn[nid]) :
                                usable_startpfn;
                }

                goto out2;
        }

        /*
         * If kernelcore=mirror is specified, ignore movablecore option
         */
        if (mirrored_kernelcore) {
                bool mem_below_4gb_not_mirrored = false;

                for_each_mem_region(r) {
                        if (memblock_is_mirror(r))
                                continue;

                        nid = memblock_get_region_node(r);

                        usable_startpfn = memblock_region_memory_base_pfn(r);

                        if (usable_startpfn < 0x100000) {
                                mem_below_4gb_not_mirrored = true;
                                continue;
                        }

                        zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
                                min(usable_startpfn, zone_movable_pfn[nid]) :
                                usable_startpfn;
                }

                if (mem_below_4gb_not_mirrored)
                        pr_warn("This configuration results in unmirrored kernel memory.\n");

                goto out2;
        }

        /*
         * If kernelcore=nn% or movablecore=nn% was specified, calculate the
         * amount of necessary memory.
         */
        if (required_kernelcore_percent)
                required_kernelcore = (totalpages * 100 * required_kernelcore_percent) /
                                       10000UL;
        if (required_movablecore_percent)
                required_movablecore = (totalpages * 100 * required_movablecore_percent) /
                                        10000UL;

        /*
         * If movablecore= was specified, calculate what size of
         * kernelcore that corresponds so that memory usable for
         * any allocation type is evenly spread. If both kernelcore
         * and movablecore are specified, then the value of kernelcore
         * will be used for required_kernelcore if it's greater than
         * what movablecore would have allowed.
         */
        if (required_movablecore) {
                unsigned long corepages;

                /*
                 * Round-up so that ZONE_MOVABLE is at least as large as what
                 * was requested by the user
                 */
                required_movablecore =
                        roundup(required_movablecore, MAX_ORDER_NR_PAGES);
                required_movablecore = min(totalpages, required_movablecore);
                corepages = totalpages - required_movablecore;

                required_kernelcore = max(required_kernelcore, corepages);
        }

        /*
         * If kernelcore was not specified or kernelcore size is larger
         * than totalpages, there is no ZONE_MOVABLE.
         */
        if (!required_kernelcore || required_kernelcore >= totalpages)
                goto out;

        /* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
        usable_startpfn = arch_zone_lowest_possible_pfn[movable_zone];

restart:
        /* Spread kernelcore memory as evenly as possible throughout nodes */
        kernelcore_node = required_kernelcore / usable_nodes;
        for_each_node_state(nid, N_MEMORY) {
                unsigned long start_pfn, end_pfn;

                /*
                 * Recalculate kernelcore_node if the division per node
                 * now exceeds what is necessary to satisfy the requested
                 * amount of memory for the kernel
                 */
                if (required_kernelcore < kernelcore_node)
                        kernelcore_node = required_kernelcore / usable_nodes;

                /*
                 * As the map is walked, we track how much memory is usable
                 * by the kernel using kernelcore_remaining. When it is
                 * 0, the rest of the node is usable by ZONE_MOVABLE
                 */
                kernelcore_remaining = kernelcore_node;

                /* Go through each range of PFNs within this node */
                for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
                        unsigned long size_pages;

                        start_pfn = max(start_pfn, zone_movable_pfn[nid]);
                        if (start_pfn >= end_pfn)
                                continue;

                        /* Account for what is only usable for kernelcore */
                        if (start_pfn < usable_startpfn) {
                                unsigned long kernel_pages;
                                kernel_pages = min(end_pfn, usable_startpfn)
                                                                - start_pfn;

                                kernelcore_remaining -= min(kernel_pages,
                                                        kernelcore_remaining);
                                required_kernelcore -= min(kernel_pages,
                                                        required_kernelcore);

                                /* Continue if range is now fully accounted */
                                if (end_pfn <= usable_startpfn) {

                                        /*
                                         * Push zone_movable_pfn to the end so
                                         * that if we have to rebalance
                                         * kernelcore across nodes, we will
                                         * not double account here
                                         */
                                        zone_movable_pfn[nid] = end_pfn;
                                        continue;
                                }
                                start_pfn = usable_startpfn;
                        }

                        /*
                         * The usable PFN range for ZONE_MOVABLE is from
                         * start_pfn->end_pfn. Calculate size_pages as the
                         * number of pages used as kernelcore
                         */
                        size_pages = end_pfn - start_pfn;
                        if (size_pages > kernelcore_remaining)
                                size_pages = kernelcore_remaining;
                        zone_movable_pfn[nid] = start_pfn + size_pages;

                        /*
                         * Some kernelcore has been met, update counts and
                         * break if the kernelcore for this node has been
                         * satisfied
                         */
                        required_kernelcore -= min(required_kernelcore,
                                                                size_pages);
                        kernelcore_remaining -= size_pages;
                        if (!kernelcore_remaining)
                                break;
                }
        }

        /*
         * If there is still required_kernelcore, we do another pass with one
         * less node in the count. This will push zone_movable_pfn[nid] further
         * along on the nodes that still have memory until kernelcore is
         * satisfied
         */
        usable_nodes--;
        if (usable_nodes && required_kernelcore > usable_nodes)
                goto restart;

out2:
        /* Align start of ZONE_MOVABLE on all nids to MAX_ORDER_NR_PAGES */
        for (nid = 0; nid < MAX_NUMNODES; nid++)
                zone_movable_pfn[nid] =
                        roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES);

out:
        /* restore the node_state */
        node_states[N_MEMORY] = saved_node_state;
}

/* Any regular or high memory on that node ? */
static void check_for_memory(pg_data_t *pgdat, int nid)
{
        enum zone_type zone_type;

        for (zone_type = 0; zone_type <= ZONE_MOVABLE - 1; zone_type++) {
                struct zone *zone = &pgdat->node_zones[zone_type];
                if (populated_zone(zone)) {
                        if (IS_ENABLED(CONFIG_HIGHMEM))
                                node_set_state(nid, N_HIGH_MEMORY);
                        if (zone_type <= ZONE_NORMAL)
                                node_set_state(nid, N_NORMAL_MEMORY);
                        break;
                }
        }
}

/*
 * Some architectures, e.g. ARC may have ZONE_HIGHMEM below ZONE_NORMAL. For
 * such cases we allow max_zone_pfn sorted in the descending order
 */
bool __weak arch_has_descending_max_zone_pfns(void)
{
        return false;
}

/**
 * free_area_init - Initialise all pg_data_t and zone data
 * @max_zone_pfn: an array of max PFNs for each zone
 *
 * This will call free_area_init_node() for each active node in the system.
 * Using the page ranges provided by memblock_set_node(), the size of each
 * zone in each node and their holes is calculated. If the maximum PFN
 * between two adjacent zones match, it is assumed that the zone is empty.
 * For example, if arch_max_dma_pfn == arch_max_dma32_pfn, it is assumed
 * that arch_max_dma32_pfn has no pages. It is also assumed that a zone
 * starts where the previous one ended. For example, ZONE_DMA32 starts
 * at arch_max_dma_pfn.
 */
void __init free_area_init(unsigned long *max_zone_pfn)
{
        unsigned long start_pfn, end_pfn;
        int i, nid, zone;
        bool descending;

        /* Record where the zone boundaries are */
        memset(arch_zone_lowest_possible_pfn, 0,
                                sizeof(arch_zone_lowest_possible_pfn));
        memset(arch_zone_highest_possible_pfn, 0,
                                sizeof(arch_zone_highest_possible_pfn));

        start_pfn = find_min_pfn_with_active_regions();
        descending = arch_has_descending_max_zone_pfns();

        for (i = 0; i < MAX_NR_ZONES; i++) {
                if (descending)
                        zone = MAX_NR_ZONES - i - 1;
                else
                        zone = i;

                if (zone == ZONE_MOVABLE)
                        continue;

                end_pfn = max(max_zone_pfn[zone], start_pfn);
                arch_zone_lowest_possible_pfn[zone] = start_pfn;
                arch_zone_highest_possible_pfn[zone] = end_pfn;

                start_pfn = end_pfn;
        }

        /* Find the PFNs that ZONE_MOVABLE begins at in each node */
        memset(zone_movable_pfn, 0, sizeof(zone_movable_pfn));
        find_zone_movable_pfns_for_nodes();

        /* Print out the zone ranges */
        pr_info("Zone ranges:\n");
        for (i = 0; i < MAX_NR_ZONES; i++) {
                if (i == ZONE_MOVABLE)
                        continue;
                pr_info("  %-8s ", zone_names[i]);
                if (arch_zone_lowest_possible_pfn[i] ==
                                arch_zone_highest_possible_pfn[i])
                        pr_cont("empty\n");
                else
                        pr_cont("[mem %#018Lx-%#018Lx]\n",
                                (u64)arch_zone_lowest_possible_pfn[i]
                                        << PAGE_SHIFT,
                                ((u64)arch_zone_highest_possible_pfn[i]
                                        << PAGE_SHIFT) - 1);
        }

        /* Print out the PFNs ZONE_MOVABLE begins at in each node */
        pr_info("Movable zone start for each node\n");
        for (i = 0; i < MAX_NUMNODES; i++) {
                if (zone_movable_pfn[i])
                        pr_info("  Node %d: %#018Lx\n", i,
                               (u64)zone_movable_pfn[i] << PAGE_SHIFT);
        }

        /*
         * Print out the early node map, and initialize the
         * subsection-map relative to active online memory ranges to
         * enable future "sub-section" extensions of the memory map.
         */
        pr_info("Early memory node ranges\n");
        for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
                pr_info("  node %3d: [mem %#018Lx-%#018Lx]\n", nid,
                        (u64)start_pfn << PAGE_SHIFT,
                        ((u64)end_pfn << PAGE_SHIFT) - 1);
                subsection_map_init(start_pfn, end_pfn - start_pfn);
        }

        /* Initialise every node */
        mminit_verify_pageflags_layout();
        setup_nr_node_ids();
        for_each_online_node(nid) {
                pg_data_t *pgdat = NODE_DATA(nid);
                free_area_init_node(nid);

                /* Any memory on that node */
                if (pgdat->node_present_pages)
                        node_set_state(nid, N_MEMORY);
                check_for_memory(pgdat, nid);
        }

        memmap_init();
}

static int __init cmdline_parse_core(char *p, unsigned long *core,
                                     unsigned long *percent)
{
        unsigned long long coremem;
        char *endptr;

        if (!p)
                return -EINVAL;

        /* Value may be a percentage of total memory, otherwise bytes */
        coremem = simple_strtoull(p, &endptr, 0);
        if (*endptr == '%') {
                /* Paranoid check for percent values greater than 100 */
                WARN_ON(coremem > 100);

                *percent = coremem;
        } else {
                coremem = memparse(p, &p);
                /* Paranoid check that UL is enough for the coremem value */
                WARN_ON((coremem >> PAGE_SHIFT) > ULONG_MAX);

                *core = coremem >> PAGE_SHIFT;
                *percent = 0UL;
        }
        return 0;
}

/*
 * kernelcore=size sets the amount of memory for use for allocations that
 * cannot be reclaimed or migrated.
 */
static int __init cmdline_parse_kernelcore(char *p)
{
        /* parse kernelcore=mirror */
        if (parse_option_str(p, "mirror")) {
                mirrored_kernelcore = true;
                return 0;
        }

        return cmdline_parse_core(p, &required_kernelcore,
                                  &required_kernelcore_percent);
}

/*
 * movablecore=size sets the amount of memory for use for allocations that
 * can be reclaimed or migrated.
 */
static int __init cmdline_parse_movablecore(char *p)
{
        return cmdline_parse_core(p, &required_movablecore,
                                  &required_movablecore_percent);
}

early_param("kernelcore", cmdline_parse_kernelcore);
early_param("movablecore", cmdline_parse_movablecore);

void adjust_managed_page_count(struct page *page, long count)
{
        atomic_long_add(count, &page_zone(page)->managed_pages);
        totalram_pages_add(count);
#ifdef CONFIG_HIGHMEM
        if (PageHighMem(page))
                totalhigh_pages_add(count);
#endif
}
EXPORT_SYMBOL(adjust_managed_page_count);

unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)
{
        void *pos;
        unsigned long pages = 0;

        start = (void *)PAGE_ALIGN((unsigned long)start);
        end = (void *)((unsigned long)end & PAGE_MASK);
        for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {
                struct page *page = virt_to_page(pos);
                void *direct_map_addr;

                /*
                 * 'direct_map_addr' might be different from 'pos'
                 * because some architectures' virt_to_page()
                 * work with aliases.  Getting the direct map
                 * address ensures that we get a _writeable_
                 * alias for the memset().
                 */
                direct_map_addr = page_address(page);
                /*
                 * Perform a kasan-unchecked memset() since this memory
                 * has not been initialized.
                 */
                direct_map_addr = kasan_reset_tag(direct_map_addr);
                if ((unsigned int)poison <= 0xFF)
                        memset(direct_map_addr, poison, PAGE_SIZE);

                free_reserved_page(page);
        }

        if (pages && s)
                pr_info("Freeing %s memory: %ldK\n", s, K(pages));

        return pages;
}

void __init mem_init_print_info(void)
{
        unsigned long physpages, codesize, datasize, rosize, bss_size;
        unsigned long init_code_size, init_data_size;

        physpages = get_num_physpages();
        codesize = _etext - _stext;
        datasize = _edata - _sdata;
        rosize = __end_rodata - __start_rodata;
        bss_size = __bss_stop - __bss_start;
        init_data_size = __init_end - __init_begin;
        init_code_size = _einittext - _sinittext;

        /*
         * Detect special cases and adjust section sizes accordingly:
         * 1) .init.* may be embedded into .data sections
         * 2) .init.text.* may be out of [__init_begin, __init_end],
         *    please refer to arch/tile/kernel/vmlinux.lds.S.
         * 3) .rodata.* may be embedded into .text or .data sections.
         */
#define adj_init_size(start, end, size, pos, adj) \
        do { \
                if (start <= pos && pos < end && size > adj) \
                        size -= adj; \
        } while (0)

        adj_init_size(__init_begin, __init_end, init_data_size,
                     _sinittext, init_code_size);
        adj_init_size(_stext, _etext, codesize, _sinittext, init_code_size);
        adj_init_size(_sdata, _edata, datasize, __init_begin, init_data_size);
        adj_init_size(_stext, _etext, codesize, __start_rodata, rosize);
        adj_init_size(_sdata, _edata, datasize, __start_rodata, rosize);

#undef  adj_init_size

        pr_info("Memory: %luK/%luK available (%luK kernel code, %luK rwdata, %luK rodata, %luK init, %luK bss, %luK reserved, %luK cma-reserved"
#ifdef  CONFIG_HIGHMEM
                ", %luK highmem"
#endif
                ")\n",
                K(nr_free_pages()), K(physpages),
                codesize >> 10, datasize >> 10, rosize >> 10,
                (init_data_size + init_code_size) >> 10, bss_size >> 10,
                K(physpages - totalram_pages() - totalcma_pages),
                K(totalcma_pages)
#ifdef  CONFIG_HIGHMEM
                , K(totalhigh_pages())
#endif
                );
}

/**
 * set_dma_reserve - set the specified number of pages reserved in the first zone
 * @new_dma_reserve: The number of pages to mark reserved
 *
 * The per-cpu batchsize and zone watermarks are determined by managed_pages.
 * In the DMA zone, a significant percentage may be consumed by kernel image
 * and other unfreeable allocations which can skew the watermarks badly. This
 * function may optionally be used to account for unfreeable pages in the
 * first zone (e.g., ZONE_DMA). The effect will be lower watermarks and
 * smaller per-cpu batchsize.
 */
void __init set_dma_reserve(unsigned long new_dma_reserve)
{
        dma_reserve = new_dma_reserve;
}

static int page_alloc_cpu_dead(unsigned int cpu)
{
        struct zone *zone;

        lru_add_drain_cpu(cpu);
        drain_pages(cpu);

        /*
         * Spill the event counters of the dead processor
         * into the current processors event counters.
         * This artificially elevates the count of the current
         * processor.
         */
        vm_events_fold_cpu(cpu);

        /*
         * Zero the differential counters of the dead processor
         * so that the vm statistics are consistent.
         *
         * This is only okay since the processor is dead and cannot
         * race with what we are doing.
         */
        cpu_vm_stats_fold(cpu);

        for_each_populated_zone(zone)
                zone_pcp_update(zone, 0);

        return 0;
}

static int page_alloc_cpu_online(unsigned int cpu)
{
        struct zone *zone;

        for_each_populated_zone(zone)
                zone_pcp_update(zone, 1);
        return 0;
}

#ifdef CONFIG_NUMA
int hashdist = HASHDIST_DEFAULT;

static int __init set_hashdist(char *str)
{
        if (!str)
                return 0;
        hashdist = simple_strtoul(str, &str, 0);
        return 1;
}
__setup("hashdist=", set_hashdist);
#endif

void __init page_alloc_init(void)
{
        int ret;

#ifdef CONFIG_NUMA
        if (num_node_state(N_MEMORY) == 1)
                hashdist = 0;
#endif

        ret = cpuhp_setup_state_nocalls(CPUHP_PAGE_ALLOC,
                                        "mm/page_alloc:pcp",
                                        page_alloc_cpu_online,
                                        page_alloc_cpu_dead);
        WARN_ON(ret < 0);
}

/*
 * calculate_totalreserve_pages - called when sysctl_lowmem_reserve_ratio
 *      or min_free_kbytes changes.
 */
static void calculate_totalreserve_pages(void)
{
        struct pglist_data *pgdat;
        unsigned long reserve_pages = 0;
        enum zone_type i, j;

        for_each_online_pgdat(pgdat) {

                pgdat->totalreserve_pages = 0;

                for (i = 0; i < MAX_NR_ZONES; i++) {
                        struct zone *zone = pgdat->node_zones + i;
                        long max = 0;
                        unsigned long managed_pages = zone_managed_pages(zone);

                        /* Find valid and maximum lowmem_reserve in the zone */
                        for (j = i; j < MAX_NR_ZONES; j++) {
                                if (zone->lowmem_reserve[j] > max)
                                        max = zone->lowmem_reserve[j];
                        }

                        /* we treat the high watermark as reserved pages. */
                        max += high_wmark_pages(zone);

                        if (max > managed_pages)
                                max = managed_pages;

                        pgdat->totalreserve_pages += max;

                        reserve_pages += max;
                }
        }
        totalreserve_pages = reserve_pages;
}

/*
 * setup_per_zone_lowmem_reserve - called whenever
 *      sysctl_lowmem_reserve_ratio changes.  Ensures that each zone
 *      has a correct pages reserved value, so an adequate number of
 *      pages are left in the zone after a successful __alloc_pages().
 */
static void setup_per_zone_lowmem_reserve(void)
{
        struct pglist_data *pgdat;
        enum zone_type i, j;

        for_each_online_pgdat(pgdat) {
                for (i = 0; i < MAX_NR_ZONES - 1; i++) {
                        struct zone *zone = &pgdat->node_zones[i];
                        int ratio = sysctl_lowmem_reserve_ratio[i];
                        bool clear = !ratio || !zone_managed_pages(zone);
                        unsigned long managed_pages = 0;

                        for (j = i + 1; j < MAX_NR_ZONES; j++) {
                                struct zone *upper_zone = &pgdat->node_zones[j];

                                managed_pages += zone_managed_pages(upper_zone);

                                if (clear)
                                        zone->lowmem_reserve[j] = 0;
                                else
                                        zone->lowmem_reserve[j] = managed_pages / ratio;
                        }
                }
        }

        /* update totalreserve_pages */
        calculate_totalreserve_pages();
}

static void __setup_per_zone_wmarks(void)
{
        unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
        unsigned long lowmem_pages = 0;
        struct zone *zone;
        unsigned long flags;

        /* Calculate total number of !ZONE_HIGHMEM pages */
        for_each_zone(zone) {
                if (!is_highmem(zone))
                        lowmem_pages += zone_managed_pages(zone);
        }

        for_each_zone(zone) {
                u64 tmp;

                spin_lock_irqsave(&zone->lock, flags);
                tmp = (u64)pages_min * zone_managed_pages(zone);
                do_div(tmp, lowmem_pages);
                if (is_highmem(zone)) {
                        /*
                         * __GFP_HIGH and PF_MEMALLOC allocations usually don't
                         * need highmem pages, so cap pages_min to a small
                         * value here.
                         *
                         * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN)
                         * deltas control async page reclaim, and so should
                         * not be capped for highmem.
                         */
                        unsigned long min_pages;

                        min_pages = zone_managed_pages(zone) / 1024;
                        min_pages = clamp(min_pages, SWAP_CLUSTER_MAX, 128UL);
                        zone->_watermark[WMARK_MIN] = min_pages;
                } else {
                        /*
                         * If it's a lowmem zone, reserve a number of pages
                         * proportionate to the zone's size.
                         */
                        zone->_watermark[WMARK_MIN] = tmp;
                }

                /*
                 * Set the kswapd watermarks distance according to the
                 * scale factor in proportion to available memory, but
                 * ensure a minimum size on small systems.
                 */
                tmp = max_t(u64, tmp >> 2,
                            mult_frac(zone_managed_pages(zone),
                                      watermark_scale_factor, 10000));

                zone->watermark_boost = 0;
                zone->_watermark[WMARK_LOW]  = min_wmark_pages(zone) + tmp;
                zone->_watermark[WMARK_HIGH] = min_wmark_pages(zone) + tmp * 2;

                spin_unlock_irqrestore(&zone->lock, flags);
        }

        /* update totalreserve_pages */
        calculate_totalreserve_pages();
}

/**
 * setup_per_zone_wmarks - called when min_free_kbytes changes
 * or when memory is hot-{added|removed}
 *
 * Ensures that the watermark[min,low,high] values for each zone are set
 * correctly with respect to min_free_kbytes.
 */
void setup_per_zone_wmarks(void)
{
        struct zone *zone;
        static DEFINE_SPINLOCK(lock);

        spin_lock(&lock);
        __setup_per_zone_wmarks();
        spin_unlock(&lock);

        /*
         * The watermark size have changed so update the pcpu batch
         * and high limits or the limits may be inappropriate.
         */
        for_each_zone(zone)
                zone_pcp_update(zone, 0);
}

/*
 * Initialise min_free_kbytes.
 *
 * For small machines we want it small (128k min).  For large machines
 * we want it large (256MB max).  But it is not linear, because network
 * bandwidth does not increase linearly with machine size.  We use
 *
 *      min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
 *      min_free_kbytes = sqrt(lowmem_kbytes * 16)
 *
 * which yields
 *
 * 16MB:        512k
 * 32MB:        724k
 * 64MB:        1024k
 * 128MB:       1448k
 * 256MB:       2048k
 * 512MB:       2896k
 * 1024MB:      4096k
 * 2048MB:      5792k
 * 4096MB:      8192k
 * 8192MB:      11584k
 * 16384MB:     16384k
 */
void calculate_min_free_kbytes(void)
{
        unsigned long lowmem_kbytes;
        int new_min_free_kbytes;

        lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
        new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);

        if (new_min_free_kbytes > user_min_free_kbytes)
                min_free_kbytes = clamp(new_min_free_kbytes, 128, 262144);
        else
                pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
                                new_min_free_kbytes, user_min_free_kbytes);

}

int __meminit init_per_zone_wmark_min(void)
{
        calculate_min_free_kbytes();
        setup_per_zone_wmarks();
        refresh_zone_stat_thresholds();
        setup_per_zone_lowmem_reserve();

#ifdef CONFIG_NUMA
        setup_min_unmapped_ratio();
        setup_min_slab_ratio();
#endif

        khugepaged_min_free_kbytes_update();

        return 0;
}
postcore_initcall(init_per_zone_wmark_min)

/*
 * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
 *      that we can call two helper functions whenever min_free_kbytes
 *      changes.
 */
int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
                void *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        if (write) {
                user_min_free_kbytes = min_free_kbytes;
                setup_per_zone_wmarks();
        }
        return 0;
}

int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
                void *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        if (write)
                setup_per_zone_wmarks();

        return 0;
}

#ifdef CONFIG_NUMA
static void setup_min_unmapped_ratio(void)
{
        pg_data_t *pgdat;
        struct zone *zone;

        for_each_online_pgdat(pgdat)
                pgdat->min_unmapped_pages = 0;

        for_each_zone(zone)
                zone->zone_pgdat->min_unmapped_pages += (zone_managed_pages(zone) *
                                                         sysctl_min_unmapped_ratio) / 100;
}


int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
                void *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        setup_min_unmapped_ratio();

        return 0;
}

static void setup_min_slab_ratio(void)
{
        pg_data_t *pgdat;
        struct zone *zone;

        for_each_online_pgdat(pgdat)
                pgdat->min_slab_pages = 0;

        for_each_zone(zone)
                zone->zone_pgdat->min_slab_pages += (zone_managed_pages(zone) *
                                                     sysctl_min_slab_ratio) / 100;
}

int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
                void *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        setup_min_slab_ratio();

        return 0;
}
#endif

/*
 * lowmem_reserve_ratio_sysctl_handler - just a wrapper around
 *      proc_dointvec() so that we can call setup_per_zone_lowmem_reserve()
 *      whenever sysctl_lowmem_reserve_ratio changes.
 *
 * The reserve ratio obviously has absolutely no relation with the
 * minimum watermarks. The lowmem reserve ratio can only make sense
 * if in function of the boot time zone sizes.
 */
int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write,
                void *buffer, size_t *length, loff_t *ppos)
{
        int i;

        proc_dointvec_minmax(table, write, buffer, length, ppos);

        for (i = 0; i < MAX_NR_ZONES; i++) {
                if (sysctl_lowmem_reserve_ratio[i] < 1)
                        sysctl_lowmem_reserve_ratio[i] = 0;
        }

        setup_per_zone_lowmem_reserve();
        return 0;
}

/*
 * percpu_pagelist_high_fraction - changes the pcp->high for each zone on each
 * cpu. It is the fraction of total pages in each zone that a hot per cpu
 * pagelist can have before it gets flushed back to buddy allocator.
 */
int percpu_pagelist_high_fraction_sysctl_handler(struct ctl_table *table,
                int write, void *buffer, size_t *length, loff_t *ppos)
{
        struct zone *zone;
        int old_percpu_pagelist_high_fraction;
        int ret;

        mutex_lock(&pcp_batch_high_lock);
        old_percpu_pagelist_high_fraction = percpu_pagelist_high_fraction;

        ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (!write || ret < 0)
                goto out;

        /* Sanity checking to avoid pcp imbalance */
        if (percpu_pagelist_high_fraction &&
            percpu_pagelist_high_fraction < MIN_PERCPU_PAGELIST_HIGH_FRACTION) {
                percpu_pagelist_high_fraction = old_percpu_pagelist_high_fraction;
                ret = -EINVAL;
                goto out;
        }

        /* No change? */
        if (percpu_pagelist_high_fraction == old_percpu_pagelist_high_fraction)
                goto out;

        for_each_populated_zone(zone)
                zone_set_pageset_high_and_batch(zone, 0);
out:
        mutex_unlock(&pcp_batch_high_lock);
        return ret;
}

#ifndef __HAVE_ARCH_RESERVED_KERNEL_PAGES
/*
 * Returns the number of pages that arch has reserved but
 * is not known to alloc_large_system_hash().
 */
static unsigned long __init arch_reserved_kernel_pages(void)
{
        return 0;
}
#endif

/*
 * Adaptive scale is meant to reduce sizes of hash tables on large memory
 * machines. As memory size is increased the scale is also increased but at
 * slower pace.  Starting from ADAPT_SCALE_BASE (64G), every time memory
 * quadruples the scale is increased by one, which means the size of hash table
 * only doubles, instead of quadrupling as well.
 * Because 32-bit systems cannot have large physical memory, where this scaling
 * makes sense, it is disabled on such platforms.
 */
#if __BITS_PER_LONG > 32
#define ADAPT_SCALE_BASE        (64ul << 30)
#define ADAPT_SCALE_SHIFT       2
#define ADAPT_SCALE_NPAGES      (ADAPT_SCALE_BASE >> PAGE_SHIFT)
#endif

/*
 * allocate a large system hash table from bootmem
 * - it is assumed that the hash table must contain an exact power-of-2
 *   quantity of entries
 * - limit is the number of hash buckets, not the total allocation size
 */
void *__init alloc_large_system_hash(const char *tablename,
                                     unsigned long bucketsize,
                                     unsigned long numentries,
                                     int scale,
                                     int flags,
                                     unsigned int *_hash_shift,
                                     unsigned int *_hash_mask,
                                     unsigned long low_limit,
                                     unsigned long high_limit)
{
        unsigned long long max = high_limit;
        unsigned long log2qty, size;
        void *table = NULL;
        gfp_t gfp_flags;
        bool virt;
        bool huge;

        /* allow the kernel cmdline to have a say */
        if (!numentries) {
                /* round applicable memory size up to nearest megabyte */
                numentries = nr_kernel_pages;
                numentries -= arch_reserved_kernel_pages();

                /* It isn't necessary when PAGE_SIZE >= 1MB */
                if (PAGE_SHIFT < 20)
                        numentries = round_up(numentries, (1<<20)/PAGE_SIZE);

#if __BITS_PER_LONG > 32
                if (!high_limit) {
                        unsigned long adapt;

                        for (adapt = ADAPT_SCALE_NPAGES; adapt < numentries;
                             adapt <<= ADAPT_SCALE_SHIFT)
                                scale++;
                }
#endif

                /* limit to 1 bucket per 2^scale bytes of low memory */
                if (scale > PAGE_SHIFT)
                        numentries >>= (scale - PAGE_SHIFT);
                else
                        numentries <<= (PAGE_SHIFT - scale);

                /* Make sure we've got at least a 0-order allocation.. */
                if (unlikely(flags & HASH_SMALL)) {
                        /* Makes no sense without HASH_EARLY */
                        WARN_ON(!(flags & HASH_EARLY));
                        if (!(numentries >> *_hash_shift)) {
                                numentries = 1UL << *_hash_shift;
                                BUG_ON(!numentries);
                        }
                } else if (unlikely((numentries * bucketsize) < PAGE_SIZE))
                        numentries = PAGE_SIZE / bucketsize;
        }
        numentries = roundup_pow_of_two(numentries);

        /* limit allocation size to 1/16 total memory by default */
        if (max == 0) {
                max = ((unsigned long long)nr_all_pages << PAGE_SHIFT) >> 4;
                do_div(max, bucketsize);
        }
        max = min(max, 0x80000000ULL);

        if (numentries < low_limit)
                numentries = low_limit;
        if (numentries > max)
                numentries = max;

        log2qty = ilog2(numentries);

        gfp_flags = (flags & HASH_ZERO) ? GFP_ATOMIC | __GFP_ZERO : GFP_ATOMIC;
        do {
                virt = false;
                size = bucketsize << log2qty;
                if (flags & HASH_EARLY) {
                        if (flags & HASH_ZERO)
                                table = memblock_alloc(size, SMP_CACHE_BYTES);
                        else
                                table = memblock_alloc_raw(size,
                                                           SMP_CACHE_BYTES);
                } else if (get_order(size) >= MAX_ORDER || hashdist) {
                        table = __vmalloc(size, gfp_flags);
                        virt = true;
                        if (table)
                                huge = is_vm_area_hugepages(table);
                } else {
                        /*
                         * If bucketsize is not a power-of-two, we may free
                         * some pages at the end of hash table which
                         * alloc_pages_exact() automatically does
                         */
                        table = alloc_pages_exact(size, gfp_flags);
                        kmemleak_alloc(table, size, 1, gfp_flags);
                }
        } while (!table && size > PAGE_SIZE && --log2qty);

        if (!table)
                panic("Failed to allocate %s hash table\n", tablename);

        pr_info("%s hash table entries: %ld (order: %d, %lu bytes, %s)\n",
                tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size,
                virt ? (huge ? "vmalloc hugepage" : "vmalloc") : "linear");

        if (_hash_shift)
                *_hash_shift = log2qty;
        if (_hash_mask)
                *_hash_mask = (1 << log2qty) - 1;

        return table;
}

/*
 * This function checks whether pageblock includes unmovable pages or not.
 *
 * PageLRU check without isolation or lru_lock could race so that
 * MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable
 * check without lock_page also may miss some movable non-lru pages at
 * race condition. So you can't expect this function should be exact.
 *
 * Returns a page without holding a reference. If the caller wants to
 * dereference that page (e.g., dumping), it has to make sure that it
 * cannot get removed (e.g., via memory unplug) concurrently.
 *
 */
struct page *has_unmovable_pages(struct zone *zone, struct page *page,
                                 int migratetype, int flags)
{
        unsigned long iter = 0;
        unsigned long pfn = page_to_pfn(page);
        unsigned long offset = pfn % pageblock_nr_pages;

        if (is_migrate_cma_page(page)) {
                /*
                 * CMA allocations (alloc_contig_range) really need to mark
                 * isolate CMA pageblocks even when they are not movable in fact
                 * so consider them movable here.
                 */
                if (is_migrate_cma(migratetype))
                        return NULL;

                return page;
        }

        for (; iter < pageblock_nr_pages - offset; iter++) {
                page = pfn_to_page(pfn + iter);

                /*
                 * Both, bootmem allocations and memory holes are marked
                 * PG_reserved and are unmovable. We can even have unmovable
                 * allocations inside ZONE_MOVABLE, for example when
                 * specifying "movablecore".
                 */
                if (PageReserved(page))
                        return page;

                /*
                 * If the zone is movable and we have ruled out all reserved
                 * pages then it should be reasonably safe to assume the rest
                 * is movable.
                 */
                if (zone_idx(zone) == ZONE_MOVABLE)
                        continue;

                /*
                 * Hugepages are not in LRU lists, but they're movable.
                 * THPs are on the LRU, but need to be counted as #small pages.
                 * We need not scan over tail pages because we don't
                 * handle each tail page individually in migration.
                 */
                if (PageHuge(page) || PageTransCompound(page)) {
                        struct page *head = compound_head(page);
                        unsigned int skip_pages;

                        if (PageHuge(page)) {
                                if (!hugepage_migration_supported(page_hstate(head)))
                                        return page;
                        } else if (!PageLRU(head) && !__PageMovable(head)) {
                                return page;
                        }

                        skip_pages = compound_nr(head) - (page - head);
                        iter += skip_pages - 1;
                        continue;
                }

                /*
                 * We can't use page_count without pin a page
                 * because another CPU can free compound page.
                 * This check already skips compound tails of THP
                 * because their page->_refcount is zero at all time.
                 */
                if (!page_ref_count(page)) {
                        if (PageBuddy(page))
                                iter += (1 << buddy_order(page)) - 1;
                        continue;
                }

                /*
                 * The HWPoisoned page may be not in buddy system, and
                 * page_count() is not 0.
                 */
                if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
                        continue;

                /*
                 * We treat all PageOffline() pages as movable when offlining
                 * to give drivers a chance to decrement their reference count
                 * in MEM_GOING_OFFLINE in order to indicate that these pages
                 * can be offlined as there are no direct references anymore.
                 * For actually unmovable PageOffline() where the driver does
                 * not support this, we will fail later when trying to actually
                 * move these pages that still have a reference count > 0.
                 * (false negatives in this function only)
                 */
                if ((flags & MEMORY_OFFLINE) && PageOffline(page))
                        continue;

                if (__PageMovable(page) || PageLRU(page))
                        continue;

                /*
                 * If there are RECLAIMABLE pages, we need to check
                 * it.  But now, memory offline itself doesn't call
                 * shrink_node_slabs() and it still to be fixed.
                 */
                return page;
        }
        return NULL;
}

#ifdef CONFIG_CONTIG_ALLOC
static unsigned long pfn_max_align_down(unsigned long pfn)
{
        return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
                             pageblock_nr_pages) - 1);
}

static unsigned long pfn_max_align_up(unsigned long pfn)
{
        return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
                                pageblock_nr_pages));
}

#if defined(CONFIG_DYNAMIC_DEBUG) || \
        (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
/* Usage: See admin-guide/dynamic-debug-howto.rst */
static void alloc_contig_dump_pages(struct list_head *page_list)
{
        DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, "migrate failure");

        if (DYNAMIC_DEBUG_BRANCH(descriptor)) {
                struct page *page;

                dump_stack();
                list_for_each_entry(page, page_list, lru)
                        dump_page(page, "migration failure");
        }
}
#else
static inline void alloc_contig_dump_pages(struct list_head *page_list)
{
}
#endif

/* [start, end) must belong to a single zone. */
static int __alloc_contig_migrate_range(struct compact_control *cc,
                                        unsigned long start, unsigned long end)
{
        /* This function is based on compact_zone() from compaction.c. */
        unsigned int nr_reclaimed;
        unsigned long pfn = start;
        unsigned int tries = 0;
        int ret = 0;
        struct migration_target_control mtc = {
                .nid = zone_to_nid(cc->zone),
                .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
        };

        lru_cache_disable();

        while (pfn < end || !list_empty(&cc->migratepages)) {
                if (fatal_signal_pending(current)) {
                        ret = -EINTR;
                        break;
                }

                if (list_empty(&cc->migratepages)) {
                        cc->nr_migratepages = 0;
                        ret = isolate_migratepages_range(cc, pfn, end);
                        if (ret && ret != -EAGAIN)
                                break;
                        pfn = cc->migrate_pfn;
                        tries = 0;
                } else if (++tries == 5) {
                        ret = -EBUSY;
                        break;
                }

                nr_reclaimed = reclaim_clean_pages_from_list(cc->zone,
                                                        &cc->migratepages);
                cc->nr_migratepages -= nr_reclaimed;

                ret = migrate_pages(&cc->migratepages, alloc_migration_target,
                        NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE, NULL);

                /*
                 * On -ENOMEM, migrate_pages() bails out right away. It is pointless
                 * to retry again over this error, so do the same here.
                 */
                if (ret == -ENOMEM)
                        break;
        }

        lru_cache_enable();
        if (ret < 0) {
                if (ret == -EBUSY)
                        alloc_contig_dump_pages(&cc->migratepages);
                putback_movable_pages(&cc->migratepages);
                return ret;
        }
        return 0;
}

/**
 * alloc_contig_range() -- tries to allocate given range of pages
 * @start:      start PFN to allocate
 * @end:        one-past-the-last PFN to allocate
 * @migratetype:        migratetype of the underlying pageblocks (either
 *                      #MIGRATE_MOVABLE or #MIGRATE_CMA).  All pageblocks
 *                      in range must have the same migratetype and it must
 *                      be either of the two.
 * @gfp_mask:   GFP mask to use during compaction
 *
 * The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES
 * aligned.  The PFN range must belong to a single zone.
 *
 * The first thing this routine does is attempt to MIGRATE_ISOLATE all
 * pageblocks in the range.  Once isolated, the pageblocks should not
 * be modified by others.
 *
 * Return: zero on success or negative error code.  On success all
 * pages which PFN is in [start, end) are allocated for the caller and
 * need to be freed with free_contig_range().
 */
int alloc_contig_range(unsigned long start, unsigned long end,
                       unsigned migratetype, gfp_t gfp_mask)
{
        unsigned long outer_start, outer_end;
        unsigned int order;
        int ret = 0;

        struct compact_control cc = {
                .nr_migratepages = 0,
                .order = -1,
                .zone = page_zone(pfn_to_page(start)),
                .mode = MIGRATE_SYNC,
                .ignore_skip_hint = true,
                .no_set_skip_hint = true,
                .gfp_mask = current_gfp_context(gfp_mask),
                .alloc_contig = true,
        };
        INIT_LIST_HEAD(&cc.migratepages);

        /*
         * What we do here is we mark all pageblocks in range as
         * MIGRATE_ISOLATE.  Because pageblock and max order pages may
         * have different sizes, and due to the way page allocator
         * work, we align the range to biggest of the two pages so
         * that page allocator won't try to merge buddies from
         * different pageblocks and change MIGRATE_ISOLATE to some
         * other migration type.
         *
         * Once the pageblocks are marked as MIGRATE_ISOLATE, we
         * migrate the pages from an unaligned range (ie. pages that
         * we are interested in).  This will put all the pages in
         * range back to page allocator as MIGRATE_ISOLATE.
         *
         * When this is done, we take the pages in range from page
         * allocator removing them from the buddy system.  This way
         * page allocator will never consider using them.
         *
         * This lets us mark the pageblocks back as
         * MIGRATE_CMA/MIGRATE_MOVABLE so that free pages in the
         * aligned range but not in the unaligned, original range are
         * put back to page allocator so that buddy can use them.
         */

        ret = start_isolate_page_range(pfn_max_align_down(start),
                                       pfn_max_align_up(end), migratetype, 0);
        if (ret)
                return ret;

        drain_all_pages(cc.zone);

        /*
         * In case of -EBUSY, we'd like to know which page causes problem.
         * So, just fall through. test_pages_isolated() has a tracepoint
         * which will report the busy page.
         *
         * It is possible that busy pages could become available before
         * the call to test_pages_isolated, and the range will actually be
         * allocated.  So, if we fall through be sure to clear ret so that
         * -EBUSY is not accidentally used or returned to caller.
         */
        ret = __alloc_contig_migrate_range(&cc, start, end);
        if (ret && ret != -EBUSY)
                goto done;
        ret = 0;

        /*
         * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
         * aligned blocks that are marked as MIGRATE_ISOLATE.  What's
         * more, all pages in [start, end) are free in page allocator.
         * What we are going to do is to allocate all pages from
         * [start, end) (that is remove them from page allocator).
         *
         * The only problem is that pages at the beginning and at the
         * end of interesting range may be not aligned with pages that
         * page allocator holds, ie. they can be part of higher order
         * pages.  Because of this, we reserve the bigger range and
         * once this is done free the pages we are not interested in.
         *
         * We don't have to hold zone->lock here because the pages are
         * isolated thus they won't get removed from buddy.
         */

        order = 0;
        outer_start = start;
        while (!PageBuddy(pfn_to_page(outer_start))) {
                if (++order >= MAX_ORDER) {
                        outer_start = start;
                        break;
                }
                outer_start &= ~0UL << order;
        }

        if (outer_start != start) {
                order = buddy_order(pfn_to_page(outer_start));

                /*
                 * outer_start page could be small order buddy page and
                 * it doesn't include start page. Adjust outer_start
                 * in this case to report failed page properly
                 * on tracepoint in test_pages_isolated()
                 */
                if (outer_start + (1UL << order) <= start)
                        outer_start = start;
        }

        /* Make sure the range is really isolated. */
        if (test_pages_isolated(outer_start, end, 0)) {
                ret = -EBUSY;
                goto done;
        }

        /* Grab isolated pages from freelists. */
        outer_end = isolate_freepages_range(&cc, outer_start, end);
        if (!outer_end) {
                ret = -EBUSY;
                goto done;
        }

        /* Free head and tail (if any) */
        if (start != outer_start)
                free_contig_range(outer_start, start - outer_start);
        if (end != outer_end)
                free_contig_range(end, outer_end - end);

done:
        undo_isolate_page_range(pfn_max_align_down(start),
                                pfn_max_align_up(end), migratetype);
        return ret;
}
EXPORT_SYMBOL(alloc_contig_range);

static int __alloc_contig_pages(unsigned long start_pfn,
                                unsigned long nr_pages, gfp_t gfp_mask)
{
        unsigned long end_pfn = start_pfn + nr_pages;

        return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
                                  gfp_mask);
}

static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
                                   unsigned long nr_pages)
{
        unsigned long i, end_pfn = start_pfn + nr_pages;
        struct page *page;

        for (i = start_pfn; i < end_pfn; i++) {
                page = pfn_to_online_page(i);
                if (!page)
                        return false;

                if (page_zone(page) != z)
                        return false;

                if (PageReserved(page))
                        return false;
        }
        return true;
}

static bool zone_spans_last_pfn(const struct zone *zone,
                                unsigned long start_pfn, unsigned long nr_pages)
{
        unsigned long last_pfn = start_pfn + nr_pages - 1;

        return zone_spans_pfn(zone, last_pfn);
}

/**
 * alloc_contig_pages() -- tries to find and allocate contiguous range of pages
 * @nr_pages:   Number of contiguous pages to allocate
 * @gfp_mask:   GFP mask to limit search and used during compaction
 * @nid:        Target node
 * @nodemask:   Mask for other possible nodes
 *
 * This routine is a wrapper around alloc_contig_range(). It scans over zones
 * on an applicable zonelist to find a contiguous pfn range which can then be
 * tried for allocation with alloc_contig_range(). This routine is intended
 * for allocation requests which can not be fulfilled with the buddy allocator.
 *
 * The allocated memory is always aligned to a page boundary. If nr_pages is a
 * power of two then the alignment is guaranteed to be to the given nr_pages
 * (e.g. 1GB request would be aligned to 1GB).
 *
 * Allocated pages can be freed with free_contig_range() or by manually calling
 * __free_page() on each allocated page.
 *
 * Return: pointer to contiguous pages on success, or NULL if not successful.
 */
struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
                                int nid, nodemask_t *nodemask)
{
        unsigned long ret, pfn, flags;
        struct zonelist *zonelist;
        struct zone *zone;
        struct zoneref *z;

        zonelist = node_zonelist(nid, gfp_mask);
        for_each_zone_zonelist_nodemask(zone, z, zonelist,
                                        gfp_zone(gfp_mask), nodemask) {
                spin_lock_irqsave(&zone->lock, flags);

                pfn = ALIGN(zone->zone_start_pfn, nr_pages);
                while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
                        if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
                                /*
                                 * We release the zone lock here because
                                 * alloc_contig_range() will also lock the zone
                                 * at some point. If there's an allocation
                                 * spinning on this lock, it may win the race
                                 * and cause alloc_contig_range() to fail...
                                 */
                                spin_unlock_irqrestore(&zone->lock, flags);
                                ret = __alloc_contig_pages(pfn, nr_pages,
                                                        gfp_mask);
                                if (!ret)
                                        return pfn_to_page(pfn);
                                spin_lock_irqsave(&zone->lock, flags);
                        }
                        pfn += nr_pages;
                }
                spin_unlock_irqrestore(&zone->lock, flags);
        }
        return NULL;
}
#endif /* CONFIG_CONTIG_ALLOC */

void free_contig_range(unsigned long pfn, unsigned long nr_pages)
{
        unsigned long count = 0;

        for (; nr_pages--; pfn++) {
                struct page *page = pfn_to_page(pfn);

                count += page_count(page) != 1;
                __free_page(page);
        }
        WARN(count != 0, "%lu pages are still in use!\n", count);
}
EXPORT_SYMBOL(free_contig_range);

/*
 * The zone indicated has a new number of managed_pages; batch sizes and percpu
 * page high values need to be recalculated.
 */
void zone_pcp_update(struct zone *zone, int cpu_online)
{
        mutex_lock(&pcp_batch_high_lock);
        zone_set_pageset_high_and_batch(zone, cpu_online);
        mutex_unlock(&pcp_batch_high_lock);
}

/*
 * Effectively disable pcplists for the zone by setting the high limit to 0
 * and draining all cpus. A concurrent page freeing on another CPU that's about
 * to put the page on pcplist will either finish before the drain and the page
 * will be drained, or observe the new high limit and skip the pcplist.
 *
 * Must be paired with a call to zone_pcp_enable().
 */
void zone_pcp_disable(struct zone *zone)
{
        mutex_lock(&pcp_batch_high_lock);
        __zone_set_pageset_high_and_batch(zone, 0, 1);
        __drain_all_pages(zone, true);
}

void zone_pcp_enable(struct zone *zone)
{
        __zone_set_pageset_high_and_batch(zone, zone->pageset_high, zone->pageset_batch);
        mutex_unlock(&pcp_batch_high_lock);
}

void zone_pcp_reset(struct zone *zone)
{
        int cpu;
        struct per_cpu_zonestat *pzstats;

        if (zone->per_cpu_pageset != &boot_pageset) {
                for_each_online_cpu(cpu) {
                        pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
                        drain_zonestat(zone, pzstats);
                }
                free_percpu(zone->per_cpu_pageset);
                free_percpu(zone->per_cpu_zonestats);
                zone->per_cpu_pageset = &boot_pageset;
                zone->per_cpu_zonestats = &boot_zonestats;
        }
}

#ifdef CONFIG_MEMORY_HOTREMOVE
/*
 * All pages in the range must be in a single zone, must not contain holes,
 * must span full sections, and must be isolated before calling this function.
 */
void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
{
        unsigned long pfn = start_pfn;
        struct page *page;
        struct zone *zone;
        unsigned int order;
        unsigned long flags;

        offline_mem_sections(pfn, end_pfn);
        zone = page_zone(pfn_to_page(pfn));
        spin_lock_irqsave(&zone->lock, flags);
        while (pfn < end_pfn) {
                page = pfn_to_page(pfn);
                /*
                 * The HWPoisoned page may be not in buddy system, and
                 * page_count() is not 0.
                 */
                if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
                        pfn++;
                        continue;
                }
                /*
                 * At this point all remaining PageOffline() pages have a
                 * reference count of 0 and can simply be skipped.
                 */
                if (PageOffline(page)) {
                        BUG_ON(page_count(page));
                        BUG_ON(PageBuddy(page));
                        pfn++;
                        continue;
                }

                BUG_ON(page_count(page));
                BUG_ON(!PageBuddy(page));
                order = buddy_order(page);
                del_page_from_free_list(page, zone, order);
                pfn += (1 << order);
        }
        spin_unlock_irqrestore(&zone->lock, flags);
}
#endif

/*
 * This function returns a stable result only if called under zone lock.
 */
bool is_free_buddy_page(struct page *page)
{
        unsigned long pfn = page_to_pfn(page);
        unsigned int order;

        for (order = 0; order < MAX_ORDER; order++) {
                struct page *page_head = page - (pfn & ((1 << order) - 1));

                if (PageBuddy(page_head) &&
                    buddy_order_unsafe(page_head) >= order)
                        break;
        }

        return order < MAX_ORDER;
}

#ifdef CONFIG_MEMORY_FAILURE
/*
 * Break down a higher-order page in sub-pages, and keep our target out of
 * buddy allocator.
 */
static void break_down_buddy_pages(struct zone *zone, struct page *page,
                                   struct page *target, int low, int high,
                                   int migratetype)
{
        unsigned long size = 1 << high;
        struct page *current_buddy, *next_page;

        while (high > low) {
                high--;
                size >>= 1;

                if (target >= &page[size]) {
                        next_page = page + size;
                        current_buddy = page;
                } else {
                        next_page = page;
                        current_buddy = page + size;
                }

                if (set_page_guard(zone, current_buddy, high, migratetype))
                        continue;

                if (current_buddy != target) {
                        add_to_free_list(current_buddy, zone, high, migratetype);
                        set_buddy_order(current_buddy, high);
                        page = next_page;
                }
        }
}

/*
 * Take a page that will be marked as poisoned off the buddy allocator.
 */
bool take_page_off_buddy(struct page *page)
{
        struct zone *zone = page_zone(page);
        unsigned long pfn = page_to_pfn(page);
        unsigned long flags;
        unsigned int order;
        bool ret = false;

        spin_lock_irqsave(&zone->lock, flags);
        for (order = 0; order < MAX_ORDER; order++) {
                struct page *page_head = page - (pfn & ((1 << order) - 1));
                int page_order = buddy_order(page_head);

                if (PageBuddy(page_head) && page_order >= order) {
                        unsigned long pfn_head = page_to_pfn(page_head);
                        int migratetype = get_pfnblock_migratetype(page_head,
                                                                   pfn_head);

                        del_page_from_free_list(page_head, zone, page_order);
                        break_down_buddy_pages(zone, page_head, page, 0,
                                                page_order, migratetype);
                        if (!is_migrate_isolate(migratetype))
                                __mod_zone_freepage_state(zone, -1, migratetype);
                        ret = true;
                        break;
                }
                if (page_count(page_head) > 0)
                        break;
        }
        spin_unlock_irqrestore(&zone->lock, flags);
        return ret;
}
#endif