Merge tag 'nfs-for-6.12-1' of git://git.linux-nfs.org/projects/anna/linux-nfs

[linux.git] / drivers / md / md-bitmap.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * bitmap.c two-level bitmap (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
 *
 * bitmap_create  - sets up the bitmap structure
 * bitmap_destroy - destroys the bitmap structure
 *
 * additions, Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.:
 * - added disk storage for bitmap
 * - changes to allow various bitmap chunk sizes
 */

/*
 * Still to do:
 *
 * flush after percent set rather than just time based. (maybe both).
 */

#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/timer.h>
#include <linux/sched.h>
#include <linux/list.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/buffer_head.h>
#include <linux/seq_file.h>
#include <trace/events/block.h>
#include "md.h"
#include "md-bitmap.h"

#define BITMAP_MAJOR_LO 3
/* version 4 insists the bitmap is in little-endian order
 * with version 3, it is host-endian which is non-portable
 * Version 5 is currently set only for clustered devices
 */
#define BITMAP_MAJOR_HI 4
#define BITMAP_MAJOR_CLUSTERED 5
#define BITMAP_MAJOR_HOSTENDIAN 3

/*
 * in-memory bitmap:
 *
 * Use 16 bit block counters to track pending writes to each "chunk".
 * The 2 high order bits are special-purpose, the first is a flag indicating
 * whether a resync is needed.  The second is a flag indicating whether a
 * resync is active.
 * This means that the counter is actually 14 bits:
 *
 * +--------+--------+------------------------------------------------+
 * | resync | resync |               counter                          |
 * | needed | active |                                                |
 * |  (0-1) |  (0-1) |              (0-16383)                         |
 * +--------+--------+------------------------------------------------+
 *
 * The "resync needed" bit is set when:
 *    a '1' bit is read from storage at startup.
 *    a write request fails on some drives
 *    a resync is aborted on a chunk with 'resync active' set
 * It is cleared (and resync-active set) when a resync starts across all drives
 * of the chunk.
 *
 *
 * The "resync active" bit is set when:
 *    a resync is started on all drives, and resync_needed is set.
 *       resync_needed will be cleared (as long as resync_active wasn't already set).
 * It is cleared when a resync completes.
 *
 * The counter counts pending write requests, plus the on-disk bit.
 * When the counter is '1' and the resync bits are clear, the on-disk
 * bit can be cleared as well, thus setting the counter to 0.
 * When we set a bit, or in the counter (to start a write), if the fields is
 * 0, we first set the disk bit and set the counter to 1.
 *
 * If the counter is 0, the on-disk bit is clear and the stripe is clean
 * Anything that dirties the stripe pushes the counter to 2 (at least)
 * and sets the on-disk bit (lazily).
 * If a periodic sweep find the counter at 2, it is decremented to 1.
 * If the sweep find the counter at 1, the on-disk bit is cleared and the
 * counter goes to zero.
 *
 * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
 * counters as a fallback when "page" memory cannot be allocated:
 *
 * Normal case (page memory allocated):
 *
 *     page pointer (32-bit)
 *
 *     [ ] ------+
 *               |
 *               +-------> [   ][   ]..[   ] (4096 byte page == 2048 counters)
 *                          c1   c2    c2048
 *
 * Hijacked case (page memory allocation failed):
 *
 *     hijacked page pointer (32-bit)
 *
 *     [                  ][              ] (no page memory allocated)
 *      counter #1 (16-bit) counter #2 (16-bit)
 *
 */

#define PAGE_BITS (PAGE_SIZE << 3)
#define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)

#define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
#define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
#define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)

/* how many counters per page? */
#define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
/* same, except a shift value for more efficient bitops */
#define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
/* same, except a mask value for more efficient bitops */
#define PAGE_COUNTER_MASK  (PAGE_COUNTER_RATIO - 1)

#define BITMAP_BLOCK_SHIFT 9

/*
 * bitmap structures:
 */

/* the in-memory bitmap is represented by bitmap_pages */
struct bitmap_page {
        /*
         * map points to the actual memory page
         */
        char *map;
        /*
         * in emergencies (when map cannot be alloced), hijack the map
         * pointer and use it as two counters itself
         */
        unsigned int hijacked:1;
        /*
         * If any counter in this page is '1' or '2' - and so could be
         * cleared then that page is marked as 'pending'
         */
        unsigned int pending:1;
        /*
         * count of dirty bits on the page
         */
        unsigned int  count:30;
};

/* the main bitmap structure - one per mddev */
struct bitmap {

        struct bitmap_counts {
                spinlock_t lock;
                struct bitmap_page *bp;
                /* total number of pages in the bitmap */
                unsigned long pages;
                /* number of pages not yet allocated */
                unsigned long missing_pages;
                /* chunksize = 2^chunkshift (for bitops) */
                unsigned long chunkshift;
                /* total number of data chunks for the array */
                unsigned long chunks;
        } counts;

        struct mddev *mddev; /* the md device that the bitmap is for */

        __u64   events_cleared;
        int need_sync;

        struct bitmap_storage {
                /* backing disk file */
                struct file *file;
                /* cached copy of the bitmap file superblock */
                struct page *sb_page;
                unsigned long sb_index;
                /* list of cache pages for the file */
                struct page **filemap;
                /* attributes associated filemap pages */
                unsigned long *filemap_attr;
                /* number of pages in the file */
                unsigned long file_pages;
                /* total bytes in the bitmap */
                unsigned long bytes;
        } storage;

        unsigned long flags;

        int allclean;

        atomic_t behind_writes;
        /* highest actual value at runtime */
        unsigned long behind_writes_used;

        /*
         * the bitmap daemon - periodically wakes up and sweeps the bitmap
         * file, cleaning up bits and flushing out pages to disk as necessary
         */
        unsigned long daemon_lastrun; /* jiffies of last run */
        /*
         * when we lasted called end_sync to update bitmap with resync
         * progress.
         */
        unsigned long last_end_sync;

        /* pending writes to the bitmap file */
        atomic_t pending_writes;
        wait_queue_head_t write_wait;
        wait_queue_head_t overflow_wait;
        wait_queue_head_t behind_wait;

        struct kernfs_node *sysfs_can_clear;
        /* slot offset for clustered env */
        int cluster_slot;
};

static int __bitmap_resize(struct bitmap *bitmap, sector_t blocks,
                           int chunksize, bool init);

static inline char *bmname(struct bitmap *bitmap)
{
        return bitmap->mddev ? mdname(bitmap->mddev) : "mdX";
}

static bool __bitmap_enabled(struct bitmap *bitmap)
{
        return bitmap->storage.filemap &&
               !test_bit(BITMAP_STALE, &bitmap->flags);
}

static bool bitmap_enabled(struct mddev *mddev)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return false;

        return __bitmap_enabled(bitmap);
}

/*
 * check a page and, if necessary, allocate it (or hijack it if the alloc fails)
 *
 * 1) check to see if this page is allocated, if it's not then try to alloc
 * 2) if the alloc fails, set the page's hijacked flag so we'll use the
 *    page pointer directly as a counter
 *
 * if we find our page, we increment the page's refcount so that it stays
 * allocated while we're using it
 */
static int md_bitmap_checkpage(struct bitmap_counts *bitmap,
                               unsigned long page, int create, int no_hijack)
__releases(bitmap->lock)
__acquires(bitmap->lock)
{
        unsigned char *mappage;

        WARN_ON_ONCE(page >= bitmap->pages);
        if (bitmap->bp[page].hijacked) /* it's hijacked, don't try to alloc */
                return 0;

        if (bitmap->bp[page].map) /* page is already allocated, just return */
                return 0;

        if (!create)
                return -ENOENT;

        /* this page has not been allocated yet */

        spin_unlock_irq(&bitmap->lock);
        /* It is possible that this is being called inside a
         * prepare_to_wait/finish_wait loop from raid5c:make_request().
         * In general it is not permitted to sleep in that context as it
         * can cause the loop to spin freely.
         * That doesn't apply here as we can only reach this point
         * once with any loop.
         * When this function completes, either bp[page].map or
         * bp[page].hijacked.  In either case, this function will
         * abort before getting to this point again.  So there is
         * no risk of a free-spin, and so it is safe to assert
         * that sleeping here is allowed.
         */
        sched_annotate_sleep();
        mappage = kzalloc(PAGE_SIZE, GFP_NOIO);
        spin_lock_irq(&bitmap->lock);

        if (mappage == NULL) {
                pr_debug("md/bitmap: map page allocation failed, hijacking\n");
                /* We don't support hijack for cluster raid */
                if (no_hijack)
                        return -ENOMEM;
                /* failed - set the hijacked flag so that we can use the
                 * pointer as a counter */
                if (!bitmap->bp[page].map)
                        bitmap->bp[page].hijacked = 1;
        } else if (bitmap->bp[page].map ||
                   bitmap->bp[page].hijacked) {
                /* somebody beat us to getting the page */
                kfree(mappage);
        } else {

                /* no page was in place and we have one, so install it */

                bitmap->bp[page].map = mappage;
                bitmap->missing_pages--;
        }
        return 0;
}

/* if page is completely empty, put it back on the free list, or dealloc it */
/* if page was hijacked, unmark the flag so it might get alloced next time */
/* Note: lock should be held when calling this */
static void md_bitmap_checkfree(struct bitmap_counts *bitmap, unsigned long page)
{
        char *ptr;

        if (bitmap->bp[page].count) /* page is still busy */
                return;

        /* page is no longer in use, it can be released */

        if (bitmap->bp[page].hijacked) { /* page was hijacked, undo this now */
                bitmap->bp[page].hijacked = 0;
                bitmap->bp[page].map = NULL;
        } else {
                /* normal case, free the page */
                ptr = bitmap->bp[page].map;
                bitmap->bp[page].map = NULL;
                bitmap->missing_pages++;
                kfree(ptr);
        }
}

/*
 * bitmap file handling - read and write the bitmap file and its superblock
 */

/*
 * basic page I/O operations
 */

/* IO operations when bitmap is stored near all superblocks */

/* choose a good rdev and read the page from there */
static int read_sb_page(struct mddev *mddev, loff_t offset,
                struct page *page, unsigned long index, int size)
{

        sector_t sector = mddev->bitmap_info.offset + offset +
                index * (PAGE_SIZE / SECTOR_SIZE);
        struct md_rdev *rdev;

        rdev_for_each(rdev, mddev) {
                u32 iosize = roundup(size, bdev_logical_block_size(rdev->bdev));

                if (!test_bit(In_sync, &rdev->flags) ||
                    test_bit(Faulty, &rdev->flags) ||
                    test_bit(Bitmap_sync, &rdev->flags))
                        continue;

                if (sync_page_io(rdev, sector, iosize, page, REQ_OP_READ, true))
                        return 0;
        }
        return -EIO;
}

static struct md_rdev *next_active_rdev(struct md_rdev *rdev, struct mddev *mddev)
{
        /* Iterate the disks of an mddev, using rcu to protect access to the
         * linked list, and raising the refcount of devices we return to ensure
         * they don't disappear while in use.
         * As devices are only added or removed when raid_disk is < 0 and
         * nr_pending is 0 and In_sync is clear, the entries we return will
         * still be in the same position on the list when we re-enter
         * list_for_each_entry_continue_rcu.
         *
         * Note that if entered with 'rdev == NULL' to start at the
         * beginning, we temporarily assign 'rdev' to an address which
         * isn't really an rdev, but which can be used by
         * list_for_each_entry_continue_rcu() to find the first entry.
         */
        rcu_read_lock();
        if (rdev == NULL)
                /* start at the beginning */
                rdev = list_entry(&mddev->disks, struct md_rdev, same_set);
        else {
                /* release the previous rdev and start from there. */
                rdev_dec_pending(rdev, mddev);
        }
        list_for_each_entry_continue_rcu(rdev, &mddev->disks, same_set) {
                if (rdev->raid_disk >= 0 &&
                    !test_bit(Faulty, &rdev->flags)) {
                        /* this is a usable devices */
                        atomic_inc(&rdev->nr_pending);
                        rcu_read_unlock();
                        return rdev;
                }
        }
        rcu_read_unlock();
        return NULL;
}

static unsigned int optimal_io_size(struct block_device *bdev,
                                    unsigned int last_page_size,
                                    unsigned int io_size)
{
        if (bdev_io_opt(bdev) > bdev_logical_block_size(bdev))
                return roundup(last_page_size, bdev_io_opt(bdev));
        return io_size;
}

static unsigned int bitmap_io_size(unsigned int io_size, unsigned int opt_size,
                                   loff_t start, loff_t boundary)
{
        if (io_size != opt_size &&
            start + opt_size / SECTOR_SIZE <= boundary)
                return opt_size;
        if (start + io_size / SECTOR_SIZE <= boundary)
                return io_size;

        /* Overflows boundary */
        return 0;
}

static int __write_sb_page(struct md_rdev *rdev, struct bitmap *bitmap,
                           unsigned long pg_index, struct page *page)
{
        struct block_device *bdev;
        struct mddev *mddev = bitmap->mddev;
        struct bitmap_storage *store = &bitmap->storage;
        unsigned int bitmap_limit = (bitmap->storage.file_pages - pg_index) <<
                PAGE_SHIFT;
        loff_t sboff, offset = mddev->bitmap_info.offset;
        sector_t ps = pg_index * PAGE_SIZE / SECTOR_SIZE;
        unsigned int size = PAGE_SIZE;
        unsigned int opt_size = PAGE_SIZE;
        sector_t doff;

        bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;
        /* we compare length (page numbers), not page offset. */
        if ((pg_index - store->sb_index) == store->file_pages - 1) {
                unsigned int last_page_size = store->bytes & (PAGE_SIZE - 1);

                if (last_page_size == 0)
                        last_page_size = PAGE_SIZE;
                size = roundup(last_page_size, bdev_logical_block_size(bdev));
                opt_size = optimal_io_size(bdev, last_page_size, size);
        }

        sboff = rdev->sb_start + offset;
        doff = rdev->data_offset;

        /* Just make sure we aren't corrupting data or metadata */
        if (mddev->external) {
                /* Bitmap could be anywhere. */
                if (sboff + ps > doff &&
                    sboff < (doff + mddev->dev_sectors + PAGE_SIZE / SECTOR_SIZE))
                        return -EINVAL;
        } else if (offset < 0) {
                /* DATA  BITMAP METADATA  */
                size = bitmap_io_size(size, opt_size, offset + ps, 0);
                if (size == 0)
                        /* bitmap runs in to metadata */
                        return -EINVAL;

                if (doff + mddev->dev_sectors > sboff)
                        /* data runs in to bitmap */
                        return -EINVAL;
        } else if (rdev->sb_start < rdev->data_offset) {
                /* METADATA BITMAP DATA */
                size = bitmap_io_size(size, opt_size, sboff + ps, doff);
                if (size == 0)
                        /* bitmap runs in to data */
                        return -EINVAL;
        }

        md_super_write(mddev, rdev, sboff + ps, (int)min(size, bitmap_limit), page);
        return 0;
}

static void write_sb_page(struct bitmap *bitmap, unsigned long pg_index,
                          struct page *page, bool wait)
{
        struct mddev *mddev = bitmap->mddev;

        do {
                struct md_rdev *rdev = NULL;

                while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
                        if (__write_sb_page(rdev, bitmap, pg_index, page) < 0) {
                                set_bit(BITMAP_WRITE_ERROR, &bitmap->flags);
                                return;
                        }
                }
        } while (wait && md_super_wait(mddev) < 0);
}

static void md_bitmap_file_kick(struct bitmap *bitmap);

#ifdef CONFIG_MD_BITMAP_FILE
static void write_file_page(struct bitmap *bitmap, struct page *page, int wait)
{
        struct buffer_head *bh = page_buffers(page);

        while (bh && bh->b_blocknr) {
                atomic_inc(&bitmap->pending_writes);
                set_buffer_locked(bh);
                set_buffer_mapped(bh);
                submit_bh(REQ_OP_WRITE | REQ_SYNC, bh);
                bh = bh->b_this_page;
        }

        if (wait)
                wait_event(bitmap->write_wait,
                           atomic_read(&bitmap->pending_writes) == 0);
}

static void end_bitmap_write(struct buffer_head *bh, int uptodate)
{
        struct bitmap *bitmap = bh->b_private;

        if (!uptodate)
                set_bit(BITMAP_WRITE_ERROR, &bitmap->flags);
        if (atomic_dec_and_test(&bitmap->pending_writes))
                wake_up(&bitmap->write_wait);
}

static void free_buffers(struct page *page)
{
        struct buffer_head *bh;

        if (!PagePrivate(page))
                return;

        bh = page_buffers(page);
        while (bh) {
                struct buffer_head *next = bh->b_this_page;
                free_buffer_head(bh);
                bh = next;
        }
        detach_page_private(page);
        put_page(page);
}

/* read a page from a file.
 * We both read the page, and attach buffers to the page to record the
 * address of each block (using bmap).  These addresses will be used
 * to write the block later, completely bypassing the filesystem.
 * This usage is similar to how swap files are handled, and allows us
 * to write to a file with no concerns of memory allocation failing.
 */
static int read_file_page(struct file *file, unsigned long index,
                struct bitmap *bitmap, unsigned long count, struct page *page)
{
        int ret = 0;
        struct inode *inode = file_inode(file);
        struct buffer_head *bh;
        sector_t block, blk_cur;
        unsigned long blocksize = i_blocksize(inode);

        pr_debug("read bitmap file (%dB @ %llu)\n", (int)PAGE_SIZE,
                 (unsigned long long)index << PAGE_SHIFT);

        bh = alloc_page_buffers(page, blocksize);
        if (!bh) {
                ret = -ENOMEM;
                goto out;
        }
        attach_page_private(page, bh);
        blk_cur = index << (PAGE_SHIFT - inode->i_blkbits);
        while (bh) {
                block = blk_cur;

                if (count == 0)
                        bh->b_blocknr = 0;
                else {
                        ret = bmap(inode, &block);
                        if (ret || !block) {
                                ret = -EINVAL;
                                bh->b_blocknr = 0;
                                goto out;
                        }

                        bh->b_blocknr = block;
                        bh->b_bdev = inode->i_sb->s_bdev;
                        if (count < blocksize)
                                count = 0;
                        else
                                count -= blocksize;

                        bh->b_end_io = end_bitmap_write;
                        bh->b_private = bitmap;
                        atomic_inc(&bitmap->pending_writes);
                        set_buffer_locked(bh);
                        set_buffer_mapped(bh);
                        submit_bh(REQ_OP_READ, bh);
                }
                blk_cur++;
                bh = bh->b_this_page;
        }

        wait_event(bitmap->write_wait,
                   atomic_read(&bitmap->pending_writes)==0);
        if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
                ret = -EIO;
out:
        if (ret)
                pr_err("md: bitmap read error: (%dB @ %llu): %d\n",
                       (int)PAGE_SIZE,
                       (unsigned long long)index << PAGE_SHIFT,
                       ret);
        return ret;
}
#else /* CONFIG_MD_BITMAP_FILE */
static void write_file_page(struct bitmap *bitmap, struct page *page, int wait)
{
}
static int read_file_page(struct file *file, unsigned long index,
                struct bitmap *bitmap, unsigned long count, struct page *page)
{
        return -EIO;
}
static void free_buffers(struct page *page)
{
        put_page(page);
}
#endif /* CONFIG_MD_BITMAP_FILE */

/*
 * bitmap file superblock operations
 */

/*
 * write out a page to a file
 */
static void filemap_write_page(struct bitmap *bitmap, unsigned long pg_index,
                               bool wait)
{
        struct bitmap_storage *store = &bitmap->storage;
        struct page *page = store->filemap[pg_index];

        if (mddev_is_clustered(bitmap->mddev)) {
                /* go to node bitmap area starting point */
                pg_index += store->sb_index;
        }

        if (store->file)
                write_file_page(bitmap, page, wait);
        else
                write_sb_page(bitmap, pg_index, page, wait);
}

/*
 * md_bitmap_wait_writes() should be called before writing any bitmap
 * blocks, to ensure previous writes, particularly from
 * md_bitmap_daemon_work(), have completed.
 */
static void md_bitmap_wait_writes(struct bitmap *bitmap)
{
        if (bitmap->storage.file)
                wait_event(bitmap->write_wait,
                           atomic_read(&bitmap->pending_writes)==0);
        else
                /* Note that we ignore the return value.  The writes
                 * might have failed, but that would just mean that
                 * some bits which should be cleared haven't been,
                 * which is safe.  The relevant bitmap blocks will
                 * probably get written again, but there is no great
                 * loss if they aren't.
                 */
                md_super_wait(bitmap->mddev);
}


/* update the event counter and sync the superblock to disk */
static void bitmap_update_sb(void *data)
{
        bitmap_super_t *sb;
        struct bitmap *bitmap = data;

        if (!bitmap || !bitmap->mddev) /* no bitmap for this array */
                return;
        if (bitmap->mddev->bitmap_info.external)
                return;
        if (!bitmap->storage.sb_page) /* no superblock */
                return;
        sb = kmap_atomic(bitmap->storage.sb_page);
        sb->events = cpu_to_le64(bitmap->mddev->events);
        if (bitmap->mddev->events < bitmap->events_cleared)
                /* rocking back to read-only */
                bitmap->events_cleared = bitmap->mddev->events;
        sb->events_cleared = cpu_to_le64(bitmap->events_cleared);
        /*
         * clear BITMAP_WRITE_ERROR bit to protect against the case that
         * a bitmap write error occurred but the later writes succeeded.
         */
        sb->state = cpu_to_le32(bitmap->flags & ~BIT(BITMAP_WRITE_ERROR));
        /* Just in case these have been changed via sysfs: */
        sb->daemon_sleep = cpu_to_le32(bitmap->mddev->bitmap_info.daemon_sleep/HZ);
        sb->write_behind = cpu_to_le32(bitmap->mddev->bitmap_info.max_write_behind);
        /* This might have been changed by a reshape */
        sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);
        sb->chunksize = cpu_to_le32(bitmap->mddev->bitmap_info.chunksize);
        sb->nodes = cpu_to_le32(bitmap->mddev->bitmap_info.nodes);
        sb->sectors_reserved = cpu_to_le32(bitmap->mddev->
                                           bitmap_info.space);
        kunmap_atomic(sb);

        if (bitmap->storage.file)
                write_file_page(bitmap, bitmap->storage.sb_page, 1);
        else
                write_sb_page(bitmap, bitmap->storage.sb_index,
                              bitmap->storage.sb_page, 1);
}

static void bitmap_print_sb(struct bitmap *bitmap)
{
        bitmap_super_t *sb;

        if (!bitmap || !bitmap->storage.sb_page)
                return;
        sb = kmap_atomic(bitmap->storage.sb_page);
        pr_debug("%s: bitmap file superblock:\n", bmname(bitmap));
        pr_debug("         magic: %08x\n", le32_to_cpu(sb->magic));
        pr_debug("       version: %u\n", le32_to_cpu(sb->version));
        pr_debug("          uuid: %08x.%08x.%08x.%08x\n",
                 le32_to_cpu(*(__le32 *)(sb->uuid+0)),
                 le32_to_cpu(*(__le32 *)(sb->uuid+4)),
                 le32_to_cpu(*(__le32 *)(sb->uuid+8)),
                 le32_to_cpu(*(__le32 *)(sb->uuid+12)));
        pr_debug("        events: %llu\n",
                 (unsigned long long) le64_to_cpu(sb->events));
        pr_debug("events cleared: %llu\n",
                 (unsigned long long) le64_to_cpu(sb->events_cleared));
        pr_debug("         state: %08x\n", le32_to_cpu(sb->state));
        pr_debug("     chunksize: %u B\n", le32_to_cpu(sb->chunksize));
        pr_debug("  daemon sleep: %us\n", le32_to_cpu(sb->daemon_sleep));
        pr_debug("     sync size: %llu KB\n",
                 (unsigned long long)le64_to_cpu(sb->sync_size)/2);
        pr_debug("max write behind: %u\n", le32_to_cpu(sb->write_behind));
        kunmap_atomic(sb);
}

/*
 * bitmap_new_disk_sb
 * @bitmap
 *
 * This function is somewhat the reverse of bitmap_read_sb.  bitmap_read_sb
 * reads and verifies the on-disk bitmap superblock and populates bitmap_info.
 * This function verifies 'bitmap_info' and populates the on-disk bitmap
 * structure, which is to be written to disk.
 *
 * Returns: 0 on success, -Exxx on error
 */
static int md_bitmap_new_disk_sb(struct bitmap *bitmap)
{
        bitmap_super_t *sb;
        unsigned long chunksize, daemon_sleep, write_behind;

        bitmap->storage.sb_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
        if (bitmap->storage.sb_page == NULL)
                return -ENOMEM;
        bitmap->storage.sb_index = 0;

        sb = kmap_atomic(bitmap->storage.sb_page);

        sb->magic = cpu_to_le32(BITMAP_MAGIC);
        sb->version = cpu_to_le32(BITMAP_MAJOR_HI);

        chunksize = bitmap->mddev->bitmap_info.chunksize;
        BUG_ON(!chunksize);
        if (!is_power_of_2(chunksize)) {
                kunmap_atomic(sb);
                pr_warn("bitmap chunksize not a power of 2\n");
                return -EINVAL;
        }
        sb->chunksize = cpu_to_le32(chunksize);

        daemon_sleep = bitmap->mddev->bitmap_info.daemon_sleep;
        if (!daemon_sleep || (daemon_sleep > MAX_SCHEDULE_TIMEOUT)) {
                pr_debug("Choosing daemon_sleep default (5 sec)\n");
                daemon_sleep = 5 * HZ;
        }
        sb->daemon_sleep = cpu_to_le32(daemon_sleep);
        bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;

        /*
         * FIXME: write_behind for RAID1.  If not specified, what
         * is a good choice?  We choose COUNTER_MAX / 2 arbitrarily.
         */
        write_behind = bitmap->mddev->bitmap_info.max_write_behind;
        if (write_behind > COUNTER_MAX)
                write_behind = COUNTER_MAX / 2;
        sb->write_behind = cpu_to_le32(write_behind);
        bitmap->mddev->bitmap_info.max_write_behind = write_behind;

        /* keep the array size field of the bitmap superblock up to date */
        sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);

        memcpy(sb->uuid, bitmap->mddev->uuid, 16);

        set_bit(BITMAP_STALE, &bitmap->flags);
        sb->state = cpu_to_le32(bitmap->flags);
        bitmap->events_cleared = bitmap->mddev->events;
        sb->events_cleared = cpu_to_le64(bitmap->mddev->events);
        bitmap->mddev->bitmap_info.nodes = 0;

        kunmap_atomic(sb);

        return 0;
}

/* read the superblock from the bitmap file and initialize some bitmap fields */
static int md_bitmap_read_sb(struct bitmap *bitmap)
{
        char *reason = NULL;
        bitmap_super_t *sb;
        unsigned long chunksize, daemon_sleep, write_behind;
        unsigned long long events;
        int nodes = 0;
        unsigned long sectors_reserved = 0;
        int err = -EINVAL;
        struct page *sb_page;
        loff_t offset = 0;

        if (!bitmap->storage.file && !bitmap->mddev->bitmap_info.offset) {
                chunksize = 128 * 1024 * 1024;
                daemon_sleep = 5 * HZ;
                write_behind = 0;
                set_bit(BITMAP_STALE, &bitmap->flags);
                err = 0;
                goto out_no_sb;
        }
        /* page 0 is the superblock, read it... */
        sb_page = alloc_page(GFP_KERNEL);
        if (!sb_page)
                return -ENOMEM;
        bitmap->storage.sb_page = sb_page;

re_read:
        /* If cluster_slot is set, the cluster is setup */
        if (bitmap->cluster_slot >= 0) {
                sector_t bm_blocks = bitmap->mddev->resync_max_sectors;

                bm_blocks = DIV_ROUND_UP_SECTOR_T(bm_blocks,
                           (bitmap->mddev->bitmap_info.chunksize >> 9));
                /* bits to bytes */
                bm_blocks = ((bm_blocks+7) >> 3) + sizeof(bitmap_super_t);
                /* to 4k blocks */
                bm_blocks = DIV_ROUND_UP_SECTOR_T(bm_blocks, 4096);
                offset = bitmap->cluster_slot * (bm_blocks << 3);
                pr_debug("%s:%d bm slot: %d offset: %llu\n", __func__, __LINE__,
                        bitmap->cluster_slot, offset);
        }

        if (bitmap->storage.file) {
                loff_t isize = i_size_read(bitmap->storage.file->f_mapping->host);
                int bytes = isize > PAGE_SIZE ? PAGE_SIZE : isize;

                err = read_file_page(bitmap->storage.file, 0,
                                bitmap, bytes, sb_page);
        } else {
                err = read_sb_page(bitmap->mddev, offset, sb_page, 0,
                                   sizeof(bitmap_super_t));
        }
        if (err)
                return err;

        err = -EINVAL;
        sb = kmap_atomic(sb_page);

        chunksize = le32_to_cpu(sb->chunksize);
        daemon_sleep = le32_to_cpu(sb->daemon_sleep) * HZ;
        write_behind = le32_to_cpu(sb->write_behind);
        sectors_reserved = le32_to_cpu(sb->sectors_reserved);

        /* verify that the bitmap-specific fields are valid */
        if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
                reason = "bad magic";
        else if (le32_to_cpu(sb->version) < BITMAP_MAJOR_LO ||
                 le32_to_cpu(sb->version) > BITMAP_MAJOR_CLUSTERED)
                reason = "unrecognized superblock version";
        else if (chunksize < 512)
                reason = "bitmap chunksize too small";
        else if (!is_power_of_2(chunksize))
                reason = "bitmap chunksize not a power of 2";
        else if (daemon_sleep < 1 || daemon_sleep > MAX_SCHEDULE_TIMEOUT)
                reason = "daemon sleep period out of range";
        else if (write_behind > COUNTER_MAX)
                reason = "write-behind limit out of range (0 - 16383)";
        if (reason) {
                pr_warn("%s: invalid bitmap file superblock: %s\n",
                        bmname(bitmap), reason);
                goto out;
        }

        /*
         * Setup nodes/clustername only if bitmap version is
         * cluster-compatible
         */
        if (sb->version == cpu_to_le32(BITMAP_MAJOR_CLUSTERED)) {
                nodes = le32_to_cpu(sb->nodes);
                strscpy(bitmap->mddev->bitmap_info.cluster_name,
                                sb->cluster_name, 64);
        }

        /* keep the array size field of the bitmap superblock up to date */
        sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);

        if (bitmap->mddev->persistent) {
                /*
                 * We have a persistent array superblock, so compare the
                 * bitmap's UUID and event counter to the mddev's
                 */
                if (memcmp(sb->uuid, bitmap->mddev->uuid, 16)) {
                        pr_warn("%s: bitmap superblock UUID mismatch\n",
                                bmname(bitmap));
                        goto out;
                }
                events = le64_to_cpu(sb->events);
                if (!nodes && (events < bitmap->mddev->events)) {
                        pr_warn("%s: bitmap file is out of date (%llu < %llu) -- forcing full recovery\n",
                                bmname(bitmap), events,
                                (unsigned long long) bitmap->mddev->events);
                        set_bit(BITMAP_STALE, &bitmap->flags);
                }
        }

        /* assign fields using values from superblock */
        bitmap->flags |= le32_to_cpu(sb->state);
        if (le32_to_cpu(sb->version) == BITMAP_MAJOR_HOSTENDIAN)
                set_bit(BITMAP_HOSTENDIAN, &bitmap->flags);
        bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
        err = 0;

out:
        kunmap_atomic(sb);
        if (err == 0 && nodes && (bitmap->cluster_slot < 0)) {
                /* Assigning chunksize is required for "re_read" */
                bitmap->mddev->bitmap_info.chunksize = chunksize;
                err = md_setup_cluster(bitmap->mddev, nodes);
                if (err) {
                        pr_warn("%s: Could not setup cluster service (%d)\n",
                                bmname(bitmap), err);
                        goto out_no_sb;
                }
                bitmap->cluster_slot = md_cluster_ops->slot_number(bitmap->mddev);
                goto re_read;
        }

out_no_sb:
        if (err == 0) {
                if (test_bit(BITMAP_STALE, &bitmap->flags))
                        bitmap->events_cleared = bitmap->mddev->events;
                bitmap->mddev->bitmap_info.chunksize = chunksize;
                bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
                bitmap->mddev->bitmap_info.max_write_behind = write_behind;
                bitmap->mddev->bitmap_info.nodes = nodes;
                if (bitmap->mddev->bitmap_info.space == 0 ||
                        bitmap->mddev->bitmap_info.space > sectors_reserved)
                        bitmap->mddev->bitmap_info.space = sectors_reserved;
        } else {
                bitmap_print_sb(bitmap);
                if (bitmap->cluster_slot < 0)
                        md_cluster_stop(bitmap->mddev);
        }
        return err;
}

/*
 * general bitmap file operations
 */

/*
 * on-disk bitmap:
 *
 * Use one bit per "chunk" (block set). We do the disk I/O on the bitmap
 * file a page at a time. There's a superblock at the start of the file.
 */
/* calculate the index of the page that contains this bit */
static inline unsigned long file_page_index(struct bitmap_storage *store,
                                            unsigned long chunk)
{
        if (store->sb_page)
                chunk += sizeof(bitmap_super_t) << 3;
        return chunk >> PAGE_BIT_SHIFT;
}

/* calculate the (bit) offset of this bit within a page */
static inline unsigned long file_page_offset(struct bitmap_storage *store,
                                             unsigned long chunk)
{
        if (store->sb_page)
                chunk += sizeof(bitmap_super_t) << 3;
        return chunk & (PAGE_BITS - 1);
}

/*
 * return a pointer to the page in the filemap that contains the given bit
 *
 */
static inline struct page *filemap_get_page(struct bitmap_storage *store,
                                            unsigned long chunk)
{
        if (file_page_index(store, chunk) >= store->file_pages)
                return NULL;
        return store->filemap[file_page_index(store, chunk)];
}

static int md_bitmap_storage_alloc(struct bitmap_storage *store,
                                   unsigned long chunks, int with_super,
                                   int slot_number)
{
        int pnum, offset = 0;
        unsigned long num_pages;
        unsigned long bytes;

        bytes = DIV_ROUND_UP(chunks, 8);
        if (with_super)
                bytes += sizeof(bitmap_super_t);

        num_pages = DIV_ROUND_UP(bytes, PAGE_SIZE);
        offset = slot_number * num_pages;

        store->filemap = kmalloc_array(num_pages, sizeof(struct page *),
                                       GFP_KERNEL);
        if (!store->filemap)
                return -ENOMEM;

        if (with_super && !store->sb_page) {
                store->sb_page = alloc_page(GFP_KERNEL|__GFP_ZERO);
                if (store->sb_page == NULL)
                        return -ENOMEM;
        }

        pnum = 0;
        if (store->sb_page) {
                store->filemap[0] = store->sb_page;
                pnum = 1;
                store->sb_index = offset;
        }

        for ( ; pnum < num_pages; pnum++) {
                store->filemap[pnum] = alloc_page(GFP_KERNEL|__GFP_ZERO);
                if (!store->filemap[pnum]) {
                        store->file_pages = pnum;
                        return -ENOMEM;
                }
        }
        store->file_pages = pnum;

        /* We need 4 bits per page, rounded up to a multiple
         * of sizeof(unsigned long) */
        store->filemap_attr = kzalloc(
                roundup(DIV_ROUND_UP(num_pages*4, 8), sizeof(unsigned long)),
                GFP_KERNEL);
        if (!store->filemap_attr)
                return -ENOMEM;

        store->bytes = bytes;

        return 0;
}

static void md_bitmap_file_unmap(struct bitmap_storage *store)
{
        struct file *file = store->file;
        struct page *sb_page = store->sb_page;
        struct page **map = store->filemap;
        int pages = store->file_pages;

        while (pages--)
                if (map[pages] != sb_page) /* 0 is sb_page, release it below */
                        free_buffers(map[pages]);
        kfree(map);
        kfree(store->filemap_attr);

        if (sb_page)
                free_buffers(sb_page);

        if (file) {
                struct inode *inode = file_inode(file);
                invalidate_mapping_pages(inode->i_mapping, 0, -1);
                fput(file);
        }
}

/*
 * bitmap_file_kick - if an error occurs while manipulating the bitmap file
 * then it is no longer reliable, so we stop using it and we mark the file
 * as failed in the superblock
 */
static void md_bitmap_file_kick(struct bitmap *bitmap)
{
        if (!test_and_set_bit(BITMAP_STALE, &bitmap->flags)) {
                bitmap_update_sb(bitmap);

                if (bitmap->storage.file) {
                        pr_warn("%s: kicking failed bitmap file %pD4 from array!\n",
                                bmname(bitmap), bitmap->storage.file);

                } else
                        pr_warn("%s: disabling internal bitmap due to errors\n",
                                bmname(bitmap));
        }
}

enum bitmap_page_attr {
        BITMAP_PAGE_DIRTY = 0,     /* there are set bits that need to be synced */
        BITMAP_PAGE_PENDING = 1,   /* there are bits that are being cleaned.
                                    * i.e. counter is 1 or 2. */
        BITMAP_PAGE_NEEDWRITE = 2, /* there are cleared bits that need to be synced */
};

static inline void set_page_attr(struct bitmap *bitmap, int pnum,
                                 enum bitmap_page_attr attr)
{
        set_bit((pnum<<2) + attr, bitmap->storage.filemap_attr);
}

static inline void clear_page_attr(struct bitmap *bitmap, int pnum,
                                   enum bitmap_page_attr attr)
{
        clear_bit((pnum<<2) + attr, bitmap->storage.filemap_attr);
}

static inline int test_page_attr(struct bitmap *bitmap, int pnum,
                                 enum bitmap_page_attr attr)
{
        return test_bit((pnum<<2) + attr, bitmap->storage.filemap_attr);
}

static inline int test_and_clear_page_attr(struct bitmap *bitmap, int pnum,
                                           enum bitmap_page_attr attr)
{
        return test_and_clear_bit((pnum<<2) + attr,
                                  bitmap->storage.filemap_attr);
}
/*
 * bitmap_file_set_bit -- called before performing a write to the md device
 * to set (and eventually sync) a particular bit in the bitmap file
 *
 * we set the bit immediately, then we record the page number so that
 * when an unplug occurs, we can flush the dirty pages out to disk
 */
static void md_bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
{
        unsigned long bit;
        struct page *page;
        void *kaddr;
        unsigned long chunk = block >> bitmap->counts.chunkshift;
        struct bitmap_storage *store = &bitmap->storage;
        unsigned long index = file_page_index(store, chunk);
        unsigned long node_offset = 0;

        index += store->sb_index;
        if (mddev_is_clustered(bitmap->mddev))
                node_offset = bitmap->cluster_slot * store->file_pages;

        page = filemap_get_page(&bitmap->storage, chunk);
        if (!page)
                return;
        bit = file_page_offset(&bitmap->storage, chunk);

        /* set the bit */
        kaddr = kmap_atomic(page);
        if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
                set_bit(bit, kaddr);
        else
                set_bit_le(bit, kaddr);
        kunmap_atomic(kaddr);
        pr_debug("set file bit %lu page %lu\n", bit, index);
        /* record page number so it gets flushed to disk when unplug occurs */
        set_page_attr(bitmap, index - node_offset, BITMAP_PAGE_DIRTY);
}

static void md_bitmap_file_clear_bit(struct bitmap *bitmap, sector_t block)
{
        unsigned long bit;
        struct page *page;
        void *paddr;
        unsigned long chunk = block >> bitmap->counts.chunkshift;
        struct bitmap_storage *store = &bitmap->storage;
        unsigned long index = file_page_index(store, chunk);
        unsigned long node_offset = 0;

        index += store->sb_index;
        if (mddev_is_clustered(bitmap->mddev))
                node_offset = bitmap->cluster_slot * store->file_pages;

        page = filemap_get_page(&bitmap->storage, chunk);
        if (!page)
                return;
        bit = file_page_offset(&bitmap->storage, chunk);
        paddr = kmap_atomic(page);
        if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
                clear_bit(bit, paddr);
        else
                clear_bit_le(bit, paddr);
        kunmap_atomic(paddr);
        if (!test_page_attr(bitmap, index - node_offset, BITMAP_PAGE_NEEDWRITE)) {
                set_page_attr(bitmap, index - node_offset, BITMAP_PAGE_PENDING);
                bitmap->allclean = 0;
        }
}

static int md_bitmap_file_test_bit(struct bitmap *bitmap, sector_t block)
{
        unsigned long bit;
        struct page *page;
        void *paddr;
        unsigned long chunk = block >> bitmap->counts.chunkshift;
        int set = 0;

        page = filemap_get_page(&bitmap->storage, chunk);
        if (!page)
                return -EINVAL;
        bit = file_page_offset(&bitmap->storage, chunk);
        paddr = kmap_atomic(page);
        if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
                set = test_bit(bit, paddr);
        else
                set = test_bit_le(bit, paddr);
        kunmap_atomic(paddr);
        return set;
}

/* this gets called when the md device is ready to unplug its underlying
 * (slave) device queues -- before we let any writes go down, we need to
 * sync the dirty pages of the bitmap file to disk */
static void __bitmap_unplug(struct bitmap *bitmap)
{
        unsigned long i;
        int dirty, need_write;
        int writing = 0;

        if (!__bitmap_enabled(bitmap))
                return;

        /* look at each page to see if there are any set bits that need to be
         * flushed out to disk */
        for (i = 0; i < bitmap->storage.file_pages; i++) {
                dirty = test_and_clear_page_attr(bitmap, i, BITMAP_PAGE_DIRTY);
                need_write = test_and_clear_page_attr(bitmap, i,
                                                      BITMAP_PAGE_NEEDWRITE);
                if (dirty || need_write) {
                        if (!writing) {
                                md_bitmap_wait_writes(bitmap);
                                mddev_add_trace_msg(bitmap->mddev,
                                        "md bitmap_unplug");
                        }
                        clear_page_attr(bitmap, i, BITMAP_PAGE_PENDING);
                        filemap_write_page(bitmap, i, false);
                        writing = 1;
                }
        }
        if (writing)
                md_bitmap_wait_writes(bitmap);

        if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
                md_bitmap_file_kick(bitmap);
}

struct bitmap_unplug_work {
        struct work_struct work;
        struct bitmap *bitmap;
        struct completion *done;
};

static void md_bitmap_unplug_fn(struct work_struct *work)
{
        struct bitmap_unplug_work *unplug_work =
                container_of(work, struct bitmap_unplug_work, work);

        __bitmap_unplug(unplug_work->bitmap);
        complete(unplug_work->done);
}

static void bitmap_unplug_async(struct bitmap *bitmap)
{
        DECLARE_COMPLETION_ONSTACK(done);
        struct bitmap_unplug_work unplug_work;

        INIT_WORK_ONSTACK(&unplug_work.work, md_bitmap_unplug_fn);
        unplug_work.bitmap = bitmap;
        unplug_work.done = &done;

        queue_work(md_bitmap_wq, &unplug_work.work);
        wait_for_completion(&done);
}

static void bitmap_unplug(struct mddev *mddev, bool sync)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return;

        if (sync)
                __bitmap_unplug(bitmap);
        else
                bitmap_unplug_async(bitmap);
}

static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed);

/*
 * Initialize the in-memory bitmap from the on-disk bitmap and set up the memory
 * mapping of the bitmap file.
 *
 * Special case: If there's no bitmap file, or if the bitmap file had been
 * previously kicked from the array, we mark all the bits as 1's in order to
 * cause a full resync.
 *
 * We ignore all bits for sectors that end earlier than 'start'.
 * This is used when reading an out-of-date bitmap.
 */
static int md_bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
{
        bool outofdate = test_bit(BITMAP_STALE, &bitmap->flags);
        struct mddev *mddev = bitmap->mddev;
        unsigned long chunks = bitmap->counts.chunks;
        struct bitmap_storage *store = &bitmap->storage;
        struct file *file = store->file;
        unsigned long node_offset = 0;
        unsigned long bit_cnt = 0;
        unsigned long i;
        int ret;

        if (!file && !mddev->bitmap_info.offset) {
                /* No permanent bitmap - fill with '1s'. */
                store->filemap = NULL;
                store->file_pages = 0;
                for (i = 0; i < chunks ; i++) {
                        /* if the disk bit is set, set the memory bit */
                        int needed = ((sector_t)(i+1) << (bitmap->counts.chunkshift)
                                      >= start);
                        md_bitmap_set_memory_bits(bitmap,
                                                  (sector_t)i << bitmap->counts.chunkshift,
                                                  needed);
                }
                return 0;
        }

        if (file && i_size_read(file->f_mapping->host) < store->bytes) {
                pr_warn("%s: bitmap file too short %lu < %lu\n",
                        bmname(bitmap),
                        (unsigned long) i_size_read(file->f_mapping->host),
                        store->bytes);
                ret = -ENOSPC;
                goto err;
        }

        if (mddev_is_clustered(mddev))
                node_offset = bitmap->cluster_slot * (DIV_ROUND_UP(store->bytes, PAGE_SIZE));

        for (i = 0; i < store->file_pages; i++) {
                struct page *page = store->filemap[i];
                int count;

                /* unmap the old page, we're done with it */
                if (i == store->file_pages - 1)
                        count = store->bytes - i * PAGE_SIZE;
                else
                        count = PAGE_SIZE;

                if (file)
                        ret = read_file_page(file, i, bitmap, count, page);
                else
                        ret = read_sb_page(mddev, 0, page, i + node_offset,
                                           count);
                if (ret)
                        goto err;
        }

        if (outofdate) {
                pr_warn("%s: bitmap file is out of date, doing full recovery\n",
                        bmname(bitmap));

                for (i = 0; i < store->file_pages; i++) {
                        struct page *page = store->filemap[i];
                        unsigned long offset = 0;
                        void *paddr;

                        if (i == 0 && !mddev->bitmap_info.external)
                                offset = sizeof(bitmap_super_t);

                        /*
                         * If the bitmap is out of date, dirty the whole page
                         * and write it out
                         */
                        paddr = kmap_atomic(page);
                        memset(paddr + offset, 0xff, PAGE_SIZE - offset);
                        kunmap_atomic(paddr);

                        filemap_write_page(bitmap, i, true);
                        if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags)) {
                                ret = -EIO;
                                goto err;
                        }
                }
        }

        for (i = 0; i < chunks; i++) {
                struct page *page = filemap_get_page(&bitmap->storage, i);
                unsigned long bit = file_page_offset(&bitmap->storage, i);
                void *paddr;
                bool was_set;

                paddr = kmap_atomic(page);
                if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
                        was_set = test_bit(bit, paddr);
                else
                        was_set = test_bit_le(bit, paddr);
                kunmap_atomic(paddr);

                if (was_set) {
                        /* if the disk bit is set, set the memory bit */
                        int needed = ((sector_t)(i+1) << bitmap->counts.chunkshift
                                      >= start);
                        md_bitmap_set_memory_bits(bitmap,
                                                  (sector_t)i << bitmap->counts.chunkshift,
                                                  needed);
                        bit_cnt++;
                }
        }

        pr_debug("%s: bitmap initialized from disk: read %lu pages, set %lu of %lu bits\n",
                 bmname(bitmap), store->file_pages,
                 bit_cnt, chunks);

        return 0;

 err:
        pr_warn("%s: bitmap initialisation failed: %d\n",
                bmname(bitmap), ret);
        return ret;
}

/* just flag bitmap pages as needing to be written. */
static void bitmap_write_all(struct mddev *mddev)
{
        int i;
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap || !bitmap->storage.filemap)
                return;

        /* Only one copy, so nothing needed */
        if (bitmap->storage.file)
                return;

        for (i = 0; i < bitmap->storage.file_pages; i++)
                set_page_attr(bitmap, i, BITMAP_PAGE_NEEDWRITE);
        bitmap->allclean = 0;
}

static void md_bitmap_count_page(struct bitmap_counts *bitmap,
                                 sector_t offset, int inc)
{
        sector_t chunk = offset >> bitmap->chunkshift;
        unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
        bitmap->bp[page].count += inc;
        md_bitmap_checkfree(bitmap, page);
}

static void md_bitmap_set_pending(struct bitmap_counts *bitmap, sector_t offset)
{
        sector_t chunk = offset >> bitmap->chunkshift;
        unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
        struct bitmap_page *bp = &bitmap->bp[page];

        if (!bp->pending)
                bp->pending = 1;
}

static bitmap_counter_t *md_bitmap_get_counter(struct bitmap_counts *bitmap,
                                               sector_t offset, sector_t *blocks,
                                               int create);

static void mddev_set_timeout(struct mddev *mddev, unsigned long timeout,
                              bool force)
{
        struct md_thread *thread;

        rcu_read_lock();
        thread = rcu_dereference(mddev->thread);

        if (!thread)
                goto out;

        if (force || thread->timeout < MAX_SCHEDULE_TIMEOUT)
                thread->timeout = timeout;

out:
        rcu_read_unlock();
}

/*
 * bitmap daemon -- periodically wakes up to clean bits and flush pages
 *                      out to disk
 */
static void bitmap_daemon_work(struct mddev *mddev)
{
        struct bitmap *bitmap;
        unsigned long j;
        unsigned long nextpage;
        sector_t blocks;
        struct bitmap_counts *counts;

        /* Use a mutex to guard daemon_work against
         * bitmap_destroy.
         */
        mutex_lock(&mddev->bitmap_info.mutex);
        bitmap = mddev->bitmap;
        if (bitmap == NULL) {
                mutex_unlock(&mddev->bitmap_info.mutex);
                return;
        }
        if (time_before(jiffies, bitmap->daemon_lastrun
                        + mddev->bitmap_info.daemon_sleep))
                goto done;

        bitmap->daemon_lastrun = jiffies;
        if (bitmap->allclean) {
                mddev_set_timeout(mddev, MAX_SCHEDULE_TIMEOUT, true);
                goto done;
        }
        bitmap->allclean = 1;

        mddev_add_trace_msg(bitmap->mddev, "md bitmap_daemon_work");

        /* Any file-page which is PENDING now needs to be written.
         * So set NEEDWRITE now, then after we make any last-minute changes
         * we will write it.
         */
        for (j = 0; j < bitmap->storage.file_pages; j++)
                if (test_and_clear_page_attr(bitmap, j,
                                             BITMAP_PAGE_PENDING))
                        set_page_attr(bitmap, j,
                                      BITMAP_PAGE_NEEDWRITE);

        if (bitmap->need_sync &&
            mddev->bitmap_info.external == 0) {
                /* Arrange for superblock update as well as
                 * other changes */
                bitmap_super_t *sb;
                bitmap->need_sync = 0;
                if (bitmap->storage.filemap) {
                        sb = kmap_atomic(bitmap->storage.sb_page);
                        sb->events_cleared =
                                cpu_to_le64(bitmap->events_cleared);
                        kunmap_atomic(sb);
                        set_page_attr(bitmap, 0,
                                      BITMAP_PAGE_NEEDWRITE);
                }
        }
        /* Now look at the bitmap counters and if any are '2' or '1',
         * decrement and handle accordingly.
         */
        counts = &bitmap->counts;
        spin_lock_irq(&counts->lock);
        nextpage = 0;
        for (j = 0; j < counts->chunks; j++) {
                bitmap_counter_t *bmc;
                sector_t  block = (sector_t)j << counts->chunkshift;

                if (j == nextpage) {
                        nextpage += PAGE_COUNTER_RATIO;
                        if (!counts->bp[j >> PAGE_COUNTER_SHIFT].pending) {
                                j |= PAGE_COUNTER_MASK;
                                continue;
                        }
                        counts->bp[j >> PAGE_COUNTER_SHIFT].pending = 0;
                }

                bmc = md_bitmap_get_counter(counts, block, &blocks, 0);
                if (!bmc) {
                        j |= PAGE_COUNTER_MASK;
                        continue;
                }
                if (*bmc == 1 && !bitmap->need_sync) {
                        /* We can clear the bit */
                        *bmc = 0;
                        md_bitmap_count_page(counts, block, -1);
                        md_bitmap_file_clear_bit(bitmap, block);
                } else if (*bmc && *bmc <= 2) {
                        *bmc = 1;
                        md_bitmap_set_pending(counts, block);
                        bitmap->allclean = 0;
                }
        }
        spin_unlock_irq(&counts->lock);

        md_bitmap_wait_writes(bitmap);
        /* Now start writeout on any page in NEEDWRITE that isn't DIRTY.
         * DIRTY pages need to be written by bitmap_unplug so it can wait
         * for them.
         * If we find any DIRTY page we stop there and let bitmap_unplug
         * handle all the rest.  This is important in the case where
         * the first blocking holds the superblock and it has been updated.
         * We mustn't write any other blocks before the superblock.
         */
        for (j = 0;
             j < bitmap->storage.file_pages
                     && !test_bit(BITMAP_STALE, &bitmap->flags);
             j++) {
                if (test_page_attr(bitmap, j,
                                   BITMAP_PAGE_DIRTY))
                        /* bitmap_unplug will handle the rest */
                        break;
                if (bitmap->storage.filemap &&
                    test_and_clear_page_attr(bitmap, j,
                                             BITMAP_PAGE_NEEDWRITE))
                        filemap_write_page(bitmap, j, false);
        }

 done:
        if (bitmap->allclean == 0)
                mddev_set_timeout(mddev, mddev->bitmap_info.daemon_sleep, true);
        mutex_unlock(&mddev->bitmap_info.mutex);
}

static bitmap_counter_t *md_bitmap_get_counter(struct bitmap_counts *bitmap,
                                               sector_t offset, sector_t *blocks,
                                               int create)
__releases(bitmap->lock)
__acquires(bitmap->lock)
{
        /* If 'create', we might release the lock and reclaim it.
         * The lock must have been taken with interrupts enabled.
         * If !create, we don't release the lock.
         */
        sector_t chunk = offset >> bitmap->chunkshift;
        unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
        unsigned long pageoff = (chunk & PAGE_COUNTER_MASK) << COUNTER_BYTE_SHIFT;
        sector_t csize = ((sector_t)1) << bitmap->chunkshift;
        int err;

        if (page >= bitmap->pages) {
                /*
                 * This can happen if bitmap_start_sync goes beyond
                 * End-of-device while looking for a whole page or
                 * user set a huge number to sysfs bitmap_set_bits.
                 */
                *blocks = csize - (offset & (csize - 1));
                return NULL;
        }
        err = md_bitmap_checkpage(bitmap, page, create, 0);

        if (bitmap->bp[page].hijacked ||
            bitmap->bp[page].map == NULL)
                csize = ((sector_t)1) << (bitmap->chunkshift +
                                          PAGE_COUNTER_SHIFT);

        *blocks = csize - (offset & (csize - 1));

        if (err < 0)
                return NULL;

        /* now locked ... */

        if (bitmap->bp[page].hijacked) { /* hijacked pointer */
                /* should we use the first or second counter field
                 * of the hijacked pointer? */
                int hi = (pageoff > PAGE_COUNTER_MASK);
                return  &((bitmap_counter_t *)
                          &bitmap->bp[page].map)[hi];
        } else /* page is allocated */
                return (bitmap_counter_t *)
                        &(bitmap->bp[page].map[pageoff]);
}

static int bitmap_startwrite(struct mddev *mddev, sector_t offset,
                             unsigned long sectors, bool behind)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return 0;

        if (behind) {
                int bw;
                atomic_inc(&bitmap->behind_writes);
                bw = atomic_read(&bitmap->behind_writes);
                if (bw > bitmap->behind_writes_used)
                        bitmap->behind_writes_used = bw;

                pr_debug("inc write-behind count %d/%lu\n",
                         bw, bitmap->mddev->bitmap_info.max_write_behind);
        }

        while (sectors) {
                sector_t blocks;
                bitmap_counter_t *bmc;

                spin_lock_irq(&bitmap->counts.lock);
                bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 1);
                if (!bmc) {
                        spin_unlock_irq(&bitmap->counts.lock);
                        return 0;
                }

                if (unlikely(COUNTER(*bmc) == COUNTER_MAX)) {
                        DEFINE_WAIT(__wait);
                        /* note that it is safe to do the prepare_to_wait
                         * after the test as long as we do it before dropping
                         * the spinlock.
                         */
                        prepare_to_wait(&bitmap->overflow_wait, &__wait,
                                        TASK_UNINTERRUPTIBLE);
                        spin_unlock_irq(&bitmap->counts.lock);
                        schedule();
                        finish_wait(&bitmap->overflow_wait, &__wait);
                        continue;
                }

                switch (*bmc) {
                case 0:
                        md_bitmap_file_set_bit(bitmap, offset);
                        md_bitmap_count_page(&bitmap->counts, offset, 1);
                        fallthrough;
                case 1:
                        *bmc = 2;
                }

                (*bmc)++;

                spin_unlock_irq(&bitmap->counts.lock);

                offset += blocks;
                if (sectors > blocks)
                        sectors -= blocks;
                else
                        sectors = 0;
        }
        return 0;
}

static void bitmap_endwrite(struct mddev *mddev, sector_t offset,
                            unsigned long sectors, bool success, bool behind)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return;

        if (behind) {
                if (atomic_dec_and_test(&bitmap->behind_writes))
                        wake_up(&bitmap->behind_wait);
                pr_debug("dec write-behind count %d/%lu\n",
                         atomic_read(&bitmap->behind_writes),
                         bitmap->mddev->bitmap_info.max_write_behind);
        }

        while (sectors) {
                sector_t blocks;
                unsigned long flags;
                bitmap_counter_t *bmc;

                spin_lock_irqsave(&bitmap->counts.lock, flags);
                bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 0);
                if (!bmc) {
                        spin_unlock_irqrestore(&bitmap->counts.lock, flags);
                        return;
                }

                if (success && !bitmap->mddev->degraded &&
                    bitmap->events_cleared < bitmap->mddev->events) {
                        bitmap->events_cleared = bitmap->mddev->events;
                        bitmap->need_sync = 1;
                        sysfs_notify_dirent_safe(bitmap->sysfs_can_clear);
                }

                if (!success && !NEEDED(*bmc))
                        *bmc |= NEEDED_MASK;

                if (COUNTER(*bmc) == COUNTER_MAX)
                        wake_up(&bitmap->overflow_wait);

                (*bmc)--;
                if (*bmc <= 2) {
                        md_bitmap_set_pending(&bitmap->counts, offset);
                        bitmap->allclean = 0;
                }
                spin_unlock_irqrestore(&bitmap->counts.lock, flags);
                offset += blocks;
                if (sectors > blocks)
                        sectors -= blocks;
                else
                        sectors = 0;
        }
}

static bool __bitmap_start_sync(struct bitmap *bitmap, sector_t offset,
                                sector_t *blocks, bool degraded)
{
        bitmap_counter_t *bmc;
        bool rv;

        if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
                *blocks = 1024;
                return true; /* always resync if no bitmap */
        }
        spin_lock_irq(&bitmap->counts.lock);

        rv = false;
        bmc = md_bitmap_get_counter(&bitmap->counts, offset, blocks, 0);
        if (bmc) {
                /* locked */
                if (RESYNC(*bmc)) {
                        rv = true;
                } else if (NEEDED(*bmc)) {
                        rv = true;
                        if (!degraded) { /* don't set/clear bits if degraded */
                                *bmc |= RESYNC_MASK;
                                *bmc &= ~NEEDED_MASK;
                        }
                }
        }
        spin_unlock_irq(&bitmap->counts.lock);

        return rv;
}

static bool bitmap_start_sync(struct mddev *mddev, sector_t offset,
                              sector_t *blocks, bool degraded)
{
        /* bitmap_start_sync must always report on multiples of whole
         * pages, otherwise resync (which is very PAGE_SIZE based) will
         * get confused.
         * So call __bitmap_start_sync repeatedly (if needed) until
         * At least PAGE_SIZE>>9 blocks are covered.
         * Return the 'or' of the result.
         */
        bool rv = false;
        sector_t blocks1;

        *blocks = 0;
        while (*blocks < (PAGE_SIZE>>9)) {
                rv |= __bitmap_start_sync(mddev->bitmap, offset,
                                          &blocks1, degraded);
                offset += blocks1;
                *blocks += blocks1;
        }

        return rv;
}

static void __bitmap_end_sync(struct bitmap *bitmap, sector_t offset,
                              sector_t *blocks, bool aborted)
{
        bitmap_counter_t *bmc;
        unsigned long flags;

        if (bitmap == NULL) {
                *blocks = 1024;
                return;
        }
        spin_lock_irqsave(&bitmap->counts.lock, flags);
        bmc = md_bitmap_get_counter(&bitmap->counts, offset, blocks, 0);
        if (bmc == NULL)
                goto unlock;
        /* locked */
        if (RESYNC(*bmc)) {
                *bmc &= ~RESYNC_MASK;

                if (!NEEDED(*bmc) && aborted)
                        *bmc |= NEEDED_MASK;
                else {
                        if (*bmc <= 2) {
                                md_bitmap_set_pending(&bitmap->counts, offset);
                                bitmap->allclean = 0;
                        }
                }
        }
 unlock:
        spin_unlock_irqrestore(&bitmap->counts.lock, flags);
}

static void bitmap_end_sync(struct mddev *mddev, sector_t offset,
                            sector_t *blocks)
{
        __bitmap_end_sync(mddev->bitmap, offset, blocks, true);
}

static void bitmap_close_sync(struct mddev *mddev)
{
        /* Sync has finished, and any bitmap chunks that weren't synced
         * properly have been aborted.  It remains to us to clear the
         * RESYNC bit wherever it is still on
         */
        sector_t sector = 0;
        sector_t blocks;
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return;

        while (sector < bitmap->mddev->resync_max_sectors) {
                __bitmap_end_sync(bitmap, sector, &blocks, false);
                sector += blocks;
        }
}

static void bitmap_cond_end_sync(struct mddev *mddev, sector_t sector,
                                 bool force)
{
        sector_t s = 0;
        sector_t blocks;
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return;
        if (sector == 0) {
                bitmap->last_end_sync = jiffies;
                return;
        }
        if (!force && time_before(jiffies, (bitmap->last_end_sync
                                  + bitmap->mddev->bitmap_info.daemon_sleep)))
                return;
        wait_event(bitmap->mddev->recovery_wait,
                   atomic_read(&bitmap->mddev->recovery_active) == 0);

        bitmap->mddev->curr_resync_completed = sector;
        set_bit(MD_SB_CHANGE_CLEAN, &bitmap->mddev->sb_flags);
        sector &= ~((1ULL << bitmap->counts.chunkshift) - 1);
        s = 0;
        while (s < sector && s < bitmap->mddev->resync_max_sectors) {
                __bitmap_end_sync(bitmap, s, &blocks, false);
                s += blocks;
        }
        bitmap->last_end_sync = jiffies;
        sysfs_notify_dirent_safe(bitmap->mddev->sysfs_completed);
}

static void bitmap_sync_with_cluster(struct mddev *mddev,
                                     sector_t old_lo, sector_t old_hi,
                                     sector_t new_lo, sector_t new_hi)
{
        struct bitmap *bitmap = mddev->bitmap;
        sector_t sector, blocks = 0;

        for (sector = old_lo; sector < new_lo; ) {
                __bitmap_end_sync(bitmap, sector, &blocks, false);
                sector += blocks;
        }
        WARN((blocks > new_lo) && old_lo, "alignment is not correct for lo\n");

        for (sector = old_hi; sector < new_hi; ) {
                bitmap_start_sync(mddev, sector, &blocks, false);
                sector += blocks;
        }
        WARN((blocks > new_hi) && old_hi, "alignment is not correct for hi\n");
}

static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed)
{
        /* For each chunk covered by any of these sectors, set the
         * counter to 2 and possibly set resync_needed.  They should all
         * be 0 at this point
         */

        sector_t secs;
        bitmap_counter_t *bmc;
        spin_lock_irq(&bitmap->counts.lock);
        bmc = md_bitmap_get_counter(&bitmap->counts, offset, &secs, 1);
        if (!bmc) {
                spin_unlock_irq(&bitmap->counts.lock);
                return;
        }
        if (!*bmc) {
                *bmc = 2;
                md_bitmap_count_page(&bitmap->counts, offset, 1);
                md_bitmap_set_pending(&bitmap->counts, offset);
                bitmap->allclean = 0;
        }
        if (needed)
                *bmc |= NEEDED_MASK;
        spin_unlock_irq(&bitmap->counts.lock);
}

/* dirty the memory and file bits for bitmap chunks "s" to "e" */
static void bitmap_dirty_bits(struct mddev *mddev, unsigned long s,
                              unsigned long e)
{
        unsigned long chunk;
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return;

        for (chunk = s; chunk <= e; chunk++) {
                sector_t sec = (sector_t)chunk << bitmap->counts.chunkshift;

                md_bitmap_set_memory_bits(bitmap, sec, 1);
                md_bitmap_file_set_bit(bitmap, sec);
                if (sec < bitmap->mddev->recovery_cp)
                        /* We are asserting that the array is dirty,
                         * so move the recovery_cp address back so
                         * that it is obvious that it is dirty
                         */
                        bitmap->mddev->recovery_cp = sec;
        }
}

static void bitmap_flush(struct mddev *mddev)
{
        struct bitmap *bitmap = mddev->bitmap;
        long sleep;

        if (!bitmap) /* there was no bitmap */
                return;

        /* run the daemon_work three time to ensure everything is flushed
         * that can be
         */
        sleep = mddev->bitmap_info.daemon_sleep * 2;
        bitmap->daemon_lastrun -= sleep;
        bitmap_daemon_work(mddev);
        bitmap->daemon_lastrun -= sleep;
        bitmap_daemon_work(mddev);
        bitmap->daemon_lastrun -= sleep;
        bitmap_daemon_work(mddev);
        if (mddev->bitmap_info.external)
                md_super_wait(mddev);
        bitmap_update_sb(bitmap);
}

static void md_bitmap_free(void *data)
{
        unsigned long k, pages;
        struct bitmap_page *bp;
        struct bitmap *bitmap = data;

        if (!bitmap) /* there was no bitmap */
                return;

        if (bitmap->sysfs_can_clear)
                sysfs_put(bitmap->sysfs_can_clear);

        if (mddev_is_clustered(bitmap->mddev) && bitmap->mddev->cluster_info &&
                bitmap->cluster_slot == md_cluster_ops->slot_number(bitmap->mddev))
                md_cluster_stop(bitmap->mddev);

        /* Shouldn't be needed - but just in case.... */
        wait_event(bitmap->write_wait,
                   atomic_read(&bitmap->pending_writes) == 0);

        /* release the bitmap file  */
        md_bitmap_file_unmap(&bitmap->storage);

        bp = bitmap->counts.bp;
        pages = bitmap->counts.pages;

        /* free all allocated memory */

        if (bp) /* deallocate the page memory */
                for (k = 0; k < pages; k++)
                        if (bp[k].map && !bp[k].hijacked)
                                kfree(bp[k].map);
        kfree(bp);
        kfree(bitmap);
}

static void bitmap_wait_behind_writes(struct mddev *mddev)
{
        struct bitmap *bitmap = mddev->bitmap;

        /* wait for behind writes to complete */
        if (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
                pr_debug("md:%s: behind writes in progress - waiting to stop.\n",
                         mdname(mddev));
                /* need to kick something here to make sure I/O goes? */
                wait_event(bitmap->behind_wait,
                           atomic_read(&bitmap->behind_writes) == 0);
        }
}

static void bitmap_destroy(struct mddev *mddev)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap) /* there was no bitmap */
                return;

        bitmap_wait_behind_writes(mddev);
        if (!mddev->serialize_policy)
                mddev_destroy_serial_pool(mddev, NULL);

        mutex_lock(&mddev->bitmap_info.mutex);
        spin_lock(&mddev->lock);
        mddev->bitmap = NULL; /* disconnect from the md device */
        spin_unlock(&mddev->lock);
        mutex_unlock(&mddev->bitmap_info.mutex);
        mddev_set_timeout(mddev, MAX_SCHEDULE_TIMEOUT, true);

        md_bitmap_free(bitmap);
}

/*
 * initialize the bitmap structure
 * if this returns an error, bitmap_destroy must be called to do clean up
 * once mddev->bitmap is set
 */
static struct bitmap *__bitmap_create(struct mddev *mddev, int slot)
{
        struct bitmap *bitmap;
        sector_t blocks = mddev->resync_max_sectors;
        struct file *file = mddev->bitmap_info.file;
        int err;
        struct kernfs_node *bm = NULL;

        BUILD_BUG_ON(sizeof(bitmap_super_t) != 256);

        BUG_ON(file && mddev->bitmap_info.offset);

        if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
                pr_notice("md/raid:%s: array with journal cannot have bitmap\n",
                          mdname(mddev));
                return ERR_PTR(-EBUSY);
        }

        bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL);
        if (!bitmap)
                return ERR_PTR(-ENOMEM);

        spin_lock_init(&bitmap->counts.lock);
        atomic_set(&bitmap->pending_writes, 0);
        init_waitqueue_head(&bitmap->write_wait);
        init_waitqueue_head(&bitmap->overflow_wait);
        init_waitqueue_head(&bitmap->behind_wait);

        bitmap->mddev = mddev;
        bitmap->cluster_slot = slot;

        if (mddev->kobj.sd)
                bm = sysfs_get_dirent(mddev->kobj.sd, "bitmap");
        if (bm) {
                bitmap->sysfs_can_clear = sysfs_get_dirent(bm, "can_clear");
                sysfs_put(bm);
        } else
                bitmap->sysfs_can_clear = NULL;

        bitmap->storage.file = file;
        if (file) {
                get_file(file);
                /* As future accesses to this file will use bmap,
                 * and bypass the page cache, we must sync the file
                 * first.
                 */
                vfs_fsync(file, 1);
        }
        /* read superblock from bitmap file (this sets mddev->bitmap_info.chunksize) */
        if (!mddev->bitmap_info.external) {
                /*
                 * If 'MD_ARRAY_FIRST_USE' is set, then device-mapper is
                 * instructing us to create a new on-disk bitmap instance.
                 */
                if (test_and_clear_bit(MD_ARRAY_FIRST_USE, &mddev->flags))
                        err = md_bitmap_new_disk_sb(bitmap);
                else
                        err = md_bitmap_read_sb(bitmap);
        } else {
                err = 0;
                if (mddev->bitmap_info.chunksize == 0 ||
                    mddev->bitmap_info.daemon_sleep == 0)
                        /* chunksize and time_base need to be
                         * set first. */
                        err = -EINVAL;
        }
        if (err)
                goto error;

        bitmap->daemon_lastrun = jiffies;
        err = __bitmap_resize(bitmap, blocks, mddev->bitmap_info.chunksize,
                              true);
        if (err)
                goto error;

        pr_debug("created bitmap (%lu pages) for device %s\n",
                 bitmap->counts.pages, bmname(bitmap));

        err = test_bit(BITMAP_WRITE_ERROR, &bitmap->flags) ? -EIO : 0;
        if (err)
                goto error;

        return bitmap;
 error:
        md_bitmap_free(bitmap);
        return ERR_PTR(err);
}

static int bitmap_create(struct mddev *mddev, int slot)
{
        struct bitmap *bitmap = __bitmap_create(mddev, slot);

        if (IS_ERR(bitmap))
                return PTR_ERR(bitmap);

        mddev->bitmap = bitmap;
        return 0;
}

static int bitmap_load(struct mddev *mddev)
{
        int err = 0;
        sector_t start = 0;
        sector_t sector = 0;
        struct bitmap *bitmap = mddev->bitmap;
        struct md_rdev *rdev;

        if (!bitmap)
                goto out;

        rdev_for_each(rdev, mddev)
                mddev_create_serial_pool(mddev, rdev);

        if (mddev_is_clustered(mddev))
                md_cluster_ops->load_bitmaps(mddev, mddev->bitmap_info.nodes);

        /* Clear out old bitmap info first:  Either there is none, or we
         * are resuming after someone else has possibly changed things,
         * so we should forget old cached info.
         * All chunks should be clean, but some might need_sync.
         */
        while (sector < mddev->resync_max_sectors) {
                sector_t blocks;
                bitmap_start_sync(mddev, sector, &blocks, false);
                sector += blocks;
        }
        bitmap_close_sync(mddev);

        if (mddev->degraded == 0
            || bitmap->events_cleared == mddev->events)
                /* no need to keep dirty bits to optimise a
                 * re-add of a missing device */
                start = mddev->recovery_cp;

        mutex_lock(&mddev->bitmap_info.mutex);
        err = md_bitmap_init_from_disk(bitmap, start);
        mutex_unlock(&mddev->bitmap_info.mutex);

        if (err)
                goto out;
        clear_bit(BITMAP_STALE, &bitmap->flags);

        /* Kick recovery in case any bits were set */
        set_bit(MD_RECOVERY_NEEDED, &bitmap->mddev->recovery);

        mddev_set_timeout(mddev, mddev->bitmap_info.daemon_sleep, true);
        md_wakeup_thread(mddev->thread);

        bitmap_update_sb(bitmap);

        if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
                err = -EIO;
out:
        return err;
}

/* caller need to free returned bitmap with md_bitmap_free() */
static void *bitmap_get_from_slot(struct mddev *mddev, int slot)
{
        int rv = 0;
        struct bitmap *bitmap;

        bitmap = __bitmap_create(mddev, slot);
        if (IS_ERR(bitmap)) {
                rv = PTR_ERR(bitmap);
                return ERR_PTR(rv);
        }

        rv = md_bitmap_init_from_disk(bitmap, 0);
        if (rv) {
                md_bitmap_free(bitmap);
                return ERR_PTR(rv);
        }

        return bitmap;
}

/* Loads the bitmap associated with slot and copies the resync information
 * to our bitmap
 */
static int bitmap_copy_from_slot(struct mddev *mddev, int slot, sector_t *low,
                                 sector_t *high, bool clear_bits)
{
        int rv = 0, i, j;
        sector_t block, lo = 0, hi = 0;
        struct bitmap_counts *counts;
        struct bitmap *bitmap;

        bitmap = bitmap_get_from_slot(mddev, slot);
        if (IS_ERR(bitmap)) {
                pr_err("%s can't get bitmap from slot %d\n", __func__, slot);
                return -1;
        }

        counts = &bitmap->counts;
        for (j = 0; j < counts->chunks; j++) {
                block = (sector_t)j << counts->chunkshift;
                if (md_bitmap_file_test_bit(bitmap, block)) {
                        if (!lo)
                                lo = block;
                        hi = block;
                        md_bitmap_file_clear_bit(bitmap, block);
                        md_bitmap_set_memory_bits(mddev->bitmap, block, 1);
                        md_bitmap_file_set_bit(mddev->bitmap, block);
                }
        }

        if (clear_bits) {
                bitmap_update_sb(bitmap);
                /* BITMAP_PAGE_PENDING is set, but bitmap_unplug needs
                 * BITMAP_PAGE_DIRTY or _NEEDWRITE to write ... */
                for (i = 0; i < bitmap->storage.file_pages; i++)
                        if (test_page_attr(bitmap, i, BITMAP_PAGE_PENDING))
                                set_page_attr(bitmap, i, BITMAP_PAGE_NEEDWRITE);
                __bitmap_unplug(bitmap);
        }
        __bitmap_unplug(mddev->bitmap);
        *low = lo;
        *high = hi;
        md_bitmap_free(bitmap);

        return rv;
}

static void bitmap_set_pages(void *data, unsigned long pages)
{
        struct bitmap *bitmap = data;

        bitmap->counts.pages = pages;
}

static int bitmap_get_stats(void *data, struct md_bitmap_stats *stats)
{
        struct bitmap_storage *storage;
        struct bitmap_counts *counts;
        struct bitmap *bitmap = data;
        bitmap_super_t *sb;

        if (!bitmap)
                return -ENOENT;

        sb = kmap_local_page(bitmap->storage.sb_page);
        stats->sync_size = le64_to_cpu(sb->sync_size);
        kunmap_local(sb);

        counts = &bitmap->counts;
        stats->missing_pages = counts->missing_pages;
        stats->pages = counts->pages;

        storage = &bitmap->storage;
        stats->file_pages = storage->file_pages;
        stats->file = storage->file;

        stats->behind_writes = atomic_read(&bitmap->behind_writes);
        stats->behind_wait = wq_has_sleeper(&bitmap->behind_wait);
        stats->events_cleared = bitmap->events_cleared;
        return 0;
}

static int __bitmap_resize(struct bitmap *bitmap, sector_t blocks,
                           int chunksize, bool init)
{
        /* If chunk_size is 0, choose an appropriate chunk size.
         * Then possibly allocate new storage space.
         * Then quiesce, copy bits, replace bitmap, and re-start
         *
         * This function is called both to set up the initial bitmap
         * and to resize the bitmap while the array is active.
         * If this happens as a result of the array being resized,
         * chunksize will be zero, and we need to choose a suitable
         * chunksize, otherwise we use what we are given.
         */
        struct bitmap_storage store;
        struct bitmap_counts old_counts;
        unsigned long chunks;
        sector_t block;
        sector_t old_blocks, new_blocks;
        int chunkshift;
        int ret = 0;
        long pages;
        struct bitmap_page *new_bp;

        if (bitmap->storage.file && !init) {
                pr_info("md: cannot resize file-based bitmap\n");
                return -EINVAL;
        }

        if (chunksize == 0) {
                /* If there is enough space, leave the chunk size unchanged,
                 * else increase by factor of two until there is enough space.
                 */
                long bytes;
                long space = bitmap->mddev->bitmap_info.space;

                if (space == 0) {
                        /* We don't know how much space there is, so limit
                         * to current size - in sectors.
                         */
                        bytes = DIV_ROUND_UP(bitmap->counts.chunks, 8);
                        if (!bitmap->mddev->bitmap_info.external)
                                bytes += sizeof(bitmap_super_t);
                        space = DIV_ROUND_UP(bytes, 512);
                        bitmap->mddev->bitmap_info.space = space;
                }
                chunkshift = bitmap->counts.chunkshift;
                chunkshift--;
                do {
                        /* 'chunkshift' is shift from block size to chunk size */
                        chunkshift++;
                        chunks = DIV_ROUND_UP_SECTOR_T(blocks, 1 << chunkshift);
                        bytes = DIV_ROUND_UP(chunks, 8);
                        if (!bitmap->mddev->bitmap_info.external)
                                bytes += sizeof(bitmap_super_t);
                } while (bytes > (space << 9) && (chunkshift + BITMAP_BLOCK_SHIFT) <
                        (BITS_PER_BYTE * sizeof(((bitmap_super_t *)0)->chunksize) - 1));
        } else
                chunkshift = ffz(~chunksize) - BITMAP_BLOCK_SHIFT;

        chunks = DIV_ROUND_UP_SECTOR_T(blocks, 1 << chunkshift);
        memset(&store, 0, sizeof(store));
        if (bitmap->mddev->bitmap_info.offset || bitmap->mddev->bitmap_info.file)
                ret = md_bitmap_storage_alloc(&store, chunks,
                                              !bitmap->mddev->bitmap_info.external,
                                              mddev_is_clustered(bitmap->mddev)
                                              ? bitmap->cluster_slot : 0);
        if (ret) {
                md_bitmap_file_unmap(&store);
                goto err;
        }

        pages = DIV_ROUND_UP(chunks, PAGE_COUNTER_RATIO);

        new_bp = kcalloc(pages, sizeof(*new_bp), GFP_KERNEL);
        ret = -ENOMEM;
        if (!new_bp) {
                md_bitmap_file_unmap(&store);
                goto err;
        }

        if (!init)
                bitmap->mddev->pers->quiesce(bitmap->mddev, 1);

        store.file = bitmap->storage.file;
        bitmap->storage.file = NULL;

        if (store.sb_page && bitmap->storage.sb_page)
                memcpy(page_address(store.sb_page),
                       page_address(bitmap->storage.sb_page),
                       sizeof(bitmap_super_t));
        spin_lock_irq(&bitmap->counts.lock);
        md_bitmap_file_unmap(&bitmap->storage);
        bitmap->storage = store;

        old_counts = bitmap->counts;
        bitmap->counts.bp = new_bp;
        bitmap->counts.pages = pages;
        bitmap->counts.missing_pages = pages;
        bitmap->counts.chunkshift = chunkshift;
        bitmap->counts.chunks = chunks;
        bitmap->mddev->bitmap_info.chunksize = 1UL << (chunkshift +
                                                     BITMAP_BLOCK_SHIFT);

        blocks = min(old_counts.chunks << old_counts.chunkshift,
                     chunks << chunkshift);

        /* For cluster raid, need to pre-allocate bitmap */
        if (mddev_is_clustered(bitmap->mddev)) {
                unsigned long page;
                for (page = 0; page < pages; page++) {
                        ret = md_bitmap_checkpage(&bitmap->counts, page, 1, 1);
                        if (ret) {
                                unsigned long k;

                                /* deallocate the page memory */
                                for (k = 0; k < page; k++) {
                                        kfree(new_bp[k].map);
                                }
                                kfree(new_bp);

                                /* restore some fields from old_counts */
                                bitmap->counts.bp = old_counts.bp;
                                bitmap->counts.pages = old_counts.pages;
                                bitmap->counts.missing_pages = old_counts.pages;
                                bitmap->counts.chunkshift = old_counts.chunkshift;
                                bitmap->counts.chunks = old_counts.chunks;
                                bitmap->mddev->bitmap_info.chunksize =
                                        1UL << (old_counts.chunkshift + BITMAP_BLOCK_SHIFT);
                                blocks = old_counts.chunks << old_counts.chunkshift;
                                pr_warn("Could not pre-allocate in-memory bitmap for cluster raid\n");
                                break;
                        } else
                                bitmap->counts.bp[page].count += 1;
                }
        }

        for (block = 0; block < blocks; ) {
                bitmap_counter_t *bmc_old, *bmc_new;
                int set;

                bmc_old = md_bitmap_get_counter(&old_counts, block, &old_blocks, 0);
                set = bmc_old && NEEDED(*bmc_old);

                if (set) {
                        bmc_new = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1);
                        if (bmc_new) {
                                if (*bmc_new == 0) {
                                        /* need to set on-disk bits too. */
                                        sector_t end = block + new_blocks;
                                        sector_t start = block >> chunkshift;

                                        start <<= chunkshift;
                                        while (start < end) {
                                                md_bitmap_file_set_bit(bitmap, block);
                                                start += 1 << chunkshift;
                                        }
                                        *bmc_new = 2;
                                        md_bitmap_count_page(&bitmap->counts, block, 1);
                                        md_bitmap_set_pending(&bitmap->counts, block);
                                }
                                *bmc_new |= NEEDED_MASK;
                        }
                        if (new_blocks < old_blocks)
                                old_blocks = new_blocks;
                }
                block += old_blocks;
        }

        if (bitmap->counts.bp != old_counts.bp) {
                unsigned long k;
                for (k = 0; k < old_counts.pages; k++)
                        if (!old_counts.bp[k].hijacked)
                                kfree(old_counts.bp[k].map);
                kfree(old_counts.bp);
        }

        if (!init) {
                int i;
                while (block < (chunks << chunkshift)) {
                        bitmap_counter_t *bmc;
                        bmc = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1);
                        if (bmc) {
                                /* new space.  It needs to be resynced, so
                                 * we set NEEDED_MASK.
                                 */
                                if (*bmc == 0) {
                                        *bmc = NEEDED_MASK | 2;
                                        md_bitmap_count_page(&bitmap->counts, block, 1);
                                        md_bitmap_set_pending(&bitmap->counts, block);
                                }
                        }
                        block += new_blocks;
                }
                for (i = 0; i < bitmap->storage.file_pages; i++)
                        set_page_attr(bitmap, i, BITMAP_PAGE_DIRTY);
        }
        spin_unlock_irq(&bitmap->counts.lock);

        if (!init) {
                __bitmap_unplug(bitmap);
                bitmap->mddev->pers->quiesce(bitmap->mddev, 0);
        }
        ret = 0;
err:
        return ret;
}

static int bitmap_resize(struct mddev *mddev, sector_t blocks, int chunksize,
                         bool init)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return 0;

        return __bitmap_resize(bitmap, blocks, chunksize, init);
}

static ssize_t
location_show(struct mddev *mddev, char *page)
{
        ssize_t len;
        if (mddev->bitmap_info.file)
                len = sprintf(page, "file");
        else if (mddev->bitmap_info.offset)
                len = sprintf(page, "%+lld", (long long)mddev->bitmap_info.offset);
        else
                len = sprintf(page, "none");
        len += sprintf(page+len, "\n");
        return len;
}

static ssize_t
location_store(struct mddev *mddev, const char *buf, size_t len)
{
        int rv;

        rv = mddev_suspend_and_lock(mddev);
        if (rv)
                return rv;

        if (mddev->pers) {
                if (mddev->recovery || mddev->sync_thread) {
                        rv = -EBUSY;
                        goto out;
                }
        }

        if (mddev->bitmap || mddev->bitmap_info.file ||
            mddev->bitmap_info.offset) {
                /* bitmap already configured.  Only option is to clear it */
                if (strncmp(buf, "none", 4) != 0) {
                        rv = -EBUSY;
                        goto out;
                }

                bitmap_destroy(mddev);
                mddev->bitmap_info.offset = 0;
                if (mddev->bitmap_info.file) {
                        struct file *f = mddev->bitmap_info.file;
                        mddev->bitmap_info.file = NULL;
                        fput(f);
                }
        } else {
                /* No bitmap, OK to set a location */
                long long offset;

                if (strncmp(buf, "none", 4) == 0)
                        /* nothing to be done */;
                else if (strncmp(buf, "file:", 5) == 0) {
                        /* Not supported yet */
                        rv = -EINVAL;
                        goto out;
                } else {
                        if (buf[0] == '+')
                                rv = kstrtoll(buf+1, 10, &offset);
                        else
                                rv = kstrtoll(buf, 10, &offset);
                        if (rv)
                                goto out;
                        if (offset == 0) {
                                rv = -EINVAL;
                                goto out;
                        }
                        if (mddev->bitmap_info.external == 0 &&
                            mddev->major_version == 0 &&
                            offset != mddev->bitmap_info.default_offset) {
                                rv = -EINVAL;
                                goto out;
                        }

                        mddev->bitmap_info.offset = offset;
                        rv = bitmap_create(mddev, -1);
                        if (rv)
                                goto out;

                        rv = bitmap_load(mddev);
                        if (rv) {
                                mddev->bitmap_info.offset = 0;
                                bitmap_destroy(mddev);
                                goto out;
                        }
                }
        }
        if (!mddev->external) {
                /* Ensure new bitmap info is stored in
                 * metadata promptly.
                 */
                set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
                md_wakeup_thread(mddev->thread);
        }
        rv = 0;
out:
        mddev_unlock_and_resume(mddev);
        if (rv)
                return rv;
        return len;
}

static struct md_sysfs_entry bitmap_location =
__ATTR(location, S_IRUGO|S_IWUSR, location_show, location_store);

/* 'bitmap/space' is the space available at 'location' for the
 * bitmap.  This allows the kernel to know when it is safe to
 * resize the bitmap to match a resized array.
 */
static ssize_t
space_show(struct mddev *mddev, char *page)
{
        return sprintf(page, "%lu\n", mddev->bitmap_info.space);
}

static ssize_t
space_store(struct mddev *mddev, const char *buf, size_t len)
{
        struct bitmap *bitmap;
        unsigned long sectors;
        int rv;

        rv = kstrtoul(buf, 10, &sectors);
        if (rv)
                return rv;

        if (sectors == 0)
                return -EINVAL;

        bitmap = mddev->bitmap;
        if (bitmap && sectors < (bitmap->storage.bytes + 511) >> 9)
                return -EFBIG; /* Bitmap is too big for this small space */

        /* could make sure it isn't too big, but that isn't really
         * needed - user-space should be careful.
         */
        mddev->bitmap_info.space = sectors;
        return len;
}

static struct md_sysfs_entry bitmap_space =
__ATTR(space, S_IRUGO|S_IWUSR, space_show, space_store);

static ssize_t
timeout_show(struct mddev *mddev, char *page)
{
        ssize_t len;
        unsigned long secs = mddev->bitmap_info.daemon_sleep / HZ;
        unsigned long jifs = mddev->bitmap_info.daemon_sleep % HZ;

        len = sprintf(page, "%lu", secs);
        if (jifs)
                len += sprintf(page+len, ".%03u", jiffies_to_msecs(jifs));
        len += sprintf(page+len, "\n");
        return len;
}

static ssize_t
timeout_store(struct mddev *mddev, const char *buf, size_t len)
{
        /* timeout can be set at any time */
        unsigned long timeout;
        int rv = strict_strtoul_scaled(buf, &timeout, 4);
        if (rv)
                return rv;

        /* just to make sure we don't overflow... */
        if (timeout >= LONG_MAX / HZ)
                return -EINVAL;

        timeout = timeout * HZ / 10000;

        if (timeout >= MAX_SCHEDULE_TIMEOUT)
                timeout = MAX_SCHEDULE_TIMEOUT-1;
        if (timeout < 1)
                timeout = 1;

        mddev->bitmap_info.daemon_sleep = timeout;
        mddev_set_timeout(mddev, timeout, false);
        md_wakeup_thread(mddev->thread);

        return len;
}

static struct md_sysfs_entry bitmap_timeout =
__ATTR(time_base, S_IRUGO|S_IWUSR, timeout_show, timeout_store);

static ssize_t
backlog_show(struct mddev *mddev, char *page)
{
        return sprintf(page, "%lu\n", mddev->bitmap_info.max_write_behind);
}

static ssize_t
backlog_store(struct mddev *mddev, const char *buf, size_t len)
{
        unsigned long backlog;
        unsigned long old_mwb = mddev->bitmap_info.max_write_behind;
        struct md_rdev *rdev;
        bool has_write_mostly = false;
        int rv = kstrtoul(buf, 10, &backlog);
        if (rv)
                return rv;
        if (backlog > COUNTER_MAX)
                return -EINVAL;

        rv = mddev_suspend_and_lock(mddev);
        if (rv)
                return rv;

        /*
         * Without write mostly device, it doesn't make sense to set
         * backlog for max_write_behind.
         */
        rdev_for_each(rdev, mddev) {
                if (test_bit(WriteMostly, &rdev->flags)) {
                        has_write_mostly = true;
                        break;
                }
        }
        if (!has_write_mostly) {
                pr_warn_ratelimited("%s: can't set backlog, no write mostly device available\n",
                                    mdname(mddev));
                mddev_unlock(mddev);
                return -EINVAL;
        }

        mddev->bitmap_info.max_write_behind = backlog;
        if (!backlog && mddev->serial_info_pool) {
                /* serial_info_pool is not needed if backlog is zero */
                if (!mddev->serialize_policy)
                        mddev_destroy_serial_pool(mddev, NULL);
        } else if (backlog && !mddev->serial_info_pool) {
                /* serial_info_pool is needed since backlog is not zero */
                rdev_for_each(rdev, mddev)
                        mddev_create_serial_pool(mddev, rdev);
        }
        if (old_mwb != backlog)
                bitmap_update_sb(mddev->bitmap);

        mddev_unlock_and_resume(mddev);
        return len;
}

static struct md_sysfs_entry bitmap_backlog =
__ATTR(backlog, S_IRUGO|S_IWUSR, backlog_show, backlog_store);

static ssize_t
chunksize_show(struct mddev *mddev, char *page)
{
        return sprintf(page, "%lu\n", mddev->bitmap_info.chunksize);
}

static ssize_t
chunksize_store(struct mddev *mddev, const char *buf, size_t len)
{
        /* Can only be changed when no bitmap is active */
        int rv;
        unsigned long csize;
        if (mddev->bitmap)
                return -EBUSY;
        rv = kstrtoul(buf, 10, &csize);
        if (rv)
                return rv;
        if (csize < 512 ||
            !is_power_of_2(csize))
                return -EINVAL;
        if (BITS_PER_LONG > 32 && csize >= (1ULL << (BITS_PER_BYTE *
                sizeof(((bitmap_super_t *)0)->chunksize))))
                return -EOVERFLOW;
        mddev->bitmap_info.chunksize = csize;
        return len;
}

static struct md_sysfs_entry bitmap_chunksize =
__ATTR(chunksize, S_IRUGO|S_IWUSR, chunksize_show, chunksize_store);

static ssize_t metadata_show(struct mddev *mddev, char *page)
{
        if (mddev_is_clustered(mddev))
                return sprintf(page, "clustered\n");
        return sprintf(page, "%s\n", (mddev->bitmap_info.external
                                      ? "external" : "internal"));
}

static ssize_t metadata_store(struct mddev *mddev, const char *buf, size_t len)
{
        if (mddev->bitmap ||
            mddev->bitmap_info.file ||
            mddev->bitmap_info.offset)
                return -EBUSY;
        if (strncmp(buf, "external", 8) == 0)
                mddev->bitmap_info.external = 1;
        else if ((strncmp(buf, "internal", 8) == 0) ||
                        (strncmp(buf, "clustered", 9) == 0))
                mddev->bitmap_info.external = 0;
        else
                return -EINVAL;
        return len;
}

static struct md_sysfs_entry bitmap_metadata =
__ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store);

static ssize_t can_clear_show(struct mddev *mddev, char *page)
{
        int len;
        struct bitmap *bitmap;

        spin_lock(&mddev->lock);
        bitmap = mddev->bitmap;
        if (bitmap)
                len = sprintf(page, "%s\n", (bitmap->need_sync ? "false" :
                                                                 "true"));
        else
                len = sprintf(page, "\n");
        spin_unlock(&mddev->lock);
        return len;
}

static ssize_t can_clear_store(struct mddev *mddev, const char *buf, size_t len)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                return -ENOENT;

        if (strncmp(buf, "false", 5) == 0) {
                bitmap->need_sync = 1;
                return len;
        }

        if (strncmp(buf, "true", 4) == 0) {
                if (mddev->degraded)
                        return -EBUSY;
                bitmap->need_sync = 0;
                return len;
        }

        return -EINVAL;
}

static struct md_sysfs_entry bitmap_can_clear =
__ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store);

static ssize_t
behind_writes_used_show(struct mddev *mddev, char *page)
{
        ssize_t ret;
        struct bitmap *bitmap;

        spin_lock(&mddev->lock);
        bitmap = mddev->bitmap;
        if (!bitmap)
                ret = sprintf(page, "0\n");
        else
                ret = sprintf(page, "%lu\n", bitmap->behind_writes_used);
        spin_unlock(&mddev->lock);

        return ret;
}

static ssize_t
behind_writes_used_reset(struct mddev *mddev, const char *buf, size_t len)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (bitmap)
                bitmap->behind_writes_used = 0;
        return len;
}

static struct md_sysfs_entry max_backlog_used =
__ATTR(max_backlog_used, S_IRUGO | S_IWUSR,
       behind_writes_used_show, behind_writes_used_reset);

static struct attribute *md_bitmap_attrs[] = {
        &bitmap_location.attr,
        &bitmap_space.attr,
        &bitmap_timeout.attr,
        &bitmap_backlog.attr,
        &bitmap_chunksize.attr,
        &bitmap_metadata.attr,
        &bitmap_can_clear.attr,
        &max_backlog_used.attr,
        NULL
};
const struct attribute_group md_bitmap_group = {
        .name = "bitmap",
        .attrs = md_bitmap_attrs,
};

static struct bitmap_operations bitmap_ops = {
        .enabled                = bitmap_enabled,
        .create                 = bitmap_create,
        .resize                 = bitmap_resize,
        .load                   = bitmap_load,
        .destroy                = bitmap_destroy,
        .flush                  = bitmap_flush,
        .write_all              = bitmap_write_all,
        .dirty_bits             = bitmap_dirty_bits,
        .unplug                 = bitmap_unplug,
        .daemon_work            = bitmap_daemon_work,
        .wait_behind_writes     = bitmap_wait_behind_writes,

        .startwrite             = bitmap_startwrite,
        .endwrite               = bitmap_endwrite,
        .start_sync             = bitmap_start_sync,
        .end_sync               = bitmap_end_sync,
        .cond_end_sync          = bitmap_cond_end_sync,
        .close_sync             = bitmap_close_sync,

        .update_sb              = bitmap_update_sb,
        .get_stats              = bitmap_get_stats,

        .sync_with_cluster      = bitmap_sync_with_cluster,
        .get_from_slot          = bitmap_get_from_slot,
        .copy_from_slot         = bitmap_copy_from_slot,
        .set_pages              = bitmap_set_pages,
        .free                   = md_bitmap_free,
};

void mddev_set_bitmap_ops(struct mddev *mddev)
{
        mddev->bitmap_ops = &bitmap_ops;
}