4 * Copyright (c) 1998-2010 The DragonFly Project. All rights reserved.
6 * This code is derived from software contributed to The DragonFly Project
7 * by Matthew Dillon <dillon@backplane.com>
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
19 * 3. Neither the name of The DragonFly Project nor the names of its
20 * contributors may be used to endorse or promote products derived
21 * from this software without specific, prior written permission.
23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
26 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
27 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
28 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
29 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
30 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
31 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
32 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
33 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * Copyright (c) 1994 John S. Dyson
37 * Copyright (c) 1990 University of Utah.
38 * Copyright (c) 1991, 1993
39 * The Regents of the University of California. All rights reserved.
41 * This code is derived from software contributed to Berkeley by
42 * the Systems Programming Group of the University of Utah Computer
45 * Redistribution and use in source and binary forms, with or without
46 * modification, are permitted provided that the following conditions
48 * 1. Redistributions of source code must retain the above copyright
49 * notice, this list of conditions and the following disclaimer.
50 * 2. Redistributions in binary form must reproduce the above copyright
51 * notice, this list of conditions and the following disclaimer in the
52 * documentation and/or other materials provided with the distribution.
53 * 3. Neither the name of the University nor the names of its contributors
54 * may be used to endorse or promote products derived from this software
55 * without specific prior written permission.
57 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
58 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
59 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
60 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
61 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
62 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
63 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
64 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
65 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
66 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
72 * Radix Bitmap 'blists'.
74 * - The new swapper uses the new radix bitmap code. This should scale
75 * to arbitrarily small or arbitrarily large swap spaces and an almost
76 * arbitrary degree of fragmentation.
80 * - on the fly reallocation of swap during putpages. The new system
81 * does not try to keep previously allocated swap blocks for dirty
84 * - on the fly deallocation of swap
86 * - No more garbage collection required. Unnecessarily allocated swap
87 * blocks only exist for dirty vm_page_t's now and these are already
88 * cycled (in a high-load system) by the pager. We also do on-the-fly
89 * removal of invalidated swap blocks when a page is destroyed
92 * from: Utah $Hdr: swap_pager.c 1.4 91/04/30$
93 * @(#)swap_pager.c 8.9 (Berkeley) 3/21/94
94 * $FreeBSD: src/sys/vm/swap_pager.c,v 1.130.2.12 2002/08/31 21:15:55 dillon Exp $
97 #include <sys/param.h>
98 #include <sys/systm.h>
100 #include <sys/kernel.h>
101 #include <sys/proc.h>
103 #include <sys/vnode.h>
104 #include <sys/malloc.h>
105 #include <sys/vmmeter.h>
106 #include <sys/sysctl.h>
107 #include <sys/blist.h>
108 #include <sys/lock.h>
109 #include <sys/kcollect.h>
112 #include "opt_swap.h"
114 #include <vm/vm_object.h>
115 #include <vm/vm_page.h>
116 #include <vm/vm_pager.h>
117 #include <vm/vm_pageout.h>
118 #include <vm/swap_pager.h>
119 #include <vm/vm_extern.h>
120 #include <vm/vm_zone.h>
121 #include <vm/vnode_pager.h>
123 #include <sys/thread2.h>
124 #include <sys/buf2.h>
125 #include <vm/vm_page2.h>
127 #ifndef MAX_PAGEOUT_CLUSTER
128 #define MAX_PAGEOUT_CLUSTER SWB_NPAGES
131 #define SWM_FREE 0x02 /* free, period */
132 #define SWM_POP 0x04 /* pop out */
134 #define SWBIO_READ 0x01
135 #define SWBIO_WRITE 0x02
136 #define SWBIO_SYNC 0x04
137 #define SWBIO_TTC 0x08 /* for VM_PAGER_TRY_TO_CACHE */
143 vm_pindex_t endi; /* inclusive */
146 struct swswapoffinfo {
153 * vm_swap_size is in page-sized chunks now. It was DEV_BSIZE'd chunks
157 int swap_pager_full; /* swap space exhaustion (task killing) */
158 int swap_fail_ticks; /* when we became exhausted */
159 int swap_pager_almost_full; /* swap space exhaustion (w/ hysteresis)*/
160 swblk_t vm_swap_cache_use;
161 swblk_t vm_swap_anon_use;
162 static int vm_report_swap_allocs;
164 static int nsw_rcount; /* free read buffers */
165 static int nsw_wcount_sync; /* limit write buffers / synchronous */
166 static int nsw_wcount_async; /* limit write buffers / asynchronous */
167 static int nsw_wcount_async_max;/* assigned maximum */
168 static int nsw_cluster_max; /* maximum VOP I/O allowed */
170 struct blist *swapblist;
171 static int swap_async_max = 4; /* maximum in-progress async I/O's */
172 static int swap_burst_read = 0; /* allow burst reading */
173 static swblk_t swapiterator; /* linearize allocations */
174 int swap_user_async = 0; /* user swap pager operation can be async */
176 static struct spinlock swapbp_spin = SPINLOCK_INITIALIZER(&swapbp_spin, "swapbp_spin");
179 extern struct vnode *swapdev_vp;
180 extern struct swdevt *swdevt;
183 #define BLK2DEVIDX(blk) (nswdev > 1 ? blk / SWB_DMMAX % nswdev : 0)
185 SYSCTL_INT(_vm, OID_AUTO, swap_async_max,
186 CTLFLAG_RW, &swap_async_max, 0, "Maximum running async swap ops");
187 SYSCTL_INT(_vm, OID_AUTO, swap_burst_read,
188 CTLFLAG_RW, &swap_burst_read, 0, "Allow burst reads for pageins");
189 SYSCTL_INT(_vm, OID_AUTO, swap_user_async,
190 CTLFLAG_RW, &swap_user_async, 0, "Allow async uuser swap write I/O");
193 SYSCTL_LONG(_vm, OID_AUTO, swap_cache_use,
194 CTLFLAG_RD, &vm_swap_cache_use, 0, "");
195 SYSCTL_LONG(_vm, OID_AUTO, swap_anon_use,
196 CTLFLAG_RD, &vm_swap_anon_use, 0, "");
197 SYSCTL_LONG(_vm, OID_AUTO, swap_size,
198 CTLFLAG_RD, &vm_swap_size, 0, "");
200 SYSCTL_INT(_vm, OID_AUTO, swap_cache_use,
201 CTLFLAG_RD, &vm_swap_cache_use, 0, "");
202 SYSCTL_INT(_vm, OID_AUTO, swap_anon_use,
203 CTLFLAG_RD, &vm_swap_anon_use, 0, "");
204 SYSCTL_INT(_vm, OID_AUTO, swap_size,
205 CTLFLAG_RD, &vm_swap_size, 0, "");
207 SYSCTL_INT(_vm, OID_AUTO, report_swap_allocs,
208 CTLFLAG_RW, &vm_report_swap_allocs, 0, "");
213 * Red-Black tree for swblock entries
215 * The caller must hold vm_token
217 RB_GENERATE2(swblock_rb_tree, swblock, swb_entry, rb_swblock_compare,
218 vm_pindex_t, swb_index);
221 rb_swblock_compare(struct swblock *swb1, struct swblock *swb2)
223 if (swb1->swb_index < swb2->swb_index)
225 if (swb1->swb_index > swb2->swb_index)
232 rb_swblock_scancmp(struct swblock *swb, void *data)
234 struct swfreeinfo *info = data;
236 if (swb->swb_index < info->basei)
238 if (swb->swb_index > info->endi)
245 rb_swblock_condcmp(struct swblock *swb, void *data)
247 struct swfreeinfo *info = data;
249 if (swb->swb_index < info->basei)
255 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
256 * calls hooked from other parts of the VM system and do not appear here.
257 * (see vm/swap_pager.h).
260 static void swap_pager_dealloc (vm_object_t object);
261 static int swap_pager_getpage (vm_object_t, vm_page_t *, int);
262 static void swap_chain_iodone(struct bio *biox);
264 struct pagerops swappagerops = {
265 swap_pager_dealloc, /* deallocate an OBJT_SWAP object */
266 swap_pager_getpage, /* pagein */
267 swap_pager_putpages, /* pageout */
268 swap_pager_haspage /* get backing store status for page */
272 * SWB_DMMAX is in page-sized chunks with the new swap system. It was
273 * dev-bsized chunks in the old. SWB_DMMAX is always a power of 2.
275 * swap_*() routines are externally accessible. swp_*() routines are
279 int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */
280 int nswap_hiwat = 512; /* in pages, swap_pager_almost_full warn */
282 static __inline void swp_sizecheck (void);
283 static void swp_pager_async_iodone (struct bio *bio);
286 * Swap bitmap functions
289 static __inline void swp_pager_freeswapspace(vm_object_t object,
290 swblk_t blk, int npages);
291 static __inline swblk_t swp_pager_getswapspace(vm_object_t object, int npages);
297 static void swp_pager_meta_convert(vm_object_t);
298 static void swp_pager_meta_build(vm_object_t, vm_pindex_t, swblk_t);
299 static void swp_pager_meta_free(vm_object_t, vm_pindex_t, vm_pindex_t);
300 static void swp_pager_meta_free_all(vm_object_t);
301 static swblk_t swp_pager_meta_ctl(vm_object_t, vm_pindex_t, int);
304 * SWP_SIZECHECK() - update swap_pager_full indication
306 * update the swap_pager_almost_full indication and warn when we are
307 * about to run out of swap space, using lowat/hiwat hysteresis.
309 * Clear swap_pager_full ( task killing ) indication when lowat is met.
311 * No restrictions on call
312 * This routine may not block.
318 if (vm_swap_size < nswap_lowat) {
319 if (swap_pager_almost_full == 0) {
320 kprintf("swap_pager: out of swap space\n");
321 swap_pager_almost_full = 1;
322 swap_fail_ticks = ticks;
326 if (vm_swap_size > nswap_hiwat)
327 swap_pager_almost_full = 0;
332 * Long-term data collection on 10-second interval. Return the value
333 * for KCOLLECT_SWAPPCT and set the values for SWAPANO and SWAPCCAC.
335 * Return total swap in the scale field. This can change if swap is
336 * regularly added or removed and may cause some historical confusion
337 * in that case, but SWAPPCT will always be historically accurate.
340 #define PTOB(value) ((uint64_t)(value) << PAGE_SHIFT)
343 collect_swap_callback(int n)
345 uint64_t total = vm_swap_max;
346 uint64_t anon = vm_swap_anon_use;
347 uint64_t cache = vm_swap_cache_use;
349 if (total == 0) /* avoid divide by zero */
351 kcollect_setvalue(KCOLLECT_SWAPANO, PTOB(anon));
352 kcollect_setvalue(KCOLLECT_SWAPCAC, PTOB(cache));
353 kcollect_setscale(KCOLLECT_SWAPANO,
354 KCOLLECT_SCALE(KCOLLECT_SWAPANO_FORMAT, PTOB(total)));
355 kcollect_setscale(KCOLLECT_SWAPCAC,
356 KCOLLECT_SCALE(KCOLLECT_SWAPCAC_FORMAT, PTOB(total)));
357 return (((anon + cache) * 10000 + (total >> 1)) / total);
361 * SWAP_PAGER_INIT() - initialize the swap pager!
363 * Expected to be started from system init. NOTE: This code is run
364 * before much else so be careful what you depend on. Most of the VM
365 * system has yet to be initialized at this point.
367 * Called from the low level boot code only.
370 swap_pager_init(void *arg __unused)
372 kcollect_register(KCOLLECT_SWAPPCT, "swapuse", collect_swap_callback,
373 KCOLLECT_SCALE(KCOLLECT_SWAPPCT_FORMAT, 0));
374 kcollect_register(KCOLLECT_SWAPANO, "swapano", NULL,
375 KCOLLECT_SCALE(KCOLLECT_SWAPANO_FORMAT, 0));
376 kcollect_register(KCOLLECT_SWAPCAC, "swapcac", NULL,
377 KCOLLECT_SCALE(KCOLLECT_SWAPCAC_FORMAT, 0));
379 SYSINIT(vm_mem, SI_BOOT1_VM, SI_ORDER_THIRD, swap_pager_init, NULL);
382 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
384 * Expected to be started from pageout process once, prior to entering
387 * Called from the low level boot code only.
390 swap_pager_swap_init(void)
395 * Number of in-transit swap bp operations. Don't
396 * exhaust the pbufs completely. Make sure we
397 * initialize workable values (0 will work for hysteresis
398 * but it isn't very efficient).
400 * The nsw_cluster_max is constrained by the number of pages an XIO
401 * holds, i.e., (MAXPHYS/PAGE_SIZE) and our locally defined
402 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
403 * constrained by the swap device interleave stripe size.
405 * Currently we hardwire nsw_wcount_async to 4. This limit is
406 * designed to prevent other I/O from having high latencies due to
407 * our pageout I/O. The value 4 works well for one or two active swap
408 * devices but is probably a little low if you have more. Even so,
409 * a higher value would probably generate only a limited improvement
410 * with three or four active swap devices since the system does not
411 * typically have to pageout at extreme bandwidths. We will want
412 * at least 2 per swap devices, and 4 is a pretty good value if you
413 * have one NFS swap device due to the command/ack latency over NFS.
414 * So it all works out pretty well.
417 nsw_cluster_max = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER);
419 nsw_rcount = (nswbuf_kva + 1) / 2;
420 nsw_wcount_sync = (nswbuf_kva + 3) / 4;
421 nsw_wcount_async = 4;
422 nsw_wcount_async_max = nsw_wcount_async;
425 * The zone is dynamically allocated so generally size it to
426 * maxswzone (32MB to 256GB of KVM). Set a minimum size based
427 * on physical memory of around 8x (each swblock can hold 16 pages).
429 * With the advent of SSDs (vs HDs) the practical (swap:memory) ratio
430 * has increased dramatically.
432 n = vmstats.v_page_count / 2;
433 if (maxswzone && n < maxswzone / sizeof(struct swblock))
434 n = maxswzone / sizeof(struct swblock);
440 sizeof(struct swblock),
443 if (swap_zone != NULL)
446 * if the allocation failed, try a zone two thirds the
447 * size of the previous attempt.
452 if (swap_zone == NULL)
453 panic("swap_pager_swap_init: swap_zone == NULL");
455 kprintf("Swap zone entries reduced from %d to %d.\n", n2, n);
459 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
460 * its metadata structures.
462 * This routine is called from the mmap and fork code to create a new
463 * OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object
464 * and then converting it with swp_pager_meta_convert().
466 * We only support unnamed objects.
471 swap_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset)
475 KKASSERT(handle == NULL);
476 object = vm_object_allocate_hold(OBJT_DEFAULT,
477 OFF_TO_IDX(offset + PAGE_MASK + size));
478 swp_pager_meta_convert(object);
479 vm_object_drop(object);
485 * SWAP_PAGER_DEALLOC() - remove swap metadata from object
487 * The swap backing for the object is destroyed. The code is
488 * designed such that we can reinstantiate it later, but this
489 * routine is typically called only when the entire object is
490 * about to be destroyed.
492 * The object must be locked or unreferenceable.
493 * No other requirements.
496 swap_pager_dealloc(vm_object_t object)
498 vm_object_hold(object);
499 vm_object_pip_wait(object, "swpdea");
502 * Free all remaining metadata. We only bother to free it from
503 * the swap meta data. We do not attempt to free swapblk's still
504 * associated with vm_page_t's for this object. We do not care
505 * if paging is still in progress on some objects.
507 swp_pager_meta_free_all(object);
508 vm_object_drop(object);
511 /************************************************************************
512 * SWAP PAGER BITMAP ROUTINES *
513 ************************************************************************/
516 * SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
518 * Allocate swap for the requested number of pages. The starting
519 * swap block number (a page index) is returned or SWAPBLK_NONE
520 * if the allocation failed.
522 * Also has the side effect of advising that somebody made a mistake
523 * when they configured swap and didn't configure enough.
525 * The caller must hold the object.
526 * This routine may not block.
528 static __inline swblk_t
529 swp_pager_getswapspace(vm_object_t object, int npages)
533 lwkt_gettoken(&vm_token);
534 blk = blist_allocat(swapblist, npages, swapiterator);
535 if (blk == SWAPBLK_NONE)
536 blk = blist_allocat(swapblist, npages, 0);
537 if (blk == SWAPBLK_NONE) {
538 if (swap_pager_full != 2) {
539 if (vm_swap_max == 0)
540 kprintf("Warning: The system would like to "
541 "page to swap but no swap space "
544 kprintf("swap_pager_getswapspace: "
545 "swap full allocating %d pages\n",
548 if (swap_pager_almost_full == 0)
549 swap_fail_ticks = ticks;
550 swap_pager_almost_full = 1;
553 /* swapiterator = blk; disable for now, doesn't work well */
554 swapacctspace(blk, -npages);
555 if (object->type == OBJT_SWAP)
556 vm_swap_anon_use += npages;
558 vm_swap_cache_use += npages;
561 lwkt_reltoken(&vm_token);
566 * SWP_PAGER_FREESWAPSPACE() - free raw swap space
568 * This routine returns the specified swap blocks back to the bitmap.
570 * Note: This routine may not block (it could in the old swap code),
571 * and through the use of the new blist routines it does not block.
573 * This routine may not block.
577 swp_pager_freeswapspace(vm_object_t object, swblk_t blk, int npages)
579 struct swdevt *sp = &swdevt[BLK2DEVIDX(blk)];
581 lwkt_gettoken(&vm_token);
582 sp->sw_nused -= npages;
583 if (object->type == OBJT_SWAP)
584 vm_swap_anon_use -= npages;
586 vm_swap_cache_use -= npages;
588 if (sp->sw_flags & SW_CLOSING) {
589 lwkt_reltoken(&vm_token);
593 blist_free(swapblist, blk, npages);
594 vm_swap_size += npages;
596 lwkt_reltoken(&vm_token);
600 * SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page
601 * range within an object.
603 * This is a globally accessible routine.
605 * This routine removes swapblk assignments from swap metadata.
607 * The external callers of this routine typically have already destroyed
608 * or renamed vm_page_t's associated with this range in the object so
614 swap_pager_freespace(vm_object_t object, vm_pindex_t start, vm_pindex_t size)
616 vm_object_hold(object);
617 swp_pager_meta_free(object, start, size);
618 vm_object_drop(object);
625 swap_pager_freespace_all(vm_object_t object)
627 vm_object_hold(object);
628 swp_pager_meta_free_all(object);
629 vm_object_drop(object);
633 * This function conditionally frees swap cache swap starting at
634 * (*basei) in the object. (count) swap blocks will be nominally freed.
635 * The actual number of blocks freed can be more or less than the
638 * This function nominally returns the number of blocks freed. However,
639 * the actual number of blocks freed may be less then the returned value.
640 * If the function is unable to exhaust the object or if it is able to
641 * free (approximately) the requested number of blocks it returns
644 * If we exhaust the object we will return a value n <= count.
646 * The caller must hold the object.
648 * WARNING! If count == 0 then -1 can be returned as a degenerate case,
649 * callers should always pass a count value > 0.
651 static int swap_pager_condfree_callback(struct swblock *swap, void *data);
654 swap_pager_condfree(vm_object_t object, vm_pindex_t *basei, int count)
656 struct swfreeinfo info;
660 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
662 info.object = object;
663 info.basei = *basei; /* skip up to this page index */
664 info.begi = count; /* max swap pages to destroy */
665 info.endi = count * 8; /* max swblocks to scan */
667 swblock_rb_tree_RB_SCAN(&object->swblock_root, rb_swblock_condcmp,
668 swap_pager_condfree_callback, &info);
672 * Take the higher difference swblocks vs pages
674 n = count - (int)info.begi;
675 t = count * 8 - (int)info.endi;
684 * The idea is to free whole meta-block to avoid fragmenting
685 * the swap space or disk I/O. We only do this if NO VM pages
688 * We do not have to deal with clearing PG_SWAPPED in related VM
689 * pages because there are no related VM pages.
691 * The caller must hold the object.
694 swap_pager_condfree_callback(struct swblock *swap, void *data)
696 struct swfreeinfo *info = data;
697 vm_object_t object = info->object;
700 for (i = 0; i < SWAP_META_PAGES; ++i) {
701 if (vm_page_lookup(object, swap->swb_index + i))
704 info->basei = swap->swb_index + SWAP_META_PAGES;
705 if (i == SWAP_META_PAGES) {
706 info->begi -= swap->swb_count;
707 swap_pager_freespace(object, swap->swb_index, SWAP_META_PAGES);
710 if ((int)info->begi < 0 || (int)info->endi < 0)
717 * Called by vm_page_alloc() when a new VM page is inserted
718 * into a VM object. Checks whether swap has been assigned to
719 * the page and sets PG_SWAPPED as necessary.
721 * (m) must be busied by caller and remains busied on return.
724 swap_pager_page_inserted(vm_page_t m)
726 if (m->object->swblock_count) {
727 vm_object_hold(m->object);
728 if (swp_pager_meta_ctl(m->object, m->pindex, 0) != SWAPBLK_NONE)
729 vm_page_flag_set(m, PG_SWAPPED);
730 vm_object_drop(m->object);
735 * SWAP_PAGER_RESERVE() - reserve swap blocks in object
737 * Assigns swap blocks to the specified range within the object. The
738 * swap blocks are not zerod. Any previous swap assignment is destroyed.
740 * Returns 0 on success, -1 on failure.
742 * The caller is responsible for avoiding races in the specified range.
743 * No other requirements.
746 swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
749 swblk_t blk = SWAPBLK_NONE;
750 vm_pindex_t beg = start; /* save start index */
752 vm_object_hold(object);
757 while ((blk = swp_pager_getswapspace(object, n)) ==
762 swp_pager_meta_free(object, beg,
764 vm_object_drop(object);
769 swp_pager_meta_build(object, start, blk);
775 swp_pager_meta_free(object, start, n);
776 vm_object_drop(object);
781 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
782 * and destroy the source.
784 * Copy any valid swapblks from the source to the destination. In
785 * cases where both the source and destination have a valid swapblk,
786 * we keep the destination's.
788 * This routine is allowed to block. It may block allocating metadata
789 * indirectly through swp_pager_meta_build() or if paging is still in
790 * progress on the source.
792 * XXX vm_page_collapse() kinda expects us not to block because we
793 * supposedly do not need to allocate memory, but for the moment we
794 * *may* have to get a little memory from the zone allocator, but
795 * it is taken from the interrupt memory. We should be ok.
797 * The source object contains no vm_page_t's (which is just as well)
798 * The source object is of type OBJT_SWAP.
800 * The source and destination objects must be held by the caller.
803 swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
804 vm_pindex_t base_index, int destroysource)
808 ASSERT_LWKT_TOKEN_HELD(vm_object_token(srcobject));
809 ASSERT_LWKT_TOKEN_HELD(vm_object_token(dstobject));
812 * transfer source to destination.
814 for (i = 0; i < dstobject->size; ++i) {
818 * Locate (without changing) the swapblk on the destination,
819 * unless it is invalid in which case free it silently, or
820 * if the destination is a resident page, in which case the
821 * source is thrown away.
823 dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
825 if (dstaddr == SWAPBLK_NONE) {
827 * Destination has no swapblk and is not resident,
832 srcaddr = swp_pager_meta_ctl(srcobject,
833 base_index + i, SWM_POP);
835 if (srcaddr != SWAPBLK_NONE)
836 swp_pager_meta_build(dstobject, i, srcaddr);
839 * Destination has valid swapblk or it is represented
840 * by a resident page. We destroy the sourceblock.
842 swp_pager_meta_ctl(srcobject, base_index + i, SWM_FREE);
847 * Free left over swap blocks in source.
849 * We have to revert the type to OBJT_DEFAULT so we do not accidently
850 * double-remove the object from the swap queues.
854 * Reverting the type is not necessary, the caller is going
855 * to destroy srcobject directly, but I'm doing it here
856 * for consistency since we've removed the object from its
859 swp_pager_meta_free_all(srcobject);
860 if (srcobject->type == OBJT_SWAP)
861 srcobject->type = OBJT_DEFAULT;
866 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for
867 * the requested page.
869 * We determine whether good backing store exists for the requested
870 * page and return TRUE if it does, FALSE if it doesn't.
872 * If TRUE, we also try to determine how much valid, contiguous backing
873 * store exists before and after the requested page within a reasonable
874 * distance. We do not try to restrict it to the swap device stripe
875 * (that is handled in getpages/putpages). It probably isn't worth
881 swap_pager_haspage(vm_object_t object, vm_pindex_t pindex)
886 * do we have good backing store at the requested index ?
888 vm_object_hold(object);
889 blk0 = swp_pager_meta_ctl(object, pindex, 0);
891 if (blk0 == SWAPBLK_NONE) {
892 vm_object_drop(object);
895 vm_object_drop(object);
900 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
902 * This removes any associated swap backing store, whether valid or
903 * not, from the page. This operates on any VM object, not just OBJT_SWAP
906 * This routine is typically called when a page is made dirty, at
907 * which point any associated swap can be freed. MADV_FREE also
908 * calls us in a special-case situation
910 * NOTE!!! If the page is clean and the swap was valid, the caller
911 * should make the page dirty before calling this routine.
912 * This routine does NOT change the m->dirty status of the page.
913 * Also: MADV_FREE depends on it.
915 * The page must be busied.
916 * The caller can hold the object to avoid blocking, else we might block.
917 * No other requirements.
920 swap_pager_unswapped(vm_page_t m)
922 if (m->flags & PG_SWAPPED) {
923 vm_object_hold(m->object);
924 KKASSERT(m->flags & PG_SWAPPED);
925 swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
926 vm_page_flag_clear(m, PG_SWAPPED);
927 vm_object_drop(m->object);
932 * SWAP_PAGER_STRATEGY() - read, write, free blocks
934 * This implements a VM OBJECT strategy function using swap backing store.
935 * This can operate on any VM OBJECT type, not necessarily just OBJT_SWAP
938 * This is intended to be a cacheless interface (i.e. caching occurs at
939 * higher levels), and is also used as a swap-based SSD cache for vnode
940 * and device objects.
942 * All I/O goes directly to and from the swap device.
944 * We currently attempt to run I/O synchronously or asynchronously as
945 * the caller requests. This isn't perfect because we loose error
946 * sequencing when we run multiple ops in parallel to satisfy a request.
947 * But this is swap, so we let it all hang out.
952 swap_pager_strategy(vm_object_t object, struct bio *bio)
954 struct buf *bp = bio->bio_buf;
957 vm_pindex_t biox_blkno = 0;
963 struct bio_track *track;
968 * tracking for swapdev vnode I/Os
970 if (bp->b_cmd == BUF_CMD_READ)
971 track = &swapdev_vp->v_track_read;
973 track = &swapdev_vp->v_track_write;
976 if (bp->b_bcount & PAGE_MASK) {
977 bp->b_error = EINVAL;
978 bp->b_flags |= B_ERROR | B_INVAL;
980 kprintf("swap_pager_strategy: bp %p offset %lld size %d, "
981 "not page bounded\n",
982 bp, (long long)bio->bio_offset, (int)bp->b_bcount);
987 * Clear error indication, initialize page index, count, data pointer.
990 bp->b_flags &= ~B_ERROR;
991 bp->b_resid = bp->b_bcount;
993 start = (vm_pindex_t)(bio->bio_offset >> PAGE_SHIFT);
994 count = howmany(bp->b_bcount, PAGE_SIZE);
998 * Deal with BUF_CMD_FREEBLKS
1000 if (bp->b_cmd == BUF_CMD_FREEBLKS) {
1002 * FREE PAGE(s) - destroy underlying swap that is no longer
1005 vm_object_hold(object);
1006 swp_pager_meta_free(object, start, count);
1007 vm_object_drop(object);
1014 * We need to be able to create a new cluster of I/O's. We cannot
1015 * use the caller fields of the passed bio so push a new one.
1017 * Because nbio is just a placeholder for the cluster links,
1018 * we can biodone() the original bio instead of nbio to make
1019 * things a bit more efficient.
1021 nbio = push_bio(bio);
1022 nbio->bio_offset = bio->bio_offset;
1023 nbio->bio_caller_info1.cluster_head = NULL;
1024 nbio->bio_caller_info2.cluster_tail = NULL;
1030 * Execute read or write
1032 vm_object_hold(object);
1038 * Obtain block. If block not found and writing, allocate a
1039 * new block and build it into the object.
1041 blk = swp_pager_meta_ctl(object, start, 0);
1042 if ((blk == SWAPBLK_NONE) && bp->b_cmd != BUF_CMD_READ) {
1043 blk = swp_pager_getswapspace(object, 1);
1044 if (blk == SWAPBLK_NONE) {
1045 bp->b_error = ENOMEM;
1046 bp->b_flags |= B_ERROR;
1049 swp_pager_meta_build(object, start, blk);
1053 * Do we have to flush our current collection? Yes if:
1055 * - no swap block at this index
1056 * - swap block is not contiguous
1057 * - we cross a physical disk boundry in the
1061 biox && (biox_blkno + btoc(bufx->b_bcount) != blk ||
1062 ((biox_blkno ^ blk) & ~SWB_DMMASK)
1065 if (bp->b_cmd == BUF_CMD_READ) {
1066 ++mycpu->gd_cnt.v_swapin;
1067 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
1069 ++mycpu->gd_cnt.v_swapout;
1070 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
1071 bufx->b_dirtyend = bufx->b_bcount;
1075 * Finished with this buf.
1077 KKASSERT(bufx->b_bcount != 0);
1078 if (bufx->b_cmd != BUF_CMD_READ)
1079 bufx->b_dirtyend = bufx->b_bcount;
1085 * Add new swapblk to biox, instantiating biox if necessary.
1086 * Zero-fill reads are able to take a shortcut.
1088 if (blk == SWAPBLK_NONE) {
1090 * We can only get here if we are reading.
1092 bzero(data, PAGE_SIZE);
1093 bp->b_resid -= PAGE_SIZE;
1096 /* XXX chain count > 4, wait to <= 4 */
1098 bufx = getpbuf(NULL);
1099 biox = &bufx->b_bio1;
1100 cluster_append(nbio, bufx);
1101 bufx->b_cmd = bp->b_cmd;
1102 biox->bio_done = swap_chain_iodone;
1103 biox->bio_offset = (off_t)blk << PAGE_SHIFT;
1104 biox->bio_caller_info1.cluster_parent = nbio;
1107 bufx->b_data = data;
1109 bufx->b_bcount += PAGE_SIZE;
1116 vm_object_drop(object);
1119 * Flush out last buffer
1122 if (bufx->b_cmd == BUF_CMD_READ) {
1123 ++mycpu->gd_cnt.v_swapin;
1124 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
1126 ++mycpu->gd_cnt.v_swapout;
1127 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
1128 bufx->b_dirtyend = bufx->b_bcount;
1130 KKASSERT(bufx->b_bcount);
1131 if (bufx->b_cmd != BUF_CMD_READ)
1132 bufx->b_dirtyend = bufx->b_bcount;
1133 /* biox, bufx = NULL */
1137 * Now initiate all the I/O. Be careful looping on our chain as
1138 * I/O's may complete while we are still initiating them.
1140 * If the request is a 100% sparse read no bios will be present
1141 * and we just biodone() the buffer.
1143 nbio->bio_caller_info2.cluster_tail = NULL;
1144 bufx = nbio->bio_caller_info1.cluster_head;
1148 biox = &bufx->b_bio1;
1150 bufx = bufx->b_cluster_next;
1151 vn_strategy(swapdev_vp, biox);
1158 * Completion of the cluster will also call biodone_chain(nbio).
1159 * We never call biodone(nbio) so we don't have to worry about
1160 * setting up a bio_done callback. It's handled in the sub-IO.
1171 swap_chain_iodone(struct bio *biox)
1174 struct buf *bufx; /* chained sub-buffer */
1175 struct bio *nbio; /* parent nbio with chain glue */
1176 struct buf *bp; /* original bp associated with nbio */
1179 bufx = biox->bio_buf;
1180 nbio = biox->bio_caller_info1.cluster_parent;
1184 * Update the original buffer
1186 KKASSERT(bp != NULL);
1187 if (bufx->b_flags & B_ERROR) {
1188 atomic_set_int(&bufx->b_flags, B_ERROR);
1189 bp->b_error = bufx->b_error; /* race ok */
1190 } else if (bufx->b_resid != 0) {
1191 atomic_set_int(&bufx->b_flags, B_ERROR);
1192 bp->b_error = EINVAL; /* race ok */
1194 atomic_subtract_int(&bp->b_resid, bufx->b_bcount);
1198 * Remove us from the chain.
1200 spin_lock(&swapbp_spin);
1201 nextp = &nbio->bio_caller_info1.cluster_head;
1202 while (*nextp != bufx) {
1203 KKASSERT(*nextp != NULL);
1204 nextp = &(*nextp)->b_cluster_next;
1206 *nextp = bufx->b_cluster_next;
1207 chain_empty = (nbio->bio_caller_info1.cluster_head == NULL);
1208 spin_unlock(&swapbp_spin);
1211 * Clean up bufx. If the chain is now empty we finish out
1212 * the parent. Note that we may be racing other completions
1213 * so we must use the chain_empty status from above.
1216 if (bp->b_resid != 0 && !(bp->b_flags & B_ERROR)) {
1217 atomic_set_int(&bp->b_flags, B_ERROR);
1218 bp->b_error = EINVAL;
1220 biodone_chain(nbio);
1222 relpbuf(bufx, NULL);
1226 * SWAP_PAGER_GETPAGES() - bring page in from swap
1228 * The requested page may have to be brought in from swap. Calculate the
1229 * swap block and bring in additional pages if possible. All pages must
1230 * have contiguous swap block assignments and reside in the same object.
1232 * The caller has a single vm_object_pip_add() reference prior to
1233 * calling us and we should return with the same.
1235 * The caller has BUSY'd the page. We should return with (*mpp) left busy,
1236 * and any additinal pages unbusied.
1238 * If the caller encounters a PG_RAM page it will pass it to us even though
1239 * it may be valid and dirty. We cannot overwrite the page in this case!
1240 * The case is used to allow us to issue pure read-aheads.
1242 * NOTE! XXX This code does not entirely pipeline yet due to the fact that
1243 * the PG_RAM page is validated at the same time as mreq. What we
1244 * really need to do is issue a separate read-ahead pbuf.
1249 swap_pager_getpage(vm_object_t object, vm_page_t *mpp, int seqaccess)
1262 vm_page_t marray[XIO_INTERNAL_PAGES];
1266 vm_object_hold(object);
1267 if (mreq->object != object) {
1268 panic("swap_pager_getpages: object mismatch %p/%p",
1275 * We don't want to overwrite a fully valid page as it might be
1276 * dirty. This case can occur when e.g. vm_fault hits a perfectly
1277 * valid page with PG_RAM set.
1279 * In this case we see if the next page is a suitable page-in
1280 * candidate and if it is we issue read-ahead. PG_RAM will be
1281 * set on the last page of the read-ahead to continue the pipeline.
1283 if (mreq->valid == VM_PAGE_BITS_ALL) {
1284 if (swap_burst_read == 0 || mreq->pindex + 1 >= object->size) {
1285 vm_object_drop(object);
1286 return(VM_PAGER_OK);
1288 blk = swp_pager_meta_ctl(object, mreq->pindex + 1, 0);
1289 if (blk == SWAPBLK_NONE) {
1290 vm_object_drop(object);
1291 return(VM_PAGER_OK);
1293 m = vm_page_lookup_busy_try(object, mreq->pindex + 1,
1296 vm_object_drop(object);
1297 return(VM_PAGER_OK);
1298 } else if (m == NULL) {
1300 * Use VM_ALLOC_QUICK to avoid blocking on cache
1303 m = vm_page_alloc(object, mreq->pindex + 1,
1306 vm_object_drop(object);
1307 return(VM_PAGER_OK);
1312 vm_object_drop(object);
1313 return(VM_PAGER_OK);
1315 vm_page_unqueue_nowakeup(m);
1325 * Try to block-read contiguous pages from swap if sequential,
1326 * otherwise just read one page. Contiguous pages from swap must
1327 * reside within a single device stripe because the I/O cannot be
1328 * broken up across multiple stripes.
1330 * Note that blk and iblk can be SWAPBLK_NONE but the loop is
1331 * set up such that the case(s) are handled implicitly.
1333 blk = swp_pager_meta_ctl(mreq->object, mreq->pindex, 0);
1336 for (i = 1; i <= swap_burst_read &&
1337 i < XIO_INTERNAL_PAGES &&
1338 mreq->pindex + i < object->size; ++i) {
1341 iblk = swp_pager_meta_ctl(object, mreq->pindex + i, 0);
1342 if (iblk != blk + i)
1344 if ((blk ^ iblk) & ~SWB_DMMASK)
1346 m = vm_page_lookup_busy_try(object, mreq->pindex + i,
1350 } else if (m == NULL) {
1352 * Use VM_ALLOC_QUICK to avoid blocking on cache
1355 m = vm_page_alloc(object, mreq->pindex + i,
1364 vm_page_unqueue_nowakeup(m);
1370 vm_page_flag_set(marray[i - 1], PG_RAM);
1373 * If mreq is the requested page and we have nothing to do return
1374 * VM_PAGER_FAIL. If raonly is set mreq is just another read-ahead
1375 * page and must be cleaned up.
1377 if (blk == SWAPBLK_NONE) {
1380 vnode_pager_freepage(mreq);
1381 vm_object_drop(object);
1382 return(VM_PAGER_OK);
1384 vm_object_drop(object);
1385 return(VM_PAGER_FAIL);
1390 * map our page(s) into kva for input
1392 bp = getpbuf_kva(&nsw_rcount);
1394 kva = (vm_offset_t) bp->b_kvabase;
1395 bcopy(marray, bp->b_xio.xio_pages, i * sizeof(vm_page_t));
1396 pmap_qenter(kva, bp->b_xio.xio_pages, i);
1398 bp->b_data = (caddr_t)kva;
1399 bp->b_bcount = PAGE_SIZE * i;
1400 bp->b_xio.xio_npages = i;
1401 bio->bio_done = swp_pager_async_iodone;
1402 bio->bio_offset = (off_t)blk << PAGE_SHIFT;
1403 bio->bio_caller_info1.index = SWBIO_READ;
1406 * Set index. If raonly set the index beyond the array so all
1407 * the pages are treated the same, otherwise the original mreq is
1411 bio->bio_driver_info = (void *)(intptr_t)i;
1413 bio->bio_driver_info = (void *)(intptr_t)0;
1415 for (j = 0; j < i; ++j)
1416 vm_page_flag_set(bp->b_xio.xio_pages[j], PG_SWAPINPROG);
1418 mycpu->gd_cnt.v_swapin++;
1419 mycpu->gd_cnt.v_swappgsin += bp->b_xio.xio_npages;
1422 * We still hold the lock on mreq, and our automatic completion routine
1423 * does not remove it.
1425 vm_object_pip_add(object, bp->b_xio.xio_npages);
1428 * perform the I/O. NOTE!!! bp cannot be considered valid after
1429 * this point because we automatically release it on completion.
1430 * Instead, we look at the one page we are interested in which we
1431 * still hold a lock on even through the I/O completion.
1433 * The other pages in our m[] array are also released on completion,
1434 * so we cannot assume they are valid anymore either.
1436 bp->b_cmd = BUF_CMD_READ;
1438 vn_strategy(swapdev_vp, bio);
1441 * Wait for the page we want to complete. PG_SWAPINPROG is always
1442 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE
1443 * is set in the meta-data.
1445 * If this is a read-ahead only we return immediately without
1449 vm_object_drop(object);
1450 return(VM_PAGER_OK);
1454 * Read-ahead includes originally requested page case.
1457 flags = mreq->flags;
1459 if ((flags & PG_SWAPINPROG) == 0)
1461 tsleep_interlock(mreq, 0);
1462 if (!atomic_cmpset_int(&mreq->flags, flags,
1463 flags | PG_WANTED | PG_REFERENCED)) {
1466 mycpu->gd_cnt.v_intrans++;
1467 if (tsleep(mreq, PINTERLOCKED, "swread", hz*20)) {
1469 "swap_pager: indefinite wait buffer: "
1470 " bp %p offset: %lld, size: %ld\n",
1472 (long long)bio->bio_offset,
1479 * Disallow speculative reads prior to the PG_SWAPINPROG test.
1484 * mreq is left busied after completion, but all the other pages
1485 * are freed. If we had an unrecoverable read error the page will
1488 vm_object_drop(object);
1489 if (mreq->valid != VM_PAGE_BITS_ALL)
1490 return(VM_PAGER_ERROR);
1492 return(VM_PAGER_OK);
1495 * A final note: in a low swap situation, we cannot deallocate swap
1496 * and mark a page dirty here because the caller is likely to mark
1497 * the page clean when we return, causing the page to possibly revert
1498 * to all-zero's later.
1503 * swap_pager_putpages:
1505 * Assign swap (if necessary) and initiate I/O on the specified pages.
1507 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
1508 * are automatically converted to SWAP objects.
1510 * In a low memory situation we may block in vn_strategy(), but the new
1511 * vm_page reservation system coupled with properly written VFS devices
1512 * should ensure that no low-memory deadlock occurs. This is an area
1515 * The parent has N vm_object_pip_add() references prior to
1516 * calling us and will remove references for rtvals[] that are
1517 * not set to VM_PAGER_PEND. We need to remove the rest on I/O
1520 * The parent has soft-busy'd the pages it passes us and will unbusy
1521 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
1522 * We need to unbusy the rest on I/O completion.
1527 swap_pager_putpages(vm_object_t object, vm_page_t *m, int count,
1528 int flags, int *rtvals)
1533 vm_object_hold(object);
1535 if (count && m[0]->object != object) {
1536 panic("swap_pager_getpages: object mismatch %p/%p",
1545 * Turn object into OBJT_SWAP
1546 * Check for bogus sysops
1548 * Force sync if not pageout process, we don't want any single
1549 * non-pageout process to be able to hog the I/O subsystem! This
1550 * can be overridden by setting.
1552 if (object->type == OBJT_DEFAULT) {
1553 if (object->type == OBJT_DEFAULT)
1554 swp_pager_meta_convert(object);
1558 * Normally we force synchronous swap I/O if this is not the
1559 * pageout daemon to prevent any single user process limited
1560 * via RLIMIT_RSS from hogging swap write bandwidth.
1562 if (curthread != pagethread &&
1563 curthread != emergpager &&
1564 swap_user_async == 0) {
1565 flags |= VM_PAGER_PUT_SYNC;
1571 * Update nsw parameters from swap_async_max sysctl values.
1572 * Do not let the sysop crash the machine with bogus numbers.
1574 if (swap_async_max != nsw_wcount_async_max) {
1580 if ((n = swap_async_max) > nswbuf_kva / 2)
1587 * Adjust difference ( if possible ). If the current async
1588 * count is too low, we may not be able to make the adjustment
1591 * vm_token needed for nsw_wcount sleep interlock
1593 lwkt_gettoken(&vm_token);
1594 n -= nsw_wcount_async_max;
1595 if (nsw_wcount_async + n >= 0) {
1596 nsw_wcount_async_max += n;
1597 pbuf_adjcount(&nsw_wcount_async, n);
1599 lwkt_reltoken(&vm_token);
1605 * Assign swap blocks and issue I/O. We reallocate swap on the fly.
1606 * The page is left dirty until the pageout operation completes
1610 for (i = 0; i < count; i += n) {
1617 * Maximum I/O size is limited by a number of factors.
1620 n = min(BLIST_MAX_ALLOC, count - i);
1621 n = min(n, nsw_cluster_max);
1623 lwkt_gettoken(&vm_token);
1626 * Get biggest block of swap we can. If we fail, fall
1627 * back and try to allocate a smaller block. Don't go
1628 * overboard trying to allocate space if it would overly
1632 (blk = swp_pager_getswapspace(object, n)) == SWAPBLK_NONE &&
1637 if (blk == SWAPBLK_NONE) {
1638 for (j = 0; j < n; ++j)
1639 rtvals[i+j] = VM_PAGER_FAIL;
1640 lwkt_reltoken(&vm_token);
1643 if (vm_report_swap_allocs > 0) {
1644 kprintf("swap_alloc %08jx,%d\n", (intmax_t)blk, n);
1645 --vm_report_swap_allocs;
1649 * The I/O we are constructing cannot cross a physical
1650 * disk boundry in the swap stripe.
1652 if ((blk ^ (blk + n)) & ~SWB_DMMASK) {
1653 j = ((blk + SWB_DMMAX) & ~SWB_DMMASK) - blk;
1654 swp_pager_freeswapspace(object, blk + j, n - j);
1659 * All I/O parameters have been satisfied, build the I/O
1660 * request and assign the swap space.
1662 if ((flags & VM_PAGER_PUT_SYNC))
1663 bp = getpbuf_kva(&nsw_wcount_sync);
1665 bp = getpbuf_kva(&nsw_wcount_async);
1668 lwkt_reltoken(&vm_token);
1670 pmap_qenter((vm_offset_t)bp->b_data, &m[i], n);
1672 bp->b_bcount = PAGE_SIZE * n;
1673 bio->bio_offset = (off_t)blk << PAGE_SHIFT;
1675 for (j = 0; j < n; ++j) {
1676 vm_page_t mreq = m[i+j];
1678 swp_pager_meta_build(mreq->object, mreq->pindex,
1680 if (object->type == OBJT_SWAP)
1681 vm_page_dirty(mreq);
1682 rtvals[i+j] = VM_PAGER_OK;
1684 vm_page_flag_set(mreq, PG_SWAPINPROG);
1685 bp->b_xio.xio_pages[j] = mreq;
1687 bp->b_xio.xio_npages = n;
1689 mycpu->gd_cnt.v_swapout++;
1690 mycpu->gd_cnt.v_swappgsout += bp->b_xio.xio_npages;
1692 bp->b_dirtyoff = 0; /* req'd for NFS */
1693 bp->b_dirtyend = bp->b_bcount; /* req'd for NFS */
1694 bp->b_cmd = BUF_CMD_WRITE;
1695 bio->bio_caller_info1.index = SWBIO_WRITE;
1698 /* PMAP TESTING CODE (useful, keep it in but #if 0'd) */
1699 bio->bio_crc = iscsi_crc32(bp->b_data, bp->b_bcount);
1702 for (j = 0; j < n; ++j) {
1703 vm_page_t mm = bp->b_xio.xio_pages[j];
1704 char *p = (char *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mm));
1705 crc = iscsi_crc32_ext(p, PAGE_SIZE, crc);
1707 if (bio->bio_crc != crc) {
1708 kprintf("PREWRITE MISMATCH-A "
1709 "bdata=%08x dmap=%08x bdata=%08x (%d)\n",
1712 iscsi_crc32(bp->b_data, bp->b_bcount),
1714 #ifdef _KERNEL_VIRTUAL
1715 madvise(bp->b_data, bp->b_bcount, MADV_INVAL);
1718 for (j = 0; j < n; ++j) {
1719 vm_page_t mm = bp->b_xio.xio_pages[j];
1720 char *p = (char *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mm));
1721 crc = iscsi_crc32_ext(p, PAGE_SIZE, crc);
1723 kprintf("PREWRITE MISMATCH-B "
1724 "bdata=%08x dmap=%08x\n",
1725 iscsi_crc32(bp->b_data, bp->b_bcount),
1734 if ((flags & VM_PAGER_PUT_SYNC) == 0) {
1735 bio->bio_done = swp_pager_async_iodone;
1737 vn_strategy(swapdev_vp, bio);
1739 for (j = 0; j < n; ++j)
1740 rtvals[i+j] = VM_PAGER_PEND;
1745 * Issue synchrnously.
1747 * Wait for the sync I/O to complete, then update rtvals.
1748 * We just set the rtvals[] to VM_PAGER_PEND so we can call
1749 * our async completion routine at the end, thus avoiding a
1752 bio->bio_caller_info1.index |= SWBIO_SYNC;
1753 if (flags & VM_PAGER_TRY_TO_CACHE)
1754 bio->bio_caller_info1.index |= SWBIO_TTC;
1755 bio->bio_done = biodone_sync;
1756 bio->bio_flags |= BIO_SYNC;
1757 vn_strategy(swapdev_vp, bio);
1758 biowait(bio, "swwrt");
1760 for (j = 0; j < n; ++j)
1761 rtvals[i+j] = VM_PAGER_PEND;
1764 * Now that we are through with the bp, we can call the
1765 * normal async completion, which frees everything up.
1767 swp_pager_async_iodone(bio);
1769 vm_object_drop(object);
1775 * Recalculate the low and high-water marks.
1778 swap_pager_newswap(void)
1781 * NOTE: vm_swap_max cannot exceed 1 billion blocks, which is the
1782 * limitation imposed by the blist code. Remember that this
1783 * will be divided by NSWAP_MAX (4), so each swap device is
1784 * limited to around a terrabyte.
1787 nswap_lowat = (int64_t)vm_swap_max * 4 / 100; /* 4% left */
1788 nswap_hiwat = (int64_t)vm_swap_max * 6 / 100; /* 6% left */
1789 kprintf("swap low/high-water marks set to %d/%d\n",
1790 nswap_lowat, nswap_hiwat);
1799 * swp_pager_async_iodone:
1801 * Completion routine for asynchronous reads and writes from/to swap.
1802 * Also called manually by synchronous code to finish up a bp.
1804 * For READ operations, the pages are PG_BUSY'd. For WRITE operations,
1805 * the pages are vm_page_t->busy'd. For READ operations, we PG_BUSY
1806 * unbusy all pages except the 'main' request page. For WRITE
1807 * operations, we vm_page_t->busy'd unbusy all pages ( we can do this
1808 * because we marked them all VM_PAGER_PEND on return from putpages ).
1810 * This routine may not block.
1815 swp_pager_async_iodone(struct bio *bio)
1817 struct buf *bp = bio->bio_buf;
1818 vm_object_t object = NULL;
1825 if (bp->b_flags & B_ERROR) {
1827 "swap_pager: I/O error - %s failed; offset %lld,"
1828 "size %ld, error %d\n",
1829 ((bio->bio_caller_info1.index & SWBIO_READ) ?
1830 "pagein" : "pageout"),
1831 (long long)bio->bio_offset,
1840 if (bp->b_xio.xio_npages)
1841 object = bp->b_xio.xio_pages[0]->object;
1844 /* PMAP TESTING CODE (useful, keep it in but #if 0'd) */
1845 if (bio->bio_caller_info1.index & SWBIO_WRITE) {
1846 if (bio->bio_crc != iscsi_crc32(bp->b_data, bp->b_bcount)) {
1847 kprintf("SWAPOUT: BADCRC %08x %08x\n",
1849 iscsi_crc32(bp->b_data, bp->b_bcount));
1850 for (i = 0; i < bp->b_xio.xio_npages; ++i) {
1851 vm_page_t m = bp->b_xio.xio_pages[i];
1852 if (m->flags & PG_WRITEABLE)
1854 "%d/%d %p writable\n",
1855 i, bp->b_xio.xio_npages, m);
1862 * remove the mapping for kernel virtual
1864 pmap_qremove((vm_offset_t)bp->b_data, bp->b_xio.xio_npages);
1867 * cleanup pages. If an error occurs writing to swap, we are in
1868 * very serious trouble. If it happens to be a disk error, though,
1869 * we may be able to recover by reassigning the swap later on. So
1870 * in this case we remove the m->swapblk assignment for the page
1871 * but do not free it in the rlist. The errornous block(s) are thus
1872 * never reallocated as swap. Redirty the page and continue.
1874 for (i = 0; i < bp->b_xio.xio_npages; ++i) {
1875 vm_page_t m = bp->b_xio.xio_pages[i];
1877 if (bp->b_flags & B_ERROR) {
1879 * If an error occurs I'd love to throw the swapblk
1880 * away without freeing it back to swapspace, so it
1881 * can never be used again. But I can't from an
1885 if (bio->bio_caller_info1.index & SWBIO_READ) {
1887 * When reading, reqpage needs to stay
1888 * locked for the parent, but all other
1889 * pages can be freed. We still want to
1890 * wakeup the parent waiting on the page,
1891 * though. ( also: pg_reqpage can be -1 and
1892 * not match anything ).
1894 * We have to wake specifically requested pages
1895 * up too because we cleared PG_SWAPINPROG and
1896 * someone may be waiting for that.
1898 * NOTE: For reads, m->dirty will probably
1899 * be overridden by the original caller
1900 * of getpages so don't play cute tricks
1903 * NOTE: We can't actually free the page from
1904 * here, because this is an interrupt.
1905 * It is not legal to mess with
1906 * object->memq from an interrupt.
1907 * Deactivate the page instead.
1909 * WARNING! The instant PG_SWAPINPROG is
1910 * cleared another cpu may start
1911 * using the mreq page (it will
1912 * check m->valid immediately).
1916 vm_page_flag_clear(m, PG_SWAPINPROG);
1919 * bio_driver_info holds the requested page
1922 if (i != (int)(intptr_t)bio->bio_driver_info) {
1923 vm_page_deactivate(m);
1929 * If i == bp->b_pager.pg_reqpage, do not wake
1930 * the page up. The caller needs to.
1934 * If a write error occurs remove the swap
1935 * assignment (note that PG_SWAPPED may or
1936 * may not be set depending on prior activity).
1938 * Re-dirty OBJT_SWAP pages as there is no
1939 * other backing store, we can't throw the
1942 * Non-OBJT_SWAP pages (aka swapcache) must
1943 * not be dirtied since they may not have
1944 * been dirty in the first place, and they
1945 * do have backing store (the vnode).
1947 vm_page_busy_wait(m, FALSE, "swadpg");
1948 vm_object_hold(m->object);
1949 swp_pager_meta_ctl(m->object, m->pindex,
1951 vm_page_flag_clear(m, PG_SWAPPED);
1952 vm_object_drop(m->object);
1953 if (m->object->type == OBJT_SWAP) {
1955 vm_page_activate(m);
1957 vm_page_io_finish(m);
1958 vm_page_flag_clear(m, PG_SWAPINPROG);
1961 } else if (bio->bio_caller_info1.index & SWBIO_READ) {
1963 * NOTE: for reads, m->dirty will probably be
1964 * overridden by the original caller of getpages so
1965 * we cannot set them in order to free the underlying
1966 * swap in a low-swap situation. I don't think we'd
1967 * want to do that anyway, but it was an optimization
1968 * that existed in the old swapper for a time before
1969 * it got ripped out due to precisely this problem.
1971 * If not the requested page then deactivate it.
1973 * Note that the requested page, reqpage, is left
1974 * busied, but we still have to wake it up. The
1975 * other pages are released (unbusied) by
1976 * vm_page_wakeup(). We do not set reqpage's
1977 * valid bits here, it is up to the caller.
1981 * NOTE: Can't call pmap_clear_modify(m) from an
1982 * interrupt thread, the pmap code may have to
1983 * map non-kernel pmaps and currently asserts
1986 * WARNING! The instant PG_SWAPINPROG is
1987 * cleared another cpu may start
1988 * using the mreq page (it will
1989 * check m->valid immediately).
1991 /*pmap_clear_modify(m);*/
1992 m->valid = VM_PAGE_BITS_ALL;
1994 vm_page_flag_set(m, PG_SWAPPED);
1995 vm_page_flag_clear(m, PG_SWAPINPROG);
1998 * We have to wake specifically requested pages
1999 * up too because we cleared PG_SWAPINPROG and
2000 * could be waiting for it in getpages. However,
2001 * be sure to not unbusy getpages specifically
2002 * requested page - getpages expects it to be
2005 * bio_driver_info holds the requested page
2007 if (i != (int)(intptr_t)bio->bio_driver_info) {
2008 vm_page_deactivate(m);
2015 * Mark the page clean but do not mess with the
2016 * pmap-layer's modified state. That state should
2017 * also be clear since the caller protected the
2018 * page VM_PROT_READ, but allow the case.
2020 * We are in an interrupt, avoid pmap operations.
2022 * If we have a severe page deficit, deactivate the
2023 * page. Do not try to cache it (which would also
2024 * involve a pmap op), because the page might still
2027 * When using the swap to cache clean vnode pages
2028 * we do not mess with the page dirty bits.
2030 * NOTE! Nobody is waiting for the key mreq page
2031 * on write completion.
2033 vm_page_busy_wait(m, FALSE, "swadpg");
2034 if (m->object->type == OBJT_SWAP)
2036 vm_page_flag_set(m, PG_SWAPPED);
2037 vm_page_flag_clear(m, PG_SWAPINPROG);
2038 if (vm_page_count_severe())
2039 vm_page_deactivate(m);
2040 vm_page_io_finish(m);
2041 if (bio->bio_caller_info1.index & SWBIO_TTC)
2042 vm_page_try_to_cache(m);
2049 * adjust pip. NOTE: the original parent may still have its own
2050 * pip refs on the object.
2054 vm_object_pip_wakeup_n(object, bp->b_xio.xio_npages);
2057 * Release the physical I/O buffer.
2059 * NOTE: Due to synchronous operations in the write case b_cmd may
2060 * already be set to BUF_CMD_DONE and BIO_SYNC may have already
2063 * Use vm_token to interlock nsw_rcount/wcount wakeup?
2065 lwkt_gettoken(&vm_token);
2066 if (bio->bio_caller_info1.index & SWBIO_READ)
2067 nswptr = &nsw_rcount;
2068 else if (bio->bio_caller_info1.index & SWBIO_SYNC)
2069 nswptr = &nsw_wcount_sync;
2071 nswptr = &nsw_wcount_async;
2072 bp->b_cmd = BUF_CMD_DONE;
2073 relpbuf(bp, nswptr);
2074 lwkt_reltoken(&vm_token);
2078 * Fault-in a potentially swapped page and remove the swap reference.
2079 * (used by swapoff code)
2081 * object must be held.
2083 static __inline void
2084 swp_pager_fault_page(vm_object_t object, int *sharedp, vm_pindex_t pindex)
2090 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
2092 if (object->type == OBJT_VNODE) {
2094 * Any swap related to a vnode is due to swapcache. We must
2095 * vget() the vnode in case it is not active (otherwise
2096 * vref() will panic). Calling vm_object_page_remove() will
2097 * ensure that any swap ref is removed interlocked with the
2098 * page. clean_only is set to TRUE so we don't throw away
2101 vp = object->handle;
2102 error = vget(vp, LK_SHARED | LK_RETRY | LK_CANRECURSE);
2104 vm_object_page_remove(object, pindex, pindex + 1, TRUE);
2109 * Otherwise it is a normal OBJT_SWAP object and we can
2110 * fault the page in and remove the swap.
2112 m = vm_fault_object_page(object, IDX_TO_OFF(pindex),
2114 VM_FAULT_DIRTY | VM_FAULT_UNSWAP,
2122 * This removes all swap blocks related to a particular device. We have
2123 * to be careful of ripups during the scan.
2125 static int swp_pager_swapoff_callback(struct swblock *swap, void *data);
2128 swap_pager_swapoff(int devidx)
2130 struct vm_object_hash *hash;
2131 struct swswapoffinfo info;
2132 struct vm_object marker;
2136 bzero(&marker, sizeof(marker));
2137 marker.type = OBJT_MARKER;
2139 for (n = 0; n < VMOBJ_HSIZE; ++n) {
2140 hash = &vm_object_hash[n];
2142 lwkt_gettoken(&hash->token);
2143 TAILQ_INSERT_HEAD(&hash->list, &marker, object_list);
2145 while ((object = TAILQ_NEXT(&marker, object_list)) != NULL) {
2146 if (object->type == OBJT_MARKER)
2148 if (object->type != OBJT_SWAP &&
2149 object->type != OBJT_VNODE)
2151 vm_object_hold(object);
2152 if (object->type != OBJT_SWAP &&
2153 object->type != OBJT_VNODE) {
2154 vm_object_drop(object);
2159 * Object is special in that we can't just pagein
2160 * into vm_page's in it (tmpfs, vn).
2162 if ((object->flags & OBJ_NOPAGEIN) &&
2163 RB_ROOT(&object->swblock_root)) {
2164 vm_object_drop(object);
2168 info.object = object;
2170 info.devidx = devidx;
2171 swblock_rb_tree_RB_SCAN(&object->swblock_root,
2172 NULL, swp_pager_swapoff_callback,
2174 vm_object_drop(object);
2176 if (object == TAILQ_NEXT(&marker, object_list)) {
2177 TAILQ_REMOVE(&hash->list, &marker, object_list);
2178 TAILQ_INSERT_AFTER(&hash->list, object,
2179 &marker, object_list);
2182 TAILQ_REMOVE(&hash->list, &marker, object_list);
2183 lwkt_reltoken(&hash->token);
2187 * If we fail to locate all swblocks we just fail gracefully and
2188 * do not bother to restore paging on the swap device. If the
2189 * user wants to retry the user can retry.
2191 if (swdevt[devidx].sw_nused)
2199 swp_pager_swapoff_callback(struct swblock *swap, void *data)
2201 struct swswapoffinfo *info = data;
2202 vm_object_t object = info->object;
2207 index = swap->swb_index;
2208 for (i = 0; i < SWAP_META_PAGES; ++i) {
2210 * Make sure we don't race a dying object. This will
2211 * kill the scan of the object's swap blocks entirely.
2213 if (object->flags & OBJ_DEAD)
2217 * Fault the page, which can obviously block. If the swap
2218 * structure disappears break out.
2220 v = swap->swb_pages[i];
2221 if (v != SWAPBLK_NONE && BLK2DEVIDX(v) == info->devidx) {
2222 swp_pager_fault_page(object, &info->shared,
2223 swap->swb_index + i);
2224 /* swap ptr might go away */
2225 if (RB_LOOKUP(swblock_rb_tree,
2226 &object->swblock_root, index) != swap) {
2234 /************************************************************************
2236 ************************************************************************
2238 * These routines manipulate the swap metadata stored in the
2241 * Swap metadata is implemented with a global hash and not directly
2242 * linked into the object. Instead the object simply contains
2243 * appropriate tracking counters.
2247 * Lookup the swblock containing the specified swap block index.
2249 * The caller must hold the object.
2253 swp_pager_lookup(vm_object_t object, vm_pindex_t index)
2255 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
2256 index &= ~(vm_pindex_t)SWAP_META_MASK;
2257 return (RB_LOOKUP(swblock_rb_tree, &object->swblock_root, index));
2261 * Remove a swblock from the RB tree.
2263 * The caller must hold the object.
2267 swp_pager_remove(vm_object_t object, struct swblock *swap)
2269 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
2270 RB_REMOVE(swblock_rb_tree, &object->swblock_root, swap);
2274 * Convert default object to swap object if necessary
2276 * The caller must hold the object.
2279 swp_pager_meta_convert(vm_object_t object)
2281 if (object->type == OBJT_DEFAULT) {
2282 object->type = OBJT_SWAP;
2283 KKASSERT(object->swblock_count == 0);
2288 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
2290 * We first convert the object to a swap object if it is a default
2291 * object. Vnode objects do not need to be converted.
2293 * The specified swapblk is added to the object's swap metadata. If
2294 * the swapblk is not valid, it is freed instead. Any previously
2295 * assigned swapblk is freed.
2297 * The caller must hold the object.
2300 swp_pager_meta_build(vm_object_t object, vm_pindex_t index, swblk_t swapblk)
2302 struct swblock *swap;
2303 struct swblock *oswap;
2306 KKASSERT(swapblk != SWAPBLK_NONE);
2307 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
2310 * Convert object if necessary
2312 if (object->type == OBJT_DEFAULT)
2313 swp_pager_meta_convert(object);
2316 * Locate swblock. If not found create, but if we aren't adding
2317 * anything just return. If we run out of space in the map we wait
2318 * and, since the hash table may have changed, retry.
2321 swap = swp_pager_lookup(object, index);
2326 swap = zalloc(swap_zone);
2331 swap->swb_index = index & ~(vm_pindex_t)SWAP_META_MASK;
2332 swap->swb_count = 0;
2334 ++object->swblock_count;
2336 for (i = 0; i < SWAP_META_PAGES; ++i)
2337 swap->swb_pages[i] = SWAPBLK_NONE;
2338 oswap = RB_INSERT(swblock_rb_tree, &object->swblock_root, swap);
2339 KKASSERT(oswap == NULL);
2343 * Delete prior contents of metadata.
2345 * NOTE: Decrement swb_count after the freeing operation (which
2346 * might block) to prevent racing destruction of the swblock.
2348 index &= SWAP_META_MASK;
2350 while ((v = swap->swb_pages[index]) != SWAPBLK_NONE) {
2351 swap->swb_pages[index] = SWAPBLK_NONE;
2353 swp_pager_freeswapspace(object, v, 1);
2355 --mycpu->gd_vmtotal.t_vm;
2359 * Enter block into metadata
2361 swap->swb_pages[index] = swapblk;
2362 if (swapblk != SWAPBLK_NONE) {
2364 ++mycpu->gd_vmtotal.t_vm;
2369 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
2371 * The requested range of blocks is freed, with any associated swap
2372 * returned to the swap bitmap.
2374 * This routine will free swap metadata structures as they are cleaned
2375 * out. This routine does *NOT* operate on swap metadata associated
2376 * with resident pages.
2378 * The caller must hold the object.
2380 static int swp_pager_meta_free_callback(struct swblock *swb, void *data);
2383 swp_pager_meta_free(vm_object_t object, vm_pindex_t index, vm_pindex_t count)
2385 struct swfreeinfo info;
2387 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
2392 if (object->swblock_count == 0) {
2393 KKASSERT(RB_EMPTY(&object->swblock_root));
2400 * Setup for RB tree scan. Note that the pindex range can be huge
2401 * due to the 64 bit page index space so we cannot safely iterate.
2403 info.object = object;
2404 info.basei = index & ~(vm_pindex_t)SWAP_META_MASK;
2406 info.endi = index + count - 1;
2407 swblock_rb_tree_RB_SCAN(&object->swblock_root, rb_swblock_scancmp,
2408 swp_pager_meta_free_callback, &info);
2412 * The caller must hold the object.
2416 swp_pager_meta_free_callback(struct swblock *swap, void *data)
2418 struct swfreeinfo *info = data;
2419 vm_object_t object = info->object;
2424 * Figure out the range within the swblock. The wider scan may
2425 * return edge-case swap blocks when the start and/or end points
2426 * are in the middle of a block.
2428 if (swap->swb_index < info->begi)
2429 index = (int)info->begi & SWAP_META_MASK;
2433 if (swap->swb_index + SWAP_META_PAGES > info->endi)
2434 eindex = (int)info->endi & SWAP_META_MASK;
2436 eindex = SWAP_META_MASK;
2439 * Scan and free the blocks. The loop terminates early
2440 * if (swap) runs out of blocks and could be freed.
2442 * NOTE: Decrement swb_count after swp_pager_freeswapspace()
2443 * to deal with a zfree race.
2445 while (index <= eindex) {
2446 swblk_t v = swap->swb_pages[index];
2448 if (v != SWAPBLK_NONE) {
2449 swap->swb_pages[index] = SWAPBLK_NONE;
2451 swp_pager_freeswapspace(object, v, 1);
2452 --mycpu->gd_vmtotal.t_vm;
2453 if (--swap->swb_count == 0) {
2454 swp_pager_remove(object, swap);
2455 zfree(swap_zone, swap);
2456 --object->swblock_count;
2463 /* swap may be invalid here due to zfree above */
2470 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
2472 * This routine locates and destroys all swap metadata associated with
2475 * NOTE: Decrement swb_count after the freeing operation (which
2476 * might block) to prevent racing destruction of the swblock.
2478 * The caller must hold the object.
2481 swp_pager_meta_free_all(vm_object_t object)
2483 struct swblock *swap;
2486 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
2488 while ((swap = RB_ROOT(&object->swblock_root)) != NULL) {
2489 swp_pager_remove(object, swap);
2490 for (i = 0; i < SWAP_META_PAGES; ++i) {
2491 swblk_t v = swap->swb_pages[i];
2492 if (v != SWAPBLK_NONE) {
2494 swp_pager_freeswapspace(object, v, 1);
2496 --mycpu->gd_vmtotal.t_vm;
2499 if (swap->swb_count != 0)
2500 panic("swap_pager_meta_free_all: swb_count != 0");
2501 zfree(swap_zone, swap);
2502 --object->swblock_count;
2505 KKASSERT(object->swblock_count == 0);
2509 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
2511 * This routine is capable of looking up, popping, or freeing
2512 * swapblk assignments in the swap meta data or in the vm_page_t.
2513 * The routine typically returns the swapblk being looked-up, or popped,
2514 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
2515 * was invalid. This routine will automatically free any invalid
2516 * meta-data swapblks.
2518 * It is not possible to store invalid swapblks in the swap meta data
2519 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
2521 * When acting on a busy resident page and paging is in progress, we
2522 * have to wait until paging is complete but otherwise can act on the
2525 * SWM_FREE remove and free swap block from metadata
2526 * SWM_POP remove from meta data but do not free.. pop it out
2528 * The caller must hold the object.
2531 swp_pager_meta_ctl(vm_object_t object, vm_pindex_t index, int flags)
2533 struct swblock *swap;
2536 if (object->swblock_count == 0)
2537 return(SWAPBLK_NONE);
2540 swap = swp_pager_lookup(object, index);
2543 index &= SWAP_META_MASK;
2544 r1 = swap->swb_pages[index];
2546 if (r1 != SWAPBLK_NONE) {
2547 if (flags & (SWM_FREE|SWM_POP)) {
2548 swap->swb_pages[index] = SWAPBLK_NONE;
2549 --mycpu->gd_vmtotal.t_vm;
2550 if (--swap->swb_count == 0) {
2551 swp_pager_remove(object, swap);
2552 zfree(swap_zone, swap);
2553 --object->swblock_count;
2556 /* swap ptr may be invalid */
2557 if (flags & SWM_FREE) {
2558 swp_pager_freeswapspace(object, r1, 1);
2562 /* swap ptr may be invalid */