4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
9 #include <linux/sched/mm.h>
10 #include <linux/sched/task.h>
11 #include <linux/hugetlb.h>
12 #include <linux/mman.h>
13 #include <linux/slab.h>
14 #include <linux/kernel_stat.h>
15 #include <linux/swap.h>
16 #include <linux/vmalloc.h>
17 #include <linux/pagemap.h>
18 #include <linux/namei.h>
19 #include <linux/shmem_fs.h>
20 #include <linux/blkdev.h>
21 #include <linux/random.h>
22 #include <linux/writeback.h>
23 #include <linux/proc_fs.h>
24 #include <linux/seq_file.h>
25 #include <linux/init.h>
26 #include <linux/ksm.h>
27 #include <linux/rmap.h>
28 #include <linux/security.h>
29 #include <linux/backing-dev.h>
30 #include <linux/mutex.h>
31 #include <linux/capability.h>
32 #include <linux/syscalls.h>
33 #include <linux/memcontrol.h>
34 #include <linux/poll.h>
35 #include <linux/oom.h>
36 #include <linux/frontswap.h>
37 #include <linux/swapfile.h>
38 #include <linux/export.h>
39 #include <linux/swap_slots.h>
40 #include <linux/sort.h>
42 #include <asm/pgtable.h>
43 #include <asm/tlbflush.h>
44 #include <linux/swapops.h>
45 #include <linux/swap_cgroup.h>
47 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
49 static void free_swap_count_continuations(struct swap_info_struct *);
50 static sector_t map_swap_entry(swp_entry_t, struct block_device**);
52 DEFINE_SPINLOCK(swap_lock);
53 static unsigned int nr_swapfiles;
54 atomic_long_t nr_swap_pages;
56 * Some modules use swappable objects and may try to swap them out under
57 * memory pressure (via the shrinker). Before doing so, they may wish to
58 * check to see if any swap space is available.
60 EXPORT_SYMBOL_GPL(nr_swap_pages);
61 /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
62 long total_swap_pages;
63 static int least_priority = -1;
65 static const char Bad_file[] = "Bad swap file entry ";
66 static const char Unused_file[] = "Unused swap file entry ";
67 static const char Bad_offset[] = "Bad swap offset entry ";
68 static const char Unused_offset[] = "Unused swap offset entry ";
71 * all active swap_info_structs
72 * protected with swap_lock, and ordered by priority.
74 PLIST_HEAD(swap_active_head);
77 * all available (active, not full) swap_info_structs
78 * protected with swap_avail_lock, ordered by priority.
79 * This is used by get_swap_page() instead of swap_active_head
80 * because swap_active_head includes all swap_info_structs,
81 * but get_swap_page() doesn't need to look at full ones.
82 * This uses its own lock instead of swap_lock because when a
83 * swap_info_struct changes between not-full/full, it needs to
84 * add/remove itself to/from this list, but the swap_info_struct->lock
85 * is held and the locking order requires swap_lock to be taken
86 * before any swap_info_struct->lock.
88 static struct plist_head *swap_avail_heads;
89 static DEFINE_SPINLOCK(swap_avail_lock);
91 struct swap_info_struct *swap_info[MAX_SWAPFILES];
93 static DEFINE_MUTEX(swapon_mutex);
95 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
96 /* Activity counter to indicate that a swapon or swapoff has occurred */
97 static atomic_t proc_poll_event = ATOMIC_INIT(0);
99 atomic_t nr_rotate_swap = ATOMIC_INIT(0);
101 static struct swap_info_struct *swap_type_to_swap_info(int type)
103 if (type >= READ_ONCE(nr_swapfiles))
106 smp_rmb(); /* Pairs with smp_wmb in alloc_swap_info. */
107 return READ_ONCE(swap_info[type]);
110 static inline unsigned char swap_count(unsigned char ent)
112 return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
115 /* Reclaim the swap entry anyway if possible */
116 #define TTRS_ANYWAY 0x1
118 * Reclaim the swap entry if there are no more mappings of the
121 #define TTRS_UNMAPPED 0x2
122 /* Reclaim the swap entry if swap is getting full*/
123 #define TTRS_FULL 0x4
125 /* returns 1 if swap entry is freed */
126 static int __try_to_reclaim_swap(struct swap_info_struct *si,
127 unsigned long offset, unsigned long flags)
129 swp_entry_t entry = swp_entry(si->type, offset);
133 page = find_get_page(swap_address_space(entry), offset);
137 * When this function is called from scan_swap_map_slots() and it's
138 * called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
139 * here. We have to use trylock for avoiding deadlock. This is a special
140 * case and you should use try_to_free_swap() with explicit lock_page()
141 * in usual operations.
143 if (trylock_page(page)) {
144 if ((flags & TTRS_ANYWAY) ||
145 ((flags & TTRS_UNMAPPED) && !page_mapped(page)) ||
146 ((flags & TTRS_FULL) && mem_cgroup_swap_full(page)))
147 ret = try_to_free_swap(page);
155 * swapon tell device that all the old swap contents can be discarded,
156 * to allow the swap device to optimize its wear-levelling.
158 static int discard_swap(struct swap_info_struct *si)
160 struct swap_extent *se;
161 sector_t start_block;
165 /* Do not discard the swap header page! */
166 se = &si->first_swap_extent;
167 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
168 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
170 err = blkdev_issue_discard(si->bdev, start_block,
171 nr_blocks, GFP_KERNEL, 0);
177 list_for_each_entry(se, &si->first_swap_extent.list, list) {
178 start_block = se->start_block << (PAGE_SHIFT - 9);
179 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
181 err = blkdev_issue_discard(si->bdev, start_block,
182 nr_blocks, GFP_KERNEL, 0);
188 return err; /* That will often be -EOPNOTSUPP */
192 * swap allocation tell device that a cluster of swap can now be discarded,
193 * to allow the swap device to optimize its wear-levelling.
195 static void discard_swap_cluster(struct swap_info_struct *si,
196 pgoff_t start_page, pgoff_t nr_pages)
198 struct swap_extent *se = si->curr_swap_extent;
199 int found_extent = 0;
202 if (se->start_page <= start_page &&
203 start_page < se->start_page + se->nr_pages) {
204 pgoff_t offset = start_page - se->start_page;
205 sector_t start_block = se->start_block + offset;
206 sector_t nr_blocks = se->nr_pages - offset;
208 if (nr_blocks > nr_pages)
209 nr_blocks = nr_pages;
210 start_page += nr_blocks;
211 nr_pages -= nr_blocks;
214 si->curr_swap_extent = se;
216 start_block <<= PAGE_SHIFT - 9;
217 nr_blocks <<= PAGE_SHIFT - 9;
218 if (blkdev_issue_discard(si->bdev, start_block,
219 nr_blocks, GFP_NOIO, 0))
223 se = list_next_entry(se, list);
227 #ifdef CONFIG_THP_SWAP
228 #define SWAPFILE_CLUSTER HPAGE_PMD_NR
230 #define swap_entry_size(size) (size)
232 #define SWAPFILE_CLUSTER 256
235 * Define swap_entry_size() as constant to let compiler to optimize
236 * out some code if !CONFIG_THP_SWAP
238 #define swap_entry_size(size) 1
240 #define LATENCY_LIMIT 256
242 static inline void cluster_set_flag(struct swap_cluster_info *info,
248 static inline unsigned int cluster_count(struct swap_cluster_info *info)
253 static inline void cluster_set_count(struct swap_cluster_info *info,
259 static inline void cluster_set_count_flag(struct swap_cluster_info *info,
260 unsigned int c, unsigned int f)
266 static inline unsigned int cluster_next(struct swap_cluster_info *info)
271 static inline void cluster_set_next(struct swap_cluster_info *info,
277 static inline void cluster_set_next_flag(struct swap_cluster_info *info,
278 unsigned int n, unsigned int f)
284 static inline bool cluster_is_free(struct swap_cluster_info *info)
286 return info->flags & CLUSTER_FLAG_FREE;
289 static inline bool cluster_is_null(struct swap_cluster_info *info)
291 return info->flags & CLUSTER_FLAG_NEXT_NULL;
294 static inline void cluster_set_null(struct swap_cluster_info *info)
296 info->flags = CLUSTER_FLAG_NEXT_NULL;
300 static inline bool cluster_is_huge(struct swap_cluster_info *info)
302 if (IS_ENABLED(CONFIG_THP_SWAP))
303 return info->flags & CLUSTER_FLAG_HUGE;
307 static inline void cluster_clear_huge(struct swap_cluster_info *info)
309 info->flags &= ~CLUSTER_FLAG_HUGE;
312 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
313 unsigned long offset)
315 struct swap_cluster_info *ci;
317 ci = si->cluster_info;
319 ci += offset / SWAPFILE_CLUSTER;
320 spin_lock(&ci->lock);
325 static inline void unlock_cluster(struct swap_cluster_info *ci)
328 spin_unlock(&ci->lock);
332 * Determine the locking method in use for this device. Return
333 * swap_cluster_info if SSD-style cluster-based locking is in place.
335 static inline struct swap_cluster_info *lock_cluster_or_swap_info(
336 struct swap_info_struct *si, unsigned long offset)
338 struct swap_cluster_info *ci;
340 /* Try to use fine-grained SSD-style locking if available: */
341 ci = lock_cluster(si, offset);
342 /* Otherwise, fall back to traditional, coarse locking: */
344 spin_lock(&si->lock);
349 static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
350 struct swap_cluster_info *ci)
355 spin_unlock(&si->lock);
358 static inline bool cluster_list_empty(struct swap_cluster_list *list)
360 return cluster_is_null(&list->head);
363 static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
365 return cluster_next(&list->head);
368 static void cluster_list_init(struct swap_cluster_list *list)
370 cluster_set_null(&list->head);
371 cluster_set_null(&list->tail);
374 static void cluster_list_add_tail(struct swap_cluster_list *list,
375 struct swap_cluster_info *ci,
378 if (cluster_list_empty(list)) {
379 cluster_set_next_flag(&list->head, idx, 0);
380 cluster_set_next_flag(&list->tail, idx, 0);
382 struct swap_cluster_info *ci_tail;
383 unsigned int tail = cluster_next(&list->tail);
386 * Nested cluster lock, but both cluster locks are
387 * only acquired when we held swap_info_struct->lock
390 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
391 cluster_set_next(ci_tail, idx);
392 spin_unlock(&ci_tail->lock);
393 cluster_set_next_flag(&list->tail, idx, 0);
397 static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
398 struct swap_cluster_info *ci)
402 idx = cluster_next(&list->head);
403 if (cluster_next(&list->tail) == idx) {
404 cluster_set_null(&list->head);
405 cluster_set_null(&list->tail);
407 cluster_set_next_flag(&list->head,
408 cluster_next(&ci[idx]), 0);
413 /* Add a cluster to discard list and schedule it to do discard */
414 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
418 * If scan_swap_map() can't find a free cluster, it will check
419 * si->swap_map directly. To make sure the discarding cluster isn't
420 * taken by scan_swap_map(), mark the swap entries bad (occupied). It
421 * will be cleared after discard
423 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
424 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
426 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
428 schedule_work(&si->discard_work);
431 static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
433 struct swap_cluster_info *ci = si->cluster_info;
435 cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
436 cluster_list_add_tail(&si->free_clusters, ci, idx);
440 * Doing discard actually. After a cluster discard is finished, the cluster
441 * will be added to free cluster list. caller should hold si->lock.
443 static void swap_do_scheduled_discard(struct swap_info_struct *si)
445 struct swap_cluster_info *info, *ci;
448 info = si->cluster_info;
450 while (!cluster_list_empty(&si->discard_clusters)) {
451 idx = cluster_list_del_first(&si->discard_clusters, info);
452 spin_unlock(&si->lock);
454 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
457 spin_lock(&si->lock);
458 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
459 __free_cluster(si, idx);
460 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
461 0, SWAPFILE_CLUSTER);
466 static void swap_discard_work(struct work_struct *work)
468 struct swap_info_struct *si;
470 si = container_of(work, struct swap_info_struct, discard_work);
472 spin_lock(&si->lock);
473 swap_do_scheduled_discard(si);
474 spin_unlock(&si->lock);
477 static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
479 struct swap_cluster_info *ci = si->cluster_info;
481 VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
482 cluster_list_del_first(&si->free_clusters, ci);
483 cluster_set_count_flag(ci + idx, 0, 0);
486 static void free_cluster(struct swap_info_struct *si, unsigned long idx)
488 struct swap_cluster_info *ci = si->cluster_info + idx;
490 VM_BUG_ON(cluster_count(ci) != 0);
492 * If the swap is discardable, prepare discard the cluster
493 * instead of free it immediately. The cluster will be freed
496 if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
497 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
498 swap_cluster_schedule_discard(si, idx);
502 __free_cluster(si, idx);
506 * The cluster corresponding to page_nr will be used. The cluster will be
507 * removed from free cluster list and its usage counter will be increased.
509 static void inc_cluster_info_page(struct swap_info_struct *p,
510 struct swap_cluster_info *cluster_info, unsigned long page_nr)
512 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
516 if (cluster_is_free(&cluster_info[idx]))
517 alloc_cluster(p, idx);
519 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
520 cluster_set_count(&cluster_info[idx],
521 cluster_count(&cluster_info[idx]) + 1);
525 * The cluster corresponding to page_nr decreases one usage. If the usage
526 * counter becomes 0, which means no page in the cluster is in using, we can
527 * optionally discard the cluster and add it to free cluster list.
529 static void dec_cluster_info_page(struct swap_info_struct *p,
530 struct swap_cluster_info *cluster_info, unsigned long page_nr)
532 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
537 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
538 cluster_set_count(&cluster_info[idx],
539 cluster_count(&cluster_info[idx]) - 1);
541 if (cluster_count(&cluster_info[idx]) == 0)
542 free_cluster(p, idx);
546 * It's possible scan_swap_map() uses a free cluster in the middle of free
547 * cluster list. Avoiding such abuse to avoid list corruption.
550 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
551 unsigned long offset)
553 struct percpu_cluster *percpu_cluster;
556 offset /= SWAPFILE_CLUSTER;
557 conflict = !cluster_list_empty(&si->free_clusters) &&
558 offset != cluster_list_first(&si->free_clusters) &&
559 cluster_is_free(&si->cluster_info[offset]);
564 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
565 cluster_set_null(&percpu_cluster->index);
570 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
571 * might involve allocating a new cluster for current CPU too.
573 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
574 unsigned long *offset, unsigned long *scan_base)
576 struct percpu_cluster *cluster;
577 struct swap_cluster_info *ci;
579 unsigned long tmp, max;
582 cluster = this_cpu_ptr(si->percpu_cluster);
583 if (cluster_is_null(&cluster->index)) {
584 if (!cluster_list_empty(&si->free_clusters)) {
585 cluster->index = si->free_clusters.head;
586 cluster->next = cluster_next(&cluster->index) *
588 } else if (!cluster_list_empty(&si->discard_clusters)) {
590 * we don't have free cluster but have some clusters in
591 * discarding, do discard now and reclaim them
593 swap_do_scheduled_discard(si);
594 *scan_base = *offset = si->cluster_next;
603 * Other CPUs can use our cluster if they can't find a free cluster,
604 * check if there is still free entry in the cluster
607 max = min_t(unsigned long, si->max,
608 (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
610 cluster_set_null(&cluster->index);
613 ci = lock_cluster(si, tmp);
615 if (!si->swap_map[tmp]) {
623 cluster_set_null(&cluster->index);
626 cluster->next = tmp + 1;
632 static void __del_from_avail_list(struct swap_info_struct *p)
637 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
640 static void del_from_avail_list(struct swap_info_struct *p)
642 spin_lock(&swap_avail_lock);
643 __del_from_avail_list(p);
644 spin_unlock(&swap_avail_lock);
647 static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
648 unsigned int nr_entries)
650 unsigned int end = offset + nr_entries - 1;
652 if (offset == si->lowest_bit)
653 si->lowest_bit += nr_entries;
654 if (end == si->highest_bit)
655 si->highest_bit -= nr_entries;
656 si->inuse_pages += nr_entries;
657 if (si->inuse_pages == si->pages) {
658 si->lowest_bit = si->max;
660 del_from_avail_list(si);
664 static void add_to_avail_list(struct swap_info_struct *p)
668 spin_lock(&swap_avail_lock);
670 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
671 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
673 spin_unlock(&swap_avail_lock);
676 static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
677 unsigned int nr_entries)
679 unsigned long end = offset + nr_entries - 1;
680 void (*swap_slot_free_notify)(struct block_device *, unsigned long);
682 if (offset < si->lowest_bit)
683 si->lowest_bit = offset;
684 if (end > si->highest_bit) {
685 bool was_full = !si->highest_bit;
687 si->highest_bit = end;
688 if (was_full && (si->flags & SWP_WRITEOK))
689 add_to_avail_list(si);
691 atomic_long_add(nr_entries, &nr_swap_pages);
692 si->inuse_pages -= nr_entries;
693 if (si->flags & SWP_BLKDEV)
694 swap_slot_free_notify =
695 si->bdev->bd_disk->fops->swap_slot_free_notify;
697 swap_slot_free_notify = NULL;
698 while (offset <= end) {
699 frontswap_invalidate_page(si->type, offset);
700 if (swap_slot_free_notify)
701 swap_slot_free_notify(si->bdev, offset);
706 static int scan_swap_map_slots(struct swap_info_struct *si,
707 unsigned char usage, int nr,
710 struct swap_cluster_info *ci;
711 unsigned long offset;
712 unsigned long scan_base;
713 unsigned long last_in_cluster = 0;
714 int latency_ration = LATENCY_LIMIT;
721 * We try to cluster swap pages by allocating them sequentially
722 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
723 * way, however, we resort to first-free allocation, starting
724 * a new cluster. This prevents us from scattering swap pages
725 * all over the entire swap partition, so that we reduce
726 * overall disk seek times between swap pages. -- sct
727 * But we do now try to find an empty cluster. -Andrea
728 * And we let swap pages go all over an SSD partition. Hugh
731 si->flags += SWP_SCANNING;
732 scan_base = offset = si->cluster_next;
735 if (si->cluster_info) {
736 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
742 if (unlikely(!si->cluster_nr--)) {
743 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
744 si->cluster_nr = SWAPFILE_CLUSTER - 1;
748 spin_unlock(&si->lock);
751 * If seek is expensive, start searching for new cluster from
752 * start of partition, to minimize the span of allocated swap.
753 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
754 * case, just handled by scan_swap_map_try_ssd_cluster() above.
756 scan_base = offset = si->lowest_bit;
757 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
759 /* Locate the first empty (unaligned) cluster */
760 for (; last_in_cluster <= si->highest_bit; offset++) {
761 if (si->swap_map[offset])
762 last_in_cluster = offset + SWAPFILE_CLUSTER;
763 else if (offset == last_in_cluster) {
764 spin_lock(&si->lock);
765 offset -= SWAPFILE_CLUSTER - 1;
766 si->cluster_next = offset;
767 si->cluster_nr = SWAPFILE_CLUSTER - 1;
770 if (unlikely(--latency_ration < 0)) {
772 latency_ration = LATENCY_LIMIT;
777 spin_lock(&si->lock);
778 si->cluster_nr = SWAPFILE_CLUSTER - 1;
782 if (si->cluster_info) {
783 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
784 /* take a break if we already got some slots */
787 if (!scan_swap_map_try_ssd_cluster(si, &offset,
792 if (!(si->flags & SWP_WRITEOK))
794 if (!si->highest_bit)
796 if (offset > si->highest_bit)
797 scan_base = offset = si->lowest_bit;
799 ci = lock_cluster(si, offset);
800 /* reuse swap entry of cache-only swap if not busy. */
801 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
804 spin_unlock(&si->lock);
805 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
806 spin_lock(&si->lock);
807 /* entry was freed successfully, try to use this again */
810 goto scan; /* check next one */
813 if (si->swap_map[offset]) {
820 si->swap_map[offset] = usage;
821 inc_cluster_info_page(si, si->cluster_info, offset);
824 swap_range_alloc(si, offset, 1);
825 si->cluster_next = offset + 1;
826 slots[n_ret++] = swp_entry(si->type, offset);
828 /* got enough slots or reach max slots? */
829 if ((n_ret == nr) || (offset >= si->highest_bit))
832 /* search for next available slot */
834 /* time to take a break? */
835 if (unlikely(--latency_ration < 0)) {
838 spin_unlock(&si->lock);
840 spin_lock(&si->lock);
841 latency_ration = LATENCY_LIMIT;
844 /* try to get more slots in cluster */
845 if (si->cluster_info) {
846 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
854 /* non-ssd case, still more slots in cluster? */
855 if (si->cluster_nr && !si->swap_map[offset]) {
861 si->flags -= SWP_SCANNING;
865 spin_unlock(&si->lock);
866 while (++offset <= si->highest_bit) {
867 if (!si->swap_map[offset]) {
868 spin_lock(&si->lock);
871 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
872 spin_lock(&si->lock);
875 if (unlikely(--latency_ration < 0)) {
877 latency_ration = LATENCY_LIMIT;
880 offset = si->lowest_bit;
881 while (offset < scan_base) {
882 if (!si->swap_map[offset]) {
883 spin_lock(&si->lock);
886 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
887 spin_lock(&si->lock);
890 if (unlikely(--latency_ration < 0)) {
892 latency_ration = LATENCY_LIMIT;
896 spin_lock(&si->lock);
899 si->flags -= SWP_SCANNING;
903 static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
906 struct swap_cluster_info *ci;
907 unsigned long offset, i;
911 * Should not even be attempting cluster allocations when huge
912 * page swap is disabled. Warn and fail the allocation.
914 if (!IS_ENABLED(CONFIG_THP_SWAP)) {
919 if (cluster_list_empty(&si->free_clusters))
922 idx = cluster_list_first(&si->free_clusters);
923 offset = idx * SWAPFILE_CLUSTER;
924 ci = lock_cluster(si, offset);
925 alloc_cluster(si, idx);
926 cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
928 map = si->swap_map + offset;
929 for (i = 0; i < SWAPFILE_CLUSTER; i++)
930 map[i] = SWAP_HAS_CACHE;
932 swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
933 *slot = swp_entry(si->type, offset);
938 static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
940 unsigned long offset = idx * SWAPFILE_CLUSTER;
941 struct swap_cluster_info *ci;
943 ci = lock_cluster(si, offset);
944 memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
945 cluster_set_count_flag(ci, 0, 0);
946 free_cluster(si, idx);
948 swap_range_free(si, offset, SWAPFILE_CLUSTER);
951 static unsigned long scan_swap_map(struct swap_info_struct *si,
957 n_ret = scan_swap_map_slots(si, usage, 1, &entry);
960 return swp_offset(entry);
966 int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
968 unsigned long size = swap_entry_size(entry_size);
969 struct swap_info_struct *si, *next;
974 /* Only single cluster request supported */
975 WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
977 avail_pgs = atomic_long_read(&nr_swap_pages) / size;
981 if (n_goal > SWAP_BATCH)
984 if (n_goal > avail_pgs)
987 atomic_long_sub(n_goal * size, &nr_swap_pages);
989 spin_lock(&swap_avail_lock);
992 node = numa_node_id();
993 plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
994 /* requeue si to after same-priority siblings */
995 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
996 spin_unlock(&swap_avail_lock);
997 spin_lock(&si->lock);
998 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
999 spin_lock(&swap_avail_lock);
1000 if (plist_node_empty(&si->avail_lists[node])) {
1001 spin_unlock(&si->lock);
1004 WARN(!si->highest_bit,
1005 "swap_info %d in list but !highest_bit\n",
1007 WARN(!(si->flags & SWP_WRITEOK),
1008 "swap_info %d in list but !SWP_WRITEOK\n",
1010 __del_from_avail_list(si);
1011 spin_unlock(&si->lock);
1014 if (size == SWAPFILE_CLUSTER) {
1015 if (!(si->flags & SWP_FS))
1016 n_ret = swap_alloc_cluster(si, swp_entries);
1018 n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1019 n_goal, swp_entries);
1020 spin_unlock(&si->lock);
1021 if (n_ret || size == SWAPFILE_CLUSTER)
1023 pr_debug("scan_swap_map of si %d failed to find offset\n",
1026 spin_lock(&swap_avail_lock);
1029 * if we got here, it's likely that si was almost full before,
1030 * and since scan_swap_map() can drop the si->lock, multiple
1031 * callers probably all tried to get a page from the same si
1032 * and it filled up before we could get one; or, the si filled
1033 * up between us dropping swap_avail_lock and taking si->lock.
1034 * Since we dropped the swap_avail_lock, the swap_avail_head
1035 * list may have been modified; so if next is still in the
1036 * swap_avail_head list then try it, otherwise start over
1037 * if we have not gotten any slots.
1039 if (plist_node_empty(&next->avail_lists[node]))
1043 spin_unlock(&swap_avail_lock);
1047 atomic_long_add((long)(n_goal - n_ret) * size,
1053 /* The only caller of this function is now suspend routine */
1054 swp_entry_t get_swap_page_of_type(int type)
1056 struct swap_info_struct *si = swap_type_to_swap_info(type);
1062 spin_lock(&si->lock);
1063 if (si->flags & SWP_WRITEOK) {
1064 atomic_long_dec(&nr_swap_pages);
1065 /* This is called for allocating swap entry, not cache */
1066 offset = scan_swap_map(si, 1);
1068 spin_unlock(&si->lock);
1069 return swp_entry(type, offset);
1071 atomic_long_inc(&nr_swap_pages);
1073 spin_unlock(&si->lock);
1075 return (swp_entry_t) {0};
1078 static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
1080 struct swap_info_struct *p;
1081 unsigned long offset, type;
1085 type = swp_type(entry);
1086 p = swap_type_to_swap_info(type);
1089 if (!(p->flags & SWP_USED))
1091 offset = swp_offset(entry);
1092 if (offset >= p->max)
1097 pr_err("swap_info_get: %s%08lx\n", Bad_offset, entry.val);
1100 pr_err("swap_info_get: %s%08lx\n", Unused_file, entry.val);
1103 pr_err("swap_info_get: %s%08lx\n", Bad_file, entry.val);
1108 static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1110 struct swap_info_struct *p;
1112 p = __swap_info_get(entry);
1115 if (!p->swap_map[swp_offset(entry)])
1120 pr_err("swap_info_get: %s%08lx\n", Unused_offset, entry.val);
1126 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
1128 struct swap_info_struct *p;
1130 p = _swap_info_get(entry);
1132 spin_lock(&p->lock);
1136 static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1137 struct swap_info_struct *q)
1139 struct swap_info_struct *p;
1141 p = _swap_info_get(entry);
1145 spin_unlock(&q->lock);
1147 spin_lock(&p->lock);
1152 static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1153 unsigned long offset,
1154 unsigned char usage)
1156 unsigned char count;
1157 unsigned char has_cache;
1159 count = p->swap_map[offset];
1161 has_cache = count & SWAP_HAS_CACHE;
1162 count &= ~SWAP_HAS_CACHE;
1164 if (usage == SWAP_HAS_CACHE) {
1165 VM_BUG_ON(!has_cache);
1167 } else if (count == SWAP_MAP_SHMEM) {
1169 * Or we could insist on shmem.c using a special
1170 * swap_shmem_free() and free_shmem_swap_and_cache()...
1173 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1174 if (count == COUNT_CONTINUED) {
1175 if (swap_count_continued(p, offset, count))
1176 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1178 count = SWAP_MAP_MAX;
1183 usage = count | has_cache;
1184 p->swap_map[offset] = usage ? : SWAP_HAS_CACHE;
1189 static unsigned char __swap_entry_free(struct swap_info_struct *p,
1190 swp_entry_t entry, unsigned char usage)
1192 struct swap_cluster_info *ci;
1193 unsigned long offset = swp_offset(entry);
1195 ci = lock_cluster_or_swap_info(p, offset);
1196 usage = __swap_entry_free_locked(p, offset, usage);
1197 unlock_cluster_or_swap_info(p, ci);
1199 free_swap_slot(entry);
1204 static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1206 struct swap_cluster_info *ci;
1207 unsigned long offset = swp_offset(entry);
1208 unsigned char count;
1210 ci = lock_cluster(p, offset);
1211 count = p->swap_map[offset];
1212 VM_BUG_ON(count != SWAP_HAS_CACHE);
1213 p->swap_map[offset] = 0;
1214 dec_cluster_info_page(p, p->cluster_info, offset);
1217 mem_cgroup_uncharge_swap(entry, 1);
1218 swap_range_free(p, offset, 1);
1222 * Caller has made sure that the swap device corresponding to entry
1223 * is still around or has not been recycled.
1225 void swap_free(swp_entry_t entry)
1227 struct swap_info_struct *p;
1229 p = _swap_info_get(entry);
1231 __swap_entry_free(p, entry, 1);
1235 * Called after dropping swapcache to decrease refcnt to swap entries.
1237 void put_swap_page(struct page *page, swp_entry_t entry)
1239 unsigned long offset = swp_offset(entry);
1240 unsigned long idx = offset / SWAPFILE_CLUSTER;
1241 struct swap_cluster_info *ci;
1242 struct swap_info_struct *si;
1244 unsigned int i, free_entries = 0;
1246 int size = swap_entry_size(hpage_nr_pages(page));
1248 si = _swap_info_get(entry);
1252 ci = lock_cluster_or_swap_info(si, offset);
1253 if (size == SWAPFILE_CLUSTER) {
1254 VM_BUG_ON(!cluster_is_huge(ci));
1255 map = si->swap_map + offset;
1256 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1258 VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1259 if (val == SWAP_HAS_CACHE)
1262 cluster_clear_huge(ci);
1263 if (free_entries == SWAPFILE_CLUSTER) {
1264 unlock_cluster_or_swap_info(si, ci);
1265 spin_lock(&si->lock);
1266 mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1267 swap_free_cluster(si, idx);
1268 spin_unlock(&si->lock);
1272 for (i = 0; i < size; i++, entry.val++) {
1273 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1274 unlock_cluster_or_swap_info(si, ci);
1275 free_swap_slot(entry);
1278 lock_cluster_or_swap_info(si, offset);
1281 unlock_cluster_or_swap_info(si, ci);
1284 #ifdef CONFIG_THP_SWAP
1285 int split_swap_cluster(swp_entry_t entry)
1287 struct swap_info_struct *si;
1288 struct swap_cluster_info *ci;
1289 unsigned long offset = swp_offset(entry);
1291 si = _swap_info_get(entry);
1294 ci = lock_cluster(si, offset);
1295 cluster_clear_huge(ci);
1301 static int swp_entry_cmp(const void *ent1, const void *ent2)
1303 const swp_entry_t *e1 = ent1, *e2 = ent2;
1305 return (int)swp_type(*e1) - (int)swp_type(*e2);
1308 void swapcache_free_entries(swp_entry_t *entries, int n)
1310 struct swap_info_struct *p, *prev;
1320 * Sort swap entries by swap device, so each lock is only taken once.
1321 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1322 * so low that it isn't necessary to optimize further.
1324 if (nr_swapfiles > 1)
1325 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1326 for (i = 0; i < n; ++i) {
1327 p = swap_info_get_cont(entries[i], prev);
1329 swap_entry_free(p, entries[i]);
1333 spin_unlock(&p->lock);
1337 * How many references to page are currently swapped out?
1338 * This does not give an exact answer when swap count is continued,
1339 * but does include the high COUNT_CONTINUED flag to allow for that.
1341 int page_swapcount(struct page *page)
1344 struct swap_info_struct *p;
1345 struct swap_cluster_info *ci;
1347 unsigned long offset;
1349 entry.val = page_private(page);
1350 p = _swap_info_get(entry);
1352 offset = swp_offset(entry);
1353 ci = lock_cluster_or_swap_info(p, offset);
1354 count = swap_count(p->swap_map[offset]);
1355 unlock_cluster_or_swap_info(p, ci);
1360 int __swap_count(struct swap_info_struct *si, swp_entry_t entry)
1362 pgoff_t offset = swp_offset(entry);
1364 return swap_count(si->swap_map[offset]);
1367 static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1370 pgoff_t offset = swp_offset(entry);
1371 struct swap_cluster_info *ci;
1373 ci = lock_cluster_or_swap_info(si, offset);
1374 count = swap_count(si->swap_map[offset]);
1375 unlock_cluster_or_swap_info(si, ci);
1380 * How many references to @entry are currently swapped out?
1381 * This does not give an exact answer when swap count is continued,
1382 * but does include the high COUNT_CONTINUED flag to allow for that.
1384 int __swp_swapcount(swp_entry_t entry)
1387 struct swap_info_struct *si;
1389 si = __swap_info_get(entry);
1391 count = swap_swapcount(si, entry);
1396 * How many references to @entry are currently swapped out?
1397 * This considers COUNT_CONTINUED so it returns exact answer.
1399 int swp_swapcount(swp_entry_t entry)
1401 int count, tmp_count, n;
1402 struct swap_info_struct *p;
1403 struct swap_cluster_info *ci;
1408 p = _swap_info_get(entry);
1412 offset = swp_offset(entry);
1414 ci = lock_cluster_or_swap_info(p, offset);
1416 count = swap_count(p->swap_map[offset]);
1417 if (!(count & COUNT_CONTINUED))
1420 count &= ~COUNT_CONTINUED;
1421 n = SWAP_MAP_MAX + 1;
1423 page = vmalloc_to_page(p->swap_map + offset);
1424 offset &= ~PAGE_MASK;
1425 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1428 page = list_next_entry(page, lru);
1429 map = kmap_atomic(page);
1430 tmp_count = map[offset];
1433 count += (tmp_count & ~COUNT_CONTINUED) * n;
1434 n *= (SWAP_CONT_MAX + 1);
1435 } while (tmp_count & COUNT_CONTINUED);
1437 unlock_cluster_or_swap_info(p, ci);
1441 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1444 struct swap_cluster_info *ci;
1445 unsigned char *map = si->swap_map;
1446 unsigned long roffset = swp_offset(entry);
1447 unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1451 ci = lock_cluster_or_swap_info(si, offset);
1452 if (!ci || !cluster_is_huge(ci)) {
1453 if (swap_count(map[roffset]))
1457 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1458 if (swap_count(map[offset + i])) {
1464 unlock_cluster_or_swap_info(si, ci);
1468 static bool page_swapped(struct page *page)
1471 struct swap_info_struct *si;
1473 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
1474 return page_swapcount(page) != 0;
1476 page = compound_head(page);
1477 entry.val = page_private(page);
1478 si = _swap_info_get(entry);
1480 return swap_page_trans_huge_swapped(si, entry);
1484 static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
1485 int *total_swapcount)
1487 int i, map_swapcount, _total_mapcount, _total_swapcount;
1488 unsigned long offset = 0;
1489 struct swap_info_struct *si;
1490 struct swap_cluster_info *ci = NULL;
1491 unsigned char *map = NULL;
1492 int mapcount, swapcount = 0;
1494 /* hugetlbfs shouldn't call it */
1495 VM_BUG_ON_PAGE(PageHuge(page), page);
1497 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {
1498 mapcount = page_trans_huge_mapcount(page, total_mapcount);
1499 if (PageSwapCache(page))
1500 swapcount = page_swapcount(page);
1501 if (total_swapcount)
1502 *total_swapcount = swapcount;
1503 return mapcount + swapcount;
1506 page = compound_head(page);
1508 _total_mapcount = _total_swapcount = map_swapcount = 0;
1509 if (PageSwapCache(page)) {
1512 entry.val = page_private(page);
1513 si = _swap_info_get(entry);
1516 offset = swp_offset(entry);
1520 ci = lock_cluster(si, offset);
1521 for (i = 0; i < HPAGE_PMD_NR; i++) {
1522 mapcount = atomic_read(&page[i]._mapcount) + 1;
1523 _total_mapcount += mapcount;
1525 swapcount = swap_count(map[offset + i]);
1526 _total_swapcount += swapcount;
1528 map_swapcount = max(map_swapcount, mapcount + swapcount);
1531 if (PageDoubleMap(page)) {
1533 _total_mapcount -= HPAGE_PMD_NR;
1535 mapcount = compound_mapcount(page);
1536 map_swapcount += mapcount;
1537 _total_mapcount += mapcount;
1539 *total_mapcount = _total_mapcount;
1540 if (total_swapcount)
1541 *total_swapcount = _total_swapcount;
1543 return map_swapcount;
1547 * We can write to an anon page without COW if there are no other references
1548 * to it. And as a side-effect, free up its swap: because the old content
1549 * on disk will never be read, and seeking back there to write new content
1550 * later would only waste time away from clustering.
1552 * NOTE: total_map_swapcount should not be relied upon by the caller if
1553 * reuse_swap_page() returns false, but it may be always overwritten
1554 * (see the other implementation for CONFIG_SWAP=n).
1556 bool reuse_swap_page(struct page *page, int *total_map_swapcount)
1558 int count, total_mapcount, total_swapcount;
1560 VM_BUG_ON_PAGE(!PageLocked(page), page);
1561 if (unlikely(PageKsm(page)))
1563 count = page_trans_huge_map_swapcount(page, &total_mapcount,
1565 if (total_map_swapcount)
1566 *total_map_swapcount = total_mapcount + total_swapcount;
1567 if (count == 1 && PageSwapCache(page) &&
1568 (likely(!PageTransCompound(page)) ||
1569 /* The remaining swap count will be freed soon */
1570 total_swapcount == page_swapcount(page))) {
1571 if (!PageWriteback(page)) {
1572 page = compound_head(page);
1573 delete_from_swap_cache(page);
1577 struct swap_info_struct *p;
1579 entry.val = page_private(page);
1580 p = swap_info_get(entry);
1581 if (p->flags & SWP_STABLE_WRITES) {
1582 spin_unlock(&p->lock);
1585 spin_unlock(&p->lock);
1593 * If swap is getting full, or if there are no more mappings of this page,
1594 * then try_to_free_swap is called to free its swap space.
1596 int try_to_free_swap(struct page *page)
1598 VM_BUG_ON_PAGE(!PageLocked(page), page);
1600 if (!PageSwapCache(page))
1602 if (PageWriteback(page))
1604 if (page_swapped(page))
1608 * Once hibernation has begun to create its image of memory,
1609 * there's a danger that one of the calls to try_to_free_swap()
1610 * - most probably a call from __try_to_reclaim_swap() while
1611 * hibernation is allocating its own swap pages for the image,
1612 * but conceivably even a call from memory reclaim - will free
1613 * the swap from a page which has already been recorded in the
1614 * image as a clean swapcache page, and then reuse its swap for
1615 * another page of the image. On waking from hibernation, the
1616 * original page might be freed under memory pressure, then
1617 * later read back in from swap, now with the wrong data.
1619 * Hibernation suspends storage while it is writing the image
1620 * to disk so check that here.
1622 if (pm_suspended_storage())
1625 page = compound_head(page);
1626 delete_from_swap_cache(page);
1632 * Free the swap entry like above, but also try to
1633 * free the page cache entry if it is the last user.
1635 int free_swap_and_cache(swp_entry_t entry)
1637 struct swap_info_struct *p;
1638 unsigned char count;
1640 if (non_swap_entry(entry))
1643 p = _swap_info_get(entry);
1645 count = __swap_entry_free(p, entry, 1);
1646 if (count == SWAP_HAS_CACHE &&
1647 !swap_page_trans_huge_swapped(p, entry))
1648 __try_to_reclaim_swap(p, swp_offset(entry),
1649 TTRS_UNMAPPED | TTRS_FULL);
1654 #ifdef CONFIG_HIBERNATION
1656 * Find the swap type that corresponds to given device (if any).
1658 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1659 * from 0, in which the swap header is expected to be located.
1661 * This is needed for the suspend to disk (aka swsusp).
1663 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
1665 struct block_device *bdev = NULL;
1669 bdev = bdget(device);
1671 spin_lock(&swap_lock);
1672 for (type = 0; type < nr_swapfiles; type++) {
1673 struct swap_info_struct *sis = swap_info[type];
1675 if (!(sis->flags & SWP_WRITEOK))
1680 *bdev_p = bdgrab(sis->bdev);
1682 spin_unlock(&swap_lock);
1685 if (bdev == sis->bdev) {
1686 struct swap_extent *se = &sis->first_swap_extent;
1688 if (se->start_block == offset) {
1690 *bdev_p = bdgrab(sis->bdev);
1692 spin_unlock(&swap_lock);
1698 spin_unlock(&swap_lock);
1706 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1707 * corresponding to given index in swap_info (swap type).
1709 sector_t swapdev_block(int type, pgoff_t offset)
1711 struct block_device *bdev;
1712 struct swap_info_struct *si = swap_type_to_swap_info(type);
1714 if (!si || !(si->flags & SWP_WRITEOK))
1716 return map_swap_entry(swp_entry(type, offset), &bdev);
1720 * Return either the total number of swap pages of given type, or the number
1721 * of free pages of that type (depending on @free)
1723 * This is needed for software suspend
1725 unsigned int count_swap_pages(int type, int free)
1729 spin_lock(&swap_lock);
1730 if ((unsigned int)type < nr_swapfiles) {
1731 struct swap_info_struct *sis = swap_info[type];
1733 spin_lock(&sis->lock);
1734 if (sis->flags & SWP_WRITEOK) {
1737 n -= sis->inuse_pages;
1739 spin_unlock(&sis->lock);
1741 spin_unlock(&swap_lock);
1744 #endif /* CONFIG_HIBERNATION */
1746 static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1748 return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte);
1752 * No need to decide whether this PTE shares the swap entry with others,
1753 * just let do_wp_page work it out if a write is requested later - to
1754 * force COW, vm_page_prot omits write permission from any private vma.
1756 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1757 unsigned long addr, swp_entry_t entry, struct page *page)
1759 struct page *swapcache;
1760 struct mem_cgroup *memcg;
1766 page = ksm_might_need_to_copy(page, vma, addr);
1767 if (unlikely(!page))
1770 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL,
1776 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1777 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1778 mem_cgroup_cancel_charge(page, memcg, false);
1783 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1784 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1786 set_pte_at(vma->vm_mm, addr, pte,
1787 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1788 if (page == swapcache) {
1789 page_add_anon_rmap(page, vma, addr, false);
1790 mem_cgroup_commit_charge(page, memcg, true, false);
1791 } else { /* ksm created a completely new copy */
1792 page_add_new_anon_rmap(page, vma, addr, false);
1793 mem_cgroup_commit_charge(page, memcg, false, false);
1794 lru_cache_add_active_or_unevictable(page, vma);
1798 * Move the page to the active list so it is not
1799 * immediately swapped out again after swapon.
1801 activate_page(page);
1803 pte_unmap_unlock(pte, ptl);
1805 if (page != swapcache) {
1812 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1813 unsigned long addr, unsigned long end,
1814 unsigned int type, bool frontswap,
1815 unsigned long *fs_pages_to_unuse)
1820 struct swap_info_struct *si;
1821 unsigned long offset;
1823 volatile unsigned char *swap_map;
1825 si = swap_info[type];
1826 pte = pte_offset_map(pmd, addr);
1828 struct vm_fault vmf;
1830 if (!is_swap_pte(*pte))
1833 entry = pte_to_swp_entry(*pte);
1834 if (swp_type(entry) != type)
1837 offset = swp_offset(entry);
1838 if (frontswap && !frontswap_test(si, offset))
1842 swap_map = &si->swap_map[offset];
1846 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, &vmf);
1848 if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1854 wait_on_page_writeback(page);
1855 ret = unuse_pte(vma, pmd, addr, entry, page);
1862 try_to_free_swap(page);
1866 if (*fs_pages_to_unuse && !--(*fs_pages_to_unuse)) {
1867 ret = FRONTSWAP_PAGES_UNUSED;
1871 pte = pte_offset_map(pmd, addr);
1872 } while (pte++, addr += PAGE_SIZE, addr != end);
1880 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1881 unsigned long addr, unsigned long end,
1882 unsigned int type, bool frontswap,
1883 unsigned long *fs_pages_to_unuse)
1889 pmd = pmd_offset(pud, addr);
1892 next = pmd_addr_end(addr, end);
1893 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1895 ret = unuse_pte_range(vma, pmd, addr, next, type,
1896 frontswap, fs_pages_to_unuse);
1899 } while (pmd++, addr = next, addr != end);
1903 static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
1904 unsigned long addr, unsigned long end,
1905 unsigned int type, bool frontswap,
1906 unsigned long *fs_pages_to_unuse)
1912 pud = pud_offset(p4d, addr);
1914 next = pud_addr_end(addr, end);
1915 if (pud_none_or_clear_bad(pud))
1917 ret = unuse_pmd_range(vma, pud, addr, next, type,
1918 frontswap, fs_pages_to_unuse);
1921 } while (pud++, addr = next, addr != end);
1925 static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
1926 unsigned long addr, unsigned long end,
1927 unsigned int type, bool frontswap,
1928 unsigned long *fs_pages_to_unuse)
1934 p4d = p4d_offset(pgd, addr);
1936 next = p4d_addr_end(addr, end);
1937 if (p4d_none_or_clear_bad(p4d))
1939 ret = unuse_pud_range(vma, p4d, addr, next, type,
1940 frontswap, fs_pages_to_unuse);
1943 } while (p4d++, addr = next, addr != end);
1947 static int unuse_vma(struct vm_area_struct *vma, unsigned int type,
1948 bool frontswap, unsigned long *fs_pages_to_unuse)
1951 unsigned long addr, end, next;
1954 addr = vma->vm_start;
1957 pgd = pgd_offset(vma->vm_mm, addr);
1959 next = pgd_addr_end(addr, end);
1960 if (pgd_none_or_clear_bad(pgd))
1962 ret = unuse_p4d_range(vma, pgd, addr, next, type,
1963 frontswap, fs_pages_to_unuse);
1966 } while (pgd++, addr = next, addr != end);
1970 static int unuse_mm(struct mm_struct *mm, unsigned int type,
1971 bool frontswap, unsigned long *fs_pages_to_unuse)
1973 struct vm_area_struct *vma;
1976 down_read(&mm->mmap_sem);
1977 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1978 if (vma->anon_vma) {
1979 ret = unuse_vma(vma, type, frontswap,
1986 up_read(&mm->mmap_sem);
1991 * Scan swap_map (or frontswap_map if frontswap parameter is true)
1992 * from current position to next entry still in use. Return 0
1993 * if there are no inuse entries after prev till end of the map.
1995 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1996 unsigned int prev, bool frontswap)
1999 unsigned char count;
2002 * No need for swap_lock here: we're just looking
2003 * for whether an entry is in use, not modifying it; false
2004 * hits are okay, and sys_swapoff() has already prevented new
2005 * allocations from this area (while holding swap_lock).
2007 for (i = prev + 1; i < si->max; i++) {
2008 count = READ_ONCE(si->swap_map[i]);
2009 if (count && swap_count(count) != SWAP_MAP_BAD)
2010 if (!frontswap || frontswap_test(si, i))
2012 if ((i % LATENCY_LIMIT) == 0)
2023 * If the boolean frontswap is true, only unuse pages_to_unuse pages;
2024 * pages_to_unuse==0 means all pages; ignored if frontswap is false
2026 #define SWAP_UNUSE_MAX_TRIES 3
2027 int try_to_unuse(unsigned int type, bool frontswap,
2028 unsigned long pages_to_unuse)
2030 struct mm_struct *prev_mm;
2031 struct mm_struct *mm;
2032 struct list_head *p;
2034 struct swap_info_struct *si = swap_info[type];
2040 if (!si->inuse_pages)
2047 retval = shmem_unuse(type, frontswap, &pages_to_unuse);
2054 spin_lock(&mmlist_lock);
2055 p = &init_mm.mmlist;
2056 while ((p = p->next) != &init_mm.mmlist) {
2057 if (signal_pending(current)) {
2062 mm = list_entry(p, struct mm_struct, mmlist);
2063 if (!mmget_not_zero(mm))
2065 spin_unlock(&mmlist_lock);
2068 retval = unuse_mm(mm, type, frontswap, &pages_to_unuse);
2076 * Make sure that we aren't completely killing
2077 * interactive performance.
2080 spin_lock(&mmlist_lock);
2082 spin_unlock(&mmlist_lock);
2087 while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
2089 entry = swp_entry(type, i);
2090 page = find_get_page(swap_address_space(entry), i);
2095 * It is conceivable that a racing task removed this page from
2096 * swap cache just before we acquired the page lock. The page
2097 * might even be back in swap cache on another swap area. But
2098 * that is okay, try_to_free_swap() only removes stale pages.
2101 wait_on_page_writeback(page);
2102 try_to_free_swap(page);
2107 * For frontswap, we just need to unuse pages_to_unuse, if
2108 * it was specified. Need not check frontswap again here as
2109 * we already zeroed out pages_to_unuse if not frontswap.
2111 if (pages_to_unuse && --pages_to_unuse == 0)
2116 * Lets check again to see if there are still swap entries in the map.
2117 * If yes, we would need to do retry the unuse logic again.
2118 * Under global memory pressure, swap entries can be reinserted back
2119 * into process space after the mmlist loop above passes over them.
2120 * Its not worth continuosuly retrying to unuse the swap in this case.
2121 * So we try SWAP_UNUSE_MAX_TRIES times.
2123 if (++retries >= SWAP_UNUSE_MAX_TRIES)
2125 else if (si->inuse_pages)
2129 return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
2133 * After a successful try_to_unuse, if no swap is now in use, we know
2134 * we can empty the mmlist. swap_lock must be held on entry and exit.
2135 * Note that mmlist_lock nests inside swap_lock, and an mm must be
2136 * added to the mmlist just after page_duplicate - before would be racy.
2138 static void drain_mmlist(void)
2140 struct list_head *p, *next;
2143 for (type = 0; type < nr_swapfiles; type++)
2144 if (swap_info[type]->inuse_pages)
2146 spin_lock(&mmlist_lock);
2147 list_for_each_safe(p, next, &init_mm.mmlist)
2149 spin_unlock(&mmlist_lock);
2153 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
2154 * corresponds to page offset for the specified swap entry.
2155 * Note that the type of this function is sector_t, but it returns page offset
2156 * into the bdev, not sector offset.
2158 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
2160 struct swap_info_struct *sis;
2161 struct swap_extent *start_se;
2162 struct swap_extent *se;
2165 sis = swp_swap_info(entry);
2168 offset = swp_offset(entry);
2169 start_se = sis->curr_swap_extent;
2173 if (se->start_page <= offset &&
2174 offset < (se->start_page + se->nr_pages)) {
2175 return se->start_block + (offset - se->start_page);
2177 se = list_next_entry(se, list);
2178 sis->curr_swap_extent = se;
2179 BUG_ON(se == start_se); /* It *must* be present */
2184 * Returns the page offset into bdev for the specified page's swap entry.
2186 sector_t map_swap_page(struct page *page, struct block_device **bdev)
2189 entry.val = page_private(page);
2190 return map_swap_entry(entry, bdev);
2194 * Free all of a swapdev's extent information
2196 static void destroy_swap_extents(struct swap_info_struct *sis)
2198 while (!list_empty(&sis->first_swap_extent.list)) {
2199 struct swap_extent *se;
2201 se = list_first_entry(&sis->first_swap_extent.list,
2202 struct swap_extent, list);
2203 list_del(&se->list);
2207 if (sis->flags & SWP_ACTIVATED) {
2208 struct file *swap_file = sis->swap_file;
2209 struct address_space *mapping = swap_file->f_mapping;
2211 sis->flags &= ~SWP_ACTIVATED;
2212 if (mapping->a_ops->swap_deactivate)
2213 mapping->a_ops->swap_deactivate(swap_file);
2218 * Add a block range (and the corresponding page range) into this swapdev's
2219 * extent list. The extent list is kept sorted in page order.
2221 * This function rather assumes that it is called in ascending page order.
2224 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2225 unsigned long nr_pages, sector_t start_block)
2227 struct swap_extent *se;
2228 struct swap_extent *new_se;
2229 struct list_head *lh;
2231 if (start_page == 0) {
2232 se = &sis->first_swap_extent;
2233 sis->curr_swap_extent = se;
2235 se->nr_pages = nr_pages;
2236 se->start_block = start_block;
2239 lh = sis->first_swap_extent.list.prev; /* Highest extent */
2240 se = list_entry(lh, struct swap_extent, list);
2241 BUG_ON(se->start_page + se->nr_pages != start_page);
2242 if (se->start_block + se->nr_pages == start_block) {
2244 se->nr_pages += nr_pages;
2250 * No merge. Insert a new extent, preserving ordering.
2252 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2255 new_se->start_page = start_page;
2256 new_se->nr_pages = nr_pages;
2257 new_se->start_block = start_block;
2259 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
2262 EXPORT_SYMBOL_GPL(add_swap_extent);
2265 * A `swap extent' is a simple thing which maps a contiguous range of pages
2266 * onto a contiguous range of disk blocks. An ordered list of swap extents
2267 * is built at swapon time and is then used at swap_writepage/swap_readpage
2268 * time for locating where on disk a page belongs.
2270 * If the swapfile is an S_ISBLK block device, a single extent is installed.
2271 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2272 * swap files identically.
2274 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2275 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
2276 * swapfiles are handled *identically* after swapon time.
2278 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2279 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
2280 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
2281 * requirements, they are simply tossed out - we will never use those blocks
2284 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
2285 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
2286 * which will scribble on the fs.
2288 * The amount of disk space which a single swap extent represents varies.
2289 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
2290 * extents in the list. To avoid much list walking, we cache the previous
2291 * search location in `curr_swap_extent', and start new searches from there.
2292 * This is extremely effective. The average number of iterations in
2293 * map_swap_page() has been measured at about 0.3 per page. - akpm.
2295 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2297 struct file *swap_file = sis->swap_file;
2298 struct address_space *mapping = swap_file->f_mapping;
2299 struct inode *inode = mapping->host;
2302 if (S_ISBLK(inode->i_mode)) {
2303 ret = add_swap_extent(sis, 0, sis->max, 0);
2308 if (mapping->a_ops->swap_activate) {
2309 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2311 sis->flags |= SWP_ACTIVATED;
2313 sis->flags |= SWP_FS;
2314 ret = add_swap_extent(sis, 0, sis->max, 0);
2320 return generic_swapfile_activate(sis, swap_file, span);
2323 static int swap_node(struct swap_info_struct *p)
2325 struct block_device *bdev;
2330 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2332 return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2335 static void _enable_swap_info(struct swap_info_struct *p, int prio,
2336 unsigned char *swap_map,
2337 struct swap_cluster_info *cluster_info)
2344 p->prio = --least_priority;
2346 * the plist prio is negated because plist ordering is
2347 * low-to-high, while swap ordering is high-to-low
2349 p->list.prio = -p->prio;
2352 p->avail_lists[i].prio = -p->prio;
2354 if (swap_node(p) == i)
2355 p->avail_lists[i].prio = 1;
2357 p->avail_lists[i].prio = -p->prio;
2360 p->swap_map = swap_map;
2361 p->cluster_info = cluster_info;
2362 p->flags |= SWP_WRITEOK;
2363 atomic_long_add(p->pages, &nr_swap_pages);
2364 total_swap_pages += p->pages;
2366 assert_spin_locked(&swap_lock);
2368 * both lists are plists, and thus priority ordered.
2369 * swap_active_head needs to be priority ordered for swapoff(),
2370 * which on removal of any swap_info_struct with an auto-assigned
2371 * (i.e. negative) priority increments the auto-assigned priority
2372 * of any lower-priority swap_info_structs.
2373 * swap_avail_head needs to be priority ordered for get_swap_page(),
2374 * which allocates swap pages from the highest available priority
2377 plist_add(&p->list, &swap_active_head);
2378 add_to_avail_list(p);
2381 static void enable_swap_info(struct swap_info_struct *p, int prio,
2382 unsigned char *swap_map,
2383 struct swap_cluster_info *cluster_info,
2384 unsigned long *frontswap_map)
2386 frontswap_init(p->type, frontswap_map);
2387 spin_lock(&swap_lock);
2388 spin_lock(&p->lock);
2389 _enable_swap_info(p, prio, swap_map, cluster_info);
2390 spin_unlock(&p->lock);
2391 spin_unlock(&swap_lock);
2394 static void reinsert_swap_info(struct swap_info_struct *p)
2396 spin_lock(&swap_lock);
2397 spin_lock(&p->lock);
2398 _enable_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2399 spin_unlock(&p->lock);
2400 spin_unlock(&swap_lock);
2403 bool has_usable_swap(void)
2407 spin_lock(&swap_lock);
2408 if (plist_head_empty(&swap_active_head))
2410 spin_unlock(&swap_lock);
2414 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2416 struct swap_info_struct *p = NULL;
2417 unsigned char *swap_map;
2418 struct swap_cluster_info *cluster_info;
2419 unsigned long *frontswap_map;
2420 struct file *swap_file, *victim;
2421 struct address_space *mapping;
2422 struct inode *inode;
2423 struct filename *pathname;
2425 unsigned int old_block_size;
2427 if (!capable(CAP_SYS_ADMIN))
2430 BUG_ON(!current->mm);
2432 pathname = getname(specialfile);
2433 if (IS_ERR(pathname))
2434 return PTR_ERR(pathname);
2436 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2437 err = PTR_ERR(victim);
2441 mapping = victim->f_mapping;
2442 spin_lock(&swap_lock);
2443 plist_for_each_entry(p, &swap_active_head, list) {
2444 if (p->flags & SWP_WRITEOK) {
2445 if (p->swap_file->f_mapping == mapping) {
2453 spin_unlock(&swap_lock);
2456 if (!security_vm_enough_memory_mm(current->mm, p->pages))
2457 vm_unacct_memory(p->pages);
2460 spin_unlock(&swap_lock);
2463 del_from_avail_list(p);
2464 spin_lock(&p->lock);
2466 struct swap_info_struct *si = p;
2469 plist_for_each_entry_continue(si, &swap_active_head, list) {
2472 for_each_node(nid) {
2473 if (si->avail_lists[nid].prio != 1)
2474 si->avail_lists[nid].prio--;
2479 plist_del(&p->list, &swap_active_head);
2480 atomic_long_sub(p->pages, &nr_swap_pages);
2481 total_swap_pages -= p->pages;
2482 p->flags &= ~SWP_WRITEOK;
2483 spin_unlock(&p->lock);
2484 spin_unlock(&swap_lock);
2486 disable_swap_slots_cache_lock();
2488 set_current_oom_origin();
2489 err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
2490 clear_current_oom_origin();
2493 /* re-insert swap space back into swap_list */
2494 reinsert_swap_info(p);
2495 reenable_swap_slots_cache_unlock();
2499 reenable_swap_slots_cache_unlock();
2501 flush_work(&p->discard_work);
2503 destroy_swap_extents(p);
2504 if (p->flags & SWP_CONTINUED)
2505 free_swap_count_continuations(p);
2507 if (!p->bdev || !blk_queue_nonrot(bdev_get_queue(p->bdev)))
2508 atomic_dec(&nr_rotate_swap);
2510 mutex_lock(&swapon_mutex);
2511 spin_lock(&swap_lock);
2512 spin_lock(&p->lock);
2515 /* wait for anyone still in scan_swap_map */
2516 p->highest_bit = 0; /* cuts scans short */
2517 while (p->flags >= SWP_SCANNING) {
2518 spin_unlock(&p->lock);
2519 spin_unlock(&swap_lock);
2520 schedule_timeout_uninterruptible(1);
2521 spin_lock(&swap_lock);
2522 spin_lock(&p->lock);
2525 swap_file = p->swap_file;
2526 old_block_size = p->old_block_size;
2527 p->swap_file = NULL;
2529 swap_map = p->swap_map;
2531 cluster_info = p->cluster_info;
2532 p->cluster_info = NULL;
2533 frontswap_map = frontswap_map_get(p);
2534 spin_unlock(&p->lock);
2535 spin_unlock(&swap_lock);
2536 frontswap_invalidate_area(p->type);
2537 frontswap_map_set(p, NULL);
2538 mutex_unlock(&swapon_mutex);
2539 free_percpu(p->percpu_cluster);
2540 p->percpu_cluster = NULL;
2542 kvfree(cluster_info);
2543 kvfree(frontswap_map);
2544 /* Destroy swap account information */
2545 swap_cgroup_swapoff(p->type);
2546 exit_swap_address_space(p->type);
2548 inode = mapping->host;
2549 if (S_ISBLK(inode->i_mode)) {
2550 struct block_device *bdev = I_BDEV(inode);
2551 set_blocksize(bdev, old_block_size);
2552 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2555 inode->i_flags &= ~S_SWAPFILE;
2556 inode_unlock(inode);
2558 filp_close(swap_file, NULL);
2561 * Clear the SWP_USED flag after all resources are freed so that swapon
2562 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
2563 * not hold p->lock after we cleared its SWP_WRITEOK.
2565 spin_lock(&swap_lock);
2567 spin_unlock(&swap_lock);
2570 atomic_inc(&proc_poll_event);
2571 wake_up_interruptible(&proc_poll_wait);
2574 filp_close(victim, NULL);
2580 #ifdef CONFIG_PROC_FS
2581 static __poll_t swaps_poll(struct file *file, poll_table *wait)
2583 struct seq_file *seq = file->private_data;
2585 poll_wait(file, &proc_poll_wait, wait);
2587 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2588 seq->poll_event = atomic_read(&proc_poll_event);
2589 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2592 return EPOLLIN | EPOLLRDNORM;
2596 static void *swap_start(struct seq_file *swap, loff_t *pos)
2598 struct swap_info_struct *si;
2602 mutex_lock(&swapon_mutex);
2605 return SEQ_START_TOKEN;
2607 for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2608 if (!(si->flags & SWP_USED) || !si->swap_map)
2617 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2619 struct swap_info_struct *si = v;
2622 if (v == SEQ_START_TOKEN)
2625 type = si->type + 1;
2627 for (; (si = swap_type_to_swap_info(type)); type++) {
2628 if (!(si->flags & SWP_USED) || !si->swap_map)
2637 static void swap_stop(struct seq_file *swap, void *v)
2639 mutex_unlock(&swapon_mutex);
2642 static int swap_show(struct seq_file *swap, void *v)
2644 struct swap_info_struct *si = v;
2648 if (si == SEQ_START_TOKEN) {
2649 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
2653 file = si->swap_file;
2654 len = seq_file_path(swap, file, " \t\n\\");
2655 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
2656 len < 40 ? 40 - len : 1, " ",
2657 S_ISBLK(file_inode(file)->i_mode) ?
2658 "partition" : "file\t",
2659 si->pages << (PAGE_SHIFT - 10),
2660 si->inuse_pages << (PAGE_SHIFT - 10),
2665 static const struct seq_operations swaps_op = {
2666 .start = swap_start,
2672 static int swaps_open(struct inode *inode, struct file *file)
2674 struct seq_file *seq;
2677 ret = seq_open(file, &swaps_op);
2681 seq = file->private_data;
2682 seq->poll_event = atomic_read(&proc_poll_event);
2686 static const struct file_operations proc_swaps_operations = {
2689 .llseek = seq_lseek,
2690 .release = seq_release,
2694 static int __init procswaps_init(void)
2696 proc_create("swaps", 0, NULL, &proc_swaps_operations);
2699 __initcall(procswaps_init);
2700 #endif /* CONFIG_PROC_FS */
2702 #ifdef MAX_SWAPFILES_CHECK
2703 static int __init max_swapfiles_check(void)
2705 MAX_SWAPFILES_CHECK();
2708 late_initcall(max_swapfiles_check);
2711 static struct swap_info_struct *alloc_swap_info(void)
2713 struct swap_info_struct *p;
2717 p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2719 return ERR_PTR(-ENOMEM);
2721 spin_lock(&swap_lock);
2722 for (type = 0; type < nr_swapfiles; type++) {
2723 if (!(swap_info[type]->flags & SWP_USED))
2726 if (type >= MAX_SWAPFILES) {
2727 spin_unlock(&swap_lock);
2729 return ERR_PTR(-EPERM);
2731 if (type >= nr_swapfiles) {
2733 WRITE_ONCE(swap_info[type], p);
2735 * Write swap_info[type] before nr_swapfiles, in case a
2736 * racing procfs swap_start() or swap_next() is reading them.
2737 * (We never shrink nr_swapfiles, we never free this entry.)
2740 WRITE_ONCE(nr_swapfiles, nr_swapfiles + 1);
2743 p = swap_info[type];
2745 * Do not memset this entry: a racing procfs swap_next()
2746 * would be relying on p->type to remain valid.
2749 INIT_LIST_HEAD(&p->first_swap_extent.list);
2750 plist_node_init(&p->list, 0);
2752 plist_node_init(&p->avail_lists[i], 0);
2753 p->flags = SWP_USED;
2754 spin_unlock(&swap_lock);
2755 spin_lock_init(&p->lock);
2756 spin_lock_init(&p->cont_lock);
2761 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2765 if (S_ISBLK(inode->i_mode)) {
2766 p->bdev = bdgrab(I_BDEV(inode));
2767 error = blkdev_get(p->bdev,
2768 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2773 p->old_block_size = block_size(p->bdev);
2774 error = set_blocksize(p->bdev, PAGE_SIZE);
2777 p->flags |= SWP_BLKDEV;
2778 } else if (S_ISREG(inode->i_mode)) {
2779 p->bdev = inode->i_sb->s_bdev;
2781 if (IS_SWAPFILE(inode))
2791 * Find out how many pages are allowed for a single swap device. There
2792 * are two limiting factors:
2793 * 1) the number of bits for the swap offset in the swp_entry_t type, and
2794 * 2) the number of bits in the swap pte, as defined by the different
2797 * In order to find the largest possible bit mask, a swap entry with
2798 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2799 * decoded to a swp_entry_t again, and finally the swap offset is
2802 * This will mask all the bits from the initial ~0UL mask that can't
2803 * be encoded in either the swp_entry_t or the architecture definition
2806 unsigned long generic_max_swapfile_size(void)
2808 return swp_offset(pte_to_swp_entry(
2809 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2812 /* Can be overridden by an architecture for additional checks. */
2813 __weak unsigned long max_swapfile_size(void)
2815 return generic_max_swapfile_size();
2818 static unsigned long read_swap_header(struct swap_info_struct *p,
2819 union swap_header *swap_header,
2820 struct inode *inode)
2823 unsigned long maxpages;
2824 unsigned long swapfilepages;
2825 unsigned long last_page;
2827 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2828 pr_err("Unable to find swap-space signature\n");
2832 /* swap partition endianess hack... */
2833 if (swab32(swap_header->info.version) == 1) {
2834 swab32s(&swap_header->info.version);
2835 swab32s(&swap_header->info.last_page);
2836 swab32s(&swap_header->info.nr_badpages);
2837 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2839 for (i = 0; i < swap_header->info.nr_badpages; i++)
2840 swab32s(&swap_header->info.badpages[i]);
2842 /* Check the swap header's sub-version */
2843 if (swap_header->info.version != 1) {
2844 pr_warn("Unable to handle swap header version %d\n",
2845 swap_header->info.version);
2850 p->cluster_next = 1;
2853 maxpages = max_swapfile_size();
2854 last_page = swap_header->info.last_page;
2856 pr_warn("Empty swap-file\n");
2859 if (last_page > maxpages) {
2860 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2861 maxpages << (PAGE_SHIFT - 10),
2862 last_page << (PAGE_SHIFT - 10));
2864 if (maxpages > last_page) {
2865 maxpages = last_page + 1;
2866 /* p->max is an unsigned int: don't overflow it */
2867 if ((unsigned int)maxpages == 0)
2868 maxpages = UINT_MAX;
2870 p->highest_bit = maxpages - 1;
2874 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2875 if (swapfilepages && maxpages > swapfilepages) {
2876 pr_warn("Swap area shorter than signature indicates\n");
2879 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2881 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2887 #define SWAP_CLUSTER_INFO_COLS \
2888 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
2889 #define SWAP_CLUSTER_SPACE_COLS \
2890 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
2891 #define SWAP_CLUSTER_COLS \
2892 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
2894 static int setup_swap_map_and_extents(struct swap_info_struct *p,
2895 union swap_header *swap_header,
2896 unsigned char *swap_map,
2897 struct swap_cluster_info *cluster_info,
2898 unsigned long maxpages,
2902 unsigned int nr_good_pages;
2904 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2905 unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
2906 unsigned long i, idx;
2908 nr_good_pages = maxpages - 1; /* omit header page */
2910 cluster_list_init(&p->free_clusters);
2911 cluster_list_init(&p->discard_clusters);
2913 for (i = 0; i < swap_header->info.nr_badpages; i++) {
2914 unsigned int page_nr = swap_header->info.badpages[i];
2915 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2917 if (page_nr < maxpages) {
2918 swap_map[page_nr] = SWAP_MAP_BAD;
2921 * Haven't marked the cluster free yet, no list
2922 * operation involved
2924 inc_cluster_info_page(p, cluster_info, page_nr);
2928 /* Haven't marked the cluster free yet, no list operation involved */
2929 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2930 inc_cluster_info_page(p, cluster_info, i);
2932 if (nr_good_pages) {
2933 swap_map[0] = SWAP_MAP_BAD;
2935 * Not mark the cluster free yet, no list
2936 * operation involved
2938 inc_cluster_info_page(p, cluster_info, 0);
2940 p->pages = nr_good_pages;
2941 nr_extents = setup_swap_extents(p, span);
2944 nr_good_pages = p->pages;
2946 if (!nr_good_pages) {
2947 pr_warn("Empty swap-file\n");
2956 * Reduce false cache line sharing between cluster_info and
2957 * sharing same address space.
2959 for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
2960 j = (k + col) % SWAP_CLUSTER_COLS;
2961 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
2962 idx = i * SWAP_CLUSTER_COLS + j;
2963 if (idx >= nr_clusters)
2965 if (cluster_count(&cluster_info[idx]))
2967 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2968 cluster_list_add_tail(&p->free_clusters, cluster_info,
2976 * Helper to sys_swapon determining if a given swap
2977 * backing device queue supports DISCARD operations.
2979 static bool swap_discardable(struct swap_info_struct *si)
2981 struct request_queue *q = bdev_get_queue(si->bdev);
2983 if (!q || !blk_queue_discard(q))
2989 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2991 struct swap_info_struct *p;
2992 struct filename *name;
2993 struct file *swap_file = NULL;
2994 struct address_space *mapping;
2997 union swap_header *swap_header;
3000 unsigned long maxpages;
3001 unsigned char *swap_map = NULL;
3002 struct swap_cluster_info *cluster_info = NULL;
3003 unsigned long *frontswap_map = NULL;
3004 struct page *page = NULL;
3005 struct inode *inode = NULL;
3006 bool inced_nr_rotate_swap = false;
3008 if (swap_flags & ~SWAP_FLAGS_VALID)
3011 if (!capable(CAP_SYS_ADMIN))
3014 if (!swap_avail_heads)
3017 p = alloc_swap_info();
3021 INIT_WORK(&p->discard_work, swap_discard_work);
3023 name = getname(specialfile);
3025 error = PTR_ERR(name);
3029 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3030 if (IS_ERR(swap_file)) {
3031 error = PTR_ERR(swap_file);
3036 p->swap_file = swap_file;
3037 mapping = swap_file->f_mapping;
3038 inode = mapping->host;
3040 /* If S_ISREG(inode->i_mode) will do inode_lock(inode); */
3041 error = claim_swapfile(p, inode);
3042 if (unlikely(error))
3046 * Read the swap header.
3048 if (!mapping->a_ops->readpage) {
3052 page = read_mapping_page(mapping, 0, swap_file);
3054 error = PTR_ERR(page);
3057 swap_header = kmap(page);
3059 maxpages = read_swap_header(p, swap_header, inode);
3060 if (unlikely(!maxpages)) {
3065 /* OK, set up the swap map and apply the bad block list */
3066 swap_map = vzalloc(maxpages);
3072 if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))
3073 p->flags |= SWP_STABLE_WRITES;
3075 if (bdi_cap_synchronous_io(inode_to_bdi(inode)))
3076 p->flags |= SWP_SYNCHRONOUS_IO;
3078 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
3080 unsigned long ci, nr_cluster;
3082 p->flags |= SWP_SOLIDSTATE;
3084 * select a random position to start with to help wear leveling
3087 p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
3088 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3090 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3092 if (!cluster_info) {
3097 for (ci = 0; ci < nr_cluster; ci++)
3098 spin_lock_init(&((cluster_info + ci)->lock));
3100 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3101 if (!p->percpu_cluster) {
3105 for_each_possible_cpu(cpu) {
3106 struct percpu_cluster *cluster;
3107 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3108 cluster_set_null(&cluster->index);
3111 atomic_inc(&nr_rotate_swap);
3112 inced_nr_rotate_swap = true;
3115 error = swap_cgroup_swapon(p->type, maxpages);
3119 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3120 cluster_info, maxpages, &span);
3121 if (unlikely(nr_extents < 0)) {
3125 /* frontswap enabled? set up bit-per-page map for frontswap */
3126 if (IS_ENABLED(CONFIG_FRONTSWAP))
3127 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3131 if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
3133 * When discard is enabled for swap with no particular
3134 * policy flagged, we set all swap discard flags here in
3135 * order to sustain backward compatibility with older
3136 * swapon(8) releases.
3138 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3142 * By flagging sys_swapon, a sysadmin can tell us to
3143 * either do single-time area discards only, or to just
3144 * perform discards for released swap page-clusters.
3145 * Now it's time to adjust the p->flags accordingly.
3147 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3148 p->flags &= ~SWP_PAGE_DISCARD;
3149 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3150 p->flags &= ~SWP_AREA_DISCARD;
3152 /* issue a swapon-time discard if it's still required */
3153 if (p->flags & SWP_AREA_DISCARD) {
3154 int err = discard_swap(p);
3156 pr_err("swapon: discard_swap(%p): %d\n",
3161 error = init_swap_address_space(p->type, maxpages);
3165 mutex_lock(&swapon_mutex);
3167 if (swap_flags & SWAP_FLAG_PREFER)
3169 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3170 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3172 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3173 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3174 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3175 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3176 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3177 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3178 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3179 (frontswap_map) ? "FS" : "");
3181 mutex_unlock(&swapon_mutex);
3182 atomic_inc(&proc_poll_event);
3183 wake_up_interruptible(&proc_poll_wait);
3185 if (S_ISREG(inode->i_mode))
3186 inode->i_flags |= S_SWAPFILE;
3190 free_percpu(p->percpu_cluster);
3191 p->percpu_cluster = NULL;
3192 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3193 set_blocksize(p->bdev, p->old_block_size);
3194 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3196 destroy_swap_extents(p);
3197 swap_cgroup_swapoff(p->type);
3198 spin_lock(&swap_lock);
3199 p->swap_file = NULL;
3201 spin_unlock(&swap_lock);
3203 kvfree(cluster_info);
3204 kvfree(frontswap_map);
3205 if (inced_nr_rotate_swap)
3206 atomic_dec(&nr_rotate_swap);
3208 if (inode && S_ISREG(inode->i_mode)) {
3209 inode_unlock(inode);
3212 filp_close(swap_file, NULL);
3215 if (page && !IS_ERR(page)) {
3221 if (inode && S_ISREG(inode->i_mode))
3222 inode_unlock(inode);
3224 enable_swap_slots_cache();
3228 void si_swapinfo(struct sysinfo *val)
3231 unsigned long nr_to_be_unused = 0;
3233 spin_lock(&swap_lock);
3234 for (type = 0; type < nr_swapfiles; type++) {
3235 struct swap_info_struct *si = swap_info[type];
3237 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3238 nr_to_be_unused += si->inuse_pages;
3240 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3241 val->totalswap = total_swap_pages + nr_to_be_unused;
3242 spin_unlock(&swap_lock);
3246 * Verify that a swap entry is valid and increment its swap map count.
3248 * Returns error code in following case.
3250 * - swp_entry is invalid -> EINVAL
3251 * - swp_entry is migration entry -> EINVAL
3252 * - swap-cache reference is requested but there is already one. -> EEXIST
3253 * - swap-cache reference is requested but the entry is not used. -> ENOENT
3254 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3256 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3258 struct swap_info_struct *p;
3259 struct swap_cluster_info *ci;
3260 unsigned long offset;
3261 unsigned char count;
3262 unsigned char has_cache;
3265 if (non_swap_entry(entry))
3268 p = swp_swap_info(entry);
3272 offset = swp_offset(entry);
3273 if (unlikely(offset >= p->max))
3276 ci = lock_cluster_or_swap_info(p, offset);
3278 count = p->swap_map[offset];
3281 * swapin_readahead() doesn't check if a swap entry is valid, so the
3282 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3284 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3289 has_cache = count & SWAP_HAS_CACHE;
3290 count &= ~SWAP_HAS_CACHE;
3293 if (usage == SWAP_HAS_CACHE) {
3295 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3296 if (!has_cache && count)
3297 has_cache = SWAP_HAS_CACHE;
3298 else if (has_cache) /* someone else added cache */
3300 else /* no users remaining */
3303 } else if (count || has_cache) {
3305 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3307 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3309 else if (swap_count_continued(p, offset, count))
3310 count = COUNT_CONTINUED;
3314 err = -ENOENT; /* unused swap entry */
3316 p->swap_map[offset] = count | has_cache;
3319 unlock_cluster_or_swap_info(p, ci);
3324 pr_err("swap_dup: %s%08lx\n", Bad_file, entry.val);
3329 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3330 * (in which case its reference count is never incremented).
3332 void swap_shmem_alloc(swp_entry_t entry)
3334 __swap_duplicate(entry, SWAP_MAP_SHMEM);
3338 * Increase reference count of swap entry by 1.
3339 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3340 * but could not be atomically allocated. Returns 0, just as if it succeeded,
3341 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3342 * might occur if a page table entry has got corrupted.
3344 int swap_duplicate(swp_entry_t entry)
3348 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3349 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3354 * @entry: swap entry for which we allocate swap cache.
3356 * Called when allocating swap cache for existing swap entry,
3357 * This can return error codes. Returns 0 at success.
3358 * -EBUSY means there is a swap cache.
3359 * Note: return code is different from swap_duplicate().
3361 int swapcache_prepare(swp_entry_t entry)
3363 return __swap_duplicate(entry, SWAP_HAS_CACHE);
3366 struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3368 return swap_type_to_swap_info(swp_type(entry));
3371 struct swap_info_struct *page_swap_info(struct page *page)
3373 swp_entry_t entry = { .val = page_private(page) };
3374 return swp_swap_info(entry);
3378 * out-of-line __page_file_ methods to avoid include hell.
3380 struct address_space *__page_file_mapping(struct page *page)
3382 return page_swap_info(page)->swap_file->f_mapping;
3384 EXPORT_SYMBOL_GPL(__page_file_mapping);
3386 pgoff_t __page_file_index(struct page *page)
3388 swp_entry_t swap = { .val = page_private(page) };
3389 return swp_offset(swap);
3391 EXPORT_SYMBOL_GPL(__page_file_index);
3394 * add_swap_count_continuation - called when a swap count is duplicated
3395 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3396 * page of the original vmalloc'ed swap_map, to hold the continuation count
3397 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
3398 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3400 * These continuation pages are seldom referenced: the common paths all work
3401 * on the original swap_map, only referring to a continuation page when the
3402 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3404 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3405 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3406 * can be called after dropping locks.
3408 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3410 struct swap_info_struct *si;
3411 struct swap_cluster_info *ci;
3414 struct page *list_page;
3416 unsigned char count;
3419 * When debugging, it's easier to use __GFP_ZERO here; but it's better
3420 * for latency not to zero a page while GFP_ATOMIC and holding locks.
3422 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3424 si = swap_info_get(entry);
3427 * An acceptable race has occurred since the failing
3428 * __swap_duplicate(): the swap entry has been freed,
3429 * perhaps even the whole swap_map cleared for swapoff.
3434 offset = swp_offset(entry);
3436 ci = lock_cluster(si, offset);
3438 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
3440 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3442 * The higher the swap count, the more likely it is that tasks
3443 * will race to add swap count continuation: we need to avoid
3444 * over-provisioning.
3451 spin_unlock(&si->lock);
3456 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3457 * no architecture is using highmem pages for kernel page tables: so it
3458 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3460 head = vmalloc_to_page(si->swap_map + offset);
3461 offset &= ~PAGE_MASK;
3463 spin_lock(&si->cont_lock);
3465 * Page allocation does not initialize the page's lru field,
3466 * but it does always reset its private field.
3468 if (!page_private(head)) {
3469 BUG_ON(count & COUNT_CONTINUED);
3470 INIT_LIST_HEAD(&head->lru);
3471 set_page_private(head, SWP_CONTINUED);
3472 si->flags |= SWP_CONTINUED;
3475 list_for_each_entry(list_page, &head->lru, lru) {
3479 * If the previous map said no continuation, but we've found
3480 * a continuation page, free our allocation and use this one.
3482 if (!(count & COUNT_CONTINUED))
3483 goto out_unlock_cont;
3485 map = kmap_atomic(list_page) + offset;
3490 * If this continuation count now has some space in it,
3491 * free our allocation and use this one.
3493 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3494 goto out_unlock_cont;
3497 list_add_tail(&page->lru, &head->lru);
3498 page = NULL; /* now it's attached, don't free it */
3500 spin_unlock(&si->cont_lock);
3503 spin_unlock(&si->lock);
3511 * swap_count_continued - when the original swap_map count is incremented
3512 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3513 * into, carry if so, or else fail until a new continuation page is allocated;
3514 * when the original swap_map count is decremented from 0 with continuation,
3515 * borrow from the continuation and report whether it still holds more.
3516 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3519 static bool swap_count_continued(struct swap_info_struct *si,
3520 pgoff_t offset, unsigned char count)
3527 head = vmalloc_to_page(si->swap_map + offset);
3528 if (page_private(head) != SWP_CONTINUED) {
3529 BUG_ON(count & COUNT_CONTINUED);
3530 return false; /* need to add count continuation */
3533 spin_lock(&si->cont_lock);
3534 offset &= ~PAGE_MASK;
3535 page = list_entry(head->lru.next, struct page, lru);
3536 map = kmap_atomic(page) + offset;
3538 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
3539 goto init_map; /* jump over SWAP_CONT_MAX checks */
3541 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3543 * Think of how you add 1 to 999
3545 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3547 page = list_entry(page->lru.next, struct page, lru);
3548 BUG_ON(page == head);
3549 map = kmap_atomic(page) + offset;
3551 if (*map == SWAP_CONT_MAX) {
3553 page = list_entry(page->lru.next, struct page, lru);
3555 ret = false; /* add count continuation */
3558 map = kmap_atomic(page) + offset;
3559 init_map: *map = 0; /* we didn't zero the page */
3563 page = list_entry(page->lru.prev, struct page, lru);
3564 while (page != head) {
3565 map = kmap_atomic(page) + offset;
3566 *map = COUNT_CONTINUED;
3568 page = list_entry(page->lru.prev, struct page, lru);
3570 ret = true; /* incremented */
3572 } else { /* decrementing */
3574 * Think of how you subtract 1 from 1000
3576 BUG_ON(count != COUNT_CONTINUED);
3577 while (*map == COUNT_CONTINUED) {
3579 page = list_entry(page->lru.next, struct page, lru);
3580 BUG_ON(page == head);
3581 map = kmap_atomic(page) + offset;
3588 page = list_entry(page->lru.prev, struct page, lru);
3589 while (page != head) {
3590 map = kmap_atomic(page) + offset;
3591 *map = SWAP_CONT_MAX | count;
3592 count = COUNT_CONTINUED;
3594 page = list_entry(page->lru.prev, struct page, lru);
3596 ret = count == COUNT_CONTINUED;
3599 spin_unlock(&si->cont_lock);
3604 * free_swap_count_continuations - swapoff free all the continuation pages
3605 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3607 static void free_swap_count_continuations(struct swap_info_struct *si)
3611 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3613 head = vmalloc_to_page(si->swap_map + offset);
3614 if (page_private(head)) {
3615 struct page *page, *next;
3617 list_for_each_entry_safe(page, next, &head->lru, lru) {
3618 list_del(&page->lru);
3625 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3626 void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg, int node,
3629 struct swap_info_struct *si, *next;
3630 if (!(gfp_mask & __GFP_IO) || !memcg)
3633 if (!blk_cgroup_congested())
3637 * We've already scheduled a throttle, avoid taking the global swap
3640 if (current->throttle_queue)
3643 spin_lock(&swap_avail_lock);
3644 plist_for_each_entry_safe(si, next, &swap_avail_heads[node],
3645 avail_lists[node]) {
3647 blkcg_schedule_throttle(bdev_get_queue(si->bdev),
3652 spin_unlock(&swap_avail_lock);
3656 static int __init swapfile_init(void)
3660 swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3662 if (!swap_avail_heads) {
3663 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3668 plist_head_init(&swap_avail_heads[nid]);
3672 subsys_initcall(swapfile_init);