1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie
9 #include <linux/blkdev.h>
11 #include <linux/sched/mm.h>
12 #include <linux/sched/task.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mman.h>
15 #include <linux/slab.h>
16 #include <linux/kernel_stat.h>
17 #include <linux/swap.h>
18 #include <linux/vmalloc.h>
19 #include <linux/pagemap.h>
20 #include <linux/namei.h>
21 #include <linux/shmem_fs.h>
22 #include <linux/blk-cgroup.h>
23 #include <linux/random.h>
24 #include <linux/writeback.h>
25 #include <linux/proc_fs.h>
26 #include <linux/seq_file.h>
27 #include <linux/init.h>
28 #include <linux/ksm.h>
29 #include <linux/rmap.h>
30 #include <linux/security.h>
31 #include <linux/backing-dev.h>
32 #include <linux/mutex.h>
33 #include <linux/capability.h>
34 #include <linux/syscalls.h>
35 #include <linux/memcontrol.h>
36 #include <linux/poll.h>
37 #include <linux/oom.h>
38 #include <linux/swapfile.h>
39 #include <linux/export.h>
40 #include <linux/swap_slots.h>
41 #include <linux/sort.h>
42 #include <linux/completion.h>
43 #include <linux/suspend.h>
44 #include <linux/zswap.h>
46 #include <asm/tlbflush.h>
47 #include <linux/swapops.h>
48 #include <linux/swap_cgroup.h>
52 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
54 static void free_swap_count_continuations(struct swap_info_struct *);
56 static DEFINE_SPINLOCK(swap_lock);
57 static unsigned int nr_swapfiles;
58 atomic_long_t nr_swap_pages;
60 * Some modules use swappable objects and may try to swap them out under
61 * memory pressure (via the shrinker). Before doing so, they may wish to
62 * check to see if any swap space is available.
64 EXPORT_SYMBOL_GPL(nr_swap_pages);
65 /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
66 long total_swap_pages;
67 static int least_priority = -1;
68 unsigned long swapfile_maximum_size;
69 #ifdef CONFIG_MIGRATION
70 bool swap_migration_ad_supported;
71 #endif /* CONFIG_MIGRATION */
73 static const char Bad_file[] = "Bad swap file entry ";
74 static const char Unused_file[] = "Unused swap file entry ";
75 static const char Bad_offset[] = "Bad swap offset entry ";
76 static const char Unused_offset[] = "Unused swap offset entry ";
79 * all active swap_info_structs
80 * protected with swap_lock, and ordered by priority.
82 static PLIST_HEAD(swap_active_head);
85 * all available (active, not full) swap_info_structs
86 * protected with swap_avail_lock, ordered by priority.
87 * This is used by folio_alloc_swap() instead of swap_active_head
88 * because swap_active_head includes all swap_info_structs,
89 * but folio_alloc_swap() doesn't need to look at full ones.
90 * This uses its own lock instead of swap_lock because when a
91 * swap_info_struct changes between not-full/full, it needs to
92 * add/remove itself to/from this list, but the swap_info_struct->lock
93 * is held and the locking order requires swap_lock to be taken
94 * before any swap_info_struct->lock.
96 static struct plist_head *swap_avail_heads;
97 static DEFINE_SPINLOCK(swap_avail_lock);
99 static struct swap_info_struct *swap_info[MAX_SWAPFILES];
101 static DEFINE_MUTEX(swapon_mutex);
103 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
104 /* Activity counter to indicate that a swapon or swapoff has occurred */
105 static atomic_t proc_poll_event = ATOMIC_INIT(0);
107 atomic_t nr_rotate_swap = ATOMIC_INIT(0);
109 static struct swap_info_struct *swap_type_to_swap_info(int type)
111 if (type >= MAX_SWAPFILES)
114 return READ_ONCE(swap_info[type]); /* rcu_dereference() */
117 static inline unsigned char swap_count(unsigned char ent)
119 return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
122 /* Reclaim the swap entry anyway if possible */
123 #define TTRS_ANYWAY 0x1
125 * Reclaim the swap entry if there are no more mappings of the
128 #define TTRS_UNMAPPED 0x2
129 /* Reclaim the swap entry if swap is getting full*/
130 #define TTRS_FULL 0x4
132 /* returns 1 if swap entry is freed */
133 static int __try_to_reclaim_swap(struct swap_info_struct *si,
134 unsigned long offset, unsigned long flags)
136 swp_entry_t entry = swp_entry(si->type, offset);
140 folio = filemap_get_folio(swap_address_space(entry), offset);
144 * When this function is called from scan_swap_map_slots() and it's
145 * called by vmscan.c at reclaiming folios. So we hold a folio lock
146 * here. We have to use trylock for avoiding deadlock. This is a special
147 * case and you should use folio_free_swap() with explicit folio_lock()
148 * in usual operations.
150 if (folio_trylock(folio)) {
151 if ((flags & TTRS_ANYWAY) ||
152 ((flags & TTRS_UNMAPPED) && !folio_mapped(folio)) ||
153 ((flags & TTRS_FULL) && mem_cgroup_swap_full(folio)))
154 ret = folio_free_swap(folio);
161 static inline struct swap_extent *first_se(struct swap_info_struct *sis)
163 struct rb_node *rb = rb_first(&sis->swap_extent_root);
164 return rb_entry(rb, struct swap_extent, rb_node);
167 static inline struct swap_extent *next_se(struct swap_extent *se)
169 struct rb_node *rb = rb_next(&se->rb_node);
170 return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
174 * swapon tell device that all the old swap contents can be discarded,
175 * to allow the swap device to optimize its wear-levelling.
177 static int discard_swap(struct swap_info_struct *si)
179 struct swap_extent *se;
180 sector_t start_block;
184 /* Do not discard the swap header page! */
186 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
187 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
189 err = blkdev_issue_discard(si->bdev, start_block,
190 nr_blocks, GFP_KERNEL);
196 for (se = next_se(se); se; se = next_se(se)) {
197 start_block = se->start_block << (PAGE_SHIFT - 9);
198 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
200 err = blkdev_issue_discard(si->bdev, start_block,
201 nr_blocks, GFP_KERNEL);
207 return err; /* That will often be -EOPNOTSUPP */
210 static struct swap_extent *
211 offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
213 struct swap_extent *se;
216 rb = sis->swap_extent_root.rb_node;
218 se = rb_entry(rb, struct swap_extent, rb_node);
219 if (offset < se->start_page)
221 else if (offset >= se->start_page + se->nr_pages)
226 /* It *must* be present */
230 sector_t swap_page_sector(struct page *page)
232 struct swap_info_struct *sis = page_swap_info(page);
233 struct swap_extent *se;
237 offset = __page_file_index(page);
238 se = offset_to_swap_extent(sis, offset);
239 sector = se->start_block + (offset - se->start_page);
240 return sector << (PAGE_SHIFT - 9);
244 * swap allocation tell device that a cluster of swap can now be discarded,
245 * to allow the swap device to optimize its wear-levelling.
247 static void discard_swap_cluster(struct swap_info_struct *si,
248 pgoff_t start_page, pgoff_t nr_pages)
250 struct swap_extent *se = offset_to_swap_extent(si, start_page);
253 pgoff_t offset = start_page - se->start_page;
254 sector_t start_block = se->start_block + offset;
255 sector_t nr_blocks = se->nr_pages - offset;
257 if (nr_blocks > nr_pages)
258 nr_blocks = nr_pages;
259 start_page += nr_blocks;
260 nr_pages -= nr_blocks;
262 start_block <<= PAGE_SHIFT - 9;
263 nr_blocks <<= PAGE_SHIFT - 9;
264 if (blkdev_issue_discard(si->bdev, start_block,
265 nr_blocks, GFP_NOIO))
272 #ifdef CONFIG_THP_SWAP
273 #define SWAPFILE_CLUSTER HPAGE_PMD_NR
275 #define swap_entry_size(size) (size)
277 #define SWAPFILE_CLUSTER 256
280 * Define swap_entry_size() as constant to let compiler to optimize
281 * out some code if !CONFIG_THP_SWAP
283 #define swap_entry_size(size) 1
285 #define LATENCY_LIMIT 256
287 static inline void cluster_set_flag(struct swap_cluster_info *info,
293 static inline unsigned int cluster_count(struct swap_cluster_info *info)
298 static inline void cluster_set_count(struct swap_cluster_info *info,
304 static inline void cluster_set_count_flag(struct swap_cluster_info *info,
305 unsigned int c, unsigned int f)
311 static inline unsigned int cluster_next(struct swap_cluster_info *info)
316 static inline void cluster_set_next(struct swap_cluster_info *info,
322 static inline void cluster_set_next_flag(struct swap_cluster_info *info,
323 unsigned int n, unsigned int f)
329 static inline bool cluster_is_free(struct swap_cluster_info *info)
331 return info->flags & CLUSTER_FLAG_FREE;
334 static inline bool cluster_is_null(struct swap_cluster_info *info)
336 return info->flags & CLUSTER_FLAG_NEXT_NULL;
339 static inline void cluster_set_null(struct swap_cluster_info *info)
341 info->flags = CLUSTER_FLAG_NEXT_NULL;
345 static inline bool cluster_is_huge(struct swap_cluster_info *info)
347 if (IS_ENABLED(CONFIG_THP_SWAP))
348 return info->flags & CLUSTER_FLAG_HUGE;
352 static inline void cluster_clear_huge(struct swap_cluster_info *info)
354 info->flags &= ~CLUSTER_FLAG_HUGE;
357 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
358 unsigned long offset)
360 struct swap_cluster_info *ci;
362 ci = si->cluster_info;
364 ci += offset / SWAPFILE_CLUSTER;
365 spin_lock(&ci->lock);
370 static inline void unlock_cluster(struct swap_cluster_info *ci)
373 spin_unlock(&ci->lock);
377 * Determine the locking method in use for this device. Return
378 * swap_cluster_info if SSD-style cluster-based locking is in place.
380 static inline struct swap_cluster_info *lock_cluster_or_swap_info(
381 struct swap_info_struct *si, unsigned long offset)
383 struct swap_cluster_info *ci;
385 /* Try to use fine-grained SSD-style locking if available: */
386 ci = lock_cluster(si, offset);
387 /* Otherwise, fall back to traditional, coarse locking: */
389 spin_lock(&si->lock);
394 static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
395 struct swap_cluster_info *ci)
400 spin_unlock(&si->lock);
403 static inline bool cluster_list_empty(struct swap_cluster_list *list)
405 return cluster_is_null(&list->head);
408 static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
410 return cluster_next(&list->head);
413 static void cluster_list_init(struct swap_cluster_list *list)
415 cluster_set_null(&list->head);
416 cluster_set_null(&list->tail);
419 static void cluster_list_add_tail(struct swap_cluster_list *list,
420 struct swap_cluster_info *ci,
423 if (cluster_list_empty(list)) {
424 cluster_set_next_flag(&list->head, idx, 0);
425 cluster_set_next_flag(&list->tail, idx, 0);
427 struct swap_cluster_info *ci_tail;
428 unsigned int tail = cluster_next(&list->tail);
431 * Nested cluster lock, but both cluster locks are
432 * only acquired when we held swap_info_struct->lock
435 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
436 cluster_set_next(ci_tail, idx);
437 spin_unlock(&ci_tail->lock);
438 cluster_set_next_flag(&list->tail, idx, 0);
442 static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
443 struct swap_cluster_info *ci)
447 idx = cluster_next(&list->head);
448 if (cluster_next(&list->tail) == idx) {
449 cluster_set_null(&list->head);
450 cluster_set_null(&list->tail);
452 cluster_set_next_flag(&list->head,
453 cluster_next(&ci[idx]), 0);
458 /* Add a cluster to discard list and schedule it to do discard */
459 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
463 * If scan_swap_map_slots() can't find a free cluster, it will check
464 * si->swap_map directly. To make sure the discarding cluster isn't
465 * taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
466 * It will be cleared after discard
468 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
469 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
471 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
473 schedule_work(&si->discard_work);
476 static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
478 struct swap_cluster_info *ci = si->cluster_info;
480 cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
481 cluster_list_add_tail(&si->free_clusters, ci, idx);
485 * Doing discard actually. After a cluster discard is finished, the cluster
486 * will be added to free cluster list. caller should hold si->lock.
488 static void swap_do_scheduled_discard(struct swap_info_struct *si)
490 struct swap_cluster_info *info, *ci;
493 info = si->cluster_info;
495 while (!cluster_list_empty(&si->discard_clusters)) {
496 idx = cluster_list_del_first(&si->discard_clusters, info);
497 spin_unlock(&si->lock);
499 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
502 spin_lock(&si->lock);
503 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
504 __free_cluster(si, idx);
505 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
506 0, SWAPFILE_CLUSTER);
511 static void swap_discard_work(struct work_struct *work)
513 struct swap_info_struct *si;
515 si = container_of(work, struct swap_info_struct, discard_work);
517 spin_lock(&si->lock);
518 swap_do_scheduled_discard(si);
519 spin_unlock(&si->lock);
522 static void swap_users_ref_free(struct percpu_ref *ref)
524 struct swap_info_struct *si;
526 si = container_of(ref, struct swap_info_struct, users);
530 static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
532 struct swap_cluster_info *ci = si->cluster_info;
534 VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
535 cluster_list_del_first(&si->free_clusters, ci);
536 cluster_set_count_flag(ci + idx, 0, 0);
539 static void free_cluster(struct swap_info_struct *si, unsigned long idx)
541 struct swap_cluster_info *ci = si->cluster_info + idx;
543 VM_BUG_ON(cluster_count(ci) != 0);
545 * If the swap is discardable, prepare discard the cluster
546 * instead of free it immediately. The cluster will be freed
549 if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
550 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
551 swap_cluster_schedule_discard(si, idx);
555 __free_cluster(si, idx);
559 * The cluster corresponding to page_nr will be used. The cluster will be
560 * removed from free cluster list and its usage counter will be increased.
562 static void inc_cluster_info_page(struct swap_info_struct *p,
563 struct swap_cluster_info *cluster_info, unsigned long page_nr)
565 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
569 if (cluster_is_free(&cluster_info[idx]))
570 alloc_cluster(p, idx);
572 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
573 cluster_set_count(&cluster_info[idx],
574 cluster_count(&cluster_info[idx]) + 1);
578 * The cluster corresponding to page_nr decreases one usage. If the usage
579 * counter becomes 0, which means no page in the cluster is in using, we can
580 * optionally discard the cluster and add it to free cluster list.
582 static void dec_cluster_info_page(struct swap_info_struct *p,
583 struct swap_cluster_info *cluster_info, unsigned long page_nr)
585 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
590 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
591 cluster_set_count(&cluster_info[idx],
592 cluster_count(&cluster_info[idx]) - 1);
594 if (cluster_count(&cluster_info[idx]) == 0)
595 free_cluster(p, idx);
599 * It's possible scan_swap_map_slots() uses a free cluster in the middle of free
600 * cluster list. Avoiding such abuse to avoid list corruption.
603 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
604 unsigned long offset)
606 struct percpu_cluster *percpu_cluster;
609 offset /= SWAPFILE_CLUSTER;
610 conflict = !cluster_list_empty(&si->free_clusters) &&
611 offset != cluster_list_first(&si->free_clusters) &&
612 cluster_is_free(&si->cluster_info[offset]);
617 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
618 cluster_set_null(&percpu_cluster->index);
623 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
624 * might involve allocating a new cluster for current CPU too.
626 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
627 unsigned long *offset, unsigned long *scan_base)
629 struct percpu_cluster *cluster;
630 struct swap_cluster_info *ci;
631 unsigned long tmp, max;
634 cluster = this_cpu_ptr(si->percpu_cluster);
635 if (cluster_is_null(&cluster->index)) {
636 if (!cluster_list_empty(&si->free_clusters)) {
637 cluster->index = si->free_clusters.head;
638 cluster->next = cluster_next(&cluster->index) *
640 } else if (!cluster_list_empty(&si->discard_clusters)) {
642 * we don't have free cluster but have some clusters in
643 * discarding, do discard now and reclaim them, then
644 * reread cluster_next_cpu since we dropped si->lock
646 swap_do_scheduled_discard(si);
647 *scan_base = this_cpu_read(*si->cluster_next_cpu);
648 *offset = *scan_base;
655 * Other CPUs can use our cluster if they can't find a free cluster,
656 * check if there is still free entry in the cluster
659 max = min_t(unsigned long, si->max,
660 (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
662 ci = lock_cluster(si, tmp);
664 if (!si->swap_map[tmp])
671 cluster_set_null(&cluster->index);
674 cluster->next = tmp + 1;
680 static void __del_from_avail_list(struct swap_info_struct *p)
684 assert_spin_locked(&p->lock);
686 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
689 static void del_from_avail_list(struct swap_info_struct *p)
691 spin_lock(&swap_avail_lock);
692 __del_from_avail_list(p);
693 spin_unlock(&swap_avail_lock);
696 static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
697 unsigned int nr_entries)
699 unsigned int end = offset + nr_entries - 1;
701 if (offset == si->lowest_bit)
702 si->lowest_bit += nr_entries;
703 if (end == si->highest_bit)
704 WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
705 WRITE_ONCE(si->inuse_pages, si->inuse_pages + nr_entries);
706 if (si->inuse_pages == si->pages) {
707 si->lowest_bit = si->max;
709 del_from_avail_list(si);
713 static void add_to_avail_list(struct swap_info_struct *p)
717 spin_lock(&swap_avail_lock);
719 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
720 spin_unlock(&swap_avail_lock);
723 static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
724 unsigned int nr_entries)
726 unsigned long begin = offset;
727 unsigned long end = offset + nr_entries - 1;
728 void (*swap_slot_free_notify)(struct block_device *, unsigned long);
730 if (offset < si->lowest_bit)
731 si->lowest_bit = offset;
732 if (end > si->highest_bit) {
733 bool was_full = !si->highest_bit;
735 WRITE_ONCE(si->highest_bit, end);
736 if (was_full && (si->flags & SWP_WRITEOK))
737 add_to_avail_list(si);
739 atomic_long_add(nr_entries, &nr_swap_pages);
740 WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries);
741 if (si->flags & SWP_BLKDEV)
742 swap_slot_free_notify =
743 si->bdev->bd_disk->fops->swap_slot_free_notify;
745 swap_slot_free_notify = NULL;
746 while (offset <= end) {
747 arch_swap_invalidate_page(si->type, offset);
748 zswap_invalidate(si->type, offset);
749 if (swap_slot_free_notify)
750 swap_slot_free_notify(si->bdev, offset);
753 clear_shadow_from_swap_cache(si->type, begin, end);
756 static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
760 if (!(si->flags & SWP_SOLIDSTATE)) {
761 si->cluster_next = next;
765 prev = this_cpu_read(*si->cluster_next_cpu);
767 * Cross the swap address space size aligned trunk, choose
768 * another trunk randomly to avoid lock contention on swap
769 * address space if possible.
771 if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) !=
772 (next >> SWAP_ADDRESS_SPACE_SHIFT)) {
773 /* No free swap slots available */
774 if (si->highest_bit <= si->lowest_bit)
776 next = get_random_u32_inclusive(si->lowest_bit, si->highest_bit);
777 next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
778 next = max_t(unsigned int, next, si->lowest_bit);
780 this_cpu_write(*si->cluster_next_cpu, next);
783 static bool swap_offset_available_and_locked(struct swap_info_struct *si,
784 unsigned long offset)
786 if (data_race(!si->swap_map[offset])) {
787 spin_lock(&si->lock);
791 if (vm_swap_full() && READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
792 spin_lock(&si->lock);
799 static int scan_swap_map_slots(struct swap_info_struct *si,
800 unsigned char usage, int nr,
803 struct swap_cluster_info *ci;
804 unsigned long offset;
805 unsigned long scan_base;
806 unsigned long last_in_cluster = 0;
807 int latency_ration = LATENCY_LIMIT;
809 bool scanned_many = false;
812 * We try to cluster swap pages by allocating them sequentially
813 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
814 * way, however, we resort to first-free allocation, starting
815 * a new cluster. This prevents us from scattering swap pages
816 * all over the entire swap partition, so that we reduce
817 * overall disk seek times between swap pages. -- sct
818 * But we do now try to find an empty cluster. -Andrea
819 * And we let swap pages go all over an SSD partition. Hugh
822 si->flags += SWP_SCANNING;
824 * Use percpu scan base for SSD to reduce lock contention on
825 * cluster and swap cache. For HDD, sequential access is more
828 if (si->flags & SWP_SOLIDSTATE)
829 scan_base = this_cpu_read(*si->cluster_next_cpu);
831 scan_base = si->cluster_next;
835 if (si->cluster_info) {
836 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
838 } else if (unlikely(!si->cluster_nr--)) {
839 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
840 si->cluster_nr = SWAPFILE_CLUSTER - 1;
844 spin_unlock(&si->lock);
847 * If seek is expensive, start searching for new cluster from
848 * start of partition, to minimize the span of allocated swap.
849 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
850 * case, just handled by scan_swap_map_try_ssd_cluster() above.
852 scan_base = offset = si->lowest_bit;
853 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
855 /* Locate the first empty (unaligned) cluster */
856 for (; last_in_cluster <= si->highest_bit; offset++) {
857 if (si->swap_map[offset])
858 last_in_cluster = offset + SWAPFILE_CLUSTER;
859 else if (offset == last_in_cluster) {
860 spin_lock(&si->lock);
861 offset -= SWAPFILE_CLUSTER - 1;
862 si->cluster_next = offset;
863 si->cluster_nr = SWAPFILE_CLUSTER - 1;
866 if (unlikely(--latency_ration < 0)) {
868 latency_ration = LATENCY_LIMIT;
873 spin_lock(&si->lock);
874 si->cluster_nr = SWAPFILE_CLUSTER - 1;
878 if (si->cluster_info) {
879 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
880 /* take a break if we already got some slots */
883 if (!scan_swap_map_try_ssd_cluster(si, &offset,
888 if (!(si->flags & SWP_WRITEOK))
890 if (!si->highest_bit)
892 if (offset > si->highest_bit)
893 scan_base = offset = si->lowest_bit;
895 ci = lock_cluster(si, offset);
896 /* reuse swap entry of cache-only swap if not busy. */
897 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
900 spin_unlock(&si->lock);
901 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
902 spin_lock(&si->lock);
903 /* entry was freed successfully, try to use this again */
906 goto scan; /* check next one */
909 if (si->swap_map[offset]) {
916 WRITE_ONCE(si->swap_map[offset], usage);
917 inc_cluster_info_page(si, si->cluster_info, offset);
920 swap_range_alloc(si, offset, 1);
921 slots[n_ret++] = swp_entry(si->type, offset);
923 /* got enough slots or reach max slots? */
924 if ((n_ret == nr) || (offset >= si->highest_bit))
927 /* search for next available slot */
929 /* time to take a break? */
930 if (unlikely(--latency_ration < 0)) {
933 spin_unlock(&si->lock);
935 spin_lock(&si->lock);
936 latency_ration = LATENCY_LIMIT;
939 /* try to get more slots in cluster */
940 if (si->cluster_info) {
941 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
943 } else if (si->cluster_nr && !si->swap_map[++offset]) {
944 /* non-ssd case, still more slots in cluster? */
950 * Even if there's no free clusters available (fragmented),
951 * try to scan a little more quickly with lock held unless we
952 * have scanned too many slots already.
955 unsigned long scan_limit;
957 if (offset < scan_base)
958 scan_limit = scan_base;
960 scan_limit = si->highest_bit;
961 for (; offset <= scan_limit && --latency_ration > 0;
963 if (!si->swap_map[offset])
969 set_cluster_next(si, offset + 1);
970 si->flags -= SWP_SCANNING;
974 spin_unlock(&si->lock);
975 while (++offset <= READ_ONCE(si->highest_bit)) {
976 if (unlikely(--latency_ration < 0)) {
978 latency_ration = LATENCY_LIMIT;
981 if (swap_offset_available_and_locked(si, offset))
984 offset = si->lowest_bit;
985 while (offset < scan_base) {
986 if (unlikely(--latency_ration < 0)) {
988 latency_ration = LATENCY_LIMIT;
991 if (swap_offset_available_and_locked(si, offset))
995 spin_lock(&si->lock);
998 si->flags -= SWP_SCANNING;
1002 static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
1005 struct swap_cluster_info *ci;
1006 unsigned long offset;
1009 * Should not even be attempting cluster allocations when huge
1010 * page swap is disabled. Warn and fail the allocation.
1012 if (!IS_ENABLED(CONFIG_THP_SWAP)) {
1017 if (cluster_list_empty(&si->free_clusters))
1020 idx = cluster_list_first(&si->free_clusters);
1021 offset = idx * SWAPFILE_CLUSTER;
1022 ci = lock_cluster(si, offset);
1023 alloc_cluster(si, idx);
1024 cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
1026 memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER);
1028 swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
1029 *slot = swp_entry(si->type, offset);
1034 static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
1036 unsigned long offset = idx * SWAPFILE_CLUSTER;
1037 struct swap_cluster_info *ci;
1039 ci = lock_cluster(si, offset);
1040 memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
1041 cluster_set_count_flag(ci, 0, 0);
1042 free_cluster(si, idx);
1044 swap_range_free(si, offset, SWAPFILE_CLUSTER);
1047 int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
1049 unsigned long size = swap_entry_size(entry_size);
1050 struct swap_info_struct *si, *next;
1055 /* Only single cluster request supported */
1056 WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1058 spin_lock(&swap_avail_lock);
1060 avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1061 if (avail_pgs <= 0) {
1062 spin_unlock(&swap_avail_lock);
1066 n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
1068 atomic_long_sub(n_goal * size, &nr_swap_pages);
1071 node = numa_node_id();
1072 plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
1073 /* requeue si to after same-priority siblings */
1074 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
1075 spin_unlock(&swap_avail_lock);
1076 spin_lock(&si->lock);
1077 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
1078 spin_lock(&swap_avail_lock);
1079 if (plist_node_empty(&si->avail_lists[node])) {
1080 spin_unlock(&si->lock);
1083 WARN(!si->highest_bit,
1084 "swap_info %d in list but !highest_bit\n",
1086 WARN(!(si->flags & SWP_WRITEOK),
1087 "swap_info %d in list but !SWP_WRITEOK\n",
1089 __del_from_avail_list(si);
1090 spin_unlock(&si->lock);
1093 if (size == SWAPFILE_CLUSTER) {
1094 if (si->flags & SWP_BLKDEV)
1095 n_ret = swap_alloc_cluster(si, swp_entries);
1097 n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1098 n_goal, swp_entries);
1099 spin_unlock(&si->lock);
1100 if (n_ret || size == SWAPFILE_CLUSTER)
1104 spin_lock(&swap_avail_lock);
1107 * if we got here, it's likely that si was almost full before,
1108 * and since scan_swap_map_slots() can drop the si->lock,
1109 * multiple callers probably all tried to get a page from the
1110 * same si and it filled up before we could get one; or, the si
1111 * filled up between us dropping swap_avail_lock and taking
1112 * si->lock. Since we dropped the swap_avail_lock, the
1113 * swap_avail_head list may have been modified; so if next is
1114 * still in the swap_avail_head list then try it, otherwise
1115 * start over if we have not gotten any slots.
1117 if (plist_node_empty(&next->avail_lists[node]))
1121 spin_unlock(&swap_avail_lock);
1125 atomic_long_add((long)(n_goal - n_ret) * size,
1131 static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1133 struct swap_info_struct *p;
1134 unsigned long offset;
1138 p = swp_swap_info(entry);
1141 if (data_race(!(p->flags & SWP_USED)))
1143 offset = swp_offset(entry);
1144 if (offset >= p->max)
1146 if (data_race(!p->swap_map[swp_offset(entry)]))
1151 pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val);
1154 pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1157 pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
1160 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1165 static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1166 struct swap_info_struct *q)
1168 struct swap_info_struct *p;
1170 p = _swap_info_get(entry);
1174 spin_unlock(&q->lock);
1176 spin_lock(&p->lock);
1181 static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1182 unsigned long offset,
1183 unsigned char usage)
1185 unsigned char count;
1186 unsigned char has_cache;
1188 count = p->swap_map[offset];
1190 has_cache = count & SWAP_HAS_CACHE;
1191 count &= ~SWAP_HAS_CACHE;
1193 if (usage == SWAP_HAS_CACHE) {
1194 VM_BUG_ON(!has_cache);
1196 } else if (count == SWAP_MAP_SHMEM) {
1198 * Or we could insist on shmem.c using a special
1199 * swap_shmem_free() and free_shmem_swap_and_cache()...
1202 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1203 if (count == COUNT_CONTINUED) {
1204 if (swap_count_continued(p, offset, count))
1205 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1207 count = SWAP_MAP_MAX;
1212 usage = count | has_cache;
1214 WRITE_ONCE(p->swap_map[offset], usage);
1216 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
1222 * When we get a swap entry, if there aren't some other ways to
1223 * prevent swapoff, such as the folio in swap cache is locked, page
1224 * table lock is held, etc., the swap entry may become invalid because
1225 * of swapoff. Then, we need to enclose all swap related functions
1226 * with get_swap_device() and put_swap_device(), unless the swap
1227 * functions call get/put_swap_device() by themselves.
1229 * Check whether swap entry is valid in the swap device. If so,
1230 * return pointer to swap_info_struct, and keep the swap entry valid
1231 * via preventing the swap device from being swapoff, until
1232 * put_swap_device() is called. Otherwise return NULL.
1234 * Notice that swapoff or swapoff+swapon can still happen before the
1235 * percpu_ref_tryget_live() in get_swap_device() or after the
1236 * percpu_ref_put() in put_swap_device() if there isn't any other way
1237 * to prevent swapoff. The caller must be prepared for that. For
1238 * example, the following situation is possible.
1242 * ... swapoff+swapon
1243 * __read_swap_cache_async()
1244 * swapcache_prepare()
1245 * __swap_duplicate()
1247 * // verify PTE not changed
1249 * In __swap_duplicate(), the swap_map need to be checked before
1250 * changing partly because the specified swap entry may be for another
1251 * swap device which has been swapoff. And in do_swap_page(), after
1252 * the page is read from the swap device, the PTE is verified not
1253 * changed with the page table locked to check whether the swap device
1254 * has been swapoff or swapoff+swapon.
1256 struct swap_info_struct *get_swap_device(swp_entry_t entry)
1258 struct swap_info_struct *si;
1259 unsigned long offset;
1263 si = swp_swap_info(entry);
1266 if (!percpu_ref_tryget_live(&si->users))
1269 * Guarantee the si->users are checked before accessing other
1270 * fields of swap_info_struct.
1272 * Paired with the spin_unlock() after setup_swap_info() in
1273 * enable_swap_info().
1276 offset = swp_offset(entry);
1277 if (offset >= si->max)
1282 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1286 pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1287 percpu_ref_put(&si->users);
1291 static unsigned char __swap_entry_free(struct swap_info_struct *p,
1294 struct swap_cluster_info *ci;
1295 unsigned long offset = swp_offset(entry);
1296 unsigned char usage;
1298 ci = lock_cluster_or_swap_info(p, offset);
1299 usage = __swap_entry_free_locked(p, offset, 1);
1300 unlock_cluster_or_swap_info(p, ci);
1302 free_swap_slot(entry);
1307 static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1309 struct swap_cluster_info *ci;
1310 unsigned long offset = swp_offset(entry);
1311 unsigned char count;
1313 ci = lock_cluster(p, offset);
1314 count = p->swap_map[offset];
1315 VM_BUG_ON(count != SWAP_HAS_CACHE);
1316 p->swap_map[offset] = 0;
1317 dec_cluster_info_page(p, p->cluster_info, offset);
1320 mem_cgroup_uncharge_swap(entry, 1);
1321 swap_range_free(p, offset, 1);
1325 * Caller has made sure that the swap device corresponding to entry
1326 * is still around or has not been recycled.
1328 void swap_free(swp_entry_t entry)
1330 struct swap_info_struct *p;
1332 p = _swap_info_get(entry);
1334 __swap_entry_free(p, entry);
1338 * Called after dropping swapcache to decrease refcnt to swap entries.
1340 void put_swap_folio(struct folio *folio, swp_entry_t entry)
1342 unsigned long offset = swp_offset(entry);
1343 unsigned long idx = offset / SWAPFILE_CLUSTER;
1344 struct swap_cluster_info *ci;
1345 struct swap_info_struct *si;
1347 unsigned int i, free_entries = 0;
1349 int size = swap_entry_size(folio_nr_pages(folio));
1351 si = _swap_info_get(entry);
1355 ci = lock_cluster_or_swap_info(si, offset);
1356 if (size == SWAPFILE_CLUSTER) {
1357 VM_BUG_ON(!cluster_is_huge(ci));
1358 map = si->swap_map + offset;
1359 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1361 VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1362 if (val == SWAP_HAS_CACHE)
1365 cluster_clear_huge(ci);
1366 if (free_entries == SWAPFILE_CLUSTER) {
1367 unlock_cluster_or_swap_info(si, ci);
1368 spin_lock(&si->lock);
1369 mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1370 swap_free_cluster(si, idx);
1371 spin_unlock(&si->lock);
1375 for (i = 0; i < size; i++, entry.val++) {
1376 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1377 unlock_cluster_or_swap_info(si, ci);
1378 free_swap_slot(entry);
1381 lock_cluster_or_swap_info(si, offset);
1384 unlock_cluster_or_swap_info(si, ci);
1387 #ifdef CONFIG_THP_SWAP
1388 int split_swap_cluster(swp_entry_t entry)
1390 struct swap_info_struct *si;
1391 struct swap_cluster_info *ci;
1392 unsigned long offset = swp_offset(entry);
1394 si = _swap_info_get(entry);
1397 ci = lock_cluster(si, offset);
1398 cluster_clear_huge(ci);
1404 static int swp_entry_cmp(const void *ent1, const void *ent2)
1406 const swp_entry_t *e1 = ent1, *e2 = ent2;
1408 return (int)swp_type(*e1) - (int)swp_type(*e2);
1411 void swapcache_free_entries(swp_entry_t *entries, int n)
1413 struct swap_info_struct *p, *prev;
1423 * Sort swap entries by swap device, so each lock is only taken once.
1424 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1425 * so low that it isn't necessary to optimize further.
1427 if (nr_swapfiles > 1)
1428 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1429 for (i = 0; i < n; ++i) {
1430 p = swap_info_get_cont(entries[i], prev);
1432 swap_entry_free(p, entries[i]);
1436 spin_unlock(&p->lock);
1439 int __swap_count(swp_entry_t entry)
1441 struct swap_info_struct *si = swp_swap_info(entry);
1442 pgoff_t offset = swp_offset(entry);
1444 return swap_count(si->swap_map[offset]);
1448 * How many references to @entry are currently swapped out?
1449 * This does not give an exact answer when swap count is continued,
1450 * but does include the high COUNT_CONTINUED flag to allow for that.
1452 int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1454 pgoff_t offset = swp_offset(entry);
1455 struct swap_cluster_info *ci;
1458 ci = lock_cluster_or_swap_info(si, offset);
1459 count = swap_count(si->swap_map[offset]);
1460 unlock_cluster_or_swap_info(si, ci);
1465 * How many references to @entry are currently swapped out?
1466 * This considers COUNT_CONTINUED so it returns exact answer.
1468 int swp_swapcount(swp_entry_t entry)
1470 int count, tmp_count, n;
1471 struct swap_info_struct *p;
1472 struct swap_cluster_info *ci;
1477 p = _swap_info_get(entry);
1481 offset = swp_offset(entry);
1483 ci = lock_cluster_or_swap_info(p, offset);
1485 count = swap_count(p->swap_map[offset]);
1486 if (!(count & COUNT_CONTINUED))
1489 count &= ~COUNT_CONTINUED;
1490 n = SWAP_MAP_MAX + 1;
1492 page = vmalloc_to_page(p->swap_map + offset);
1493 offset &= ~PAGE_MASK;
1494 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1497 page = list_next_entry(page, lru);
1498 map = kmap_atomic(page);
1499 tmp_count = map[offset];
1502 count += (tmp_count & ~COUNT_CONTINUED) * n;
1503 n *= (SWAP_CONT_MAX + 1);
1504 } while (tmp_count & COUNT_CONTINUED);
1506 unlock_cluster_or_swap_info(p, ci);
1510 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1513 struct swap_cluster_info *ci;
1514 unsigned char *map = si->swap_map;
1515 unsigned long roffset = swp_offset(entry);
1516 unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1520 ci = lock_cluster_or_swap_info(si, offset);
1521 if (!ci || !cluster_is_huge(ci)) {
1522 if (swap_count(map[roffset]))
1526 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1527 if (swap_count(map[offset + i])) {
1533 unlock_cluster_or_swap_info(si, ci);
1537 static bool folio_swapped(struct folio *folio)
1539 swp_entry_t entry = folio_swap_entry(folio);
1540 struct swap_info_struct *si = _swap_info_get(entry);
1545 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!folio_test_large(folio)))
1546 return swap_swapcount(si, entry) != 0;
1548 return swap_page_trans_huge_swapped(si, entry);
1552 * folio_free_swap() - Free the swap space used for this folio.
1553 * @folio: The folio to remove.
1555 * If swap is getting full, or if there are no more mappings of this folio,
1556 * then call folio_free_swap to free its swap space.
1558 * Return: true if we were able to release the swap space.
1560 bool folio_free_swap(struct folio *folio)
1562 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1564 if (!folio_test_swapcache(folio))
1566 if (folio_test_writeback(folio))
1568 if (folio_swapped(folio))
1572 * Once hibernation has begun to create its image of memory,
1573 * there's a danger that one of the calls to folio_free_swap()
1574 * - most probably a call from __try_to_reclaim_swap() while
1575 * hibernation is allocating its own swap pages for the image,
1576 * but conceivably even a call from memory reclaim - will free
1577 * the swap from a folio which has already been recorded in the
1578 * image as a clean swapcache folio, and then reuse its swap for
1579 * another page of the image. On waking from hibernation, the
1580 * original folio might be freed under memory pressure, then
1581 * later read back in from swap, now with the wrong data.
1583 * Hibernation suspends storage while it is writing the image
1584 * to disk so check that here.
1586 if (pm_suspended_storage())
1589 delete_from_swap_cache(folio);
1590 folio_set_dirty(folio);
1595 * Free the swap entry like above, but also try to
1596 * free the page cache entry if it is the last user.
1598 int free_swap_and_cache(swp_entry_t entry)
1600 struct swap_info_struct *p;
1601 unsigned char count;
1603 if (non_swap_entry(entry))
1606 p = _swap_info_get(entry);
1608 count = __swap_entry_free(p, entry);
1609 if (count == SWAP_HAS_CACHE &&
1610 !swap_page_trans_huge_swapped(p, entry))
1611 __try_to_reclaim_swap(p, swp_offset(entry),
1612 TTRS_UNMAPPED | TTRS_FULL);
1617 #ifdef CONFIG_HIBERNATION
1619 swp_entry_t get_swap_page_of_type(int type)
1621 struct swap_info_struct *si = swap_type_to_swap_info(type);
1622 swp_entry_t entry = {0};
1627 /* This is called for allocating swap entry, not cache */
1628 spin_lock(&si->lock);
1629 if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
1630 atomic_long_dec(&nr_swap_pages);
1631 spin_unlock(&si->lock);
1637 * Find the swap type that corresponds to given device (if any).
1639 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1640 * from 0, in which the swap header is expected to be located.
1642 * This is needed for the suspend to disk (aka swsusp).
1644 int swap_type_of(dev_t device, sector_t offset)
1651 spin_lock(&swap_lock);
1652 for (type = 0; type < nr_swapfiles; type++) {
1653 struct swap_info_struct *sis = swap_info[type];
1655 if (!(sis->flags & SWP_WRITEOK))
1658 if (device == sis->bdev->bd_dev) {
1659 struct swap_extent *se = first_se(sis);
1661 if (se->start_block == offset) {
1662 spin_unlock(&swap_lock);
1667 spin_unlock(&swap_lock);
1671 int find_first_swap(dev_t *device)
1675 spin_lock(&swap_lock);
1676 for (type = 0; type < nr_swapfiles; type++) {
1677 struct swap_info_struct *sis = swap_info[type];
1679 if (!(sis->flags & SWP_WRITEOK))
1681 *device = sis->bdev->bd_dev;
1682 spin_unlock(&swap_lock);
1685 spin_unlock(&swap_lock);
1690 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1691 * corresponding to given index in swap_info (swap type).
1693 sector_t swapdev_block(int type, pgoff_t offset)
1695 struct swap_info_struct *si = swap_type_to_swap_info(type);
1696 struct swap_extent *se;
1698 if (!si || !(si->flags & SWP_WRITEOK))
1700 se = offset_to_swap_extent(si, offset);
1701 return se->start_block + (offset - se->start_page);
1705 * Return either the total number of swap pages of given type, or the number
1706 * of free pages of that type (depending on @free)
1708 * This is needed for software suspend
1710 unsigned int count_swap_pages(int type, int free)
1714 spin_lock(&swap_lock);
1715 if ((unsigned int)type < nr_swapfiles) {
1716 struct swap_info_struct *sis = swap_info[type];
1718 spin_lock(&sis->lock);
1719 if (sis->flags & SWP_WRITEOK) {
1722 n -= sis->inuse_pages;
1724 spin_unlock(&sis->lock);
1726 spin_unlock(&swap_lock);
1729 #endif /* CONFIG_HIBERNATION */
1731 static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1733 return pte_same(pte_swp_clear_flags(pte), swp_pte);
1737 * No need to decide whether this PTE shares the swap entry with others,
1738 * just let do_wp_page work it out if a write is requested later - to
1739 * force COW, vm_page_prot omits write permission from any private vma.
1741 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1742 unsigned long addr, swp_entry_t entry, struct folio *folio)
1744 struct page *page = folio_file_page(folio, swp_offset(entry));
1745 struct page *swapcache;
1747 pte_t *pte, new_pte, old_pte;
1748 bool hwpoisoned = PageHWPoison(page);
1752 page = ksm_might_need_to_copy(page, vma, addr);
1753 if (unlikely(!page))
1755 else if (unlikely(PTR_ERR(page) == -EHWPOISON))
1758 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1759 if (unlikely(!pte || !pte_same_as_swp(ptep_get(pte),
1760 swp_entry_to_pte(entry)))) {
1765 old_pte = ptep_get(pte);
1767 if (unlikely(hwpoisoned || !PageUptodate(page))) {
1768 swp_entry_t swp_entry;
1770 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1772 swp_entry = make_hwpoison_entry(swapcache);
1775 swp_entry = make_poisoned_swp_entry();
1777 new_pte = swp_entry_to_pte(swp_entry);
1783 * Some architectures may have to restore extra metadata to the page
1784 * when reading from swap. This metadata may be indexed by swap entry
1785 * so this must be called before swap_free().
1787 arch_swap_restore(entry, page_folio(page));
1789 /* See do_swap_page() */
1790 BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
1791 BUG_ON(PageAnon(page) && PageAnonExclusive(page));
1793 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1794 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1796 if (page == swapcache) {
1797 rmap_t rmap_flags = RMAP_NONE;
1800 * See do_swap_page(): PageWriteback() would be problematic.
1801 * However, we do a wait_on_page_writeback() just before this
1802 * call and have the page locked.
1804 VM_BUG_ON_PAGE(PageWriteback(page), page);
1805 if (pte_swp_exclusive(old_pte))
1806 rmap_flags |= RMAP_EXCLUSIVE;
1808 page_add_anon_rmap(page, vma, addr, rmap_flags);
1809 } else { /* ksm created a completely new copy */
1810 page_add_new_anon_rmap(page, vma, addr);
1811 lru_cache_add_inactive_or_unevictable(page, vma);
1813 new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot));
1814 if (pte_swp_soft_dirty(old_pte))
1815 new_pte = pte_mksoft_dirty(new_pte);
1816 if (pte_swp_uffd_wp(old_pte))
1817 new_pte = pte_mkuffd_wp(new_pte);
1819 set_pte_at(vma->vm_mm, addr, pte, new_pte);
1823 pte_unmap_unlock(pte, ptl);
1824 if (page != swapcache) {
1831 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1832 unsigned long addr, unsigned long end,
1836 struct swap_info_struct *si;
1838 si = swap_info[type];
1840 struct folio *folio;
1841 unsigned long offset;
1842 unsigned char swp_count;
1848 pte = pte_offset_map(pmd, addr);
1853 ptent = ptep_get_lockless(pte);
1855 if (!is_swap_pte(ptent))
1858 entry = pte_to_swp_entry(ptent);
1859 if (swp_type(entry) != type)
1862 offset = swp_offset(entry);
1866 folio = swap_cache_get_folio(entry, vma, addr);
1869 struct vm_fault vmf = {
1872 .real_address = addr,
1876 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
1879 folio = page_folio(page);
1882 swp_count = READ_ONCE(si->swap_map[offset]);
1883 if (swp_count == 0 || swp_count == SWAP_MAP_BAD)
1889 folio_wait_writeback(folio);
1890 ret = unuse_pte(vma, pmd, addr, entry, folio);
1892 folio_unlock(folio);
1897 folio_free_swap(folio);
1898 folio_unlock(folio);
1900 } while (addr += PAGE_SIZE, addr != end);
1907 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1908 unsigned long addr, unsigned long end,
1915 pmd = pmd_offset(pud, addr);
1918 next = pmd_addr_end(addr, end);
1919 ret = unuse_pte_range(vma, pmd, addr, next, type);
1922 } while (pmd++, addr = next, addr != end);
1926 static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
1927 unsigned long addr, unsigned long end,
1934 pud = pud_offset(p4d, addr);
1936 next = pud_addr_end(addr, end);
1937 if (pud_none_or_clear_bad(pud))
1939 ret = unuse_pmd_range(vma, pud, addr, next, type);
1942 } while (pud++, addr = next, addr != end);
1946 static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
1947 unsigned long addr, unsigned long end,
1954 p4d = p4d_offset(pgd, addr);
1956 next = p4d_addr_end(addr, end);
1957 if (p4d_none_or_clear_bad(p4d))
1959 ret = unuse_pud_range(vma, p4d, addr, next, type);
1962 } while (p4d++, addr = next, addr != end);
1966 static int unuse_vma(struct vm_area_struct *vma, unsigned int type)
1969 unsigned long addr, end, next;
1972 addr = vma->vm_start;
1975 pgd = pgd_offset(vma->vm_mm, addr);
1977 next = pgd_addr_end(addr, end);
1978 if (pgd_none_or_clear_bad(pgd))
1980 ret = unuse_p4d_range(vma, pgd, addr, next, type);
1983 } while (pgd++, addr = next, addr != end);
1987 static int unuse_mm(struct mm_struct *mm, unsigned int type)
1989 struct vm_area_struct *vma;
1991 VMA_ITERATOR(vmi, mm, 0);
1994 for_each_vma(vmi, vma) {
1995 if (vma->anon_vma) {
1996 ret = unuse_vma(vma, type);
2003 mmap_read_unlock(mm);
2008 * Scan swap_map from current position to next entry still in use.
2009 * Return 0 if there are no inuse entries after prev till end of
2012 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
2016 unsigned char count;
2019 * No need for swap_lock here: we're just looking
2020 * for whether an entry is in use, not modifying it; false
2021 * hits are okay, and sys_swapoff() has already prevented new
2022 * allocations from this area (while holding swap_lock).
2024 for (i = prev + 1; i < si->max; i++) {
2025 count = READ_ONCE(si->swap_map[i]);
2026 if (count && swap_count(count) != SWAP_MAP_BAD)
2028 if ((i % LATENCY_LIMIT) == 0)
2038 static int try_to_unuse(unsigned int type)
2040 struct mm_struct *prev_mm;
2041 struct mm_struct *mm;
2042 struct list_head *p;
2044 struct swap_info_struct *si = swap_info[type];
2045 struct folio *folio;
2049 if (!READ_ONCE(si->inuse_pages))
2053 retval = shmem_unuse(type);
2060 spin_lock(&mmlist_lock);
2061 p = &init_mm.mmlist;
2062 while (READ_ONCE(si->inuse_pages) &&
2063 !signal_pending(current) &&
2064 (p = p->next) != &init_mm.mmlist) {
2066 mm = list_entry(p, struct mm_struct, mmlist);
2067 if (!mmget_not_zero(mm))
2069 spin_unlock(&mmlist_lock);
2072 retval = unuse_mm(mm, type);
2079 * Make sure that we aren't completely killing
2080 * interactive performance.
2083 spin_lock(&mmlist_lock);
2085 spin_unlock(&mmlist_lock);
2090 while (READ_ONCE(si->inuse_pages) &&
2091 !signal_pending(current) &&
2092 (i = find_next_to_unuse(si, i)) != 0) {
2094 entry = swp_entry(type, i);
2095 folio = filemap_get_folio(swap_address_space(entry), i);
2100 * It is conceivable that a racing task removed this folio from
2101 * swap cache just before we acquired the page lock. The folio
2102 * might even be back in swap cache on another swap area. But
2103 * that is okay, folio_free_swap() only removes stale folios.
2106 folio_wait_writeback(folio);
2107 folio_free_swap(folio);
2108 folio_unlock(folio);
2113 * Lets check again to see if there are still swap entries in the map.
2114 * If yes, we would need to do retry the unuse logic again.
2115 * Under global memory pressure, swap entries can be reinserted back
2116 * into process space after the mmlist loop above passes over them.
2118 * Limit the number of retries? No: when mmget_not_zero()
2119 * above fails, that mm is likely to be freeing swap from
2120 * exit_mmap(), which proceeds at its own independent pace;
2121 * and even shmem_writepage() could have been preempted after
2122 * folio_alloc_swap(), temporarily hiding that swap. It's easy
2123 * and robust (though cpu-intensive) just to keep retrying.
2125 if (READ_ONCE(si->inuse_pages)) {
2126 if (!signal_pending(current))
2135 * After a successful try_to_unuse, if no swap is now in use, we know
2136 * we can empty the mmlist. swap_lock must be held on entry and exit.
2137 * Note that mmlist_lock nests inside swap_lock, and an mm must be
2138 * added to the mmlist just after page_duplicate - before would be racy.
2140 static void drain_mmlist(void)
2142 struct list_head *p, *next;
2145 for (type = 0; type < nr_swapfiles; type++)
2146 if (swap_info[type]->inuse_pages)
2148 spin_lock(&mmlist_lock);
2149 list_for_each_safe(p, next, &init_mm.mmlist)
2151 spin_unlock(&mmlist_lock);
2155 * Free all of a swapdev's extent information
2157 static void destroy_swap_extents(struct swap_info_struct *sis)
2159 while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2160 struct rb_node *rb = sis->swap_extent_root.rb_node;
2161 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2163 rb_erase(rb, &sis->swap_extent_root);
2167 if (sis->flags & SWP_ACTIVATED) {
2168 struct file *swap_file = sis->swap_file;
2169 struct address_space *mapping = swap_file->f_mapping;
2171 sis->flags &= ~SWP_ACTIVATED;
2172 if (mapping->a_ops->swap_deactivate)
2173 mapping->a_ops->swap_deactivate(swap_file);
2178 * Add a block range (and the corresponding page range) into this swapdev's
2181 * This function rather assumes that it is called in ascending page order.
2184 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2185 unsigned long nr_pages, sector_t start_block)
2187 struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2188 struct swap_extent *se;
2189 struct swap_extent *new_se;
2192 * place the new node at the right most since the
2193 * function is called in ascending page order.
2197 link = &parent->rb_right;
2201 se = rb_entry(parent, struct swap_extent, rb_node);
2202 BUG_ON(se->start_page + se->nr_pages != start_page);
2203 if (se->start_block + se->nr_pages == start_block) {
2205 se->nr_pages += nr_pages;
2210 /* No merge, insert a new extent. */
2211 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2214 new_se->start_page = start_page;
2215 new_se->nr_pages = nr_pages;
2216 new_se->start_block = start_block;
2218 rb_link_node(&new_se->rb_node, parent, link);
2219 rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2222 EXPORT_SYMBOL_GPL(add_swap_extent);
2225 * A `swap extent' is a simple thing which maps a contiguous range of pages
2226 * onto a contiguous range of disk blocks. A rbtree of swap extents is
2227 * built at swapon time and is then used at swap_writepage/swap_readpage
2228 * time for locating where on disk a page belongs.
2230 * If the swapfile is an S_ISBLK block device, a single extent is installed.
2231 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2232 * swap files identically.
2234 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2235 * extent rbtree operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
2236 * swapfiles are handled *identically* after swapon time.
2238 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2239 * and will parse them into a rbtree, in PAGE_SIZE chunks. If some stray
2240 * blocks are found which do not fall within the PAGE_SIZE alignment
2241 * requirements, they are simply tossed out - we will never use those blocks
2244 * For all swap devices we set S_SWAPFILE across the life of the swapon. This
2245 * prevents users from writing to the swap device, which will corrupt memory.
2247 * The amount of disk space which a single swap extent represents varies.
2248 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
2249 * extents in the rbtree. - akpm.
2251 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2253 struct file *swap_file = sis->swap_file;
2254 struct address_space *mapping = swap_file->f_mapping;
2255 struct inode *inode = mapping->host;
2258 if (S_ISBLK(inode->i_mode)) {
2259 ret = add_swap_extent(sis, 0, sis->max, 0);
2264 if (mapping->a_ops->swap_activate) {
2265 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2268 sis->flags |= SWP_ACTIVATED;
2269 if ((sis->flags & SWP_FS_OPS) &&
2270 sio_pool_init() != 0) {
2271 destroy_swap_extents(sis);
2277 return generic_swapfile_activate(sis, swap_file, span);
2280 static int swap_node(struct swap_info_struct *p)
2282 struct block_device *bdev;
2287 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2289 return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2292 static void setup_swap_info(struct swap_info_struct *p, int prio,
2293 unsigned char *swap_map,
2294 struct swap_cluster_info *cluster_info)
2301 p->prio = --least_priority;
2303 * the plist prio is negated because plist ordering is
2304 * low-to-high, while swap ordering is high-to-low
2306 p->list.prio = -p->prio;
2309 p->avail_lists[i].prio = -p->prio;
2311 if (swap_node(p) == i)
2312 p->avail_lists[i].prio = 1;
2314 p->avail_lists[i].prio = -p->prio;
2317 p->swap_map = swap_map;
2318 p->cluster_info = cluster_info;
2321 static void _enable_swap_info(struct swap_info_struct *p)
2323 p->flags |= SWP_WRITEOK;
2324 atomic_long_add(p->pages, &nr_swap_pages);
2325 total_swap_pages += p->pages;
2327 assert_spin_locked(&swap_lock);
2329 * both lists are plists, and thus priority ordered.
2330 * swap_active_head needs to be priority ordered for swapoff(),
2331 * which on removal of any swap_info_struct with an auto-assigned
2332 * (i.e. negative) priority increments the auto-assigned priority
2333 * of any lower-priority swap_info_structs.
2334 * swap_avail_head needs to be priority ordered for folio_alloc_swap(),
2335 * which allocates swap pages from the highest available priority
2338 plist_add(&p->list, &swap_active_head);
2340 /* add to available list iff swap device is not full */
2342 add_to_avail_list(p);
2345 static void enable_swap_info(struct swap_info_struct *p, int prio,
2346 unsigned char *swap_map,
2347 struct swap_cluster_info *cluster_info)
2349 zswap_swapon(p->type);
2351 spin_lock(&swap_lock);
2352 spin_lock(&p->lock);
2353 setup_swap_info(p, prio, swap_map, cluster_info);
2354 spin_unlock(&p->lock);
2355 spin_unlock(&swap_lock);
2357 * Finished initializing swap device, now it's safe to reference it.
2359 percpu_ref_resurrect(&p->users);
2360 spin_lock(&swap_lock);
2361 spin_lock(&p->lock);
2362 _enable_swap_info(p);
2363 spin_unlock(&p->lock);
2364 spin_unlock(&swap_lock);
2367 static void reinsert_swap_info(struct swap_info_struct *p)
2369 spin_lock(&swap_lock);
2370 spin_lock(&p->lock);
2371 setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2372 _enable_swap_info(p);
2373 spin_unlock(&p->lock);
2374 spin_unlock(&swap_lock);
2377 bool has_usable_swap(void)
2381 spin_lock(&swap_lock);
2382 if (plist_head_empty(&swap_active_head))
2384 spin_unlock(&swap_lock);
2388 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2390 struct swap_info_struct *p = NULL;
2391 unsigned char *swap_map;
2392 struct swap_cluster_info *cluster_info;
2393 struct file *swap_file, *victim;
2394 struct address_space *mapping;
2395 struct inode *inode;
2396 struct filename *pathname;
2398 unsigned int old_block_size;
2400 if (!capable(CAP_SYS_ADMIN))
2403 BUG_ON(!current->mm);
2405 pathname = getname(specialfile);
2406 if (IS_ERR(pathname))
2407 return PTR_ERR(pathname);
2409 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2410 err = PTR_ERR(victim);
2414 mapping = victim->f_mapping;
2415 spin_lock(&swap_lock);
2416 plist_for_each_entry(p, &swap_active_head, list) {
2417 if (p->flags & SWP_WRITEOK) {
2418 if (p->swap_file->f_mapping == mapping) {
2426 spin_unlock(&swap_lock);
2429 if (!security_vm_enough_memory_mm(current->mm, p->pages))
2430 vm_unacct_memory(p->pages);
2433 spin_unlock(&swap_lock);
2436 spin_lock(&p->lock);
2437 del_from_avail_list(p);
2439 struct swap_info_struct *si = p;
2442 plist_for_each_entry_continue(si, &swap_active_head, list) {
2445 for_each_node(nid) {
2446 if (si->avail_lists[nid].prio != 1)
2447 si->avail_lists[nid].prio--;
2452 plist_del(&p->list, &swap_active_head);
2453 atomic_long_sub(p->pages, &nr_swap_pages);
2454 total_swap_pages -= p->pages;
2455 p->flags &= ~SWP_WRITEOK;
2456 spin_unlock(&p->lock);
2457 spin_unlock(&swap_lock);
2459 disable_swap_slots_cache_lock();
2461 set_current_oom_origin();
2462 err = try_to_unuse(p->type);
2463 clear_current_oom_origin();
2466 /* re-insert swap space back into swap_list */
2467 reinsert_swap_info(p);
2468 reenable_swap_slots_cache_unlock();
2472 reenable_swap_slots_cache_unlock();
2475 * Wait for swap operations protected by get/put_swap_device()
2478 * We need synchronize_rcu() here to protect the accessing to
2479 * the swap cache data structure.
2481 percpu_ref_kill(&p->users);
2483 wait_for_completion(&p->comp);
2485 flush_work(&p->discard_work);
2487 destroy_swap_extents(p);
2488 if (p->flags & SWP_CONTINUED)
2489 free_swap_count_continuations(p);
2491 if (!p->bdev || !bdev_nonrot(p->bdev))
2492 atomic_dec(&nr_rotate_swap);
2494 mutex_lock(&swapon_mutex);
2495 spin_lock(&swap_lock);
2496 spin_lock(&p->lock);
2499 /* wait for anyone still in scan_swap_map_slots */
2500 p->highest_bit = 0; /* cuts scans short */
2501 while (p->flags >= SWP_SCANNING) {
2502 spin_unlock(&p->lock);
2503 spin_unlock(&swap_lock);
2504 schedule_timeout_uninterruptible(1);
2505 spin_lock(&swap_lock);
2506 spin_lock(&p->lock);
2509 swap_file = p->swap_file;
2510 old_block_size = p->old_block_size;
2511 p->swap_file = NULL;
2513 swap_map = p->swap_map;
2515 cluster_info = p->cluster_info;
2516 p->cluster_info = NULL;
2517 spin_unlock(&p->lock);
2518 spin_unlock(&swap_lock);
2519 arch_swap_invalidate_area(p->type);
2520 zswap_swapoff(p->type);
2521 mutex_unlock(&swapon_mutex);
2522 free_percpu(p->percpu_cluster);
2523 p->percpu_cluster = NULL;
2524 free_percpu(p->cluster_next_cpu);
2525 p->cluster_next_cpu = NULL;
2527 kvfree(cluster_info);
2528 /* Destroy swap account information */
2529 swap_cgroup_swapoff(p->type);
2530 exit_swap_address_space(p->type);
2532 inode = mapping->host;
2533 if (S_ISBLK(inode->i_mode)) {
2534 struct block_device *bdev = I_BDEV(inode);
2536 set_blocksize(bdev, old_block_size);
2537 blkdev_put(bdev, p);
2541 inode->i_flags &= ~S_SWAPFILE;
2542 inode_unlock(inode);
2543 filp_close(swap_file, NULL);
2546 * Clear the SWP_USED flag after all resources are freed so that swapon
2547 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
2548 * not hold p->lock after we cleared its SWP_WRITEOK.
2550 spin_lock(&swap_lock);
2552 spin_unlock(&swap_lock);
2555 atomic_inc(&proc_poll_event);
2556 wake_up_interruptible(&proc_poll_wait);
2559 filp_close(victim, NULL);
2565 #ifdef CONFIG_PROC_FS
2566 static __poll_t swaps_poll(struct file *file, poll_table *wait)
2568 struct seq_file *seq = file->private_data;
2570 poll_wait(file, &proc_poll_wait, wait);
2572 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2573 seq->poll_event = atomic_read(&proc_poll_event);
2574 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2577 return EPOLLIN | EPOLLRDNORM;
2581 static void *swap_start(struct seq_file *swap, loff_t *pos)
2583 struct swap_info_struct *si;
2587 mutex_lock(&swapon_mutex);
2590 return SEQ_START_TOKEN;
2592 for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2593 if (!(si->flags & SWP_USED) || !si->swap_map)
2602 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2604 struct swap_info_struct *si = v;
2607 if (v == SEQ_START_TOKEN)
2610 type = si->type + 1;
2613 for (; (si = swap_type_to_swap_info(type)); type++) {
2614 if (!(si->flags & SWP_USED) || !si->swap_map)
2622 static void swap_stop(struct seq_file *swap, void *v)
2624 mutex_unlock(&swapon_mutex);
2627 static int swap_show(struct seq_file *swap, void *v)
2629 struct swap_info_struct *si = v;
2632 unsigned long bytes, inuse;
2634 if (si == SEQ_START_TOKEN) {
2635 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2639 bytes = K(si->pages);
2640 inuse = K(READ_ONCE(si->inuse_pages));
2642 file = si->swap_file;
2643 len = seq_file_path(swap, file, " \t\n\\");
2644 seq_printf(swap, "%*s%s\t%lu\t%s%lu\t%s%d\n",
2645 len < 40 ? 40 - len : 1, " ",
2646 S_ISBLK(file_inode(file)->i_mode) ?
2647 "partition" : "file\t",
2648 bytes, bytes < 10000000 ? "\t" : "",
2649 inuse, inuse < 10000000 ? "\t" : "",
2654 static const struct seq_operations swaps_op = {
2655 .start = swap_start,
2661 static int swaps_open(struct inode *inode, struct file *file)
2663 struct seq_file *seq;
2666 ret = seq_open(file, &swaps_op);
2670 seq = file->private_data;
2671 seq->poll_event = atomic_read(&proc_poll_event);
2675 static const struct proc_ops swaps_proc_ops = {
2676 .proc_flags = PROC_ENTRY_PERMANENT,
2677 .proc_open = swaps_open,
2678 .proc_read = seq_read,
2679 .proc_lseek = seq_lseek,
2680 .proc_release = seq_release,
2681 .proc_poll = swaps_poll,
2684 static int __init procswaps_init(void)
2686 proc_create("swaps", 0, NULL, &swaps_proc_ops);
2689 __initcall(procswaps_init);
2690 #endif /* CONFIG_PROC_FS */
2692 #ifdef MAX_SWAPFILES_CHECK
2693 static int __init max_swapfiles_check(void)
2695 MAX_SWAPFILES_CHECK();
2698 late_initcall(max_swapfiles_check);
2701 static struct swap_info_struct *alloc_swap_info(void)
2703 struct swap_info_struct *p;
2704 struct swap_info_struct *defer = NULL;
2708 p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2710 return ERR_PTR(-ENOMEM);
2712 if (percpu_ref_init(&p->users, swap_users_ref_free,
2713 PERCPU_REF_INIT_DEAD, GFP_KERNEL)) {
2715 return ERR_PTR(-ENOMEM);
2718 spin_lock(&swap_lock);
2719 for (type = 0; type < nr_swapfiles; type++) {
2720 if (!(swap_info[type]->flags & SWP_USED))
2723 if (type >= MAX_SWAPFILES) {
2724 spin_unlock(&swap_lock);
2725 percpu_ref_exit(&p->users);
2727 return ERR_PTR(-EPERM);
2729 if (type >= nr_swapfiles) {
2732 * Publish the swap_info_struct after initializing it.
2733 * Note that kvzalloc() above zeroes all its fields.
2735 smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */
2739 p = swap_info[type];
2741 * Do not memset this entry: a racing procfs swap_next()
2742 * would be relying on p->type to remain valid.
2745 p->swap_extent_root = RB_ROOT;
2746 plist_node_init(&p->list, 0);
2748 plist_node_init(&p->avail_lists[i], 0);
2749 p->flags = SWP_USED;
2750 spin_unlock(&swap_lock);
2752 percpu_ref_exit(&defer->users);
2755 spin_lock_init(&p->lock);
2756 spin_lock_init(&p->cont_lock);
2757 init_completion(&p->comp);
2762 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2766 if (S_ISBLK(inode->i_mode)) {
2767 p->bdev = blkdev_get_by_dev(inode->i_rdev,
2768 BLK_OPEN_READ | BLK_OPEN_WRITE, p, NULL);
2769 if (IS_ERR(p->bdev)) {
2770 error = PTR_ERR(p->bdev);
2774 p->old_block_size = block_size(p->bdev);
2775 error = set_blocksize(p->bdev, PAGE_SIZE);
2779 * Zoned block devices contain zones that have a sequential
2780 * write only restriction. Hence zoned block devices are not
2781 * suitable for swapping. Disallow them here.
2783 if (bdev_is_zoned(p->bdev))
2785 p->flags |= SWP_BLKDEV;
2786 } else if (S_ISREG(inode->i_mode)) {
2787 p->bdev = inode->i_sb->s_bdev;
2795 * Find out how many pages are allowed for a single swap device. There
2796 * are two limiting factors:
2797 * 1) the number of bits for the swap offset in the swp_entry_t type, and
2798 * 2) the number of bits in the swap pte, as defined by the different
2801 * In order to find the largest possible bit mask, a swap entry with
2802 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2803 * decoded to a swp_entry_t again, and finally the swap offset is
2806 * This will mask all the bits from the initial ~0UL mask that can't
2807 * be encoded in either the swp_entry_t or the architecture definition
2810 unsigned long generic_max_swapfile_size(void)
2812 return swp_offset(pte_to_swp_entry(
2813 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2816 /* Can be overridden by an architecture for additional checks. */
2817 __weak unsigned long arch_max_swapfile_size(void)
2819 return generic_max_swapfile_size();
2822 static unsigned long read_swap_header(struct swap_info_struct *p,
2823 union swap_header *swap_header,
2824 struct inode *inode)
2827 unsigned long maxpages;
2828 unsigned long swapfilepages;
2829 unsigned long last_page;
2831 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2832 pr_err("Unable to find swap-space signature\n");
2836 /* swap partition endianness hack... */
2837 if (swab32(swap_header->info.version) == 1) {
2838 swab32s(&swap_header->info.version);
2839 swab32s(&swap_header->info.last_page);
2840 swab32s(&swap_header->info.nr_badpages);
2841 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2843 for (i = 0; i < swap_header->info.nr_badpages; i++)
2844 swab32s(&swap_header->info.badpages[i]);
2846 /* Check the swap header's sub-version */
2847 if (swap_header->info.version != 1) {
2848 pr_warn("Unable to handle swap header version %d\n",
2849 swap_header->info.version);
2854 p->cluster_next = 1;
2857 maxpages = swapfile_maximum_size;
2858 last_page = swap_header->info.last_page;
2860 pr_warn("Empty swap-file\n");
2863 if (last_page > maxpages) {
2864 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2865 K(maxpages), K(last_page));
2867 if (maxpages > last_page) {
2868 maxpages = last_page + 1;
2869 /* p->max is an unsigned int: don't overflow it */
2870 if ((unsigned int)maxpages == 0)
2871 maxpages = UINT_MAX;
2873 p->highest_bit = maxpages - 1;
2877 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2878 if (swapfilepages && maxpages > swapfilepages) {
2879 pr_warn("Swap area shorter than signature indicates\n");
2882 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2884 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2890 #define SWAP_CLUSTER_INFO_COLS \
2891 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
2892 #define SWAP_CLUSTER_SPACE_COLS \
2893 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
2894 #define SWAP_CLUSTER_COLS \
2895 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
2897 static int setup_swap_map_and_extents(struct swap_info_struct *p,
2898 union swap_header *swap_header,
2899 unsigned char *swap_map,
2900 struct swap_cluster_info *cluster_info,
2901 unsigned long maxpages,
2905 unsigned int nr_good_pages;
2907 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2908 unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
2909 unsigned long i, idx;
2911 nr_good_pages = maxpages - 1; /* omit header page */
2913 cluster_list_init(&p->free_clusters);
2914 cluster_list_init(&p->discard_clusters);
2916 for (i = 0; i < swap_header->info.nr_badpages; i++) {
2917 unsigned int page_nr = swap_header->info.badpages[i];
2918 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2920 if (page_nr < maxpages) {
2921 swap_map[page_nr] = SWAP_MAP_BAD;
2924 * Haven't marked the cluster free yet, no list
2925 * operation involved
2927 inc_cluster_info_page(p, cluster_info, page_nr);
2931 /* Haven't marked the cluster free yet, no list operation involved */
2932 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2933 inc_cluster_info_page(p, cluster_info, i);
2935 if (nr_good_pages) {
2936 swap_map[0] = SWAP_MAP_BAD;
2938 * Not mark the cluster free yet, no list
2939 * operation involved
2941 inc_cluster_info_page(p, cluster_info, 0);
2943 p->pages = nr_good_pages;
2944 nr_extents = setup_swap_extents(p, span);
2947 nr_good_pages = p->pages;
2949 if (!nr_good_pages) {
2950 pr_warn("Empty swap-file\n");
2959 * Reduce false cache line sharing between cluster_info and
2960 * sharing same address space.
2962 for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
2963 j = (k + col) % SWAP_CLUSTER_COLS;
2964 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
2965 idx = i * SWAP_CLUSTER_COLS + j;
2966 if (idx >= nr_clusters)
2968 if (cluster_count(&cluster_info[idx]))
2970 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2971 cluster_list_add_tail(&p->free_clusters, cluster_info,
2978 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2980 struct swap_info_struct *p;
2981 struct filename *name;
2982 struct file *swap_file = NULL;
2983 struct address_space *mapping;
2984 struct dentry *dentry;
2987 union swap_header *swap_header;
2990 unsigned long maxpages;
2991 unsigned char *swap_map = NULL;
2992 struct swap_cluster_info *cluster_info = NULL;
2993 struct page *page = NULL;
2994 struct inode *inode = NULL;
2995 bool inced_nr_rotate_swap = false;
2997 if (swap_flags & ~SWAP_FLAGS_VALID)
3000 if (!capable(CAP_SYS_ADMIN))
3003 if (!swap_avail_heads)
3006 p = alloc_swap_info();
3010 INIT_WORK(&p->discard_work, swap_discard_work);
3012 name = getname(specialfile);
3014 error = PTR_ERR(name);
3018 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3019 if (IS_ERR(swap_file)) {
3020 error = PTR_ERR(swap_file);
3025 p->swap_file = swap_file;
3026 mapping = swap_file->f_mapping;
3027 dentry = swap_file->f_path.dentry;
3028 inode = mapping->host;
3030 error = claim_swapfile(p, inode);
3031 if (unlikely(error))
3035 if (d_unlinked(dentry) || cant_mount(dentry)) {
3037 goto bad_swap_unlock_inode;
3039 if (IS_SWAPFILE(inode)) {
3041 goto bad_swap_unlock_inode;
3045 * Read the swap header.
3047 if (!mapping->a_ops->read_folio) {
3049 goto bad_swap_unlock_inode;
3051 page = read_mapping_page(mapping, 0, swap_file);
3053 error = PTR_ERR(page);
3054 goto bad_swap_unlock_inode;
3056 swap_header = kmap(page);
3058 maxpages = read_swap_header(p, swap_header, inode);
3059 if (unlikely(!maxpages)) {
3061 goto bad_swap_unlock_inode;
3064 /* OK, set up the swap map and apply the bad block list */
3065 swap_map = vzalloc(maxpages);
3068 goto bad_swap_unlock_inode;
3071 if (p->bdev && bdev_stable_writes(p->bdev))
3072 p->flags |= SWP_STABLE_WRITES;
3074 if (p->bdev && bdev_synchronous(p->bdev))
3075 p->flags |= SWP_SYNCHRONOUS_IO;
3077 if (p->bdev && bdev_nonrot(p->bdev)) {
3079 unsigned long ci, nr_cluster;
3081 p->flags |= SWP_SOLIDSTATE;
3082 p->cluster_next_cpu = alloc_percpu(unsigned int);
3083 if (!p->cluster_next_cpu) {
3085 goto bad_swap_unlock_inode;
3088 * select a random position to start with to help wear leveling
3091 for_each_possible_cpu(cpu) {
3092 per_cpu(*p->cluster_next_cpu, cpu) =
3093 get_random_u32_inclusive(1, p->highest_bit);
3095 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3097 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3099 if (!cluster_info) {
3101 goto bad_swap_unlock_inode;
3104 for (ci = 0; ci < nr_cluster; ci++)
3105 spin_lock_init(&((cluster_info + ci)->lock));
3107 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3108 if (!p->percpu_cluster) {
3110 goto bad_swap_unlock_inode;
3112 for_each_possible_cpu(cpu) {
3113 struct percpu_cluster *cluster;
3114 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3115 cluster_set_null(&cluster->index);
3118 atomic_inc(&nr_rotate_swap);
3119 inced_nr_rotate_swap = true;
3122 error = swap_cgroup_swapon(p->type, maxpages);
3124 goto bad_swap_unlock_inode;
3126 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3127 cluster_info, maxpages, &span);
3128 if (unlikely(nr_extents < 0)) {
3130 goto bad_swap_unlock_inode;
3133 if ((swap_flags & SWAP_FLAG_DISCARD) &&
3134 p->bdev && bdev_max_discard_sectors(p->bdev)) {
3136 * When discard is enabled for swap with no particular
3137 * policy flagged, we set all swap discard flags here in
3138 * order to sustain backward compatibility with older
3139 * swapon(8) releases.
3141 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3145 * By flagging sys_swapon, a sysadmin can tell us to
3146 * either do single-time area discards only, or to just
3147 * perform discards for released swap page-clusters.
3148 * Now it's time to adjust the p->flags accordingly.
3150 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3151 p->flags &= ~SWP_PAGE_DISCARD;
3152 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3153 p->flags &= ~SWP_AREA_DISCARD;
3155 /* issue a swapon-time discard if it's still required */
3156 if (p->flags & SWP_AREA_DISCARD) {
3157 int err = discard_swap(p);
3159 pr_err("swapon: discard_swap(%p): %d\n",
3164 error = init_swap_address_space(p->type, maxpages);
3166 goto bad_swap_unlock_inode;
3169 * Flush any pending IO and dirty mappings before we start using this
3172 inode->i_flags |= S_SWAPFILE;
3173 error = inode_drain_writes(inode);
3175 inode->i_flags &= ~S_SWAPFILE;
3176 goto free_swap_address_space;
3179 mutex_lock(&swapon_mutex);
3181 if (swap_flags & SWAP_FLAG_PREFER)
3183 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3184 enable_swap_info(p, prio, swap_map, cluster_info);
3186 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s\n",
3187 K(p->pages), name->name, p->prio, nr_extents,
3188 K((unsigned long long)span),
3189 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3190 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3191 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3192 (p->flags & SWP_PAGE_DISCARD) ? "c" : "");
3194 mutex_unlock(&swapon_mutex);
3195 atomic_inc(&proc_poll_event);
3196 wake_up_interruptible(&proc_poll_wait);
3200 free_swap_address_space:
3201 exit_swap_address_space(p->type);
3202 bad_swap_unlock_inode:
3203 inode_unlock(inode);
3205 free_percpu(p->percpu_cluster);
3206 p->percpu_cluster = NULL;
3207 free_percpu(p->cluster_next_cpu);
3208 p->cluster_next_cpu = NULL;
3209 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3210 set_blocksize(p->bdev, p->old_block_size);
3211 blkdev_put(p->bdev, p);
3214 destroy_swap_extents(p);
3215 swap_cgroup_swapoff(p->type);
3216 spin_lock(&swap_lock);
3217 p->swap_file = NULL;
3219 spin_unlock(&swap_lock);
3221 kvfree(cluster_info);
3222 if (inced_nr_rotate_swap)
3223 atomic_dec(&nr_rotate_swap);
3225 filp_close(swap_file, NULL);
3227 if (page && !IS_ERR(page)) {
3234 inode_unlock(inode);
3236 enable_swap_slots_cache();
3240 void si_swapinfo(struct sysinfo *val)
3243 unsigned long nr_to_be_unused = 0;
3245 spin_lock(&swap_lock);
3246 for (type = 0; type < nr_swapfiles; type++) {
3247 struct swap_info_struct *si = swap_info[type];
3249 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3250 nr_to_be_unused += READ_ONCE(si->inuse_pages);
3252 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3253 val->totalswap = total_swap_pages + nr_to_be_unused;
3254 spin_unlock(&swap_lock);
3258 * Verify that a swap entry is valid and increment its swap map count.
3260 * Returns error code in following case.
3262 * - swp_entry is invalid -> EINVAL
3263 * - swp_entry is migration entry -> EINVAL
3264 * - swap-cache reference is requested but there is already one. -> EEXIST
3265 * - swap-cache reference is requested but the entry is not used. -> ENOENT
3266 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3268 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3270 struct swap_info_struct *p;
3271 struct swap_cluster_info *ci;
3272 unsigned long offset;
3273 unsigned char count;
3274 unsigned char has_cache;
3277 p = swp_swap_info(entry);
3279 offset = swp_offset(entry);
3280 ci = lock_cluster_or_swap_info(p, offset);
3282 count = p->swap_map[offset];
3285 * swapin_readahead() doesn't check if a swap entry is valid, so the
3286 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3288 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3293 has_cache = count & SWAP_HAS_CACHE;
3294 count &= ~SWAP_HAS_CACHE;
3297 if (usage == SWAP_HAS_CACHE) {
3299 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3300 if (!has_cache && count)
3301 has_cache = SWAP_HAS_CACHE;
3302 else if (has_cache) /* someone else added cache */
3304 else /* no users remaining */
3307 } else if (count || has_cache) {
3309 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3311 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3313 else if (swap_count_continued(p, offset, count))
3314 count = COUNT_CONTINUED;
3318 err = -ENOENT; /* unused swap entry */
3320 WRITE_ONCE(p->swap_map[offset], count | has_cache);
3323 unlock_cluster_or_swap_info(p, ci);
3328 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3329 * (in which case its reference count is never incremented).
3331 void swap_shmem_alloc(swp_entry_t entry)
3333 __swap_duplicate(entry, SWAP_MAP_SHMEM);
3337 * Increase reference count of swap entry by 1.
3338 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3339 * but could not be atomically allocated. Returns 0, just as if it succeeded,
3340 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3341 * might occur if a page table entry has got corrupted.
3343 int swap_duplicate(swp_entry_t entry)
3347 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3348 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3353 * @entry: swap entry for which we allocate swap cache.
3355 * Called when allocating swap cache for existing swap entry,
3356 * This can return error codes. Returns 0 at success.
3357 * -EEXIST means there is a swap cache.
3358 * Note: return code is different from swap_duplicate().
3360 int swapcache_prepare(swp_entry_t entry)
3362 return __swap_duplicate(entry, SWAP_HAS_CACHE);
3365 struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3367 return swap_type_to_swap_info(swp_type(entry));
3370 struct swap_info_struct *page_swap_info(struct page *page)
3372 swp_entry_t entry = { .val = page_private(page) };
3373 return swp_swap_info(entry);
3377 * out-of-line methods to avoid include hell.
3379 struct address_space *swapcache_mapping(struct folio *folio)
3381 return page_swap_info(&folio->page)->swap_file->f_mapping;
3383 EXPORT_SYMBOL_GPL(swapcache_mapping);
3385 pgoff_t __page_file_index(struct page *page)
3387 swp_entry_t swap = { .val = page_private(page) };
3388 return swp_offset(swap);
3390 EXPORT_SYMBOL_GPL(__page_file_index);
3393 * add_swap_count_continuation - called when a swap count is duplicated
3394 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3395 * page of the original vmalloc'ed swap_map, to hold the continuation count
3396 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
3397 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3399 * These continuation pages are seldom referenced: the common paths all work
3400 * on the original swap_map, only referring to a continuation page when the
3401 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3403 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3404 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3405 * can be called after dropping locks.
3407 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3409 struct swap_info_struct *si;
3410 struct swap_cluster_info *ci;
3413 struct page *list_page;
3415 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 = get_swap_device(entry);
3427 * An acceptable race has occurred since the failing
3428 * __swap_duplicate(): the swap device may be swapoff
3432 spin_lock(&si->lock);
3434 offset = swp_offset(entry);
3436 ci = lock_cluster(si, offset);
3438 count = swap_count(si->swap_map[offset]);
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.
3454 head = vmalloc_to_page(si->swap_map + offset);
3455 offset &= ~PAGE_MASK;
3457 spin_lock(&si->cont_lock);
3459 * Page allocation does not initialize the page's lru field,
3460 * but it does always reset its private field.
3462 if (!page_private(head)) {
3463 BUG_ON(count & COUNT_CONTINUED);
3464 INIT_LIST_HEAD(&head->lru);
3465 set_page_private(head, SWP_CONTINUED);
3466 si->flags |= SWP_CONTINUED;
3469 list_for_each_entry(list_page, &head->lru, lru) {
3473 * If the previous map said no continuation, but we've found
3474 * a continuation page, free our allocation and use this one.
3476 if (!(count & COUNT_CONTINUED))
3477 goto out_unlock_cont;
3479 map = kmap_atomic(list_page) + offset;
3484 * If this continuation count now has some space in it,
3485 * free our allocation and use this one.
3487 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3488 goto out_unlock_cont;
3491 list_add_tail(&page->lru, &head->lru);
3492 page = NULL; /* now it's attached, don't free it */
3494 spin_unlock(&si->cont_lock);
3497 spin_unlock(&si->lock);
3498 put_swap_device(si);
3506 * swap_count_continued - when the original swap_map count is incremented
3507 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3508 * into, carry if so, or else fail until a new continuation page is allocated;
3509 * when the original swap_map count is decremented from 0 with continuation,
3510 * borrow from the continuation and report whether it still holds more.
3511 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3514 static bool swap_count_continued(struct swap_info_struct *si,
3515 pgoff_t offset, unsigned char count)
3522 head = vmalloc_to_page(si->swap_map + offset);
3523 if (page_private(head) != SWP_CONTINUED) {
3524 BUG_ON(count & COUNT_CONTINUED);
3525 return false; /* need to add count continuation */
3528 spin_lock(&si->cont_lock);
3529 offset &= ~PAGE_MASK;
3530 page = list_next_entry(head, lru);
3531 map = kmap_atomic(page) + offset;
3533 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
3534 goto init_map; /* jump over SWAP_CONT_MAX checks */
3536 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3538 * Think of how you add 1 to 999
3540 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3542 page = list_next_entry(page, lru);
3543 BUG_ON(page == head);
3544 map = kmap_atomic(page) + offset;
3546 if (*map == SWAP_CONT_MAX) {
3548 page = list_next_entry(page, lru);
3550 ret = false; /* add count continuation */
3553 map = kmap_atomic(page) + offset;
3554 init_map: *map = 0; /* we didn't zero the page */
3558 while ((page = list_prev_entry(page, lru)) != head) {
3559 map = kmap_atomic(page) + offset;
3560 *map = COUNT_CONTINUED;
3563 ret = true; /* incremented */
3565 } else { /* decrementing */
3567 * Think of how you subtract 1 from 1000
3569 BUG_ON(count != COUNT_CONTINUED);
3570 while (*map == COUNT_CONTINUED) {
3572 page = list_next_entry(page, lru);
3573 BUG_ON(page == head);
3574 map = kmap_atomic(page) + offset;
3581 while ((page = list_prev_entry(page, lru)) != head) {
3582 map = kmap_atomic(page) + offset;
3583 *map = SWAP_CONT_MAX | count;
3584 count = COUNT_CONTINUED;
3587 ret = count == COUNT_CONTINUED;
3590 spin_unlock(&si->cont_lock);
3595 * free_swap_count_continuations - swapoff free all the continuation pages
3596 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3598 static void free_swap_count_continuations(struct swap_info_struct *si)
3602 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3604 head = vmalloc_to_page(si->swap_map + offset);
3605 if (page_private(head)) {
3606 struct page *page, *next;
3608 list_for_each_entry_safe(page, next, &head->lru, lru) {
3609 list_del(&page->lru);
3616 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3617 void __folio_throttle_swaprate(struct folio *folio, gfp_t gfp)
3619 struct swap_info_struct *si, *next;
3620 int nid = folio_nid(folio);
3622 if (!(gfp & __GFP_IO))
3625 if (!blk_cgroup_congested())
3629 * We've already scheduled a throttle, avoid taking the global swap
3632 if (current->throttle_disk)
3635 spin_lock(&swap_avail_lock);
3636 plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
3639 blkcg_schedule_throttle(si->bdev->bd_disk, true);
3643 spin_unlock(&swap_avail_lock);
3647 static int __init swapfile_init(void)
3651 swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3653 if (!swap_avail_heads) {
3654 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3659 plist_head_init(&swap_avail_heads[nid]);
3661 swapfile_maximum_size = arch_max_swapfile_size();
3663 #ifdef CONFIG_MIGRATION
3664 if (swapfile_maximum_size >= (1UL << SWP_MIG_TOTAL_BITS))
3665 swap_migration_ad_supported = true;
3666 #endif /* CONFIG_MIGRATION */
3670 subsys_initcall(swapfile_init);