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
10 #include <linux/sched/mm.h>
11 #include <linux/sched/task.h>
12 #include <linux/hugetlb.h>
13 #include <linux/mman.h>
14 #include <linux/slab.h>
15 #include <linux/kernel_stat.h>
16 #include <linux/swap.h>
17 #include <linux/vmalloc.h>
18 #include <linux/pagemap.h>
19 #include <linux/namei.h>
20 #include <linux/shmem_fs.h>
21 #include <linux/blk-cgroup.h>
22 #include <linux/random.h>
23 #include <linux/writeback.h>
24 #include <linux/proc_fs.h>
25 #include <linux/seq_file.h>
26 #include <linux/init.h>
27 #include <linux/ksm.h>
28 #include <linux/rmap.h>
29 #include <linux/security.h>
30 #include <linux/backing-dev.h>
31 #include <linux/mutex.h>
32 #include <linux/capability.h>
33 #include <linux/syscalls.h>
34 #include <linux/memcontrol.h>
35 #include <linux/poll.h>
36 #include <linux/oom.h>
37 #include <linux/frontswap.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>
44 #include <asm/tlbflush.h>
45 #include <linux/swapops.h>
46 #include <linux/swap_cgroup.h>
48 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
50 static void free_swap_count_continuations(struct swap_info_struct *);
52 static 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 static 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 >= MAX_SWAPFILES)
106 return READ_ONCE(swap_info[type]); /* rcu_dereference() */
109 static inline unsigned char swap_count(unsigned char ent)
111 return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
114 /* Reclaim the swap entry anyway if possible */
115 #define TTRS_ANYWAY 0x1
117 * Reclaim the swap entry if there are no more mappings of the
120 #define TTRS_UNMAPPED 0x2
121 /* Reclaim the swap entry if swap is getting full*/
122 #define TTRS_FULL 0x4
124 /* returns 1 if swap entry is freed */
125 static int __try_to_reclaim_swap(struct swap_info_struct *si,
126 unsigned long offset, unsigned long flags)
128 swp_entry_t entry = swp_entry(si->type, offset);
132 page = find_get_page(swap_address_space(entry), offset);
136 * When this function is called from scan_swap_map_slots() and it's
137 * called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
138 * here. We have to use trylock for avoiding deadlock. This is a special
139 * case and you should use try_to_free_swap() with explicit lock_page()
140 * in usual operations.
142 if (trylock_page(page)) {
143 if ((flags & TTRS_ANYWAY) ||
144 ((flags & TTRS_UNMAPPED) && !page_mapped(page)) ||
145 ((flags & TTRS_FULL) && mem_cgroup_swap_full(page)))
146 ret = try_to_free_swap(page);
153 static inline struct swap_extent *first_se(struct swap_info_struct *sis)
155 struct rb_node *rb = rb_first(&sis->swap_extent_root);
156 return rb_entry(rb, struct swap_extent, rb_node);
159 static inline struct swap_extent *next_se(struct swap_extent *se)
161 struct rb_node *rb = rb_next(&se->rb_node);
162 return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
166 * swapon tell device that all the old swap contents can be discarded,
167 * to allow the swap device to optimize its wear-levelling.
169 static int discard_swap(struct swap_info_struct *si)
171 struct swap_extent *se;
172 sector_t start_block;
176 /* Do not discard the swap header page! */
178 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
179 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
181 err = blkdev_issue_discard(si->bdev, start_block,
182 nr_blocks, GFP_KERNEL, 0);
188 for (se = next_se(se); se; se = next_se(se)) {
189 start_block = se->start_block << (PAGE_SHIFT - 9);
190 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
192 err = blkdev_issue_discard(si->bdev, start_block,
193 nr_blocks, GFP_KERNEL, 0);
199 return err; /* That will often be -EOPNOTSUPP */
202 static struct swap_extent *
203 offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
205 struct swap_extent *se;
208 rb = sis->swap_extent_root.rb_node;
210 se = rb_entry(rb, struct swap_extent, rb_node);
211 if (offset < se->start_page)
213 else if (offset >= se->start_page + se->nr_pages)
218 /* It *must* be present */
222 sector_t swap_page_sector(struct page *page)
224 struct swap_info_struct *sis = page_swap_info(page);
225 struct swap_extent *se;
229 offset = __page_file_index(page);
230 se = offset_to_swap_extent(sis, offset);
231 sector = se->start_block + (offset - se->start_page);
232 return sector << (PAGE_SHIFT - 9);
236 * swap allocation tell device that a cluster of swap can now be discarded,
237 * to allow the swap device to optimize its wear-levelling.
239 static void discard_swap_cluster(struct swap_info_struct *si,
240 pgoff_t start_page, pgoff_t nr_pages)
242 struct swap_extent *se = offset_to_swap_extent(si, start_page);
245 pgoff_t offset = start_page - se->start_page;
246 sector_t start_block = se->start_block + offset;
247 sector_t nr_blocks = se->nr_pages - offset;
249 if (nr_blocks > nr_pages)
250 nr_blocks = nr_pages;
251 start_page += nr_blocks;
252 nr_pages -= nr_blocks;
254 start_block <<= PAGE_SHIFT - 9;
255 nr_blocks <<= PAGE_SHIFT - 9;
256 if (blkdev_issue_discard(si->bdev, start_block,
257 nr_blocks, GFP_NOIO, 0))
264 #ifdef CONFIG_THP_SWAP
265 #define SWAPFILE_CLUSTER HPAGE_PMD_NR
267 #define swap_entry_size(size) (size)
269 #define SWAPFILE_CLUSTER 256
272 * Define swap_entry_size() as constant to let compiler to optimize
273 * out some code if !CONFIG_THP_SWAP
275 #define swap_entry_size(size) 1
277 #define LATENCY_LIMIT 256
279 static inline void cluster_set_flag(struct swap_cluster_info *info,
285 static inline unsigned int cluster_count(struct swap_cluster_info *info)
290 static inline void cluster_set_count(struct swap_cluster_info *info,
296 static inline void cluster_set_count_flag(struct swap_cluster_info *info,
297 unsigned int c, unsigned int f)
303 static inline unsigned int cluster_next(struct swap_cluster_info *info)
308 static inline void cluster_set_next(struct swap_cluster_info *info,
314 static inline void cluster_set_next_flag(struct swap_cluster_info *info,
315 unsigned int n, unsigned int f)
321 static inline bool cluster_is_free(struct swap_cluster_info *info)
323 return info->flags & CLUSTER_FLAG_FREE;
326 static inline bool cluster_is_null(struct swap_cluster_info *info)
328 return info->flags & CLUSTER_FLAG_NEXT_NULL;
331 static inline void cluster_set_null(struct swap_cluster_info *info)
333 info->flags = CLUSTER_FLAG_NEXT_NULL;
337 static inline bool cluster_is_huge(struct swap_cluster_info *info)
339 if (IS_ENABLED(CONFIG_THP_SWAP))
340 return info->flags & CLUSTER_FLAG_HUGE;
344 static inline void cluster_clear_huge(struct swap_cluster_info *info)
346 info->flags &= ~CLUSTER_FLAG_HUGE;
349 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
350 unsigned long offset)
352 struct swap_cluster_info *ci;
354 ci = si->cluster_info;
356 ci += offset / SWAPFILE_CLUSTER;
357 spin_lock(&ci->lock);
362 static inline void unlock_cluster(struct swap_cluster_info *ci)
365 spin_unlock(&ci->lock);
369 * Determine the locking method in use for this device. Return
370 * swap_cluster_info if SSD-style cluster-based locking is in place.
372 static inline struct swap_cluster_info *lock_cluster_or_swap_info(
373 struct swap_info_struct *si, unsigned long offset)
375 struct swap_cluster_info *ci;
377 /* Try to use fine-grained SSD-style locking if available: */
378 ci = lock_cluster(si, offset);
379 /* Otherwise, fall back to traditional, coarse locking: */
381 spin_lock(&si->lock);
386 static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
387 struct swap_cluster_info *ci)
392 spin_unlock(&si->lock);
395 static inline bool cluster_list_empty(struct swap_cluster_list *list)
397 return cluster_is_null(&list->head);
400 static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
402 return cluster_next(&list->head);
405 static void cluster_list_init(struct swap_cluster_list *list)
407 cluster_set_null(&list->head);
408 cluster_set_null(&list->tail);
411 static void cluster_list_add_tail(struct swap_cluster_list *list,
412 struct swap_cluster_info *ci,
415 if (cluster_list_empty(list)) {
416 cluster_set_next_flag(&list->head, idx, 0);
417 cluster_set_next_flag(&list->tail, idx, 0);
419 struct swap_cluster_info *ci_tail;
420 unsigned int tail = cluster_next(&list->tail);
423 * Nested cluster lock, but both cluster locks are
424 * only acquired when we held swap_info_struct->lock
427 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
428 cluster_set_next(ci_tail, idx);
429 spin_unlock(&ci_tail->lock);
430 cluster_set_next_flag(&list->tail, idx, 0);
434 static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
435 struct swap_cluster_info *ci)
439 idx = cluster_next(&list->head);
440 if (cluster_next(&list->tail) == idx) {
441 cluster_set_null(&list->head);
442 cluster_set_null(&list->tail);
444 cluster_set_next_flag(&list->head,
445 cluster_next(&ci[idx]), 0);
450 /* Add a cluster to discard list and schedule it to do discard */
451 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
455 * If scan_swap_map_slots() can't find a free cluster, it will check
456 * si->swap_map directly. To make sure the discarding cluster isn't
457 * taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
458 * It will be cleared after discard
460 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
461 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
463 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
465 schedule_work(&si->discard_work);
468 static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
470 struct swap_cluster_info *ci = si->cluster_info;
472 cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
473 cluster_list_add_tail(&si->free_clusters, ci, idx);
477 * Doing discard actually. After a cluster discard is finished, the cluster
478 * will be added to free cluster list. caller should hold si->lock.
480 static void swap_do_scheduled_discard(struct swap_info_struct *si)
482 struct swap_cluster_info *info, *ci;
485 info = si->cluster_info;
487 while (!cluster_list_empty(&si->discard_clusters)) {
488 idx = cluster_list_del_first(&si->discard_clusters, info);
489 spin_unlock(&si->lock);
491 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
494 spin_lock(&si->lock);
495 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
496 __free_cluster(si, idx);
497 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
498 0, SWAPFILE_CLUSTER);
503 static void swap_discard_work(struct work_struct *work)
505 struct swap_info_struct *si;
507 si = container_of(work, struct swap_info_struct, discard_work);
509 spin_lock(&si->lock);
510 swap_do_scheduled_discard(si);
511 spin_unlock(&si->lock);
514 static void swap_users_ref_free(struct percpu_ref *ref)
516 struct swap_info_struct *si;
518 si = container_of(ref, struct swap_info_struct, users);
522 static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
524 struct swap_cluster_info *ci = si->cluster_info;
526 VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
527 cluster_list_del_first(&si->free_clusters, ci);
528 cluster_set_count_flag(ci + idx, 0, 0);
531 static void free_cluster(struct swap_info_struct *si, unsigned long idx)
533 struct swap_cluster_info *ci = si->cluster_info + idx;
535 VM_BUG_ON(cluster_count(ci) != 0);
537 * If the swap is discardable, prepare discard the cluster
538 * instead of free it immediately. The cluster will be freed
541 if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
542 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
543 swap_cluster_schedule_discard(si, idx);
547 __free_cluster(si, idx);
551 * The cluster corresponding to page_nr will be used. The cluster will be
552 * removed from free cluster list and its usage counter will be increased.
554 static void inc_cluster_info_page(struct swap_info_struct *p,
555 struct swap_cluster_info *cluster_info, unsigned long page_nr)
557 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
561 if (cluster_is_free(&cluster_info[idx]))
562 alloc_cluster(p, idx);
564 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
565 cluster_set_count(&cluster_info[idx],
566 cluster_count(&cluster_info[idx]) + 1);
570 * The cluster corresponding to page_nr decreases one usage. If the usage
571 * counter becomes 0, which means no page in the cluster is in using, we can
572 * optionally discard the cluster and add it to free cluster list.
574 static void dec_cluster_info_page(struct swap_info_struct *p,
575 struct swap_cluster_info *cluster_info, unsigned long page_nr)
577 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
582 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
583 cluster_set_count(&cluster_info[idx],
584 cluster_count(&cluster_info[idx]) - 1);
586 if (cluster_count(&cluster_info[idx]) == 0)
587 free_cluster(p, idx);
591 * It's possible scan_swap_map_slots() uses a free cluster in the middle of free
592 * cluster list. Avoiding such abuse to avoid list corruption.
595 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
596 unsigned long offset)
598 struct percpu_cluster *percpu_cluster;
601 offset /= SWAPFILE_CLUSTER;
602 conflict = !cluster_list_empty(&si->free_clusters) &&
603 offset != cluster_list_first(&si->free_clusters) &&
604 cluster_is_free(&si->cluster_info[offset]);
609 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
610 cluster_set_null(&percpu_cluster->index);
615 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
616 * might involve allocating a new cluster for current CPU too.
618 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
619 unsigned long *offset, unsigned long *scan_base)
621 struct percpu_cluster *cluster;
622 struct swap_cluster_info *ci;
623 unsigned long tmp, max;
626 cluster = this_cpu_ptr(si->percpu_cluster);
627 if (cluster_is_null(&cluster->index)) {
628 if (!cluster_list_empty(&si->free_clusters)) {
629 cluster->index = si->free_clusters.head;
630 cluster->next = cluster_next(&cluster->index) *
632 } else if (!cluster_list_empty(&si->discard_clusters)) {
634 * we don't have free cluster but have some clusters in
635 * discarding, do discard now and reclaim them, then
636 * reread cluster_next_cpu since we dropped si->lock
638 swap_do_scheduled_discard(si);
639 *scan_base = this_cpu_read(*si->cluster_next_cpu);
640 *offset = *scan_base;
647 * Other CPUs can use our cluster if they can't find a free cluster,
648 * check if there is still free entry in the cluster
651 max = min_t(unsigned long, si->max,
652 (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
654 ci = lock_cluster(si, tmp);
656 if (!si->swap_map[tmp])
663 cluster_set_null(&cluster->index);
666 cluster->next = tmp + 1;
672 static void __del_from_avail_list(struct swap_info_struct *p)
677 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
680 static void del_from_avail_list(struct swap_info_struct *p)
682 spin_lock(&swap_avail_lock);
683 __del_from_avail_list(p);
684 spin_unlock(&swap_avail_lock);
687 static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
688 unsigned int nr_entries)
690 unsigned int end = offset + nr_entries - 1;
692 if (offset == si->lowest_bit)
693 si->lowest_bit += nr_entries;
694 if (end == si->highest_bit)
695 WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
696 si->inuse_pages += nr_entries;
697 if (si->inuse_pages == si->pages) {
698 si->lowest_bit = si->max;
700 del_from_avail_list(si);
704 static void add_to_avail_list(struct swap_info_struct *p)
708 spin_lock(&swap_avail_lock);
710 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
711 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
713 spin_unlock(&swap_avail_lock);
716 static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
717 unsigned int nr_entries)
719 unsigned long begin = offset;
720 unsigned long end = offset + nr_entries - 1;
721 void (*swap_slot_free_notify)(struct block_device *, unsigned long);
723 if (offset < si->lowest_bit)
724 si->lowest_bit = offset;
725 if (end > si->highest_bit) {
726 bool was_full = !si->highest_bit;
728 WRITE_ONCE(si->highest_bit, end);
729 if (was_full && (si->flags & SWP_WRITEOK))
730 add_to_avail_list(si);
732 atomic_long_add(nr_entries, &nr_swap_pages);
733 si->inuse_pages -= nr_entries;
734 if (si->flags & SWP_BLKDEV)
735 swap_slot_free_notify =
736 si->bdev->bd_disk->fops->swap_slot_free_notify;
738 swap_slot_free_notify = NULL;
739 while (offset <= end) {
740 arch_swap_invalidate_page(si->type, offset);
741 frontswap_invalidate_page(si->type, offset);
742 if (swap_slot_free_notify)
743 swap_slot_free_notify(si->bdev, offset);
746 clear_shadow_from_swap_cache(si->type, begin, end);
749 static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
753 if (!(si->flags & SWP_SOLIDSTATE)) {
754 si->cluster_next = next;
758 prev = this_cpu_read(*si->cluster_next_cpu);
760 * Cross the swap address space size aligned trunk, choose
761 * another trunk randomly to avoid lock contention on swap
762 * address space if possible.
764 if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) !=
765 (next >> SWAP_ADDRESS_SPACE_SHIFT)) {
766 /* No free swap slots available */
767 if (si->highest_bit <= si->lowest_bit)
769 next = si->lowest_bit +
770 prandom_u32_max(si->highest_bit - si->lowest_bit + 1);
771 next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
772 next = max_t(unsigned int, next, si->lowest_bit);
774 this_cpu_write(*si->cluster_next_cpu, next);
777 static int scan_swap_map_slots(struct swap_info_struct *si,
778 unsigned char usage, int nr,
781 struct swap_cluster_info *ci;
782 unsigned long offset;
783 unsigned long scan_base;
784 unsigned long last_in_cluster = 0;
785 int latency_ration = LATENCY_LIMIT;
787 bool scanned_many = false;
790 * We try to cluster swap pages by allocating them sequentially
791 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
792 * way, however, we resort to first-free allocation, starting
793 * a new cluster. This prevents us from scattering swap pages
794 * all over the entire swap partition, so that we reduce
795 * overall disk seek times between swap pages. -- sct
796 * But we do now try to find an empty cluster. -Andrea
797 * And we let swap pages go all over an SSD partition. Hugh
800 si->flags += SWP_SCANNING;
802 * Use percpu scan base for SSD to reduce lock contention on
803 * cluster and swap cache. For HDD, sequential access is more
806 if (si->flags & SWP_SOLIDSTATE)
807 scan_base = this_cpu_read(*si->cluster_next_cpu);
809 scan_base = si->cluster_next;
813 if (si->cluster_info) {
814 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
816 } else if (unlikely(!si->cluster_nr--)) {
817 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
818 si->cluster_nr = SWAPFILE_CLUSTER - 1;
822 spin_unlock(&si->lock);
825 * If seek is expensive, start searching for new cluster from
826 * start of partition, to minimize the span of allocated swap.
827 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
828 * case, just handled by scan_swap_map_try_ssd_cluster() above.
830 scan_base = offset = si->lowest_bit;
831 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
833 /* Locate the first empty (unaligned) cluster */
834 for (; last_in_cluster <= si->highest_bit; offset++) {
835 if (si->swap_map[offset])
836 last_in_cluster = offset + SWAPFILE_CLUSTER;
837 else if (offset == last_in_cluster) {
838 spin_lock(&si->lock);
839 offset -= SWAPFILE_CLUSTER - 1;
840 si->cluster_next = offset;
841 si->cluster_nr = SWAPFILE_CLUSTER - 1;
844 if (unlikely(--latency_ration < 0)) {
846 latency_ration = LATENCY_LIMIT;
851 spin_lock(&si->lock);
852 si->cluster_nr = SWAPFILE_CLUSTER - 1;
856 if (si->cluster_info) {
857 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
858 /* take a break if we already got some slots */
861 if (!scan_swap_map_try_ssd_cluster(si, &offset,
866 if (!(si->flags & SWP_WRITEOK))
868 if (!si->highest_bit)
870 if (offset > si->highest_bit)
871 scan_base = offset = si->lowest_bit;
873 ci = lock_cluster(si, offset);
874 /* reuse swap entry of cache-only swap if not busy. */
875 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
878 spin_unlock(&si->lock);
879 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
880 spin_lock(&si->lock);
881 /* entry was freed successfully, try to use this again */
884 goto scan; /* check next one */
887 if (si->swap_map[offset]) {
894 WRITE_ONCE(si->swap_map[offset], usage);
895 inc_cluster_info_page(si, si->cluster_info, offset);
898 swap_range_alloc(si, offset, 1);
899 slots[n_ret++] = swp_entry(si->type, offset);
901 /* got enough slots or reach max slots? */
902 if ((n_ret == nr) || (offset >= si->highest_bit))
905 /* search for next available slot */
907 /* time to take a break? */
908 if (unlikely(--latency_ration < 0)) {
911 spin_unlock(&si->lock);
913 spin_lock(&si->lock);
914 latency_ration = LATENCY_LIMIT;
917 /* try to get more slots in cluster */
918 if (si->cluster_info) {
919 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
921 } else if (si->cluster_nr && !si->swap_map[++offset]) {
922 /* non-ssd case, still more slots in cluster? */
928 * Even if there's no free clusters available (fragmented),
929 * try to scan a little more quickly with lock held unless we
930 * have scanned too many slots already.
933 unsigned long scan_limit;
935 if (offset < scan_base)
936 scan_limit = scan_base;
938 scan_limit = si->highest_bit;
939 for (; offset <= scan_limit && --latency_ration > 0;
941 if (!si->swap_map[offset])
947 set_cluster_next(si, offset + 1);
948 si->flags -= SWP_SCANNING;
952 spin_unlock(&si->lock);
953 while (++offset <= READ_ONCE(si->highest_bit)) {
954 if (data_race(!si->swap_map[offset])) {
955 spin_lock(&si->lock);
958 if (vm_swap_full() &&
959 READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
960 spin_lock(&si->lock);
963 if (unlikely(--latency_ration < 0)) {
965 latency_ration = LATENCY_LIMIT;
969 offset = si->lowest_bit;
970 while (offset < scan_base) {
971 if (data_race(!si->swap_map[offset])) {
972 spin_lock(&si->lock);
975 if (vm_swap_full() &&
976 READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
977 spin_lock(&si->lock);
980 if (unlikely(--latency_ration < 0)) {
982 latency_ration = LATENCY_LIMIT;
987 spin_lock(&si->lock);
990 si->flags -= SWP_SCANNING;
994 static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
997 struct swap_cluster_info *ci;
998 unsigned long offset;
1001 * Should not even be attempting cluster allocations when huge
1002 * page swap is disabled. Warn and fail the allocation.
1004 if (!IS_ENABLED(CONFIG_THP_SWAP)) {
1009 if (cluster_list_empty(&si->free_clusters))
1012 idx = cluster_list_first(&si->free_clusters);
1013 offset = idx * SWAPFILE_CLUSTER;
1014 ci = lock_cluster(si, offset);
1015 alloc_cluster(si, idx);
1016 cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
1018 memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER);
1020 swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
1021 *slot = swp_entry(si->type, offset);
1026 static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
1028 unsigned long offset = idx * SWAPFILE_CLUSTER;
1029 struct swap_cluster_info *ci;
1031 ci = lock_cluster(si, offset);
1032 memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
1033 cluster_set_count_flag(ci, 0, 0);
1034 free_cluster(si, idx);
1036 swap_range_free(si, offset, SWAPFILE_CLUSTER);
1039 int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
1041 unsigned long size = swap_entry_size(entry_size);
1042 struct swap_info_struct *si, *next;
1047 /* Only single cluster request supported */
1048 WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1050 spin_lock(&swap_avail_lock);
1052 avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1053 if (avail_pgs <= 0) {
1054 spin_unlock(&swap_avail_lock);
1058 n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
1060 atomic_long_sub(n_goal * size, &nr_swap_pages);
1063 node = numa_node_id();
1064 plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
1065 /* requeue si to after same-priority siblings */
1066 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
1067 spin_unlock(&swap_avail_lock);
1068 spin_lock(&si->lock);
1069 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
1070 spin_lock(&swap_avail_lock);
1071 if (plist_node_empty(&si->avail_lists[node])) {
1072 spin_unlock(&si->lock);
1075 WARN(!si->highest_bit,
1076 "swap_info %d in list but !highest_bit\n",
1078 WARN(!(si->flags & SWP_WRITEOK),
1079 "swap_info %d in list but !SWP_WRITEOK\n",
1081 __del_from_avail_list(si);
1082 spin_unlock(&si->lock);
1085 if (size == SWAPFILE_CLUSTER) {
1086 if (si->flags & SWP_BLKDEV)
1087 n_ret = swap_alloc_cluster(si, swp_entries);
1089 n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1090 n_goal, swp_entries);
1091 spin_unlock(&si->lock);
1092 if (n_ret || size == SWAPFILE_CLUSTER)
1094 pr_debug("scan_swap_map of si %d failed to find offset\n",
1097 spin_lock(&swap_avail_lock);
1100 * if we got here, it's likely that si was almost full before,
1101 * and since scan_swap_map_slots() can drop the si->lock,
1102 * multiple callers probably all tried to get a page from the
1103 * same si and it filled up before we could get one; or, the si
1104 * filled up between us dropping swap_avail_lock and taking
1105 * si->lock. Since we dropped the swap_avail_lock, the
1106 * swap_avail_head list may have been modified; so if next is
1107 * still in the swap_avail_head list then try it, otherwise
1108 * start over if we have not gotten any slots.
1110 if (plist_node_empty(&next->avail_lists[node]))
1114 spin_unlock(&swap_avail_lock);
1118 atomic_long_add((long)(n_goal - n_ret) * size,
1124 static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
1126 struct swap_info_struct *p;
1127 unsigned long offset;
1131 p = swp_swap_info(entry);
1134 if (data_race(!(p->flags & SWP_USED)))
1136 offset = swp_offset(entry);
1137 if (offset >= p->max)
1142 pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1145 pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
1148 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1153 static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1155 struct swap_info_struct *p;
1157 p = __swap_info_get(entry);
1160 if (data_race(!p->swap_map[swp_offset(entry)]))
1165 pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val);
1170 static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1171 struct swap_info_struct *q)
1173 struct swap_info_struct *p;
1175 p = _swap_info_get(entry);
1179 spin_unlock(&q->lock);
1181 spin_lock(&p->lock);
1186 static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1187 unsigned long offset,
1188 unsigned char usage)
1190 unsigned char count;
1191 unsigned char has_cache;
1193 count = p->swap_map[offset];
1195 has_cache = count & SWAP_HAS_CACHE;
1196 count &= ~SWAP_HAS_CACHE;
1198 if (usage == SWAP_HAS_CACHE) {
1199 VM_BUG_ON(!has_cache);
1201 } else if (count == SWAP_MAP_SHMEM) {
1203 * Or we could insist on shmem.c using a special
1204 * swap_shmem_free() and free_shmem_swap_and_cache()...
1207 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1208 if (count == COUNT_CONTINUED) {
1209 if (swap_count_continued(p, offset, count))
1210 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1212 count = SWAP_MAP_MAX;
1217 usage = count | has_cache;
1219 WRITE_ONCE(p->swap_map[offset], usage);
1221 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
1227 * Check whether swap entry is valid in the swap device. If so,
1228 * return pointer to swap_info_struct, and keep the swap entry valid
1229 * via preventing the swap device from being swapoff, until
1230 * put_swap_device() is called. Otherwise return NULL.
1232 * Notice that swapoff or swapoff+swapon can still happen before the
1233 * percpu_ref_tryget_live() in get_swap_device() or after the
1234 * percpu_ref_put() in put_swap_device() if there isn't any other way
1235 * to prevent swapoff, such as page lock, page table lock, etc. The
1236 * caller must be prepared for that. For example, the following
1237 * situation is possible.
1241 * ... swapoff+swapon
1242 * __read_swap_cache_async()
1243 * swapcache_prepare()
1244 * __swap_duplicate()
1246 * // verify PTE not changed
1248 * In __swap_duplicate(), the swap_map need to be checked before
1249 * changing partly because the specified swap entry may be for another
1250 * swap device which has been swapoff. And in do_swap_page(), after
1251 * the page is read from the swap device, the PTE is verified not
1252 * changed with the page table locked to check whether the swap device
1253 * has been swapoff or swapoff+swapon.
1255 struct swap_info_struct *get_swap_device(swp_entry_t entry)
1257 struct swap_info_struct *si;
1258 unsigned long offset;
1262 si = swp_swap_info(entry);
1265 if (!percpu_ref_tryget_live(&si->users))
1268 * Guarantee the si->users are checked before accessing other
1269 * fields of swap_info_struct.
1271 * Paired with the spin_unlock() after setup_swap_info() in
1272 * enable_swap_info().
1275 offset = swp_offset(entry);
1276 if (offset >= si->max)
1281 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1285 percpu_ref_put(&si->users);
1289 static unsigned char __swap_entry_free(struct swap_info_struct *p,
1292 struct swap_cluster_info *ci;
1293 unsigned long offset = swp_offset(entry);
1294 unsigned char usage;
1296 ci = lock_cluster_or_swap_info(p, offset);
1297 usage = __swap_entry_free_locked(p, offset, 1);
1298 unlock_cluster_or_swap_info(p, ci);
1300 free_swap_slot(entry);
1305 static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1307 struct swap_cluster_info *ci;
1308 unsigned long offset = swp_offset(entry);
1309 unsigned char count;
1311 ci = lock_cluster(p, offset);
1312 count = p->swap_map[offset];
1313 VM_BUG_ON(count != SWAP_HAS_CACHE);
1314 p->swap_map[offset] = 0;
1315 dec_cluster_info_page(p, p->cluster_info, offset);
1318 mem_cgroup_uncharge_swap(entry, 1);
1319 swap_range_free(p, offset, 1);
1323 * Caller has made sure that the swap device corresponding to entry
1324 * is still around or has not been recycled.
1326 void swap_free(swp_entry_t entry)
1328 struct swap_info_struct *p;
1330 p = _swap_info_get(entry);
1332 __swap_entry_free(p, entry);
1336 * Called after dropping swapcache to decrease refcnt to swap entries.
1338 void put_swap_page(struct page *page, swp_entry_t entry)
1340 unsigned long offset = swp_offset(entry);
1341 unsigned long idx = offset / SWAPFILE_CLUSTER;
1342 struct swap_cluster_info *ci;
1343 struct swap_info_struct *si;
1345 unsigned int i, free_entries = 0;
1347 int size = swap_entry_size(thp_nr_pages(page));
1349 si = _swap_info_get(entry);
1353 ci = lock_cluster_or_swap_info(si, offset);
1354 if (size == SWAPFILE_CLUSTER) {
1355 VM_BUG_ON(!cluster_is_huge(ci));
1356 map = si->swap_map + offset;
1357 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1359 VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1360 if (val == SWAP_HAS_CACHE)
1363 cluster_clear_huge(ci);
1364 if (free_entries == SWAPFILE_CLUSTER) {
1365 unlock_cluster_or_swap_info(si, ci);
1366 spin_lock(&si->lock);
1367 mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1368 swap_free_cluster(si, idx);
1369 spin_unlock(&si->lock);
1373 for (i = 0; i < size; i++, entry.val++) {
1374 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1375 unlock_cluster_or_swap_info(si, ci);
1376 free_swap_slot(entry);
1379 lock_cluster_or_swap_info(si, offset);
1382 unlock_cluster_or_swap_info(si, ci);
1385 #ifdef CONFIG_THP_SWAP
1386 int split_swap_cluster(swp_entry_t entry)
1388 struct swap_info_struct *si;
1389 struct swap_cluster_info *ci;
1390 unsigned long offset = swp_offset(entry);
1392 si = _swap_info_get(entry);
1395 ci = lock_cluster(si, offset);
1396 cluster_clear_huge(ci);
1402 static int swp_entry_cmp(const void *ent1, const void *ent2)
1404 const swp_entry_t *e1 = ent1, *e2 = ent2;
1406 return (int)swp_type(*e1) - (int)swp_type(*e2);
1409 void swapcache_free_entries(swp_entry_t *entries, int n)
1411 struct swap_info_struct *p, *prev;
1421 * Sort swap entries by swap device, so each lock is only taken once.
1422 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1423 * so low that it isn't necessary to optimize further.
1425 if (nr_swapfiles > 1)
1426 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1427 for (i = 0; i < n; ++i) {
1428 p = swap_info_get_cont(entries[i], prev);
1430 swap_entry_free(p, entries[i]);
1434 spin_unlock(&p->lock);
1438 * How many references to page are currently swapped out?
1439 * This does not give an exact answer when swap count is continued,
1440 * but does include the high COUNT_CONTINUED flag to allow for that.
1442 int page_swapcount(struct page *page)
1445 struct swap_info_struct *p;
1446 struct swap_cluster_info *ci;
1448 unsigned long offset;
1450 entry.val = page_private(page);
1451 p = _swap_info_get(entry);
1453 offset = swp_offset(entry);
1454 ci = lock_cluster_or_swap_info(p, offset);
1455 count = swap_count(p->swap_map[offset]);
1456 unlock_cluster_or_swap_info(p, ci);
1461 int __swap_count(swp_entry_t entry)
1463 struct swap_info_struct *si;
1464 pgoff_t offset = swp_offset(entry);
1467 si = get_swap_device(entry);
1469 count = swap_count(si->swap_map[offset]);
1470 put_swap_device(si);
1475 static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1478 pgoff_t offset = swp_offset(entry);
1479 struct swap_cluster_info *ci;
1481 ci = lock_cluster_or_swap_info(si, offset);
1482 count = swap_count(si->swap_map[offset]);
1483 unlock_cluster_or_swap_info(si, ci);
1488 * How many references to @entry are currently swapped out?
1489 * This does not give an exact answer when swap count is continued,
1490 * but does include the high COUNT_CONTINUED flag to allow for that.
1492 int __swp_swapcount(swp_entry_t entry)
1495 struct swap_info_struct *si;
1497 si = get_swap_device(entry);
1499 count = swap_swapcount(si, entry);
1500 put_swap_device(si);
1506 * How many references to @entry are currently swapped out?
1507 * This considers COUNT_CONTINUED so it returns exact answer.
1509 int swp_swapcount(swp_entry_t entry)
1511 int count, tmp_count, n;
1512 struct swap_info_struct *p;
1513 struct swap_cluster_info *ci;
1518 p = _swap_info_get(entry);
1522 offset = swp_offset(entry);
1524 ci = lock_cluster_or_swap_info(p, offset);
1526 count = swap_count(p->swap_map[offset]);
1527 if (!(count & COUNT_CONTINUED))
1530 count &= ~COUNT_CONTINUED;
1531 n = SWAP_MAP_MAX + 1;
1533 page = vmalloc_to_page(p->swap_map + offset);
1534 offset &= ~PAGE_MASK;
1535 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1538 page = list_next_entry(page, lru);
1539 map = kmap_atomic(page);
1540 tmp_count = map[offset];
1543 count += (tmp_count & ~COUNT_CONTINUED) * n;
1544 n *= (SWAP_CONT_MAX + 1);
1545 } while (tmp_count & COUNT_CONTINUED);
1547 unlock_cluster_or_swap_info(p, ci);
1551 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1554 struct swap_cluster_info *ci;
1555 unsigned char *map = si->swap_map;
1556 unsigned long roffset = swp_offset(entry);
1557 unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1561 ci = lock_cluster_or_swap_info(si, offset);
1562 if (!ci || !cluster_is_huge(ci)) {
1563 if (swap_count(map[roffset]))
1567 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1568 if (swap_count(map[offset + i])) {
1574 unlock_cluster_or_swap_info(si, ci);
1578 static bool page_swapped(struct page *page)
1581 struct swap_info_struct *si;
1583 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
1584 return page_swapcount(page) != 0;
1586 page = compound_head(page);
1587 entry.val = page_private(page);
1588 si = _swap_info_get(entry);
1590 return swap_page_trans_huge_swapped(si, entry);
1595 * If swap is getting full, or if there are no more mappings of this page,
1596 * then try_to_free_swap is called to free its swap space.
1598 int try_to_free_swap(struct page *page)
1600 VM_BUG_ON_PAGE(!PageLocked(page), page);
1602 if (!PageSwapCache(page))
1604 if (PageWriteback(page))
1606 if (page_swapped(page))
1610 * Once hibernation has begun to create its image of memory,
1611 * there's a danger that one of the calls to try_to_free_swap()
1612 * - most probably a call from __try_to_reclaim_swap() while
1613 * hibernation is allocating its own swap pages for the image,
1614 * but conceivably even a call from memory reclaim - will free
1615 * the swap from a page which has already been recorded in the
1616 * image as a clean swapcache page, and then reuse its swap for
1617 * another page of the image. On waking from hibernation, the
1618 * original page might be freed under memory pressure, then
1619 * later read back in from swap, now with the wrong data.
1621 * Hibernation suspends storage while it is writing the image
1622 * to disk so check that here.
1624 if (pm_suspended_storage())
1627 page = compound_head(page);
1628 delete_from_swap_cache(page);
1634 * Free the swap entry like above, but also try to
1635 * free the page cache entry if it is the last user.
1637 int free_swap_and_cache(swp_entry_t entry)
1639 struct swap_info_struct *p;
1640 unsigned char count;
1642 if (non_swap_entry(entry))
1645 p = _swap_info_get(entry);
1647 count = __swap_entry_free(p, entry);
1648 if (count == SWAP_HAS_CACHE &&
1649 !swap_page_trans_huge_swapped(p, entry))
1650 __try_to_reclaim_swap(p, swp_offset(entry),
1651 TTRS_UNMAPPED | TTRS_FULL);
1656 #ifdef CONFIG_HIBERNATION
1658 swp_entry_t get_swap_page_of_type(int type)
1660 struct swap_info_struct *si = swap_type_to_swap_info(type);
1661 swp_entry_t entry = {0};
1666 /* This is called for allocating swap entry, not cache */
1667 spin_lock(&si->lock);
1668 if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
1669 atomic_long_dec(&nr_swap_pages);
1670 spin_unlock(&si->lock);
1676 * Find the swap type that corresponds to given device (if any).
1678 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1679 * from 0, in which the swap header is expected to be located.
1681 * This is needed for the suspend to disk (aka swsusp).
1683 int swap_type_of(dev_t device, sector_t offset)
1690 spin_lock(&swap_lock);
1691 for (type = 0; type < nr_swapfiles; type++) {
1692 struct swap_info_struct *sis = swap_info[type];
1694 if (!(sis->flags & SWP_WRITEOK))
1697 if (device == sis->bdev->bd_dev) {
1698 struct swap_extent *se = first_se(sis);
1700 if (se->start_block == offset) {
1701 spin_unlock(&swap_lock);
1706 spin_unlock(&swap_lock);
1710 int find_first_swap(dev_t *device)
1714 spin_lock(&swap_lock);
1715 for (type = 0; type < nr_swapfiles; type++) {
1716 struct swap_info_struct *sis = swap_info[type];
1718 if (!(sis->flags & SWP_WRITEOK))
1720 *device = sis->bdev->bd_dev;
1721 spin_unlock(&swap_lock);
1724 spin_unlock(&swap_lock);
1729 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1730 * corresponding to given index in swap_info (swap type).
1732 sector_t swapdev_block(int type, pgoff_t offset)
1734 struct swap_info_struct *si = swap_type_to_swap_info(type);
1735 struct swap_extent *se;
1737 if (!si || !(si->flags & SWP_WRITEOK))
1739 se = offset_to_swap_extent(si, offset);
1740 return se->start_block + (offset - se->start_page);
1744 * Return either the total number of swap pages of given type, or the number
1745 * of free pages of that type (depending on @free)
1747 * This is needed for software suspend
1749 unsigned int count_swap_pages(int type, int free)
1753 spin_lock(&swap_lock);
1754 if ((unsigned int)type < nr_swapfiles) {
1755 struct swap_info_struct *sis = swap_info[type];
1757 spin_lock(&sis->lock);
1758 if (sis->flags & SWP_WRITEOK) {
1761 n -= sis->inuse_pages;
1763 spin_unlock(&sis->lock);
1765 spin_unlock(&swap_lock);
1768 #endif /* CONFIG_HIBERNATION */
1770 static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1772 return pte_same(pte_swp_clear_flags(pte), swp_pte);
1776 * No need to decide whether this PTE shares the swap entry with others,
1777 * just let do_wp_page work it out if a write is requested later - to
1778 * force COW, vm_page_prot omits write permission from any private vma.
1780 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1781 unsigned long addr, swp_entry_t entry, struct page *page)
1783 struct page *swapcache;
1789 page = ksm_might_need_to_copy(page, vma, addr);
1790 if (unlikely(!page))
1793 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1794 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1799 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1800 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1802 if (page == swapcache) {
1803 page_add_anon_rmap(page, vma, addr, false);
1804 } else { /* ksm created a completely new copy */
1805 page_add_new_anon_rmap(page, vma, addr, false);
1806 lru_cache_add_inactive_or_unevictable(page, vma);
1808 set_pte_at(vma->vm_mm, addr, pte,
1809 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1812 pte_unmap_unlock(pte, ptl);
1813 if (page != swapcache) {
1820 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1821 unsigned long addr, unsigned long end,
1827 struct swap_info_struct *si;
1828 unsigned long offset;
1830 volatile unsigned char *swap_map;
1832 si = swap_info[type];
1833 pte = pte_offset_map(pmd, addr);
1835 if (!is_swap_pte(*pte))
1838 entry = pte_to_swp_entry(*pte);
1839 if (swp_type(entry) != type)
1842 offset = swp_offset(entry);
1844 swap_map = &si->swap_map[offset];
1845 page = lookup_swap_cache(entry, vma, addr);
1847 struct vm_fault vmf = {
1850 .real_address = addr,
1854 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
1858 if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1864 wait_on_page_writeback(page);
1865 ret = unuse_pte(vma, pmd, addr, entry, page);
1872 try_to_free_swap(page);
1876 pte = pte_offset_map(pmd, addr);
1877 } while (pte++, addr += PAGE_SIZE, addr != end);
1885 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1886 unsigned long addr, unsigned long end,
1893 pmd = pmd_offset(pud, addr);
1896 next = pmd_addr_end(addr, end);
1897 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1899 ret = unuse_pte_range(vma, pmd, addr, next, type);
1902 } while (pmd++, addr = next, addr != end);
1906 static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
1907 unsigned long addr, unsigned long end,
1914 pud = pud_offset(p4d, addr);
1916 next = pud_addr_end(addr, end);
1917 if (pud_none_or_clear_bad(pud))
1919 ret = unuse_pmd_range(vma, pud, addr, next, type);
1922 } while (pud++, addr = next, addr != end);
1926 static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
1927 unsigned long addr, unsigned long end,
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);
1942 } while (p4d++, addr = next, addr != end);
1946 static int unuse_vma(struct vm_area_struct *vma, unsigned int type)
1949 unsigned long addr, end, next;
1952 addr = vma->vm_start;
1955 pgd = pgd_offset(vma->vm_mm, addr);
1957 next = pgd_addr_end(addr, end);
1958 if (pgd_none_or_clear_bad(pgd))
1960 ret = unuse_p4d_range(vma, pgd, addr, next, type);
1963 } while (pgd++, addr = next, addr != end);
1967 static int unuse_mm(struct mm_struct *mm, unsigned int type)
1969 struct vm_area_struct *vma;
1973 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1974 if (vma->anon_vma) {
1975 ret = unuse_vma(vma, type);
1981 mmap_read_unlock(mm);
1986 * Scan swap_map (or frontswap_map if frontswap parameter is true)
1987 * from current position to next entry still in use. Return 0
1988 * if there are no inuse entries after prev till end of the map.
1990 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1994 unsigned char count;
1997 * No need for swap_lock here: we're just looking
1998 * for whether an entry is in use, not modifying it; false
1999 * hits are okay, and sys_swapoff() has already prevented new
2000 * allocations from this area (while holding swap_lock).
2002 for (i = prev + 1; i < si->max; i++) {
2003 count = READ_ONCE(si->swap_map[i]);
2004 if (count && swap_count(count) != SWAP_MAP_BAD)
2006 if ((i % LATENCY_LIMIT) == 0)
2016 static int try_to_unuse(unsigned int type)
2018 struct mm_struct *prev_mm;
2019 struct mm_struct *mm;
2020 struct list_head *p;
2022 struct swap_info_struct *si = swap_info[type];
2027 if (!READ_ONCE(si->inuse_pages))
2031 retval = shmem_unuse(type);
2038 spin_lock(&mmlist_lock);
2039 p = &init_mm.mmlist;
2040 while (READ_ONCE(si->inuse_pages) &&
2041 !signal_pending(current) &&
2042 (p = p->next) != &init_mm.mmlist) {
2044 mm = list_entry(p, struct mm_struct, mmlist);
2045 if (!mmget_not_zero(mm))
2047 spin_unlock(&mmlist_lock);
2050 retval = unuse_mm(mm, type);
2057 * Make sure that we aren't completely killing
2058 * interactive performance.
2061 spin_lock(&mmlist_lock);
2063 spin_unlock(&mmlist_lock);
2068 while (READ_ONCE(si->inuse_pages) &&
2069 !signal_pending(current) &&
2070 (i = find_next_to_unuse(si, i)) != 0) {
2072 entry = swp_entry(type, i);
2073 page = find_get_page(swap_address_space(entry), i);
2078 * It is conceivable that a racing task removed this page from
2079 * swap cache just before we acquired the page lock. The page
2080 * might even be back in swap cache on another swap area. But
2081 * that is okay, try_to_free_swap() only removes stale pages.
2084 wait_on_page_writeback(page);
2085 try_to_free_swap(page);
2091 * Lets check again to see if there are still swap entries in the map.
2092 * If yes, we would need to do retry the unuse logic again.
2093 * Under global memory pressure, swap entries can be reinserted back
2094 * into process space after the mmlist loop above passes over them.
2096 * Limit the number of retries? No: when mmget_not_zero() above fails,
2097 * that mm is likely to be freeing swap from exit_mmap(), which proceeds
2098 * at its own independent pace; and even shmem_writepage() could have
2099 * been preempted after get_swap_page(), temporarily hiding that swap.
2100 * It's easy and robust (though cpu-intensive) just to keep retrying.
2102 if (READ_ONCE(si->inuse_pages)) {
2103 if (!signal_pending(current))
2112 * After a successful try_to_unuse, if no swap is now in use, we know
2113 * we can empty the mmlist. swap_lock must be held on entry and exit.
2114 * Note that mmlist_lock nests inside swap_lock, and an mm must be
2115 * added to the mmlist just after page_duplicate - before would be racy.
2117 static void drain_mmlist(void)
2119 struct list_head *p, *next;
2122 for (type = 0; type < nr_swapfiles; type++)
2123 if (swap_info[type]->inuse_pages)
2125 spin_lock(&mmlist_lock);
2126 list_for_each_safe(p, next, &init_mm.mmlist)
2128 spin_unlock(&mmlist_lock);
2132 * Free all of a swapdev's extent information
2134 static void destroy_swap_extents(struct swap_info_struct *sis)
2136 while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2137 struct rb_node *rb = sis->swap_extent_root.rb_node;
2138 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2140 rb_erase(rb, &sis->swap_extent_root);
2144 if (sis->flags & SWP_ACTIVATED) {
2145 struct file *swap_file = sis->swap_file;
2146 struct address_space *mapping = swap_file->f_mapping;
2148 sis->flags &= ~SWP_ACTIVATED;
2149 if (mapping->a_ops->swap_deactivate)
2150 mapping->a_ops->swap_deactivate(swap_file);
2155 * Add a block range (and the corresponding page range) into this swapdev's
2158 * This function rather assumes that it is called in ascending page order.
2161 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2162 unsigned long nr_pages, sector_t start_block)
2164 struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2165 struct swap_extent *se;
2166 struct swap_extent *new_se;
2169 * place the new node at the right most since the
2170 * function is called in ascending page order.
2174 link = &parent->rb_right;
2178 se = rb_entry(parent, struct swap_extent, rb_node);
2179 BUG_ON(se->start_page + se->nr_pages != start_page);
2180 if (se->start_block + se->nr_pages == start_block) {
2182 se->nr_pages += nr_pages;
2187 /* No merge, insert a new extent. */
2188 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2191 new_se->start_page = start_page;
2192 new_se->nr_pages = nr_pages;
2193 new_se->start_block = start_block;
2195 rb_link_node(&new_se->rb_node, parent, link);
2196 rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2199 EXPORT_SYMBOL_GPL(add_swap_extent);
2202 * A `swap extent' is a simple thing which maps a contiguous range of pages
2203 * onto a contiguous range of disk blocks. An ordered list of swap extents
2204 * is built at swapon time and is then used at swap_writepage/swap_readpage
2205 * time for locating where on disk a page belongs.
2207 * If the swapfile is an S_ISBLK block device, a single extent is installed.
2208 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2209 * swap files identically.
2211 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2212 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
2213 * swapfiles are handled *identically* after swapon time.
2215 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2216 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
2217 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
2218 * requirements, they are simply tossed out - we will never use those blocks
2221 * For all swap devices we set S_SWAPFILE across the life of the swapon. This
2222 * prevents users from writing to the swap device, which will corrupt memory.
2224 * The amount of disk space which a single swap extent represents varies.
2225 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
2226 * extents in the list. To avoid much list walking, we cache the previous
2227 * search location in `curr_swap_extent', and start new searches from there.
2228 * This is extremely effective. The average number of iterations in
2229 * map_swap_page() has been measured at about 0.3 per page. - akpm.
2231 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2233 struct file *swap_file = sis->swap_file;
2234 struct address_space *mapping = swap_file->f_mapping;
2235 struct inode *inode = mapping->host;
2238 if (S_ISBLK(inode->i_mode)) {
2239 ret = add_swap_extent(sis, 0, sis->max, 0);
2244 if (mapping->a_ops->swap_activate) {
2245 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2247 sis->flags |= SWP_ACTIVATED;
2249 sis->flags |= SWP_FS_OPS;
2250 ret = add_swap_extent(sis, 0, sis->max, 0);
2256 return generic_swapfile_activate(sis, swap_file, span);
2259 static int swap_node(struct swap_info_struct *p)
2261 struct block_device *bdev;
2266 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2268 return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2271 static void setup_swap_info(struct swap_info_struct *p, int prio,
2272 unsigned char *swap_map,
2273 struct swap_cluster_info *cluster_info)
2280 p->prio = --least_priority;
2282 * the plist prio is negated because plist ordering is
2283 * low-to-high, while swap ordering is high-to-low
2285 p->list.prio = -p->prio;
2288 p->avail_lists[i].prio = -p->prio;
2290 if (swap_node(p) == i)
2291 p->avail_lists[i].prio = 1;
2293 p->avail_lists[i].prio = -p->prio;
2296 p->swap_map = swap_map;
2297 p->cluster_info = cluster_info;
2300 static void _enable_swap_info(struct swap_info_struct *p)
2302 p->flags |= SWP_WRITEOK;
2303 atomic_long_add(p->pages, &nr_swap_pages);
2304 total_swap_pages += p->pages;
2306 assert_spin_locked(&swap_lock);
2308 * both lists are plists, and thus priority ordered.
2309 * swap_active_head needs to be priority ordered for swapoff(),
2310 * which on removal of any swap_info_struct with an auto-assigned
2311 * (i.e. negative) priority increments the auto-assigned priority
2312 * of any lower-priority swap_info_structs.
2313 * swap_avail_head needs to be priority ordered for get_swap_page(),
2314 * which allocates swap pages from the highest available priority
2317 plist_add(&p->list, &swap_active_head);
2318 add_to_avail_list(p);
2321 static void enable_swap_info(struct swap_info_struct *p, int prio,
2322 unsigned char *swap_map,
2323 struct swap_cluster_info *cluster_info,
2324 unsigned long *frontswap_map)
2326 if (IS_ENABLED(CONFIG_FRONTSWAP))
2327 frontswap_init(p->type, frontswap_map);
2328 spin_lock(&swap_lock);
2329 spin_lock(&p->lock);
2330 setup_swap_info(p, prio, swap_map, cluster_info);
2331 spin_unlock(&p->lock);
2332 spin_unlock(&swap_lock);
2334 * Finished initializing swap device, now it's safe to reference it.
2336 percpu_ref_resurrect(&p->users);
2337 spin_lock(&swap_lock);
2338 spin_lock(&p->lock);
2339 _enable_swap_info(p);
2340 spin_unlock(&p->lock);
2341 spin_unlock(&swap_lock);
2344 static void reinsert_swap_info(struct swap_info_struct *p)
2346 spin_lock(&swap_lock);
2347 spin_lock(&p->lock);
2348 setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2349 _enable_swap_info(p);
2350 spin_unlock(&p->lock);
2351 spin_unlock(&swap_lock);
2354 bool has_usable_swap(void)
2358 spin_lock(&swap_lock);
2359 if (plist_head_empty(&swap_active_head))
2361 spin_unlock(&swap_lock);
2365 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2367 struct swap_info_struct *p = NULL;
2368 unsigned char *swap_map;
2369 struct swap_cluster_info *cluster_info;
2370 unsigned long *frontswap_map;
2371 struct file *swap_file, *victim;
2372 struct address_space *mapping;
2373 struct inode *inode;
2374 struct filename *pathname;
2376 unsigned int old_block_size;
2378 if (!capable(CAP_SYS_ADMIN))
2381 BUG_ON(!current->mm);
2383 pathname = getname(specialfile);
2384 if (IS_ERR(pathname))
2385 return PTR_ERR(pathname);
2387 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2388 err = PTR_ERR(victim);
2392 mapping = victim->f_mapping;
2393 spin_lock(&swap_lock);
2394 plist_for_each_entry(p, &swap_active_head, list) {
2395 if (p->flags & SWP_WRITEOK) {
2396 if (p->swap_file->f_mapping == mapping) {
2404 spin_unlock(&swap_lock);
2407 if (!security_vm_enough_memory_mm(current->mm, p->pages))
2408 vm_unacct_memory(p->pages);
2411 spin_unlock(&swap_lock);
2414 del_from_avail_list(p);
2415 spin_lock(&p->lock);
2417 struct swap_info_struct *si = p;
2420 plist_for_each_entry_continue(si, &swap_active_head, list) {
2423 for_each_node(nid) {
2424 if (si->avail_lists[nid].prio != 1)
2425 si->avail_lists[nid].prio--;
2430 plist_del(&p->list, &swap_active_head);
2431 atomic_long_sub(p->pages, &nr_swap_pages);
2432 total_swap_pages -= p->pages;
2433 p->flags &= ~SWP_WRITEOK;
2434 spin_unlock(&p->lock);
2435 spin_unlock(&swap_lock);
2437 disable_swap_slots_cache_lock();
2439 set_current_oom_origin();
2440 err = try_to_unuse(p->type);
2441 clear_current_oom_origin();
2444 /* re-insert swap space back into swap_list */
2445 reinsert_swap_info(p);
2446 reenable_swap_slots_cache_unlock();
2450 reenable_swap_slots_cache_unlock();
2453 * Wait for swap operations protected by get/put_swap_device()
2456 * We need synchronize_rcu() here to protect the accessing to
2457 * the swap cache data structure.
2459 percpu_ref_kill(&p->users);
2461 wait_for_completion(&p->comp);
2463 flush_work(&p->discard_work);
2465 destroy_swap_extents(p);
2466 if (p->flags & SWP_CONTINUED)
2467 free_swap_count_continuations(p);
2469 if (!p->bdev || !blk_queue_nonrot(bdev_get_queue(p->bdev)))
2470 atomic_dec(&nr_rotate_swap);
2472 mutex_lock(&swapon_mutex);
2473 spin_lock(&swap_lock);
2474 spin_lock(&p->lock);
2477 /* wait for anyone still in scan_swap_map_slots */
2478 p->highest_bit = 0; /* cuts scans short */
2479 while (p->flags >= SWP_SCANNING) {
2480 spin_unlock(&p->lock);
2481 spin_unlock(&swap_lock);
2482 schedule_timeout_uninterruptible(1);
2483 spin_lock(&swap_lock);
2484 spin_lock(&p->lock);
2487 swap_file = p->swap_file;
2488 old_block_size = p->old_block_size;
2489 p->swap_file = NULL;
2491 swap_map = p->swap_map;
2493 cluster_info = p->cluster_info;
2494 p->cluster_info = NULL;
2495 frontswap_map = frontswap_map_get(p);
2496 spin_unlock(&p->lock);
2497 spin_unlock(&swap_lock);
2498 arch_swap_invalidate_area(p->type);
2499 frontswap_invalidate_area(p->type);
2500 frontswap_map_set(p, NULL);
2501 mutex_unlock(&swapon_mutex);
2502 free_percpu(p->percpu_cluster);
2503 p->percpu_cluster = NULL;
2504 free_percpu(p->cluster_next_cpu);
2505 p->cluster_next_cpu = NULL;
2507 kvfree(cluster_info);
2508 kvfree(frontswap_map);
2509 /* Destroy swap account information */
2510 swap_cgroup_swapoff(p->type);
2511 exit_swap_address_space(p->type);
2513 inode = mapping->host;
2514 if (S_ISBLK(inode->i_mode)) {
2515 struct block_device *bdev = I_BDEV(inode);
2517 set_blocksize(bdev, old_block_size);
2518 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2522 inode->i_flags &= ~S_SWAPFILE;
2523 inode_unlock(inode);
2524 filp_close(swap_file, NULL);
2527 * Clear the SWP_USED flag after all resources are freed so that swapon
2528 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
2529 * not hold p->lock after we cleared its SWP_WRITEOK.
2531 spin_lock(&swap_lock);
2533 spin_unlock(&swap_lock);
2536 atomic_inc(&proc_poll_event);
2537 wake_up_interruptible(&proc_poll_wait);
2540 filp_close(victim, NULL);
2546 #ifdef CONFIG_PROC_FS
2547 static __poll_t swaps_poll(struct file *file, poll_table *wait)
2549 struct seq_file *seq = file->private_data;
2551 poll_wait(file, &proc_poll_wait, wait);
2553 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2554 seq->poll_event = atomic_read(&proc_poll_event);
2555 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2558 return EPOLLIN | EPOLLRDNORM;
2562 static void *swap_start(struct seq_file *swap, loff_t *pos)
2564 struct swap_info_struct *si;
2568 mutex_lock(&swapon_mutex);
2571 return SEQ_START_TOKEN;
2573 for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2574 if (!(si->flags & SWP_USED) || !si->swap_map)
2583 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2585 struct swap_info_struct *si = v;
2588 if (v == SEQ_START_TOKEN)
2591 type = si->type + 1;
2594 for (; (si = swap_type_to_swap_info(type)); type++) {
2595 if (!(si->flags & SWP_USED) || !si->swap_map)
2603 static void swap_stop(struct seq_file *swap, void *v)
2605 mutex_unlock(&swapon_mutex);
2608 static int swap_show(struct seq_file *swap, void *v)
2610 struct swap_info_struct *si = v;
2613 unsigned long bytes, inuse;
2615 if (si == SEQ_START_TOKEN) {
2616 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2620 bytes = si->pages << (PAGE_SHIFT - 10);
2621 inuse = si->inuse_pages << (PAGE_SHIFT - 10);
2623 file = si->swap_file;
2624 len = seq_file_path(swap, file, " \t\n\\");
2625 seq_printf(swap, "%*s%s\t%lu\t%s%lu\t%s%d\n",
2626 len < 40 ? 40 - len : 1, " ",
2627 S_ISBLK(file_inode(file)->i_mode) ?
2628 "partition" : "file\t",
2629 bytes, bytes < 10000000 ? "\t" : "",
2630 inuse, inuse < 10000000 ? "\t" : "",
2635 static const struct seq_operations swaps_op = {
2636 .start = swap_start,
2642 static int swaps_open(struct inode *inode, struct file *file)
2644 struct seq_file *seq;
2647 ret = seq_open(file, &swaps_op);
2651 seq = file->private_data;
2652 seq->poll_event = atomic_read(&proc_poll_event);
2656 static const struct proc_ops swaps_proc_ops = {
2657 .proc_flags = PROC_ENTRY_PERMANENT,
2658 .proc_open = swaps_open,
2659 .proc_read = seq_read,
2660 .proc_lseek = seq_lseek,
2661 .proc_release = seq_release,
2662 .proc_poll = swaps_poll,
2665 static int __init procswaps_init(void)
2667 proc_create("swaps", 0, NULL, &swaps_proc_ops);
2670 __initcall(procswaps_init);
2671 #endif /* CONFIG_PROC_FS */
2673 #ifdef MAX_SWAPFILES_CHECK
2674 static int __init max_swapfiles_check(void)
2676 MAX_SWAPFILES_CHECK();
2679 late_initcall(max_swapfiles_check);
2682 static struct swap_info_struct *alloc_swap_info(void)
2684 struct swap_info_struct *p;
2685 struct swap_info_struct *defer = NULL;
2689 p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2691 return ERR_PTR(-ENOMEM);
2693 if (percpu_ref_init(&p->users, swap_users_ref_free,
2694 PERCPU_REF_INIT_DEAD, GFP_KERNEL)) {
2696 return ERR_PTR(-ENOMEM);
2699 spin_lock(&swap_lock);
2700 for (type = 0; type < nr_swapfiles; type++) {
2701 if (!(swap_info[type]->flags & SWP_USED))
2704 if (type >= MAX_SWAPFILES) {
2705 spin_unlock(&swap_lock);
2706 percpu_ref_exit(&p->users);
2708 return ERR_PTR(-EPERM);
2710 if (type >= nr_swapfiles) {
2713 * Publish the swap_info_struct after initializing it.
2714 * Note that kvzalloc() above zeroes all its fields.
2716 smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */
2720 p = swap_info[type];
2722 * Do not memset this entry: a racing procfs swap_next()
2723 * would be relying on p->type to remain valid.
2726 p->swap_extent_root = RB_ROOT;
2727 plist_node_init(&p->list, 0);
2729 plist_node_init(&p->avail_lists[i], 0);
2730 p->flags = SWP_USED;
2731 spin_unlock(&swap_lock);
2733 percpu_ref_exit(&defer->users);
2736 spin_lock_init(&p->lock);
2737 spin_lock_init(&p->cont_lock);
2738 init_completion(&p->comp);
2743 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2747 if (S_ISBLK(inode->i_mode)) {
2748 p->bdev = blkdev_get_by_dev(inode->i_rdev,
2749 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2750 if (IS_ERR(p->bdev)) {
2751 error = PTR_ERR(p->bdev);
2755 p->old_block_size = block_size(p->bdev);
2756 error = set_blocksize(p->bdev, PAGE_SIZE);
2760 * Zoned block devices contain zones that have a sequential
2761 * write only restriction. Hence zoned block devices are not
2762 * suitable for swapping. Disallow them here.
2764 if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
2766 p->flags |= SWP_BLKDEV;
2767 } else if (S_ISREG(inode->i_mode)) {
2768 p->bdev = inode->i_sb->s_bdev;
2776 * Find out how many pages are allowed for a single swap device. There
2777 * are two limiting factors:
2778 * 1) the number of bits for the swap offset in the swp_entry_t type, and
2779 * 2) the number of bits in the swap pte, as defined by the different
2782 * In order to find the largest possible bit mask, a swap entry with
2783 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2784 * decoded to a swp_entry_t again, and finally the swap offset is
2787 * This will mask all the bits from the initial ~0UL mask that can't
2788 * be encoded in either the swp_entry_t or the architecture definition
2791 unsigned long generic_max_swapfile_size(void)
2793 return swp_offset(pte_to_swp_entry(
2794 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2797 /* Can be overridden by an architecture for additional checks. */
2798 __weak unsigned long max_swapfile_size(void)
2800 return generic_max_swapfile_size();
2803 static unsigned long read_swap_header(struct swap_info_struct *p,
2804 union swap_header *swap_header,
2805 struct inode *inode)
2808 unsigned long maxpages;
2809 unsigned long swapfilepages;
2810 unsigned long last_page;
2812 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2813 pr_err("Unable to find swap-space signature\n");
2817 /* swap partition endianness hack... */
2818 if (swab32(swap_header->info.version) == 1) {
2819 swab32s(&swap_header->info.version);
2820 swab32s(&swap_header->info.last_page);
2821 swab32s(&swap_header->info.nr_badpages);
2822 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2824 for (i = 0; i < swap_header->info.nr_badpages; i++)
2825 swab32s(&swap_header->info.badpages[i]);
2827 /* Check the swap header's sub-version */
2828 if (swap_header->info.version != 1) {
2829 pr_warn("Unable to handle swap header version %d\n",
2830 swap_header->info.version);
2835 p->cluster_next = 1;
2838 maxpages = max_swapfile_size();
2839 last_page = swap_header->info.last_page;
2841 pr_warn("Empty swap-file\n");
2844 if (last_page > maxpages) {
2845 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2846 maxpages << (PAGE_SHIFT - 10),
2847 last_page << (PAGE_SHIFT - 10));
2849 if (maxpages > last_page) {
2850 maxpages = last_page + 1;
2851 /* p->max is an unsigned int: don't overflow it */
2852 if ((unsigned int)maxpages == 0)
2853 maxpages = UINT_MAX;
2855 p->highest_bit = maxpages - 1;
2859 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2860 if (swapfilepages && maxpages > swapfilepages) {
2861 pr_warn("Swap area shorter than signature indicates\n");
2864 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2866 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2872 #define SWAP_CLUSTER_INFO_COLS \
2873 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
2874 #define SWAP_CLUSTER_SPACE_COLS \
2875 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
2876 #define SWAP_CLUSTER_COLS \
2877 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
2879 static int setup_swap_map_and_extents(struct swap_info_struct *p,
2880 union swap_header *swap_header,
2881 unsigned char *swap_map,
2882 struct swap_cluster_info *cluster_info,
2883 unsigned long maxpages,
2887 unsigned int nr_good_pages;
2889 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2890 unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
2891 unsigned long i, idx;
2893 nr_good_pages = maxpages - 1; /* omit header page */
2895 cluster_list_init(&p->free_clusters);
2896 cluster_list_init(&p->discard_clusters);
2898 for (i = 0; i < swap_header->info.nr_badpages; i++) {
2899 unsigned int page_nr = swap_header->info.badpages[i];
2900 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2902 if (page_nr < maxpages) {
2903 swap_map[page_nr] = SWAP_MAP_BAD;
2906 * Haven't marked the cluster free yet, no list
2907 * operation involved
2909 inc_cluster_info_page(p, cluster_info, page_nr);
2913 /* Haven't marked the cluster free yet, no list operation involved */
2914 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2915 inc_cluster_info_page(p, cluster_info, i);
2917 if (nr_good_pages) {
2918 swap_map[0] = SWAP_MAP_BAD;
2920 * Not mark the cluster free yet, no list
2921 * operation involved
2923 inc_cluster_info_page(p, cluster_info, 0);
2925 p->pages = nr_good_pages;
2926 nr_extents = setup_swap_extents(p, span);
2929 nr_good_pages = p->pages;
2931 if (!nr_good_pages) {
2932 pr_warn("Empty swap-file\n");
2941 * Reduce false cache line sharing between cluster_info and
2942 * sharing same address space.
2944 for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
2945 j = (k + col) % SWAP_CLUSTER_COLS;
2946 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
2947 idx = i * SWAP_CLUSTER_COLS + j;
2948 if (idx >= nr_clusters)
2950 if (cluster_count(&cluster_info[idx]))
2952 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2953 cluster_list_add_tail(&p->free_clusters, cluster_info,
2961 * Helper to sys_swapon determining if a given swap
2962 * backing device queue supports DISCARD operations.
2964 static bool swap_discardable(struct swap_info_struct *si)
2966 struct request_queue *q = bdev_get_queue(si->bdev);
2968 if (!blk_queue_discard(q))
2974 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2976 struct swap_info_struct *p;
2977 struct filename *name;
2978 struct file *swap_file = NULL;
2979 struct address_space *mapping;
2980 struct dentry *dentry;
2983 union swap_header *swap_header;
2986 unsigned long maxpages;
2987 unsigned char *swap_map = NULL;
2988 struct swap_cluster_info *cluster_info = NULL;
2989 unsigned long *frontswap_map = NULL;
2990 struct page *page = NULL;
2991 struct inode *inode = NULL;
2992 bool inced_nr_rotate_swap = false;
2994 if (swap_flags & ~SWAP_FLAGS_VALID)
2997 if (!capable(CAP_SYS_ADMIN))
3000 if (!swap_avail_heads)
3003 p = alloc_swap_info();
3007 INIT_WORK(&p->discard_work, swap_discard_work);
3009 name = getname(specialfile);
3011 error = PTR_ERR(name);
3015 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3016 if (IS_ERR(swap_file)) {
3017 error = PTR_ERR(swap_file);
3022 p->swap_file = swap_file;
3023 mapping = swap_file->f_mapping;
3024 dentry = swap_file->f_path.dentry;
3025 inode = mapping->host;
3027 error = claim_swapfile(p, inode);
3028 if (unlikely(error))
3032 if (d_unlinked(dentry) || cant_mount(dentry)) {
3034 goto bad_swap_unlock_inode;
3036 if (IS_SWAPFILE(inode)) {
3038 goto bad_swap_unlock_inode;
3042 * Read the swap header.
3044 if (!mapping->a_ops->readpage) {
3046 goto bad_swap_unlock_inode;
3048 page = read_mapping_page(mapping, 0, swap_file);
3050 error = PTR_ERR(page);
3051 goto bad_swap_unlock_inode;
3053 swap_header = kmap(page);
3055 maxpages = read_swap_header(p, swap_header, inode);
3056 if (unlikely(!maxpages)) {
3058 goto bad_swap_unlock_inode;
3061 /* OK, set up the swap map and apply the bad block list */
3062 swap_map = vzalloc(maxpages);
3065 goto bad_swap_unlock_inode;
3068 if (p->bdev && blk_queue_stable_writes(p->bdev->bd_disk->queue))
3069 p->flags |= SWP_STABLE_WRITES;
3071 if (p->bdev && p->bdev->bd_disk->fops->rw_page)
3072 p->flags |= SWP_SYNCHRONOUS_IO;
3074 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
3076 unsigned long ci, nr_cluster;
3078 p->flags |= SWP_SOLIDSTATE;
3079 p->cluster_next_cpu = alloc_percpu(unsigned int);
3080 if (!p->cluster_next_cpu) {
3082 goto bad_swap_unlock_inode;
3085 * select a random position to start with to help wear leveling
3088 for_each_possible_cpu(cpu) {
3089 per_cpu(*p->cluster_next_cpu, cpu) =
3090 1 + prandom_u32_max(p->highest_bit);
3092 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3094 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3096 if (!cluster_info) {
3098 goto bad_swap_unlock_inode;
3101 for (ci = 0; ci < nr_cluster; ci++)
3102 spin_lock_init(&((cluster_info + ci)->lock));
3104 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3105 if (!p->percpu_cluster) {
3107 goto bad_swap_unlock_inode;
3109 for_each_possible_cpu(cpu) {
3110 struct percpu_cluster *cluster;
3111 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3112 cluster_set_null(&cluster->index);
3115 atomic_inc(&nr_rotate_swap);
3116 inced_nr_rotate_swap = true;
3119 error = swap_cgroup_swapon(p->type, maxpages);
3121 goto bad_swap_unlock_inode;
3123 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3124 cluster_info, maxpages, &span);
3125 if (unlikely(nr_extents < 0)) {
3127 goto bad_swap_unlock_inode;
3129 /* frontswap enabled? set up bit-per-page map for frontswap */
3130 if (IS_ENABLED(CONFIG_FRONTSWAP))
3131 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3135 if (p->bdev && (swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
3137 * When discard is enabled for swap with no particular
3138 * policy flagged, we set all swap discard flags here in
3139 * order to sustain backward compatibility with older
3140 * swapon(8) releases.
3142 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3146 * By flagging sys_swapon, a sysadmin can tell us to
3147 * either do single-time area discards only, or to just
3148 * perform discards for released swap page-clusters.
3149 * Now it's time to adjust the p->flags accordingly.
3151 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3152 p->flags &= ~SWP_PAGE_DISCARD;
3153 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3154 p->flags &= ~SWP_AREA_DISCARD;
3156 /* issue a swapon-time discard if it's still required */
3157 if (p->flags & SWP_AREA_DISCARD) {
3158 int err = discard_swap(p);
3160 pr_err("swapon: discard_swap(%p): %d\n",
3165 error = init_swap_address_space(p->type, maxpages);
3167 goto bad_swap_unlock_inode;
3170 * Flush any pending IO and dirty mappings before we start using this
3173 inode->i_flags |= S_SWAPFILE;
3174 error = inode_drain_writes(inode);
3176 inode->i_flags &= ~S_SWAPFILE;
3177 goto free_swap_address_space;
3180 mutex_lock(&swapon_mutex);
3182 if (swap_flags & SWAP_FLAG_PREFER)
3184 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3185 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3187 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3188 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3189 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3190 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3191 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3192 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3193 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3194 (frontswap_map) ? "FS" : "");
3196 mutex_unlock(&swapon_mutex);
3197 atomic_inc(&proc_poll_event);
3198 wake_up_interruptible(&proc_poll_wait);
3202 free_swap_address_space:
3203 exit_swap_address_space(p->type);
3204 bad_swap_unlock_inode:
3205 inode_unlock(inode);
3207 free_percpu(p->percpu_cluster);
3208 p->percpu_cluster = NULL;
3209 free_percpu(p->cluster_next_cpu);
3210 p->cluster_next_cpu = NULL;
3211 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3212 set_blocksize(p->bdev, p->old_block_size);
3213 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3216 destroy_swap_extents(p);
3217 swap_cgroup_swapoff(p->type);
3218 spin_lock(&swap_lock);
3219 p->swap_file = NULL;
3221 spin_unlock(&swap_lock);
3223 kvfree(cluster_info);
3224 kvfree(frontswap_map);
3225 if (inced_nr_rotate_swap)
3226 atomic_dec(&nr_rotate_swap);
3228 filp_close(swap_file, NULL);
3230 if (page && !IS_ERR(page)) {
3237 inode_unlock(inode);
3239 enable_swap_slots_cache();
3243 void si_swapinfo(struct sysinfo *val)
3246 unsigned long nr_to_be_unused = 0;
3248 spin_lock(&swap_lock);
3249 for (type = 0; type < nr_swapfiles; type++) {
3250 struct swap_info_struct *si = swap_info[type];
3252 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3253 nr_to_be_unused += si->inuse_pages;
3255 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3256 val->totalswap = total_swap_pages + nr_to_be_unused;
3257 spin_unlock(&swap_lock);
3261 * Verify that a swap entry is valid and increment its swap map count.
3263 * Returns error code in following case.
3265 * - swp_entry is invalid -> EINVAL
3266 * - swp_entry is migration entry -> EINVAL
3267 * - swap-cache reference is requested but there is already one. -> EEXIST
3268 * - swap-cache reference is requested but the entry is not used. -> ENOENT
3269 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3271 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3273 struct swap_info_struct *p;
3274 struct swap_cluster_info *ci;
3275 unsigned long offset;
3276 unsigned char count;
3277 unsigned char has_cache;
3280 p = get_swap_device(entry);
3284 offset = swp_offset(entry);
3285 ci = lock_cluster_or_swap_info(p, offset);
3287 count = p->swap_map[offset];
3290 * swapin_readahead() doesn't check if a swap entry is valid, so the
3291 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3293 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3298 has_cache = count & SWAP_HAS_CACHE;
3299 count &= ~SWAP_HAS_CACHE;
3302 if (usage == SWAP_HAS_CACHE) {
3304 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3305 if (!has_cache && count)
3306 has_cache = SWAP_HAS_CACHE;
3307 else if (has_cache) /* someone else added cache */
3309 else /* no users remaining */
3312 } else if (count || has_cache) {
3314 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3316 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3318 else if (swap_count_continued(p, offset, count))
3319 count = COUNT_CONTINUED;
3323 err = -ENOENT; /* unused swap entry */
3325 WRITE_ONCE(p->swap_map[offset], count | has_cache);
3328 unlock_cluster_or_swap_info(p, ci);
3335 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3336 * (in which case its reference count is never incremented).
3338 void swap_shmem_alloc(swp_entry_t entry)
3340 __swap_duplicate(entry, SWAP_MAP_SHMEM);
3344 * Increase reference count of swap entry by 1.
3345 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3346 * but could not be atomically allocated. Returns 0, just as if it succeeded,
3347 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3348 * might occur if a page table entry has got corrupted.
3350 int swap_duplicate(swp_entry_t entry)
3354 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3355 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3360 * @entry: swap entry for which we allocate swap cache.
3362 * Called when allocating swap cache for existing swap entry,
3363 * This can return error codes. Returns 0 at success.
3364 * -EEXIST means there is a swap cache.
3365 * Note: return code is different from swap_duplicate().
3367 int swapcache_prepare(swp_entry_t entry)
3369 return __swap_duplicate(entry, SWAP_HAS_CACHE);
3372 struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3374 return swap_type_to_swap_info(swp_type(entry));
3377 struct swap_info_struct *page_swap_info(struct page *page)
3379 swp_entry_t entry = { .val = page_private(page) };
3380 return swp_swap_info(entry);
3384 * out-of-line methods to avoid include hell.
3386 struct address_space *swapcache_mapping(struct folio *folio)
3388 return page_swap_info(&folio->page)->swap_file->f_mapping;
3390 EXPORT_SYMBOL_GPL(swapcache_mapping);
3392 pgoff_t __page_file_index(struct page *page)
3394 swp_entry_t swap = { .val = page_private(page) };
3395 return swp_offset(swap);
3397 EXPORT_SYMBOL_GPL(__page_file_index);
3400 * add_swap_count_continuation - called when a swap count is duplicated
3401 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3402 * page of the original vmalloc'ed swap_map, to hold the continuation count
3403 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
3404 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3406 * These continuation pages are seldom referenced: the common paths all work
3407 * on the original swap_map, only referring to a continuation page when the
3408 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3410 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3411 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3412 * can be called after dropping locks.
3414 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3416 struct swap_info_struct *si;
3417 struct swap_cluster_info *ci;
3420 struct page *list_page;
3422 unsigned char count;
3426 * When debugging, it's easier to use __GFP_ZERO here; but it's better
3427 * for latency not to zero a page while GFP_ATOMIC and holding locks.
3429 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3431 si = get_swap_device(entry);
3434 * An acceptable race has occurred since the failing
3435 * __swap_duplicate(): the swap device may be swapoff
3439 spin_lock(&si->lock);
3441 offset = swp_offset(entry);
3443 ci = lock_cluster(si, offset);
3445 count = swap_count(si->swap_map[offset]);
3447 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3449 * The higher the swap count, the more likely it is that tasks
3450 * will race to add swap count continuation: we need to avoid
3451 * over-provisioning.
3462 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3463 * no architecture is using highmem pages for kernel page tables: so it
3464 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3466 head = vmalloc_to_page(si->swap_map + offset);
3467 offset &= ~PAGE_MASK;
3469 spin_lock(&si->cont_lock);
3471 * Page allocation does not initialize the page's lru field,
3472 * but it does always reset its private field.
3474 if (!page_private(head)) {
3475 BUG_ON(count & COUNT_CONTINUED);
3476 INIT_LIST_HEAD(&head->lru);
3477 set_page_private(head, SWP_CONTINUED);
3478 si->flags |= SWP_CONTINUED;
3481 list_for_each_entry(list_page, &head->lru, lru) {
3485 * If the previous map said no continuation, but we've found
3486 * a continuation page, free our allocation and use this one.
3488 if (!(count & COUNT_CONTINUED))
3489 goto out_unlock_cont;
3491 map = kmap_atomic(list_page) + offset;
3496 * If this continuation count now has some space in it,
3497 * free our allocation and use this one.
3499 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3500 goto out_unlock_cont;
3503 list_add_tail(&page->lru, &head->lru);
3504 page = NULL; /* now it's attached, don't free it */
3506 spin_unlock(&si->cont_lock);
3509 spin_unlock(&si->lock);
3510 put_swap_device(si);
3518 * swap_count_continued - when the original swap_map count is incremented
3519 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3520 * into, carry if so, or else fail until a new continuation page is allocated;
3521 * when the original swap_map count is decremented from 0 with continuation,
3522 * borrow from the continuation and report whether it still holds more.
3523 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3526 static bool swap_count_continued(struct swap_info_struct *si,
3527 pgoff_t offset, unsigned char count)
3534 head = vmalloc_to_page(si->swap_map + offset);
3535 if (page_private(head) != SWP_CONTINUED) {
3536 BUG_ON(count & COUNT_CONTINUED);
3537 return false; /* need to add count continuation */
3540 spin_lock(&si->cont_lock);
3541 offset &= ~PAGE_MASK;
3542 page = list_next_entry(head, lru);
3543 map = kmap_atomic(page) + offset;
3545 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
3546 goto init_map; /* jump over SWAP_CONT_MAX checks */
3548 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3550 * Think of how you add 1 to 999
3552 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3554 page = list_next_entry(page, lru);
3555 BUG_ON(page == head);
3556 map = kmap_atomic(page) + offset;
3558 if (*map == SWAP_CONT_MAX) {
3560 page = list_next_entry(page, lru);
3562 ret = false; /* add count continuation */
3565 map = kmap_atomic(page) + offset;
3566 init_map: *map = 0; /* we didn't zero the page */
3570 while ((page = list_prev_entry(page, lru)) != head) {
3571 map = kmap_atomic(page) + offset;
3572 *map = COUNT_CONTINUED;
3575 ret = true; /* incremented */
3577 } else { /* decrementing */
3579 * Think of how you subtract 1 from 1000
3581 BUG_ON(count != COUNT_CONTINUED);
3582 while (*map == COUNT_CONTINUED) {
3584 page = list_next_entry(page, lru);
3585 BUG_ON(page == head);
3586 map = kmap_atomic(page) + offset;
3593 while ((page = list_prev_entry(page, lru)) != head) {
3594 map = kmap_atomic(page) + offset;
3595 *map = SWAP_CONT_MAX | count;
3596 count = COUNT_CONTINUED;
3599 ret = count == COUNT_CONTINUED;
3602 spin_unlock(&si->cont_lock);
3607 * free_swap_count_continuations - swapoff free all the continuation pages
3608 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3610 static void free_swap_count_continuations(struct swap_info_struct *si)
3614 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3616 head = vmalloc_to_page(si->swap_map + offset);
3617 if (page_private(head)) {
3618 struct page *page, *next;
3620 list_for_each_entry_safe(page, next, &head->lru, lru) {
3621 list_del(&page->lru);
3628 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3629 void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
3631 struct swap_info_struct *si, *next;
3632 int nid = page_to_nid(page);
3634 if (!(gfp_mask & __GFP_IO))
3637 if (!blk_cgroup_congested())
3641 * We've already scheduled a throttle, avoid taking the global swap
3644 if (current->throttle_queue)
3647 spin_lock(&swap_avail_lock);
3648 plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
3651 blkcg_schedule_throttle(bdev_get_queue(si->bdev), true);
3655 spin_unlock(&swap_avail_lock);
3659 static int __init swapfile_init(void)
3663 swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3665 if (!swap_avail_heads) {
3666 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3671 plist_head_init(&swap_avail_heads[nid]);
3675 subsys_initcall(swapfile_init);