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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/swapfile.c
4 *
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie
7 */
8
9#include <linux/mm.h>
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/blkdev.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>
43
44#include <asm/tlbflush.h>
45#include <linux/swapops.h>
46#include <linux/swap_cgroup.h>
47
48static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
49 unsigned char);
50static void free_swap_count_continuations(struct swap_info_struct *);
51
52DEFINE_SPINLOCK(swap_lock);
53static unsigned int nr_swapfiles;
54atomic_long_t nr_swap_pages;
55/*
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.
59 */
60EXPORT_SYMBOL_GPL(nr_swap_pages);
61/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
62long total_swap_pages;
63static int least_priority = -1;
64
65static const char Bad_file[] = "Bad swap file entry ";
66static const char Unused_file[] = "Unused swap file entry ";
67static const char Bad_offset[] = "Bad swap offset entry ";
68static const char Unused_offset[] = "Unused swap offset entry ";
69
70/*
71 * all active swap_info_structs
72 * protected with swap_lock, and ordered by priority.
73 */
74PLIST_HEAD(swap_active_head);
75
76/*
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.
87 */
88static struct plist_head *swap_avail_heads;
89static DEFINE_SPINLOCK(swap_avail_lock);
90
91struct swap_info_struct *swap_info[MAX_SWAPFILES];
92
93static DEFINE_MUTEX(swapon_mutex);
94
95static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
96/* Activity counter to indicate that a swapon or swapoff has occurred */
97static atomic_t proc_poll_event = ATOMIC_INIT(0);
98
99atomic_t nr_rotate_swap = ATOMIC_INIT(0);
100
101static struct swap_info_struct *swap_type_to_swap_info(int type)
102{
103 if (type >= MAX_SWAPFILES)
104 return NULL;
105
106 return READ_ONCE(swap_info[type]); /* rcu_dereference() */
107}
108
109static inline unsigned char swap_count(unsigned char ent)
110{
111 return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
112}
113
114/* Reclaim the swap entry anyway if possible */
115#define TTRS_ANYWAY 0x1
116/*
117 * Reclaim the swap entry if there are no more mappings of the
118 * corresponding page
119 */
120#define TTRS_UNMAPPED 0x2
121/* Reclaim the swap entry if swap is getting full*/
122#define TTRS_FULL 0x4
123
124/* returns 1 if swap entry is freed */
125static int __try_to_reclaim_swap(struct swap_info_struct *si,
126 unsigned long offset, unsigned long flags)
127{
128 swp_entry_t entry = swp_entry(si->type, offset);
129 struct page *page;
130 int ret = 0;
131
132 page = find_get_page(swap_address_space(entry), offset);
133 if (!page)
134 return 0;
135 /*
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.
141 */
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);
147 unlock_page(page);
148 }
149 put_page(page);
150 return ret;
151}
152
153static inline struct swap_extent *first_se(struct swap_info_struct *sis)
154{
155 struct rb_node *rb = rb_first(&sis->swap_extent_root);
156 return rb_entry(rb, struct swap_extent, rb_node);
157}
158
159static inline struct swap_extent *next_se(struct swap_extent *se)
160{
161 struct rb_node *rb = rb_next(&se->rb_node);
162 return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
163}
164
165/*
166 * swapon tell device that all the old swap contents can be discarded,
167 * to allow the swap device to optimize its wear-levelling.
168 */
169static int discard_swap(struct swap_info_struct *si)
170{
171 struct swap_extent *se;
172 sector_t start_block;
173 sector_t nr_blocks;
174 int err = 0;
175
176 /* Do not discard the swap header page! */
177 se = first_se(si);
178 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
179 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
180 if (nr_blocks) {
181 err = blkdev_issue_discard(si->bdev, start_block,
182 nr_blocks, GFP_KERNEL, 0);
183 if (err)
184 return err;
185 cond_resched();
186 }
187
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);
191
192 err = blkdev_issue_discard(si->bdev, start_block,
193 nr_blocks, GFP_KERNEL, 0);
194 if (err)
195 break;
196
197 cond_resched();
198 }
199 return err; /* That will often be -EOPNOTSUPP */
200}
201
202static struct swap_extent *
203offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
204{
205 struct swap_extent *se;
206 struct rb_node *rb;
207
208 rb = sis->swap_extent_root.rb_node;
209 while (rb) {
210 se = rb_entry(rb, struct swap_extent, rb_node);
211 if (offset < se->start_page)
212 rb = rb->rb_left;
213 else if (offset >= se->start_page + se->nr_pages)
214 rb = rb->rb_right;
215 else
216 return se;
217 }
218 /* It *must* be present */
219 BUG();
220}
221
222sector_t swap_page_sector(struct page *page)
223{
224 struct swap_info_struct *sis = page_swap_info(page);
225 struct swap_extent *se;
226 sector_t sector;
227 pgoff_t offset;
228
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);
233}
234
235/*
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.
238 */
239static void discard_swap_cluster(struct swap_info_struct *si,
240 pgoff_t start_page, pgoff_t nr_pages)
241{
242 struct swap_extent *se = offset_to_swap_extent(si, start_page);
243
244 while (nr_pages) {
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;
248
249 if (nr_blocks > nr_pages)
250 nr_blocks = nr_pages;
251 start_page += nr_blocks;
252 nr_pages -= nr_blocks;
253
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))
258 break;
259
260 se = next_se(se);
261 }
262}
263
264#ifdef CONFIG_THP_SWAP
265#define SWAPFILE_CLUSTER HPAGE_PMD_NR
266
267#define swap_entry_size(size) (size)
268#else
269#define SWAPFILE_CLUSTER 256
270
271/*
272 * Define swap_entry_size() as constant to let compiler to optimize
273 * out some code if !CONFIG_THP_SWAP
274 */
275#define swap_entry_size(size) 1
276#endif
277#define LATENCY_LIMIT 256
278
279static inline void cluster_set_flag(struct swap_cluster_info *info,
280 unsigned int flag)
281{
282 info->flags = flag;
283}
284
285static inline unsigned int cluster_count(struct swap_cluster_info *info)
286{
287 return info->data;
288}
289
290static inline void cluster_set_count(struct swap_cluster_info *info,
291 unsigned int c)
292{
293 info->data = c;
294}
295
296static inline void cluster_set_count_flag(struct swap_cluster_info *info,
297 unsigned int c, unsigned int f)
298{
299 info->flags = f;
300 info->data = c;
301}
302
303static inline unsigned int cluster_next(struct swap_cluster_info *info)
304{
305 return info->data;
306}
307
308static inline void cluster_set_next(struct swap_cluster_info *info,
309 unsigned int n)
310{
311 info->data = n;
312}
313
314static inline void cluster_set_next_flag(struct swap_cluster_info *info,
315 unsigned int n, unsigned int f)
316{
317 info->flags = f;
318 info->data = n;
319}
320
321static inline bool cluster_is_free(struct swap_cluster_info *info)
322{
323 return info->flags & CLUSTER_FLAG_FREE;
324}
325
326static inline bool cluster_is_null(struct swap_cluster_info *info)
327{
328 return info->flags & CLUSTER_FLAG_NEXT_NULL;
329}
330
331static inline void cluster_set_null(struct swap_cluster_info *info)
332{
333 info->flags = CLUSTER_FLAG_NEXT_NULL;
334 info->data = 0;
335}
336
337static inline bool cluster_is_huge(struct swap_cluster_info *info)
338{
339 if (IS_ENABLED(CONFIG_THP_SWAP))
340 return info->flags & CLUSTER_FLAG_HUGE;
341 return false;
342}
343
344static inline void cluster_clear_huge(struct swap_cluster_info *info)
345{
346 info->flags &= ~CLUSTER_FLAG_HUGE;
347}
348
349static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
350 unsigned long offset)
351{
352 struct swap_cluster_info *ci;
353
354 ci = si->cluster_info;
355 if (ci) {
356 ci += offset / SWAPFILE_CLUSTER;
357 spin_lock(&ci->lock);
358 }
359 return ci;
360}
361
362static inline void unlock_cluster(struct swap_cluster_info *ci)
363{
364 if (ci)
365 spin_unlock(&ci->lock);
366}
367
368/*
369 * Determine the locking method in use for this device. Return
370 * swap_cluster_info if SSD-style cluster-based locking is in place.
371 */
372static inline struct swap_cluster_info *lock_cluster_or_swap_info(
373 struct swap_info_struct *si, unsigned long offset)
374{
375 struct swap_cluster_info *ci;
376
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: */
380 if (!ci)
381 spin_lock(&si->lock);
382
383 return ci;
384}
385
386static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
387 struct swap_cluster_info *ci)
388{
389 if (ci)
390 unlock_cluster(ci);
391 else
392 spin_unlock(&si->lock);
393}
394
395static inline bool cluster_list_empty(struct swap_cluster_list *list)
396{
397 return cluster_is_null(&list->head);
398}
399
400static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
401{
402 return cluster_next(&list->head);
403}
404
405static void cluster_list_init(struct swap_cluster_list *list)
406{
407 cluster_set_null(&list->head);
408 cluster_set_null(&list->tail);
409}
410
411static void cluster_list_add_tail(struct swap_cluster_list *list,
412 struct swap_cluster_info *ci,
413 unsigned int idx)
414{
415 if (cluster_list_empty(list)) {
416 cluster_set_next_flag(&list->head, idx, 0);
417 cluster_set_next_flag(&list->tail, idx, 0);
418 } else {
419 struct swap_cluster_info *ci_tail;
420 unsigned int tail = cluster_next(&list->tail);
421
422 /*
423 * Nested cluster lock, but both cluster locks are
424 * only acquired when we held swap_info_struct->lock
425 */
426 ci_tail = ci + tail;
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);
431 }
432}
433
434static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
435 struct swap_cluster_info *ci)
436{
437 unsigned int idx;
438
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);
443 } else
444 cluster_set_next_flag(&list->head,
445 cluster_next(&ci[idx]), 0);
446
447 return idx;
448}
449
450/* Add a cluster to discard list and schedule it to do discard */
451static void swap_cluster_schedule_discard(struct swap_info_struct *si,
452 unsigned int idx)
453{
454 /*
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
459 */
460 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
461 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
462
463 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
464
465 schedule_work(&si->discard_work);
466}
467
468static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
469{
470 struct swap_cluster_info *ci = si->cluster_info;
471
472 cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
473 cluster_list_add_tail(&si->free_clusters, ci, idx);
474}
475
476/*
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.
479*/
480static void swap_do_scheduled_discard(struct swap_info_struct *si)
481{
482 struct swap_cluster_info *info, *ci;
483 unsigned int idx;
484
485 info = si->cluster_info;
486
487 while (!cluster_list_empty(&si->discard_clusters)) {
488 idx = cluster_list_del_first(&si->discard_clusters, info);
489 spin_unlock(&si->lock);
490
491 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
492 SWAPFILE_CLUSTER);
493
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);
499 unlock_cluster(ci);
500 }
501}
502
503static void swap_discard_work(struct work_struct *work)
504{
505 struct swap_info_struct *si;
506
507 si = container_of(work, struct swap_info_struct, discard_work);
508
509 spin_lock(&si->lock);
510 swap_do_scheduled_discard(si);
511 spin_unlock(&si->lock);
512}
513
514static void swap_users_ref_free(struct percpu_ref *ref)
515{
516 struct swap_info_struct *si;
517
518 si = container_of(ref, struct swap_info_struct, users);
519 complete(&si->comp);
520}
521
522static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
523{
524 struct swap_cluster_info *ci = si->cluster_info;
525
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);
529}
530
531static void free_cluster(struct swap_info_struct *si, unsigned long idx)
532{
533 struct swap_cluster_info *ci = si->cluster_info + idx;
534
535 VM_BUG_ON(cluster_count(ci) != 0);
536 /*
537 * If the swap is discardable, prepare discard the cluster
538 * instead of free it immediately. The cluster will be freed
539 * after discard.
540 */
541 if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
542 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
543 swap_cluster_schedule_discard(si, idx);
544 return;
545 }
546
547 __free_cluster(si, idx);
548}
549
550/*
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.
553 */
554static void inc_cluster_info_page(struct swap_info_struct *p,
555 struct swap_cluster_info *cluster_info, unsigned long page_nr)
556{
557 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
558
559 if (!cluster_info)
560 return;
561 if (cluster_is_free(&cluster_info[idx]))
562 alloc_cluster(p, idx);
563
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);
567}
568
569/*
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.
573 */
574static void dec_cluster_info_page(struct swap_info_struct *p,
575 struct swap_cluster_info *cluster_info, unsigned long page_nr)
576{
577 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
578
579 if (!cluster_info)
580 return;
581
582 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
583 cluster_set_count(&cluster_info[idx],
584 cluster_count(&cluster_info[idx]) - 1);
585
586 if (cluster_count(&cluster_info[idx]) == 0)
587 free_cluster(p, idx);
588}
589
590/*
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.
593 */
594static bool
595scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
596 unsigned long offset)
597{
598 struct percpu_cluster *percpu_cluster;
599 bool conflict;
600
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]);
605
606 if (!conflict)
607 return false;
608
609 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
610 cluster_set_null(&percpu_cluster->index);
611 return true;
612}
613
614/*
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.
617 */
618static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
619 unsigned long *offset, unsigned long *scan_base)
620{
621 struct percpu_cluster *cluster;
622 struct swap_cluster_info *ci;
623 unsigned long tmp, max;
624
625new_cluster:
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) *
631 SWAPFILE_CLUSTER;
632 } else if (!cluster_list_empty(&si->discard_clusters)) {
633 /*
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
637 */
638 swap_do_scheduled_discard(si);
639 *scan_base = this_cpu_read(*si->cluster_next_cpu);
640 *offset = *scan_base;
641 goto new_cluster;
642 } else
643 return false;
644 }
645
646 /*
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
649 */
650 tmp = cluster->next;
651 max = min_t(unsigned long, si->max,
652 (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
653 if (tmp < max) {
654 ci = lock_cluster(si, tmp);
655 while (tmp < max) {
656 if (!si->swap_map[tmp])
657 break;
658 tmp++;
659 }
660 unlock_cluster(ci);
661 }
662 if (tmp >= max) {
663 cluster_set_null(&cluster->index);
664 goto new_cluster;
665 }
666 cluster->next = tmp + 1;
667 *offset = tmp;
668 *scan_base = tmp;
669 return true;
670}
671
672static void __del_from_avail_list(struct swap_info_struct *p)
673{
674 int nid;
675
676 for_each_node(nid)
677 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
678}
679
680static void del_from_avail_list(struct swap_info_struct *p)
681{
682 spin_lock(&swap_avail_lock);
683 __del_from_avail_list(p);
684 spin_unlock(&swap_avail_lock);
685}
686
687static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
688 unsigned int nr_entries)
689{
690 unsigned int end = offset + nr_entries - 1;
691
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;
699 si->highest_bit = 0;
700 del_from_avail_list(si);
701 }
702}
703
704static void add_to_avail_list(struct swap_info_struct *p)
705{
706 int nid;
707
708 spin_lock(&swap_avail_lock);
709 for_each_node(nid) {
710 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
711 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
712 }
713 spin_unlock(&swap_avail_lock);
714}
715
716static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
717 unsigned int nr_entries)
718{
719 unsigned long begin = offset;
720 unsigned long end = offset + nr_entries - 1;
721 void (*swap_slot_free_notify)(struct block_device *, unsigned long);
722
723 if (offset < si->lowest_bit)
724 si->lowest_bit = offset;
725 if (end > si->highest_bit) {
726 bool was_full = !si->highest_bit;
727
728 WRITE_ONCE(si->highest_bit, end);
729 if (was_full && (si->flags & SWP_WRITEOK))
730 add_to_avail_list(si);
731 }
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;
737 else
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);
744 offset++;
745 }
746 clear_shadow_from_swap_cache(si->type, begin, end);
747}
748
749static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
750{
751 unsigned long prev;
752
753 if (!(si->flags & SWP_SOLIDSTATE)) {
754 si->cluster_next = next;
755 return;
756 }
757
758 prev = this_cpu_read(*si->cluster_next_cpu);
759 /*
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.
763 */
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)
768 return;
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);
773 }
774 this_cpu_write(*si->cluster_next_cpu, next);
775}
776
777static int scan_swap_map_slots(struct swap_info_struct *si,
778 unsigned char usage, int nr,
779 swp_entry_t slots[])
780{
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;
786 int n_ret = 0;
787 bool scanned_many = false;
788
789 /*
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
798 */
799
800 si->flags += SWP_SCANNING;
801 /*
802 * Use percpu scan base for SSD to reduce lock contention on
803 * cluster and swap cache. For HDD, sequential access is more
804 * important.
805 */
806 if (si->flags & SWP_SOLIDSTATE)
807 scan_base = this_cpu_read(*si->cluster_next_cpu);
808 else
809 scan_base = si->cluster_next;
810 offset = scan_base;
811
812 /* SSD algorithm */
813 if (si->cluster_info) {
814 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
815 goto scan;
816 } else if (unlikely(!si->cluster_nr--)) {
817 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
818 si->cluster_nr = SWAPFILE_CLUSTER - 1;
819 goto checks;
820 }
821
822 spin_unlock(&si->lock);
823
824 /*
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.
829 */
830 scan_base = offset = si->lowest_bit;
831 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
832
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;
842 goto checks;
843 }
844 if (unlikely(--latency_ration < 0)) {
845 cond_resched();
846 latency_ration = LATENCY_LIMIT;
847 }
848 }
849
850 offset = scan_base;
851 spin_lock(&si->lock);
852 si->cluster_nr = SWAPFILE_CLUSTER - 1;
853 }
854
855checks:
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 */
859 if (n_ret)
860 goto done;
861 if (!scan_swap_map_try_ssd_cluster(si, &offset,
862 &scan_base))
863 goto scan;
864 }
865 }
866 if (!(si->flags & SWP_WRITEOK))
867 goto no_page;
868 if (!si->highest_bit)
869 goto no_page;
870 if (offset > si->highest_bit)
871 scan_base = offset = si->lowest_bit;
872
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) {
876 int swap_was_freed;
877 unlock_cluster(ci);
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 */
882 if (swap_was_freed)
883 goto checks;
884 goto scan; /* check next one */
885 }
886
887 if (si->swap_map[offset]) {
888 unlock_cluster(ci);
889 if (!n_ret)
890 goto scan;
891 else
892 goto done;
893 }
894 WRITE_ONCE(si->swap_map[offset], usage);
895 inc_cluster_info_page(si, si->cluster_info, offset);
896 unlock_cluster(ci);
897
898 swap_range_alloc(si, offset, 1);
899 slots[n_ret++] = swp_entry(si->type, offset);
900
901 /* got enough slots or reach max slots? */
902 if ((n_ret == nr) || (offset >= si->highest_bit))
903 goto done;
904
905 /* search for next available slot */
906
907 /* time to take a break? */
908 if (unlikely(--latency_ration < 0)) {
909 if (n_ret)
910 goto done;
911 spin_unlock(&si->lock);
912 cond_resched();
913 spin_lock(&si->lock);
914 latency_ration = LATENCY_LIMIT;
915 }
916
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))
920 goto checks;
921 } else if (si->cluster_nr && !si->swap_map[++offset]) {
922 /* non-ssd case, still more slots in cluster? */
923 --si->cluster_nr;
924 goto checks;
925 }
926
927 /*
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.
931 */
932 if (!scanned_many) {
933 unsigned long scan_limit;
934
935 if (offset < scan_base)
936 scan_limit = scan_base;
937 else
938 scan_limit = si->highest_bit;
939 for (; offset <= scan_limit && --latency_ration > 0;
940 offset++) {
941 if (!si->swap_map[offset])
942 goto checks;
943 }
944 }
945
946done:
947 set_cluster_next(si, offset + 1);
948 si->flags -= SWP_SCANNING;
949 return n_ret;
950
951scan:
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);
956 goto checks;
957 }
958 if (vm_swap_full() &&
959 READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
960 spin_lock(&si->lock);
961 goto checks;
962 }
963 if (unlikely(--latency_ration < 0)) {
964 cond_resched();
965 latency_ration = LATENCY_LIMIT;
966 scanned_many = true;
967 }
968 }
969 offset = si->lowest_bit;
970 while (offset < scan_base) {
971 if (data_race(!si->swap_map[offset])) {
972 spin_lock(&si->lock);
973 goto checks;
974 }
975 if (vm_swap_full() &&
976 READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
977 spin_lock(&si->lock);
978 goto checks;
979 }
980 if (unlikely(--latency_ration < 0)) {
981 cond_resched();
982 latency_ration = LATENCY_LIMIT;
983 scanned_many = true;
984 }
985 offset++;
986 }
987 spin_lock(&si->lock);
988
989no_page:
990 si->flags -= SWP_SCANNING;
991 return n_ret;
992}
993
994static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
995{
996 unsigned long idx;
997 struct swap_cluster_info *ci;
998 unsigned long offset;
999
1000 /*
1001 * Should not even be attempting cluster allocations when huge
1002 * page swap is disabled. Warn and fail the allocation.
1003 */
1004 if (!IS_ENABLED(CONFIG_THP_SWAP)) {
1005 VM_WARN_ON_ONCE(1);
1006 return 0;
1007 }
1008
1009 if (cluster_list_empty(&si->free_clusters))
1010 return 0;
1011
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);
1017
1018 memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER);
1019 unlock_cluster(ci);
1020 swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
1021 *slot = swp_entry(si->type, offset);
1022
1023 return 1;
1024}
1025
1026static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
1027{
1028 unsigned long offset = idx * SWAPFILE_CLUSTER;
1029 struct swap_cluster_info *ci;
1030
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);
1035 unlock_cluster(ci);
1036 swap_range_free(si, offset, SWAPFILE_CLUSTER);
1037}
1038
1039int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
1040{
1041 unsigned long size = swap_entry_size(entry_size);
1042 struct swap_info_struct *si, *next;
1043 long avail_pgs;
1044 int n_ret = 0;
1045 int node;
1046
1047 /* Only single cluster request supported */
1048 WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1049
1050 spin_lock(&swap_avail_lock);
1051
1052 avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1053 if (avail_pgs <= 0) {
1054 spin_unlock(&swap_avail_lock);
1055 goto noswap;
1056 }
1057
1058 n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
1059
1060 atomic_long_sub(n_goal * size, &nr_swap_pages);
1061
1062start_over:
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);
1073 goto nextsi;
1074 }
1075 WARN(!si->highest_bit,
1076 "swap_info %d in list but !highest_bit\n",
1077 si->type);
1078 WARN(!(si->flags & SWP_WRITEOK),
1079 "swap_info %d in list but !SWP_WRITEOK\n",
1080 si->type);
1081 __del_from_avail_list(si);
1082 spin_unlock(&si->lock);
1083 goto nextsi;
1084 }
1085 if (size == SWAPFILE_CLUSTER) {
1086 if (si->flags & SWP_BLKDEV)
1087 n_ret = swap_alloc_cluster(si, swp_entries);
1088 } else
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)
1093 goto check_out;
1094 pr_debug("scan_swap_map of si %d failed to find offset\n",
1095 si->type);
1096
1097 spin_lock(&swap_avail_lock);
1098nextsi:
1099 /*
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.
1109 */
1110 if (plist_node_empty(&next->avail_lists[node]))
1111 goto start_over;
1112 }
1113
1114 spin_unlock(&swap_avail_lock);
1115
1116check_out:
1117 if (n_ret < n_goal)
1118 atomic_long_add((long)(n_goal - n_ret) * size,
1119 &nr_swap_pages);
1120noswap:
1121 return n_ret;
1122}
1123
1124static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
1125{
1126 struct swap_info_struct *p;
1127 unsigned long offset;
1128
1129 if (!entry.val)
1130 goto out;
1131 p = swp_swap_info(entry);
1132 if (!p)
1133 goto bad_nofile;
1134 if (data_race(!(p->flags & SWP_USED)))
1135 goto bad_device;
1136 offset = swp_offset(entry);
1137 if (offset >= p->max)
1138 goto bad_offset;
1139 return p;
1140
1141bad_offset:
1142 pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1143 goto out;
1144bad_device:
1145 pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
1146 goto out;
1147bad_nofile:
1148 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1149out:
1150 return NULL;
1151}
1152
1153static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1154{
1155 struct swap_info_struct *p;
1156
1157 p = __swap_info_get(entry);
1158 if (!p)
1159 goto out;
1160 if (data_race(!p->swap_map[swp_offset(entry)]))
1161 goto bad_free;
1162 return p;
1163
1164bad_free:
1165 pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val);
1166out:
1167 return NULL;
1168}
1169
1170static struct swap_info_struct *swap_info_get(swp_entry_t entry)
1171{
1172 struct swap_info_struct *p;
1173
1174 p = _swap_info_get(entry);
1175 if (p)
1176 spin_lock(&p->lock);
1177 return p;
1178}
1179
1180static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1181 struct swap_info_struct *q)
1182{
1183 struct swap_info_struct *p;
1184
1185 p = _swap_info_get(entry);
1186
1187 if (p != q) {
1188 if (q != NULL)
1189 spin_unlock(&q->lock);
1190 if (p != NULL)
1191 spin_lock(&p->lock);
1192 }
1193 return p;
1194}
1195
1196static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1197 unsigned long offset,
1198 unsigned char usage)
1199{
1200 unsigned char count;
1201 unsigned char has_cache;
1202
1203 count = p->swap_map[offset];
1204
1205 has_cache = count & SWAP_HAS_CACHE;
1206 count &= ~SWAP_HAS_CACHE;
1207
1208 if (usage == SWAP_HAS_CACHE) {
1209 VM_BUG_ON(!has_cache);
1210 has_cache = 0;
1211 } else if (count == SWAP_MAP_SHMEM) {
1212 /*
1213 * Or we could insist on shmem.c using a special
1214 * swap_shmem_free() and free_shmem_swap_and_cache()...
1215 */
1216 count = 0;
1217 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1218 if (count == COUNT_CONTINUED) {
1219 if (swap_count_continued(p, offset, count))
1220 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1221 else
1222 count = SWAP_MAP_MAX;
1223 } else
1224 count--;
1225 }
1226
1227 usage = count | has_cache;
1228 if (usage)
1229 WRITE_ONCE(p->swap_map[offset], usage);
1230 else
1231 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
1232
1233 return usage;
1234}
1235
1236/*
1237 * Check whether swap entry is valid in the swap device. If so,
1238 * return pointer to swap_info_struct, and keep the swap entry valid
1239 * via preventing the swap device from being swapoff, until
1240 * put_swap_device() is called. Otherwise return NULL.
1241 *
1242 * Notice that swapoff or swapoff+swapon can still happen before the
1243 * percpu_ref_tryget_live() in get_swap_device() or after the
1244 * percpu_ref_put() in put_swap_device() if there isn't any other way
1245 * to prevent swapoff, such as page lock, page table lock, etc. The
1246 * caller must be prepared for that. For example, the following
1247 * situation is possible.
1248 *
1249 * CPU1 CPU2
1250 * do_swap_page()
1251 * ... swapoff+swapon
1252 * __read_swap_cache_async()
1253 * swapcache_prepare()
1254 * __swap_duplicate()
1255 * // check swap_map
1256 * // verify PTE not changed
1257 *
1258 * In __swap_duplicate(), the swap_map need to be checked before
1259 * changing partly because the specified swap entry may be for another
1260 * swap device which has been swapoff. And in do_swap_page(), after
1261 * the page is read from the swap device, the PTE is verified not
1262 * changed with the page table locked to check whether the swap device
1263 * has been swapoff or swapoff+swapon.
1264 */
1265struct swap_info_struct *get_swap_device(swp_entry_t entry)
1266{
1267 struct swap_info_struct *si;
1268 unsigned long offset;
1269
1270 if (!entry.val)
1271 goto out;
1272 si = swp_swap_info(entry);
1273 if (!si)
1274 goto bad_nofile;
1275 if (!percpu_ref_tryget_live(&si->users))
1276 goto out;
1277 /*
1278 * Guarantee the si->users are checked before accessing other
1279 * fields of swap_info_struct.
1280 *
1281 * Paired with the spin_unlock() after setup_swap_info() in
1282 * enable_swap_info().
1283 */
1284 smp_rmb();
1285 offset = swp_offset(entry);
1286 if (offset >= si->max)
1287 goto put_out;
1288
1289 return si;
1290bad_nofile:
1291 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1292out:
1293 return NULL;
1294put_out:
1295 percpu_ref_put(&si->users);
1296 return NULL;
1297}
1298
1299static unsigned char __swap_entry_free(struct swap_info_struct *p,
1300 swp_entry_t entry)
1301{
1302 struct swap_cluster_info *ci;
1303 unsigned long offset = swp_offset(entry);
1304 unsigned char usage;
1305
1306 ci = lock_cluster_or_swap_info(p, offset);
1307 usage = __swap_entry_free_locked(p, offset, 1);
1308 unlock_cluster_or_swap_info(p, ci);
1309 if (!usage)
1310 free_swap_slot(entry);
1311
1312 return usage;
1313}
1314
1315static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1316{
1317 struct swap_cluster_info *ci;
1318 unsigned long offset = swp_offset(entry);
1319 unsigned char count;
1320
1321 ci = lock_cluster(p, offset);
1322 count = p->swap_map[offset];
1323 VM_BUG_ON(count != SWAP_HAS_CACHE);
1324 p->swap_map[offset] = 0;
1325 dec_cluster_info_page(p, p->cluster_info, offset);
1326 unlock_cluster(ci);
1327
1328 mem_cgroup_uncharge_swap(entry, 1);
1329 swap_range_free(p, offset, 1);
1330}
1331
1332/*
1333 * Caller has made sure that the swap device corresponding to entry
1334 * is still around or has not been recycled.
1335 */
1336void swap_free(swp_entry_t entry)
1337{
1338 struct swap_info_struct *p;
1339
1340 p = _swap_info_get(entry);
1341 if (p)
1342 __swap_entry_free(p, entry);
1343}
1344
1345/*
1346 * Called after dropping swapcache to decrease refcnt to swap entries.
1347 */
1348void put_swap_page(struct page *page, swp_entry_t entry)
1349{
1350 unsigned long offset = swp_offset(entry);
1351 unsigned long idx = offset / SWAPFILE_CLUSTER;
1352 struct swap_cluster_info *ci;
1353 struct swap_info_struct *si;
1354 unsigned char *map;
1355 unsigned int i, free_entries = 0;
1356 unsigned char val;
1357 int size = swap_entry_size(thp_nr_pages(page));
1358
1359 si = _swap_info_get(entry);
1360 if (!si)
1361 return;
1362
1363 ci = lock_cluster_or_swap_info(si, offset);
1364 if (size == SWAPFILE_CLUSTER) {
1365 VM_BUG_ON(!cluster_is_huge(ci));
1366 map = si->swap_map + offset;
1367 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1368 val = map[i];
1369 VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1370 if (val == SWAP_HAS_CACHE)
1371 free_entries++;
1372 }
1373 cluster_clear_huge(ci);
1374 if (free_entries == SWAPFILE_CLUSTER) {
1375 unlock_cluster_or_swap_info(si, ci);
1376 spin_lock(&si->lock);
1377 mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1378 swap_free_cluster(si, idx);
1379 spin_unlock(&si->lock);
1380 return;
1381 }
1382 }
1383 for (i = 0; i < size; i++, entry.val++) {
1384 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1385 unlock_cluster_or_swap_info(si, ci);
1386 free_swap_slot(entry);
1387 if (i == size - 1)
1388 return;
1389 lock_cluster_or_swap_info(si, offset);
1390 }
1391 }
1392 unlock_cluster_or_swap_info(si, ci);
1393}
1394
1395#ifdef CONFIG_THP_SWAP
1396int split_swap_cluster(swp_entry_t entry)
1397{
1398 struct swap_info_struct *si;
1399 struct swap_cluster_info *ci;
1400 unsigned long offset = swp_offset(entry);
1401
1402 si = _swap_info_get(entry);
1403 if (!si)
1404 return -EBUSY;
1405 ci = lock_cluster(si, offset);
1406 cluster_clear_huge(ci);
1407 unlock_cluster(ci);
1408 return 0;
1409}
1410#endif
1411
1412static int swp_entry_cmp(const void *ent1, const void *ent2)
1413{
1414 const swp_entry_t *e1 = ent1, *e2 = ent2;
1415
1416 return (int)swp_type(*e1) - (int)swp_type(*e2);
1417}
1418
1419void swapcache_free_entries(swp_entry_t *entries, int n)
1420{
1421 struct swap_info_struct *p, *prev;
1422 int i;
1423
1424 if (n <= 0)
1425 return;
1426
1427 prev = NULL;
1428 p = NULL;
1429
1430 /*
1431 * Sort swap entries by swap device, so each lock is only taken once.
1432 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1433 * so low that it isn't necessary to optimize further.
1434 */
1435 if (nr_swapfiles > 1)
1436 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1437 for (i = 0; i < n; ++i) {
1438 p = swap_info_get_cont(entries[i], prev);
1439 if (p)
1440 swap_entry_free(p, entries[i]);
1441 prev = p;
1442 }
1443 if (p)
1444 spin_unlock(&p->lock);
1445}
1446
1447/*
1448 * How many references to page 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.
1451 */
1452int page_swapcount(struct page *page)
1453{
1454 int count = 0;
1455 struct swap_info_struct *p;
1456 struct swap_cluster_info *ci;
1457 swp_entry_t entry;
1458 unsigned long offset;
1459
1460 entry.val = page_private(page);
1461 p = _swap_info_get(entry);
1462 if (p) {
1463 offset = swp_offset(entry);
1464 ci = lock_cluster_or_swap_info(p, offset);
1465 count = swap_count(p->swap_map[offset]);
1466 unlock_cluster_or_swap_info(p, ci);
1467 }
1468 return count;
1469}
1470
1471int __swap_count(swp_entry_t entry)
1472{
1473 struct swap_info_struct *si;
1474 pgoff_t offset = swp_offset(entry);
1475 int count = 0;
1476
1477 si = get_swap_device(entry);
1478 if (si) {
1479 count = swap_count(si->swap_map[offset]);
1480 put_swap_device(si);
1481 }
1482 return count;
1483}
1484
1485static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1486{
1487 int count = 0;
1488 pgoff_t offset = swp_offset(entry);
1489 struct swap_cluster_info *ci;
1490
1491 ci = lock_cluster_or_swap_info(si, offset);
1492 count = swap_count(si->swap_map[offset]);
1493 unlock_cluster_or_swap_info(si, ci);
1494 return count;
1495}
1496
1497/*
1498 * How many references to @entry are currently swapped out?
1499 * This does not give an exact answer when swap count is continued,
1500 * but does include the high COUNT_CONTINUED flag to allow for that.
1501 */
1502int __swp_swapcount(swp_entry_t entry)
1503{
1504 int count = 0;
1505 struct swap_info_struct *si;
1506
1507 si = get_swap_device(entry);
1508 if (si) {
1509 count = swap_swapcount(si, entry);
1510 put_swap_device(si);
1511 }
1512 return count;
1513}
1514
1515/*
1516 * How many references to @entry are currently swapped out?
1517 * This considers COUNT_CONTINUED so it returns exact answer.
1518 */
1519int swp_swapcount(swp_entry_t entry)
1520{
1521 int count, tmp_count, n;
1522 struct swap_info_struct *p;
1523 struct swap_cluster_info *ci;
1524 struct page *page;
1525 pgoff_t offset;
1526 unsigned char *map;
1527
1528 p = _swap_info_get(entry);
1529 if (!p)
1530 return 0;
1531
1532 offset = swp_offset(entry);
1533
1534 ci = lock_cluster_or_swap_info(p, offset);
1535
1536 count = swap_count(p->swap_map[offset]);
1537 if (!(count & COUNT_CONTINUED))
1538 goto out;
1539
1540 count &= ~COUNT_CONTINUED;
1541 n = SWAP_MAP_MAX + 1;
1542
1543 page = vmalloc_to_page(p->swap_map + offset);
1544 offset &= ~PAGE_MASK;
1545 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1546
1547 do {
1548 page = list_next_entry(page, lru);
1549 map = kmap_atomic(page);
1550 tmp_count = map[offset];
1551 kunmap_atomic(map);
1552
1553 count += (tmp_count & ~COUNT_CONTINUED) * n;
1554 n *= (SWAP_CONT_MAX + 1);
1555 } while (tmp_count & COUNT_CONTINUED);
1556out:
1557 unlock_cluster_or_swap_info(p, ci);
1558 return count;
1559}
1560
1561static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1562 swp_entry_t entry)
1563{
1564 struct swap_cluster_info *ci;
1565 unsigned char *map = si->swap_map;
1566 unsigned long roffset = swp_offset(entry);
1567 unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1568 int i;
1569 bool ret = false;
1570
1571 ci = lock_cluster_or_swap_info(si, offset);
1572 if (!ci || !cluster_is_huge(ci)) {
1573 if (swap_count(map[roffset]))
1574 ret = true;
1575 goto unlock_out;
1576 }
1577 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1578 if (swap_count(map[offset + i])) {
1579 ret = true;
1580 break;
1581 }
1582 }
1583unlock_out:
1584 unlock_cluster_or_swap_info(si, ci);
1585 return ret;
1586}
1587
1588static bool page_swapped(struct page *page)
1589{
1590 swp_entry_t entry;
1591 struct swap_info_struct *si;
1592
1593 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
1594 return page_swapcount(page) != 0;
1595
1596 page = compound_head(page);
1597 entry.val = page_private(page);
1598 si = _swap_info_get(entry);
1599 if (si)
1600 return swap_page_trans_huge_swapped(si, entry);
1601 return false;
1602}
1603
1604static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
1605 int *total_swapcount)
1606{
1607 int i, map_swapcount, _total_mapcount, _total_swapcount;
1608 unsigned long offset = 0;
1609 struct swap_info_struct *si;
1610 struct swap_cluster_info *ci = NULL;
1611 unsigned char *map = NULL;
1612 int mapcount, swapcount = 0;
1613
1614 /* hugetlbfs shouldn't call it */
1615 VM_BUG_ON_PAGE(PageHuge(page), page);
1616
1617 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {
1618 mapcount = page_trans_huge_mapcount(page, total_mapcount);
1619 if (PageSwapCache(page))
1620 swapcount = page_swapcount(page);
1621 if (total_swapcount)
1622 *total_swapcount = swapcount;
1623 return mapcount + swapcount;
1624 }
1625
1626 page = compound_head(page);
1627
1628 _total_mapcount = _total_swapcount = map_swapcount = 0;
1629 if (PageSwapCache(page)) {
1630 swp_entry_t entry;
1631
1632 entry.val = page_private(page);
1633 si = _swap_info_get(entry);
1634 if (si) {
1635 map = si->swap_map;
1636 offset = swp_offset(entry);
1637 }
1638 }
1639 if (map)
1640 ci = lock_cluster(si, offset);
1641 for (i = 0; i < HPAGE_PMD_NR; i++) {
1642 mapcount = atomic_read(&page[i]._mapcount) + 1;
1643 _total_mapcount += mapcount;
1644 if (map) {
1645 swapcount = swap_count(map[offset + i]);
1646 _total_swapcount += swapcount;
1647 }
1648 map_swapcount = max(map_swapcount, mapcount + swapcount);
1649 }
1650 unlock_cluster(ci);
1651 if (PageDoubleMap(page)) {
1652 map_swapcount -= 1;
1653 _total_mapcount -= HPAGE_PMD_NR;
1654 }
1655 mapcount = compound_mapcount(page);
1656 map_swapcount += mapcount;
1657 _total_mapcount += mapcount;
1658 if (total_mapcount)
1659 *total_mapcount = _total_mapcount;
1660 if (total_swapcount)
1661 *total_swapcount = _total_swapcount;
1662
1663 return map_swapcount;
1664}
1665
1666/*
1667 * We can write to an anon page without COW if there are no other references
1668 * to it. And as a side-effect, free up its swap: because the old content
1669 * on disk will never be read, and seeking back there to write new content
1670 * later would only waste time away from clustering.
1671 *
1672 * NOTE: total_map_swapcount should not be relied upon by the caller if
1673 * reuse_swap_page() returns false, but it may be always overwritten
1674 * (see the other implementation for CONFIG_SWAP=n).
1675 */
1676bool reuse_swap_page(struct page *page, int *total_map_swapcount)
1677{
1678 int count, total_mapcount, total_swapcount;
1679
1680 VM_BUG_ON_PAGE(!PageLocked(page), page);
1681 if (unlikely(PageKsm(page)))
1682 return false;
1683 count = page_trans_huge_map_swapcount(page, &total_mapcount,
1684 &total_swapcount);
1685 if (total_map_swapcount)
1686 *total_map_swapcount = total_mapcount + total_swapcount;
1687 if (count == 1 && PageSwapCache(page) &&
1688 (likely(!PageTransCompound(page)) ||
1689 /* The remaining swap count will be freed soon */
1690 total_swapcount == page_swapcount(page))) {
1691 if (!PageWriteback(page)) {
1692 page = compound_head(page);
1693 delete_from_swap_cache(page);
1694 SetPageDirty(page);
1695 } else {
1696 swp_entry_t entry;
1697 struct swap_info_struct *p;
1698
1699 entry.val = page_private(page);
1700 p = swap_info_get(entry);
1701 if (p->flags & SWP_STABLE_WRITES) {
1702 spin_unlock(&p->lock);
1703 return false;
1704 }
1705 spin_unlock(&p->lock);
1706 }
1707 }
1708
1709 return count <= 1;
1710}
1711
1712/*
1713 * If swap is getting full, or if there are no more mappings of this page,
1714 * then try_to_free_swap is called to free its swap space.
1715 */
1716int try_to_free_swap(struct page *page)
1717{
1718 VM_BUG_ON_PAGE(!PageLocked(page), page);
1719
1720 if (!PageSwapCache(page))
1721 return 0;
1722 if (PageWriteback(page))
1723 return 0;
1724 if (page_swapped(page))
1725 return 0;
1726
1727 /*
1728 * Once hibernation has begun to create its image of memory,
1729 * there's a danger that one of the calls to try_to_free_swap()
1730 * - most probably a call from __try_to_reclaim_swap() while
1731 * hibernation is allocating its own swap pages for the image,
1732 * but conceivably even a call from memory reclaim - will free
1733 * the swap from a page which has already been recorded in the
1734 * image as a clean swapcache page, and then reuse its swap for
1735 * another page of the image. On waking from hibernation, the
1736 * original page might be freed under memory pressure, then
1737 * later read back in from swap, now with the wrong data.
1738 *
1739 * Hibernation suspends storage while it is writing the image
1740 * to disk so check that here.
1741 */
1742 if (pm_suspended_storage())
1743 return 0;
1744
1745 page = compound_head(page);
1746 delete_from_swap_cache(page);
1747 SetPageDirty(page);
1748 return 1;
1749}
1750
1751/*
1752 * Free the swap entry like above, but also try to
1753 * free the page cache entry if it is the last user.
1754 */
1755int free_swap_and_cache(swp_entry_t entry)
1756{
1757 struct swap_info_struct *p;
1758 unsigned char count;
1759
1760 if (non_swap_entry(entry))
1761 return 1;
1762
1763 p = _swap_info_get(entry);
1764 if (p) {
1765 count = __swap_entry_free(p, entry);
1766 if (count == SWAP_HAS_CACHE &&
1767 !swap_page_trans_huge_swapped(p, entry))
1768 __try_to_reclaim_swap(p, swp_offset(entry),
1769 TTRS_UNMAPPED | TTRS_FULL);
1770 }
1771 return p != NULL;
1772}
1773
1774#ifdef CONFIG_HIBERNATION
1775
1776swp_entry_t get_swap_page_of_type(int type)
1777{
1778 struct swap_info_struct *si = swap_type_to_swap_info(type);
1779 swp_entry_t entry = {0};
1780
1781 if (!si)
1782 goto fail;
1783
1784 /* This is called for allocating swap entry, not cache */
1785 spin_lock(&si->lock);
1786 if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
1787 atomic_long_dec(&nr_swap_pages);
1788 spin_unlock(&si->lock);
1789fail:
1790 return entry;
1791}
1792
1793/*
1794 * Find the swap type that corresponds to given device (if any).
1795 *
1796 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1797 * from 0, in which the swap header is expected to be located.
1798 *
1799 * This is needed for the suspend to disk (aka swsusp).
1800 */
1801int swap_type_of(dev_t device, sector_t offset)
1802{
1803 int type;
1804
1805 if (!device)
1806 return -1;
1807
1808 spin_lock(&swap_lock);
1809 for (type = 0; type < nr_swapfiles; type++) {
1810 struct swap_info_struct *sis = swap_info[type];
1811
1812 if (!(sis->flags & SWP_WRITEOK))
1813 continue;
1814
1815 if (device == sis->bdev->bd_dev) {
1816 struct swap_extent *se = first_se(sis);
1817
1818 if (se->start_block == offset) {
1819 spin_unlock(&swap_lock);
1820 return type;
1821 }
1822 }
1823 }
1824 spin_unlock(&swap_lock);
1825 return -ENODEV;
1826}
1827
1828int find_first_swap(dev_t *device)
1829{
1830 int type;
1831
1832 spin_lock(&swap_lock);
1833 for (type = 0; type < nr_swapfiles; type++) {
1834 struct swap_info_struct *sis = swap_info[type];
1835
1836 if (!(sis->flags & SWP_WRITEOK))
1837 continue;
1838 *device = sis->bdev->bd_dev;
1839 spin_unlock(&swap_lock);
1840 return type;
1841 }
1842 spin_unlock(&swap_lock);
1843 return -ENODEV;
1844}
1845
1846/*
1847 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1848 * corresponding to given index in swap_info (swap type).
1849 */
1850sector_t swapdev_block(int type, pgoff_t offset)
1851{
1852 struct swap_info_struct *si = swap_type_to_swap_info(type);
1853 struct swap_extent *se;
1854
1855 if (!si || !(si->flags & SWP_WRITEOK))
1856 return 0;
1857 se = offset_to_swap_extent(si, offset);
1858 return se->start_block + (offset - se->start_page);
1859}
1860
1861/*
1862 * Return either the total number of swap pages of given type, or the number
1863 * of free pages of that type (depending on @free)
1864 *
1865 * This is needed for software suspend
1866 */
1867unsigned int count_swap_pages(int type, int free)
1868{
1869 unsigned int n = 0;
1870
1871 spin_lock(&swap_lock);
1872 if ((unsigned int)type < nr_swapfiles) {
1873 struct swap_info_struct *sis = swap_info[type];
1874
1875 spin_lock(&sis->lock);
1876 if (sis->flags & SWP_WRITEOK) {
1877 n = sis->pages;
1878 if (free)
1879 n -= sis->inuse_pages;
1880 }
1881 spin_unlock(&sis->lock);
1882 }
1883 spin_unlock(&swap_lock);
1884 return n;
1885}
1886#endif /* CONFIG_HIBERNATION */
1887
1888static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1889{
1890 return pte_same(pte_swp_clear_flags(pte), swp_pte);
1891}
1892
1893/*
1894 * No need to decide whether this PTE shares the swap entry with others,
1895 * just let do_wp_page work it out if a write is requested later - to
1896 * force COW, vm_page_prot omits write permission from any private vma.
1897 */
1898static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1899 unsigned long addr, swp_entry_t entry, struct page *page)
1900{
1901 struct page *swapcache;
1902 spinlock_t *ptl;
1903 pte_t *pte;
1904 int ret = 1;
1905
1906 swapcache = page;
1907 page = ksm_might_need_to_copy(page, vma, addr);
1908 if (unlikely(!page))
1909 return -ENOMEM;
1910
1911 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1912 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1913 ret = 0;
1914 goto out;
1915 }
1916
1917 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1918 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1919 get_page(page);
1920 set_pte_at(vma->vm_mm, addr, pte,
1921 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1922 if (page == swapcache) {
1923 page_add_anon_rmap(page, vma, addr, false);
1924 } else { /* ksm created a completely new copy */
1925 page_add_new_anon_rmap(page, vma, addr, false);
1926 lru_cache_add_inactive_or_unevictable(page, vma);
1927 }
1928 swap_free(entry);
1929out:
1930 pte_unmap_unlock(pte, ptl);
1931 if (page != swapcache) {
1932 unlock_page(page);
1933 put_page(page);
1934 }
1935 return ret;
1936}
1937
1938static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1939 unsigned long addr, unsigned long end,
1940 unsigned int type, bool frontswap,
1941 unsigned long *fs_pages_to_unuse)
1942{
1943 struct page *page;
1944 swp_entry_t entry;
1945 pte_t *pte;
1946 struct swap_info_struct *si;
1947 unsigned long offset;
1948 int ret = 0;
1949 volatile unsigned char *swap_map;
1950
1951 si = swap_info[type];
1952 pte = pte_offset_map(pmd, addr);
1953 do {
1954 if (!is_swap_pte(*pte))
1955 continue;
1956
1957 entry = pte_to_swp_entry(*pte);
1958 if (swp_type(entry) != type)
1959 continue;
1960
1961 offset = swp_offset(entry);
1962 if (frontswap && !frontswap_test(si, offset))
1963 continue;
1964
1965 pte_unmap(pte);
1966 swap_map = &si->swap_map[offset];
1967 page = lookup_swap_cache(entry, vma, addr);
1968 if (!page) {
1969 struct vm_fault vmf = {
1970 .vma = vma,
1971 .address = addr,
1972 .pmd = pmd,
1973 };
1974
1975 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
1976 &vmf);
1977 }
1978 if (!page) {
1979 if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1980 goto try_next;
1981 return -ENOMEM;
1982 }
1983
1984 lock_page(page);
1985 wait_on_page_writeback(page);
1986 ret = unuse_pte(vma, pmd, addr, entry, page);
1987 if (ret < 0) {
1988 unlock_page(page);
1989 put_page(page);
1990 goto out;
1991 }
1992
1993 try_to_free_swap(page);
1994 unlock_page(page);
1995 put_page(page);
1996
1997 if (*fs_pages_to_unuse && !--(*fs_pages_to_unuse)) {
1998 ret = FRONTSWAP_PAGES_UNUSED;
1999 goto out;
2000 }
2001try_next:
2002 pte = pte_offset_map(pmd, addr);
2003 } while (pte++, addr += PAGE_SIZE, addr != end);
2004 pte_unmap(pte - 1);
2005
2006 ret = 0;
2007out:
2008 return ret;
2009}
2010
2011static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
2012 unsigned long addr, unsigned long end,
2013 unsigned int type, bool frontswap,
2014 unsigned long *fs_pages_to_unuse)
2015{
2016 pmd_t *pmd;
2017 unsigned long next;
2018 int ret;
2019
2020 pmd = pmd_offset(pud, addr);
2021 do {
2022 cond_resched();
2023 next = pmd_addr_end(addr, end);
2024 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
2025 continue;
2026 ret = unuse_pte_range(vma, pmd, addr, next, type,
2027 frontswap, fs_pages_to_unuse);
2028 if (ret)
2029 return ret;
2030 } while (pmd++, addr = next, addr != end);
2031 return 0;
2032}
2033
2034static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
2035 unsigned long addr, unsigned long end,
2036 unsigned int type, bool frontswap,
2037 unsigned long *fs_pages_to_unuse)
2038{
2039 pud_t *pud;
2040 unsigned long next;
2041 int ret;
2042
2043 pud = pud_offset(p4d, addr);
2044 do {
2045 next = pud_addr_end(addr, end);
2046 if (pud_none_or_clear_bad(pud))
2047 continue;
2048 ret = unuse_pmd_range(vma, pud, addr, next, type,
2049 frontswap, fs_pages_to_unuse);
2050 if (ret)
2051 return ret;
2052 } while (pud++, addr = next, addr != end);
2053 return 0;
2054}
2055
2056static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
2057 unsigned long addr, unsigned long end,
2058 unsigned int type, bool frontswap,
2059 unsigned long *fs_pages_to_unuse)
2060{
2061 p4d_t *p4d;
2062 unsigned long next;
2063 int ret;
2064
2065 p4d = p4d_offset(pgd, addr);
2066 do {
2067 next = p4d_addr_end(addr, end);
2068 if (p4d_none_or_clear_bad(p4d))
2069 continue;
2070 ret = unuse_pud_range(vma, p4d, addr, next, type,
2071 frontswap, fs_pages_to_unuse);
2072 if (ret)
2073 return ret;
2074 } while (p4d++, addr = next, addr != end);
2075 return 0;
2076}
2077
2078static int unuse_vma(struct vm_area_struct *vma, unsigned int type,
2079 bool frontswap, unsigned long *fs_pages_to_unuse)
2080{
2081 pgd_t *pgd;
2082 unsigned long addr, end, next;
2083 int ret;
2084
2085 addr = vma->vm_start;
2086 end = vma->vm_end;
2087
2088 pgd = pgd_offset(vma->vm_mm, addr);
2089 do {
2090 next = pgd_addr_end(addr, end);
2091 if (pgd_none_or_clear_bad(pgd))
2092 continue;
2093 ret = unuse_p4d_range(vma, pgd, addr, next, type,
2094 frontswap, fs_pages_to_unuse);
2095 if (ret)
2096 return ret;
2097 } while (pgd++, addr = next, addr != end);
2098 return 0;
2099}
2100
2101static int unuse_mm(struct mm_struct *mm, unsigned int type,
2102 bool frontswap, unsigned long *fs_pages_to_unuse)
2103{
2104 struct vm_area_struct *vma;
2105 int ret = 0;
2106
2107 mmap_read_lock(mm);
2108 for (vma = mm->mmap; vma; vma = vma->vm_next) {
2109 if (vma->anon_vma) {
2110 ret = unuse_vma(vma, type, frontswap,
2111 fs_pages_to_unuse);
2112 if (ret)
2113 break;
2114 }
2115 cond_resched();
2116 }
2117 mmap_read_unlock(mm);
2118 return ret;
2119}
2120
2121/*
2122 * Scan swap_map (or frontswap_map if frontswap parameter is true)
2123 * from current position to next entry still in use. Return 0
2124 * if there are no inuse entries after prev till end of the map.
2125 */
2126static unsigned int find_next_to_unuse(struct swap_info_struct *si,
2127 unsigned int prev, bool frontswap)
2128{
2129 unsigned int i;
2130 unsigned char count;
2131
2132 /*
2133 * No need for swap_lock here: we're just looking
2134 * for whether an entry is in use, not modifying it; false
2135 * hits are okay, and sys_swapoff() has already prevented new
2136 * allocations from this area (while holding swap_lock).
2137 */
2138 for (i = prev + 1; i < si->max; i++) {
2139 count = READ_ONCE(si->swap_map[i]);
2140 if (count && swap_count(count) != SWAP_MAP_BAD)
2141 if (!frontswap || frontswap_test(si, i))
2142 break;
2143 if ((i % LATENCY_LIMIT) == 0)
2144 cond_resched();
2145 }
2146
2147 if (i == si->max)
2148 i = 0;
2149
2150 return i;
2151}
2152
2153/*
2154 * If the boolean frontswap is true, only unuse pages_to_unuse pages;
2155 * pages_to_unuse==0 means all pages; ignored if frontswap is false
2156 */
2157int try_to_unuse(unsigned int type, bool frontswap,
2158 unsigned long pages_to_unuse)
2159{
2160 struct mm_struct *prev_mm;
2161 struct mm_struct *mm;
2162 struct list_head *p;
2163 int retval = 0;
2164 struct swap_info_struct *si = swap_info[type];
2165 struct page *page;
2166 swp_entry_t entry;
2167 unsigned int i;
2168
2169 if (!READ_ONCE(si->inuse_pages))
2170 return 0;
2171
2172 if (!frontswap)
2173 pages_to_unuse = 0;
2174
2175retry:
2176 retval = shmem_unuse(type, frontswap, &pages_to_unuse);
2177 if (retval)
2178 goto out;
2179
2180 prev_mm = &init_mm;
2181 mmget(prev_mm);
2182
2183 spin_lock(&mmlist_lock);
2184 p = &init_mm.mmlist;
2185 while (READ_ONCE(si->inuse_pages) &&
2186 !signal_pending(current) &&
2187 (p = p->next) != &init_mm.mmlist) {
2188
2189 mm = list_entry(p, struct mm_struct, mmlist);
2190 if (!mmget_not_zero(mm))
2191 continue;
2192 spin_unlock(&mmlist_lock);
2193 mmput(prev_mm);
2194 prev_mm = mm;
2195 retval = unuse_mm(mm, type, frontswap, &pages_to_unuse);
2196
2197 if (retval) {
2198 mmput(prev_mm);
2199 goto out;
2200 }
2201
2202 /*
2203 * Make sure that we aren't completely killing
2204 * interactive performance.
2205 */
2206 cond_resched();
2207 spin_lock(&mmlist_lock);
2208 }
2209 spin_unlock(&mmlist_lock);
2210
2211 mmput(prev_mm);
2212
2213 i = 0;
2214 while (READ_ONCE(si->inuse_pages) &&
2215 !signal_pending(current) &&
2216 (i = find_next_to_unuse(si, i, frontswap)) != 0) {
2217
2218 entry = swp_entry(type, i);
2219 page = find_get_page(swap_address_space(entry), i);
2220 if (!page)
2221 continue;
2222
2223 /*
2224 * It is conceivable that a racing task removed this page from
2225 * swap cache just before we acquired the page lock. The page
2226 * might even be back in swap cache on another swap area. But
2227 * that is okay, try_to_free_swap() only removes stale pages.
2228 */
2229 lock_page(page);
2230 wait_on_page_writeback(page);
2231 try_to_free_swap(page);
2232 unlock_page(page);
2233 put_page(page);
2234
2235 /*
2236 * For frontswap, we just need to unuse pages_to_unuse, if
2237 * it was specified. Need not check frontswap again here as
2238 * we already zeroed out pages_to_unuse if not frontswap.
2239 */
2240 if (pages_to_unuse && --pages_to_unuse == 0)
2241 goto out;
2242 }
2243
2244 /*
2245 * Lets check again to see if there are still swap entries in the map.
2246 * If yes, we would need to do retry the unuse logic again.
2247 * Under global memory pressure, swap entries can be reinserted back
2248 * into process space after the mmlist loop above passes over them.
2249 *
2250 * Limit the number of retries? No: when mmget_not_zero() above fails,
2251 * that mm is likely to be freeing swap from exit_mmap(), which proceeds
2252 * at its own independent pace; and even shmem_writepage() could have
2253 * been preempted after get_swap_page(), temporarily hiding that swap.
2254 * It's easy and robust (though cpu-intensive) just to keep retrying.
2255 */
2256 if (READ_ONCE(si->inuse_pages)) {
2257 if (!signal_pending(current))
2258 goto retry;
2259 retval = -EINTR;
2260 }
2261out:
2262 return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
2263}
2264
2265/*
2266 * After a successful try_to_unuse, if no swap is now in use, we know
2267 * we can empty the mmlist. swap_lock must be held on entry and exit.
2268 * Note that mmlist_lock nests inside swap_lock, and an mm must be
2269 * added to the mmlist just after page_duplicate - before would be racy.
2270 */
2271static void drain_mmlist(void)
2272{
2273 struct list_head *p, *next;
2274 unsigned int type;
2275
2276 for (type = 0; type < nr_swapfiles; type++)
2277 if (swap_info[type]->inuse_pages)
2278 return;
2279 spin_lock(&mmlist_lock);
2280 list_for_each_safe(p, next, &init_mm.mmlist)
2281 list_del_init(p);
2282 spin_unlock(&mmlist_lock);
2283}
2284
2285/*
2286 * Free all of a swapdev's extent information
2287 */
2288static void destroy_swap_extents(struct swap_info_struct *sis)
2289{
2290 while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2291 struct rb_node *rb = sis->swap_extent_root.rb_node;
2292 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2293
2294 rb_erase(rb, &sis->swap_extent_root);
2295 kfree(se);
2296 }
2297
2298 if (sis->flags & SWP_ACTIVATED) {
2299 struct file *swap_file = sis->swap_file;
2300 struct address_space *mapping = swap_file->f_mapping;
2301
2302 sis->flags &= ~SWP_ACTIVATED;
2303 if (mapping->a_ops->swap_deactivate)
2304 mapping->a_ops->swap_deactivate(swap_file);
2305 }
2306}
2307
2308/*
2309 * Add a block range (and the corresponding page range) into this swapdev's
2310 * extent tree.
2311 *
2312 * This function rather assumes that it is called in ascending page order.
2313 */
2314int
2315add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2316 unsigned long nr_pages, sector_t start_block)
2317{
2318 struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2319 struct swap_extent *se;
2320 struct swap_extent *new_se;
2321
2322 /*
2323 * place the new node at the right most since the
2324 * function is called in ascending page order.
2325 */
2326 while (*link) {
2327 parent = *link;
2328 link = &parent->rb_right;
2329 }
2330
2331 if (parent) {
2332 se = rb_entry(parent, struct swap_extent, rb_node);
2333 BUG_ON(se->start_page + se->nr_pages != start_page);
2334 if (se->start_block + se->nr_pages == start_block) {
2335 /* Merge it */
2336 se->nr_pages += nr_pages;
2337 return 0;
2338 }
2339 }
2340
2341 /* No merge, insert a new extent. */
2342 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2343 if (new_se == NULL)
2344 return -ENOMEM;
2345 new_se->start_page = start_page;
2346 new_se->nr_pages = nr_pages;
2347 new_se->start_block = start_block;
2348
2349 rb_link_node(&new_se->rb_node, parent, link);
2350 rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2351 return 1;
2352}
2353EXPORT_SYMBOL_GPL(add_swap_extent);
2354
2355/*
2356 * A `swap extent' is a simple thing which maps a contiguous range of pages
2357 * onto a contiguous range of disk blocks. An ordered list of swap extents
2358 * is built at swapon time and is then used at swap_writepage/swap_readpage
2359 * time for locating where on disk a page belongs.
2360 *
2361 * If the swapfile is an S_ISBLK block device, a single extent is installed.
2362 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2363 * swap files identically.
2364 *
2365 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2366 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
2367 * swapfiles are handled *identically* after swapon time.
2368 *
2369 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2370 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
2371 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
2372 * requirements, they are simply tossed out - we will never use those blocks
2373 * for swapping.
2374 *
2375 * For all swap devices we set S_SWAPFILE across the life of the swapon. This
2376 * prevents users from writing to the swap device, which will corrupt memory.
2377 *
2378 * The amount of disk space which a single swap extent represents varies.
2379 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
2380 * extents in the list. To avoid much list walking, we cache the previous
2381 * search location in `curr_swap_extent', and start new searches from there.
2382 * This is extremely effective. The average number of iterations in
2383 * map_swap_page() has been measured at about 0.3 per page. - akpm.
2384 */
2385static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2386{
2387 struct file *swap_file = sis->swap_file;
2388 struct address_space *mapping = swap_file->f_mapping;
2389 struct inode *inode = mapping->host;
2390 int ret;
2391
2392 if (S_ISBLK(inode->i_mode)) {
2393 ret = add_swap_extent(sis, 0, sis->max, 0);
2394 *span = sis->pages;
2395 return ret;
2396 }
2397
2398 if (mapping->a_ops->swap_activate) {
2399 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2400 if (ret >= 0)
2401 sis->flags |= SWP_ACTIVATED;
2402 if (!ret) {
2403 sis->flags |= SWP_FS_OPS;
2404 ret = add_swap_extent(sis, 0, sis->max, 0);
2405 *span = sis->pages;
2406 }
2407 return ret;
2408 }
2409
2410 return generic_swapfile_activate(sis, swap_file, span);
2411}
2412
2413static int swap_node(struct swap_info_struct *p)
2414{
2415 struct block_device *bdev;
2416
2417 if (p->bdev)
2418 bdev = p->bdev;
2419 else
2420 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2421
2422 return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2423}
2424
2425static void setup_swap_info(struct swap_info_struct *p, int prio,
2426 unsigned char *swap_map,
2427 struct swap_cluster_info *cluster_info)
2428{
2429 int i;
2430
2431 if (prio >= 0)
2432 p->prio = prio;
2433 else
2434 p->prio = --least_priority;
2435 /*
2436 * the plist prio is negated because plist ordering is
2437 * low-to-high, while swap ordering is high-to-low
2438 */
2439 p->list.prio = -p->prio;
2440 for_each_node(i) {
2441 if (p->prio >= 0)
2442 p->avail_lists[i].prio = -p->prio;
2443 else {
2444 if (swap_node(p) == i)
2445 p->avail_lists[i].prio = 1;
2446 else
2447 p->avail_lists[i].prio = -p->prio;
2448 }
2449 }
2450 p->swap_map = swap_map;
2451 p->cluster_info = cluster_info;
2452}
2453
2454static void _enable_swap_info(struct swap_info_struct *p)
2455{
2456 p->flags |= SWP_WRITEOK;
2457 atomic_long_add(p->pages, &nr_swap_pages);
2458 total_swap_pages += p->pages;
2459
2460 assert_spin_locked(&swap_lock);
2461 /*
2462 * both lists are plists, and thus priority ordered.
2463 * swap_active_head needs to be priority ordered for swapoff(),
2464 * which on removal of any swap_info_struct with an auto-assigned
2465 * (i.e. negative) priority increments the auto-assigned priority
2466 * of any lower-priority swap_info_structs.
2467 * swap_avail_head needs to be priority ordered for get_swap_page(),
2468 * which allocates swap pages from the highest available priority
2469 * swap_info_struct.
2470 */
2471 plist_add(&p->list, &swap_active_head);
2472 add_to_avail_list(p);
2473}
2474
2475static void enable_swap_info(struct swap_info_struct *p, int prio,
2476 unsigned char *swap_map,
2477 struct swap_cluster_info *cluster_info,
2478 unsigned long *frontswap_map)
2479{
2480 frontswap_init(p->type, frontswap_map);
2481 spin_lock(&swap_lock);
2482 spin_lock(&p->lock);
2483 setup_swap_info(p, prio, swap_map, cluster_info);
2484 spin_unlock(&p->lock);
2485 spin_unlock(&swap_lock);
2486 /*
2487 * Finished initializing swap device, now it's safe to reference it.
2488 */
2489 percpu_ref_resurrect(&p->users);
2490 spin_lock(&swap_lock);
2491 spin_lock(&p->lock);
2492 _enable_swap_info(p);
2493 spin_unlock(&p->lock);
2494 spin_unlock(&swap_lock);
2495}
2496
2497static void reinsert_swap_info(struct swap_info_struct *p)
2498{
2499 spin_lock(&swap_lock);
2500 spin_lock(&p->lock);
2501 setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2502 _enable_swap_info(p);
2503 spin_unlock(&p->lock);
2504 spin_unlock(&swap_lock);
2505}
2506
2507bool has_usable_swap(void)
2508{
2509 bool ret = true;
2510
2511 spin_lock(&swap_lock);
2512 if (plist_head_empty(&swap_active_head))
2513 ret = false;
2514 spin_unlock(&swap_lock);
2515 return ret;
2516}
2517
2518SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2519{
2520 struct swap_info_struct *p = NULL;
2521 unsigned char *swap_map;
2522 struct swap_cluster_info *cluster_info;
2523 unsigned long *frontswap_map;
2524 struct file *swap_file, *victim;
2525 struct address_space *mapping;
2526 struct inode *inode;
2527 struct filename *pathname;
2528 int err, found = 0;
2529 unsigned int old_block_size;
2530
2531 if (!capable(CAP_SYS_ADMIN))
2532 return -EPERM;
2533
2534 BUG_ON(!current->mm);
2535
2536 pathname = getname(specialfile);
2537 if (IS_ERR(pathname))
2538 return PTR_ERR(pathname);
2539
2540 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2541 err = PTR_ERR(victim);
2542 if (IS_ERR(victim))
2543 goto out;
2544
2545 mapping = victim->f_mapping;
2546 spin_lock(&swap_lock);
2547 plist_for_each_entry(p, &swap_active_head, list) {
2548 if (p->flags & SWP_WRITEOK) {
2549 if (p->swap_file->f_mapping == mapping) {
2550 found = 1;
2551 break;
2552 }
2553 }
2554 }
2555 if (!found) {
2556 err = -EINVAL;
2557 spin_unlock(&swap_lock);
2558 goto out_dput;
2559 }
2560 if (!security_vm_enough_memory_mm(current->mm, p->pages))
2561 vm_unacct_memory(p->pages);
2562 else {
2563 err = -ENOMEM;
2564 spin_unlock(&swap_lock);
2565 goto out_dput;
2566 }
2567 del_from_avail_list(p);
2568 spin_lock(&p->lock);
2569 if (p->prio < 0) {
2570 struct swap_info_struct *si = p;
2571 int nid;
2572
2573 plist_for_each_entry_continue(si, &swap_active_head, list) {
2574 si->prio++;
2575 si->list.prio--;
2576 for_each_node(nid) {
2577 if (si->avail_lists[nid].prio != 1)
2578 si->avail_lists[nid].prio--;
2579 }
2580 }
2581 least_priority++;
2582 }
2583 plist_del(&p->list, &swap_active_head);
2584 atomic_long_sub(p->pages, &nr_swap_pages);
2585 total_swap_pages -= p->pages;
2586 p->flags &= ~SWP_WRITEOK;
2587 spin_unlock(&p->lock);
2588 spin_unlock(&swap_lock);
2589
2590 disable_swap_slots_cache_lock();
2591
2592 set_current_oom_origin();
2593 err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
2594 clear_current_oom_origin();
2595
2596 if (err) {
2597 /* re-insert swap space back into swap_list */
2598 reinsert_swap_info(p);
2599 reenable_swap_slots_cache_unlock();
2600 goto out_dput;
2601 }
2602
2603 reenable_swap_slots_cache_unlock();
2604
2605 /*
2606 * Wait for swap operations protected by get/put_swap_device()
2607 * to complete.
2608 *
2609 * We need synchronize_rcu() here to protect the accessing to
2610 * the swap cache data structure.
2611 */
2612 percpu_ref_kill(&p->users);
2613 synchronize_rcu();
2614 wait_for_completion(&p->comp);
2615
2616 flush_work(&p->discard_work);
2617
2618 destroy_swap_extents(p);
2619 if (p->flags & SWP_CONTINUED)
2620 free_swap_count_continuations(p);
2621
2622 if (!p->bdev || !blk_queue_nonrot(bdev_get_queue(p->bdev)))
2623 atomic_dec(&nr_rotate_swap);
2624
2625 mutex_lock(&swapon_mutex);
2626 spin_lock(&swap_lock);
2627 spin_lock(&p->lock);
2628 drain_mmlist();
2629
2630 /* wait for anyone still in scan_swap_map_slots */
2631 p->highest_bit = 0; /* cuts scans short */
2632 while (p->flags >= SWP_SCANNING) {
2633 spin_unlock(&p->lock);
2634 spin_unlock(&swap_lock);
2635 schedule_timeout_uninterruptible(1);
2636 spin_lock(&swap_lock);
2637 spin_lock(&p->lock);
2638 }
2639
2640 swap_file = p->swap_file;
2641 old_block_size = p->old_block_size;
2642 p->swap_file = NULL;
2643 p->max = 0;
2644 swap_map = p->swap_map;
2645 p->swap_map = NULL;
2646 cluster_info = p->cluster_info;
2647 p->cluster_info = NULL;
2648 frontswap_map = frontswap_map_get(p);
2649 spin_unlock(&p->lock);
2650 spin_unlock(&swap_lock);
2651 arch_swap_invalidate_area(p->type);
2652 frontswap_invalidate_area(p->type);
2653 frontswap_map_set(p, NULL);
2654 mutex_unlock(&swapon_mutex);
2655 free_percpu(p->percpu_cluster);
2656 p->percpu_cluster = NULL;
2657 free_percpu(p->cluster_next_cpu);
2658 p->cluster_next_cpu = NULL;
2659 vfree(swap_map);
2660 kvfree(cluster_info);
2661 kvfree(frontswap_map);
2662 /* Destroy swap account information */
2663 swap_cgroup_swapoff(p->type);
2664 exit_swap_address_space(p->type);
2665
2666 inode = mapping->host;
2667 if (S_ISBLK(inode->i_mode)) {
2668 struct block_device *bdev = I_BDEV(inode);
2669
2670 set_blocksize(bdev, old_block_size);
2671 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2672 }
2673
2674 inode_lock(inode);
2675 inode->i_flags &= ~S_SWAPFILE;
2676 inode_unlock(inode);
2677 filp_close(swap_file, NULL);
2678
2679 /*
2680 * Clear the SWP_USED flag after all resources are freed so that swapon
2681 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
2682 * not hold p->lock after we cleared its SWP_WRITEOK.
2683 */
2684 spin_lock(&swap_lock);
2685 p->flags = 0;
2686 spin_unlock(&swap_lock);
2687
2688 err = 0;
2689 atomic_inc(&proc_poll_event);
2690 wake_up_interruptible(&proc_poll_wait);
2691
2692out_dput:
2693 filp_close(victim, NULL);
2694out:
2695 putname(pathname);
2696 return err;
2697}
2698
2699#ifdef CONFIG_PROC_FS
2700static __poll_t swaps_poll(struct file *file, poll_table *wait)
2701{
2702 struct seq_file *seq = file->private_data;
2703
2704 poll_wait(file, &proc_poll_wait, wait);
2705
2706 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2707 seq->poll_event = atomic_read(&proc_poll_event);
2708 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2709 }
2710
2711 return EPOLLIN | EPOLLRDNORM;
2712}
2713
2714/* iterator */
2715static void *swap_start(struct seq_file *swap, loff_t *pos)
2716{
2717 struct swap_info_struct *si;
2718 int type;
2719 loff_t l = *pos;
2720
2721 mutex_lock(&swapon_mutex);
2722
2723 if (!l)
2724 return SEQ_START_TOKEN;
2725
2726 for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2727 if (!(si->flags & SWP_USED) || !si->swap_map)
2728 continue;
2729 if (!--l)
2730 return si;
2731 }
2732
2733 return NULL;
2734}
2735
2736static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2737{
2738 struct swap_info_struct *si = v;
2739 int type;
2740
2741 if (v == SEQ_START_TOKEN)
2742 type = 0;
2743 else
2744 type = si->type + 1;
2745
2746 ++(*pos);
2747 for (; (si = swap_type_to_swap_info(type)); type++) {
2748 if (!(si->flags & SWP_USED) || !si->swap_map)
2749 continue;
2750 return si;
2751 }
2752
2753 return NULL;
2754}
2755
2756static void swap_stop(struct seq_file *swap, void *v)
2757{
2758 mutex_unlock(&swapon_mutex);
2759}
2760
2761static int swap_show(struct seq_file *swap, void *v)
2762{
2763 struct swap_info_struct *si = v;
2764 struct file *file;
2765 int len;
2766 unsigned int bytes, inuse;
2767
2768 if (si == SEQ_START_TOKEN) {
2769 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2770 return 0;
2771 }
2772
2773 bytes = si->pages << (PAGE_SHIFT - 10);
2774 inuse = si->inuse_pages << (PAGE_SHIFT - 10);
2775
2776 file = si->swap_file;
2777 len = seq_file_path(swap, file, " \t\n\\");
2778 seq_printf(swap, "%*s%s\t%u\t%s%u\t%s%d\n",
2779 len < 40 ? 40 - len : 1, " ",
2780 S_ISBLK(file_inode(file)->i_mode) ?
2781 "partition" : "file\t",
2782 bytes, bytes < 10000000 ? "\t" : "",
2783 inuse, inuse < 10000000 ? "\t" : "",
2784 si->prio);
2785 return 0;
2786}
2787
2788static const struct seq_operations swaps_op = {
2789 .start = swap_start,
2790 .next = swap_next,
2791 .stop = swap_stop,
2792 .show = swap_show
2793};
2794
2795static int swaps_open(struct inode *inode, struct file *file)
2796{
2797 struct seq_file *seq;
2798 int ret;
2799
2800 ret = seq_open(file, &swaps_op);
2801 if (ret)
2802 return ret;
2803
2804 seq = file->private_data;
2805 seq->poll_event = atomic_read(&proc_poll_event);
2806 return 0;
2807}
2808
2809static const struct proc_ops swaps_proc_ops = {
2810 .proc_flags = PROC_ENTRY_PERMANENT,
2811 .proc_open = swaps_open,
2812 .proc_read = seq_read,
2813 .proc_lseek = seq_lseek,
2814 .proc_release = seq_release,
2815 .proc_poll = swaps_poll,
2816};
2817
2818static int __init procswaps_init(void)
2819{
2820 proc_create("swaps", 0, NULL, &swaps_proc_ops);
2821 return 0;
2822}
2823__initcall(procswaps_init);
2824#endif /* CONFIG_PROC_FS */
2825
2826#ifdef MAX_SWAPFILES_CHECK
2827static int __init max_swapfiles_check(void)
2828{
2829 MAX_SWAPFILES_CHECK();
2830 return 0;
2831}
2832late_initcall(max_swapfiles_check);
2833#endif
2834
2835static struct swap_info_struct *alloc_swap_info(void)
2836{
2837 struct swap_info_struct *p;
2838 struct swap_info_struct *defer = NULL;
2839 unsigned int type;
2840 int i;
2841
2842 p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2843 if (!p)
2844 return ERR_PTR(-ENOMEM);
2845
2846 if (percpu_ref_init(&p->users, swap_users_ref_free,
2847 PERCPU_REF_INIT_DEAD, GFP_KERNEL)) {
2848 kvfree(p);
2849 return ERR_PTR(-ENOMEM);
2850 }
2851
2852 spin_lock(&swap_lock);
2853 for (type = 0; type < nr_swapfiles; type++) {
2854 if (!(swap_info[type]->flags & SWP_USED))
2855 break;
2856 }
2857 if (type >= MAX_SWAPFILES) {
2858 spin_unlock(&swap_lock);
2859 percpu_ref_exit(&p->users);
2860 kvfree(p);
2861 return ERR_PTR(-EPERM);
2862 }
2863 if (type >= nr_swapfiles) {
2864 p->type = type;
2865 /*
2866 * Publish the swap_info_struct after initializing it.
2867 * Note that kvzalloc() above zeroes all its fields.
2868 */
2869 smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */
2870 nr_swapfiles++;
2871 } else {
2872 defer = p;
2873 p = swap_info[type];
2874 /*
2875 * Do not memset this entry: a racing procfs swap_next()
2876 * would be relying on p->type to remain valid.
2877 */
2878 }
2879 p->swap_extent_root = RB_ROOT;
2880 plist_node_init(&p->list, 0);
2881 for_each_node(i)
2882 plist_node_init(&p->avail_lists[i], 0);
2883 p->flags = SWP_USED;
2884 spin_unlock(&swap_lock);
2885 if (defer) {
2886 percpu_ref_exit(&defer->users);
2887 kvfree(defer);
2888 }
2889 spin_lock_init(&p->lock);
2890 spin_lock_init(&p->cont_lock);
2891 init_completion(&p->comp);
2892
2893 return p;
2894}
2895
2896static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2897{
2898 int error;
2899
2900 if (S_ISBLK(inode->i_mode)) {
2901 p->bdev = blkdev_get_by_dev(inode->i_rdev,
2902 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2903 if (IS_ERR(p->bdev)) {
2904 error = PTR_ERR(p->bdev);
2905 p->bdev = NULL;
2906 return error;
2907 }
2908 p->old_block_size = block_size(p->bdev);
2909 error = set_blocksize(p->bdev, PAGE_SIZE);
2910 if (error < 0)
2911 return error;
2912 /*
2913 * Zoned block devices contain zones that have a sequential
2914 * write only restriction. Hence zoned block devices are not
2915 * suitable for swapping. Disallow them here.
2916 */
2917 if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
2918 return -EINVAL;
2919 p->flags |= SWP_BLKDEV;
2920 } else if (S_ISREG(inode->i_mode)) {
2921 p->bdev = inode->i_sb->s_bdev;
2922 }
2923
2924 return 0;
2925}
2926
2927
2928/*
2929 * Find out how many pages are allowed for a single swap device. There
2930 * are two limiting factors:
2931 * 1) the number of bits for the swap offset in the swp_entry_t type, and
2932 * 2) the number of bits in the swap pte, as defined by the different
2933 * architectures.
2934 *
2935 * In order to find the largest possible bit mask, a swap entry with
2936 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2937 * decoded to a swp_entry_t again, and finally the swap offset is
2938 * extracted.
2939 *
2940 * This will mask all the bits from the initial ~0UL mask that can't
2941 * be encoded in either the swp_entry_t or the architecture definition
2942 * of a swap pte.
2943 */
2944unsigned long generic_max_swapfile_size(void)
2945{
2946 return swp_offset(pte_to_swp_entry(
2947 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2948}
2949
2950/* Can be overridden by an architecture for additional checks. */
2951__weak unsigned long max_swapfile_size(void)
2952{
2953 return generic_max_swapfile_size();
2954}
2955
2956static unsigned long read_swap_header(struct swap_info_struct *p,
2957 union swap_header *swap_header,
2958 struct inode *inode)
2959{
2960 int i;
2961 unsigned long maxpages;
2962 unsigned long swapfilepages;
2963 unsigned long last_page;
2964
2965 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2966 pr_err("Unable to find swap-space signature\n");
2967 return 0;
2968 }
2969
2970 /* swap partition endianness hack... */
2971 if (swab32(swap_header->info.version) == 1) {
2972 swab32s(&swap_header->info.version);
2973 swab32s(&swap_header->info.last_page);
2974 swab32s(&swap_header->info.nr_badpages);
2975 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2976 return 0;
2977 for (i = 0; i < swap_header->info.nr_badpages; i++)
2978 swab32s(&swap_header->info.badpages[i]);
2979 }
2980 /* Check the swap header's sub-version */
2981 if (swap_header->info.version != 1) {
2982 pr_warn("Unable to handle swap header version %d\n",
2983 swap_header->info.version);
2984 return 0;
2985 }
2986
2987 p->lowest_bit = 1;
2988 p->cluster_next = 1;
2989 p->cluster_nr = 0;
2990
2991 maxpages = max_swapfile_size();
2992 last_page = swap_header->info.last_page;
2993 if (!last_page) {
2994 pr_warn("Empty swap-file\n");
2995 return 0;
2996 }
2997 if (last_page > maxpages) {
2998 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2999 maxpages << (PAGE_SHIFT - 10),
3000 last_page << (PAGE_SHIFT - 10));
3001 }
3002 if (maxpages > last_page) {
3003 maxpages = last_page + 1;
3004 /* p->max is an unsigned int: don't overflow it */
3005 if ((unsigned int)maxpages == 0)
3006 maxpages = UINT_MAX;
3007 }
3008 p->highest_bit = maxpages - 1;
3009
3010 if (!maxpages)
3011 return 0;
3012 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
3013 if (swapfilepages && maxpages > swapfilepages) {
3014 pr_warn("Swap area shorter than signature indicates\n");
3015 return 0;
3016 }
3017 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
3018 return 0;
3019 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
3020 return 0;
3021
3022 return maxpages;
3023}
3024
3025#define SWAP_CLUSTER_INFO_COLS \
3026 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
3027#define SWAP_CLUSTER_SPACE_COLS \
3028 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
3029#define SWAP_CLUSTER_COLS \
3030 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
3031
3032static int setup_swap_map_and_extents(struct swap_info_struct *p,
3033 union swap_header *swap_header,
3034 unsigned char *swap_map,
3035 struct swap_cluster_info *cluster_info,
3036 unsigned long maxpages,
3037 sector_t *span)
3038{
3039 unsigned int j, k;
3040 unsigned int nr_good_pages;
3041 int nr_extents;
3042 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3043 unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
3044 unsigned long i, idx;
3045
3046 nr_good_pages = maxpages - 1; /* omit header page */
3047
3048 cluster_list_init(&p->free_clusters);
3049 cluster_list_init(&p->discard_clusters);
3050
3051 for (i = 0; i < swap_header->info.nr_badpages; i++) {
3052 unsigned int page_nr = swap_header->info.badpages[i];
3053 if (page_nr == 0 || page_nr > swap_header->info.last_page)
3054 return -EINVAL;
3055 if (page_nr < maxpages) {
3056 swap_map[page_nr] = SWAP_MAP_BAD;
3057 nr_good_pages--;
3058 /*
3059 * Haven't marked the cluster free yet, no list
3060 * operation involved
3061 */
3062 inc_cluster_info_page(p, cluster_info, page_nr);
3063 }
3064 }
3065
3066 /* Haven't marked the cluster free yet, no list operation involved */
3067 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
3068 inc_cluster_info_page(p, cluster_info, i);
3069
3070 if (nr_good_pages) {
3071 swap_map[0] = SWAP_MAP_BAD;
3072 /*
3073 * Not mark the cluster free yet, no list
3074 * operation involved
3075 */
3076 inc_cluster_info_page(p, cluster_info, 0);
3077 p->max = maxpages;
3078 p->pages = nr_good_pages;
3079 nr_extents = setup_swap_extents(p, span);
3080 if (nr_extents < 0)
3081 return nr_extents;
3082 nr_good_pages = p->pages;
3083 }
3084 if (!nr_good_pages) {
3085 pr_warn("Empty swap-file\n");
3086 return -EINVAL;
3087 }
3088
3089 if (!cluster_info)
3090 return nr_extents;
3091
3092
3093 /*
3094 * Reduce false cache line sharing between cluster_info and
3095 * sharing same address space.
3096 */
3097 for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
3098 j = (k + col) % SWAP_CLUSTER_COLS;
3099 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
3100 idx = i * SWAP_CLUSTER_COLS + j;
3101 if (idx >= nr_clusters)
3102 continue;
3103 if (cluster_count(&cluster_info[idx]))
3104 continue;
3105 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
3106 cluster_list_add_tail(&p->free_clusters, cluster_info,
3107 idx);
3108 }
3109 }
3110 return nr_extents;
3111}
3112
3113/*
3114 * Helper to sys_swapon determining if a given swap
3115 * backing device queue supports DISCARD operations.
3116 */
3117static bool swap_discardable(struct swap_info_struct *si)
3118{
3119 struct request_queue *q = bdev_get_queue(si->bdev);
3120
3121 if (!q || !blk_queue_discard(q))
3122 return false;
3123
3124 return true;
3125}
3126
3127SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
3128{
3129 struct swap_info_struct *p;
3130 struct filename *name;
3131 struct file *swap_file = NULL;
3132 struct address_space *mapping;
3133 int prio;
3134 int error;
3135 union swap_header *swap_header;
3136 int nr_extents;
3137 sector_t span;
3138 unsigned long maxpages;
3139 unsigned char *swap_map = NULL;
3140 struct swap_cluster_info *cluster_info = NULL;
3141 unsigned long *frontswap_map = NULL;
3142 struct page *page = NULL;
3143 struct inode *inode = NULL;
3144 bool inced_nr_rotate_swap = false;
3145
3146 if (swap_flags & ~SWAP_FLAGS_VALID)
3147 return -EINVAL;
3148
3149 if (!capable(CAP_SYS_ADMIN))
3150 return -EPERM;
3151
3152 if (!swap_avail_heads)
3153 return -ENOMEM;
3154
3155 p = alloc_swap_info();
3156 if (IS_ERR(p))
3157 return PTR_ERR(p);
3158
3159 INIT_WORK(&p->discard_work, swap_discard_work);
3160
3161 name = getname(specialfile);
3162 if (IS_ERR(name)) {
3163 error = PTR_ERR(name);
3164 name = NULL;
3165 goto bad_swap;
3166 }
3167 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3168 if (IS_ERR(swap_file)) {
3169 error = PTR_ERR(swap_file);
3170 swap_file = NULL;
3171 goto bad_swap;
3172 }
3173
3174 p->swap_file = swap_file;
3175 mapping = swap_file->f_mapping;
3176 inode = mapping->host;
3177
3178 error = claim_swapfile(p, inode);
3179 if (unlikely(error))
3180 goto bad_swap;
3181
3182 inode_lock(inode);
3183 if (IS_SWAPFILE(inode)) {
3184 error = -EBUSY;
3185 goto bad_swap_unlock_inode;
3186 }
3187
3188 /*
3189 * Read the swap header.
3190 */
3191 if (!mapping->a_ops->readpage) {
3192 error = -EINVAL;
3193 goto bad_swap_unlock_inode;
3194 }
3195 page = read_mapping_page(mapping, 0, swap_file);
3196 if (IS_ERR(page)) {
3197 error = PTR_ERR(page);
3198 goto bad_swap_unlock_inode;
3199 }
3200 swap_header = kmap(page);
3201
3202 maxpages = read_swap_header(p, swap_header, inode);
3203 if (unlikely(!maxpages)) {
3204 error = -EINVAL;
3205 goto bad_swap_unlock_inode;
3206 }
3207
3208 /* OK, set up the swap map and apply the bad block list */
3209 swap_map = vzalloc(maxpages);
3210 if (!swap_map) {
3211 error = -ENOMEM;
3212 goto bad_swap_unlock_inode;
3213 }
3214
3215 if (p->bdev && blk_queue_stable_writes(p->bdev->bd_disk->queue))
3216 p->flags |= SWP_STABLE_WRITES;
3217
3218 if (p->bdev && p->bdev->bd_disk->fops->rw_page)
3219 p->flags |= SWP_SYNCHRONOUS_IO;
3220
3221 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
3222 int cpu;
3223 unsigned long ci, nr_cluster;
3224
3225 p->flags |= SWP_SOLIDSTATE;
3226 p->cluster_next_cpu = alloc_percpu(unsigned int);
3227 if (!p->cluster_next_cpu) {
3228 error = -ENOMEM;
3229 goto bad_swap_unlock_inode;
3230 }
3231 /*
3232 * select a random position to start with to help wear leveling
3233 * SSD
3234 */
3235 for_each_possible_cpu(cpu) {
3236 per_cpu(*p->cluster_next_cpu, cpu) =
3237 1 + prandom_u32_max(p->highest_bit);
3238 }
3239 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3240
3241 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3242 GFP_KERNEL);
3243 if (!cluster_info) {
3244 error = -ENOMEM;
3245 goto bad_swap_unlock_inode;
3246 }
3247
3248 for (ci = 0; ci < nr_cluster; ci++)
3249 spin_lock_init(&((cluster_info + ci)->lock));
3250
3251 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3252 if (!p->percpu_cluster) {
3253 error = -ENOMEM;
3254 goto bad_swap_unlock_inode;
3255 }
3256 for_each_possible_cpu(cpu) {
3257 struct percpu_cluster *cluster;
3258 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3259 cluster_set_null(&cluster->index);
3260 }
3261 } else {
3262 atomic_inc(&nr_rotate_swap);
3263 inced_nr_rotate_swap = true;
3264 }
3265
3266 error = swap_cgroup_swapon(p->type, maxpages);
3267 if (error)
3268 goto bad_swap_unlock_inode;
3269
3270 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3271 cluster_info, maxpages, &span);
3272 if (unlikely(nr_extents < 0)) {
3273 error = nr_extents;
3274 goto bad_swap_unlock_inode;
3275 }
3276 /* frontswap enabled? set up bit-per-page map for frontswap */
3277 if (IS_ENABLED(CONFIG_FRONTSWAP))
3278 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3279 sizeof(long),
3280 GFP_KERNEL);
3281
3282 if (p->bdev && (swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
3283 /*
3284 * When discard is enabled for swap with no particular
3285 * policy flagged, we set all swap discard flags here in
3286 * order to sustain backward compatibility with older
3287 * swapon(8) releases.
3288 */
3289 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3290 SWP_PAGE_DISCARD);
3291
3292 /*
3293 * By flagging sys_swapon, a sysadmin can tell us to
3294 * either do single-time area discards only, or to just
3295 * perform discards for released swap page-clusters.
3296 * Now it's time to adjust the p->flags accordingly.
3297 */
3298 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3299 p->flags &= ~SWP_PAGE_DISCARD;
3300 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3301 p->flags &= ~SWP_AREA_DISCARD;
3302
3303 /* issue a swapon-time discard if it's still required */
3304 if (p->flags & SWP_AREA_DISCARD) {
3305 int err = discard_swap(p);
3306 if (unlikely(err))
3307 pr_err("swapon: discard_swap(%p): %d\n",
3308 p, err);
3309 }
3310 }
3311
3312 error = init_swap_address_space(p->type, maxpages);
3313 if (error)
3314 goto bad_swap_unlock_inode;
3315
3316 /*
3317 * Flush any pending IO and dirty mappings before we start using this
3318 * swap device.
3319 */
3320 inode->i_flags |= S_SWAPFILE;
3321 error = inode_drain_writes(inode);
3322 if (error) {
3323 inode->i_flags &= ~S_SWAPFILE;
3324 goto free_swap_address_space;
3325 }
3326
3327 mutex_lock(&swapon_mutex);
3328 prio = -1;
3329 if (swap_flags & SWAP_FLAG_PREFER)
3330 prio =
3331 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3332 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3333
3334 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3335 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3336 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3337 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3338 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3339 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3340 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3341 (frontswap_map) ? "FS" : "");
3342
3343 mutex_unlock(&swapon_mutex);
3344 atomic_inc(&proc_poll_event);
3345 wake_up_interruptible(&proc_poll_wait);
3346
3347 error = 0;
3348 goto out;
3349free_swap_address_space:
3350 exit_swap_address_space(p->type);
3351bad_swap_unlock_inode:
3352 inode_unlock(inode);
3353bad_swap:
3354 free_percpu(p->percpu_cluster);
3355 p->percpu_cluster = NULL;
3356 free_percpu(p->cluster_next_cpu);
3357 p->cluster_next_cpu = NULL;
3358 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3359 set_blocksize(p->bdev, p->old_block_size);
3360 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3361 }
3362 inode = NULL;
3363 destroy_swap_extents(p);
3364 swap_cgroup_swapoff(p->type);
3365 spin_lock(&swap_lock);
3366 p->swap_file = NULL;
3367 p->flags = 0;
3368 spin_unlock(&swap_lock);
3369 vfree(swap_map);
3370 kvfree(cluster_info);
3371 kvfree(frontswap_map);
3372 if (inced_nr_rotate_swap)
3373 atomic_dec(&nr_rotate_swap);
3374 if (swap_file)
3375 filp_close(swap_file, NULL);
3376out:
3377 if (page && !IS_ERR(page)) {
3378 kunmap(page);
3379 put_page(page);
3380 }
3381 if (name)
3382 putname(name);
3383 if (inode)
3384 inode_unlock(inode);
3385 if (!error)
3386 enable_swap_slots_cache();
3387 return error;
3388}
3389
3390void si_swapinfo(struct sysinfo *val)
3391{
3392 unsigned int type;
3393 unsigned long nr_to_be_unused = 0;
3394
3395 spin_lock(&swap_lock);
3396 for (type = 0; type < nr_swapfiles; type++) {
3397 struct swap_info_struct *si = swap_info[type];
3398
3399 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3400 nr_to_be_unused += si->inuse_pages;
3401 }
3402 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3403 val->totalswap = total_swap_pages + nr_to_be_unused;
3404 spin_unlock(&swap_lock);
3405}
3406
3407/*
3408 * Verify that a swap entry is valid and increment its swap map count.
3409 *
3410 * Returns error code in following case.
3411 * - success -> 0
3412 * - swp_entry is invalid -> EINVAL
3413 * - swp_entry is migration entry -> EINVAL
3414 * - swap-cache reference is requested but there is already one. -> EEXIST
3415 * - swap-cache reference is requested but the entry is not used. -> ENOENT
3416 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3417 */
3418static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3419{
3420 struct swap_info_struct *p;
3421 struct swap_cluster_info *ci;
3422 unsigned long offset;
3423 unsigned char count;
3424 unsigned char has_cache;
3425 int err;
3426
3427 p = get_swap_device(entry);
3428 if (!p)
3429 return -EINVAL;
3430
3431 offset = swp_offset(entry);
3432 ci = lock_cluster_or_swap_info(p, offset);
3433
3434 count = p->swap_map[offset];
3435
3436 /*
3437 * swapin_readahead() doesn't check if a swap entry is valid, so the
3438 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3439 */
3440 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3441 err = -ENOENT;
3442 goto unlock_out;
3443 }
3444
3445 has_cache = count & SWAP_HAS_CACHE;
3446 count &= ~SWAP_HAS_CACHE;
3447 err = 0;
3448
3449 if (usage == SWAP_HAS_CACHE) {
3450
3451 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3452 if (!has_cache && count)
3453 has_cache = SWAP_HAS_CACHE;
3454 else if (has_cache) /* someone else added cache */
3455 err = -EEXIST;
3456 else /* no users remaining */
3457 err = -ENOENT;
3458
3459 } else if (count || has_cache) {
3460
3461 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3462 count += usage;
3463 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3464 err = -EINVAL;
3465 else if (swap_count_continued(p, offset, count))
3466 count = COUNT_CONTINUED;
3467 else
3468 err = -ENOMEM;
3469 } else
3470 err = -ENOENT; /* unused swap entry */
3471
3472 WRITE_ONCE(p->swap_map[offset], count | has_cache);
3473
3474unlock_out:
3475 unlock_cluster_or_swap_info(p, ci);
3476 if (p)
3477 put_swap_device(p);
3478 return err;
3479}
3480
3481/*
3482 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3483 * (in which case its reference count is never incremented).
3484 */
3485void swap_shmem_alloc(swp_entry_t entry)
3486{
3487 __swap_duplicate(entry, SWAP_MAP_SHMEM);
3488}
3489
3490/*
3491 * Increase reference count of swap entry by 1.
3492 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3493 * but could not be atomically allocated. Returns 0, just as if it succeeded,
3494 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3495 * might occur if a page table entry has got corrupted.
3496 */
3497int swap_duplicate(swp_entry_t entry)
3498{
3499 int err = 0;
3500
3501 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3502 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3503 return err;
3504}
3505
3506/*
3507 * @entry: swap entry for which we allocate swap cache.
3508 *
3509 * Called when allocating swap cache for existing swap entry,
3510 * This can return error codes. Returns 0 at success.
3511 * -EEXIST means there is a swap cache.
3512 * Note: return code is different from swap_duplicate().
3513 */
3514int swapcache_prepare(swp_entry_t entry)
3515{
3516 return __swap_duplicate(entry, SWAP_HAS_CACHE);
3517}
3518
3519struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3520{
3521 return swap_type_to_swap_info(swp_type(entry));
3522}
3523
3524struct swap_info_struct *page_swap_info(struct page *page)
3525{
3526 swp_entry_t entry = { .val = page_private(page) };
3527 return swp_swap_info(entry);
3528}
3529
3530/*
3531 * out-of-line __page_file_ methods to avoid include hell.
3532 */
3533struct address_space *__page_file_mapping(struct page *page)
3534{
3535 return page_swap_info(page)->swap_file->f_mapping;
3536}
3537EXPORT_SYMBOL_GPL(__page_file_mapping);
3538
3539pgoff_t __page_file_index(struct page *page)
3540{
3541 swp_entry_t swap = { .val = page_private(page) };
3542 return swp_offset(swap);
3543}
3544EXPORT_SYMBOL_GPL(__page_file_index);
3545
3546/*
3547 * add_swap_count_continuation - called when a swap count is duplicated
3548 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3549 * page of the original vmalloc'ed swap_map, to hold the continuation count
3550 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
3551 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3552 *
3553 * These continuation pages are seldom referenced: the common paths all work
3554 * on the original swap_map, only referring to a continuation page when the
3555 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3556 *
3557 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3558 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3559 * can be called after dropping locks.
3560 */
3561int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3562{
3563 struct swap_info_struct *si;
3564 struct swap_cluster_info *ci;
3565 struct page *head;
3566 struct page *page;
3567 struct page *list_page;
3568 pgoff_t offset;
3569 unsigned char count;
3570 int ret = 0;
3571
3572 /*
3573 * When debugging, it's easier to use __GFP_ZERO here; but it's better
3574 * for latency not to zero a page while GFP_ATOMIC and holding locks.
3575 */
3576 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3577
3578 si = get_swap_device(entry);
3579 if (!si) {
3580 /*
3581 * An acceptable race has occurred since the failing
3582 * __swap_duplicate(): the swap device may be swapoff
3583 */
3584 goto outer;
3585 }
3586 spin_lock(&si->lock);
3587
3588 offset = swp_offset(entry);
3589
3590 ci = lock_cluster(si, offset);
3591
3592 count = swap_count(si->swap_map[offset]);
3593
3594 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3595 /*
3596 * The higher the swap count, the more likely it is that tasks
3597 * will race to add swap count continuation: we need to avoid
3598 * over-provisioning.
3599 */
3600 goto out;
3601 }
3602
3603 if (!page) {
3604 ret = -ENOMEM;
3605 goto out;
3606 }
3607
3608 /*
3609 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3610 * no architecture is using highmem pages for kernel page tables: so it
3611 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3612 */
3613 head = vmalloc_to_page(si->swap_map + offset);
3614 offset &= ~PAGE_MASK;
3615
3616 spin_lock(&si->cont_lock);
3617 /*
3618 * Page allocation does not initialize the page's lru field,
3619 * but it does always reset its private field.
3620 */
3621 if (!page_private(head)) {
3622 BUG_ON(count & COUNT_CONTINUED);
3623 INIT_LIST_HEAD(&head->lru);
3624 set_page_private(head, SWP_CONTINUED);
3625 si->flags |= SWP_CONTINUED;
3626 }
3627
3628 list_for_each_entry(list_page, &head->lru, lru) {
3629 unsigned char *map;
3630
3631 /*
3632 * If the previous map said no continuation, but we've found
3633 * a continuation page, free our allocation and use this one.
3634 */
3635 if (!(count & COUNT_CONTINUED))
3636 goto out_unlock_cont;
3637
3638 map = kmap_atomic(list_page) + offset;
3639 count = *map;
3640 kunmap_atomic(map);
3641
3642 /*
3643 * If this continuation count now has some space in it,
3644 * free our allocation and use this one.
3645 */
3646 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3647 goto out_unlock_cont;
3648 }
3649
3650 list_add_tail(&page->lru, &head->lru);
3651 page = NULL; /* now it's attached, don't free it */
3652out_unlock_cont:
3653 spin_unlock(&si->cont_lock);
3654out:
3655 unlock_cluster(ci);
3656 spin_unlock(&si->lock);
3657 put_swap_device(si);
3658outer:
3659 if (page)
3660 __free_page(page);
3661 return ret;
3662}
3663
3664/*
3665 * swap_count_continued - when the original swap_map count is incremented
3666 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3667 * into, carry if so, or else fail until a new continuation page is allocated;
3668 * when the original swap_map count is decremented from 0 with continuation,
3669 * borrow from the continuation and report whether it still holds more.
3670 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3671 * lock.
3672 */
3673static bool swap_count_continued(struct swap_info_struct *si,
3674 pgoff_t offset, unsigned char count)
3675{
3676 struct page *head;
3677 struct page *page;
3678 unsigned char *map;
3679 bool ret;
3680
3681 head = vmalloc_to_page(si->swap_map + offset);
3682 if (page_private(head) != SWP_CONTINUED) {
3683 BUG_ON(count & COUNT_CONTINUED);
3684 return false; /* need to add count continuation */
3685 }
3686
3687 spin_lock(&si->cont_lock);
3688 offset &= ~PAGE_MASK;
3689 page = list_next_entry(head, lru);
3690 map = kmap_atomic(page) + offset;
3691
3692 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
3693 goto init_map; /* jump over SWAP_CONT_MAX checks */
3694
3695 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3696 /*
3697 * Think of how you add 1 to 999
3698 */
3699 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3700 kunmap_atomic(map);
3701 page = list_next_entry(page, lru);
3702 BUG_ON(page == head);
3703 map = kmap_atomic(page) + offset;
3704 }
3705 if (*map == SWAP_CONT_MAX) {
3706 kunmap_atomic(map);
3707 page = list_next_entry(page, lru);
3708 if (page == head) {
3709 ret = false; /* add count continuation */
3710 goto out;
3711 }
3712 map = kmap_atomic(page) + offset;
3713init_map: *map = 0; /* we didn't zero the page */
3714 }
3715 *map += 1;
3716 kunmap_atomic(map);
3717 while ((page = list_prev_entry(page, lru)) != head) {
3718 map = kmap_atomic(page) + offset;
3719 *map = COUNT_CONTINUED;
3720 kunmap_atomic(map);
3721 }
3722 ret = true; /* incremented */
3723
3724 } else { /* decrementing */
3725 /*
3726 * Think of how you subtract 1 from 1000
3727 */
3728 BUG_ON(count != COUNT_CONTINUED);
3729 while (*map == COUNT_CONTINUED) {
3730 kunmap_atomic(map);
3731 page = list_next_entry(page, lru);
3732 BUG_ON(page == head);
3733 map = kmap_atomic(page) + offset;
3734 }
3735 BUG_ON(*map == 0);
3736 *map -= 1;
3737 if (*map == 0)
3738 count = 0;
3739 kunmap_atomic(map);
3740 while ((page = list_prev_entry(page, lru)) != head) {
3741 map = kmap_atomic(page) + offset;
3742 *map = SWAP_CONT_MAX | count;
3743 count = COUNT_CONTINUED;
3744 kunmap_atomic(map);
3745 }
3746 ret = count == COUNT_CONTINUED;
3747 }
3748out:
3749 spin_unlock(&si->cont_lock);
3750 return ret;
3751}
3752
3753/*
3754 * free_swap_count_continuations - swapoff free all the continuation pages
3755 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3756 */
3757static void free_swap_count_continuations(struct swap_info_struct *si)
3758{
3759 pgoff_t offset;
3760
3761 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3762 struct page *head;
3763 head = vmalloc_to_page(si->swap_map + offset);
3764 if (page_private(head)) {
3765 struct page *page, *next;
3766
3767 list_for_each_entry_safe(page, next, &head->lru, lru) {
3768 list_del(&page->lru);
3769 __free_page(page);
3770 }
3771 }
3772 }
3773}
3774
3775#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3776void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
3777{
3778 struct swap_info_struct *si, *next;
3779 int nid = page_to_nid(page);
3780
3781 if (!(gfp_mask & __GFP_IO))
3782 return;
3783
3784 if (!blk_cgroup_congested())
3785 return;
3786
3787 /*
3788 * We've already scheduled a throttle, avoid taking the global swap
3789 * lock.
3790 */
3791 if (current->throttle_queue)
3792 return;
3793
3794 spin_lock(&swap_avail_lock);
3795 plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
3796 avail_lists[nid]) {
3797 if (si->bdev) {
3798 blkcg_schedule_throttle(bdev_get_queue(si->bdev), true);
3799 break;
3800 }
3801 }
3802 spin_unlock(&swap_avail_lock);
3803}
3804#endif
3805
3806static int __init swapfile_init(void)
3807{
3808 int nid;
3809
3810 swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3811 GFP_KERNEL);
3812 if (!swap_avail_heads) {
3813 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3814 return -ENOMEM;
3815 }
3816
3817 for_each_node(nid)
3818 plist_head_init(&swap_avail_heads[nid]);
3819
3820 return 0;
3821}
3822subsys_initcall(swapfile_init);
1/*
2 * linux/mm/swapfile.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
6 */
7
8#include <linux/mm.h>
9#include <linux/hugetlb.h>
10#include <linux/mman.h>
11#include <linux/slab.h>
12#include <linux/kernel_stat.h>
13#include <linux/swap.h>
14#include <linux/vmalloc.h>
15#include <linux/pagemap.h>
16#include <linux/namei.h>
17#include <linux/shmem_fs.h>
18#include <linux/blkdev.h>
19#include <linux/random.h>
20#include <linux/writeback.h>
21#include <linux/proc_fs.h>
22#include <linux/seq_file.h>
23#include <linux/init.h>
24#include <linux/ksm.h>
25#include <linux/rmap.h>
26#include <linux/security.h>
27#include <linux/backing-dev.h>
28#include <linux/mutex.h>
29#include <linux/capability.h>
30#include <linux/syscalls.h>
31#include <linux/memcontrol.h>
32#include <linux/poll.h>
33#include <linux/oom.h>
34#include <linux/frontswap.h>
35#include <linux/swapfile.h>
36#include <linux/export.h>
37
38#include <asm/pgtable.h>
39#include <asm/tlbflush.h>
40#include <linux/swapops.h>
41#include <linux/swap_cgroup.h>
42
43static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
44 unsigned char);
45static void free_swap_count_continuations(struct swap_info_struct *);
46static sector_t map_swap_entry(swp_entry_t, struct block_device**);
47
48DEFINE_SPINLOCK(swap_lock);
49static unsigned int nr_swapfiles;
50atomic_long_t nr_swap_pages;
51/*
52 * Some modules use swappable objects and may try to swap them out under
53 * memory pressure (via the shrinker). Before doing so, they may wish to
54 * check to see if any swap space is available.
55 */
56EXPORT_SYMBOL_GPL(nr_swap_pages);
57/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
58long total_swap_pages;
59static int least_priority;
60
61static const char Bad_file[] = "Bad swap file entry ";
62static const char Unused_file[] = "Unused swap file entry ";
63static const char Bad_offset[] = "Bad swap offset entry ";
64static const char Unused_offset[] = "Unused swap offset entry ";
65
66/*
67 * all active swap_info_structs
68 * protected with swap_lock, and ordered by priority.
69 */
70PLIST_HEAD(swap_active_head);
71
72/*
73 * all available (active, not full) swap_info_structs
74 * protected with swap_avail_lock, ordered by priority.
75 * This is used by get_swap_page() instead of swap_active_head
76 * because swap_active_head includes all swap_info_structs,
77 * but get_swap_page() doesn't need to look at full ones.
78 * This uses its own lock instead of swap_lock because when a
79 * swap_info_struct changes between not-full/full, it needs to
80 * add/remove itself to/from this list, but the swap_info_struct->lock
81 * is held and the locking order requires swap_lock to be taken
82 * before any swap_info_struct->lock.
83 */
84static PLIST_HEAD(swap_avail_head);
85static DEFINE_SPINLOCK(swap_avail_lock);
86
87struct swap_info_struct *swap_info[MAX_SWAPFILES];
88
89static DEFINE_MUTEX(swapon_mutex);
90
91static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
92/* Activity counter to indicate that a swapon or swapoff has occurred */
93static atomic_t proc_poll_event = ATOMIC_INIT(0);
94
95static inline unsigned char swap_count(unsigned char ent)
96{
97 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
98}
99
100/* returns 1 if swap entry is freed */
101static int
102__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
103{
104 swp_entry_t entry = swp_entry(si->type, offset);
105 struct page *page;
106 int ret = 0;
107
108 page = find_get_page(swap_address_space(entry), swp_offset(entry));
109 if (!page)
110 return 0;
111 /*
112 * This function is called from scan_swap_map() and it's called
113 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
114 * We have to use trylock for avoiding deadlock. This is a special
115 * case and you should use try_to_free_swap() with explicit lock_page()
116 * in usual operations.
117 */
118 if (trylock_page(page)) {
119 ret = try_to_free_swap(page);
120 unlock_page(page);
121 }
122 put_page(page);
123 return ret;
124}
125
126/*
127 * swapon tell device that all the old swap contents can be discarded,
128 * to allow the swap device to optimize its wear-levelling.
129 */
130static int discard_swap(struct swap_info_struct *si)
131{
132 struct swap_extent *se;
133 sector_t start_block;
134 sector_t nr_blocks;
135 int err = 0;
136
137 /* Do not discard the swap header page! */
138 se = &si->first_swap_extent;
139 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
140 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
141 if (nr_blocks) {
142 err = blkdev_issue_discard(si->bdev, start_block,
143 nr_blocks, GFP_KERNEL, 0);
144 if (err)
145 return err;
146 cond_resched();
147 }
148
149 list_for_each_entry(se, &si->first_swap_extent.list, list) {
150 start_block = se->start_block << (PAGE_SHIFT - 9);
151 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
152
153 err = blkdev_issue_discard(si->bdev, start_block,
154 nr_blocks, GFP_KERNEL, 0);
155 if (err)
156 break;
157
158 cond_resched();
159 }
160 return err; /* That will often be -EOPNOTSUPP */
161}
162
163/*
164 * swap allocation tell device that a cluster of swap can now be discarded,
165 * to allow the swap device to optimize its wear-levelling.
166 */
167static void discard_swap_cluster(struct swap_info_struct *si,
168 pgoff_t start_page, pgoff_t nr_pages)
169{
170 struct swap_extent *se = si->curr_swap_extent;
171 int found_extent = 0;
172
173 while (nr_pages) {
174 if (se->start_page <= start_page &&
175 start_page < se->start_page + se->nr_pages) {
176 pgoff_t offset = start_page - se->start_page;
177 sector_t start_block = se->start_block + offset;
178 sector_t nr_blocks = se->nr_pages - offset;
179
180 if (nr_blocks > nr_pages)
181 nr_blocks = nr_pages;
182 start_page += nr_blocks;
183 nr_pages -= nr_blocks;
184
185 if (!found_extent++)
186 si->curr_swap_extent = se;
187
188 start_block <<= PAGE_SHIFT - 9;
189 nr_blocks <<= PAGE_SHIFT - 9;
190 if (blkdev_issue_discard(si->bdev, start_block,
191 nr_blocks, GFP_NOIO, 0))
192 break;
193 }
194
195 se = list_next_entry(se, list);
196 }
197}
198
199#define SWAPFILE_CLUSTER 256
200#define LATENCY_LIMIT 256
201
202static inline void cluster_set_flag(struct swap_cluster_info *info,
203 unsigned int flag)
204{
205 info->flags = flag;
206}
207
208static inline unsigned int cluster_count(struct swap_cluster_info *info)
209{
210 return info->data;
211}
212
213static inline void cluster_set_count(struct swap_cluster_info *info,
214 unsigned int c)
215{
216 info->data = c;
217}
218
219static inline void cluster_set_count_flag(struct swap_cluster_info *info,
220 unsigned int c, unsigned int f)
221{
222 info->flags = f;
223 info->data = c;
224}
225
226static inline unsigned int cluster_next(struct swap_cluster_info *info)
227{
228 return info->data;
229}
230
231static inline void cluster_set_next(struct swap_cluster_info *info,
232 unsigned int n)
233{
234 info->data = n;
235}
236
237static inline void cluster_set_next_flag(struct swap_cluster_info *info,
238 unsigned int n, unsigned int f)
239{
240 info->flags = f;
241 info->data = n;
242}
243
244static inline bool cluster_is_free(struct swap_cluster_info *info)
245{
246 return info->flags & CLUSTER_FLAG_FREE;
247}
248
249static inline bool cluster_is_null(struct swap_cluster_info *info)
250{
251 return info->flags & CLUSTER_FLAG_NEXT_NULL;
252}
253
254static inline void cluster_set_null(struct swap_cluster_info *info)
255{
256 info->flags = CLUSTER_FLAG_NEXT_NULL;
257 info->data = 0;
258}
259
260static inline bool cluster_list_empty(struct swap_cluster_list *list)
261{
262 return cluster_is_null(&list->head);
263}
264
265static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
266{
267 return cluster_next(&list->head);
268}
269
270static void cluster_list_init(struct swap_cluster_list *list)
271{
272 cluster_set_null(&list->head);
273 cluster_set_null(&list->tail);
274}
275
276static void cluster_list_add_tail(struct swap_cluster_list *list,
277 struct swap_cluster_info *ci,
278 unsigned int idx)
279{
280 if (cluster_list_empty(list)) {
281 cluster_set_next_flag(&list->head, idx, 0);
282 cluster_set_next_flag(&list->tail, idx, 0);
283 } else {
284 unsigned int tail = cluster_next(&list->tail);
285
286 cluster_set_next(&ci[tail], idx);
287 cluster_set_next_flag(&list->tail, idx, 0);
288 }
289}
290
291static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
292 struct swap_cluster_info *ci)
293{
294 unsigned int idx;
295
296 idx = cluster_next(&list->head);
297 if (cluster_next(&list->tail) == idx) {
298 cluster_set_null(&list->head);
299 cluster_set_null(&list->tail);
300 } else
301 cluster_set_next_flag(&list->head,
302 cluster_next(&ci[idx]), 0);
303
304 return idx;
305}
306
307/* Add a cluster to discard list and schedule it to do discard */
308static void swap_cluster_schedule_discard(struct swap_info_struct *si,
309 unsigned int idx)
310{
311 /*
312 * If scan_swap_map() can't find a free cluster, it will check
313 * si->swap_map directly. To make sure the discarding cluster isn't
314 * taken by scan_swap_map(), mark the swap entries bad (occupied). It
315 * will be cleared after discard
316 */
317 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
318 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
319
320 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
321
322 schedule_work(&si->discard_work);
323}
324
325/*
326 * Doing discard actually. After a cluster discard is finished, the cluster
327 * will be added to free cluster list. caller should hold si->lock.
328*/
329static void swap_do_scheduled_discard(struct swap_info_struct *si)
330{
331 struct swap_cluster_info *info;
332 unsigned int idx;
333
334 info = si->cluster_info;
335
336 while (!cluster_list_empty(&si->discard_clusters)) {
337 idx = cluster_list_del_first(&si->discard_clusters, info);
338 spin_unlock(&si->lock);
339
340 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
341 SWAPFILE_CLUSTER);
342
343 spin_lock(&si->lock);
344 cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
345 cluster_list_add_tail(&si->free_clusters, info, idx);
346 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
347 0, SWAPFILE_CLUSTER);
348 }
349}
350
351static void swap_discard_work(struct work_struct *work)
352{
353 struct swap_info_struct *si;
354
355 si = container_of(work, struct swap_info_struct, discard_work);
356
357 spin_lock(&si->lock);
358 swap_do_scheduled_discard(si);
359 spin_unlock(&si->lock);
360}
361
362/*
363 * The cluster corresponding to page_nr will be used. The cluster will be
364 * removed from free cluster list and its usage counter will be increased.
365 */
366static void inc_cluster_info_page(struct swap_info_struct *p,
367 struct swap_cluster_info *cluster_info, unsigned long page_nr)
368{
369 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
370
371 if (!cluster_info)
372 return;
373 if (cluster_is_free(&cluster_info[idx])) {
374 VM_BUG_ON(cluster_list_first(&p->free_clusters) != idx);
375 cluster_list_del_first(&p->free_clusters, cluster_info);
376 cluster_set_count_flag(&cluster_info[idx], 0, 0);
377 }
378
379 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
380 cluster_set_count(&cluster_info[idx],
381 cluster_count(&cluster_info[idx]) + 1);
382}
383
384/*
385 * The cluster corresponding to page_nr decreases one usage. If the usage
386 * counter becomes 0, which means no page in the cluster is in using, we can
387 * optionally discard the cluster and add it to free cluster list.
388 */
389static void dec_cluster_info_page(struct swap_info_struct *p,
390 struct swap_cluster_info *cluster_info, unsigned long page_nr)
391{
392 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
393
394 if (!cluster_info)
395 return;
396
397 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
398 cluster_set_count(&cluster_info[idx],
399 cluster_count(&cluster_info[idx]) - 1);
400
401 if (cluster_count(&cluster_info[idx]) == 0) {
402 /*
403 * If the swap is discardable, prepare discard the cluster
404 * instead of free it immediately. The cluster will be freed
405 * after discard.
406 */
407 if ((p->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
408 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
409 swap_cluster_schedule_discard(p, idx);
410 return;
411 }
412
413 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
414 cluster_list_add_tail(&p->free_clusters, cluster_info, idx);
415 }
416}
417
418/*
419 * It's possible scan_swap_map() uses a free cluster in the middle of free
420 * cluster list. Avoiding such abuse to avoid list corruption.
421 */
422static bool
423scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
424 unsigned long offset)
425{
426 struct percpu_cluster *percpu_cluster;
427 bool conflict;
428
429 offset /= SWAPFILE_CLUSTER;
430 conflict = !cluster_list_empty(&si->free_clusters) &&
431 offset != cluster_list_first(&si->free_clusters) &&
432 cluster_is_free(&si->cluster_info[offset]);
433
434 if (!conflict)
435 return false;
436
437 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
438 cluster_set_null(&percpu_cluster->index);
439 return true;
440}
441
442/*
443 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
444 * might involve allocating a new cluster for current CPU too.
445 */
446static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
447 unsigned long *offset, unsigned long *scan_base)
448{
449 struct percpu_cluster *cluster;
450 bool found_free;
451 unsigned long tmp;
452
453new_cluster:
454 cluster = this_cpu_ptr(si->percpu_cluster);
455 if (cluster_is_null(&cluster->index)) {
456 if (!cluster_list_empty(&si->free_clusters)) {
457 cluster->index = si->free_clusters.head;
458 cluster->next = cluster_next(&cluster->index) *
459 SWAPFILE_CLUSTER;
460 } else if (!cluster_list_empty(&si->discard_clusters)) {
461 /*
462 * we don't have free cluster but have some clusters in
463 * discarding, do discard now and reclaim them
464 */
465 swap_do_scheduled_discard(si);
466 *scan_base = *offset = si->cluster_next;
467 goto new_cluster;
468 } else
469 return;
470 }
471
472 found_free = false;
473
474 /*
475 * Other CPUs can use our cluster if they can't find a free cluster,
476 * check if there is still free entry in the cluster
477 */
478 tmp = cluster->next;
479 while (tmp < si->max && tmp < (cluster_next(&cluster->index) + 1) *
480 SWAPFILE_CLUSTER) {
481 if (!si->swap_map[tmp]) {
482 found_free = true;
483 break;
484 }
485 tmp++;
486 }
487 if (!found_free) {
488 cluster_set_null(&cluster->index);
489 goto new_cluster;
490 }
491 cluster->next = tmp + 1;
492 *offset = tmp;
493 *scan_base = tmp;
494}
495
496static unsigned long scan_swap_map(struct swap_info_struct *si,
497 unsigned char usage)
498{
499 unsigned long offset;
500 unsigned long scan_base;
501 unsigned long last_in_cluster = 0;
502 int latency_ration = LATENCY_LIMIT;
503
504 /*
505 * We try to cluster swap pages by allocating them sequentially
506 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
507 * way, however, we resort to first-free allocation, starting
508 * a new cluster. This prevents us from scattering swap pages
509 * all over the entire swap partition, so that we reduce
510 * overall disk seek times between swap pages. -- sct
511 * But we do now try to find an empty cluster. -Andrea
512 * And we let swap pages go all over an SSD partition. Hugh
513 */
514
515 si->flags += SWP_SCANNING;
516 scan_base = offset = si->cluster_next;
517
518 /* SSD algorithm */
519 if (si->cluster_info) {
520 scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
521 goto checks;
522 }
523
524 if (unlikely(!si->cluster_nr--)) {
525 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
526 si->cluster_nr = SWAPFILE_CLUSTER - 1;
527 goto checks;
528 }
529
530 spin_unlock(&si->lock);
531
532 /*
533 * If seek is expensive, start searching for new cluster from
534 * start of partition, to minimize the span of allocated swap.
535 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
536 * case, just handled by scan_swap_map_try_ssd_cluster() above.
537 */
538 scan_base = offset = si->lowest_bit;
539 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
540
541 /* Locate the first empty (unaligned) cluster */
542 for (; last_in_cluster <= si->highest_bit; offset++) {
543 if (si->swap_map[offset])
544 last_in_cluster = offset + SWAPFILE_CLUSTER;
545 else if (offset == last_in_cluster) {
546 spin_lock(&si->lock);
547 offset -= SWAPFILE_CLUSTER - 1;
548 si->cluster_next = offset;
549 si->cluster_nr = SWAPFILE_CLUSTER - 1;
550 goto checks;
551 }
552 if (unlikely(--latency_ration < 0)) {
553 cond_resched();
554 latency_ration = LATENCY_LIMIT;
555 }
556 }
557
558 offset = scan_base;
559 spin_lock(&si->lock);
560 si->cluster_nr = SWAPFILE_CLUSTER - 1;
561 }
562
563checks:
564 if (si->cluster_info) {
565 while (scan_swap_map_ssd_cluster_conflict(si, offset))
566 scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
567 }
568 if (!(si->flags & SWP_WRITEOK))
569 goto no_page;
570 if (!si->highest_bit)
571 goto no_page;
572 if (offset > si->highest_bit)
573 scan_base = offset = si->lowest_bit;
574
575 /* reuse swap entry of cache-only swap if not busy. */
576 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
577 int swap_was_freed;
578 spin_unlock(&si->lock);
579 swap_was_freed = __try_to_reclaim_swap(si, offset);
580 spin_lock(&si->lock);
581 /* entry was freed successfully, try to use this again */
582 if (swap_was_freed)
583 goto checks;
584 goto scan; /* check next one */
585 }
586
587 if (si->swap_map[offset])
588 goto scan;
589
590 if (offset == si->lowest_bit)
591 si->lowest_bit++;
592 if (offset == si->highest_bit)
593 si->highest_bit--;
594 si->inuse_pages++;
595 if (si->inuse_pages == si->pages) {
596 si->lowest_bit = si->max;
597 si->highest_bit = 0;
598 spin_lock(&swap_avail_lock);
599 plist_del(&si->avail_list, &swap_avail_head);
600 spin_unlock(&swap_avail_lock);
601 }
602 si->swap_map[offset] = usage;
603 inc_cluster_info_page(si, si->cluster_info, offset);
604 si->cluster_next = offset + 1;
605 si->flags -= SWP_SCANNING;
606
607 return offset;
608
609scan:
610 spin_unlock(&si->lock);
611 while (++offset <= si->highest_bit) {
612 if (!si->swap_map[offset]) {
613 spin_lock(&si->lock);
614 goto checks;
615 }
616 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
617 spin_lock(&si->lock);
618 goto checks;
619 }
620 if (unlikely(--latency_ration < 0)) {
621 cond_resched();
622 latency_ration = LATENCY_LIMIT;
623 }
624 }
625 offset = si->lowest_bit;
626 while (offset < scan_base) {
627 if (!si->swap_map[offset]) {
628 spin_lock(&si->lock);
629 goto checks;
630 }
631 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
632 spin_lock(&si->lock);
633 goto checks;
634 }
635 if (unlikely(--latency_ration < 0)) {
636 cond_resched();
637 latency_ration = LATENCY_LIMIT;
638 }
639 offset++;
640 }
641 spin_lock(&si->lock);
642
643no_page:
644 si->flags -= SWP_SCANNING;
645 return 0;
646}
647
648swp_entry_t get_swap_page(void)
649{
650 struct swap_info_struct *si, *next;
651 pgoff_t offset;
652
653 if (atomic_long_read(&nr_swap_pages) <= 0)
654 goto noswap;
655 atomic_long_dec(&nr_swap_pages);
656
657 spin_lock(&swap_avail_lock);
658
659start_over:
660 plist_for_each_entry_safe(si, next, &swap_avail_head, avail_list) {
661 /* requeue si to after same-priority siblings */
662 plist_requeue(&si->avail_list, &swap_avail_head);
663 spin_unlock(&swap_avail_lock);
664 spin_lock(&si->lock);
665 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
666 spin_lock(&swap_avail_lock);
667 if (plist_node_empty(&si->avail_list)) {
668 spin_unlock(&si->lock);
669 goto nextsi;
670 }
671 WARN(!si->highest_bit,
672 "swap_info %d in list but !highest_bit\n",
673 si->type);
674 WARN(!(si->flags & SWP_WRITEOK),
675 "swap_info %d in list but !SWP_WRITEOK\n",
676 si->type);
677 plist_del(&si->avail_list, &swap_avail_head);
678 spin_unlock(&si->lock);
679 goto nextsi;
680 }
681
682 /* This is called for allocating swap entry for cache */
683 offset = scan_swap_map(si, SWAP_HAS_CACHE);
684 spin_unlock(&si->lock);
685 if (offset)
686 return swp_entry(si->type, offset);
687 pr_debug("scan_swap_map of si %d failed to find offset\n",
688 si->type);
689 spin_lock(&swap_avail_lock);
690nextsi:
691 /*
692 * if we got here, it's likely that si was almost full before,
693 * and since scan_swap_map() can drop the si->lock, multiple
694 * callers probably all tried to get a page from the same si
695 * and it filled up before we could get one; or, the si filled
696 * up between us dropping swap_avail_lock and taking si->lock.
697 * Since we dropped the swap_avail_lock, the swap_avail_head
698 * list may have been modified; so if next is still in the
699 * swap_avail_head list then try it, otherwise start over.
700 */
701 if (plist_node_empty(&next->avail_list))
702 goto start_over;
703 }
704
705 spin_unlock(&swap_avail_lock);
706
707 atomic_long_inc(&nr_swap_pages);
708noswap:
709 return (swp_entry_t) {0};
710}
711
712/* The only caller of this function is now suspend routine */
713swp_entry_t get_swap_page_of_type(int type)
714{
715 struct swap_info_struct *si;
716 pgoff_t offset;
717
718 si = swap_info[type];
719 spin_lock(&si->lock);
720 if (si && (si->flags & SWP_WRITEOK)) {
721 atomic_long_dec(&nr_swap_pages);
722 /* This is called for allocating swap entry, not cache */
723 offset = scan_swap_map(si, 1);
724 if (offset) {
725 spin_unlock(&si->lock);
726 return swp_entry(type, offset);
727 }
728 atomic_long_inc(&nr_swap_pages);
729 }
730 spin_unlock(&si->lock);
731 return (swp_entry_t) {0};
732}
733
734static struct swap_info_struct *swap_info_get(swp_entry_t entry)
735{
736 struct swap_info_struct *p;
737 unsigned long offset, type;
738
739 if (!entry.val)
740 goto out;
741 type = swp_type(entry);
742 if (type >= nr_swapfiles)
743 goto bad_nofile;
744 p = swap_info[type];
745 if (!(p->flags & SWP_USED))
746 goto bad_device;
747 offset = swp_offset(entry);
748 if (offset >= p->max)
749 goto bad_offset;
750 if (!p->swap_map[offset])
751 goto bad_free;
752 spin_lock(&p->lock);
753 return p;
754
755bad_free:
756 pr_err("swap_free: %s%08lx\n", Unused_offset, entry.val);
757 goto out;
758bad_offset:
759 pr_err("swap_free: %s%08lx\n", Bad_offset, entry.val);
760 goto out;
761bad_device:
762 pr_err("swap_free: %s%08lx\n", Unused_file, entry.val);
763 goto out;
764bad_nofile:
765 pr_err("swap_free: %s%08lx\n", Bad_file, entry.val);
766out:
767 return NULL;
768}
769
770static unsigned char swap_entry_free(struct swap_info_struct *p,
771 swp_entry_t entry, unsigned char usage)
772{
773 unsigned long offset = swp_offset(entry);
774 unsigned char count;
775 unsigned char has_cache;
776
777 count = p->swap_map[offset];
778 has_cache = count & SWAP_HAS_CACHE;
779 count &= ~SWAP_HAS_CACHE;
780
781 if (usage == SWAP_HAS_CACHE) {
782 VM_BUG_ON(!has_cache);
783 has_cache = 0;
784 } else if (count == SWAP_MAP_SHMEM) {
785 /*
786 * Or we could insist on shmem.c using a special
787 * swap_shmem_free() and free_shmem_swap_and_cache()...
788 */
789 count = 0;
790 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
791 if (count == COUNT_CONTINUED) {
792 if (swap_count_continued(p, offset, count))
793 count = SWAP_MAP_MAX | COUNT_CONTINUED;
794 else
795 count = SWAP_MAP_MAX;
796 } else
797 count--;
798 }
799
800 usage = count | has_cache;
801 p->swap_map[offset] = usage;
802
803 /* free if no reference */
804 if (!usage) {
805 mem_cgroup_uncharge_swap(entry);
806 dec_cluster_info_page(p, p->cluster_info, offset);
807 if (offset < p->lowest_bit)
808 p->lowest_bit = offset;
809 if (offset > p->highest_bit) {
810 bool was_full = !p->highest_bit;
811 p->highest_bit = offset;
812 if (was_full && (p->flags & SWP_WRITEOK)) {
813 spin_lock(&swap_avail_lock);
814 WARN_ON(!plist_node_empty(&p->avail_list));
815 if (plist_node_empty(&p->avail_list))
816 plist_add(&p->avail_list,
817 &swap_avail_head);
818 spin_unlock(&swap_avail_lock);
819 }
820 }
821 atomic_long_inc(&nr_swap_pages);
822 p->inuse_pages--;
823 frontswap_invalidate_page(p->type, offset);
824 if (p->flags & SWP_BLKDEV) {
825 struct gendisk *disk = p->bdev->bd_disk;
826 if (disk->fops->swap_slot_free_notify)
827 disk->fops->swap_slot_free_notify(p->bdev,
828 offset);
829 }
830 }
831
832 return usage;
833}
834
835/*
836 * Caller has made sure that the swap device corresponding to entry
837 * is still around or has not been recycled.
838 */
839void swap_free(swp_entry_t entry)
840{
841 struct swap_info_struct *p;
842
843 p = swap_info_get(entry);
844 if (p) {
845 swap_entry_free(p, entry, 1);
846 spin_unlock(&p->lock);
847 }
848}
849
850/*
851 * Called after dropping swapcache to decrease refcnt to swap entries.
852 */
853void swapcache_free(swp_entry_t entry)
854{
855 struct swap_info_struct *p;
856
857 p = swap_info_get(entry);
858 if (p) {
859 swap_entry_free(p, entry, SWAP_HAS_CACHE);
860 spin_unlock(&p->lock);
861 }
862}
863
864/*
865 * How many references to page are currently swapped out?
866 * This does not give an exact answer when swap count is continued,
867 * but does include the high COUNT_CONTINUED flag to allow for that.
868 */
869int page_swapcount(struct page *page)
870{
871 int count = 0;
872 struct swap_info_struct *p;
873 swp_entry_t entry;
874
875 entry.val = page_private(page);
876 p = swap_info_get(entry);
877 if (p) {
878 count = swap_count(p->swap_map[swp_offset(entry)]);
879 spin_unlock(&p->lock);
880 }
881 return count;
882}
883
884/*
885 * How many references to @entry are currently swapped out?
886 * This considers COUNT_CONTINUED so it returns exact answer.
887 */
888int swp_swapcount(swp_entry_t entry)
889{
890 int count, tmp_count, n;
891 struct swap_info_struct *p;
892 struct page *page;
893 pgoff_t offset;
894 unsigned char *map;
895
896 p = swap_info_get(entry);
897 if (!p)
898 return 0;
899
900 count = swap_count(p->swap_map[swp_offset(entry)]);
901 if (!(count & COUNT_CONTINUED))
902 goto out;
903
904 count &= ~COUNT_CONTINUED;
905 n = SWAP_MAP_MAX + 1;
906
907 offset = swp_offset(entry);
908 page = vmalloc_to_page(p->swap_map + offset);
909 offset &= ~PAGE_MASK;
910 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
911
912 do {
913 page = list_next_entry(page, lru);
914 map = kmap_atomic(page);
915 tmp_count = map[offset];
916 kunmap_atomic(map);
917
918 count += (tmp_count & ~COUNT_CONTINUED) * n;
919 n *= (SWAP_CONT_MAX + 1);
920 } while (tmp_count & COUNT_CONTINUED);
921out:
922 spin_unlock(&p->lock);
923 return count;
924}
925
926/*
927 * We can write to an anon page without COW if there are no other references
928 * to it. And as a side-effect, free up its swap: because the old content
929 * on disk will never be read, and seeking back there to write new content
930 * later would only waste time away from clustering.
931 *
932 * NOTE: total_mapcount should not be relied upon by the caller if
933 * reuse_swap_page() returns false, but it may be always overwritten
934 * (see the other implementation for CONFIG_SWAP=n).
935 */
936bool reuse_swap_page(struct page *page, int *total_mapcount)
937{
938 int count;
939
940 VM_BUG_ON_PAGE(!PageLocked(page), page);
941 if (unlikely(PageKsm(page)))
942 return false;
943 count = page_trans_huge_mapcount(page, total_mapcount);
944 if (count <= 1 && PageSwapCache(page)) {
945 count += page_swapcount(page);
946 if (count != 1)
947 goto out;
948 if (!PageWriteback(page)) {
949 delete_from_swap_cache(page);
950 SetPageDirty(page);
951 } else {
952 swp_entry_t entry;
953 struct swap_info_struct *p;
954
955 entry.val = page_private(page);
956 p = swap_info_get(entry);
957 if (p->flags & SWP_STABLE_WRITES) {
958 spin_unlock(&p->lock);
959 return false;
960 }
961 spin_unlock(&p->lock);
962 }
963 }
964out:
965 return count <= 1;
966}
967
968/*
969 * If swap is getting full, or if there are no more mappings of this page,
970 * then try_to_free_swap is called to free its swap space.
971 */
972int try_to_free_swap(struct page *page)
973{
974 VM_BUG_ON_PAGE(!PageLocked(page), page);
975
976 if (!PageSwapCache(page))
977 return 0;
978 if (PageWriteback(page))
979 return 0;
980 if (page_swapcount(page))
981 return 0;
982
983 /*
984 * Once hibernation has begun to create its image of memory,
985 * there's a danger that one of the calls to try_to_free_swap()
986 * - most probably a call from __try_to_reclaim_swap() while
987 * hibernation is allocating its own swap pages for the image,
988 * but conceivably even a call from memory reclaim - will free
989 * the swap from a page which has already been recorded in the
990 * image as a clean swapcache page, and then reuse its swap for
991 * another page of the image. On waking from hibernation, the
992 * original page might be freed under memory pressure, then
993 * later read back in from swap, now with the wrong data.
994 *
995 * Hibernation suspends storage while it is writing the image
996 * to disk so check that here.
997 */
998 if (pm_suspended_storage())
999 return 0;
1000
1001 delete_from_swap_cache(page);
1002 SetPageDirty(page);
1003 return 1;
1004}
1005
1006/*
1007 * Free the swap entry like above, but also try to
1008 * free the page cache entry if it is the last user.
1009 */
1010int free_swap_and_cache(swp_entry_t entry)
1011{
1012 struct swap_info_struct *p;
1013 struct page *page = NULL;
1014
1015 if (non_swap_entry(entry))
1016 return 1;
1017
1018 p = swap_info_get(entry);
1019 if (p) {
1020 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
1021 page = find_get_page(swap_address_space(entry),
1022 swp_offset(entry));
1023 if (page && !trylock_page(page)) {
1024 put_page(page);
1025 page = NULL;
1026 }
1027 }
1028 spin_unlock(&p->lock);
1029 }
1030 if (page) {
1031 /*
1032 * Not mapped elsewhere, or swap space full? Free it!
1033 * Also recheck PageSwapCache now page is locked (above).
1034 */
1035 if (PageSwapCache(page) && !PageWriteback(page) &&
1036 (!page_mapped(page) || mem_cgroup_swap_full(page))) {
1037 delete_from_swap_cache(page);
1038 SetPageDirty(page);
1039 }
1040 unlock_page(page);
1041 put_page(page);
1042 }
1043 return p != NULL;
1044}
1045
1046#ifdef CONFIG_HIBERNATION
1047/*
1048 * Find the swap type that corresponds to given device (if any).
1049 *
1050 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1051 * from 0, in which the swap header is expected to be located.
1052 *
1053 * This is needed for the suspend to disk (aka swsusp).
1054 */
1055int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
1056{
1057 struct block_device *bdev = NULL;
1058 int type;
1059
1060 if (device)
1061 bdev = bdget(device);
1062
1063 spin_lock(&swap_lock);
1064 for (type = 0; type < nr_swapfiles; type++) {
1065 struct swap_info_struct *sis = swap_info[type];
1066
1067 if (!(sis->flags & SWP_WRITEOK))
1068 continue;
1069
1070 if (!bdev) {
1071 if (bdev_p)
1072 *bdev_p = bdgrab(sis->bdev);
1073
1074 spin_unlock(&swap_lock);
1075 return type;
1076 }
1077 if (bdev == sis->bdev) {
1078 struct swap_extent *se = &sis->first_swap_extent;
1079
1080 if (se->start_block == offset) {
1081 if (bdev_p)
1082 *bdev_p = bdgrab(sis->bdev);
1083
1084 spin_unlock(&swap_lock);
1085 bdput(bdev);
1086 return type;
1087 }
1088 }
1089 }
1090 spin_unlock(&swap_lock);
1091 if (bdev)
1092 bdput(bdev);
1093
1094 return -ENODEV;
1095}
1096
1097/*
1098 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1099 * corresponding to given index in swap_info (swap type).
1100 */
1101sector_t swapdev_block(int type, pgoff_t offset)
1102{
1103 struct block_device *bdev;
1104
1105 if ((unsigned int)type >= nr_swapfiles)
1106 return 0;
1107 if (!(swap_info[type]->flags & SWP_WRITEOK))
1108 return 0;
1109 return map_swap_entry(swp_entry(type, offset), &bdev);
1110}
1111
1112/*
1113 * Return either the total number of swap pages of given type, or the number
1114 * of free pages of that type (depending on @free)
1115 *
1116 * This is needed for software suspend
1117 */
1118unsigned int count_swap_pages(int type, int free)
1119{
1120 unsigned int n = 0;
1121
1122 spin_lock(&swap_lock);
1123 if ((unsigned int)type < nr_swapfiles) {
1124 struct swap_info_struct *sis = swap_info[type];
1125
1126 spin_lock(&sis->lock);
1127 if (sis->flags & SWP_WRITEOK) {
1128 n = sis->pages;
1129 if (free)
1130 n -= sis->inuse_pages;
1131 }
1132 spin_unlock(&sis->lock);
1133 }
1134 spin_unlock(&swap_lock);
1135 return n;
1136}
1137#endif /* CONFIG_HIBERNATION */
1138
1139static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1140{
1141 return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte);
1142}
1143
1144/*
1145 * No need to decide whether this PTE shares the swap entry with others,
1146 * just let do_wp_page work it out if a write is requested later - to
1147 * force COW, vm_page_prot omits write permission from any private vma.
1148 */
1149static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1150 unsigned long addr, swp_entry_t entry, struct page *page)
1151{
1152 struct page *swapcache;
1153 struct mem_cgroup *memcg;
1154 spinlock_t *ptl;
1155 pte_t *pte;
1156 int ret = 1;
1157
1158 swapcache = page;
1159 page = ksm_might_need_to_copy(page, vma, addr);
1160 if (unlikely(!page))
1161 return -ENOMEM;
1162
1163 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL,
1164 &memcg, false)) {
1165 ret = -ENOMEM;
1166 goto out_nolock;
1167 }
1168
1169 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1170 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1171 mem_cgroup_cancel_charge(page, memcg, false);
1172 ret = 0;
1173 goto out;
1174 }
1175
1176 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1177 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1178 get_page(page);
1179 set_pte_at(vma->vm_mm, addr, pte,
1180 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1181 if (page == swapcache) {
1182 page_add_anon_rmap(page, vma, addr, false);
1183 mem_cgroup_commit_charge(page, memcg, true, false);
1184 } else { /* ksm created a completely new copy */
1185 page_add_new_anon_rmap(page, vma, addr, false);
1186 mem_cgroup_commit_charge(page, memcg, false, false);
1187 lru_cache_add_active_or_unevictable(page, vma);
1188 }
1189 swap_free(entry);
1190 /*
1191 * Move the page to the active list so it is not
1192 * immediately swapped out again after swapon.
1193 */
1194 activate_page(page);
1195out:
1196 pte_unmap_unlock(pte, ptl);
1197out_nolock:
1198 if (page != swapcache) {
1199 unlock_page(page);
1200 put_page(page);
1201 }
1202 return ret;
1203}
1204
1205static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1206 unsigned long addr, unsigned long end,
1207 swp_entry_t entry, struct page *page)
1208{
1209 pte_t swp_pte = swp_entry_to_pte(entry);
1210 pte_t *pte;
1211 int ret = 0;
1212
1213 /*
1214 * We don't actually need pte lock while scanning for swp_pte: since
1215 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
1216 * page table while we're scanning; though it could get zapped, and on
1217 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
1218 * of unmatched parts which look like swp_pte, so unuse_pte must
1219 * recheck under pte lock. Scanning without pte lock lets it be
1220 * preemptable whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
1221 */
1222 pte = pte_offset_map(pmd, addr);
1223 do {
1224 /*
1225 * swapoff spends a _lot_ of time in this loop!
1226 * Test inline before going to call unuse_pte.
1227 */
1228 if (unlikely(pte_same_as_swp(*pte, swp_pte))) {
1229 pte_unmap(pte);
1230 ret = unuse_pte(vma, pmd, addr, entry, page);
1231 if (ret)
1232 goto out;
1233 pte = pte_offset_map(pmd, addr);
1234 }
1235 } while (pte++, addr += PAGE_SIZE, addr != end);
1236 pte_unmap(pte - 1);
1237out:
1238 return ret;
1239}
1240
1241static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1242 unsigned long addr, unsigned long end,
1243 swp_entry_t entry, struct page *page)
1244{
1245 pmd_t *pmd;
1246 unsigned long next;
1247 int ret;
1248
1249 pmd = pmd_offset(pud, addr);
1250 do {
1251 cond_resched();
1252 next = pmd_addr_end(addr, end);
1253 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1254 continue;
1255 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
1256 if (ret)
1257 return ret;
1258 } while (pmd++, addr = next, addr != end);
1259 return 0;
1260}
1261
1262static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
1263 unsigned long addr, unsigned long end,
1264 swp_entry_t entry, struct page *page)
1265{
1266 pud_t *pud;
1267 unsigned long next;
1268 int ret;
1269
1270 pud = pud_offset(pgd, addr);
1271 do {
1272 next = pud_addr_end(addr, end);
1273 if (pud_none_or_clear_bad(pud))
1274 continue;
1275 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
1276 if (ret)
1277 return ret;
1278 } while (pud++, addr = next, addr != end);
1279 return 0;
1280}
1281
1282static int unuse_vma(struct vm_area_struct *vma,
1283 swp_entry_t entry, struct page *page)
1284{
1285 pgd_t *pgd;
1286 unsigned long addr, end, next;
1287 int ret;
1288
1289 if (page_anon_vma(page)) {
1290 addr = page_address_in_vma(page, vma);
1291 if (addr == -EFAULT)
1292 return 0;
1293 else
1294 end = addr + PAGE_SIZE;
1295 } else {
1296 addr = vma->vm_start;
1297 end = vma->vm_end;
1298 }
1299
1300 pgd = pgd_offset(vma->vm_mm, addr);
1301 do {
1302 next = pgd_addr_end(addr, end);
1303 if (pgd_none_or_clear_bad(pgd))
1304 continue;
1305 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
1306 if (ret)
1307 return ret;
1308 } while (pgd++, addr = next, addr != end);
1309 return 0;
1310}
1311
1312static int unuse_mm(struct mm_struct *mm,
1313 swp_entry_t entry, struct page *page)
1314{
1315 struct vm_area_struct *vma;
1316 int ret = 0;
1317
1318 if (!down_read_trylock(&mm->mmap_sem)) {
1319 /*
1320 * Activate page so shrink_inactive_list is unlikely to unmap
1321 * its ptes while lock is dropped, so swapoff can make progress.
1322 */
1323 activate_page(page);
1324 unlock_page(page);
1325 down_read(&mm->mmap_sem);
1326 lock_page(page);
1327 }
1328 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1329 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
1330 break;
1331 cond_resched();
1332 }
1333 up_read(&mm->mmap_sem);
1334 return (ret < 0)? ret: 0;
1335}
1336
1337/*
1338 * Scan swap_map (or frontswap_map if frontswap parameter is true)
1339 * from current position to next entry still in use.
1340 * Recycle to start on reaching the end, returning 0 when empty.
1341 */
1342static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1343 unsigned int prev, bool frontswap)
1344{
1345 unsigned int max = si->max;
1346 unsigned int i = prev;
1347 unsigned char count;
1348
1349 /*
1350 * No need for swap_lock here: we're just looking
1351 * for whether an entry is in use, not modifying it; false
1352 * hits are okay, and sys_swapoff() has already prevented new
1353 * allocations from this area (while holding swap_lock).
1354 */
1355 for (;;) {
1356 if (++i >= max) {
1357 if (!prev) {
1358 i = 0;
1359 break;
1360 }
1361 /*
1362 * No entries in use at top of swap_map,
1363 * loop back to start and recheck there.
1364 */
1365 max = prev + 1;
1366 prev = 0;
1367 i = 1;
1368 }
1369 count = READ_ONCE(si->swap_map[i]);
1370 if (count && swap_count(count) != SWAP_MAP_BAD)
1371 if (!frontswap || frontswap_test(si, i))
1372 break;
1373 if ((i % LATENCY_LIMIT) == 0)
1374 cond_resched();
1375 }
1376 return i;
1377}
1378
1379/*
1380 * We completely avoid races by reading each swap page in advance,
1381 * and then search for the process using it. All the necessary
1382 * page table adjustments can then be made atomically.
1383 *
1384 * if the boolean frontswap is true, only unuse pages_to_unuse pages;
1385 * pages_to_unuse==0 means all pages; ignored if frontswap is false
1386 */
1387int try_to_unuse(unsigned int type, bool frontswap,
1388 unsigned long pages_to_unuse)
1389{
1390 struct swap_info_struct *si = swap_info[type];
1391 struct mm_struct *start_mm;
1392 volatile unsigned char *swap_map; /* swap_map is accessed without
1393 * locking. Mark it as volatile
1394 * to prevent compiler doing
1395 * something odd.
1396 */
1397 unsigned char swcount;
1398 struct page *page;
1399 swp_entry_t entry;
1400 unsigned int i = 0;
1401 int retval = 0;
1402
1403 /*
1404 * When searching mms for an entry, a good strategy is to
1405 * start at the first mm we freed the previous entry from
1406 * (though actually we don't notice whether we or coincidence
1407 * freed the entry). Initialize this start_mm with a hold.
1408 *
1409 * A simpler strategy would be to start at the last mm we
1410 * freed the previous entry from; but that would take less
1411 * advantage of mmlist ordering, which clusters forked mms
1412 * together, child after parent. If we race with dup_mmap(), we
1413 * prefer to resolve parent before child, lest we miss entries
1414 * duplicated after we scanned child: using last mm would invert
1415 * that.
1416 */
1417 start_mm = &init_mm;
1418 atomic_inc(&init_mm.mm_users);
1419
1420 /*
1421 * Keep on scanning until all entries have gone. Usually,
1422 * one pass through swap_map is enough, but not necessarily:
1423 * there are races when an instance of an entry might be missed.
1424 */
1425 while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
1426 if (signal_pending(current)) {
1427 retval = -EINTR;
1428 break;
1429 }
1430
1431 /*
1432 * Get a page for the entry, using the existing swap
1433 * cache page if there is one. Otherwise, get a clean
1434 * page and read the swap into it.
1435 */
1436 swap_map = &si->swap_map[i];
1437 entry = swp_entry(type, i);
1438 page = read_swap_cache_async(entry,
1439 GFP_HIGHUSER_MOVABLE, NULL, 0);
1440 if (!page) {
1441 /*
1442 * Either swap_duplicate() failed because entry
1443 * has been freed independently, and will not be
1444 * reused since sys_swapoff() already disabled
1445 * allocation from here, or alloc_page() failed.
1446 */
1447 swcount = *swap_map;
1448 /*
1449 * We don't hold lock here, so the swap entry could be
1450 * SWAP_MAP_BAD (when the cluster is discarding).
1451 * Instead of fail out, We can just skip the swap
1452 * entry because swapoff will wait for discarding
1453 * finish anyway.
1454 */
1455 if (!swcount || swcount == SWAP_MAP_BAD)
1456 continue;
1457 retval = -ENOMEM;
1458 break;
1459 }
1460
1461 /*
1462 * Don't hold on to start_mm if it looks like exiting.
1463 */
1464 if (atomic_read(&start_mm->mm_users) == 1) {
1465 mmput(start_mm);
1466 start_mm = &init_mm;
1467 atomic_inc(&init_mm.mm_users);
1468 }
1469
1470 /*
1471 * Wait for and lock page. When do_swap_page races with
1472 * try_to_unuse, do_swap_page can handle the fault much
1473 * faster than try_to_unuse can locate the entry. This
1474 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1475 * defer to do_swap_page in such a case - in some tests,
1476 * do_swap_page and try_to_unuse repeatedly compete.
1477 */
1478 wait_on_page_locked(page);
1479 wait_on_page_writeback(page);
1480 lock_page(page);
1481 wait_on_page_writeback(page);
1482
1483 /*
1484 * Remove all references to entry.
1485 */
1486 swcount = *swap_map;
1487 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1488 retval = shmem_unuse(entry, page);
1489 /* page has already been unlocked and released */
1490 if (retval < 0)
1491 break;
1492 continue;
1493 }
1494 if (swap_count(swcount) && start_mm != &init_mm)
1495 retval = unuse_mm(start_mm, entry, page);
1496
1497 if (swap_count(*swap_map)) {
1498 int set_start_mm = (*swap_map >= swcount);
1499 struct list_head *p = &start_mm->mmlist;
1500 struct mm_struct *new_start_mm = start_mm;
1501 struct mm_struct *prev_mm = start_mm;
1502 struct mm_struct *mm;
1503
1504 atomic_inc(&new_start_mm->mm_users);
1505 atomic_inc(&prev_mm->mm_users);
1506 spin_lock(&mmlist_lock);
1507 while (swap_count(*swap_map) && !retval &&
1508 (p = p->next) != &start_mm->mmlist) {
1509 mm = list_entry(p, struct mm_struct, mmlist);
1510 if (!atomic_inc_not_zero(&mm->mm_users))
1511 continue;
1512 spin_unlock(&mmlist_lock);
1513 mmput(prev_mm);
1514 prev_mm = mm;
1515
1516 cond_resched();
1517
1518 swcount = *swap_map;
1519 if (!swap_count(swcount)) /* any usage ? */
1520 ;
1521 else if (mm == &init_mm)
1522 set_start_mm = 1;
1523 else
1524 retval = unuse_mm(mm, entry, page);
1525
1526 if (set_start_mm && *swap_map < swcount) {
1527 mmput(new_start_mm);
1528 atomic_inc(&mm->mm_users);
1529 new_start_mm = mm;
1530 set_start_mm = 0;
1531 }
1532 spin_lock(&mmlist_lock);
1533 }
1534 spin_unlock(&mmlist_lock);
1535 mmput(prev_mm);
1536 mmput(start_mm);
1537 start_mm = new_start_mm;
1538 }
1539 if (retval) {
1540 unlock_page(page);
1541 put_page(page);
1542 break;
1543 }
1544
1545 /*
1546 * If a reference remains (rare), we would like to leave
1547 * the page in the swap cache; but try_to_unmap could
1548 * then re-duplicate the entry once we drop page lock,
1549 * so we might loop indefinitely; also, that page could
1550 * not be swapped out to other storage meanwhile. So:
1551 * delete from cache even if there's another reference,
1552 * after ensuring that the data has been saved to disk -
1553 * since if the reference remains (rarer), it will be
1554 * read from disk into another page. Splitting into two
1555 * pages would be incorrect if swap supported "shared
1556 * private" pages, but they are handled by tmpfs files.
1557 *
1558 * Given how unuse_vma() targets one particular offset
1559 * in an anon_vma, once the anon_vma has been determined,
1560 * this splitting happens to be just what is needed to
1561 * handle where KSM pages have been swapped out: re-reading
1562 * is unnecessarily slow, but we can fix that later on.
1563 */
1564 if (swap_count(*swap_map) &&
1565 PageDirty(page) && PageSwapCache(page)) {
1566 struct writeback_control wbc = {
1567 .sync_mode = WB_SYNC_NONE,
1568 };
1569
1570 swap_writepage(page, &wbc);
1571 lock_page(page);
1572 wait_on_page_writeback(page);
1573 }
1574
1575 /*
1576 * It is conceivable that a racing task removed this page from
1577 * swap cache just before we acquired the page lock at the top,
1578 * or while we dropped it in unuse_mm(). The page might even
1579 * be back in swap cache on another swap area: that we must not
1580 * delete, since it may not have been written out to swap yet.
1581 */
1582 if (PageSwapCache(page) &&
1583 likely(page_private(page) == entry.val))
1584 delete_from_swap_cache(page);
1585
1586 /*
1587 * So we could skip searching mms once swap count went
1588 * to 1, we did not mark any present ptes as dirty: must
1589 * mark page dirty so shrink_page_list will preserve it.
1590 */
1591 SetPageDirty(page);
1592 unlock_page(page);
1593 put_page(page);
1594
1595 /*
1596 * Make sure that we aren't completely killing
1597 * interactive performance.
1598 */
1599 cond_resched();
1600 if (frontswap && pages_to_unuse > 0) {
1601 if (!--pages_to_unuse)
1602 break;
1603 }
1604 }
1605
1606 mmput(start_mm);
1607 return retval;
1608}
1609
1610/*
1611 * After a successful try_to_unuse, if no swap is now in use, we know
1612 * we can empty the mmlist. swap_lock must be held on entry and exit.
1613 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1614 * added to the mmlist just after page_duplicate - before would be racy.
1615 */
1616static void drain_mmlist(void)
1617{
1618 struct list_head *p, *next;
1619 unsigned int type;
1620
1621 for (type = 0; type < nr_swapfiles; type++)
1622 if (swap_info[type]->inuse_pages)
1623 return;
1624 spin_lock(&mmlist_lock);
1625 list_for_each_safe(p, next, &init_mm.mmlist)
1626 list_del_init(p);
1627 spin_unlock(&mmlist_lock);
1628}
1629
1630/*
1631 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1632 * corresponds to page offset for the specified swap entry.
1633 * Note that the type of this function is sector_t, but it returns page offset
1634 * into the bdev, not sector offset.
1635 */
1636static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1637{
1638 struct swap_info_struct *sis;
1639 struct swap_extent *start_se;
1640 struct swap_extent *se;
1641 pgoff_t offset;
1642
1643 sis = swap_info[swp_type(entry)];
1644 *bdev = sis->bdev;
1645
1646 offset = swp_offset(entry);
1647 start_se = sis->curr_swap_extent;
1648 se = start_se;
1649
1650 for ( ; ; ) {
1651 if (se->start_page <= offset &&
1652 offset < (se->start_page + se->nr_pages)) {
1653 return se->start_block + (offset - se->start_page);
1654 }
1655 se = list_next_entry(se, list);
1656 sis->curr_swap_extent = se;
1657 BUG_ON(se == start_se); /* It *must* be present */
1658 }
1659}
1660
1661/*
1662 * Returns the page offset into bdev for the specified page's swap entry.
1663 */
1664sector_t map_swap_page(struct page *page, struct block_device **bdev)
1665{
1666 swp_entry_t entry;
1667 entry.val = page_private(page);
1668 return map_swap_entry(entry, bdev);
1669}
1670
1671/*
1672 * Free all of a swapdev's extent information
1673 */
1674static void destroy_swap_extents(struct swap_info_struct *sis)
1675{
1676 while (!list_empty(&sis->first_swap_extent.list)) {
1677 struct swap_extent *se;
1678
1679 se = list_first_entry(&sis->first_swap_extent.list,
1680 struct swap_extent, list);
1681 list_del(&se->list);
1682 kfree(se);
1683 }
1684
1685 if (sis->flags & SWP_FILE) {
1686 struct file *swap_file = sis->swap_file;
1687 struct address_space *mapping = swap_file->f_mapping;
1688
1689 sis->flags &= ~SWP_FILE;
1690 mapping->a_ops->swap_deactivate(swap_file);
1691 }
1692}
1693
1694/*
1695 * Add a block range (and the corresponding page range) into this swapdev's
1696 * extent list. The extent list is kept sorted in page order.
1697 *
1698 * This function rather assumes that it is called in ascending page order.
1699 */
1700int
1701add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1702 unsigned long nr_pages, sector_t start_block)
1703{
1704 struct swap_extent *se;
1705 struct swap_extent *new_se;
1706 struct list_head *lh;
1707
1708 if (start_page == 0) {
1709 se = &sis->first_swap_extent;
1710 sis->curr_swap_extent = se;
1711 se->start_page = 0;
1712 se->nr_pages = nr_pages;
1713 se->start_block = start_block;
1714 return 1;
1715 } else {
1716 lh = sis->first_swap_extent.list.prev; /* Highest extent */
1717 se = list_entry(lh, struct swap_extent, list);
1718 BUG_ON(se->start_page + se->nr_pages != start_page);
1719 if (se->start_block + se->nr_pages == start_block) {
1720 /* Merge it */
1721 se->nr_pages += nr_pages;
1722 return 0;
1723 }
1724 }
1725
1726 /*
1727 * No merge. Insert a new extent, preserving ordering.
1728 */
1729 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1730 if (new_se == NULL)
1731 return -ENOMEM;
1732 new_se->start_page = start_page;
1733 new_se->nr_pages = nr_pages;
1734 new_se->start_block = start_block;
1735
1736 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1737 return 1;
1738}
1739
1740/*
1741 * A `swap extent' is a simple thing which maps a contiguous range of pages
1742 * onto a contiguous range of disk blocks. An ordered list of swap extents
1743 * is built at swapon time and is then used at swap_writepage/swap_readpage
1744 * time for locating where on disk a page belongs.
1745 *
1746 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1747 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1748 * swap files identically.
1749 *
1750 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1751 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1752 * swapfiles are handled *identically* after swapon time.
1753 *
1754 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1755 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1756 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1757 * requirements, they are simply tossed out - we will never use those blocks
1758 * for swapping.
1759 *
1760 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1761 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1762 * which will scribble on the fs.
1763 *
1764 * The amount of disk space which a single swap extent represents varies.
1765 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1766 * extents in the list. To avoid much list walking, we cache the previous
1767 * search location in `curr_swap_extent', and start new searches from there.
1768 * This is extremely effective. The average number of iterations in
1769 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1770 */
1771static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1772{
1773 struct file *swap_file = sis->swap_file;
1774 struct address_space *mapping = swap_file->f_mapping;
1775 struct inode *inode = mapping->host;
1776 int ret;
1777
1778 if (S_ISBLK(inode->i_mode)) {
1779 ret = add_swap_extent(sis, 0, sis->max, 0);
1780 *span = sis->pages;
1781 return ret;
1782 }
1783
1784 if (mapping->a_ops->swap_activate) {
1785 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
1786 if (!ret) {
1787 sis->flags |= SWP_FILE;
1788 ret = add_swap_extent(sis, 0, sis->max, 0);
1789 *span = sis->pages;
1790 }
1791 return ret;
1792 }
1793
1794 return generic_swapfile_activate(sis, swap_file, span);
1795}
1796
1797static void _enable_swap_info(struct swap_info_struct *p, int prio,
1798 unsigned char *swap_map,
1799 struct swap_cluster_info *cluster_info)
1800{
1801 if (prio >= 0)
1802 p->prio = prio;
1803 else
1804 p->prio = --least_priority;
1805 /*
1806 * the plist prio is negated because plist ordering is
1807 * low-to-high, while swap ordering is high-to-low
1808 */
1809 p->list.prio = -p->prio;
1810 p->avail_list.prio = -p->prio;
1811 p->swap_map = swap_map;
1812 p->cluster_info = cluster_info;
1813 p->flags |= SWP_WRITEOK;
1814 atomic_long_add(p->pages, &nr_swap_pages);
1815 total_swap_pages += p->pages;
1816
1817 assert_spin_locked(&swap_lock);
1818 /*
1819 * both lists are plists, and thus priority ordered.
1820 * swap_active_head needs to be priority ordered for swapoff(),
1821 * which on removal of any swap_info_struct with an auto-assigned
1822 * (i.e. negative) priority increments the auto-assigned priority
1823 * of any lower-priority swap_info_structs.
1824 * swap_avail_head needs to be priority ordered for get_swap_page(),
1825 * which allocates swap pages from the highest available priority
1826 * swap_info_struct.
1827 */
1828 plist_add(&p->list, &swap_active_head);
1829 spin_lock(&swap_avail_lock);
1830 plist_add(&p->avail_list, &swap_avail_head);
1831 spin_unlock(&swap_avail_lock);
1832}
1833
1834static void enable_swap_info(struct swap_info_struct *p, int prio,
1835 unsigned char *swap_map,
1836 struct swap_cluster_info *cluster_info,
1837 unsigned long *frontswap_map)
1838{
1839 frontswap_init(p->type, frontswap_map);
1840 spin_lock(&swap_lock);
1841 spin_lock(&p->lock);
1842 _enable_swap_info(p, prio, swap_map, cluster_info);
1843 spin_unlock(&p->lock);
1844 spin_unlock(&swap_lock);
1845}
1846
1847static void reinsert_swap_info(struct swap_info_struct *p)
1848{
1849 spin_lock(&swap_lock);
1850 spin_lock(&p->lock);
1851 _enable_swap_info(p, p->prio, p->swap_map, p->cluster_info);
1852 spin_unlock(&p->lock);
1853 spin_unlock(&swap_lock);
1854}
1855
1856SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1857{
1858 struct swap_info_struct *p = NULL;
1859 unsigned char *swap_map;
1860 struct swap_cluster_info *cluster_info;
1861 unsigned long *frontswap_map;
1862 struct file *swap_file, *victim;
1863 struct address_space *mapping;
1864 struct inode *inode;
1865 struct filename *pathname;
1866 int err, found = 0;
1867 unsigned int old_block_size;
1868
1869 if (!capable(CAP_SYS_ADMIN))
1870 return -EPERM;
1871
1872 BUG_ON(!current->mm);
1873
1874 pathname = getname(specialfile);
1875 if (IS_ERR(pathname))
1876 return PTR_ERR(pathname);
1877
1878 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
1879 err = PTR_ERR(victim);
1880 if (IS_ERR(victim))
1881 goto out;
1882
1883 mapping = victim->f_mapping;
1884 spin_lock(&swap_lock);
1885 plist_for_each_entry(p, &swap_active_head, list) {
1886 if (p->flags & SWP_WRITEOK) {
1887 if (p->swap_file->f_mapping == mapping) {
1888 found = 1;
1889 break;
1890 }
1891 }
1892 }
1893 if (!found) {
1894 err = -EINVAL;
1895 spin_unlock(&swap_lock);
1896 goto out_dput;
1897 }
1898 if (!security_vm_enough_memory_mm(current->mm, p->pages))
1899 vm_unacct_memory(p->pages);
1900 else {
1901 err = -ENOMEM;
1902 spin_unlock(&swap_lock);
1903 goto out_dput;
1904 }
1905 spin_lock(&swap_avail_lock);
1906 plist_del(&p->avail_list, &swap_avail_head);
1907 spin_unlock(&swap_avail_lock);
1908 spin_lock(&p->lock);
1909 if (p->prio < 0) {
1910 struct swap_info_struct *si = p;
1911
1912 plist_for_each_entry_continue(si, &swap_active_head, list) {
1913 si->prio++;
1914 si->list.prio--;
1915 si->avail_list.prio--;
1916 }
1917 least_priority++;
1918 }
1919 plist_del(&p->list, &swap_active_head);
1920 atomic_long_sub(p->pages, &nr_swap_pages);
1921 total_swap_pages -= p->pages;
1922 p->flags &= ~SWP_WRITEOK;
1923 spin_unlock(&p->lock);
1924 spin_unlock(&swap_lock);
1925
1926 set_current_oom_origin();
1927 err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
1928 clear_current_oom_origin();
1929
1930 if (err) {
1931 /* re-insert swap space back into swap_list */
1932 reinsert_swap_info(p);
1933 goto out_dput;
1934 }
1935
1936 flush_work(&p->discard_work);
1937
1938 destroy_swap_extents(p);
1939 if (p->flags & SWP_CONTINUED)
1940 free_swap_count_continuations(p);
1941
1942 mutex_lock(&swapon_mutex);
1943 spin_lock(&swap_lock);
1944 spin_lock(&p->lock);
1945 drain_mmlist();
1946
1947 /* wait for anyone still in scan_swap_map */
1948 p->highest_bit = 0; /* cuts scans short */
1949 while (p->flags >= SWP_SCANNING) {
1950 spin_unlock(&p->lock);
1951 spin_unlock(&swap_lock);
1952 schedule_timeout_uninterruptible(1);
1953 spin_lock(&swap_lock);
1954 spin_lock(&p->lock);
1955 }
1956
1957 swap_file = p->swap_file;
1958 old_block_size = p->old_block_size;
1959 p->swap_file = NULL;
1960 p->max = 0;
1961 swap_map = p->swap_map;
1962 p->swap_map = NULL;
1963 cluster_info = p->cluster_info;
1964 p->cluster_info = NULL;
1965 frontswap_map = frontswap_map_get(p);
1966 spin_unlock(&p->lock);
1967 spin_unlock(&swap_lock);
1968 frontswap_invalidate_area(p->type);
1969 frontswap_map_set(p, NULL);
1970 mutex_unlock(&swapon_mutex);
1971 free_percpu(p->percpu_cluster);
1972 p->percpu_cluster = NULL;
1973 vfree(swap_map);
1974 vfree(cluster_info);
1975 vfree(frontswap_map);
1976 /* Destroy swap account information */
1977 swap_cgroup_swapoff(p->type);
1978
1979 inode = mapping->host;
1980 if (S_ISBLK(inode->i_mode)) {
1981 struct block_device *bdev = I_BDEV(inode);
1982 set_blocksize(bdev, old_block_size);
1983 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
1984 } else {
1985 inode_lock(inode);
1986 inode->i_flags &= ~S_SWAPFILE;
1987 inode_unlock(inode);
1988 }
1989 filp_close(swap_file, NULL);
1990
1991 /*
1992 * Clear the SWP_USED flag after all resources are freed so that swapon
1993 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
1994 * not hold p->lock after we cleared its SWP_WRITEOK.
1995 */
1996 spin_lock(&swap_lock);
1997 p->flags = 0;
1998 spin_unlock(&swap_lock);
1999
2000 err = 0;
2001 atomic_inc(&proc_poll_event);
2002 wake_up_interruptible(&proc_poll_wait);
2003
2004out_dput:
2005 filp_close(victim, NULL);
2006out:
2007 putname(pathname);
2008 return err;
2009}
2010
2011#ifdef CONFIG_PROC_FS
2012static unsigned swaps_poll(struct file *file, poll_table *wait)
2013{
2014 struct seq_file *seq = file->private_data;
2015
2016 poll_wait(file, &proc_poll_wait, wait);
2017
2018 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2019 seq->poll_event = atomic_read(&proc_poll_event);
2020 return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
2021 }
2022
2023 return POLLIN | POLLRDNORM;
2024}
2025
2026/* iterator */
2027static void *swap_start(struct seq_file *swap, loff_t *pos)
2028{
2029 struct swap_info_struct *si;
2030 int type;
2031 loff_t l = *pos;
2032
2033 mutex_lock(&swapon_mutex);
2034
2035 if (!l)
2036 return SEQ_START_TOKEN;
2037
2038 for (type = 0; type < nr_swapfiles; type++) {
2039 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
2040 si = swap_info[type];
2041 if (!(si->flags & SWP_USED) || !si->swap_map)
2042 continue;
2043 if (!--l)
2044 return si;
2045 }
2046
2047 return NULL;
2048}
2049
2050static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2051{
2052 struct swap_info_struct *si = v;
2053 int type;
2054
2055 if (v == SEQ_START_TOKEN)
2056 type = 0;
2057 else
2058 type = si->type + 1;
2059
2060 for (; type < nr_swapfiles; type++) {
2061 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
2062 si = swap_info[type];
2063 if (!(si->flags & SWP_USED) || !si->swap_map)
2064 continue;
2065 ++*pos;
2066 return si;
2067 }
2068
2069 return NULL;
2070}
2071
2072static void swap_stop(struct seq_file *swap, void *v)
2073{
2074 mutex_unlock(&swapon_mutex);
2075}
2076
2077static int swap_show(struct seq_file *swap, void *v)
2078{
2079 struct swap_info_struct *si = v;
2080 struct file *file;
2081 int len;
2082
2083 if (si == SEQ_START_TOKEN) {
2084 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
2085 return 0;
2086 }
2087
2088 file = si->swap_file;
2089 len = seq_file_path(swap, file, " \t\n\\");
2090 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
2091 len < 40 ? 40 - len : 1, " ",
2092 S_ISBLK(file_inode(file)->i_mode) ?
2093 "partition" : "file\t",
2094 si->pages << (PAGE_SHIFT - 10),
2095 si->inuse_pages << (PAGE_SHIFT - 10),
2096 si->prio);
2097 return 0;
2098}
2099
2100static const struct seq_operations swaps_op = {
2101 .start = swap_start,
2102 .next = swap_next,
2103 .stop = swap_stop,
2104 .show = swap_show
2105};
2106
2107static int swaps_open(struct inode *inode, struct file *file)
2108{
2109 struct seq_file *seq;
2110 int ret;
2111
2112 ret = seq_open(file, &swaps_op);
2113 if (ret)
2114 return ret;
2115
2116 seq = file->private_data;
2117 seq->poll_event = atomic_read(&proc_poll_event);
2118 return 0;
2119}
2120
2121static const struct file_operations proc_swaps_operations = {
2122 .open = swaps_open,
2123 .read = seq_read,
2124 .llseek = seq_lseek,
2125 .release = seq_release,
2126 .poll = swaps_poll,
2127};
2128
2129static int __init procswaps_init(void)
2130{
2131 proc_create("swaps", 0, NULL, &proc_swaps_operations);
2132 return 0;
2133}
2134__initcall(procswaps_init);
2135#endif /* CONFIG_PROC_FS */
2136
2137#ifdef MAX_SWAPFILES_CHECK
2138static int __init max_swapfiles_check(void)
2139{
2140 MAX_SWAPFILES_CHECK();
2141 return 0;
2142}
2143late_initcall(max_swapfiles_check);
2144#endif
2145
2146static struct swap_info_struct *alloc_swap_info(void)
2147{
2148 struct swap_info_struct *p;
2149 unsigned int type;
2150
2151 p = kzalloc(sizeof(*p), GFP_KERNEL);
2152 if (!p)
2153 return ERR_PTR(-ENOMEM);
2154
2155 spin_lock(&swap_lock);
2156 for (type = 0; type < nr_swapfiles; type++) {
2157 if (!(swap_info[type]->flags & SWP_USED))
2158 break;
2159 }
2160 if (type >= MAX_SWAPFILES) {
2161 spin_unlock(&swap_lock);
2162 kfree(p);
2163 return ERR_PTR(-EPERM);
2164 }
2165 if (type >= nr_swapfiles) {
2166 p->type = type;
2167 swap_info[type] = p;
2168 /*
2169 * Write swap_info[type] before nr_swapfiles, in case a
2170 * racing procfs swap_start() or swap_next() is reading them.
2171 * (We never shrink nr_swapfiles, we never free this entry.)
2172 */
2173 smp_wmb();
2174 nr_swapfiles++;
2175 } else {
2176 kfree(p);
2177 p = swap_info[type];
2178 /*
2179 * Do not memset this entry: a racing procfs swap_next()
2180 * would be relying on p->type to remain valid.
2181 */
2182 }
2183 INIT_LIST_HEAD(&p->first_swap_extent.list);
2184 plist_node_init(&p->list, 0);
2185 plist_node_init(&p->avail_list, 0);
2186 p->flags = SWP_USED;
2187 spin_unlock(&swap_lock);
2188 spin_lock_init(&p->lock);
2189
2190 return p;
2191}
2192
2193static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2194{
2195 int error;
2196
2197 if (S_ISBLK(inode->i_mode)) {
2198 p->bdev = bdgrab(I_BDEV(inode));
2199 error = blkdev_get(p->bdev,
2200 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2201 if (error < 0) {
2202 p->bdev = NULL;
2203 return error;
2204 }
2205 p->old_block_size = block_size(p->bdev);
2206 error = set_blocksize(p->bdev, PAGE_SIZE);
2207 if (error < 0)
2208 return error;
2209 p->flags |= SWP_BLKDEV;
2210 } else if (S_ISREG(inode->i_mode)) {
2211 p->bdev = inode->i_sb->s_bdev;
2212 inode_lock(inode);
2213 if (IS_SWAPFILE(inode))
2214 return -EBUSY;
2215 } else
2216 return -EINVAL;
2217
2218 return 0;
2219}
2220
2221static unsigned long read_swap_header(struct swap_info_struct *p,
2222 union swap_header *swap_header,
2223 struct inode *inode)
2224{
2225 int i;
2226 unsigned long maxpages;
2227 unsigned long swapfilepages;
2228 unsigned long last_page;
2229
2230 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2231 pr_err("Unable to find swap-space signature\n");
2232 return 0;
2233 }
2234
2235 /* swap partition endianess hack... */
2236 if (swab32(swap_header->info.version) == 1) {
2237 swab32s(&swap_header->info.version);
2238 swab32s(&swap_header->info.last_page);
2239 swab32s(&swap_header->info.nr_badpages);
2240 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2241 return 0;
2242 for (i = 0; i < swap_header->info.nr_badpages; i++)
2243 swab32s(&swap_header->info.badpages[i]);
2244 }
2245 /* Check the swap header's sub-version */
2246 if (swap_header->info.version != 1) {
2247 pr_warn("Unable to handle swap header version %d\n",
2248 swap_header->info.version);
2249 return 0;
2250 }
2251
2252 p->lowest_bit = 1;
2253 p->cluster_next = 1;
2254 p->cluster_nr = 0;
2255
2256 /*
2257 * Find out how many pages are allowed for a single swap
2258 * device. There are two limiting factors: 1) the number
2259 * of bits for the swap offset in the swp_entry_t type, and
2260 * 2) the number of bits in the swap pte as defined by the
2261 * different architectures. In order to find the
2262 * largest possible bit mask, a swap entry with swap type 0
2263 * and swap offset ~0UL is created, encoded to a swap pte,
2264 * decoded to a swp_entry_t again, and finally the swap
2265 * offset is extracted. This will mask all the bits from
2266 * the initial ~0UL mask that can't be encoded in either
2267 * the swp_entry_t or the architecture definition of a
2268 * swap pte.
2269 */
2270 maxpages = swp_offset(pte_to_swp_entry(
2271 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2272 last_page = swap_header->info.last_page;
2273 if (last_page > maxpages) {
2274 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2275 maxpages << (PAGE_SHIFT - 10),
2276 last_page << (PAGE_SHIFT - 10));
2277 }
2278 if (maxpages > last_page) {
2279 maxpages = last_page + 1;
2280 /* p->max is an unsigned int: don't overflow it */
2281 if ((unsigned int)maxpages == 0)
2282 maxpages = UINT_MAX;
2283 }
2284 p->highest_bit = maxpages - 1;
2285
2286 if (!maxpages)
2287 return 0;
2288 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2289 if (swapfilepages && maxpages > swapfilepages) {
2290 pr_warn("Swap area shorter than signature indicates\n");
2291 return 0;
2292 }
2293 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2294 return 0;
2295 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2296 return 0;
2297
2298 return maxpages;
2299}
2300
2301static int setup_swap_map_and_extents(struct swap_info_struct *p,
2302 union swap_header *swap_header,
2303 unsigned char *swap_map,
2304 struct swap_cluster_info *cluster_info,
2305 unsigned long maxpages,
2306 sector_t *span)
2307{
2308 int i;
2309 unsigned int nr_good_pages;
2310 int nr_extents;
2311 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2312 unsigned long idx = p->cluster_next / SWAPFILE_CLUSTER;
2313
2314 nr_good_pages = maxpages - 1; /* omit header page */
2315
2316 cluster_list_init(&p->free_clusters);
2317 cluster_list_init(&p->discard_clusters);
2318
2319 for (i = 0; i < swap_header->info.nr_badpages; i++) {
2320 unsigned int page_nr = swap_header->info.badpages[i];
2321 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2322 return -EINVAL;
2323 if (page_nr < maxpages) {
2324 swap_map[page_nr] = SWAP_MAP_BAD;
2325 nr_good_pages--;
2326 /*
2327 * Haven't marked the cluster free yet, no list
2328 * operation involved
2329 */
2330 inc_cluster_info_page(p, cluster_info, page_nr);
2331 }
2332 }
2333
2334 /* Haven't marked the cluster free yet, no list operation involved */
2335 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2336 inc_cluster_info_page(p, cluster_info, i);
2337
2338 if (nr_good_pages) {
2339 swap_map[0] = SWAP_MAP_BAD;
2340 /*
2341 * Not mark the cluster free yet, no list
2342 * operation involved
2343 */
2344 inc_cluster_info_page(p, cluster_info, 0);
2345 p->max = maxpages;
2346 p->pages = nr_good_pages;
2347 nr_extents = setup_swap_extents(p, span);
2348 if (nr_extents < 0)
2349 return nr_extents;
2350 nr_good_pages = p->pages;
2351 }
2352 if (!nr_good_pages) {
2353 pr_warn("Empty swap-file\n");
2354 return -EINVAL;
2355 }
2356
2357 if (!cluster_info)
2358 return nr_extents;
2359
2360 for (i = 0; i < nr_clusters; i++) {
2361 if (!cluster_count(&cluster_info[idx])) {
2362 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2363 cluster_list_add_tail(&p->free_clusters, cluster_info,
2364 idx);
2365 }
2366 idx++;
2367 if (idx == nr_clusters)
2368 idx = 0;
2369 }
2370 return nr_extents;
2371}
2372
2373/*
2374 * Helper to sys_swapon determining if a given swap
2375 * backing device queue supports DISCARD operations.
2376 */
2377static bool swap_discardable(struct swap_info_struct *si)
2378{
2379 struct request_queue *q = bdev_get_queue(si->bdev);
2380
2381 if (!q || !blk_queue_discard(q))
2382 return false;
2383
2384 return true;
2385}
2386
2387SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2388{
2389 struct swap_info_struct *p;
2390 struct filename *name;
2391 struct file *swap_file = NULL;
2392 struct address_space *mapping;
2393 int prio;
2394 int error;
2395 union swap_header *swap_header;
2396 int nr_extents;
2397 sector_t span;
2398 unsigned long maxpages;
2399 unsigned char *swap_map = NULL;
2400 struct swap_cluster_info *cluster_info = NULL;
2401 unsigned long *frontswap_map = NULL;
2402 struct page *page = NULL;
2403 struct inode *inode = NULL;
2404
2405 if (swap_flags & ~SWAP_FLAGS_VALID)
2406 return -EINVAL;
2407
2408 if (!capable(CAP_SYS_ADMIN))
2409 return -EPERM;
2410
2411 p = alloc_swap_info();
2412 if (IS_ERR(p))
2413 return PTR_ERR(p);
2414
2415 INIT_WORK(&p->discard_work, swap_discard_work);
2416
2417 name = getname(specialfile);
2418 if (IS_ERR(name)) {
2419 error = PTR_ERR(name);
2420 name = NULL;
2421 goto bad_swap;
2422 }
2423 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
2424 if (IS_ERR(swap_file)) {
2425 error = PTR_ERR(swap_file);
2426 swap_file = NULL;
2427 goto bad_swap;
2428 }
2429
2430 p->swap_file = swap_file;
2431 mapping = swap_file->f_mapping;
2432 inode = mapping->host;
2433
2434 /* If S_ISREG(inode->i_mode) will do inode_lock(inode); */
2435 error = claim_swapfile(p, inode);
2436 if (unlikely(error))
2437 goto bad_swap;
2438
2439 /*
2440 * Read the swap header.
2441 */
2442 if (!mapping->a_ops->readpage) {
2443 error = -EINVAL;
2444 goto bad_swap;
2445 }
2446 page = read_mapping_page(mapping, 0, swap_file);
2447 if (IS_ERR(page)) {
2448 error = PTR_ERR(page);
2449 goto bad_swap;
2450 }
2451 swap_header = kmap(page);
2452
2453 maxpages = read_swap_header(p, swap_header, inode);
2454 if (unlikely(!maxpages)) {
2455 error = -EINVAL;
2456 goto bad_swap;
2457 }
2458
2459 /* OK, set up the swap map and apply the bad block list */
2460 swap_map = vzalloc(maxpages);
2461 if (!swap_map) {
2462 error = -ENOMEM;
2463 goto bad_swap;
2464 }
2465
2466 if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))
2467 p->flags |= SWP_STABLE_WRITES;
2468
2469 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2470 int cpu;
2471
2472 p->flags |= SWP_SOLIDSTATE;
2473 /*
2474 * select a random position to start with to help wear leveling
2475 * SSD
2476 */
2477 p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
2478
2479 cluster_info = vzalloc(DIV_ROUND_UP(maxpages,
2480 SWAPFILE_CLUSTER) * sizeof(*cluster_info));
2481 if (!cluster_info) {
2482 error = -ENOMEM;
2483 goto bad_swap;
2484 }
2485 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
2486 if (!p->percpu_cluster) {
2487 error = -ENOMEM;
2488 goto bad_swap;
2489 }
2490 for_each_possible_cpu(cpu) {
2491 struct percpu_cluster *cluster;
2492 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
2493 cluster_set_null(&cluster->index);
2494 }
2495 }
2496
2497 error = swap_cgroup_swapon(p->type, maxpages);
2498 if (error)
2499 goto bad_swap;
2500
2501 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
2502 cluster_info, maxpages, &span);
2503 if (unlikely(nr_extents < 0)) {
2504 error = nr_extents;
2505 goto bad_swap;
2506 }
2507 /* frontswap enabled? set up bit-per-page map for frontswap */
2508 if (IS_ENABLED(CONFIG_FRONTSWAP))
2509 frontswap_map = vzalloc(BITS_TO_LONGS(maxpages) * sizeof(long));
2510
2511 if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
2512 /*
2513 * When discard is enabled for swap with no particular
2514 * policy flagged, we set all swap discard flags here in
2515 * order to sustain backward compatibility with older
2516 * swapon(8) releases.
2517 */
2518 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
2519 SWP_PAGE_DISCARD);
2520
2521 /*
2522 * By flagging sys_swapon, a sysadmin can tell us to
2523 * either do single-time area discards only, or to just
2524 * perform discards for released swap page-clusters.
2525 * Now it's time to adjust the p->flags accordingly.
2526 */
2527 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
2528 p->flags &= ~SWP_PAGE_DISCARD;
2529 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
2530 p->flags &= ~SWP_AREA_DISCARD;
2531
2532 /* issue a swapon-time discard if it's still required */
2533 if (p->flags & SWP_AREA_DISCARD) {
2534 int err = discard_swap(p);
2535 if (unlikely(err))
2536 pr_err("swapon: discard_swap(%p): %d\n",
2537 p, err);
2538 }
2539 }
2540
2541 mutex_lock(&swapon_mutex);
2542 prio = -1;
2543 if (swap_flags & SWAP_FLAG_PREFER)
2544 prio =
2545 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2546 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
2547
2548 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
2549 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
2550 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2551 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2552 (p->flags & SWP_DISCARDABLE) ? "D" : "",
2553 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
2554 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
2555 (frontswap_map) ? "FS" : "");
2556
2557 mutex_unlock(&swapon_mutex);
2558 atomic_inc(&proc_poll_event);
2559 wake_up_interruptible(&proc_poll_wait);
2560
2561 if (S_ISREG(inode->i_mode))
2562 inode->i_flags |= S_SWAPFILE;
2563 error = 0;
2564 goto out;
2565bad_swap:
2566 free_percpu(p->percpu_cluster);
2567 p->percpu_cluster = NULL;
2568 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
2569 set_blocksize(p->bdev, p->old_block_size);
2570 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2571 }
2572 destroy_swap_extents(p);
2573 swap_cgroup_swapoff(p->type);
2574 spin_lock(&swap_lock);
2575 p->swap_file = NULL;
2576 p->flags = 0;
2577 spin_unlock(&swap_lock);
2578 vfree(swap_map);
2579 vfree(cluster_info);
2580 if (swap_file) {
2581 if (inode && S_ISREG(inode->i_mode)) {
2582 inode_unlock(inode);
2583 inode = NULL;
2584 }
2585 filp_close(swap_file, NULL);
2586 }
2587out:
2588 if (page && !IS_ERR(page)) {
2589 kunmap(page);
2590 put_page(page);
2591 }
2592 if (name)
2593 putname(name);
2594 if (inode && S_ISREG(inode->i_mode))
2595 inode_unlock(inode);
2596 return error;
2597}
2598
2599void si_swapinfo(struct sysinfo *val)
2600{
2601 unsigned int type;
2602 unsigned long nr_to_be_unused = 0;
2603
2604 spin_lock(&swap_lock);
2605 for (type = 0; type < nr_swapfiles; type++) {
2606 struct swap_info_struct *si = swap_info[type];
2607
2608 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2609 nr_to_be_unused += si->inuse_pages;
2610 }
2611 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
2612 val->totalswap = total_swap_pages + nr_to_be_unused;
2613 spin_unlock(&swap_lock);
2614}
2615
2616/*
2617 * Verify that a swap entry is valid and increment its swap map count.
2618 *
2619 * Returns error code in following case.
2620 * - success -> 0
2621 * - swp_entry is invalid -> EINVAL
2622 * - swp_entry is migration entry -> EINVAL
2623 * - swap-cache reference is requested but there is already one. -> EEXIST
2624 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2625 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2626 */
2627static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2628{
2629 struct swap_info_struct *p;
2630 unsigned long offset, type;
2631 unsigned char count;
2632 unsigned char has_cache;
2633 int err = -EINVAL;
2634
2635 if (non_swap_entry(entry))
2636 goto out;
2637
2638 type = swp_type(entry);
2639 if (type >= nr_swapfiles)
2640 goto bad_file;
2641 p = swap_info[type];
2642 offset = swp_offset(entry);
2643
2644 spin_lock(&p->lock);
2645 if (unlikely(offset >= p->max))
2646 goto unlock_out;
2647
2648 count = p->swap_map[offset];
2649
2650 /*
2651 * swapin_readahead() doesn't check if a swap entry is valid, so the
2652 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
2653 */
2654 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
2655 err = -ENOENT;
2656 goto unlock_out;
2657 }
2658
2659 has_cache = count & SWAP_HAS_CACHE;
2660 count &= ~SWAP_HAS_CACHE;
2661 err = 0;
2662
2663 if (usage == SWAP_HAS_CACHE) {
2664
2665 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2666 if (!has_cache && count)
2667 has_cache = SWAP_HAS_CACHE;
2668 else if (has_cache) /* someone else added cache */
2669 err = -EEXIST;
2670 else /* no users remaining */
2671 err = -ENOENT;
2672
2673 } else if (count || has_cache) {
2674
2675 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2676 count += usage;
2677 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2678 err = -EINVAL;
2679 else if (swap_count_continued(p, offset, count))
2680 count = COUNT_CONTINUED;
2681 else
2682 err = -ENOMEM;
2683 } else
2684 err = -ENOENT; /* unused swap entry */
2685
2686 p->swap_map[offset] = count | has_cache;
2687
2688unlock_out:
2689 spin_unlock(&p->lock);
2690out:
2691 return err;
2692
2693bad_file:
2694 pr_err("swap_dup: %s%08lx\n", Bad_file, entry.val);
2695 goto out;
2696}
2697
2698/*
2699 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2700 * (in which case its reference count is never incremented).
2701 */
2702void swap_shmem_alloc(swp_entry_t entry)
2703{
2704 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2705}
2706
2707/*
2708 * Increase reference count of swap entry by 1.
2709 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2710 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2711 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2712 * might occur if a page table entry has got corrupted.
2713 */
2714int swap_duplicate(swp_entry_t entry)
2715{
2716 int err = 0;
2717
2718 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2719 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2720 return err;
2721}
2722
2723/*
2724 * @entry: swap entry for which we allocate swap cache.
2725 *
2726 * Called when allocating swap cache for existing swap entry,
2727 * This can return error codes. Returns 0 at success.
2728 * -EBUSY means there is a swap cache.
2729 * Note: return code is different from swap_duplicate().
2730 */
2731int swapcache_prepare(swp_entry_t entry)
2732{
2733 return __swap_duplicate(entry, SWAP_HAS_CACHE);
2734}
2735
2736struct swap_info_struct *page_swap_info(struct page *page)
2737{
2738 swp_entry_t swap = { .val = page_private(page) };
2739 return swap_info[swp_type(swap)];
2740}
2741
2742/*
2743 * out-of-line __page_file_ methods to avoid include hell.
2744 */
2745struct address_space *__page_file_mapping(struct page *page)
2746{
2747 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
2748 return page_swap_info(page)->swap_file->f_mapping;
2749}
2750EXPORT_SYMBOL_GPL(__page_file_mapping);
2751
2752pgoff_t __page_file_index(struct page *page)
2753{
2754 swp_entry_t swap = { .val = page_private(page) };
2755 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
2756 return swp_offset(swap);
2757}
2758EXPORT_SYMBOL_GPL(__page_file_index);
2759
2760/*
2761 * add_swap_count_continuation - called when a swap count is duplicated
2762 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2763 * page of the original vmalloc'ed swap_map, to hold the continuation count
2764 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2765 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2766 *
2767 * These continuation pages are seldom referenced: the common paths all work
2768 * on the original swap_map, only referring to a continuation page when the
2769 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2770 *
2771 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2772 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2773 * can be called after dropping locks.
2774 */
2775int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2776{
2777 struct swap_info_struct *si;
2778 struct page *head;
2779 struct page *page;
2780 struct page *list_page;
2781 pgoff_t offset;
2782 unsigned char count;
2783
2784 /*
2785 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2786 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2787 */
2788 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2789
2790 si = swap_info_get(entry);
2791 if (!si) {
2792 /*
2793 * An acceptable race has occurred since the failing
2794 * __swap_duplicate(): the swap entry has been freed,
2795 * perhaps even the whole swap_map cleared for swapoff.
2796 */
2797 goto outer;
2798 }
2799
2800 offset = swp_offset(entry);
2801 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2802
2803 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2804 /*
2805 * The higher the swap count, the more likely it is that tasks
2806 * will race to add swap count continuation: we need to avoid
2807 * over-provisioning.
2808 */
2809 goto out;
2810 }
2811
2812 if (!page) {
2813 spin_unlock(&si->lock);
2814 return -ENOMEM;
2815 }
2816
2817 /*
2818 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2819 * no architecture is using highmem pages for kernel page tables: so it
2820 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
2821 */
2822 head = vmalloc_to_page(si->swap_map + offset);
2823 offset &= ~PAGE_MASK;
2824
2825 /*
2826 * Page allocation does not initialize the page's lru field,
2827 * but it does always reset its private field.
2828 */
2829 if (!page_private(head)) {
2830 BUG_ON(count & COUNT_CONTINUED);
2831 INIT_LIST_HEAD(&head->lru);
2832 set_page_private(head, SWP_CONTINUED);
2833 si->flags |= SWP_CONTINUED;
2834 }
2835
2836 list_for_each_entry(list_page, &head->lru, lru) {
2837 unsigned char *map;
2838
2839 /*
2840 * If the previous map said no continuation, but we've found
2841 * a continuation page, free our allocation and use this one.
2842 */
2843 if (!(count & COUNT_CONTINUED))
2844 goto out;
2845
2846 map = kmap_atomic(list_page) + offset;
2847 count = *map;
2848 kunmap_atomic(map);
2849
2850 /*
2851 * If this continuation count now has some space in it,
2852 * free our allocation and use this one.
2853 */
2854 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2855 goto out;
2856 }
2857
2858 list_add_tail(&page->lru, &head->lru);
2859 page = NULL; /* now it's attached, don't free it */
2860out:
2861 spin_unlock(&si->lock);
2862outer:
2863 if (page)
2864 __free_page(page);
2865 return 0;
2866}
2867
2868/*
2869 * swap_count_continued - when the original swap_map count is incremented
2870 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2871 * into, carry if so, or else fail until a new continuation page is allocated;
2872 * when the original swap_map count is decremented from 0 with continuation,
2873 * borrow from the continuation and report whether it still holds more.
2874 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2875 */
2876static bool swap_count_continued(struct swap_info_struct *si,
2877 pgoff_t offset, unsigned char count)
2878{
2879 struct page *head;
2880 struct page *page;
2881 unsigned char *map;
2882
2883 head = vmalloc_to_page(si->swap_map + offset);
2884 if (page_private(head) != SWP_CONTINUED) {
2885 BUG_ON(count & COUNT_CONTINUED);
2886 return false; /* need to add count continuation */
2887 }
2888
2889 offset &= ~PAGE_MASK;
2890 page = list_entry(head->lru.next, struct page, lru);
2891 map = kmap_atomic(page) + offset;
2892
2893 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2894 goto init_map; /* jump over SWAP_CONT_MAX checks */
2895
2896 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2897 /*
2898 * Think of how you add 1 to 999
2899 */
2900 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2901 kunmap_atomic(map);
2902 page = list_entry(page->lru.next, struct page, lru);
2903 BUG_ON(page == head);
2904 map = kmap_atomic(page) + offset;
2905 }
2906 if (*map == SWAP_CONT_MAX) {
2907 kunmap_atomic(map);
2908 page = list_entry(page->lru.next, struct page, lru);
2909 if (page == head)
2910 return false; /* add count continuation */
2911 map = kmap_atomic(page) + offset;
2912init_map: *map = 0; /* we didn't zero the page */
2913 }
2914 *map += 1;
2915 kunmap_atomic(map);
2916 page = list_entry(page->lru.prev, struct page, lru);
2917 while (page != head) {
2918 map = kmap_atomic(page) + offset;
2919 *map = COUNT_CONTINUED;
2920 kunmap_atomic(map);
2921 page = list_entry(page->lru.prev, struct page, lru);
2922 }
2923 return true; /* incremented */
2924
2925 } else { /* decrementing */
2926 /*
2927 * Think of how you subtract 1 from 1000
2928 */
2929 BUG_ON(count != COUNT_CONTINUED);
2930 while (*map == COUNT_CONTINUED) {
2931 kunmap_atomic(map);
2932 page = list_entry(page->lru.next, struct page, lru);
2933 BUG_ON(page == head);
2934 map = kmap_atomic(page) + offset;
2935 }
2936 BUG_ON(*map == 0);
2937 *map -= 1;
2938 if (*map == 0)
2939 count = 0;
2940 kunmap_atomic(map);
2941 page = list_entry(page->lru.prev, struct page, lru);
2942 while (page != head) {
2943 map = kmap_atomic(page) + offset;
2944 *map = SWAP_CONT_MAX | count;
2945 count = COUNT_CONTINUED;
2946 kunmap_atomic(map);
2947 page = list_entry(page->lru.prev, struct page, lru);
2948 }
2949 return count == COUNT_CONTINUED;
2950 }
2951}
2952
2953/*
2954 * free_swap_count_continuations - swapoff free all the continuation pages
2955 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2956 */
2957static void free_swap_count_continuations(struct swap_info_struct *si)
2958{
2959 pgoff_t offset;
2960
2961 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2962 struct page *head;
2963 head = vmalloc_to_page(si->swap_map + offset);
2964 if (page_private(head)) {
2965 struct page *page, *next;
2966
2967 list_for_each_entry_safe(page, next, &head->lru, lru) {
2968 list_del(&page->lru);
2969 __free_page(page);
2970 }
2971 }
2972 }
2973}