Merge tag 'for-linus-2022102101' of git://git.kernel.org/pub/scm/linux/kernel/git...
[platform/kernel/linux-starfive.git] / mm / swapfile.c
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/blkdev.h>
10 #include <linux/mm.h>
11 #include <linux/sched/mm.h>
12 #include <linux/sched/task.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mman.h>
15 #include <linux/slab.h>
16 #include <linux/kernel_stat.h>
17 #include <linux/swap.h>
18 #include <linux/vmalloc.h>
19 #include <linux/pagemap.h>
20 #include <linux/namei.h>
21 #include <linux/shmem_fs.h>
22 #include <linux/blk-cgroup.h>
23 #include <linux/random.h>
24 #include <linux/writeback.h>
25 #include <linux/proc_fs.h>
26 #include <linux/seq_file.h>
27 #include <linux/init.h>
28 #include <linux/ksm.h>
29 #include <linux/rmap.h>
30 #include <linux/security.h>
31 #include <linux/backing-dev.h>
32 #include <linux/mutex.h>
33 #include <linux/capability.h>
34 #include <linux/syscalls.h>
35 #include <linux/memcontrol.h>
36 #include <linux/poll.h>
37 #include <linux/oom.h>
38 #include <linux/frontswap.h>
39 #include <linux/swapfile.h>
40 #include <linux/export.h>
41 #include <linux/swap_slots.h>
42 #include <linux/sort.h>
43 #include <linux/completion.h>
44
45 #include <asm/tlbflush.h>
46 #include <linux/swapops.h>
47 #include <linux/swap_cgroup.h>
48 #include "swap.h"
49
50 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
51                                  unsigned char);
52 static void free_swap_count_continuations(struct swap_info_struct *);
53
54 static DEFINE_SPINLOCK(swap_lock);
55 static unsigned int nr_swapfiles;
56 atomic_long_t nr_swap_pages;
57 /*
58  * Some modules use swappable objects and may try to swap them out under
59  * memory pressure (via the shrinker). Before doing so, they may wish to
60  * check to see if any swap space is available.
61  */
62 EXPORT_SYMBOL_GPL(nr_swap_pages);
63 /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
64 long total_swap_pages;
65 static int least_priority = -1;
66 unsigned long swapfile_maximum_size;
67 #ifdef CONFIG_MIGRATION
68 bool swap_migration_ad_supported;
69 #endif  /* CONFIG_MIGRATION */
70
71 static const char Bad_file[] = "Bad swap file entry ";
72 static const char Unused_file[] = "Unused swap file entry ";
73 static const char Bad_offset[] = "Bad swap offset entry ";
74 static const char Unused_offset[] = "Unused swap offset entry ";
75
76 /*
77  * all active swap_info_structs
78  * protected with swap_lock, and ordered by priority.
79  */
80 static PLIST_HEAD(swap_active_head);
81
82 /*
83  * all available (active, not full) swap_info_structs
84  * protected with swap_avail_lock, ordered by priority.
85  * This is used by folio_alloc_swap() instead of swap_active_head
86  * because swap_active_head includes all swap_info_structs,
87  * but folio_alloc_swap() doesn't need to look at full ones.
88  * This uses its own lock instead of swap_lock because when a
89  * swap_info_struct changes between not-full/full, it needs to
90  * add/remove itself to/from this list, but the swap_info_struct->lock
91  * is held and the locking order requires swap_lock to be taken
92  * before any swap_info_struct->lock.
93  */
94 static struct plist_head *swap_avail_heads;
95 static DEFINE_SPINLOCK(swap_avail_lock);
96
97 struct swap_info_struct *swap_info[MAX_SWAPFILES];
98
99 static DEFINE_MUTEX(swapon_mutex);
100
101 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
102 /* Activity counter to indicate that a swapon or swapoff has occurred */
103 static atomic_t proc_poll_event = ATOMIC_INIT(0);
104
105 atomic_t nr_rotate_swap = ATOMIC_INIT(0);
106
107 static struct swap_info_struct *swap_type_to_swap_info(int type)
108 {
109         if (type >= MAX_SWAPFILES)
110                 return NULL;
111
112         return READ_ONCE(swap_info[type]); /* rcu_dereference() */
113 }
114
115 static inline unsigned char swap_count(unsigned char ent)
116 {
117         return ent & ~SWAP_HAS_CACHE;   /* may include COUNT_CONTINUED flag */
118 }
119
120 /* Reclaim the swap entry anyway if possible */
121 #define TTRS_ANYWAY             0x1
122 /*
123  * Reclaim the swap entry if there are no more mappings of the
124  * corresponding page
125  */
126 #define TTRS_UNMAPPED           0x2
127 /* Reclaim the swap entry if swap is getting full*/
128 #define TTRS_FULL               0x4
129
130 /* returns 1 if swap entry is freed */
131 static int __try_to_reclaim_swap(struct swap_info_struct *si,
132                                  unsigned long offset, unsigned long flags)
133 {
134         swp_entry_t entry = swp_entry(si->type, offset);
135         struct folio *folio;
136         int ret = 0;
137
138         folio = filemap_get_folio(swap_address_space(entry), offset);
139         if (!folio)
140                 return 0;
141         /*
142          * When this function is called from scan_swap_map_slots() and it's
143          * called by vmscan.c at reclaiming folios. So we hold a folio lock
144          * here. We have to use trylock for avoiding deadlock. This is a special
145          * case and you should use folio_free_swap() with explicit folio_lock()
146          * in usual operations.
147          */
148         if (folio_trylock(folio)) {
149                 if ((flags & TTRS_ANYWAY) ||
150                     ((flags & TTRS_UNMAPPED) && !folio_mapped(folio)) ||
151                     ((flags & TTRS_FULL) && mem_cgroup_swap_full(folio)))
152                         ret = folio_free_swap(folio);
153                 folio_unlock(folio);
154         }
155         folio_put(folio);
156         return ret;
157 }
158
159 static inline struct swap_extent *first_se(struct swap_info_struct *sis)
160 {
161         struct rb_node *rb = rb_first(&sis->swap_extent_root);
162         return rb_entry(rb, struct swap_extent, rb_node);
163 }
164
165 static inline struct swap_extent *next_se(struct swap_extent *se)
166 {
167         struct rb_node *rb = rb_next(&se->rb_node);
168         return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
169 }
170
171 /*
172  * swapon tell device that all the old swap contents can be discarded,
173  * to allow the swap device to optimize its wear-levelling.
174  */
175 static int discard_swap(struct swap_info_struct *si)
176 {
177         struct swap_extent *se;
178         sector_t start_block;
179         sector_t nr_blocks;
180         int err = 0;
181
182         /* Do not discard the swap header page! */
183         se = first_se(si);
184         start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
185         nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
186         if (nr_blocks) {
187                 err = blkdev_issue_discard(si->bdev, start_block,
188                                 nr_blocks, GFP_KERNEL);
189                 if (err)
190                         return err;
191                 cond_resched();
192         }
193
194         for (se = next_se(se); se; se = next_se(se)) {
195                 start_block = se->start_block << (PAGE_SHIFT - 9);
196                 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
197
198                 err = blkdev_issue_discard(si->bdev, start_block,
199                                 nr_blocks, GFP_KERNEL);
200                 if (err)
201                         break;
202
203                 cond_resched();
204         }
205         return err;             /* That will often be -EOPNOTSUPP */
206 }
207
208 static struct swap_extent *
209 offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
210 {
211         struct swap_extent *se;
212         struct rb_node *rb;
213
214         rb = sis->swap_extent_root.rb_node;
215         while (rb) {
216                 se = rb_entry(rb, struct swap_extent, rb_node);
217                 if (offset < se->start_page)
218                         rb = rb->rb_left;
219                 else if (offset >= se->start_page + se->nr_pages)
220                         rb = rb->rb_right;
221                 else
222                         return se;
223         }
224         /* It *must* be present */
225         BUG();
226 }
227
228 sector_t swap_page_sector(struct page *page)
229 {
230         struct swap_info_struct *sis = page_swap_info(page);
231         struct swap_extent *se;
232         sector_t sector;
233         pgoff_t offset;
234
235         offset = __page_file_index(page);
236         se = offset_to_swap_extent(sis, offset);
237         sector = se->start_block + (offset - se->start_page);
238         return sector << (PAGE_SHIFT - 9);
239 }
240
241 /*
242  * swap allocation tell device that a cluster of swap can now be discarded,
243  * to allow the swap device to optimize its wear-levelling.
244  */
245 static void discard_swap_cluster(struct swap_info_struct *si,
246                                  pgoff_t start_page, pgoff_t nr_pages)
247 {
248         struct swap_extent *se = offset_to_swap_extent(si, start_page);
249
250         while (nr_pages) {
251                 pgoff_t offset = start_page - se->start_page;
252                 sector_t start_block = se->start_block + offset;
253                 sector_t nr_blocks = se->nr_pages - offset;
254
255                 if (nr_blocks > nr_pages)
256                         nr_blocks = nr_pages;
257                 start_page += nr_blocks;
258                 nr_pages -= nr_blocks;
259
260                 start_block <<= PAGE_SHIFT - 9;
261                 nr_blocks <<= PAGE_SHIFT - 9;
262                 if (blkdev_issue_discard(si->bdev, start_block,
263                                         nr_blocks, GFP_NOIO))
264                         break;
265
266                 se = next_se(se);
267         }
268 }
269
270 #ifdef CONFIG_THP_SWAP
271 #define SWAPFILE_CLUSTER        HPAGE_PMD_NR
272
273 #define swap_entry_size(size)   (size)
274 #else
275 #define SWAPFILE_CLUSTER        256
276
277 /*
278  * Define swap_entry_size() as constant to let compiler to optimize
279  * out some code if !CONFIG_THP_SWAP
280  */
281 #define swap_entry_size(size)   1
282 #endif
283 #define LATENCY_LIMIT           256
284
285 static inline void cluster_set_flag(struct swap_cluster_info *info,
286         unsigned int flag)
287 {
288         info->flags = flag;
289 }
290
291 static inline unsigned int cluster_count(struct swap_cluster_info *info)
292 {
293         return info->data;
294 }
295
296 static inline void cluster_set_count(struct swap_cluster_info *info,
297                                      unsigned int c)
298 {
299         info->data = c;
300 }
301
302 static inline void cluster_set_count_flag(struct swap_cluster_info *info,
303                                          unsigned int c, unsigned int f)
304 {
305         info->flags = f;
306         info->data = c;
307 }
308
309 static inline unsigned int cluster_next(struct swap_cluster_info *info)
310 {
311         return info->data;
312 }
313
314 static inline void cluster_set_next(struct swap_cluster_info *info,
315                                     unsigned int n)
316 {
317         info->data = n;
318 }
319
320 static inline void cluster_set_next_flag(struct swap_cluster_info *info,
321                                          unsigned int n, unsigned int f)
322 {
323         info->flags = f;
324         info->data = n;
325 }
326
327 static inline bool cluster_is_free(struct swap_cluster_info *info)
328 {
329         return info->flags & CLUSTER_FLAG_FREE;
330 }
331
332 static inline bool cluster_is_null(struct swap_cluster_info *info)
333 {
334         return info->flags & CLUSTER_FLAG_NEXT_NULL;
335 }
336
337 static inline void cluster_set_null(struct swap_cluster_info *info)
338 {
339         info->flags = CLUSTER_FLAG_NEXT_NULL;
340         info->data = 0;
341 }
342
343 static inline bool cluster_is_huge(struct swap_cluster_info *info)
344 {
345         if (IS_ENABLED(CONFIG_THP_SWAP))
346                 return info->flags & CLUSTER_FLAG_HUGE;
347         return false;
348 }
349
350 static inline void cluster_clear_huge(struct swap_cluster_info *info)
351 {
352         info->flags &= ~CLUSTER_FLAG_HUGE;
353 }
354
355 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
356                                                      unsigned long offset)
357 {
358         struct swap_cluster_info *ci;
359
360         ci = si->cluster_info;
361         if (ci) {
362                 ci += offset / SWAPFILE_CLUSTER;
363                 spin_lock(&ci->lock);
364         }
365         return ci;
366 }
367
368 static inline void unlock_cluster(struct swap_cluster_info *ci)
369 {
370         if (ci)
371                 spin_unlock(&ci->lock);
372 }
373
374 /*
375  * Determine the locking method in use for this device.  Return
376  * swap_cluster_info if SSD-style cluster-based locking is in place.
377  */
378 static inline struct swap_cluster_info *lock_cluster_or_swap_info(
379                 struct swap_info_struct *si, unsigned long offset)
380 {
381         struct swap_cluster_info *ci;
382
383         /* Try to use fine-grained SSD-style locking if available: */
384         ci = lock_cluster(si, offset);
385         /* Otherwise, fall back to traditional, coarse locking: */
386         if (!ci)
387                 spin_lock(&si->lock);
388
389         return ci;
390 }
391
392 static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
393                                                struct swap_cluster_info *ci)
394 {
395         if (ci)
396                 unlock_cluster(ci);
397         else
398                 spin_unlock(&si->lock);
399 }
400
401 static inline bool cluster_list_empty(struct swap_cluster_list *list)
402 {
403         return cluster_is_null(&list->head);
404 }
405
406 static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
407 {
408         return cluster_next(&list->head);
409 }
410
411 static void cluster_list_init(struct swap_cluster_list *list)
412 {
413         cluster_set_null(&list->head);
414         cluster_set_null(&list->tail);
415 }
416
417 static void cluster_list_add_tail(struct swap_cluster_list *list,
418                                   struct swap_cluster_info *ci,
419                                   unsigned int idx)
420 {
421         if (cluster_list_empty(list)) {
422                 cluster_set_next_flag(&list->head, idx, 0);
423                 cluster_set_next_flag(&list->tail, idx, 0);
424         } else {
425                 struct swap_cluster_info *ci_tail;
426                 unsigned int tail = cluster_next(&list->tail);
427
428                 /*
429                  * Nested cluster lock, but both cluster locks are
430                  * only acquired when we held swap_info_struct->lock
431                  */
432                 ci_tail = ci + tail;
433                 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
434                 cluster_set_next(ci_tail, idx);
435                 spin_unlock(&ci_tail->lock);
436                 cluster_set_next_flag(&list->tail, idx, 0);
437         }
438 }
439
440 static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
441                                            struct swap_cluster_info *ci)
442 {
443         unsigned int idx;
444
445         idx = cluster_next(&list->head);
446         if (cluster_next(&list->tail) == idx) {
447                 cluster_set_null(&list->head);
448                 cluster_set_null(&list->tail);
449         } else
450                 cluster_set_next_flag(&list->head,
451                                       cluster_next(&ci[idx]), 0);
452
453         return idx;
454 }
455
456 /* Add a cluster to discard list and schedule it to do discard */
457 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
458                 unsigned int idx)
459 {
460         /*
461          * If scan_swap_map_slots() can't find a free cluster, it will check
462          * si->swap_map directly. To make sure the discarding cluster isn't
463          * taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
464          * It will be cleared after discard
465          */
466         memset(si->swap_map + idx * SWAPFILE_CLUSTER,
467                         SWAP_MAP_BAD, SWAPFILE_CLUSTER);
468
469         cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
470
471         schedule_work(&si->discard_work);
472 }
473
474 static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
475 {
476         struct swap_cluster_info *ci = si->cluster_info;
477
478         cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
479         cluster_list_add_tail(&si->free_clusters, ci, idx);
480 }
481
482 /*
483  * Doing discard actually. After a cluster discard is finished, the cluster
484  * will be added to free cluster list. caller should hold si->lock.
485 */
486 static void swap_do_scheduled_discard(struct swap_info_struct *si)
487 {
488         struct swap_cluster_info *info, *ci;
489         unsigned int idx;
490
491         info = si->cluster_info;
492
493         while (!cluster_list_empty(&si->discard_clusters)) {
494                 idx = cluster_list_del_first(&si->discard_clusters, info);
495                 spin_unlock(&si->lock);
496
497                 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
498                                 SWAPFILE_CLUSTER);
499
500                 spin_lock(&si->lock);
501                 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
502                 __free_cluster(si, idx);
503                 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
504                                 0, SWAPFILE_CLUSTER);
505                 unlock_cluster(ci);
506         }
507 }
508
509 static void swap_discard_work(struct work_struct *work)
510 {
511         struct swap_info_struct *si;
512
513         si = container_of(work, struct swap_info_struct, discard_work);
514
515         spin_lock(&si->lock);
516         swap_do_scheduled_discard(si);
517         spin_unlock(&si->lock);
518 }
519
520 static void swap_users_ref_free(struct percpu_ref *ref)
521 {
522         struct swap_info_struct *si;
523
524         si = container_of(ref, struct swap_info_struct, users);
525         complete(&si->comp);
526 }
527
528 static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
529 {
530         struct swap_cluster_info *ci = si->cluster_info;
531
532         VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
533         cluster_list_del_first(&si->free_clusters, ci);
534         cluster_set_count_flag(ci + idx, 0, 0);
535 }
536
537 static void free_cluster(struct swap_info_struct *si, unsigned long idx)
538 {
539         struct swap_cluster_info *ci = si->cluster_info + idx;
540
541         VM_BUG_ON(cluster_count(ci) != 0);
542         /*
543          * If the swap is discardable, prepare discard the cluster
544          * instead of free it immediately. The cluster will be freed
545          * after discard.
546          */
547         if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
548             (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
549                 swap_cluster_schedule_discard(si, idx);
550                 return;
551         }
552
553         __free_cluster(si, idx);
554 }
555
556 /*
557  * The cluster corresponding to page_nr will be used. The cluster will be
558  * removed from free cluster list and its usage counter will be increased.
559  */
560 static void inc_cluster_info_page(struct swap_info_struct *p,
561         struct swap_cluster_info *cluster_info, unsigned long page_nr)
562 {
563         unsigned long idx = page_nr / SWAPFILE_CLUSTER;
564
565         if (!cluster_info)
566                 return;
567         if (cluster_is_free(&cluster_info[idx]))
568                 alloc_cluster(p, idx);
569
570         VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
571         cluster_set_count(&cluster_info[idx],
572                 cluster_count(&cluster_info[idx]) + 1);
573 }
574
575 /*
576  * The cluster corresponding to page_nr decreases one usage. If the usage
577  * counter becomes 0, which means no page in the cluster is in using, we can
578  * optionally discard the cluster and add it to free cluster list.
579  */
580 static void dec_cluster_info_page(struct swap_info_struct *p,
581         struct swap_cluster_info *cluster_info, unsigned long page_nr)
582 {
583         unsigned long idx = page_nr / SWAPFILE_CLUSTER;
584
585         if (!cluster_info)
586                 return;
587
588         VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
589         cluster_set_count(&cluster_info[idx],
590                 cluster_count(&cluster_info[idx]) - 1);
591
592         if (cluster_count(&cluster_info[idx]) == 0)
593                 free_cluster(p, idx);
594 }
595
596 /*
597  * It's possible scan_swap_map_slots() uses a free cluster in the middle of free
598  * cluster list. Avoiding such abuse to avoid list corruption.
599  */
600 static bool
601 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
602         unsigned long offset)
603 {
604         struct percpu_cluster *percpu_cluster;
605         bool conflict;
606
607         offset /= SWAPFILE_CLUSTER;
608         conflict = !cluster_list_empty(&si->free_clusters) &&
609                 offset != cluster_list_first(&si->free_clusters) &&
610                 cluster_is_free(&si->cluster_info[offset]);
611
612         if (!conflict)
613                 return false;
614
615         percpu_cluster = this_cpu_ptr(si->percpu_cluster);
616         cluster_set_null(&percpu_cluster->index);
617         return true;
618 }
619
620 /*
621  * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
622  * might involve allocating a new cluster for current CPU too.
623  */
624 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
625         unsigned long *offset, unsigned long *scan_base)
626 {
627         struct percpu_cluster *cluster;
628         struct swap_cluster_info *ci;
629         unsigned long tmp, max;
630
631 new_cluster:
632         cluster = this_cpu_ptr(si->percpu_cluster);
633         if (cluster_is_null(&cluster->index)) {
634                 if (!cluster_list_empty(&si->free_clusters)) {
635                         cluster->index = si->free_clusters.head;
636                         cluster->next = cluster_next(&cluster->index) *
637                                         SWAPFILE_CLUSTER;
638                 } else if (!cluster_list_empty(&si->discard_clusters)) {
639                         /*
640                          * we don't have free cluster but have some clusters in
641                          * discarding, do discard now and reclaim them, then
642                          * reread cluster_next_cpu since we dropped si->lock
643                          */
644                         swap_do_scheduled_discard(si);
645                         *scan_base = this_cpu_read(*si->cluster_next_cpu);
646                         *offset = *scan_base;
647                         goto new_cluster;
648                 } else
649                         return false;
650         }
651
652         /*
653          * Other CPUs can use our cluster if they can't find a free cluster,
654          * check if there is still free entry in the cluster
655          */
656         tmp = cluster->next;
657         max = min_t(unsigned long, si->max,
658                     (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
659         if (tmp < max) {
660                 ci = lock_cluster(si, tmp);
661                 while (tmp < max) {
662                         if (!si->swap_map[tmp])
663                                 break;
664                         tmp++;
665                 }
666                 unlock_cluster(ci);
667         }
668         if (tmp >= max) {
669                 cluster_set_null(&cluster->index);
670                 goto new_cluster;
671         }
672         cluster->next = tmp + 1;
673         *offset = tmp;
674         *scan_base = tmp;
675         return true;
676 }
677
678 static void __del_from_avail_list(struct swap_info_struct *p)
679 {
680         int nid;
681
682         for_each_node(nid)
683                 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
684 }
685
686 static void del_from_avail_list(struct swap_info_struct *p)
687 {
688         spin_lock(&swap_avail_lock);
689         __del_from_avail_list(p);
690         spin_unlock(&swap_avail_lock);
691 }
692
693 static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
694                              unsigned int nr_entries)
695 {
696         unsigned int end = offset + nr_entries - 1;
697
698         if (offset == si->lowest_bit)
699                 si->lowest_bit += nr_entries;
700         if (end == si->highest_bit)
701                 WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
702         WRITE_ONCE(si->inuse_pages, si->inuse_pages + nr_entries);
703         if (si->inuse_pages == si->pages) {
704                 si->lowest_bit = si->max;
705                 si->highest_bit = 0;
706                 del_from_avail_list(si);
707         }
708 }
709
710 static void add_to_avail_list(struct swap_info_struct *p)
711 {
712         int nid;
713
714         spin_lock(&swap_avail_lock);
715         for_each_node(nid) {
716                 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
717                 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
718         }
719         spin_unlock(&swap_avail_lock);
720 }
721
722 static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
723                             unsigned int nr_entries)
724 {
725         unsigned long begin = offset;
726         unsigned long end = offset + nr_entries - 1;
727         void (*swap_slot_free_notify)(struct block_device *, unsigned long);
728
729         if (offset < si->lowest_bit)
730                 si->lowest_bit = offset;
731         if (end > si->highest_bit) {
732                 bool was_full = !si->highest_bit;
733
734                 WRITE_ONCE(si->highest_bit, end);
735                 if (was_full && (si->flags & SWP_WRITEOK))
736                         add_to_avail_list(si);
737         }
738         atomic_long_add(nr_entries, &nr_swap_pages);
739         WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries);
740         if (si->flags & SWP_BLKDEV)
741                 swap_slot_free_notify =
742                         si->bdev->bd_disk->fops->swap_slot_free_notify;
743         else
744                 swap_slot_free_notify = NULL;
745         while (offset <= end) {
746                 arch_swap_invalidate_page(si->type, offset);
747                 frontswap_invalidate_page(si->type, offset);
748                 if (swap_slot_free_notify)
749                         swap_slot_free_notify(si->bdev, offset);
750                 offset++;
751         }
752         clear_shadow_from_swap_cache(si->type, begin, end);
753 }
754
755 static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
756 {
757         unsigned long prev;
758
759         if (!(si->flags & SWP_SOLIDSTATE)) {
760                 si->cluster_next = next;
761                 return;
762         }
763
764         prev = this_cpu_read(*si->cluster_next_cpu);
765         /*
766          * Cross the swap address space size aligned trunk, choose
767          * another trunk randomly to avoid lock contention on swap
768          * address space if possible.
769          */
770         if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) !=
771             (next >> SWAP_ADDRESS_SPACE_SHIFT)) {
772                 /* No free swap slots available */
773                 if (si->highest_bit <= si->lowest_bit)
774                         return;
775                 next = si->lowest_bit +
776                         prandom_u32_max(si->highest_bit - si->lowest_bit + 1);
777                 next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
778                 next = max_t(unsigned int, next, si->lowest_bit);
779         }
780         this_cpu_write(*si->cluster_next_cpu, next);
781 }
782
783 static bool swap_offset_available_and_locked(struct swap_info_struct *si,
784                                              unsigned long offset)
785 {
786         if (data_race(!si->swap_map[offset])) {
787                 spin_lock(&si->lock);
788                 return true;
789         }
790
791         if (vm_swap_full() && READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
792                 spin_lock(&si->lock);
793                 return true;
794         }
795
796         return false;
797 }
798
799 static int scan_swap_map_slots(struct swap_info_struct *si,
800                                unsigned char usage, int nr,
801                                swp_entry_t slots[])
802 {
803         struct swap_cluster_info *ci;
804         unsigned long offset;
805         unsigned long scan_base;
806         unsigned long last_in_cluster = 0;
807         int latency_ration = LATENCY_LIMIT;
808         int n_ret = 0;
809         bool scanned_many = false;
810
811         /*
812          * We try to cluster swap pages by allocating them sequentially
813          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
814          * way, however, we resort to first-free allocation, starting
815          * a new cluster.  This prevents us from scattering swap pages
816          * all over the entire swap partition, so that we reduce
817          * overall disk seek times between swap pages.  -- sct
818          * But we do now try to find an empty cluster.  -Andrea
819          * And we let swap pages go all over an SSD partition.  Hugh
820          */
821
822         si->flags += SWP_SCANNING;
823         /*
824          * Use percpu scan base for SSD to reduce lock contention on
825          * cluster and swap cache.  For HDD, sequential access is more
826          * important.
827          */
828         if (si->flags & SWP_SOLIDSTATE)
829                 scan_base = this_cpu_read(*si->cluster_next_cpu);
830         else
831                 scan_base = si->cluster_next;
832         offset = scan_base;
833
834         /* SSD algorithm */
835         if (si->cluster_info) {
836                 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
837                         goto scan;
838         } else if (unlikely(!si->cluster_nr--)) {
839                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
840                         si->cluster_nr = SWAPFILE_CLUSTER - 1;
841                         goto checks;
842                 }
843
844                 spin_unlock(&si->lock);
845
846                 /*
847                  * If seek is expensive, start searching for new cluster from
848                  * start of partition, to minimize the span of allocated swap.
849                  * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
850                  * case, just handled by scan_swap_map_try_ssd_cluster() above.
851                  */
852                 scan_base = offset = si->lowest_bit;
853                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
854
855                 /* Locate the first empty (unaligned) cluster */
856                 for (; last_in_cluster <= si->highest_bit; offset++) {
857                         if (si->swap_map[offset])
858                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
859                         else if (offset == last_in_cluster) {
860                                 spin_lock(&si->lock);
861                                 offset -= SWAPFILE_CLUSTER - 1;
862                                 si->cluster_next = offset;
863                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
864                                 goto checks;
865                         }
866                         if (unlikely(--latency_ration < 0)) {
867                                 cond_resched();
868                                 latency_ration = LATENCY_LIMIT;
869                         }
870                 }
871
872                 offset = scan_base;
873                 spin_lock(&si->lock);
874                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
875         }
876
877 checks:
878         if (si->cluster_info) {
879                 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
880                 /* take a break if we already got some slots */
881                         if (n_ret)
882                                 goto done;
883                         if (!scan_swap_map_try_ssd_cluster(si, &offset,
884                                                         &scan_base))
885                                 goto scan;
886                 }
887         }
888         if (!(si->flags & SWP_WRITEOK))
889                 goto no_page;
890         if (!si->highest_bit)
891                 goto no_page;
892         if (offset > si->highest_bit)
893                 scan_base = offset = si->lowest_bit;
894
895         ci = lock_cluster(si, offset);
896         /* reuse swap entry of cache-only swap if not busy. */
897         if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
898                 int swap_was_freed;
899                 unlock_cluster(ci);
900                 spin_unlock(&si->lock);
901                 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
902                 spin_lock(&si->lock);
903                 /* entry was freed successfully, try to use this again */
904                 if (swap_was_freed)
905                         goto checks;
906                 goto scan; /* check next one */
907         }
908
909         if (si->swap_map[offset]) {
910                 unlock_cluster(ci);
911                 if (!n_ret)
912                         goto scan;
913                 else
914                         goto done;
915         }
916         WRITE_ONCE(si->swap_map[offset], usage);
917         inc_cluster_info_page(si, si->cluster_info, offset);
918         unlock_cluster(ci);
919
920         swap_range_alloc(si, offset, 1);
921         slots[n_ret++] = swp_entry(si->type, offset);
922
923         /* got enough slots or reach max slots? */
924         if ((n_ret == nr) || (offset >= si->highest_bit))
925                 goto done;
926
927         /* search for next available slot */
928
929         /* time to take a break? */
930         if (unlikely(--latency_ration < 0)) {
931                 if (n_ret)
932                         goto done;
933                 spin_unlock(&si->lock);
934                 cond_resched();
935                 spin_lock(&si->lock);
936                 latency_ration = LATENCY_LIMIT;
937         }
938
939         /* try to get more slots in cluster */
940         if (si->cluster_info) {
941                 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
942                         goto checks;
943         } else if (si->cluster_nr && !si->swap_map[++offset]) {
944                 /* non-ssd case, still more slots in cluster? */
945                 --si->cluster_nr;
946                 goto checks;
947         }
948
949         /*
950          * Even if there's no free clusters available (fragmented),
951          * try to scan a little more quickly with lock held unless we
952          * have scanned too many slots already.
953          */
954         if (!scanned_many) {
955                 unsigned long scan_limit;
956
957                 if (offset < scan_base)
958                         scan_limit = scan_base;
959                 else
960                         scan_limit = si->highest_bit;
961                 for (; offset <= scan_limit && --latency_ration > 0;
962                      offset++) {
963                         if (!si->swap_map[offset])
964                                 goto checks;
965                 }
966         }
967
968 done:
969         set_cluster_next(si, offset + 1);
970         si->flags -= SWP_SCANNING;
971         return n_ret;
972
973 scan:
974         spin_unlock(&si->lock);
975         while (++offset <= READ_ONCE(si->highest_bit)) {
976                 if (swap_offset_available_and_locked(si, offset))
977                         goto checks;
978                 if (unlikely(--latency_ration < 0)) {
979                         cond_resched();
980                         latency_ration = LATENCY_LIMIT;
981                         scanned_many = true;
982                 }
983         }
984         offset = si->lowest_bit;
985         while (offset < scan_base) {
986                 if (swap_offset_available_and_locked(si, offset))
987                         goto checks;
988                 if (unlikely(--latency_ration < 0)) {
989                         cond_resched();
990                         latency_ration = LATENCY_LIMIT;
991                         scanned_many = true;
992                 }
993                 offset++;
994         }
995         spin_lock(&si->lock);
996
997 no_page:
998         si->flags -= SWP_SCANNING;
999         return n_ret;
1000 }
1001
1002 static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
1003 {
1004         unsigned long idx;
1005         struct swap_cluster_info *ci;
1006         unsigned long offset;
1007
1008         /*
1009          * Should not even be attempting cluster allocations when huge
1010          * page swap is disabled.  Warn and fail the allocation.
1011          */
1012         if (!IS_ENABLED(CONFIG_THP_SWAP)) {
1013                 VM_WARN_ON_ONCE(1);
1014                 return 0;
1015         }
1016
1017         if (cluster_list_empty(&si->free_clusters))
1018                 return 0;
1019
1020         idx = cluster_list_first(&si->free_clusters);
1021         offset = idx * SWAPFILE_CLUSTER;
1022         ci = lock_cluster(si, offset);
1023         alloc_cluster(si, idx);
1024         cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
1025
1026         memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER);
1027         unlock_cluster(ci);
1028         swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
1029         *slot = swp_entry(si->type, offset);
1030
1031         return 1;
1032 }
1033
1034 static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
1035 {
1036         unsigned long offset = idx * SWAPFILE_CLUSTER;
1037         struct swap_cluster_info *ci;
1038
1039         ci = lock_cluster(si, offset);
1040         memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
1041         cluster_set_count_flag(ci, 0, 0);
1042         free_cluster(si, idx);
1043         unlock_cluster(ci);
1044         swap_range_free(si, offset, SWAPFILE_CLUSTER);
1045 }
1046
1047 int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
1048 {
1049         unsigned long size = swap_entry_size(entry_size);
1050         struct swap_info_struct *si, *next;
1051         long avail_pgs;
1052         int n_ret = 0;
1053         int node;
1054
1055         /* Only single cluster request supported */
1056         WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1057
1058         spin_lock(&swap_avail_lock);
1059
1060         avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1061         if (avail_pgs <= 0) {
1062                 spin_unlock(&swap_avail_lock);
1063                 goto noswap;
1064         }
1065
1066         n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
1067
1068         atomic_long_sub(n_goal * size, &nr_swap_pages);
1069
1070 start_over:
1071         node = numa_node_id();
1072         plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
1073                 /* requeue si to after same-priority siblings */
1074                 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
1075                 spin_unlock(&swap_avail_lock);
1076                 spin_lock(&si->lock);
1077                 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
1078                         spin_lock(&swap_avail_lock);
1079                         if (plist_node_empty(&si->avail_lists[node])) {
1080                                 spin_unlock(&si->lock);
1081                                 goto nextsi;
1082                         }
1083                         WARN(!si->highest_bit,
1084                              "swap_info %d in list but !highest_bit\n",
1085                              si->type);
1086                         WARN(!(si->flags & SWP_WRITEOK),
1087                              "swap_info %d in list but !SWP_WRITEOK\n",
1088                              si->type);
1089                         __del_from_avail_list(si);
1090                         spin_unlock(&si->lock);
1091                         goto nextsi;
1092                 }
1093                 if (size == SWAPFILE_CLUSTER) {
1094                         if (si->flags & SWP_BLKDEV)
1095                                 n_ret = swap_alloc_cluster(si, swp_entries);
1096                 } else
1097                         n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1098                                                     n_goal, swp_entries);
1099                 spin_unlock(&si->lock);
1100                 if (n_ret || size == SWAPFILE_CLUSTER)
1101                         goto check_out;
1102                 pr_debug("scan_swap_map of si %d failed to find offset\n",
1103                         si->type);
1104
1105                 spin_lock(&swap_avail_lock);
1106 nextsi:
1107                 /*
1108                  * if we got here, it's likely that si was almost full before,
1109                  * and since scan_swap_map_slots() can drop the si->lock,
1110                  * multiple callers probably all tried to get a page from the
1111                  * same si and it filled up before we could get one; or, the si
1112                  * filled up between us dropping swap_avail_lock and taking
1113                  * si->lock. Since we dropped the swap_avail_lock, the
1114                  * swap_avail_head list may have been modified; so if next is
1115                  * still in the swap_avail_head list then try it, otherwise
1116                  * start over if we have not gotten any slots.
1117                  */
1118                 if (plist_node_empty(&next->avail_lists[node]))
1119                         goto start_over;
1120         }
1121
1122         spin_unlock(&swap_avail_lock);
1123
1124 check_out:
1125         if (n_ret < n_goal)
1126                 atomic_long_add((long)(n_goal - n_ret) * size,
1127                                 &nr_swap_pages);
1128 noswap:
1129         return n_ret;
1130 }
1131
1132 static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1133 {
1134         struct swap_info_struct *p;
1135         unsigned long offset;
1136
1137         if (!entry.val)
1138                 goto out;
1139         p = swp_swap_info(entry);
1140         if (!p)
1141                 goto bad_nofile;
1142         if (data_race(!(p->flags & SWP_USED)))
1143                 goto bad_device;
1144         offset = swp_offset(entry);
1145         if (offset >= p->max)
1146                 goto bad_offset;
1147         if (data_race(!p->swap_map[swp_offset(entry)]))
1148                 goto bad_free;
1149         return p;
1150
1151 bad_free:
1152         pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val);
1153         goto out;
1154 bad_offset:
1155         pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1156         goto out;
1157 bad_device:
1158         pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
1159         goto out;
1160 bad_nofile:
1161         pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1162 out:
1163         return NULL;
1164 }
1165
1166 static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1167                                         struct swap_info_struct *q)
1168 {
1169         struct swap_info_struct *p;
1170
1171         p = _swap_info_get(entry);
1172
1173         if (p != q) {
1174                 if (q != NULL)
1175                         spin_unlock(&q->lock);
1176                 if (p != NULL)
1177                         spin_lock(&p->lock);
1178         }
1179         return p;
1180 }
1181
1182 static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1183                                               unsigned long offset,
1184                                               unsigned char usage)
1185 {
1186         unsigned char count;
1187         unsigned char has_cache;
1188
1189         count = p->swap_map[offset];
1190
1191         has_cache = count & SWAP_HAS_CACHE;
1192         count &= ~SWAP_HAS_CACHE;
1193
1194         if (usage == SWAP_HAS_CACHE) {
1195                 VM_BUG_ON(!has_cache);
1196                 has_cache = 0;
1197         } else if (count == SWAP_MAP_SHMEM) {
1198                 /*
1199                  * Or we could insist on shmem.c using a special
1200                  * swap_shmem_free() and free_shmem_swap_and_cache()...
1201                  */
1202                 count = 0;
1203         } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1204                 if (count == COUNT_CONTINUED) {
1205                         if (swap_count_continued(p, offset, count))
1206                                 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1207                         else
1208                                 count = SWAP_MAP_MAX;
1209                 } else
1210                         count--;
1211         }
1212
1213         usage = count | has_cache;
1214         if (usage)
1215                 WRITE_ONCE(p->swap_map[offset], usage);
1216         else
1217                 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
1218
1219         return usage;
1220 }
1221
1222 /*
1223  * Check whether swap entry is valid in the swap device.  If so,
1224  * return pointer to swap_info_struct, and keep the swap entry valid
1225  * via preventing the swap device from being swapoff, until
1226  * put_swap_device() is called.  Otherwise return NULL.
1227  *
1228  * Notice that swapoff or swapoff+swapon can still happen before the
1229  * percpu_ref_tryget_live() in get_swap_device() or after the
1230  * percpu_ref_put() in put_swap_device() if there isn't any other way
1231  * to prevent swapoff, such as page lock, page table lock, etc.  The
1232  * caller must be prepared for that.  For example, the following
1233  * situation is possible.
1234  *
1235  *   CPU1                               CPU2
1236  *   do_swap_page()
1237  *     ...                              swapoff+swapon
1238  *     __read_swap_cache_async()
1239  *       swapcache_prepare()
1240  *         __swap_duplicate()
1241  *           // check swap_map
1242  *     // verify PTE not changed
1243  *
1244  * In __swap_duplicate(), the swap_map need to be checked before
1245  * changing partly because the specified swap entry may be for another
1246  * swap device which has been swapoff.  And in do_swap_page(), after
1247  * the page is read from the swap device, the PTE is verified not
1248  * changed with the page table locked to check whether the swap device
1249  * has been swapoff or swapoff+swapon.
1250  */
1251 struct swap_info_struct *get_swap_device(swp_entry_t entry)
1252 {
1253         struct swap_info_struct *si;
1254         unsigned long offset;
1255
1256         if (!entry.val)
1257                 goto out;
1258         si = swp_swap_info(entry);
1259         if (!si)
1260                 goto bad_nofile;
1261         if (!percpu_ref_tryget_live(&si->users))
1262                 goto out;
1263         /*
1264          * Guarantee the si->users are checked before accessing other
1265          * fields of swap_info_struct.
1266          *
1267          * Paired with the spin_unlock() after setup_swap_info() in
1268          * enable_swap_info().
1269          */
1270         smp_rmb();
1271         offset = swp_offset(entry);
1272         if (offset >= si->max)
1273                 goto put_out;
1274
1275         return si;
1276 bad_nofile:
1277         pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1278 out:
1279         return NULL;
1280 put_out:
1281         pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1282         percpu_ref_put(&si->users);
1283         return NULL;
1284 }
1285
1286 static unsigned char __swap_entry_free(struct swap_info_struct *p,
1287                                        swp_entry_t entry)
1288 {
1289         struct swap_cluster_info *ci;
1290         unsigned long offset = swp_offset(entry);
1291         unsigned char usage;
1292
1293         ci = lock_cluster_or_swap_info(p, offset);
1294         usage = __swap_entry_free_locked(p, offset, 1);
1295         unlock_cluster_or_swap_info(p, ci);
1296         if (!usage)
1297                 free_swap_slot(entry);
1298
1299         return usage;
1300 }
1301
1302 static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1303 {
1304         struct swap_cluster_info *ci;
1305         unsigned long offset = swp_offset(entry);
1306         unsigned char count;
1307
1308         ci = lock_cluster(p, offset);
1309         count = p->swap_map[offset];
1310         VM_BUG_ON(count != SWAP_HAS_CACHE);
1311         p->swap_map[offset] = 0;
1312         dec_cluster_info_page(p, p->cluster_info, offset);
1313         unlock_cluster(ci);
1314
1315         mem_cgroup_uncharge_swap(entry, 1);
1316         swap_range_free(p, offset, 1);
1317 }
1318
1319 /*
1320  * Caller has made sure that the swap device corresponding to entry
1321  * is still around or has not been recycled.
1322  */
1323 void swap_free(swp_entry_t entry)
1324 {
1325         struct swap_info_struct *p;
1326
1327         p = _swap_info_get(entry);
1328         if (p)
1329                 __swap_entry_free(p, entry);
1330 }
1331
1332 /*
1333  * Called after dropping swapcache to decrease refcnt to swap entries.
1334  */
1335 void put_swap_folio(struct folio *folio, swp_entry_t entry)
1336 {
1337         unsigned long offset = swp_offset(entry);
1338         unsigned long idx = offset / SWAPFILE_CLUSTER;
1339         struct swap_cluster_info *ci;
1340         struct swap_info_struct *si;
1341         unsigned char *map;
1342         unsigned int i, free_entries = 0;
1343         unsigned char val;
1344         int size = swap_entry_size(folio_nr_pages(folio));
1345
1346         si = _swap_info_get(entry);
1347         if (!si)
1348                 return;
1349
1350         ci = lock_cluster_or_swap_info(si, offset);
1351         if (size == SWAPFILE_CLUSTER) {
1352                 VM_BUG_ON(!cluster_is_huge(ci));
1353                 map = si->swap_map + offset;
1354                 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1355                         val = map[i];
1356                         VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1357                         if (val == SWAP_HAS_CACHE)
1358                                 free_entries++;
1359                 }
1360                 cluster_clear_huge(ci);
1361                 if (free_entries == SWAPFILE_CLUSTER) {
1362                         unlock_cluster_or_swap_info(si, ci);
1363                         spin_lock(&si->lock);
1364                         mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1365                         swap_free_cluster(si, idx);
1366                         spin_unlock(&si->lock);
1367                         return;
1368                 }
1369         }
1370         for (i = 0; i < size; i++, entry.val++) {
1371                 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1372                         unlock_cluster_or_swap_info(si, ci);
1373                         free_swap_slot(entry);
1374                         if (i == size - 1)
1375                                 return;
1376                         lock_cluster_or_swap_info(si, offset);
1377                 }
1378         }
1379         unlock_cluster_or_swap_info(si, ci);
1380 }
1381
1382 #ifdef CONFIG_THP_SWAP
1383 int split_swap_cluster(swp_entry_t entry)
1384 {
1385         struct swap_info_struct *si;
1386         struct swap_cluster_info *ci;
1387         unsigned long offset = swp_offset(entry);
1388
1389         si = _swap_info_get(entry);
1390         if (!si)
1391                 return -EBUSY;
1392         ci = lock_cluster(si, offset);
1393         cluster_clear_huge(ci);
1394         unlock_cluster(ci);
1395         return 0;
1396 }
1397 #endif
1398
1399 static int swp_entry_cmp(const void *ent1, const void *ent2)
1400 {
1401         const swp_entry_t *e1 = ent1, *e2 = ent2;
1402
1403         return (int)swp_type(*e1) - (int)swp_type(*e2);
1404 }
1405
1406 void swapcache_free_entries(swp_entry_t *entries, int n)
1407 {
1408         struct swap_info_struct *p, *prev;
1409         int i;
1410
1411         if (n <= 0)
1412                 return;
1413
1414         prev = NULL;
1415         p = NULL;
1416
1417         /*
1418          * Sort swap entries by swap device, so each lock is only taken once.
1419          * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1420          * so low that it isn't necessary to optimize further.
1421          */
1422         if (nr_swapfiles > 1)
1423                 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1424         for (i = 0; i < n; ++i) {
1425                 p = swap_info_get_cont(entries[i], prev);
1426                 if (p)
1427                         swap_entry_free(p, entries[i]);
1428                 prev = p;
1429         }
1430         if (p)
1431                 spin_unlock(&p->lock);
1432 }
1433
1434 int __swap_count(swp_entry_t entry)
1435 {
1436         struct swap_info_struct *si;
1437         pgoff_t offset = swp_offset(entry);
1438         int count = 0;
1439
1440         si = get_swap_device(entry);
1441         if (si) {
1442                 count = swap_count(si->swap_map[offset]);
1443                 put_swap_device(si);
1444         }
1445         return count;
1446 }
1447
1448 /*
1449  * How many references to @entry are currently swapped out?
1450  * This does not give an exact answer when swap count is continued,
1451  * but does include the high COUNT_CONTINUED flag to allow for that.
1452  */
1453 static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1454 {
1455         pgoff_t offset = swp_offset(entry);
1456         struct swap_cluster_info *ci;
1457         int count;
1458
1459         ci = lock_cluster_or_swap_info(si, offset);
1460         count = swap_count(si->swap_map[offset]);
1461         unlock_cluster_or_swap_info(si, ci);
1462         return count;
1463 }
1464
1465 /*
1466  * How many references to @entry are currently swapped out?
1467  * This does not give an exact answer when swap count is continued,
1468  * but does include the high COUNT_CONTINUED flag to allow for that.
1469  */
1470 int __swp_swapcount(swp_entry_t entry)
1471 {
1472         int count = 0;
1473         struct swap_info_struct *si;
1474
1475         si = get_swap_device(entry);
1476         if (si) {
1477                 count = swap_swapcount(si, entry);
1478                 put_swap_device(si);
1479         }
1480         return count;
1481 }
1482
1483 /*
1484  * How many references to @entry are currently swapped out?
1485  * This considers COUNT_CONTINUED so it returns exact answer.
1486  */
1487 int swp_swapcount(swp_entry_t entry)
1488 {
1489         int count, tmp_count, n;
1490         struct swap_info_struct *p;
1491         struct swap_cluster_info *ci;
1492         struct page *page;
1493         pgoff_t offset;
1494         unsigned char *map;
1495
1496         p = _swap_info_get(entry);
1497         if (!p)
1498                 return 0;
1499
1500         offset = swp_offset(entry);
1501
1502         ci = lock_cluster_or_swap_info(p, offset);
1503
1504         count = swap_count(p->swap_map[offset]);
1505         if (!(count & COUNT_CONTINUED))
1506                 goto out;
1507
1508         count &= ~COUNT_CONTINUED;
1509         n = SWAP_MAP_MAX + 1;
1510
1511         page = vmalloc_to_page(p->swap_map + offset);
1512         offset &= ~PAGE_MASK;
1513         VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1514
1515         do {
1516                 page = list_next_entry(page, lru);
1517                 map = kmap_atomic(page);
1518                 tmp_count = map[offset];
1519                 kunmap_atomic(map);
1520
1521                 count += (tmp_count & ~COUNT_CONTINUED) * n;
1522                 n *= (SWAP_CONT_MAX + 1);
1523         } while (tmp_count & COUNT_CONTINUED);
1524 out:
1525         unlock_cluster_or_swap_info(p, ci);
1526         return count;
1527 }
1528
1529 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1530                                          swp_entry_t entry)
1531 {
1532         struct swap_cluster_info *ci;
1533         unsigned char *map = si->swap_map;
1534         unsigned long roffset = swp_offset(entry);
1535         unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1536         int i;
1537         bool ret = false;
1538
1539         ci = lock_cluster_or_swap_info(si, offset);
1540         if (!ci || !cluster_is_huge(ci)) {
1541                 if (swap_count(map[roffset]))
1542                         ret = true;
1543                 goto unlock_out;
1544         }
1545         for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1546                 if (swap_count(map[offset + i])) {
1547                         ret = true;
1548                         break;
1549                 }
1550         }
1551 unlock_out:
1552         unlock_cluster_or_swap_info(si, ci);
1553         return ret;
1554 }
1555
1556 static bool folio_swapped(struct folio *folio)
1557 {
1558         swp_entry_t entry = folio_swap_entry(folio);
1559         struct swap_info_struct *si = _swap_info_get(entry);
1560
1561         if (!si)
1562                 return false;
1563
1564         if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!folio_test_large(folio)))
1565                 return swap_swapcount(si, entry) != 0;
1566
1567         return swap_page_trans_huge_swapped(si, entry);
1568 }
1569
1570 /**
1571  * folio_free_swap() - Free the swap space used for this folio.
1572  * @folio: The folio to remove.
1573  *
1574  * If swap is getting full, or if there are no more mappings of this folio,
1575  * then call folio_free_swap to free its swap space.
1576  *
1577  * Return: true if we were able to release the swap space.
1578  */
1579 bool folio_free_swap(struct folio *folio)
1580 {
1581         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1582
1583         if (!folio_test_swapcache(folio))
1584                 return false;
1585         if (folio_test_writeback(folio))
1586                 return false;
1587         if (folio_swapped(folio))
1588                 return false;
1589
1590         /*
1591          * Once hibernation has begun to create its image of memory,
1592          * there's a danger that one of the calls to folio_free_swap()
1593          * - most probably a call from __try_to_reclaim_swap() while
1594          * hibernation is allocating its own swap pages for the image,
1595          * but conceivably even a call from memory reclaim - will free
1596          * the swap from a folio which has already been recorded in the
1597          * image as a clean swapcache folio, and then reuse its swap for
1598          * another page of the image.  On waking from hibernation, the
1599          * original folio might be freed under memory pressure, then
1600          * later read back in from swap, now with the wrong data.
1601          *
1602          * Hibernation suspends storage while it is writing the image
1603          * to disk so check that here.
1604          */
1605         if (pm_suspended_storage())
1606                 return false;
1607
1608         delete_from_swap_cache(folio);
1609         folio_set_dirty(folio);
1610         return true;
1611 }
1612
1613 /*
1614  * Free the swap entry like above, but also try to
1615  * free the page cache entry if it is the last user.
1616  */
1617 int free_swap_and_cache(swp_entry_t entry)
1618 {
1619         struct swap_info_struct *p;
1620         unsigned char count;
1621
1622         if (non_swap_entry(entry))
1623                 return 1;
1624
1625         p = _swap_info_get(entry);
1626         if (p) {
1627                 count = __swap_entry_free(p, entry);
1628                 if (count == SWAP_HAS_CACHE &&
1629                     !swap_page_trans_huge_swapped(p, entry))
1630                         __try_to_reclaim_swap(p, swp_offset(entry),
1631                                               TTRS_UNMAPPED | TTRS_FULL);
1632         }
1633         return p != NULL;
1634 }
1635
1636 #ifdef CONFIG_HIBERNATION
1637
1638 swp_entry_t get_swap_page_of_type(int type)
1639 {
1640         struct swap_info_struct *si = swap_type_to_swap_info(type);
1641         swp_entry_t entry = {0};
1642
1643         if (!si)
1644                 goto fail;
1645
1646         /* This is called for allocating swap entry, not cache */
1647         spin_lock(&si->lock);
1648         if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
1649                 atomic_long_dec(&nr_swap_pages);
1650         spin_unlock(&si->lock);
1651 fail:
1652         return entry;
1653 }
1654
1655 /*
1656  * Find the swap type that corresponds to given device (if any).
1657  *
1658  * @offset - number of the PAGE_SIZE-sized block of the device, starting
1659  * from 0, in which the swap header is expected to be located.
1660  *
1661  * This is needed for the suspend to disk (aka swsusp).
1662  */
1663 int swap_type_of(dev_t device, sector_t offset)
1664 {
1665         int type;
1666
1667         if (!device)
1668                 return -1;
1669
1670         spin_lock(&swap_lock);
1671         for (type = 0; type < nr_swapfiles; type++) {
1672                 struct swap_info_struct *sis = swap_info[type];
1673
1674                 if (!(sis->flags & SWP_WRITEOK))
1675                         continue;
1676
1677                 if (device == sis->bdev->bd_dev) {
1678                         struct swap_extent *se = first_se(sis);
1679
1680                         if (se->start_block == offset) {
1681                                 spin_unlock(&swap_lock);
1682                                 return type;
1683                         }
1684                 }
1685         }
1686         spin_unlock(&swap_lock);
1687         return -ENODEV;
1688 }
1689
1690 int find_first_swap(dev_t *device)
1691 {
1692         int type;
1693
1694         spin_lock(&swap_lock);
1695         for (type = 0; type < nr_swapfiles; type++) {
1696                 struct swap_info_struct *sis = swap_info[type];
1697
1698                 if (!(sis->flags & SWP_WRITEOK))
1699                         continue;
1700                 *device = sis->bdev->bd_dev;
1701                 spin_unlock(&swap_lock);
1702                 return type;
1703         }
1704         spin_unlock(&swap_lock);
1705         return -ENODEV;
1706 }
1707
1708 /*
1709  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1710  * corresponding to given index in swap_info (swap type).
1711  */
1712 sector_t swapdev_block(int type, pgoff_t offset)
1713 {
1714         struct swap_info_struct *si = swap_type_to_swap_info(type);
1715         struct swap_extent *se;
1716
1717         if (!si || !(si->flags & SWP_WRITEOK))
1718                 return 0;
1719         se = offset_to_swap_extent(si, offset);
1720         return se->start_block + (offset - se->start_page);
1721 }
1722
1723 /*
1724  * Return either the total number of swap pages of given type, or the number
1725  * of free pages of that type (depending on @free)
1726  *
1727  * This is needed for software suspend
1728  */
1729 unsigned int count_swap_pages(int type, int free)
1730 {
1731         unsigned int n = 0;
1732
1733         spin_lock(&swap_lock);
1734         if ((unsigned int)type < nr_swapfiles) {
1735                 struct swap_info_struct *sis = swap_info[type];
1736
1737                 spin_lock(&sis->lock);
1738                 if (sis->flags & SWP_WRITEOK) {
1739                         n = sis->pages;
1740                         if (free)
1741                                 n -= sis->inuse_pages;
1742                 }
1743                 spin_unlock(&sis->lock);
1744         }
1745         spin_unlock(&swap_lock);
1746         return n;
1747 }
1748 #endif /* CONFIG_HIBERNATION */
1749
1750 static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1751 {
1752         return pte_same(pte_swp_clear_flags(pte), swp_pte);
1753 }
1754
1755 /*
1756  * No need to decide whether this PTE shares the swap entry with others,
1757  * just let do_wp_page work it out if a write is requested later - to
1758  * force COW, vm_page_prot omits write permission from any private vma.
1759  */
1760 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1761                 unsigned long addr, swp_entry_t entry, struct folio *folio)
1762 {
1763         struct page *page = folio_file_page(folio, swp_offset(entry));
1764         struct page *swapcache;
1765         spinlock_t *ptl;
1766         pte_t *pte, new_pte;
1767         int ret = 1;
1768
1769         swapcache = page;
1770         page = ksm_might_need_to_copy(page, vma, addr);
1771         if (unlikely(!page))
1772                 return -ENOMEM;
1773
1774         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1775         if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1776                 ret = 0;
1777                 goto out;
1778         }
1779
1780         if (unlikely(!PageUptodate(page))) {
1781                 pte_t pteval;
1782
1783                 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1784                 pteval = swp_entry_to_pte(make_swapin_error_entry(page));
1785                 set_pte_at(vma->vm_mm, addr, pte, pteval);
1786                 swap_free(entry);
1787                 ret = 0;
1788                 goto out;
1789         }
1790
1791         /* See do_swap_page() */
1792         BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
1793         BUG_ON(PageAnon(page) && PageAnonExclusive(page));
1794
1795         dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1796         inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1797         get_page(page);
1798         if (page == swapcache) {
1799                 rmap_t rmap_flags = RMAP_NONE;
1800
1801                 /*
1802                  * See do_swap_page(): PageWriteback() would be problematic.
1803                  * However, we do a wait_on_page_writeback() just before this
1804                  * call and have the page locked.
1805                  */
1806                 VM_BUG_ON_PAGE(PageWriteback(page), page);
1807                 if (pte_swp_exclusive(*pte))
1808                         rmap_flags |= RMAP_EXCLUSIVE;
1809
1810                 page_add_anon_rmap(page, vma, addr, rmap_flags);
1811         } else { /* ksm created a completely new copy */
1812                 page_add_new_anon_rmap(page, vma, addr);
1813                 lru_cache_add_inactive_or_unevictable(page, vma);
1814         }
1815         new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot));
1816         if (pte_swp_soft_dirty(*pte))
1817                 new_pte = pte_mksoft_dirty(new_pte);
1818         if (pte_swp_uffd_wp(*pte))
1819                 new_pte = pte_mkuffd_wp(new_pte);
1820         set_pte_at(vma->vm_mm, addr, pte, new_pte);
1821         swap_free(entry);
1822 out:
1823         pte_unmap_unlock(pte, ptl);
1824         if (page != swapcache) {
1825                 unlock_page(page);
1826                 put_page(page);
1827         }
1828         return ret;
1829 }
1830
1831 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1832                         unsigned long addr, unsigned long end,
1833                         unsigned int type)
1834 {
1835         swp_entry_t entry;
1836         pte_t *pte;
1837         struct swap_info_struct *si;
1838         int ret = 0;
1839         volatile unsigned char *swap_map;
1840
1841         si = swap_info[type];
1842         pte = pte_offset_map(pmd, addr);
1843         do {
1844                 struct folio *folio;
1845                 unsigned long offset;
1846
1847                 if (!is_swap_pte(*pte))
1848                         continue;
1849
1850                 entry = pte_to_swp_entry(*pte);
1851                 if (swp_type(entry) != type)
1852                         continue;
1853
1854                 offset = swp_offset(entry);
1855                 pte_unmap(pte);
1856                 swap_map = &si->swap_map[offset];
1857                 folio = swap_cache_get_folio(entry, vma, addr);
1858                 if (!folio) {
1859                         struct page *page;
1860                         struct vm_fault vmf = {
1861                                 .vma = vma,
1862                                 .address = addr,
1863                                 .real_address = addr,
1864                                 .pmd = pmd,
1865                         };
1866
1867                         page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
1868                                                 &vmf);
1869                         if (page)
1870                                 folio = page_folio(page);
1871                 }
1872                 if (!folio) {
1873                         if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1874                                 goto try_next;
1875                         return -ENOMEM;
1876                 }
1877
1878                 folio_lock(folio);
1879                 folio_wait_writeback(folio);
1880                 ret = unuse_pte(vma, pmd, addr, entry, folio);
1881                 if (ret < 0) {
1882                         folio_unlock(folio);
1883                         folio_put(folio);
1884                         goto out;
1885                 }
1886
1887                 folio_free_swap(folio);
1888                 folio_unlock(folio);
1889                 folio_put(folio);
1890 try_next:
1891                 pte = pte_offset_map(pmd, addr);
1892         } while (pte++, addr += PAGE_SIZE, addr != end);
1893         pte_unmap(pte - 1);
1894
1895         ret = 0;
1896 out:
1897         return ret;
1898 }
1899
1900 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1901                                 unsigned long addr, unsigned long end,
1902                                 unsigned int type)
1903 {
1904         pmd_t *pmd;
1905         unsigned long next;
1906         int ret;
1907
1908         pmd = pmd_offset(pud, addr);
1909         do {
1910                 cond_resched();
1911                 next = pmd_addr_end(addr, end);
1912                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1913                         continue;
1914                 ret = unuse_pte_range(vma, pmd, addr, next, type);
1915                 if (ret)
1916                         return ret;
1917         } while (pmd++, addr = next, addr != end);
1918         return 0;
1919 }
1920
1921 static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
1922                                 unsigned long addr, unsigned long end,
1923                                 unsigned int type)
1924 {
1925         pud_t *pud;
1926         unsigned long next;
1927         int ret;
1928
1929         pud = pud_offset(p4d, addr);
1930         do {
1931                 next = pud_addr_end(addr, end);
1932                 if (pud_none_or_clear_bad(pud))
1933                         continue;
1934                 ret = unuse_pmd_range(vma, pud, addr, next, type);
1935                 if (ret)
1936                         return ret;
1937         } while (pud++, addr = next, addr != end);
1938         return 0;
1939 }
1940
1941 static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
1942                                 unsigned long addr, unsigned long end,
1943                                 unsigned int type)
1944 {
1945         p4d_t *p4d;
1946         unsigned long next;
1947         int ret;
1948
1949         p4d = p4d_offset(pgd, addr);
1950         do {
1951                 next = p4d_addr_end(addr, end);
1952                 if (p4d_none_or_clear_bad(p4d))
1953                         continue;
1954                 ret = unuse_pud_range(vma, p4d, addr, next, type);
1955                 if (ret)
1956                         return ret;
1957         } while (p4d++, addr = next, addr != end);
1958         return 0;
1959 }
1960
1961 static int unuse_vma(struct vm_area_struct *vma, unsigned int type)
1962 {
1963         pgd_t *pgd;
1964         unsigned long addr, end, next;
1965         int ret;
1966
1967         addr = vma->vm_start;
1968         end = vma->vm_end;
1969
1970         pgd = pgd_offset(vma->vm_mm, addr);
1971         do {
1972                 next = pgd_addr_end(addr, end);
1973                 if (pgd_none_or_clear_bad(pgd))
1974                         continue;
1975                 ret = unuse_p4d_range(vma, pgd, addr, next, type);
1976                 if (ret)
1977                         return ret;
1978         } while (pgd++, addr = next, addr != end);
1979         return 0;
1980 }
1981
1982 static int unuse_mm(struct mm_struct *mm, unsigned int type)
1983 {
1984         struct vm_area_struct *vma;
1985         int ret = 0;
1986         VMA_ITERATOR(vmi, mm, 0);
1987
1988         mmap_read_lock(mm);
1989         for_each_vma(vmi, vma) {
1990                 if (vma->anon_vma) {
1991                         ret = unuse_vma(vma, type);
1992                         if (ret)
1993                                 break;
1994                 }
1995
1996                 cond_resched();
1997         }
1998         mmap_read_unlock(mm);
1999         return ret;
2000 }
2001
2002 /*
2003  * Scan swap_map from current position to next entry still in use.
2004  * Return 0 if there are no inuse entries after prev till end of
2005  * the map.
2006  */
2007 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
2008                                         unsigned int prev)
2009 {
2010         unsigned int i;
2011         unsigned char count;
2012
2013         /*
2014          * No need for swap_lock here: we're just looking
2015          * for whether an entry is in use, not modifying it; false
2016          * hits are okay, and sys_swapoff() has already prevented new
2017          * allocations from this area (while holding swap_lock).
2018          */
2019         for (i = prev + 1; i < si->max; i++) {
2020                 count = READ_ONCE(si->swap_map[i]);
2021                 if (count && swap_count(count) != SWAP_MAP_BAD)
2022                         break;
2023                 if ((i % LATENCY_LIMIT) == 0)
2024                         cond_resched();
2025         }
2026
2027         if (i == si->max)
2028                 i = 0;
2029
2030         return i;
2031 }
2032
2033 static int try_to_unuse(unsigned int type)
2034 {
2035         struct mm_struct *prev_mm;
2036         struct mm_struct *mm;
2037         struct list_head *p;
2038         int retval = 0;
2039         struct swap_info_struct *si = swap_info[type];
2040         struct folio *folio;
2041         swp_entry_t entry;
2042         unsigned int i;
2043
2044         if (!READ_ONCE(si->inuse_pages))
2045                 return 0;
2046
2047 retry:
2048         retval = shmem_unuse(type);
2049         if (retval)
2050                 return retval;
2051
2052         prev_mm = &init_mm;
2053         mmget(prev_mm);
2054
2055         spin_lock(&mmlist_lock);
2056         p = &init_mm.mmlist;
2057         while (READ_ONCE(si->inuse_pages) &&
2058                !signal_pending(current) &&
2059                (p = p->next) != &init_mm.mmlist) {
2060
2061                 mm = list_entry(p, struct mm_struct, mmlist);
2062                 if (!mmget_not_zero(mm))
2063                         continue;
2064                 spin_unlock(&mmlist_lock);
2065                 mmput(prev_mm);
2066                 prev_mm = mm;
2067                 retval = unuse_mm(mm, type);
2068                 if (retval) {
2069                         mmput(prev_mm);
2070                         return retval;
2071                 }
2072
2073                 /*
2074                  * Make sure that we aren't completely killing
2075                  * interactive performance.
2076                  */
2077                 cond_resched();
2078                 spin_lock(&mmlist_lock);
2079         }
2080         spin_unlock(&mmlist_lock);
2081
2082         mmput(prev_mm);
2083
2084         i = 0;
2085         while (READ_ONCE(si->inuse_pages) &&
2086                !signal_pending(current) &&
2087                (i = find_next_to_unuse(si, i)) != 0) {
2088
2089                 entry = swp_entry(type, i);
2090                 folio = filemap_get_folio(swap_address_space(entry), i);
2091                 if (!folio)
2092                         continue;
2093
2094                 /*
2095                  * It is conceivable that a racing task removed this folio from
2096                  * swap cache just before we acquired the page lock. The folio
2097                  * might even be back in swap cache on another swap area. But
2098                  * that is okay, folio_free_swap() only removes stale folios.
2099                  */
2100                 folio_lock(folio);
2101                 folio_wait_writeback(folio);
2102                 folio_free_swap(folio);
2103                 folio_unlock(folio);
2104                 folio_put(folio);
2105         }
2106
2107         /*
2108          * Lets check again to see if there are still swap entries in the map.
2109          * If yes, we would need to do retry the unuse logic again.
2110          * Under global memory pressure, swap entries can be reinserted back
2111          * into process space after the mmlist loop above passes over them.
2112          *
2113          * Limit the number of retries? No: when mmget_not_zero()
2114          * above fails, that mm is likely to be freeing swap from
2115          * exit_mmap(), which proceeds at its own independent pace;
2116          * and even shmem_writepage() could have been preempted after
2117          * folio_alloc_swap(), temporarily hiding that swap.  It's easy
2118          * and robust (though cpu-intensive) just to keep retrying.
2119          */
2120         if (READ_ONCE(si->inuse_pages)) {
2121                 if (!signal_pending(current))
2122                         goto retry;
2123                 return -EINTR;
2124         }
2125
2126         return 0;
2127 }
2128
2129 /*
2130  * After a successful try_to_unuse, if no swap is now in use, we know
2131  * we can empty the mmlist.  swap_lock must be held on entry and exit.
2132  * Note that mmlist_lock nests inside swap_lock, and an mm must be
2133  * added to the mmlist just after page_duplicate - before would be racy.
2134  */
2135 static void drain_mmlist(void)
2136 {
2137         struct list_head *p, *next;
2138         unsigned int type;
2139
2140         for (type = 0; type < nr_swapfiles; type++)
2141                 if (swap_info[type]->inuse_pages)
2142                         return;
2143         spin_lock(&mmlist_lock);
2144         list_for_each_safe(p, next, &init_mm.mmlist)
2145                 list_del_init(p);
2146         spin_unlock(&mmlist_lock);
2147 }
2148
2149 /*
2150  * Free all of a swapdev's extent information
2151  */
2152 static void destroy_swap_extents(struct swap_info_struct *sis)
2153 {
2154         while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2155                 struct rb_node *rb = sis->swap_extent_root.rb_node;
2156                 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2157
2158                 rb_erase(rb, &sis->swap_extent_root);
2159                 kfree(se);
2160         }
2161
2162         if (sis->flags & SWP_ACTIVATED) {
2163                 struct file *swap_file = sis->swap_file;
2164                 struct address_space *mapping = swap_file->f_mapping;
2165
2166                 sis->flags &= ~SWP_ACTIVATED;
2167                 if (mapping->a_ops->swap_deactivate)
2168                         mapping->a_ops->swap_deactivate(swap_file);
2169         }
2170 }
2171
2172 /*
2173  * Add a block range (and the corresponding page range) into this swapdev's
2174  * extent tree.
2175  *
2176  * This function rather assumes that it is called in ascending page order.
2177  */
2178 int
2179 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2180                 unsigned long nr_pages, sector_t start_block)
2181 {
2182         struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2183         struct swap_extent *se;
2184         struct swap_extent *new_se;
2185
2186         /*
2187          * place the new node at the right most since the
2188          * function is called in ascending page order.
2189          */
2190         while (*link) {
2191                 parent = *link;
2192                 link = &parent->rb_right;
2193         }
2194
2195         if (parent) {
2196                 se = rb_entry(parent, struct swap_extent, rb_node);
2197                 BUG_ON(se->start_page + se->nr_pages != start_page);
2198                 if (se->start_block + se->nr_pages == start_block) {
2199                         /* Merge it */
2200                         se->nr_pages += nr_pages;
2201                         return 0;
2202                 }
2203         }
2204
2205         /* No merge, insert a new extent. */
2206         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2207         if (new_se == NULL)
2208                 return -ENOMEM;
2209         new_se->start_page = start_page;
2210         new_se->nr_pages = nr_pages;
2211         new_se->start_block = start_block;
2212
2213         rb_link_node(&new_se->rb_node, parent, link);
2214         rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2215         return 1;
2216 }
2217 EXPORT_SYMBOL_GPL(add_swap_extent);
2218
2219 /*
2220  * A `swap extent' is a simple thing which maps a contiguous range of pages
2221  * onto a contiguous range of disk blocks.  A rbtree of swap extents is
2222  * built at swapon time and is then used at swap_writepage/swap_readpage
2223  * time for locating where on disk a page belongs.
2224  *
2225  * If the swapfile is an S_ISBLK block device, a single extent is installed.
2226  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2227  * swap files identically.
2228  *
2229  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2230  * extent rbtree operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
2231  * swapfiles are handled *identically* after swapon time.
2232  *
2233  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2234  * and will parse them into a rbtree, in PAGE_SIZE chunks.  If some stray
2235  * blocks are found which do not fall within the PAGE_SIZE alignment
2236  * requirements, they are simply tossed out - we will never use those blocks
2237  * for swapping.
2238  *
2239  * For all swap devices we set S_SWAPFILE across the life of the swapon.  This
2240  * prevents users from writing to the swap device, which will corrupt memory.
2241  *
2242  * The amount of disk space which a single swap extent represents varies.
2243  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
2244  * extents in the rbtree. - akpm.
2245  */
2246 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2247 {
2248         struct file *swap_file = sis->swap_file;
2249         struct address_space *mapping = swap_file->f_mapping;
2250         struct inode *inode = mapping->host;
2251         int ret;
2252
2253         if (S_ISBLK(inode->i_mode)) {
2254                 ret = add_swap_extent(sis, 0, sis->max, 0);
2255                 *span = sis->pages;
2256                 return ret;
2257         }
2258
2259         if (mapping->a_ops->swap_activate) {
2260                 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2261                 if (ret < 0)
2262                         return ret;
2263                 sis->flags |= SWP_ACTIVATED;
2264                 if ((sis->flags & SWP_FS_OPS) &&
2265                     sio_pool_init() != 0) {
2266                         destroy_swap_extents(sis);
2267                         return -ENOMEM;
2268                 }
2269                 return ret;
2270         }
2271
2272         return generic_swapfile_activate(sis, swap_file, span);
2273 }
2274
2275 static int swap_node(struct swap_info_struct *p)
2276 {
2277         struct block_device *bdev;
2278
2279         if (p->bdev)
2280                 bdev = p->bdev;
2281         else
2282                 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2283
2284         return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2285 }
2286
2287 static void setup_swap_info(struct swap_info_struct *p, int prio,
2288                             unsigned char *swap_map,
2289                             struct swap_cluster_info *cluster_info)
2290 {
2291         int i;
2292
2293         if (prio >= 0)
2294                 p->prio = prio;
2295         else
2296                 p->prio = --least_priority;
2297         /*
2298          * the plist prio is negated because plist ordering is
2299          * low-to-high, while swap ordering is high-to-low
2300          */
2301         p->list.prio = -p->prio;
2302         for_each_node(i) {
2303                 if (p->prio >= 0)
2304                         p->avail_lists[i].prio = -p->prio;
2305                 else {
2306                         if (swap_node(p) == i)
2307                                 p->avail_lists[i].prio = 1;
2308                         else
2309                                 p->avail_lists[i].prio = -p->prio;
2310                 }
2311         }
2312         p->swap_map = swap_map;
2313         p->cluster_info = cluster_info;
2314 }
2315
2316 static void _enable_swap_info(struct swap_info_struct *p)
2317 {
2318         p->flags |= SWP_WRITEOK;
2319         atomic_long_add(p->pages, &nr_swap_pages);
2320         total_swap_pages += p->pages;
2321
2322         assert_spin_locked(&swap_lock);
2323         /*
2324          * both lists are plists, and thus priority ordered.
2325          * swap_active_head needs to be priority ordered for swapoff(),
2326          * which on removal of any swap_info_struct with an auto-assigned
2327          * (i.e. negative) priority increments the auto-assigned priority
2328          * of any lower-priority swap_info_structs.
2329          * swap_avail_head needs to be priority ordered for folio_alloc_swap(),
2330          * which allocates swap pages from the highest available priority
2331          * swap_info_struct.
2332          */
2333         plist_add(&p->list, &swap_active_head);
2334         add_to_avail_list(p);
2335 }
2336
2337 static void enable_swap_info(struct swap_info_struct *p, int prio,
2338                                 unsigned char *swap_map,
2339                                 struct swap_cluster_info *cluster_info,
2340                                 unsigned long *frontswap_map)
2341 {
2342         if (IS_ENABLED(CONFIG_FRONTSWAP))
2343                 frontswap_init(p->type, frontswap_map);
2344         spin_lock(&swap_lock);
2345         spin_lock(&p->lock);
2346         setup_swap_info(p, prio, swap_map, cluster_info);
2347         spin_unlock(&p->lock);
2348         spin_unlock(&swap_lock);
2349         /*
2350          * Finished initializing swap device, now it's safe to reference it.
2351          */
2352         percpu_ref_resurrect(&p->users);
2353         spin_lock(&swap_lock);
2354         spin_lock(&p->lock);
2355         _enable_swap_info(p);
2356         spin_unlock(&p->lock);
2357         spin_unlock(&swap_lock);
2358 }
2359
2360 static void reinsert_swap_info(struct swap_info_struct *p)
2361 {
2362         spin_lock(&swap_lock);
2363         spin_lock(&p->lock);
2364         setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2365         _enable_swap_info(p);
2366         spin_unlock(&p->lock);
2367         spin_unlock(&swap_lock);
2368 }
2369
2370 bool has_usable_swap(void)
2371 {
2372         bool ret = true;
2373
2374         spin_lock(&swap_lock);
2375         if (plist_head_empty(&swap_active_head))
2376                 ret = false;
2377         spin_unlock(&swap_lock);
2378         return ret;
2379 }
2380
2381 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2382 {
2383         struct swap_info_struct *p = NULL;
2384         unsigned char *swap_map;
2385         struct swap_cluster_info *cluster_info;
2386         unsigned long *frontswap_map;
2387         struct file *swap_file, *victim;
2388         struct address_space *mapping;
2389         struct inode *inode;
2390         struct filename *pathname;
2391         int err, found = 0;
2392         unsigned int old_block_size;
2393
2394         if (!capable(CAP_SYS_ADMIN))
2395                 return -EPERM;
2396
2397         BUG_ON(!current->mm);
2398
2399         pathname = getname(specialfile);
2400         if (IS_ERR(pathname))
2401                 return PTR_ERR(pathname);
2402
2403         victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2404         err = PTR_ERR(victim);
2405         if (IS_ERR(victim))
2406                 goto out;
2407
2408         mapping = victim->f_mapping;
2409         spin_lock(&swap_lock);
2410         plist_for_each_entry(p, &swap_active_head, list) {
2411                 if (p->flags & SWP_WRITEOK) {
2412                         if (p->swap_file->f_mapping == mapping) {
2413                                 found = 1;
2414                                 break;
2415                         }
2416                 }
2417         }
2418         if (!found) {
2419                 err = -EINVAL;
2420                 spin_unlock(&swap_lock);
2421                 goto out_dput;
2422         }
2423         if (!security_vm_enough_memory_mm(current->mm, p->pages))
2424                 vm_unacct_memory(p->pages);
2425         else {
2426                 err = -ENOMEM;
2427                 spin_unlock(&swap_lock);
2428                 goto out_dput;
2429         }
2430         del_from_avail_list(p);
2431         spin_lock(&p->lock);
2432         if (p->prio < 0) {
2433                 struct swap_info_struct *si = p;
2434                 int nid;
2435
2436                 plist_for_each_entry_continue(si, &swap_active_head, list) {
2437                         si->prio++;
2438                         si->list.prio--;
2439                         for_each_node(nid) {
2440                                 if (si->avail_lists[nid].prio != 1)
2441                                         si->avail_lists[nid].prio--;
2442                         }
2443                 }
2444                 least_priority++;
2445         }
2446         plist_del(&p->list, &swap_active_head);
2447         atomic_long_sub(p->pages, &nr_swap_pages);
2448         total_swap_pages -= p->pages;
2449         p->flags &= ~SWP_WRITEOK;
2450         spin_unlock(&p->lock);
2451         spin_unlock(&swap_lock);
2452
2453         disable_swap_slots_cache_lock();
2454
2455         set_current_oom_origin();
2456         err = try_to_unuse(p->type);
2457         clear_current_oom_origin();
2458
2459         if (err) {
2460                 /* re-insert swap space back into swap_list */
2461                 reinsert_swap_info(p);
2462                 reenable_swap_slots_cache_unlock();
2463                 goto out_dput;
2464         }
2465
2466         reenable_swap_slots_cache_unlock();
2467
2468         /*
2469          * Wait for swap operations protected by get/put_swap_device()
2470          * to complete.
2471          *
2472          * We need synchronize_rcu() here to protect the accessing to
2473          * the swap cache data structure.
2474          */
2475         percpu_ref_kill(&p->users);
2476         synchronize_rcu();
2477         wait_for_completion(&p->comp);
2478
2479         flush_work(&p->discard_work);
2480
2481         destroy_swap_extents(p);
2482         if (p->flags & SWP_CONTINUED)
2483                 free_swap_count_continuations(p);
2484
2485         if (!p->bdev || !bdev_nonrot(p->bdev))
2486                 atomic_dec(&nr_rotate_swap);
2487
2488         mutex_lock(&swapon_mutex);
2489         spin_lock(&swap_lock);
2490         spin_lock(&p->lock);
2491         drain_mmlist();
2492
2493         /* wait for anyone still in scan_swap_map_slots */
2494         p->highest_bit = 0;             /* cuts scans short */
2495         while (p->flags >= SWP_SCANNING) {
2496                 spin_unlock(&p->lock);
2497                 spin_unlock(&swap_lock);
2498                 schedule_timeout_uninterruptible(1);
2499                 spin_lock(&swap_lock);
2500                 spin_lock(&p->lock);
2501         }
2502
2503         swap_file = p->swap_file;
2504         old_block_size = p->old_block_size;
2505         p->swap_file = NULL;
2506         p->max = 0;
2507         swap_map = p->swap_map;
2508         p->swap_map = NULL;
2509         cluster_info = p->cluster_info;
2510         p->cluster_info = NULL;
2511         frontswap_map = frontswap_map_get(p);
2512         spin_unlock(&p->lock);
2513         spin_unlock(&swap_lock);
2514         arch_swap_invalidate_area(p->type);
2515         frontswap_invalidate_area(p->type);
2516         frontswap_map_set(p, NULL);
2517         mutex_unlock(&swapon_mutex);
2518         free_percpu(p->percpu_cluster);
2519         p->percpu_cluster = NULL;
2520         free_percpu(p->cluster_next_cpu);
2521         p->cluster_next_cpu = NULL;
2522         vfree(swap_map);
2523         kvfree(cluster_info);
2524         kvfree(frontswap_map);
2525         /* Destroy swap account information */
2526         swap_cgroup_swapoff(p->type);
2527         exit_swap_address_space(p->type);
2528
2529         inode = mapping->host;
2530         if (S_ISBLK(inode->i_mode)) {
2531                 struct block_device *bdev = I_BDEV(inode);
2532
2533                 set_blocksize(bdev, old_block_size);
2534                 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2535         }
2536
2537         inode_lock(inode);
2538         inode->i_flags &= ~S_SWAPFILE;
2539         inode_unlock(inode);
2540         filp_close(swap_file, NULL);
2541
2542         /*
2543          * Clear the SWP_USED flag after all resources are freed so that swapon
2544          * can reuse this swap_info in alloc_swap_info() safely.  It is ok to
2545          * not hold p->lock after we cleared its SWP_WRITEOK.
2546          */
2547         spin_lock(&swap_lock);
2548         p->flags = 0;
2549         spin_unlock(&swap_lock);
2550
2551         err = 0;
2552         atomic_inc(&proc_poll_event);
2553         wake_up_interruptible(&proc_poll_wait);
2554
2555 out_dput:
2556         filp_close(victim, NULL);
2557 out:
2558         putname(pathname);
2559         return err;
2560 }
2561
2562 #ifdef CONFIG_PROC_FS
2563 static __poll_t swaps_poll(struct file *file, poll_table *wait)
2564 {
2565         struct seq_file *seq = file->private_data;
2566
2567         poll_wait(file, &proc_poll_wait, wait);
2568
2569         if (seq->poll_event != atomic_read(&proc_poll_event)) {
2570                 seq->poll_event = atomic_read(&proc_poll_event);
2571                 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2572         }
2573
2574         return EPOLLIN | EPOLLRDNORM;
2575 }
2576
2577 /* iterator */
2578 static void *swap_start(struct seq_file *swap, loff_t *pos)
2579 {
2580         struct swap_info_struct *si;
2581         int type;
2582         loff_t l = *pos;
2583
2584         mutex_lock(&swapon_mutex);
2585
2586         if (!l)
2587                 return SEQ_START_TOKEN;
2588
2589         for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2590                 if (!(si->flags & SWP_USED) || !si->swap_map)
2591                         continue;
2592                 if (!--l)
2593                         return si;
2594         }
2595
2596         return NULL;
2597 }
2598
2599 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2600 {
2601         struct swap_info_struct *si = v;
2602         int type;
2603
2604         if (v == SEQ_START_TOKEN)
2605                 type = 0;
2606         else
2607                 type = si->type + 1;
2608
2609         ++(*pos);
2610         for (; (si = swap_type_to_swap_info(type)); type++) {
2611                 if (!(si->flags & SWP_USED) || !si->swap_map)
2612                         continue;
2613                 return si;
2614         }
2615
2616         return NULL;
2617 }
2618
2619 static void swap_stop(struct seq_file *swap, void *v)
2620 {
2621         mutex_unlock(&swapon_mutex);
2622 }
2623
2624 static int swap_show(struct seq_file *swap, void *v)
2625 {
2626         struct swap_info_struct *si = v;
2627         struct file *file;
2628         int len;
2629         unsigned long bytes, inuse;
2630
2631         if (si == SEQ_START_TOKEN) {
2632                 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2633                 return 0;
2634         }
2635
2636         bytes = si->pages << (PAGE_SHIFT - 10);
2637         inuse = READ_ONCE(si->inuse_pages) << (PAGE_SHIFT - 10);
2638
2639         file = si->swap_file;
2640         len = seq_file_path(swap, file, " \t\n\\");
2641         seq_printf(swap, "%*s%s\t%lu\t%s%lu\t%s%d\n",
2642                         len < 40 ? 40 - len : 1, " ",
2643                         S_ISBLK(file_inode(file)->i_mode) ?
2644                                 "partition" : "file\t",
2645                         bytes, bytes < 10000000 ? "\t" : "",
2646                         inuse, inuse < 10000000 ? "\t" : "",
2647                         si->prio);
2648         return 0;
2649 }
2650
2651 static const struct seq_operations swaps_op = {
2652         .start =        swap_start,
2653         .next =         swap_next,
2654         .stop =         swap_stop,
2655         .show =         swap_show
2656 };
2657
2658 static int swaps_open(struct inode *inode, struct file *file)
2659 {
2660         struct seq_file *seq;
2661         int ret;
2662
2663         ret = seq_open(file, &swaps_op);
2664         if (ret)
2665                 return ret;
2666
2667         seq = file->private_data;
2668         seq->poll_event = atomic_read(&proc_poll_event);
2669         return 0;
2670 }
2671
2672 static const struct proc_ops swaps_proc_ops = {
2673         .proc_flags     = PROC_ENTRY_PERMANENT,
2674         .proc_open      = swaps_open,
2675         .proc_read      = seq_read,
2676         .proc_lseek     = seq_lseek,
2677         .proc_release   = seq_release,
2678         .proc_poll      = swaps_poll,
2679 };
2680
2681 static int __init procswaps_init(void)
2682 {
2683         proc_create("swaps", 0, NULL, &swaps_proc_ops);
2684         return 0;
2685 }
2686 __initcall(procswaps_init);
2687 #endif /* CONFIG_PROC_FS */
2688
2689 #ifdef MAX_SWAPFILES_CHECK
2690 static int __init max_swapfiles_check(void)
2691 {
2692         MAX_SWAPFILES_CHECK();
2693         return 0;
2694 }
2695 late_initcall(max_swapfiles_check);
2696 #endif
2697
2698 static struct swap_info_struct *alloc_swap_info(void)
2699 {
2700         struct swap_info_struct *p;
2701         struct swap_info_struct *defer = NULL;
2702         unsigned int type;
2703         int i;
2704
2705         p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2706         if (!p)
2707                 return ERR_PTR(-ENOMEM);
2708
2709         if (percpu_ref_init(&p->users, swap_users_ref_free,
2710                             PERCPU_REF_INIT_DEAD, GFP_KERNEL)) {
2711                 kvfree(p);
2712                 return ERR_PTR(-ENOMEM);
2713         }
2714
2715         spin_lock(&swap_lock);
2716         for (type = 0; type < nr_swapfiles; type++) {
2717                 if (!(swap_info[type]->flags & SWP_USED))
2718                         break;
2719         }
2720         if (type >= MAX_SWAPFILES) {
2721                 spin_unlock(&swap_lock);
2722                 percpu_ref_exit(&p->users);
2723                 kvfree(p);
2724                 return ERR_PTR(-EPERM);
2725         }
2726         if (type >= nr_swapfiles) {
2727                 p->type = type;
2728                 /*
2729                  * Publish the swap_info_struct after initializing it.
2730                  * Note that kvzalloc() above zeroes all its fields.
2731                  */
2732                 smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */
2733                 nr_swapfiles++;
2734         } else {
2735                 defer = p;
2736                 p = swap_info[type];
2737                 /*
2738                  * Do not memset this entry: a racing procfs swap_next()
2739                  * would be relying on p->type to remain valid.
2740                  */
2741         }
2742         p->swap_extent_root = RB_ROOT;
2743         plist_node_init(&p->list, 0);
2744         for_each_node(i)
2745                 plist_node_init(&p->avail_lists[i], 0);
2746         p->flags = SWP_USED;
2747         spin_unlock(&swap_lock);
2748         if (defer) {
2749                 percpu_ref_exit(&defer->users);
2750                 kvfree(defer);
2751         }
2752         spin_lock_init(&p->lock);
2753         spin_lock_init(&p->cont_lock);
2754         init_completion(&p->comp);
2755
2756         return p;
2757 }
2758
2759 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2760 {
2761         int error;
2762
2763         if (S_ISBLK(inode->i_mode)) {
2764                 p->bdev = blkdev_get_by_dev(inode->i_rdev,
2765                                    FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2766                 if (IS_ERR(p->bdev)) {
2767                         error = PTR_ERR(p->bdev);
2768                         p->bdev = NULL;
2769                         return error;
2770                 }
2771                 p->old_block_size = block_size(p->bdev);
2772                 error = set_blocksize(p->bdev, PAGE_SIZE);
2773                 if (error < 0)
2774                         return error;
2775                 /*
2776                  * Zoned block devices contain zones that have a sequential
2777                  * write only restriction.  Hence zoned block devices are not
2778                  * suitable for swapping.  Disallow them here.
2779                  */
2780                 if (bdev_is_zoned(p->bdev))
2781                         return -EINVAL;
2782                 p->flags |= SWP_BLKDEV;
2783         } else if (S_ISREG(inode->i_mode)) {
2784                 p->bdev = inode->i_sb->s_bdev;
2785         }
2786
2787         return 0;
2788 }
2789
2790
2791 /*
2792  * Find out how many pages are allowed for a single swap device. There
2793  * are two limiting factors:
2794  * 1) the number of bits for the swap offset in the swp_entry_t type, and
2795  * 2) the number of bits in the swap pte, as defined by the different
2796  * architectures.
2797  *
2798  * In order to find the largest possible bit mask, a swap entry with
2799  * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2800  * decoded to a swp_entry_t again, and finally the swap offset is
2801  * extracted.
2802  *
2803  * This will mask all the bits from the initial ~0UL mask that can't
2804  * be encoded in either the swp_entry_t or the architecture definition
2805  * of a swap pte.
2806  */
2807 unsigned long generic_max_swapfile_size(void)
2808 {
2809         return swp_offset(pte_to_swp_entry(
2810                         swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2811 }
2812
2813 /* Can be overridden by an architecture for additional checks. */
2814 __weak unsigned long arch_max_swapfile_size(void)
2815 {
2816         return generic_max_swapfile_size();
2817 }
2818
2819 static unsigned long read_swap_header(struct swap_info_struct *p,
2820                                         union swap_header *swap_header,
2821                                         struct inode *inode)
2822 {
2823         int i;
2824         unsigned long maxpages;
2825         unsigned long swapfilepages;
2826         unsigned long last_page;
2827
2828         if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2829                 pr_err("Unable to find swap-space signature\n");
2830                 return 0;
2831         }
2832
2833         /* swap partition endianness hack... */
2834         if (swab32(swap_header->info.version) == 1) {
2835                 swab32s(&swap_header->info.version);
2836                 swab32s(&swap_header->info.last_page);
2837                 swab32s(&swap_header->info.nr_badpages);
2838                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2839                         return 0;
2840                 for (i = 0; i < swap_header->info.nr_badpages; i++)
2841                         swab32s(&swap_header->info.badpages[i]);
2842         }
2843         /* Check the swap header's sub-version */
2844         if (swap_header->info.version != 1) {
2845                 pr_warn("Unable to handle swap header version %d\n",
2846                         swap_header->info.version);
2847                 return 0;
2848         }
2849
2850         p->lowest_bit  = 1;
2851         p->cluster_next = 1;
2852         p->cluster_nr = 0;
2853
2854         maxpages = swapfile_maximum_size;
2855         last_page = swap_header->info.last_page;
2856         if (!last_page) {
2857                 pr_warn("Empty swap-file\n");
2858                 return 0;
2859         }
2860         if (last_page > maxpages) {
2861                 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2862                         maxpages << (PAGE_SHIFT - 10),
2863                         last_page << (PAGE_SHIFT - 10));
2864         }
2865         if (maxpages > last_page) {
2866                 maxpages = last_page + 1;
2867                 /* p->max is an unsigned int: don't overflow it */
2868                 if ((unsigned int)maxpages == 0)
2869                         maxpages = UINT_MAX;
2870         }
2871         p->highest_bit = maxpages - 1;
2872
2873         if (!maxpages)
2874                 return 0;
2875         swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2876         if (swapfilepages && maxpages > swapfilepages) {
2877                 pr_warn("Swap area shorter than signature indicates\n");
2878                 return 0;
2879         }
2880         if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2881                 return 0;
2882         if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2883                 return 0;
2884
2885         return maxpages;
2886 }
2887
2888 #define SWAP_CLUSTER_INFO_COLS                                          \
2889         DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
2890 #define SWAP_CLUSTER_SPACE_COLS                                         \
2891         DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
2892 #define SWAP_CLUSTER_COLS                                               \
2893         max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
2894
2895 static int setup_swap_map_and_extents(struct swap_info_struct *p,
2896                                         union swap_header *swap_header,
2897                                         unsigned char *swap_map,
2898                                         struct swap_cluster_info *cluster_info,
2899                                         unsigned long maxpages,
2900                                         sector_t *span)
2901 {
2902         unsigned int j, k;
2903         unsigned int nr_good_pages;
2904         int nr_extents;
2905         unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2906         unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
2907         unsigned long i, idx;
2908
2909         nr_good_pages = maxpages - 1;   /* omit header page */
2910
2911         cluster_list_init(&p->free_clusters);
2912         cluster_list_init(&p->discard_clusters);
2913
2914         for (i = 0; i < swap_header->info.nr_badpages; i++) {
2915                 unsigned int page_nr = swap_header->info.badpages[i];
2916                 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2917                         return -EINVAL;
2918                 if (page_nr < maxpages) {
2919                         swap_map[page_nr] = SWAP_MAP_BAD;
2920                         nr_good_pages--;
2921                         /*
2922                          * Haven't marked the cluster free yet, no list
2923                          * operation involved
2924                          */
2925                         inc_cluster_info_page(p, cluster_info, page_nr);
2926                 }
2927         }
2928
2929         /* Haven't marked the cluster free yet, no list operation involved */
2930         for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2931                 inc_cluster_info_page(p, cluster_info, i);
2932
2933         if (nr_good_pages) {
2934                 swap_map[0] = SWAP_MAP_BAD;
2935                 /*
2936                  * Not mark the cluster free yet, no list
2937                  * operation involved
2938                  */
2939                 inc_cluster_info_page(p, cluster_info, 0);
2940                 p->max = maxpages;
2941                 p->pages = nr_good_pages;
2942                 nr_extents = setup_swap_extents(p, span);
2943                 if (nr_extents < 0)
2944                         return nr_extents;
2945                 nr_good_pages = p->pages;
2946         }
2947         if (!nr_good_pages) {
2948                 pr_warn("Empty swap-file\n");
2949                 return -EINVAL;
2950         }
2951
2952         if (!cluster_info)
2953                 return nr_extents;
2954
2955
2956         /*
2957          * Reduce false cache line sharing between cluster_info and
2958          * sharing same address space.
2959          */
2960         for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
2961                 j = (k + col) % SWAP_CLUSTER_COLS;
2962                 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
2963                         idx = i * SWAP_CLUSTER_COLS + j;
2964                         if (idx >= nr_clusters)
2965                                 continue;
2966                         if (cluster_count(&cluster_info[idx]))
2967                                 continue;
2968                         cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2969                         cluster_list_add_tail(&p->free_clusters, cluster_info,
2970                                               idx);
2971                 }
2972         }
2973         return nr_extents;
2974 }
2975
2976 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2977 {
2978         struct swap_info_struct *p;
2979         struct filename *name;
2980         struct file *swap_file = NULL;
2981         struct address_space *mapping;
2982         struct dentry *dentry;
2983         int prio;
2984         int error;
2985         union swap_header *swap_header;
2986         int nr_extents;
2987         sector_t span;
2988         unsigned long maxpages;
2989         unsigned char *swap_map = NULL;
2990         struct swap_cluster_info *cluster_info = NULL;
2991         unsigned long *frontswap_map = NULL;
2992         struct page *page = NULL;
2993         struct inode *inode = NULL;
2994         bool inced_nr_rotate_swap = false;
2995
2996         if (swap_flags & ~SWAP_FLAGS_VALID)
2997                 return -EINVAL;
2998
2999         if (!capable(CAP_SYS_ADMIN))
3000                 return -EPERM;
3001
3002         if (!swap_avail_heads)
3003                 return -ENOMEM;
3004
3005         p = alloc_swap_info();
3006         if (IS_ERR(p))
3007                 return PTR_ERR(p);
3008
3009         INIT_WORK(&p->discard_work, swap_discard_work);
3010
3011         name = getname(specialfile);
3012         if (IS_ERR(name)) {
3013                 error = PTR_ERR(name);
3014                 name = NULL;
3015                 goto bad_swap;
3016         }
3017         swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3018         if (IS_ERR(swap_file)) {
3019                 error = PTR_ERR(swap_file);
3020                 swap_file = NULL;
3021                 goto bad_swap;
3022         }
3023
3024         p->swap_file = swap_file;
3025         mapping = swap_file->f_mapping;
3026         dentry = swap_file->f_path.dentry;
3027         inode = mapping->host;
3028
3029         error = claim_swapfile(p, inode);
3030         if (unlikely(error))
3031                 goto bad_swap;
3032
3033         inode_lock(inode);
3034         if (d_unlinked(dentry) || cant_mount(dentry)) {
3035                 error = -ENOENT;
3036                 goto bad_swap_unlock_inode;
3037         }
3038         if (IS_SWAPFILE(inode)) {
3039                 error = -EBUSY;
3040                 goto bad_swap_unlock_inode;
3041         }
3042
3043         /*
3044          * Read the swap header.
3045          */
3046         if (!mapping->a_ops->read_folio) {
3047                 error = -EINVAL;
3048                 goto bad_swap_unlock_inode;
3049         }
3050         page = read_mapping_page(mapping, 0, swap_file);
3051         if (IS_ERR(page)) {
3052                 error = PTR_ERR(page);
3053                 goto bad_swap_unlock_inode;
3054         }
3055         swap_header = kmap(page);
3056
3057         maxpages = read_swap_header(p, swap_header, inode);
3058         if (unlikely(!maxpages)) {
3059                 error = -EINVAL;
3060                 goto bad_swap_unlock_inode;
3061         }
3062
3063         /* OK, set up the swap map and apply the bad block list */
3064         swap_map = vzalloc(maxpages);
3065         if (!swap_map) {
3066                 error = -ENOMEM;
3067                 goto bad_swap_unlock_inode;
3068         }
3069
3070         if (p->bdev && bdev_stable_writes(p->bdev))
3071                 p->flags |= SWP_STABLE_WRITES;
3072
3073         if (p->bdev && p->bdev->bd_disk->fops->rw_page)
3074                 p->flags |= SWP_SYNCHRONOUS_IO;
3075
3076         if (p->bdev && bdev_nonrot(p->bdev)) {
3077                 int cpu;
3078                 unsigned long ci, nr_cluster;
3079
3080                 p->flags |= SWP_SOLIDSTATE;
3081                 p->cluster_next_cpu = alloc_percpu(unsigned int);
3082                 if (!p->cluster_next_cpu) {
3083                         error = -ENOMEM;
3084                         goto bad_swap_unlock_inode;
3085                 }
3086                 /*
3087                  * select a random position to start with to help wear leveling
3088                  * SSD
3089                  */
3090                 for_each_possible_cpu(cpu) {
3091                         per_cpu(*p->cluster_next_cpu, cpu) =
3092                                 1 + prandom_u32_max(p->highest_bit);
3093                 }
3094                 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3095
3096                 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3097                                         GFP_KERNEL);
3098                 if (!cluster_info) {
3099                         error = -ENOMEM;
3100                         goto bad_swap_unlock_inode;
3101                 }
3102
3103                 for (ci = 0; ci < nr_cluster; ci++)
3104                         spin_lock_init(&((cluster_info + ci)->lock));
3105
3106                 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3107                 if (!p->percpu_cluster) {
3108                         error = -ENOMEM;
3109                         goto bad_swap_unlock_inode;
3110                 }
3111                 for_each_possible_cpu(cpu) {
3112                         struct percpu_cluster *cluster;
3113                         cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3114                         cluster_set_null(&cluster->index);
3115                 }
3116         } else {
3117                 atomic_inc(&nr_rotate_swap);
3118                 inced_nr_rotate_swap = true;
3119         }
3120
3121         error = swap_cgroup_swapon(p->type, maxpages);
3122         if (error)
3123                 goto bad_swap_unlock_inode;
3124
3125         nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3126                 cluster_info, maxpages, &span);
3127         if (unlikely(nr_extents < 0)) {
3128                 error = nr_extents;
3129                 goto bad_swap_unlock_inode;
3130         }
3131         /* frontswap enabled? set up bit-per-page map for frontswap */
3132         if (IS_ENABLED(CONFIG_FRONTSWAP))
3133                 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3134                                          sizeof(long),
3135                                          GFP_KERNEL);
3136
3137         if ((swap_flags & SWAP_FLAG_DISCARD) &&
3138             p->bdev && bdev_max_discard_sectors(p->bdev)) {
3139                 /*
3140                  * When discard is enabled for swap with no particular
3141                  * policy flagged, we set all swap discard flags here in
3142                  * order to sustain backward compatibility with older
3143                  * swapon(8) releases.
3144                  */
3145                 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3146                              SWP_PAGE_DISCARD);
3147
3148                 /*
3149                  * By flagging sys_swapon, a sysadmin can tell us to
3150                  * either do single-time area discards only, or to just
3151                  * perform discards for released swap page-clusters.
3152                  * Now it's time to adjust the p->flags accordingly.
3153                  */
3154                 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3155                         p->flags &= ~SWP_PAGE_DISCARD;
3156                 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3157                         p->flags &= ~SWP_AREA_DISCARD;
3158
3159                 /* issue a swapon-time discard if it's still required */
3160                 if (p->flags & SWP_AREA_DISCARD) {
3161                         int err = discard_swap(p);
3162                         if (unlikely(err))
3163                                 pr_err("swapon: discard_swap(%p): %d\n",
3164                                         p, err);
3165                 }
3166         }
3167
3168         error = init_swap_address_space(p->type, maxpages);
3169         if (error)
3170                 goto bad_swap_unlock_inode;
3171
3172         /*
3173          * Flush any pending IO and dirty mappings before we start using this
3174          * swap device.
3175          */
3176         inode->i_flags |= S_SWAPFILE;
3177         error = inode_drain_writes(inode);
3178         if (error) {
3179                 inode->i_flags &= ~S_SWAPFILE;
3180                 goto free_swap_address_space;
3181         }
3182
3183         mutex_lock(&swapon_mutex);
3184         prio = -1;
3185         if (swap_flags & SWAP_FLAG_PREFER)
3186                 prio =
3187                   (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3188         enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3189
3190         pr_info("Adding %uk swap on %s.  Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3191                 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3192                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3193                 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3194                 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3195                 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3196                 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3197                 (frontswap_map) ? "FS" : "");
3198
3199         mutex_unlock(&swapon_mutex);
3200         atomic_inc(&proc_poll_event);
3201         wake_up_interruptible(&proc_poll_wait);
3202
3203         error = 0;
3204         goto out;
3205 free_swap_address_space:
3206         exit_swap_address_space(p->type);
3207 bad_swap_unlock_inode:
3208         inode_unlock(inode);
3209 bad_swap:
3210         free_percpu(p->percpu_cluster);
3211         p->percpu_cluster = NULL;
3212         free_percpu(p->cluster_next_cpu);
3213         p->cluster_next_cpu = NULL;
3214         if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3215                 set_blocksize(p->bdev, p->old_block_size);
3216                 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3217         }
3218         inode = NULL;
3219         destroy_swap_extents(p);
3220         swap_cgroup_swapoff(p->type);
3221         spin_lock(&swap_lock);
3222         p->swap_file = NULL;
3223         p->flags = 0;
3224         spin_unlock(&swap_lock);
3225         vfree(swap_map);
3226         kvfree(cluster_info);
3227         kvfree(frontswap_map);
3228         if (inced_nr_rotate_swap)
3229                 atomic_dec(&nr_rotate_swap);
3230         if (swap_file)
3231                 filp_close(swap_file, NULL);
3232 out:
3233         if (page && !IS_ERR(page)) {
3234                 kunmap(page);
3235                 put_page(page);
3236         }
3237         if (name)
3238                 putname(name);
3239         if (inode)
3240                 inode_unlock(inode);
3241         if (!error)
3242                 enable_swap_slots_cache();
3243         return error;
3244 }
3245
3246 void si_swapinfo(struct sysinfo *val)
3247 {
3248         unsigned int type;
3249         unsigned long nr_to_be_unused = 0;
3250
3251         spin_lock(&swap_lock);
3252         for (type = 0; type < nr_swapfiles; type++) {
3253                 struct swap_info_struct *si = swap_info[type];
3254
3255                 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3256                         nr_to_be_unused += READ_ONCE(si->inuse_pages);
3257         }
3258         val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3259         val->totalswap = total_swap_pages + nr_to_be_unused;
3260         spin_unlock(&swap_lock);
3261 }
3262
3263 /*
3264  * Verify that a swap entry is valid and increment its swap map count.
3265  *
3266  * Returns error code in following case.
3267  * - success -> 0
3268  * - swp_entry is invalid -> EINVAL
3269  * - swp_entry is migration entry -> EINVAL
3270  * - swap-cache reference is requested but there is already one. -> EEXIST
3271  * - swap-cache reference is requested but the entry is not used. -> ENOENT
3272  * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3273  */
3274 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3275 {
3276         struct swap_info_struct *p;
3277         struct swap_cluster_info *ci;
3278         unsigned long offset;
3279         unsigned char count;
3280         unsigned char has_cache;
3281         int err;
3282
3283         p = get_swap_device(entry);
3284         if (!p)
3285                 return -EINVAL;
3286
3287         offset = swp_offset(entry);
3288         ci = lock_cluster_or_swap_info(p, offset);
3289
3290         count = p->swap_map[offset];
3291
3292         /*
3293          * swapin_readahead() doesn't check if a swap entry is valid, so the
3294          * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3295          */
3296         if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3297                 err = -ENOENT;
3298                 goto unlock_out;
3299         }
3300
3301         has_cache = count & SWAP_HAS_CACHE;
3302         count &= ~SWAP_HAS_CACHE;
3303         err = 0;
3304
3305         if (usage == SWAP_HAS_CACHE) {
3306
3307                 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3308                 if (!has_cache && count)
3309                         has_cache = SWAP_HAS_CACHE;
3310                 else if (has_cache)             /* someone else added cache */
3311                         err = -EEXIST;
3312                 else                            /* no users remaining */
3313                         err = -ENOENT;
3314
3315         } else if (count || has_cache) {
3316
3317                 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3318                         count += usage;
3319                 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3320                         err = -EINVAL;
3321                 else if (swap_count_continued(p, offset, count))
3322                         count = COUNT_CONTINUED;
3323                 else
3324                         err = -ENOMEM;
3325         } else
3326                 err = -ENOENT;                  /* unused swap entry */
3327
3328         WRITE_ONCE(p->swap_map[offset], count | has_cache);
3329
3330 unlock_out:
3331         unlock_cluster_or_swap_info(p, ci);
3332         put_swap_device(p);
3333         return err;
3334 }
3335
3336 /*
3337  * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3338  * (in which case its reference count is never incremented).
3339  */
3340 void swap_shmem_alloc(swp_entry_t entry)
3341 {
3342         __swap_duplicate(entry, SWAP_MAP_SHMEM);
3343 }
3344
3345 /*
3346  * Increase reference count of swap entry by 1.
3347  * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3348  * but could not be atomically allocated.  Returns 0, just as if it succeeded,
3349  * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3350  * might occur if a page table entry has got corrupted.
3351  */
3352 int swap_duplicate(swp_entry_t entry)
3353 {
3354         int err = 0;
3355
3356         while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3357                 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3358         return err;
3359 }
3360
3361 /*
3362  * @entry: swap entry for which we allocate swap cache.
3363  *
3364  * Called when allocating swap cache for existing swap entry,
3365  * This can return error codes. Returns 0 at success.
3366  * -EEXIST means there is a swap cache.
3367  * Note: return code is different from swap_duplicate().
3368  */
3369 int swapcache_prepare(swp_entry_t entry)
3370 {
3371         return __swap_duplicate(entry, SWAP_HAS_CACHE);
3372 }
3373
3374 struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3375 {
3376         return swap_type_to_swap_info(swp_type(entry));
3377 }
3378
3379 struct swap_info_struct *page_swap_info(struct page *page)
3380 {
3381         swp_entry_t entry = { .val = page_private(page) };
3382         return swp_swap_info(entry);
3383 }
3384
3385 /*
3386  * out-of-line methods to avoid include hell.
3387  */
3388 struct address_space *swapcache_mapping(struct folio *folio)
3389 {
3390         return page_swap_info(&folio->page)->swap_file->f_mapping;
3391 }
3392 EXPORT_SYMBOL_GPL(swapcache_mapping);
3393
3394 pgoff_t __page_file_index(struct page *page)
3395 {
3396         swp_entry_t swap = { .val = page_private(page) };
3397         return swp_offset(swap);
3398 }
3399 EXPORT_SYMBOL_GPL(__page_file_index);
3400
3401 /*
3402  * add_swap_count_continuation - called when a swap count is duplicated
3403  * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3404  * page of the original vmalloc'ed swap_map, to hold the continuation count
3405  * (for that entry and for its neighbouring PAGE_SIZE swap entries).  Called
3406  * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3407  *
3408  * These continuation pages are seldom referenced: the common paths all work
3409  * on the original swap_map, only referring to a continuation page when the
3410  * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3411  *
3412  * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3413  * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3414  * can be called after dropping locks.
3415  */
3416 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3417 {
3418         struct swap_info_struct *si;
3419         struct swap_cluster_info *ci;
3420         struct page *head;
3421         struct page *page;
3422         struct page *list_page;
3423         pgoff_t offset;
3424         unsigned char count;
3425         int ret = 0;
3426
3427         /*
3428          * When debugging, it's easier to use __GFP_ZERO here; but it's better
3429          * for latency not to zero a page while GFP_ATOMIC and holding locks.
3430          */
3431         page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3432
3433         si = get_swap_device(entry);
3434         if (!si) {
3435                 /*
3436                  * An acceptable race has occurred since the failing
3437                  * __swap_duplicate(): the swap device may be swapoff
3438                  */
3439                 goto outer;
3440         }
3441         spin_lock(&si->lock);
3442
3443         offset = swp_offset(entry);
3444
3445         ci = lock_cluster(si, offset);
3446
3447         count = swap_count(si->swap_map[offset]);
3448
3449         if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3450                 /*
3451                  * The higher the swap count, the more likely it is that tasks
3452                  * will race to add swap count continuation: we need to avoid
3453                  * over-provisioning.
3454                  */
3455                 goto out;
3456         }
3457
3458         if (!page) {
3459                 ret = -ENOMEM;
3460                 goto out;
3461         }
3462
3463         /*
3464          * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3465          * no architecture is using highmem pages for kernel page tables: so it
3466          * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3467          */
3468         head = vmalloc_to_page(si->swap_map + offset);
3469         offset &= ~PAGE_MASK;
3470
3471         spin_lock(&si->cont_lock);
3472         /*
3473          * Page allocation does not initialize the page's lru field,
3474          * but it does always reset its private field.
3475          */
3476         if (!page_private(head)) {
3477                 BUG_ON(count & COUNT_CONTINUED);
3478                 INIT_LIST_HEAD(&head->lru);
3479                 set_page_private(head, SWP_CONTINUED);
3480                 si->flags |= SWP_CONTINUED;
3481         }
3482
3483         list_for_each_entry(list_page, &head->lru, lru) {
3484                 unsigned char *map;
3485
3486                 /*
3487                  * If the previous map said no continuation, but we've found
3488                  * a continuation page, free our allocation and use this one.
3489                  */
3490                 if (!(count & COUNT_CONTINUED))
3491                         goto out_unlock_cont;
3492
3493                 map = kmap_atomic(list_page) + offset;
3494                 count = *map;
3495                 kunmap_atomic(map);
3496
3497                 /*
3498                  * If this continuation count now has some space in it,
3499                  * free our allocation and use this one.
3500                  */
3501                 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3502                         goto out_unlock_cont;
3503         }
3504
3505         list_add_tail(&page->lru, &head->lru);
3506         page = NULL;                    /* now it's attached, don't free it */
3507 out_unlock_cont:
3508         spin_unlock(&si->cont_lock);
3509 out:
3510         unlock_cluster(ci);
3511         spin_unlock(&si->lock);
3512         put_swap_device(si);
3513 outer:
3514         if (page)
3515                 __free_page(page);
3516         return ret;
3517 }
3518
3519 /*
3520  * swap_count_continued - when the original swap_map count is incremented
3521  * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3522  * into, carry if so, or else fail until a new continuation page is allocated;
3523  * when the original swap_map count is decremented from 0 with continuation,
3524  * borrow from the continuation and report whether it still holds more.
3525  * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3526  * lock.
3527  */
3528 static bool swap_count_continued(struct swap_info_struct *si,
3529                                  pgoff_t offset, unsigned char count)
3530 {
3531         struct page *head;
3532         struct page *page;
3533         unsigned char *map;
3534         bool ret;
3535
3536         head = vmalloc_to_page(si->swap_map + offset);
3537         if (page_private(head) != SWP_CONTINUED) {
3538                 BUG_ON(count & COUNT_CONTINUED);
3539                 return false;           /* need to add count continuation */
3540         }
3541
3542         spin_lock(&si->cont_lock);
3543         offset &= ~PAGE_MASK;
3544         page = list_next_entry(head, lru);
3545         map = kmap_atomic(page) + offset;
3546
3547         if (count == SWAP_MAP_MAX)      /* initial increment from swap_map */
3548                 goto init_map;          /* jump over SWAP_CONT_MAX checks */
3549
3550         if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3551                 /*
3552                  * Think of how you add 1 to 999
3553                  */
3554                 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3555                         kunmap_atomic(map);
3556                         page = list_next_entry(page, lru);
3557                         BUG_ON(page == head);
3558                         map = kmap_atomic(page) + offset;
3559                 }
3560                 if (*map == SWAP_CONT_MAX) {
3561                         kunmap_atomic(map);
3562                         page = list_next_entry(page, lru);
3563                         if (page == head) {
3564                                 ret = false;    /* add count continuation */
3565                                 goto out;
3566                         }
3567                         map = kmap_atomic(page) + offset;
3568 init_map:               *map = 0;               /* we didn't zero the page */
3569                 }
3570                 *map += 1;
3571                 kunmap_atomic(map);
3572                 while ((page = list_prev_entry(page, lru)) != head) {
3573                         map = kmap_atomic(page) + offset;
3574                         *map = COUNT_CONTINUED;
3575                         kunmap_atomic(map);
3576                 }
3577                 ret = true;                     /* incremented */
3578
3579         } else {                                /* decrementing */
3580                 /*
3581                  * Think of how you subtract 1 from 1000
3582                  */
3583                 BUG_ON(count != COUNT_CONTINUED);
3584                 while (*map == COUNT_CONTINUED) {
3585                         kunmap_atomic(map);
3586                         page = list_next_entry(page, lru);
3587                         BUG_ON(page == head);
3588                         map = kmap_atomic(page) + offset;
3589                 }
3590                 BUG_ON(*map == 0);
3591                 *map -= 1;
3592                 if (*map == 0)
3593                         count = 0;
3594                 kunmap_atomic(map);
3595                 while ((page = list_prev_entry(page, lru)) != head) {
3596                         map = kmap_atomic(page) + offset;
3597                         *map = SWAP_CONT_MAX | count;
3598                         count = COUNT_CONTINUED;
3599                         kunmap_atomic(map);
3600                 }
3601                 ret = count == COUNT_CONTINUED;
3602         }
3603 out:
3604         spin_unlock(&si->cont_lock);
3605         return ret;
3606 }
3607
3608 /*
3609  * free_swap_count_continuations - swapoff free all the continuation pages
3610  * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3611  */
3612 static void free_swap_count_continuations(struct swap_info_struct *si)
3613 {
3614         pgoff_t offset;
3615
3616         for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3617                 struct page *head;
3618                 head = vmalloc_to_page(si->swap_map + offset);
3619                 if (page_private(head)) {
3620                         struct page *page, *next;
3621
3622                         list_for_each_entry_safe(page, next, &head->lru, lru) {
3623                                 list_del(&page->lru);
3624                                 __free_page(page);
3625                         }
3626                 }
3627         }
3628 }
3629
3630 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3631 void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
3632 {
3633         struct swap_info_struct *si, *next;
3634         int nid = page_to_nid(page);
3635
3636         if (!(gfp_mask & __GFP_IO))
3637                 return;
3638
3639         if (!blk_cgroup_congested())
3640                 return;
3641
3642         /*
3643          * We've already scheduled a throttle, avoid taking the global swap
3644          * lock.
3645          */
3646         if (current->throttle_queue)
3647                 return;
3648
3649         spin_lock(&swap_avail_lock);
3650         plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
3651                                   avail_lists[nid]) {
3652                 if (si->bdev) {
3653                         blkcg_schedule_throttle(si->bdev->bd_disk, true);
3654                         break;
3655                 }
3656         }
3657         spin_unlock(&swap_avail_lock);
3658 }
3659 #endif
3660
3661 static int __init swapfile_init(void)
3662 {
3663         int nid;
3664
3665         swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3666                                          GFP_KERNEL);
3667         if (!swap_avail_heads) {
3668                 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3669                 return -ENOMEM;
3670         }
3671
3672         for_each_node(nid)
3673                 plist_head_init(&swap_avail_heads[nid]);
3674
3675         swapfile_maximum_size = arch_max_swapfile_size();
3676
3677 #ifdef CONFIG_MIGRATION
3678         if (swapfile_maximum_size >= (1UL << SWP_MIG_TOTAL_BITS))
3679                 swap_migration_ad_supported = true;
3680 #endif  /* CONFIG_MIGRATION */
3681
3682         return 0;
3683 }
3684 subsys_initcall(swapfile_init);