Merge tag 'timers-core-2022-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux-2.6-microblaze.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
67 static const char Bad_file[] = "Bad swap file entry ";
68 static const char Unused_file[] = "Unused swap file entry ";
69 static const char Bad_offset[] = "Bad swap offset entry ";
70 static const char Unused_offset[] = "Unused swap offset entry ";
71
72 /*
73  * all active swap_info_structs
74  * protected with swap_lock, and ordered by priority.
75  */
76 static PLIST_HEAD(swap_active_head);
77
78 /*
79  * all available (active, not full) swap_info_structs
80  * protected with swap_avail_lock, ordered by priority.
81  * This is used by folio_alloc_swap() instead of swap_active_head
82  * because swap_active_head includes all swap_info_structs,
83  * but folio_alloc_swap() doesn't need to look at full ones.
84  * This uses its own lock instead of swap_lock because when a
85  * swap_info_struct changes between not-full/full, it needs to
86  * add/remove itself to/from this list, but the swap_info_struct->lock
87  * is held and the locking order requires swap_lock to be taken
88  * before any swap_info_struct->lock.
89  */
90 static struct plist_head *swap_avail_heads;
91 static DEFINE_SPINLOCK(swap_avail_lock);
92
93 struct swap_info_struct *swap_info[MAX_SWAPFILES];
94
95 static DEFINE_MUTEX(swapon_mutex);
96
97 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
98 /* Activity counter to indicate that a swapon or swapoff has occurred */
99 static atomic_t proc_poll_event = ATOMIC_INIT(0);
100
101 atomic_t nr_rotate_swap = ATOMIC_INIT(0);
102
103 static struct swap_info_struct *swap_type_to_swap_info(int type)
104 {
105         if (type >= MAX_SWAPFILES)
106                 return NULL;
107
108         return READ_ONCE(swap_info[type]); /* rcu_dereference() */
109 }
110
111 static inline unsigned char swap_count(unsigned char ent)
112 {
113         return ent & ~SWAP_HAS_CACHE;   /* may include COUNT_CONTINUED flag */
114 }
115
116 /* Reclaim the swap entry anyway if possible */
117 #define TTRS_ANYWAY             0x1
118 /*
119  * Reclaim the swap entry if there are no more mappings of the
120  * corresponding page
121  */
122 #define TTRS_UNMAPPED           0x2
123 /* Reclaim the swap entry if swap is getting full*/
124 #define TTRS_FULL               0x4
125
126 /* returns 1 if swap entry is freed */
127 static int __try_to_reclaim_swap(struct swap_info_struct *si,
128                                  unsigned long offset, unsigned long flags)
129 {
130         swp_entry_t entry = swp_entry(si->type, offset);
131         struct page *page;
132         int ret = 0;
133
134         page = find_get_page(swap_address_space(entry), offset);
135         if (!page)
136                 return 0;
137         /*
138          * When this function is called from scan_swap_map_slots() and it's
139          * called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
140          * here. We have to use trylock for avoiding deadlock. This is a special
141          * case and you should use try_to_free_swap() with explicit lock_page()
142          * in usual operations.
143          */
144         if (trylock_page(page)) {
145                 if ((flags & TTRS_ANYWAY) ||
146                     ((flags & TTRS_UNMAPPED) && !page_mapped(page)) ||
147                     ((flags & TTRS_FULL) && mem_cgroup_swap_full(page)))
148                         ret = try_to_free_swap(page);
149                 unlock_page(page);
150         }
151         put_page(page);
152         return ret;
153 }
154
155 static inline struct swap_extent *first_se(struct swap_info_struct *sis)
156 {
157         struct rb_node *rb = rb_first(&sis->swap_extent_root);
158         return rb_entry(rb, struct swap_extent, rb_node);
159 }
160
161 static inline struct swap_extent *next_se(struct swap_extent *se)
162 {
163         struct rb_node *rb = rb_next(&se->rb_node);
164         return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
165 }
166
167 /*
168  * swapon tell device that all the old swap contents can be discarded,
169  * to allow the swap device to optimize its wear-levelling.
170  */
171 static int discard_swap(struct swap_info_struct *si)
172 {
173         struct swap_extent *se;
174         sector_t start_block;
175         sector_t nr_blocks;
176         int err = 0;
177
178         /* Do not discard the swap header page! */
179         se = first_se(si);
180         start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
181         nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
182         if (nr_blocks) {
183                 err = blkdev_issue_discard(si->bdev, start_block,
184                                 nr_blocks, GFP_KERNEL);
185                 if (err)
186                         return err;
187                 cond_resched();
188         }
189
190         for (se = next_se(se); se; se = next_se(se)) {
191                 start_block = se->start_block << (PAGE_SHIFT - 9);
192                 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
193
194                 err = blkdev_issue_discard(si->bdev, start_block,
195                                 nr_blocks, GFP_KERNEL);
196                 if (err)
197                         break;
198
199                 cond_resched();
200         }
201         return err;             /* That will often be -EOPNOTSUPP */
202 }
203
204 static struct swap_extent *
205 offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
206 {
207         struct swap_extent *se;
208         struct rb_node *rb;
209
210         rb = sis->swap_extent_root.rb_node;
211         while (rb) {
212                 se = rb_entry(rb, struct swap_extent, rb_node);
213                 if (offset < se->start_page)
214                         rb = rb->rb_left;
215                 else if (offset >= se->start_page + se->nr_pages)
216                         rb = rb->rb_right;
217                 else
218                         return se;
219         }
220         /* It *must* be present */
221         BUG();
222 }
223
224 sector_t swap_page_sector(struct page *page)
225 {
226         struct swap_info_struct *sis = page_swap_info(page);
227         struct swap_extent *se;
228         sector_t sector;
229         pgoff_t offset;
230
231         offset = __page_file_index(page);
232         se = offset_to_swap_extent(sis, offset);
233         sector = se->start_block + (offset - se->start_page);
234         return sector << (PAGE_SHIFT - 9);
235 }
236
237 /*
238  * swap allocation tell device that a cluster of swap can now be discarded,
239  * to allow the swap device to optimize its wear-levelling.
240  */
241 static void discard_swap_cluster(struct swap_info_struct *si,
242                                  pgoff_t start_page, pgoff_t nr_pages)
243 {
244         struct swap_extent *se = offset_to_swap_extent(si, start_page);
245
246         while (nr_pages) {
247                 pgoff_t offset = start_page - se->start_page;
248                 sector_t start_block = se->start_block + offset;
249                 sector_t nr_blocks = se->nr_pages - offset;
250
251                 if (nr_blocks > nr_pages)
252                         nr_blocks = nr_pages;
253                 start_page += nr_blocks;
254                 nr_pages -= nr_blocks;
255
256                 start_block <<= PAGE_SHIFT - 9;
257                 nr_blocks <<= PAGE_SHIFT - 9;
258                 if (blkdev_issue_discard(si->bdev, start_block,
259                                         nr_blocks, GFP_NOIO))
260                         break;
261
262                 se = next_se(se);
263         }
264 }
265
266 #ifdef CONFIG_THP_SWAP
267 #define SWAPFILE_CLUSTER        HPAGE_PMD_NR
268
269 #define swap_entry_size(size)   (size)
270 #else
271 #define SWAPFILE_CLUSTER        256
272
273 /*
274  * Define swap_entry_size() as constant to let compiler to optimize
275  * out some code if !CONFIG_THP_SWAP
276  */
277 #define swap_entry_size(size)   1
278 #endif
279 #define LATENCY_LIMIT           256
280
281 static inline void cluster_set_flag(struct swap_cluster_info *info,
282         unsigned int flag)
283 {
284         info->flags = flag;
285 }
286
287 static inline unsigned int cluster_count(struct swap_cluster_info *info)
288 {
289         return info->data;
290 }
291
292 static inline void cluster_set_count(struct swap_cluster_info *info,
293                                      unsigned int c)
294 {
295         info->data = c;
296 }
297
298 static inline void cluster_set_count_flag(struct swap_cluster_info *info,
299                                          unsigned int c, unsigned int f)
300 {
301         info->flags = f;
302         info->data = c;
303 }
304
305 static inline unsigned int cluster_next(struct swap_cluster_info *info)
306 {
307         return info->data;
308 }
309
310 static inline void cluster_set_next(struct swap_cluster_info *info,
311                                     unsigned int n)
312 {
313         info->data = n;
314 }
315
316 static inline void cluster_set_next_flag(struct swap_cluster_info *info,
317                                          unsigned int n, unsigned int f)
318 {
319         info->flags = f;
320         info->data = n;
321 }
322
323 static inline bool cluster_is_free(struct swap_cluster_info *info)
324 {
325         return info->flags & CLUSTER_FLAG_FREE;
326 }
327
328 static inline bool cluster_is_null(struct swap_cluster_info *info)
329 {
330         return info->flags & CLUSTER_FLAG_NEXT_NULL;
331 }
332
333 static inline void cluster_set_null(struct swap_cluster_info *info)
334 {
335         info->flags = CLUSTER_FLAG_NEXT_NULL;
336         info->data = 0;
337 }
338
339 static inline bool cluster_is_huge(struct swap_cluster_info *info)
340 {
341         if (IS_ENABLED(CONFIG_THP_SWAP))
342                 return info->flags & CLUSTER_FLAG_HUGE;
343         return false;
344 }
345
346 static inline void cluster_clear_huge(struct swap_cluster_info *info)
347 {
348         info->flags &= ~CLUSTER_FLAG_HUGE;
349 }
350
351 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
352                                                      unsigned long offset)
353 {
354         struct swap_cluster_info *ci;
355
356         ci = si->cluster_info;
357         if (ci) {
358                 ci += offset / SWAPFILE_CLUSTER;
359                 spin_lock(&ci->lock);
360         }
361         return ci;
362 }
363
364 static inline void unlock_cluster(struct swap_cluster_info *ci)
365 {
366         if (ci)
367                 spin_unlock(&ci->lock);
368 }
369
370 /*
371  * Determine the locking method in use for this device.  Return
372  * swap_cluster_info if SSD-style cluster-based locking is in place.
373  */
374 static inline struct swap_cluster_info *lock_cluster_or_swap_info(
375                 struct swap_info_struct *si, unsigned long offset)
376 {
377         struct swap_cluster_info *ci;
378
379         /* Try to use fine-grained SSD-style locking if available: */
380         ci = lock_cluster(si, offset);
381         /* Otherwise, fall back to traditional, coarse locking: */
382         if (!ci)
383                 spin_lock(&si->lock);
384
385         return ci;
386 }
387
388 static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
389                                                struct swap_cluster_info *ci)
390 {
391         if (ci)
392                 unlock_cluster(ci);
393         else
394                 spin_unlock(&si->lock);
395 }
396
397 static inline bool cluster_list_empty(struct swap_cluster_list *list)
398 {
399         return cluster_is_null(&list->head);
400 }
401
402 static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
403 {
404         return cluster_next(&list->head);
405 }
406
407 static void cluster_list_init(struct swap_cluster_list *list)
408 {
409         cluster_set_null(&list->head);
410         cluster_set_null(&list->tail);
411 }
412
413 static void cluster_list_add_tail(struct swap_cluster_list *list,
414                                   struct swap_cluster_info *ci,
415                                   unsigned int idx)
416 {
417         if (cluster_list_empty(list)) {
418                 cluster_set_next_flag(&list->head, idx, 0);
419                 cluster_set_next_flag(&list->tail, idx, 0);
420         } else {
421                 struct swap_cluster_info *ci_tail;
422                 unsigned int tail = cluster_next(&list->tail);
423
424                 /*
425                  * Nested cluster lock, but both cluster locks are
426                  * only acquired when we held swap_info_struct->lock
427                  */
428                 ci_tail = ci + tail;
429                 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
430                 cluster_set_next(ci_tail, idx);
431                 spin_unlock(&ci_tail->lock);
432                 cluster_set_next_flag(&list->tail, idx, 0);
433         }
434 }
435
436 static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
437                                            struct swap_cluster_info *ci)
438 {
439         unsigned int idx;
440
441         idx = cluster_next(&list->head);
442         if (cluster_next(&list->tail) == idx) {
443                 cluster_set_null(&list->head);
444                 cluster_set_null(&list->tail);
445         } else
446                 cluster_set_next_flag(&list->head,
447                                       cluster_next(&ci[idx]), 0);
448
449         return idx;
450 }
451
452 /* Add a cluster to discard list and schedule it to do discard */
453 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
454                 unsigned int idx)
455 {
456         /*
457          * If scan_swap_map_slots() can't find a free cluster, it will check
458          * si->swap_map directly. To make sure the discarding cluster isn't
459          * taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
460          * It will be cleared after discard
461          */
462         memset(si->swap_map + idx * SWAPFILE_CLUSTER,
463                         SWAP_MAP_BAD, SWAPFILE_CLUSTER);
464
465         cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
466
467         schedule_work(&si->discard_work);
468 }
469
470 static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
471 {
472         struct swap_cluster_info *ci = si->cluster_info;
473
474         cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
475         cluster_list_add_tail(&si->free_clusters, ci, idx);
476 }
477
478 /*
479  * Doing discard actually. After a cluster discard is finished, the cluster
480  * will be added to free cluster list. caller should hold si->lock.
481 */
482 static void swap_do_scheduled_discard(struct swap_info_struct *si)
483 {
484         struct swap_cluster_info *info, *ci;
485         unsigned int idx;
486
487         info = si->cluster_info;
488
489         while (!cluster_list_empty(&si->discard_clusters)) {
490                 idx = cluster_list_del_first(&si->discard_clusters, info);
491                 spin_unlock(&si->lock);
492
493                 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
494                                 SWAPFILE_CLUSTER);
495
496                 spin_lock(&si->lock);
497                 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
498                 __free_cluster(si, idx);
499                 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
500                                 0, SWAPFILE_CLUSTER);
501                 unlock_cluster(ci);
502         }
503 }
504
505 static void swap_discard_work(struct work_struct *work)
506 {
507         struct swap_info_struct *si;
508
509         si = container_of(work, struct swap_info_struct, discard_work);
510
511         spin_lock(&si->lock);
512         swap_do_scheduled_discard(si);
513         spin_unlock(&si->lock);
514 }
515
516 static void swap_users_ref_free(struct percpu_ref *ref)
517 {
518         struct swap_info_struct *si;
519
520         si = container_of(ref, struct swap_info_struct, users);
521         complete(&si->comp);
522 }
523
524 static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
525 {
526         struct swap_cluster_info *ci = si->cluster_info;
527
528         VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
529         cluster_list_del_first(&si->free_clusters, ci);
530         cluster_set_count_flag(ci + idx, 0, 0);
531 }
532
533 static void free_cluster(struct swap_info_struct *si, unsigned long idx)
534 {
535         struct swap_cluster_info *ci = si->cluster_info + idx;
536
537         VM_BUG_ON(cluster_count(ci) != 0);
538         /*
539          * If the swap is discardable, prepare discard the cluster
540          * instead of free it immediately. The cluster will be freed
541          * after discard.
542          */
543         if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
544             (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
545                 swap_cluster_schedule_discard(si, idx);
546                 return;
547         }
548
549         __free_cluster(si, idx);
550 }
551
552 /*
553  * The cluster corresponding to page_nr will be used. The cluster will be
554  * removed from free cluster list and its usage counter will be increased.
555  */
556 static void inc_cluster_info_page(struct swap_info_struct *p,
557         struct swap_cluster_info *cluster_info, unsigned long page_nr)
558 {
559         unsigned long idx = page_nr / SWAPFILE_CLUSTER;
560
561         if (!cluster_info)
562                 return;
563         if (cluster_is_free(&cluster_info[idx]))
564                 alloc_cluster(p, idx);
565
566         VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
567         cluster_set_count(&cluster_info[idx],
568                 cluster_count(&cluster_info[idx]) + 1);
569 }
570
571 /*
572  * The cluster corresponding to page_nr decreases one usage. If the usage
573  * counter becomes 0, which means no page in the cluster is in using, we can
574  * optionally discard the cluster and add it to free cluster list.
575  */
576 static void dec_cluster_info_page(struct swap_info_struct *p,
577         struct swap_cluster_info *cluster_info, unsigned long page_nr)
578 {
579         unsigned long idx = page_nr / SWAPFILE_CLUSTER;
580
581         if (!cluster_info)
582                 return;
583
584         VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
585         cluster_set_count(&cluster_info[idx],
586                 cluster_count(&cluster_info[idx]) - 1);
587
588         if (cluster_count(&cluster_info[idx]) == 0)
589                 free_cluster(p, idx);
590 }
591
592 /*
593  * It's possible scan_swap_map_slots() uses a free cluster in the middle of free
594  * cluster list. Avoiding such abuse to avoid list corruption.
595  */
596 static bool
597 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
598         unsigned long offset)
599 {
600         struct percpu_cluster *percpu_cluster;
601         bool conflict;
602
603         offset /= SWAPFILE_CLUSTER;
604         conflict = !cluster_list_empty(&si->free_clusters) &&
605                 offset != cluster_list_first(&si->free_clusters) &&
606                 cluster_is_free(&si->cluster_info[offset]);
607
608         if (!conflict)
609                 return false;
610
611         percpu_cluster = this_cpu_ptr(si->percpu_cluster);
612         cluster_set_null(&percpu_cluster->index);
613         return true;
614 }
615
616 /*
617  * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
618  * might involve allocating a new cluster for current CPU too.
619  */
620 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
621         unsigned long *offset, unsigned long *scan_base)
622 {
623         struct percpu_cluster *cluster;
624         struct swap_cluster_info *ci;
625         unsigned long tmp, max;
626
627 new_cluster:
628         cluster = this_cpu_ptr(si->percpu_cluster);
629         if (cluster_is_null(&cluster->index)) {
630                 if (!cluster_list_empty(&si->free_clusters)) {
631                         cluster->index = si->free_clusters.head;
632                         cluster->next = cluster_next(&cluster->index) *
633                                         SWAPFILE_CLUSTER;
634                 } else if (!cluster_list_empty(&si->discard_clusters)) {
635                         /*
636                          * we don't have free cluster but have some clusters in
637                          * discarding, do discard now and reclaim them, then
638                          * reread cluster_next_cpu since we dropped si->lock
639                          */
640                         swap_do_scheduled_discard(si);
641                         *scan_base = this_cpu_read(*si->cluster_next_cpu);
642                         *offset = *scan_base;
643                         goto new_cluster;
644                 } else
645                         return false;
646         }
647
648         /*
649          * Other CPUs can use our cluster if they can't find a free cluster,
650          * check if there is still free entry in the cluster
651          */
652         tmp = cluster->next;
653         max = min_t(unsigned long, si->max,
654                     (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
655         if (tmp < max) {
656                 ci = lock_cluster(si, tmp);
657                 while (tmp < max) {
658                         if (!si->swap_map[tmp])
659                                 break;
660                         tmp++;
661                 }
662                 unlock_cluster(ci);
663         }
664         if (tmp >= max) {
665                 cluster_set_null(&cluster->index);
666                 goto new_cluster;
667         }
668         cluster->next = tmp + 1;
669         *offset = tmp;
670         *scan_base = tmp;
671         return true;
672 }
673
674 static void __del_from_avail_list(struct swap_info_struct *p)
675 {
676         int nid;
677
678         for_each_node(nid)
679                 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
680 }
681
682 static void del_from_avail_list(struct swap_info_struct *p)
683 {
684         spin_lock(&swap_avail_lock);
685         __del_from_avail_list(p);
686         spin_unlock(&swap_avail_lock);
687 }
688
689 static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
690                              unsigned int nr_entries)
691 {
692         unsigned int end = offset + nr_entries - 1;
693
694         if (offset == si->lowest_bit)
695                 si->lowest_bit += nr_entries;
696         if (end == si->highest_bit)
697                 WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
698         si->inuse_pages += nr_entries;
699         if (si->inuse_pages == si->pages) {
700                 si->lowest_bit = si->max;
701                 si->highest_bit = 0;
702                 del_from_avail_list(si);
703         }
704 }
705
706 static void add_to_avail_list(struct swap_info_struct *p)
707 {
708         int nid;
709
710         spin_lock(&swap_avail_lock);
711         for_each_node(nid) {
712                 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
713                 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
714         }
715         spin_unlock(&swap_avail_lock);
716 }
717
718 static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
719                             unsigned int nr_entries)
720 {
721         unsigned long begin = offset;
722         unsigned long end = offset + nr_entries - 1;
723         void (*swap_slot_free_notify)(struct block_device *, unsigned long);
724
725         if (offset < si->lowest_bit)
726                 si->lowest_bit = offset;
727         if (end > si->highest_bit) {
728                 bool was_full = !si->highest_bit;
729
730                 WRITE_ONCE(si->highest_bit, end);
731                 if (was_full && (si->flags & SWP_WRITEOK))
732                         add_to_avail_list(si);
733         }
734         atomic_long_add(nr_entries, &nr_swap_pages);
735         si->inuse_pages -= nr_entries;
736         if (si->flags & SWP_BLKDEV)
737                 swap_slot_free_notify =
738                         si->bdev->bd_disk->fops->swap_slot_free_notify;
739         else
740                 swap_slot_free_notify = NULL;
741         while (offset <= end) {
742                 arch_swap_invalidate_page(si->type, offset);
743                 frontswap_invalidate_page(si->type, offset);
744                 if (swap_slot_free_notify)
745                         swap_slot_free_notify(si->bdev, offset);
746                 offset++;
747         }
748         clear_shadow_from_swap_cache(si->type, begin, end);
749 }
750
751 static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
752 {
753         unsigned long prev;
754
755         if (!(si->flags & SWP_SOLIDSTATE)) {
756                 si->cluster_next = next;
757                 return;
758         }
759
760         prev = this_cpu_read(*si->cluster_next_cpu);
761         /*
762          * Cross the swap address space size aligned trunk, choose
763          * another trunk randomly to avoid lock contention on swap
764          * address space if possible.
765          */
766         if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) !=
767             (next >> SWAP_ADDRESS_SPACE_SHIFT)) {
768                 /* No free swap slots available */
769                 if (si->highest_bit <= si->lowest_bit)
770                         return;
771                 next = si->lowest_bit +
772                         prandom_u32_max(si->highest_bit - si->lowest_bit + 1);
773                 next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
774                 next = max_t(unsigned int, next, si->lowest_bit);
775         }
776         this_cpu_write(*si->cluster_next_cpu, next);
777 }
778
779 static bool swap_offset_available_and_locked(struct swap_info_struct *si,
780                                              unsigned long offset)
781 {
782         if (data_race(!si->swap_map[offset])) {
783                 spin_lock(&si->lock);
784                 return true;
785         }
786
787         if (vm_swap_full() && READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
788                 spin_lock(&si->lock);
789                 return true;
790         }
791
792         return false;
793 }
794
795 static int scan_swap_map_slots(struct swap_info_struct *si,
796                                unsigned char usage, int nr,
797                                swp_entry_t slots[])
798 {
799         struct swap_cluster_info *ci;
800         unsigned long offset;
801         unsigned long scan_base;
802         unsigned long last_in_cluster = 0;
803         int latency_ration = LATENCY_LIMIT;
804         int n_ret = 0;
805         bool scanned_many = false;
806
807         /*
808          * We try to cluster swap pages by allocating them sequentially
809          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
810          * way, however, we resort to first-free allocation, starting
811          * a new cluster.  This prevents us from scattering swap pages
812          * all over the entire swap partition, so that we reduce
813          * overall disk seek times between swap pages.  -- sct
814          * But we do now try to find an empty cluster.  -Andrea
815          * And we let swap pages go all over an SSD partition.  Hugh
816          */
817
818         si->flags += SWP_SCANNING;
819         /*
820          * Use percpu scan base for SSD to reduce lock contention on
821          * cluster and swap cache.  For HDD, sequential access is more
822          * important.
823          */
824         if (si->flags & SWP_SOLIDSTATE)
825                 scan_base = this_cpu_read(*si->cluster_next_cpu);
826         else
827                 scan_base = si->cluster_next;
828         offset = scan_base;
829
830         /* SSD algorithm */
831         if (si->cluster_info) {
832                 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
833                         goto scan;
834         } else if (unlikely(!si->cluster_nr--)) {
835                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
836                         si->cluster_nr = SWAPFILE_CLUSTER - 1;
837                         goto checks;
838                 }
839
840                 spin_unlock(&si->lock);
841
842                 /*
843                  * If seek is expensive, start searching for new cluster from
844                  * start of partition, to minimize the span of allocated swap.
845                  * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
846                  * case, just handled by scan_swap_map_try_ssd_cluster() above.
847                  */
848                 scan_base = offset = si->lowest_bit;
849                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
850
851                 /* Locate the first empty (unaligned) cluster */
852                 for (; last_in_cluster <= si->highest_bit; offset++) {
853                         if (si->swap_map[offset])
854                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
855                         else if (offset == last_in_cluster) {
856                                 spin_lock(&si->lock);
857                                 offset -= SWAPFILE_CLUSTER - 1;
858                                 si->cluster_next = offset;
859                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
860                                 goto checks;
861                         }
862                         if (unlikely(--latency_ration < 0)) {
863                                 cond_resched();
864                                 latency_ration = LATENCY_LIMIT;
865                         }
866                 }
867
868                 offset = scan_base;
869                 spin_lock(&si->lock);
870                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
871         }
872
873 checks:
874         if (si->cluster_info) {
875                 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
876                 /* take a break if we already got some slots */
877                         if (n_ret)
878                                 goto done;
879                         if (!scan_swap_map_try_ssd_cluster(si, &offset,
880                                                         &scan_base))
881                                 goto scan;
882                 }
883         }
884         if (!(si->flags & SWP_WRITEOK))
885                 goto no_page;
886         if (!si->highest_bit)
887                 goto no_page;
888         if (offset > si->highest_bit)
889                 scan_base = offset = si->lowest_bit;
890
891         ci = lock_cluster(si, offset);
892         /* reuse swap entry of cache-only swap if not busy. */
893         if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
894                 int swap_was_freed;
895                 unlock_cluster(ci);
896                 spin_unlock(&si->lock);
897                 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
898                 spin_lock(&si->lock);
899                 /* entry was freed successfully, try to use this again */
900                 if (swap_was_freed)
901                         goto checks;
902                 goto scan; /* check next one */
903         }
904
905         if (si->swap_map[offset]) {
906                 unlock_cluster(ci);
907                 if (!n_ret)
908                         goto scan;
909                 else
910                         goto done;
911         }
912         WRITE_ONCE(si->swap_map[offset], usage);
913         inc_cluster_info_page(si, si->cluster_info, offset);
914         unlock_cluster(ci);
915
916         swap_range_alloc(si, offset, 1);
917         slots[n_ret++] = swp_entry(si->type, offset);
918
919         /* got enough slots or reach max slots? */
920         if ((n_ret == nr) || (offset >= si->highest_bit))
921                 goto done;
922
923         /* search for next available slot */
924
925         /* time to take a break? */
926         if (unlikely(--latency_ration < 0)) {
927                 if (n_ret)
928                         goto done;
929                 spin_unlock(&si->lock);
930                 cond_resched();
931                 spin_lock(&si->lock);
932                 latency_ration = LATENCY_LIMIT;
933         }
934
935         /* try to get more slots in cluster */
936         if (si->cluster_info) {
937                 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
938                         goto checks;
939         } else if (si->cluster_nr && !si->swap_map[++offset]) {
940                 /* non-ssd case, still more slots in cluster? */
941                 --si->cluster_nr;
942                 goto checks;
943         }
944
945         /*
946          * Even if there's no free clusters available (fragmented),
947          * try to scan a little more quickly with lock held unless we
948          * have scanned too many slots already.
949          */
950         if (!scanned_many) {
951                 unsigned long scan_limit;
952
953                 if (offset < scan_base)
954                         scan_limit = scan_base;
955                 else
956                         scan_limit = si->highest_bit;
957                 for (; offset <= scan_limit && --latency_ration > 0;
958                      offset++) {
959                         if (!si->swap_map[offset])
960                                 goto checks;
961                 }
962         }
963
964 done:
965         set_cluster_next(si, offset + 1);
966         si->flags -= SWP_SCANNING;
967         return n_ret;
968
969 scan:
970         spin_unlock(&si->lock);
971         while (++offset <= READ_ONCE(si->highest_bit)) {
972                 if (swap_offset_available_and_locked(si, offset))
973                         goto checks;
974                 if (unlikely(--latency_ration < 0)) {
975                         cond_resched();
976                         latency_ration = LATENCY_LIMIT;
977                         scanned_many = true;
978                 }
979         }
980         offset = si->lowest_bit;
981         while (offset < scan_base) {
982                 if (swap_offset_available_and_locked(si, offset))
983                         goto checks;
984                 if (unlikely(--latency_ration < 0)) {
985                         cond_resched();
986                         latency_ration = LATENCY_LIMIT;
987                         scanned_many = true;
988                 }
989                 offset++;
990         }
991         spin_lock(&si->lock);
992
993 no_page:
994         si->flags -= SWP_SCANNING;
995         return n_ret;
996 }
997
998 static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
999 {
1000         unsigned long idx;
1001         struct swap_cluster_info *ci;
1002         unsigned long offset;
1003
1004         /*
1005          * Should not even be attempting cluster allocations when huge
1006          * page swap is disabled.  Warn and fail the allocation.
1007          */
1008         if (!IS_ENABLED(CONFIG_THP_SWAP)) {
1009                 VM_WARN_ON_ONCE(1);
1010                 return 0;
1011         }
1012
1013         if (cluster_list_empty(&si->free_clusters))
1014                 return 0;
1015
1016         idx = cluster_list_first(&si->free_clusters);
1017         offset = idx * SWAPFILE_CLUSTER;
1018         ci = lock_cluster(si, offset);
1019         alloc_cluster(si, idx);
1020         cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
1021
1022         memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER);
1023         unlock_cluster(ci);
1024         swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
1025         *slot = swp_entry(si->type, offset);
1026
1027         return 1;
1028 }
1029
1030 static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
1031 {
1032         unsigned long offset = idx * SWAPFILE_CLUSTER;
1033         struct swap_cluster_info *ci;
1034
1035         ci = lock_cluster(si, offset);
1036         memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
1037         cluster_set_count_flag(ci, 0, 0);
1038         free_cluster(si, idx);
1039         unlock_cluster(ci);
1040         swap_range_free(si, offset, SWAPFILE_CLUSTER);
1041 }
1042
1043 int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
1044 {
1045         unsigned long size = swap_entry_size(entry_size);
1046         struct swap_info_struct *si, *next;
1047         long avail_pgs;
1048         int n_ret = 0;
1049         int node;
1050
1051         /* Only single cluster request supported */
1052         WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1053
1054         spin_lock(&swap_avail_lock);
1055
1056         avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1057         if (avail_pgs <= 0) {
1058                 spin_unlock(&swap_avail_lock);
1059                 goto noswap;
1060         }
1061
1062         n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
1063
1064         atomic_long_sub(n_goal * size, &nr_swap_pages);
1065
1066 start_over:
1067         node = numa_node_id();
1068         plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
1069                 /* requeue si to after same-priority siblings */
1070                 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
1071                 spin_unlock(&swap_avail_lock);
1072                 spin_lock(&si->lock);
1073                 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
1074                         spin_lock(&swap_avail_lock);
1075                         if (plist_node_empty(&si->avail_lists[node])) {
1076                                 spin_unlock(&si->lock);
1077                                 goto nextsi;
1078                         }
1079                         WARN(!si->highest_bit,
1080                              "swap_info %d in list but !highest_bit\n",
1081                              si->type);
1082                         WARN(!(si->flags & SWP_WRITEOK),
1083                              "swap_info %d in list but !SWP_WRITEOK\n",
1084                              si->type);
1085                         __del_from_avail_list(si);
1086                         spin_unlock(&si->lock);
1087                         goto nextsi;
1088                 }
1089                 if (size == SWAPFILE_CLUSTER) {
1090                         if (si->flags & SWP_BLKDEV)
1091                                 n_ret = swap_alloc_cluster(si, swp_entries);
1092                 } else
1093                         n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1094                                                     n_goal, swp_entries);
1095                 spin_unlock(&si->lock);
1096                 if (n_ret || size == SWAPFILE_CLUSTER)
1097                         goto check_out;
1098                 pr_debug("scan_swap_map of si %d failed to find offset\n",
1099                         si->type);
1100
1101                 spin_lock(&swap_avail_lock);
1102 nextsi:
1103                 /*
1104                  * if we got here, it's likely that si was almost full before,
1105                  * and since scan_swap_map_slots() can drop the si->lock,
1106                  * multiple callers probably all tried to get a page from the
1107                  * same si and it filled up before we could get one; or, the si
1108                  * filled up between us dropping swap_avail_lock and taking
1109                  * si->lock. Since we dropped the swap_avail_lock, the
1110                  * swap_avail_head list may have been modified; so if next is
1111                  * still in the swap_avail_head list then try it, otherwise
1112                  * start over if we have not gotten any slots.
1113                  */
1114                 if (plist_node_empty(&next->avail_lists[node]))
1115                         goto start_over;
1116         }
1117
1118         spin_unlock(&swap_avail_lock);
1119
1120 check_out:
1121         if (n_ret < n_goal)
1122                 atomic_long_add((long)(n_goal - n_ret) * size,
1123                                 &nr_swap_pages);
1124 noswap:
1125         return n_ret;
1126 }
1127
1128 static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1129 {
1130         struct swap_info_struct *p;
1131         unsigned long offset;
1132
1133         if (!entry.val)
1134                 goto out;
1135         p = swp_swap_info(entry);
1136         if (!p)
1137                 goto bad_nofile;
1138         if (data_race(!(p->flags & SWP_USED)))
1139                 goto bad_device;
1140         offset = swp_offset(entry);
1141         if (offset >= p->max)
1142                 goto bad_offset;
1143         if (data_race(!p->swap_map[swp_offset(entry)]))
1144                 goto bad_free;
1145         return p;
1146
1147 bad_free:
1148         pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val);
1149         goto out;
1150 bad_offset:
1151         pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1152         goto out;
1153 bad_device:
1154         pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
1155         goto out;
1156 bad_nofile:
1157         pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1158 out:
1159         return NULL;
1160 }
1161
1162 static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1163                                         struct swap_info_struct *q)
1164 {
1165         struct swap_info_struct *p;
1166
1167         p = _swap_info_get(entry);
1168
1169         if (p != q) {
1170                 if (q != NULL)
1171                         spin_unlock(&q->lock);
1172                 if (p != NULL)
1173                         spin_lock(&p->lock);
1174         }
1175         return p;
1176 }
1177
1178 static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1179                                               unsigned long offset,
1180                                               unsigned char usage)
1181 {
1182         unsigned char count;
1183         unsigned char has_cache;
1184
1185         count = p->swap_map[offset];
1186
1187         has_cache = count & SWAP_HAS_CACHE;
1188         count &= ~SWAP_HAS_CACHE;
1189
1190         if (usage == SWAP_HAS_CACHE) {
1191                 VM_BUG_ON(!has_cache);
1192                 has_cache = 0;
1193         } else if (count == SWAP_MAP_SHMEM) {
1194                 /*
1195                  * Or we could insist on shmem.c using a special
1196                  * swap_shmem_free() and free_shmem_swap_and_cache()...
1197                  */
1198                 count = 0;
1199         } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1200                 if (count == COUNT_CONTINUED) {
1201                         if (swap_count_continued(p, offset, count))
1202                                 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1203                         else
1204                                 count = SWAP_MAP_MAX;
1205                 } else
1206                         count--;
1207         }
1208
1209         usage = count | has_cache;
1210         if (usage)
1211                 WRITE_ONCE(p->swap_map[offset], usage);
1212         else
1213                 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
1214
1215         return usage;
1216 }
1217
1218 /*
1219  * Check whether swap entry is valid in the swap device.  If so,
1220  * return pointer to swap_info_struct, and keep the swap entry valid
1221  * via preventing the swap device from being swapoff, until
1222  * put_swap_device() is called.  Otherwise return NULL.
1223  *
1224  * Notice that swapoff or swapoff+swapon can still happen before the
1225  * percpu_ref_tryget_live() in get_swap_device() or after the
1226  * percpu_ref_put() in put_swap_device() if there isn't any other way
1227  * to prevent swapoff, such as page lock, page table lock, etc.  The
1228  * caller must be prepared for that.  For example, the following
1229  * situation is possible.
1230  *
1231  *   CPU1                               CPU2
1232  *   do_swap_page()
1233  *     ...                              swapoff+swapon
1234  *     __read_swap_cache_async()
1235  *       swapcache_prepare()
1236  *         __swap_duplicate()
1237  *           // check swap_map
1238  *     // verify PTE not changed
1239  *
1240  * In __swap_duplicate(), the swap_map need to be checked before
1241  * changing partly because the specified swap entry may be for another
1242  * swap device which has been swapoff.  And in do_swap_page(), after
1243  * the page is read from the swap device, the PTE is verified not
1244  * changed with the page table locked to check whether the swap device
1245  * has been swapoff or swapoff+swapon.
1246  */
1247 struct swap_info_struct *get_swap_device(swp_entry_t entry)
1248 {
1249         struct swap_info_struct *si;
1250         unsigned long offset;
1251
1252         if (!entry.val)
1253                 goto out;
1254         si = swp_swap_info(entry);
1255         if (!si)
1256                 goto bad_nofile;
1257         if (!percpu_ref_tryget_live(&si->users))
1258                 goto out;
1259         /*
1260          * Guarantee the si->users are checked before accessing other
1261          * fields of swap_info_struct.
1262          *
1263          * Paired with the spin_unlock() after setup_swap_info() in
1264          * enable_swap_info().
1265          */
1266         smp_rmb();
1267         offset = swp_offset(entry);
1268         if (offset >= si->max)
1269                 goto put_out;
1270
1271         return si;
1272 bad_nofile:
1273         pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1274 out:
1275         return NULL;
1276 put_out:
1277         pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1278         percpu_ref_put(&si->users);
1279         return NULL;
1280 }
1281
1282 static unsigned char __swap_entry_free(struct swap_info_struct *p,
1283                                        swp_entry_t entry)
1284 {
1285         struct swap_cluster_info *ci;
1286         unsigned long offset = swp_offset(entry);
1287         unsigned char usage;
1288
1289         ci = lock_cluster_or_swap_info(p, offset);
1290         usage = __swap_entry_free_locked(p, offset, 1);
1291         unlock_cluster_or_swap_info(p, ci);
1292         if (!usage)
1293                 free_swap_slot(entry);
1294
1295         return usage;
1296 }
1297
1298 static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1299 {
1300         struct swap_cluster_info *ci;
1301         unsigned long offset = swp_offset(entry);
1302         unsigned char count;
1303
1304         ci = lock_cluster(p, offset);
1305         count = p->swap_map[offset];
1306         VM_BUG_ON(count != SWAP_HAS_CACHE);
1307         p->swap_map[offset] = 0;
1308         dec_cluster_info_page(p, p->cluster_info, offset);
1309         unlock_cluster(ci);
1310
1311         mem_cgroup_uncharge_swap(entry, 1);
1312         swap_range_free(p, offset, 1);
1313 }
1314
1315 /*
1316  * Caller has made sure that the swap device corresponding to entry
1317  * is still around or has not been recycled.
1318  */
1319 void swap_free(swp_entry_t entry)
1320 {
1321         struct swap_info_struct *p;
1322
1323         p = _swap_info_get(entry);
1324         if (p)
1325                 __swap_entry_free(p, entry);
1326 }
1327
1328 /*
1329  * Called after dropping swapcache to decrease refcnt to swap entries.
1330  */
1331 void put_swap_page(struct page *page, swp_entry_t entry)
1332 {
1333         unsigned long offset = swp_offset(entry);
1334         unsigned long idx = offset / SWAPFILE_CLUSTER;
1335         struct swap_cluster_info *ci;
1336         struct swap_info_struct *si;
1337         unsigned char *map;
1338         unsigned int i, free_entries = 0;
1339         unsigned char val;
1340         int size = swap_entry_size(thp_nr_pages(page));
1341
1342         si = _swap_info_get(entry);
1343         if (!si)
1344                 return;
1345
1346         ci = lock_cluster_or_swap_info(si, offset);
1347         if (size == SWAPFILE_CLUSTER) {
1348                 VM_BUG_ON(!cluster_is_huge(ci));
1349                 map = si->swap_map + offset;
1350                 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1351                         val = map[i];
1352                         VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1353                         if (val == SWAP_HAS_CACHE)
1354                                 free_entries++;
1355                 }
1356                 cluster_clear_huge(ci);
1357                 if (free_entries == SWAPFILE_CLUSTER) {
1358                         unlock_cluster_or_swap_info(si, ci);
1359                         spin_lock(&si->lock);
1360                         mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1361                         swap_free_cluster(si, idx);
1362                         spin_unlock(&si->lock);
1363                         return;
1364                 }
1365         }
1366         for (i = 0; i < size; i++, entry.val++) {
1367                 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1368                         unlock_cluster_or_swap_info(si, ci);
1369                         free_swap_slot(entry);
1370                         if (i == size - 1)
1371                                 return;
1372                         lock_cluster_or_swap_info(si, offset);
1373                 }
1374         }
1375         unlock_cluster_or_swap_info(si, ci);
1376 }
1377
1378 #ifdef CONFIG_THP_SWAP
1379 int split_swap_cluster(swp_entry_t entry)
1380 {
1381         struct swap_info_struct *si;
1382         struct swap_cluster_info *ci;
1383         unsigned long offset = swp_offset(entry);
1384
1385         si = _swap_info_get(entry);
1386         if (!si)
1387                 return -EBUSY;
1388         ci = lock_cluster(si, offset);
1389         cluster_clear_huge(ci);
1390         unlock_cluster(ci);
1391         return 0;
1392 }
1393 #endif
1394
1395 static int swp_entry_cmp(const void *ent1, const void *ent2)
1396 {
1397         const swp_entry_t *e1 = ent1, *e2 = ent2;
1398
1399         return (int)swp_type(*e1) - (int)swp_type(*e2);
1400 }
1401
1402 void swapcache_free_entries(swp_entry_t *entries, int n)
1403 {
1404         struct swap_info_struct *p, *prev;
1405         int i;
1406
1407         if (n <= 0)
1408                 return;
1409
1410         prev = NULL;
1411         p = NULL;
1412
1413         /*
1414          * Sort swap entries by swap device, so each lock is only taken once.
1415          * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1416          * so low that it isn't necessary to optimize further.
1417          */
1418         if (nr_swapfiles > 1)
1419                 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1420         for (i = 0; i < n; ++i) {
1421                 p = swap_info_get_cont(entries[i], prev);
1422                 if (p)
1423                         swap_entry_free(p, entries[i]);
1424                 prev = p;
1425         }
1426         if (p)
1427                 spin_unlock(&p->lock);
1428 }
1429
1430 /*
1431  * How many references to page are currently swapped out?
1432  * This does not give an exact answer when swap count is continued,
1433  * but does include the high COUNT_CONTINUED flag to allow for that.
1434  */
1435 static int page_swapcount(struct page *page)
1436 {
1437         int count = 0;
1438         struct swap_info_struct *p;
1439         struct swap_cluster_info *ci;
1440         swp_entry_t entry;
1441         unsigned long offset;
1442
1443         entry.val = page_private(page);
1444         p = _swap_info_get(entry);
1445         if (p) {
1446                 offset = swp_offset(entry);
1447                 ci = lock_cluster_or_swap_info(p, offset);
1448                 count = swap_count(p->swap_map[offset]);
1449                 unlock_cluster_or_swap_info(p, ci);
1450         }
1451         return count;
1452 }
1453
1454 int __swap_count(swp_entry_t entry)
1455 {
1456         struct swap_info_struct *si;
1457         pgoff_t offset = swp_offset(entry);
1458         int count = 0;
1459
1460         si = get_swap_device(entry);
1461         if (si) {
1462                 count = swap_count(si->swap_map[offset]);
1463                 put_swap_device(si);
1464         }
1465         return count;
1466 }
1467
1468 static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1469 {
1470         int count = 0;
1471         pgoff_t offset = swp_offset(entry);
1472         struct swap_cluster_info *ci;
1473
1474         ci = lock_cluster_or_swap_info(si, offset);
1475         count = swap_count(si->swap_map[offset]);
1476         unlock_cluster_or_swap_info(si, ci);
1477         return count;
1478 }
1479
1480 /*
1481  * How many references to @entry are currently swapped out?
1482  * This does not give an exact answer when swap count is continued,
1483  * but does include the high COUNT_CONTINUED flag to allow for that.
1484  */
1485 int __swp_swapcount(swp_entry_t entry)
1486 {
1487         int count = 0;
1488         struct swap_info_struct *si;
1489
1490         si = get_swap_device(entry);
1491         if (si) {
1492                 count = swap_swapcount(si, entry);
1493                 put_swap_device(si);
1494         }
1495         return count;
1496 }
1497
1498 /*
1499  * How many references to @entry are currently swapped out?
1500  * This considers COUNT_CONTINUED so it returns exact answer.
1501  */
1502 int swp_swapcount(swp_entry_t entry)
1503 {
1504         int count, tmp_count, n;
1505         struct swap_info_struct *p;
1506         struct swap_cluster_info *ci;
1507         struct page *page;
1508         pgoff_t offset;
1509         unsigned char *map;
1510
1511         p = _swap_info_get(entry);
1512         if (!p)
1513                 return 0;
1514
1515         offset = swp_offset(entry);
1516
1517         ci = lock_cluster_or_swap_info(p, offset);
1518
1519         count = swap_count(p->swap_map[offset]);
1520         if (!(count & COUNT_CONTINUED))
1521                 goto out;
1522
1523         count &= ~COUNT_CONTINUED;
1524         n = SWAP_MAP_MAX + 1;
1525
1526         page = vmalloc_to_page(p->swap_map + offset);
1527         offset &= ~PAGE_MASK;
1528         VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1529
1530         do {
1531                 page = list_next_entry(page, lru);
1532                 map = kmap_atomic(page);
1533                 tmp_count = map[offset];
1534                 kunmap_atomic(map);
1535
1536                 count += (tmp_count & ~COUNT_CONTINUED) * n;
1537                 n *= (SWAP_CONT_MAX + 1);
1538         } while (tmp_count & COUNT_CONTINUED);
1539 out:
1540         unlock_cluster_or_swap_info(p, ci);
1541         return count;
1542 }
1543
1544 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1545                                          swp_entry_t entry)
1546 {
1547         struct swap_cluster_info *ci;
1548         unsigned char *map = si->swap_map;
1549         unsigned long roffset = swp_offset(entry);
1550         unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1551         int i;
1552         bool ret = false;
1553
1554         ci = lock_cluster_or_swap_info(si, offset);
1555         if (!ci || !cluster_is_huge(ci)) {
1556                 if (swap_count(map[roffset]))
1557                         ret = true;
1558                 goto unlock_out;
1559         }
1560         for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1561                 if (swap_count(map[offset + i])) {
1562                         ret = true;
1563                         break;
1564                 }
1565         }
1566 unlock_out:
1567         unlock_cluster_or_swap_info(si, ci);
1568         return ret;
1569 }
1570
1571 static bool page_swapped(struct page *page)
1572 {
1573         swp_entry_t entry;
1574         struct swap_info_struct *si;
1575
1576         if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
1577                 return page_swapcount(page) != 0;
1578
1579         page = compound_head(page);
1580         entry.val = page_private(page);
1581         si = _swap_info_get(entry);
1582         if (si)
1583                 return swap_page_trans_huge_swapped(si, entry);
1584         return false;
1585 }
1586
1587 /*
1588  * If swap is getting full, or if there are no more mappings of this page,
1589  * then try_to_free_swap is called to free its swap space.
1590  */
1591 int try_to_free_swap(struct page *page)
1592 {
1593         VM_BUG_ON_PAGE(!PageLocked(page), page);
1594
1595         if (!PageSwapCache(page))
1596                 return 0;
1597         if (PageWriteback(page))
1598                 return 0;
1599         if (page_swapped(page))
1600                 return 0;
1601
1602         /*
1603          * Once hibernation has begun to create its image of memory,
1604          * there's a danger that one of the calls to try_to_free_swap()
1605          * - most probably a call from __try_to_reclaim_swap() while
1606          * hibernation is allocating its own swap pages for the image,
1607          * but conceivably even a call from memory reclaim - will free
1608          * the swap from a page which has already been recorded in the
1609          * image as a clean swapcache page, and then reuse its swap for
1610          * another page of the image.  On waking from hibernation, the
1611          * original page might be freed under memory pressure, then
1612          * later read back in from swap, now with the wrong data.
1613          *
1614          * Hibernation suspends storage while it is writing the image
1615          * to disk so check that here.
1616          */
1617         if (pm_suspended_storage())
1618                 return 0;
1619
1620         page = compound_head(page);
1621         delete_from_swap_cache(page);
1622         SetPageDirty(page);
1623         return 1;
1624 }
1625
1626 /*
1627  * Free the swap entry like above, but also try to
1628  * free the page cache entry if it is the last user.
1629  */
1630 int free_swap_and_cache(swp_entry_t entry)
1631 {
1632         struct swap_info_struct *p;
1633         unsigned char count;
1634
1635         if (non_swap_entry(entry))
1636                 return 1;
1637
1638         p = _swap_info_get(entry);
1639         if (p) {
1640                 count = __swap_entry_free(p, entry);
1641                 if (count == SWAP_HAS_CACHE &&
1642                     !swap_page_trans_huge_swapped(p, entry))
1643                         __try_to_reclaim_swap(p, swp_offset(entry),
1644                                               TTRS_UNMAPPED | TTRS_FULL);
1645         }
1646         return p != NULL;
1647 }
1648
1649 #ifdef CONFIG_HIBERNATION
1650
1651 swp_entry_t get_swap_page_of_type(int type)
1652 {
1653         struct swap_info_struct *si = swap_type_to_swap_info(type);
1654         swp_entry_t entry = {0};
1655
1656         if (!si)
1657                 goto fail;
1658
1659         /* This is called for allocating swap entry, not cache */
1660         spin_lock(&si->lock);
1661         if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
1662                 atomic_long_dec(&nr_swap_pages);
1663         spin_unlock(&si->lock);
1664 fail:
1665         return entry;
1666 }
1667
1668 /*
1669  * Find the swap type that corresponds to given device (if any).
1670  *
1671  * @offset - number of the PAGE_SIZE-sized block of the device, starting
1672  * from 0, in which the swap header is expected to be located.
1673  *
1674  * This is needed for the suspend to disk (aka swsusp).
1675  */
1676 int swap_type_of(dev_t device, sector_t offset)
1677 {
1678         int type;
1679
1680         if (!device)
1681                 return -1;
1682
1683         spin_lock(&swap_lock);
1684         for (type = 0; type < nr_swapfiles; type++) {
1685                 struct swap_info_struct *sis = swap_info[type];
1686
1687                 if (!(sis->flags & SWP_WRITEOK))
1688                         continue;
1689
1690                 if (device == sis->bdev->bd_dev) {
1691                         struct swap_extent *se = first_se(sis);
1692
1693                         if (se->start_block == offset) {
1694                                 spin_unlock(&swap_lock);
1695                                 return type;
1696                         }
1697                 }
1698         }
1699         spin_unlock(&swap_lock);
1700         return -ENODEV;
1701 }
1702
1703 int find_first_swap(dev_t *device)
1704 {
1705         int type;
1706
1707         spin_lock(&swap_lock);
1708         for (type = 0; type < nr_swapfiles; type++) {
1709                 struct swap_info_struct *sis = swap_info[type];
1710
1711                 if (!(sis->flags & SWP_WRITEOK))
1712                         continue;
1713                 *device = sis->bdev->bd_dev;
1714                 spin_unlock(&swap_lock);
1715                 return type;
1716         }
1717         spin_unlock(&swap_lock);
1718         return -ENODEV;
1719 }
1720
1721 /*
1722  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1723  * corresponding to given index in swap_info (swap type).
1724  */
1725 sector_t swapdev_block(int type, pgoff_t offset)
1726 {
1727         struct swap_info_struct *si = swap_type_to_swap_info(type);
1728         struct swap_extent *se;
1729
1730         if (!si || !(si->flags & SWP_WRITEOK))
1731                 return 0;
1732         se = offset_to_swap_extent(si, offset);
1733         return se->start_block + (offset - se->start_page);
1734 }
1735
1736 /*
1737  * Return either the total number of swap pages of given type, or the number
1738  * of free pages of that type (depending on @free)
1739  *
1740  * This is needed for software suspend
1741  */
1742 unsigned int count_swap_pages(int type, int free)
1743 {
1744         unsigned int n = 0;
1745
1746         spin_lock(&swap_lock);
1747         if ((unsigned int)type < nr_swapfiles) {
1748                 struct swap_info_struct *sis = swap_info[type];
1749
1750                 spin_lock(&sis->lock);
1751                 if (sis->flags & SWP_WRITEOK) {
1752                         n = sis->pages;
1753                         if (free)
1754                                 n -= sis->inuse_pages;
1755                 }
1756                 spin_unlock(&sis->lock);
1757         }
1758         spin_unlock(&swap_lock);
1759         return n;
1760 }
1761 #endif /* CONFIG_HIBERNATION */
1762
1763 static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1764 {
1765         return pte_same(pte_swp_clear_flags(pte), swp_pte);
1766 }
1767
1768 /*
1769  * No need to decide whether this PTE shares the swap entry with others,
1770  * just let do_wp_page work it out if a write is requested later - to
1771  * force COW, vm_page_prot omits write permission from any private vma.
1772  */
1773 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1774                 unsigned long addr, swp_entry_t entry, struct page *page)
1775 {
1776         struct page *swapcache;
1777         spinlock_t *ptl;
1778         pte_t *pte, new_pte;
1779         int ret = 1;
1780
1781         swapcache = page;
1782         page = ksm_might_need_to_copy(page, vma, addr);
1783         if (unlikely(!page))
1784                 return -ENOMEM;
1785
1786         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1787         if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1788                 ret = 0;
1789                 goto out;
1790         }
1791
1792         if (unlikely(!PageUptodate(page))) {
1793                 pte_t pteval;
1794
1795                 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1796                 pteval = swp_entry_to_pte(make_swapin_error_entry(page));
1797                 set_pte_at(vma->vm_mm, addr, pte, pteval);
1798                 swap_free(entry);
1799                 ret = 0;
1800                 goto out;
1801         }
1802
1803         /* See do_swap_page() */
1804         BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
1805         BUG_ON(PageAnon(page) && PageAnonExclusive(page));
1806
1807         dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1808         inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1809         get_page(page);
1810         if (page == swapcache) {
1811                 rmap_t rmap_flags = RMAP_NONE;
1812
1813                 /*
1814                  * See do_swap_page(): PageWriteback() would be problematic.
1815                  * However, we do a wait_on_page_writeback() just before this
1816                  * call and have the page locked.
1817                  */
1818                 VM_BUG_ON_PAGE(PageWriteback(page), page);
1819                 if (pte_swp_exclusive(*pte))
1820                         rmap_flags |= RMAP_EXCLUSIVE;
1821
1822                 page_add_anon_rmap(page, vma, addr, rmap_flags);
1823         } else { /* ksm created a completely new copy */
1824                 page_add_new_anon_rmap(page, vma, addr);
1825                 lru_cache_add_inactive_or_unevictable(page, vma);
1826         }
1827         new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot));
1828         if (pte_swp_soft_dirty(*pte))
1829                 new_pte = pte_mksoft_dirty(new_pte);
1830         if (pte_swp_uffd_wp(*pte))
1831                 new_pte = pte_mkuffd_wp(new_pte);
1832         set_pte_at(vma->vm_mm, addr, pte, new_pte);
1833         swap_free(entry);
1834 out:
1835         pte_unmap_unlock(pte, ptl);
1836         if (page != swapcache) {
1837                 unlock_page(page);
1838                 put_page(page);
1839         }
1840         return ret;
1841 }
1842
1843 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1844                         unsigned long addr, unsigned long end,
1845                         unsigned int type)
1846 {
1847         struct page *page;
1848         swp_entry_t entry;
1849         pte_t *pte;
1850         struct swap_info_struct *si;
1851         unsigned long offset;
1852         int ret = 0;
1853         volatile unsigned char *swap_map;
1854
1855         si = swap_info[type];
1856         pte = pte_offset_map(pmd, addr);
1857         do {
1858                 if (!is_swap_pte(*pte))
1859                         continue;
1860
1861                 entry = pte_to_swp_entry(*pte);
1862                 if (swp_type(entry) != type)
1863                         continue;
1864
1865                 offset = swp_offset(entry);
1866                 pte_unmap(pte);
1867                 swap_map = &si->swap_map[offset];
1868                 page = lookup_swap_cache(entry, vma, addr);
1869                 if (!page) {
1870                         struct vm_fault vmf = {
1871                                 .vma = vma,
1872                                 .address = addr,
1873                                 .real_address = addr,
1874                                 .pmd = pmd,
1875                         };
1876
1877                         page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
1878                                                 &vmf);
1879                 }
1880                 if (!page) {
1881                         if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1882                                 goto try_next;
1883                         return -ENOMEM;
1884                 }
1885
1886                 lock_page(page);
1887                 wait_on_page_writeback(page);
1888                 ret = unuse_pte(vma, pmd, addr, entry, page);
1889                 if (ret < 0) {
1890                         unlock_page(page);
1891                         put_page(page);
1892                         goto out;
1893                 }
1894
1895                 try_to_free_swap(page);
1896                 unlock_page(page);
1897                 put_page(page);
1898 try_next:
1899                 pte = pte_offset_map(pmd, addr);
1900         } while (pte++, addr += PAGE_SIZE, addr != end);
1901         pte_unmap(pte - 1);
1902
1903         ret = 0;
1904 out:
1905         return ret;
1906 }
1907
1908 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1909                                 unsigned long addr, unsigned long end,
1910                                 unsigned int type)
1911 {
1912         pmd_t *pmd;
1913         unsigned long next;
1914         int ret;
1915
1916         pmd = pmd_offset(pud, addr);
1917         do {
1918                 cond_resched();
1919                 next = pmd_addr_end(addr, end);
1920                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1921                         continue;
1922                 ret = unuse_pte_range(vma, pmd, addr, next, type);
1923                 if (ret)
1924                         return ret;
1925         } while (pmd++, addr = next, addr != end);
1926         return 0;
1927 }
1928
1929 static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
1930                                 unsigned long addr, unsigned long end,
1931                                 unsigned int type)
1932 {
1933         pud_t *pud;
1934         unsigned long next;
1935         int ret;
1936
1937         pud = pud_offset(p4d, addr);
1938         do {
1939                 next = pud_addr_end(addr, end);
1940                 if (pud_none_or_clear_bad(pud))
1941                         continue;
1942                 ret = unuse_pmd_range(vma, pud, addr, next, type);
1943                 if (ret)
1944                         return ret;
1945         } while (pud++, addr = next, addr != end);
1946         return 0;
1947 }
1948
1949 static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
1950                                 unsigned long addr, unsigned long end,
1951                                 unsigned int type)
1952 {
1953         p4d_t *p4d;
1954         unsigned long next;
1955         int ret;
1956
1957         p4d = p4d_offset(pgd, addr);
1958         do {
1959                 next = p4d_addr_end(addr, end);
1960                 if (p4d_none_or_clear_bad(p4d))
1961                         continue;
1962                 ret = unuse_pud_range(vma, p4d, addr, next, type);
1963                 if (ret)
1964                         return ret;
1965         } while (p4d++, addr = next, addr != end);
1966         return 0;
1967 }
1968
1969 static int unuse_vma(struct vm_area_struct *vma, unsigned int type)
1970 {
1971         pgd_t *pgd;
1972         unsigned long addr, end, next;
1973         int ret;
1974
1975         addr = vma->vm_start;
1976         end = vma->vm_end;
1977
1978         pgd = pgd_offset(vma->vm_mm, addr);
1979         do {
1980                 next = pgd_addr_end(addr, end);
1981                 if (pgd_none_or_clear_bad(pgd))
1982                         continue;
1983                 ret = unuse_p4d_range(vma, pgd, addr, next, type);
1984                 if (ret)
1985                         return ret;
1986         } while (pgd++, addr = next, addr != end);
1987         return 0;
1988 }
1989
1990 static int unuse_mm(struct mm_struct *mm, unsigned int type)
1991 {
1992         struct vm_area_struct *vma;
1993         int ret = 0;
1994
1995         mmap_read_lock(mm);
1996         for (vma = mm->mmap; vma; vma = vma->vm_next) {
1997                 if (vma->anon_vma) {
1998                         ret = unuse_vma(vma, type);
1999                         if (ret)
2000                                 break;
2001                 }
2002                 cond_resched();
2003         }
2004         mmap_read_unlock(mm);
2005         return ret;
2006 }
2007
2008 /*
2009  * Scan swap_map from current position to next entry still in use.
2010  * Return 0 if there are no inuse entries after prev till end of
2011  * the map.
2012  */
2013 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
2014                                         unsigned int prev)
2015 {
2016         unsigned int i;
2017         unsigned char count;
2018
2019         /*
2020          * No need for swap_lock here: we're just looking
2021          * for whether an entry is in use, not modifying it; false
2022          * hits are okay, and sys_swapoff() has already prevented new
2023          * allocations from this area (while holding swap_lock).
2024          */
2025         for (i = prev + 1; i < si->max; i++) {
2026                 count = READ_ONCE(si->swap_map[i]);
2027                 if (count && swap_count(count) != SWAP_MAP_BAD)
2028                         break;
2029                 if ((i % LATENCY_LIMIT) == 0)
2030                         cond_resched();
2031         }
2032
2033         if (i == si->max)
2034                 i = 0;
2035
2036         return i;
2037 }
2038
2039 static int try_to_unuse(unsigned int type)
2040 {
2041         struct mm_struct *prev_mm;
2042         struct mm_struct *mm;
2043         struct list_head *p;
2044         int retval = 0;
2045         struct swap_info_struct *si = swap_info[type];
2046         struct page *page;
2047         swp_entry_t entry;
2048         unsigned int i;
2049
2050         if (!READ_ONCE(si->inuse_pages))
2051                 return 0;
2052
2053 retry:
2054         retval = shmem_unuse(type);
2055         if (retval)
2056                 return retval;
2057
2058         prev_mm = &init_mm;
2059         mmget(prev_mm);
2060
2061         spin_lock(&mmlist_lock);
2062         p = &init_mm.mmlist;
2063         while (READ_ONCE(si->inuse_pages) &&
2064                !signal_pending(current) &&
2065                (p = p->next) != &init_mm.mmlist) {
2066
2067                 mm = list_entry(p, struct mm_struct, mmlist);
2068                 if (!mmget_not_zero(mm))
2069                         continue;
2070                 spin_unlock(&mmlist_lock);
2071                 mmput(prev_mm);
2072                 prev_mm = mm;
2073                 retval = unuse_mm(mm, type);
2074                 if (retval) {
2075                         mmput(prev_mm);
2076                         return retval;
2077                 }
2078
2079                 /*
2080                  * Make sure that we aren't completely killing
2081                  * interactive performance.
2082                  */
2083                 cond_resched();
2084                 spin_lock(&mmlist_lock);
2085         }
2086         spin_unlock(&mmlist_lock);
2087
2088         mmput(prev_mm);
2089
2090         i = 0;
2091         while (READ_ONCE(si->inuse_pages) &&
2092                !signal_pending(current) &&
2093                (i = find_next_to_unuse(si, i)) != 0) {
2094
2095                 entry = swp_entry(type, i);
2096                 page = find_get_page(swap_address_space(entry), i);
2097                 if (!page)
2098                         continue;
2099
2100                 /*
2101                  * It is conceivable that a racing task removed this page from
2102                  * swap cache just before we acquired the page lock. The page
2103                  * might even be back in swap cache on another swap area. But
2104                  * that is okay, try_to_free_swap() only removes stale pages.
2105                  */
2106                 lock_page(page);
2107                 wait_on_page_writeback(page);
2108                 try_to_free_swap(page);
2109                 unlock_page(page);
2110                 put_page(page);
2111         }
2112
2113         /*
2114          * Lets check again to see if there are still swap entries in the map.
2115          * If yes, we would need to do retry the unuse logic again.
2116          * Under global memory pressure, swap entries can be reinserted back
2117          * into process space after the mmlist loop above passes over them.
2118          *
2119          * Limit the number of retries? No: when mmget_not_zero()
2120          * above fails, that mm is likely to be freeing swap from
2121          * exit_mmap(), which proceeds at its own independent pace;
2122          * and even shmem_writepage() could have been preempted after
2123          * folio_alloc_swap(), temporarily hiding that swap.  It's easy
2124          * and robust (though cpu-intensive) just to keep retrying.
2125          */
2126         if (READ_ONCE(si->inuse_pages)) {
2127                 if (!signal_pending(current))
2128                         goto retry;
2129                 return -EINTR;
2130         }
2131
2132         return 0;
2133 }
2134
2135 /*
2136  * After a successful try_to_unuse, if no swap is now in use, we know
2137  * we can empty the mmlist.  swap_lock must be held on entry and exit.
2138  * Note that mmlist_lock nests inside swap_lock, and an mm must be
2139  * added to the mmlist just after page_duplicate - before would be racy.
2140  */
2141 static void drain_mmlist(void)
2142 {
2143         struct list_head *p, *next;
2144         unsigned int type;
2145
2146         for (type = 0; type < nr_swapfiles; type++)
2147                 if (swap_info[type]->inuse_pages)
2148                         return;
2149         spin_lock(&mmlist_lock);
2150         list_for_each_safe(p, next, &init_mm.mmlist)
2151                 list_del_init(p);
2152         spin_unlock(&mmlist_lock);
2153 }
2154
2155 /*
2156  * Free all of a swapdev's extent information
2157  */
2158 static void destroy_swap_extents(struct swap_info_struct *sis)
2159 {
2160         while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2161                 struct rb_node *rb = sis->swap_extent_root.rb_node;
2162                 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2163
2164                 rb_erase(rb, &sis->swap_extent_root);
2165                 kfree(se);
2166         }
2167
2168         if (sis->flags & SWP_ACTIVATED) {
2169                 struct file *swap_file = sis->swap_file;
2170                 struct address_space *mapping = swap_file->f_mapping;
2171
2172                 sis->flags &= ~SWP_ACTIVATED;
2173                 if (mapping->a_ops->swap_deactivate)
2174                         mapping->a_ops->swap_deactivate(swap_file);
2175         }
2176 }
2177
2178 /*
2179  * Add a block range (and the corresponding page range) into this swapdev's
2180  * extent tree.
2181  *
2182  * This function rather assumes that it is called in ascending page order.
2183  */
2184 int
2185 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2186                 unsigned long nr_pages, sector_t start_block)
2187 {
2188         struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2189         struct swap_extent *se;
2190         struct swap_extent *new_se;
2191
2192         /*
2193          * place the new node at the right most since the
2194          * function is called in ascending page order.
2195          */
2196         while (*link) {
2197                 parent = *link;
2198                 link = &parent->rb_right;
2199         }
2200
2201         if (parent) {
2202                 se = rb_entry(parent, struct swap_extent, rb_node);
2203                 BUG_ON(se->start_page + se->nr_pages != start_page);
2204                 if (se->start_block + se->nr_pages == start_block) {
2205                         /* Merge it */
2206                         se->nr_pages += nr_pages;
2207                         return 0;
2208                 }
2209         }
2210
2211         /* No merge, insert a new extent. */
2212         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2213         if (new_se == NULL)
2214                 return -ENOMEM;
2215         new_se->start_page = start_page;
2216         new_se->nr_pages = nr_pages;
2217         new_se->start_block = start_block;
2218
2219         rb_link_node(&new_se->rb_node, parent, link);
2220         rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2221         return 1;
2222 }
2223 EXPORT_SYMBOL_GPL(add_swap_extent);
2224
2225 /*
2226  * A `swap extent' is a simple thing which maps a contiguous range of pages
2227  * onto a contiguous range of disk blocks.  A rbtree of swap extents is
2228  * built at swapon time and is then used at swap_writepage/swap_readpage
2229  * time for locating where on disk a page belongs.
2230  *
2231  * If the swapfile is an S_ISBLK block device, a single extent is installed.
2232  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2233  * swap files identically.
2234  *
2235  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2236  * extent rbtree operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
2237  * swapfiles are handled *identically* after swapon time.
2238  *
2239  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2240  * and will parse them into a rbtree, in PAGE_SIZE chunks.  If some stray
2241  * blocks are found which do not fall within the PAGE_SIZE alignment
2242  * requirements, they are simply tossed out - we will never use those blocks
2243  * for swapping.
2244  *
2245  * For all swap devices we set S_SWAPFILE across the life of the swapon.  This
2246  * prevents users from writing to the swap device, which will corrupt memory.
2247  *
2248  * The amount of disk space which a single swap extent represents varies.
2249  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
2250  * extents in the rbtree. - akpm.
2251  */
2252 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2253 {
2254         struct file *swap_file = sis->swap_file;
2255         struct address_space *mapping = swap_file->f_mapping;
2256         struct inode *inode = mapping->host;
2257         int ret;
2258
2259         if (S_ISBLK(inode->i_mode)) {
2260                 ret = add_swap_extent(sis, 0, sis->max, 0);
2261                 *span = sis->pages;
2262                 return ret;
2263         }
2264
2265         if (mapping->a_ops->swap_activate) {
2266                 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2267                 if (ret < 0)
2268                         return ret;
2269                 sis->flags |= SWP_ACTIVATED;
2270                 if ((sis->flags & SWP_FS_OPS) &&
2271                     sio_pool_init() != 0) {
2272                         destroy_swap_extents(sis);
2273                         return -ENOMEM;
2274                 }
2275                 return ret;
2276         }
2277
2278         return generic_swapfile_activate(sis, swap_file, span);
2279 }
2280
2281 static int swap_node(struct swap_info_struct *p)
2282 {
2283         struct block_device *bdev;
2284
2285         if (p->bdev)
2286                 bdev = p->bdev;
2287         else
2288                 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2289
2290         return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2291 }
2292
2293 static void setup_swap_info(struct swap_info_struct *p, int prio,
2294                             unsigned char *swap_map,
2295                             struct swap_cluster_info *cluster_info)
2296 {
2297         int i;
2298
2299         if (prio >= 0)
2300                 p->prio = prio;
2301         else
2302                 p->prio = --least_priority;
2303         /*
2304          * the plist prio is negated because plist ordering is
2305          * low-to-high, while swap ordering is high-to-low
2306          */
2307         p->list.prio = -p->prio;
2308         for_each_node(i) {
2309                 if (p->prio >= 0)
2310                         p->avail_lists[i].prio = -p->prio;
2311                 else {
2312                         if (swap_node(p) == i)
2313                                 p->avail_lists[i].prio = 1;
2314                         else
2315                                 p->avail_lists[i].prio = -p->prio;
2316                 }
2317         }
2318         p->swap_map = swap_map;
2319         p->cluster_info = cluster_info;
2320 }
2321
2322 static void _enable_swap_info(struct swap_info_struct *p)
2323 {
2324         p->flags |= SWP_WRITEOK;
2325         atomic_long_add(p->pages, &nr_swap_pages);
2326         total_swap_pages += p->pages;
2327
2328         assert_spin_locked(&swap_lock);
2329         /*
2330          * both lists are plists, and thus priority ordered.
2331          * swap_active_head needs to be priority ordered for swapoff(),
2332          * which on removal of any swap_info_struct with an auto-assigned
2333          * (i.e. negative) priority increments the auto-assigned priority
2334          * of any lower-priority swap_info_structs.
2335          * swap_avail_head needs to be priority ordered for folio_alloc_swap(),
2336          * which allocates swap pages from the highest available priority
2337          * swap_info_struct.
2338          */
2339         plist_add(&p->list, &swap_active_head);
2340         add_to_avail_list(p);
2341 }
2342
2343 static void enable_swap_info(struct swap_info_struct *p, int prio,
2344                                 unsigned char *swap_map,
2345                                 struct swap_cluster_info *cluster_info,
2346                                 unsigned long *frontswap_map)
2347 {
2348         if (IS_ENABLED(CONFIG_FRONTSWAP))
2349                 frontswap_init(p->type, frontswap_map);
2350         spin_lock(&swap_lock);
2351         spin_lock(&p->lock);
2352         setup_swap_info(p, prio, swap_map, cluster_info);
2353         spin_unlock(&p->lock);
2354         spin_unlock(&swap_lock);
2355         /*
2356          * Finished initializing swap device, now it's safe to reference it.
2357          */
2358         percpu_ref_resurrect(&p->users);
2359         spin_lock(&swap_lock);
2360         spin_lock(&p->lock);
2361         _enable_swap_info(p);
2362         spin_unlock(&p->lock);
2363         spin_unlock(&swap_lock);
2364 }
2365
2366 static void reinsert_swap_info(struct swap_info_struct *p)
2367 {
2368         spin_lock(&swap_lock);
2369         spin_lock(&p->lock);
2370         setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2371         _enable_swap_info(p);
2372         spin_unlock(&p->lock);
2373         spin_unlock(&swap_lock);
2374 }
2375
2376 bool has_usable_swap(void)
2377 {
2378         bool ret = true;
2379
2380         spin_lock(&swap_lock);
2381         if (plist_head_empty(&swap_active_head))
2382                 ret = false;
2383         spin_unlock(&swap_lock);
2384         return ret;
2385 }
2386
2387 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2388 {
2389         struct swap_info_struct *p = NULL;
2390         unsigned char *swap_map;
2391         struct swap_cluster_info *cluster_info;
2392         unsigned long *frontswap_map;
2393         struct file *swap_file, *victim;
2394         struct address_space *mapping;
2395         struct inode *inode;
2396         struct filename *pathname;
2397         int err, found = 0;
2398         unsigned int old_block_size;
2399
2400         if (!capable(CAP_SYS_ADMIN))
2401                 return -EPERM;
2402
2403         BUG_ON(!current->mm);
2404
2405         pathname = getname(specialfile);
2406         if (IS_ERR(pathname))
2407                 return PTR_ERR(pathname);
2408
2409         victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2410         err = PTR_ERR(victim);
2411         if (IS_ERR(victim))
2412                 goto out;
2413
2414         mapping = victim->f_mapping;
2415         spin_lock(&swap_lock);
2416         plist_for_each_entry(p, &swap_active_head, list) {
2417                 if (p->flags & SWP_WRITEOK) {
2418                         if (p->swap_file->f_mapping == mapping) {
2419                                 found = 1;
2420                                 break;
2421                         }
2422                 }
2423         }
2424         if (!found) {
2425                 err = -EINVAL;
2426                 spin_unlock(&swap_lock);
2427                 goto out_dput;
2428         }
2429         if (!security_vm_enough_memory_mm(current->mm, p->pages))
2430                 vm_unacct_memory(p->pages);
2431         else {
2432                 err = -ENOMEM;
2433                 spin_unlock(&swap_lock);
2434                 goto out_dput;
2435         }
2436         del_from_avail_list(p);
2437         spin_lock(&p->lock);
2438         if (p->prio < 0) {
2439                 struct swap_info_struct *si = p;
2440                 int nid;
2441
2442                 plist_for_each_entry_continue(si, &swap_active_head, list) {
2443                         si->prio++;
2444                         si->list.prio--;
2445                         for_each_node(nid) {
2446                                 if (si->avail_lists[nid].prio != 1)
2447                                         si->avail_lists[nid].prio--;
2448                         }
2449                 }
2450                 least_priority++;
2451         }
2452         plist_del(&p->list, &swap_active_head);
2453         atomic_long_sub(p->pages, &nr_swap_pages);
2454         total_swap_pages -= p->pages;
2455         p->flags &= ~SWP_WRITEOK;
2456         spin_unlock(&p->lock);
2457         spin_unlock(&swap_lock);
2458
2459         disable_swap_slots_cache_lock();
2460
2461         set_current_oom_origin();
2462         err = try_to_unuse(p->type);
2463         clear_current_oom_origin();
2464
2465         if (err) {
2466                 /* re-insert swap space back into swap_list */
2467                 reinsert_swap_info(p);
2468                 reenable_swap_slots_cache_unlock();
2469                 goto out_dput;
2470         }
2471
2472         reenable_swap_slots_cache_unlock();
2473
2474         /*
2475          * Wait for swap operations protected by get/put_swap_device()
2476          * to complete.
2477          *
2478          * We need synchronize_rcu() here to protect the accessing to
2479          * the swap cache data structure.
2480          */
2481         percpu_ref_kill(&p->users);
2482         synchronize_rcu();
2483         wait_for_completion(&p->comp);
2484
2485         flush_work(&p->discard_work);
2486
2487         destroy_swap_extents(p);
2488         if (p->flags & SWP_CONTINUED)
2489                 free_swap_count_continuations(p);
2490
2491         if (!p->bdev || !bdev_nonrot(p->bdev))
2492                 atomic_dec(&nr_rotate_swap);
2493
2494         mutex_lock(&swapon_mutex);
2495         spin_lock(&swap_lock);
2496         spin_lock(&p->lock);
2497         drain_mmlist();
2498
2499         /* wait for anyone still in scan_swap_map_slots */
2500         p->highest_bit = 0;             /* cuts scans short */
2501         while (p->flags >= SWP_SCANNING) {
2502                 spin_unlock(&p->lock);
2503                 spin_unlock(&swap_lock);
2504                 schedule_timeout_uninterruptible(1);
2505                 spin_lock(&swap_lock);
2506                 spin_lock(&p->lock);
2507         }
2508
2509         swap_file = p->swap_file;
2510         old_block_size = p->old_block_size;
2511         p->swap_file = NULL;
2512         p->max = 0;
2513         swap_map = p->swap_map;
2514         p->swap_map = NULL;
2515         cluster_info = p->cluster_info;
2516         p->cluster_info = NULL;
2517         frontswap_map = frontswap_map_get(p);
2518         spin_unlock(&p->lock);
2519         spin_unlock(&swap_lock);
2520         arch_swap_invalidate_area(p->type);
2521         frontswap_invalidate_area(p->type);
2522         frontswap_map_set(p, NULL);
2523         mutex_unlock(&swapon_mutex);
2524         free_percpu(p->percpu_cluster);
2525         p->percpu_cluster = NULL;
2526         free_percpu(p->cluster_next_cpu);
2527         p->cluster_next_cpu = NULL;
2528         vfree(swap_map);
2529         kvfree(cluster_info);
2530         kvfree(frontswap_map);
2531         /* Destroy swap account information */
2532         swap_cgroup_swapoff(p->type);
2533         exit_swap_address_space(p->type);
2534
2535         inode = mapping->host;
2536         if (S_ISBLK(inode->i_mode)) {
2537                 struct block_device *bdev = I_BDEV(inode);
2538
2539                 set_blocksize(bdev, old_block_size);
2540                 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2541         }
2542
2543         inode_lock(inode);
2544         inode->i_flags &= ~S_SWAPFILE;
2545         inode_unlock(inode);
2546         filp_close(swap_file, NULL);
2547
2548         /*
2549          * Clear the SWP_USED flag after all resources are freed so that swapon
2550          * can reuse this swap_info in alloc_swap_info() safely.  It is ok to
2551          * not hold p->lock after we cleared its SWP_WRITEOK.
2552          */
2553         spin_lock(&swap_lock);
2554         p->flags = 0;
2555         spin_unlock(&swap_lock);
2556
2557         err = 0;
2558         atomic_inc(&proc_poll_event);
2559         wake_up_interruptible(&proc_poll_wait);
2560
2561 out_dput:
2562         filp_close(victim, NULL);
2563 out:
2564         putname(pathname);
2565         return err;
2566 }
2567
2568 #ifdef CONFIG_PROC_FS
2569 static __poll_t swaps_poll(struct file *file, poll_table *wait)
2570 {
2571         struct seq_file *seq = file->private_data;
2572
2573         poll_wait(file, &proc_poll_wait, wait);
2574
2575         if (seq->poll_event != atomic_read(&proc_poll_event)) {
2576                 seq->poll_event = atomic_read(&proc_poll_event);
2577                 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2578         }
2579
2580         return EPOLLIN | EPOLLRDNORM;
2581 }
2582
2583 /* iterator */
2584 static void *swap_start(struct seq_file *swap, loff_t *pos)
2585 {
2586         struct swap_info_struct *si;
2587         int type;
2588         loff_t l = *pos;
2589
2590         mutex_lock(&swapon_mutex);
2591
2592         if (!l)
2593                 return SEQ_START_TOKEN;
2594
2595         for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2596                 if (!(si->flags & SWP_USED) || !si->swap_map)
2597                         continue;
2598                 if (!--l)
2599                         return si;
2600         }
2601
2602         return NULL;
2603 }
2604
2605 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2606 {
2607         struct swap_info_struct *si = v;
2608         int type;
2609
2610         if (v == SEQ_START_TOKEN)
2611                 type = 0;
2612         else
2613                 type = si->type + 1;
2614
2615         ++(*pos);
2616         for (; (si = swap_type_to_swap_info(type)); type++) {
2617                 if (!(si->flags & SWP_USED) || !si->swap_map)
2618                         continue;
2619                 return si;
2620         }
2621
2622         return NULL;
2623 }
2624
2625 static void swap_stop(struct seq_file *swap, void *v)
2626 {
2627         mutex_unlock(&swapon_mutex);
2628 }
2629
2630 static int swap_show(struct seq_file *swap, void *v)
2631 {
2632         struct swap_info_struct *si = v;
2633         struct file *file;
2634         int len;
2635         unsigned long bytes, inuse;
2636
2637         if (si == SEQ_START_TOKEN) {
2638                 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2639                 return 0;
2640         }
2641
2642         bytes = si->pages << (PAGE_SHIFT - 10);
2643         inuse = si->inuse_pages << (PAGE_SHIFT - 10);
2644
2645         file = si->swap_file;
2646         len = seq_file_path(swap, file, " \t\n\\");
2647         seq_printf(swap, "%*s%s\t%lu\t%s%lu\t%s%d\n",
2648                         len < 40 ? 40 - len : 1, " ",
2649                         S_ISBLK(file_inode(file)->i_mode) ?
2650                                 "partition" : "file\t",
2651                         bytes, bytes < 10000000 ? "\t" : "",
2652                         inuse, inuse < 10000000 ? "\t" : "",
2653                         si->prio);
2654         return 0;
2655 }
2656
2657 static const struct seq_operations swaps_op = {
2658         .start =        swap_start,
2659         .next =         swap_next,
2660         .stop =         swap_stop,
2661         .show =         swap_show
2662 };
2663
2664 static int swaps_open(struct inode *inode, struct file *file)
2665 {
2666         struct seq_file *seq;
2667         int ret;
2668
2669         ret = seq_open(file, &swaps_op);
2670         if (ret)
2671                 return ret;
2672
2673         seq = file->private_data;
2674         seq->poll_event = atomic_read(&proc_poll_event);
2675         return 0;
2676 }
2677
2678 static const struct proc_ops swaps_proc_ops = {
2679         .proc_flags     = PROC_ENTRY_PERMANENT,
2680         .proc_open      = swaps_open,
2681         .proc_read      = seq_read,
2682         .proc_lseek     = seq_lseek,
2683         .proc_release   = seq_release,
2684         .proc_poll      = swaps_poll,
2685 };
2686
2687 static int __init procswaps_init(void)
2688 {
2689         proc_create("swaps", 0, NULL, &swaps_proc_ops);
2690         return 0;
2691 }
2692 __initcall(procswaps_init);
2693 #endif /* CONFIG_PROC_FS */
2694
2695 #ifdef MAX_SWAPFILES_CHECK
2696 static int __init max_swapfiles_check(void)
2697 {
2698         MAX_SWAPFILES_CHECK();
2699         return 0;
2700 }
2701 late_initcall(max_swapfiles_check);
2702 #endif
2703
2704 static struct swap_info_struct *alloc_swap_info(void)
2705 {
2706         struct swap_info_struct *p;
2707         struct swap_info_struct *defer = NULL;
2708         unsigned int type;
2709         int i;
2710
2711         p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2712         if (!p)
2713                 return ERR_PTR(-ENOMEM);
2714
2715         if (percpu_ref_init(&p->users, swap_users_ref_free,
2716                             PERCPU_REF_INIT_DEAD, GFP_KERNEL)) {
2717                 kvfree(p);
2718                 return ERR_PTR(-ENOMEM);
2719         }
2720
2721         spin_lock(&swap_lock);
2722         for (type = 0; type < nr_swapfiles; type++) {
2723                 if (!(swap_info[type]->flags & SWP_USED))
2724                         break;
2725         }
2726         if (type >= MAX_SWAPFILES) {
2727                 spin_unlock(&swap_lock);
2728                 percpu_ref_exit(&p->users);
2729                 kvfree(p);
2730                 return ERR_PTR(-EPERM);
2731         }
2732         if (type >= nr_swapfiles) {
2733                 p->type = type;
2734                 /*
2735                  * Publish the swap_info_struct after initializing it.
2736                  * Note that kvzalloc() above zeroes all its fields.
2737                  */
2738                 smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */
2739                 nr_swapfiles++;
2740         } else {
2741                 defer = p;
2742                 p = swap_info[type];
2743                 /*
2744                  * Do not memset this entry: a racing procfs swap_next()
2745                  * would be relying on p->type to remain valid.
2746                  */
2747         }
2748         p->swap_extent_root = RB_ROOT;
2749         plist_node_init(&p->list, 0);
2750         for_each_node(i)
2751                 plist_node_init(&p->avail_lists[i], 0);
2752         p->flags = SWP_USED;
2753         spin_unlock(&swap_lock);
2754         if (defer) {
2755                 percpu_ref_exit(&defer->users);
2756                 kvfree(defer);
2757         }
2758         spin_lock_init(&p->lock);
2759         spin_lock_init(&p->cont_lock);
2760         init_completion(&p->comp);
2761
2762         return p;
2763 }
2764
2765 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2766 {
2767         int error;
2768
2769         if (S_ISBLK(inode->i_mode)) {
2770                 p->bdev = blkdev_get_by_dev(inode->i_rdev,
2771                                    FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2772                 if (IS_ERR(p->bdev)) {
2773                         error = PTR_ERR(p->bdev);
2774                         p->bdev = NULL;
2775                         return error;
2776                 }
2777                 p->old_block_size = block_size(p->bdev);
2778                 error = set_blocksize(p->bdev, PAGE_SIZE);
2779                 if (error < 0)
2780                         return error;
2781                 /*
2782                  * Zoned block devices contain zones that have a sequential
2783                  * write only restriction.  Hence zoned block devices are not
2784                  * suitable for swapping.  Disallow them here.
2785                  */
2786                 if (bdev_is_zoned(p->bdev))
2787                         return -EINVAL;
2788                 p->flags |= SWP_BLKDEV;
2789         } else if (S_ISREG(inode->i_mode)) {
2790                 p->bdev = inode->i_sb->s_bdev;
2791         }
2792
2793         return 0;
2794 }
2795
2796
2797 /*
2798  * Find out how many pages are allowed for a single swap device. There
2799  * are two limiting factors:
2800  * 1) the number of bits for the swap offset in the swp_entry_t type, and
2801  * 2) the number of bits in the swap pte, as defined by the different
2802  * architectures.
2803  *
2804  * In order to find the largest possible bit mask, a swap entry with
2805  * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2806  * decoded to a swp_entry_t again, and finally the swap offset is
2807  * extracted.
2808  *
2809  * This will mask all the bits from the initial ~0UL mask that can't
2810  * be encoded in either the swp_entry_t or the architecture definition
2811  * of a swap pte.
2812  */
2813 unsigned long generic_max_swapfile_size(void)
2814 {
2815         return swp_offset(pte_to_swp_entry(
2816                         swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2817 }
2818
2819 /* Can be overridden by an architecture for additional checks. */
2820 __weak unsigned long max_swapfile_size(void)
2821 {
2822         return generic_max_swapfile_size();
2823 }
2824
2825 static unsigned long read_swap_header(struct swap_info_struct *p,
2826                                         union swap_header *swap_header,
2827                                         struct inode *inode)
2828 {
2829         int i;
2830         unsigned long maxpages;
2831         unsigned long swapfilepages;
2832         unsigned long last_page;
2833
2834         if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2835                 pr_err("Unable to find swap-space signature\n");
2836                 return 0;
2837         }
2838
2839         /* swap partition endianness hack... */
2840         if (swab32(swap_header->info.version) == 1) {
2841                 swab32s(&swap_header->info.version);
2842                 swab32s(&swap_header->info.last_page);
2843                 swab32s(&swap_header->info.nr_badpages);
2844                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2845                         return 0;
2846                 for (i = 0; i < swap_header->info.nr_badpages; i++)
2847                         swab32s(&swap_header->info.badpages[i]);
2848         }
2849         /* Check the swap header's sub-version */
2850         if (swap_header->info.version != 1) {
2851                 pr_warn("Unable to handle swap header version %d\n",
2852                         swap_header->info.version);
2853                 return 0;
2854         }
2855
2856         p->lowest_bit  = 1;
2857         p->cluster_next = 1;
2858         p->cluster_nr = 0;
2859
2860         maxpages = max_swapfile_size();
2861         last_page = swap_header->info.last_page;
2862         if (!last_page) {
2863                 pr_warn("Empty swap-file\n");
2864                 return 0;
2865         }
2866         if (last_page > maxpages) {
2867                 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2868                         maxpages << (PAGE_SHIFT - 10),
2869                         last_page << (PAGE_SHIFT - 10));
2870         }
2871         if (maxpages > last_page) {
2872                 maxpages = last_page + 1;
2873                 /* p->max is an unsigned int: don't overflow it */
2874                 if ((unsigned int)maxpages == 0)
2875                         maxpages = UINT_MAX;
2876         }
2877         p->highest_bit = maxpages - 1;
2878
2879         if (!maxpages)
2880                 return 0;
2881         swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2882         if (swapfilepages && maxpages > swapfilepages) {
2883                 pr_warn("Swap area shorter than signature indicates\n");
2884                 return 0;
2885         }
2886         if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2887                 return 0;
2888         if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2889                 return 0;
2890
2891         return maxpages;
2892 }
2893
2894 #define SWAP_CLUSTER_INFO_COLS                                          \
2895         DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
2896 #define SWAP_CLUSTER_SPACE_COLS                                         \
2897         DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
2898 #define SWAP_CLUSTER_COLS                                               \
2899         max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
2900
2901 static int setup_swap_map_and_extents(struct swap_info_struct *p,
2902                                         union swap_header *swap_header,
2903                                         unsigned char *swap_map,
2904                                         struct swap_cluster_info *cluster_info,
2905                                         unsigned long maxpages,
2906                                         sector_t *span)
2907 {
2908         unsigned int j, k;
2909         unsigned int nr_good_pages;
2910         int nr_extents;
2911         unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2912         unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
2913         unsigned long i, idx;
2914
2915         nr_good_pages = maxpages - 1;   /* omit header page */
2916
2917         cluster_list_init(&p->free_clusters);
2918         cluster_list_init(&p->discard_clusters);
2919
2920         for (i = 0; i < swap_header->info.nr_badpages; i++) {
2921                 unsigned int page_nr = swap_header->info.badpages[i];
2922                 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2923                         return -EINVAL;
2924                 if (page_nr < maxpages) {
2925                         swap_map[page_nr] = SWAP_MAP_BAD;
2926                         nr_good_pages--;
2927                         /*
2928                          * Haven't marked the cluster free yet, no list
2929                          * operation involved
2930                          */
2931                         inc_cluster_info_page(p, cluster_info, page_nr);
2932                 }
2933         }
2934
2935         /* Haven't marked the cluster free yet, no list operation involved */
2936         for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2937                 inc_cluster_info_page(p, cluster_info, i);
2938
2939         if (nr_good_pages) {
2940                 swap_map[0] = SWAP_MAP_BAD;
2941                 /*
2942                  * Not mark the cluster free yet, no list
2943                  * operation involved
2944                  */
2945                 inc_cluster_info_page(p, cluster_info, 0);
2946                 p->max = maxpages;
2947                 p->pages = nr_good_pages;
2948                 nr_extents = setup_swap_extents(p, span);
2949                 if (nr_extents < 0)
2950                         return nr_extents;
2951                 nr_good_pages = p->pages;
2952         }
2953         if (!nr_good_pages) {
2954                 pr_warn("Empty swap-file\n");
2955                 return -EINVAL;
2956         }
2957
2958         if (!cluster_info)
2959                 return nr_extents;
2960
2961
2962         /*
2963          * Reduce false cache line sharing between cluster_info and
2964          * sharing same address space.
2965          */
2966         for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
2967                 j = (k + col) % SWAP_CLUSTER_COLS;
2968                 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
2969                         idx = i * SWAP_CLUSTER_COLS + j;
2970                         if (idx >= nr_clusters)
2971                                 continue;
2972                         if (cluster_count(&cluster_info[idx]))
2973                                 continue;
2974                         cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2975                         cluster_list_add_tail(&p->free_clusters, cluster_info,
2976                                               idx);
2977                 }
2978         }
2979         return nr_extents;
2980 }
2981
2982 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2983 {
2984         struct swap_info_struct *p;
2985         struct filename *name;
2986         struct file *swap_file = NULL;
2987         struct address_space *mapping;
2988         struct dentry *dentry;
2989         int prio;
2990         int error;
2991         union swap_header *swap_header;
2992         int nr_extents;
2993         sector_t span;
2994         unsigned long maxpages;
2995         unsigned char *swap_map = NULL;
2996         struct swap_cluster_info *cluster_info = NULL;
2997         unsigned long *frontswap_map = NULL;
2998         struct page *page = NULL;
2999         struct inode *inode = NULL;
3000         bool inced_nr_rotate_swap = false;
3001
3002         if (swap_flags & ~SWAP_FLAGS_VALID)
3003                 return -EINVAL;
3004
3005         if (!capable(CAP_SYS_ADMIN))
3006                 return -EPERM;
3007
3008         if (!swap_avail_heads)
3009                 return -ENOMEM;
3010
3011         p = alloc_swap_info();
3012         if (IS_ERR(p))
3013                 return PTR_ERR(p);
3014
3015         INIT_WORK(&p->discard_work, swap_discard_work);
3016
3017         name = getname(specialfile);
3018         if (IS_ERR(name)) {
3019                 error = PTR_ERR(name);
3020                 name = NULL;
3021                 goto bad_swap;
3022         }
3023         swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3024         if (IS_ERR(swap_file)) {
3025                 error = PTR_ERR(swap_file);
3026                 swap_file = NULL;
3027                 goto bad_swap;
3028         }
3029
3030         p->swap_file = swap_file;
3031         mapping = swap_file->f_mapping;
3032         dentry = swap_file->f_path.dentry;
3033         inode = mapping->host;
3034
3035         error = claim_swapfile(p, inode);
3036         if (unlikely(error))
3037                 goto bad_swap;
3038
3039         inode_lock(inode);
3040         if (d_unlinked(dentry) || cant_mount(dentry)) {
3041                 error = -ENOENT;
3042                 goto bad_swap_unlock_inode;
3043         }
3044         if (IS_SWAPFILE(inode)) {
3045                 error = -EBUSY;
3046                 goto bad_swap_unlock_inode;
3047         }
3048
3049         /*
3050          * Read the swap header.
3051          */
3052         if (!mapping->a_ops->read_folio) {
3053                 error = -EINVAL;
3054                 goto bad_swap_unlock_inode;
3055         }
3056         page = read_mapping_page(mapping, 0, swap_file);
3057         if (IS_ERR(page)) {
3058                 error = PTR_ERR(page);
3059                 goto bad_swap_unlock_inode;
3060         }
3061         swap_header = kmap(page);
3062
3063         maxpages = read_swap_header(p, swap_header, inode);
3064         if (unlikely(!maxpages)) {
3065                 error = -EINVAL;
3066                 goto bad_swap_unlock_inode;
3067         }
3068
3069         /* OK, set up the swap map and apply the bad block list */
3070         swap_map = vzalloc(maxpages);
3071         if (!swap_map) {
3072                 error = -ENOMEM;
3073                 goto bad_swap_unlock_inode;
3074         }
3075
3076         if (p->bdev && bdev_stable_writes(p->bdev))
3077                 p->flags |= SWP_STABLE_WRITES;
3078
3079         if (p->bdev && p->bdev->bd_disk->fops->rw_page)
3080                 p->flags |= SWP_SYNCHRONOUS_IO;
3081
3082         if (p->bdev && bdev_nonrot(p->bdev)) {
3083                 int cpu;
3084                 unsigned long ci, nr_cluster;
3085
3086                 p->flags |= SWP_SOLIDSTATE;
3087                 p->cluster_next_cpu = alloc_percpu(unsigned int);
3088                 if (!p->cluster_next_cpu) {
3089                         error = -ENOMEM;
3090                         goto bad_swap_unlock_inode;
3091                 }
3092                 /*
3093                  * select a random position to start with to help wear leveling
3094                  * SSD
3095                  */
3096                 for_each_possible_cpu(cpu) {
3097                         per_cpu(*p->cluster_next_cpu, cpu) =
3098                                 1 + prandom_u32_max(p->highest_bit);
3099                 }
3100                 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3101
3102                 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3103                                         GFP_KERNEL);
3104                 if (!cluster_info) {
3105                         error = -ENOMEM;
3106                         goto bad_swap_unlock_inode;
3107                 }
3108
3109                 for (ci = 0; ci < nr_cluster; ci++)
3110                         spin_lock_init(&((cluster_info + ci)->lock));
3111
3112                 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3113                 if (!p->percpu_cluster) {
3114                         error = -ENOMEM;
3115                         goto bad_swap_unlock_inode;
3116                 }
3117                 for_each_possible_cpu(cpu) {
3118                         struct percpu_cluster *cluster;
3119                         cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3120                         cluster_set_null(&cluster->index);
3121                 }
3122         } else {
3123                 atomic_inc(&nr_rotate_swap);
3124                 inced_nr_rotate_swap = true;
3125         }
3126
3127         error = swap_cgroup_swapon(p->type, maxpages);
3128         if (error)
3129                 goto bad_swap_unlock_inode;
3130
3131         nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3132                 cluster_info, maxpages, &span);
3133         if (unlikely(nr_extents < 0)) {
3134                 error = nr_extents;
3135                 goto bad_swap_unlock_inode;
3136         }
3137         /* frontswap enabled? set up bit-per-page map for frontswap */
3138         if (IS_ENABLED(CONFIG_FRONTSWAP))
3139                 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3140                                          sizeof(long),
3141                                          GFP_KERNEL);
3142
3143         if ((swap_flags & SWAP_FLAG_DISCARD) &&
3144             p->bdev && bdev_max_discard_sectors(p->bdev)) {
3145                 /*
3146                  * When discard is enabled for swap with no particular
3147                  * policy flagged, we set all swap discard flags here in
3148                  * order to sustain backward compatibility with older
3149                  * swapon(8) releases.
3150                  */
3151                 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3152                              SWP_PAGE_DISCARD);
3153
3154                 /*
3155                  * By flagging sys_swapon, a sysadmin can tell us to
3156                  * either do single-time area discards only, or to just
3157                  * perform discards for released swap page-clusters.
3158                  * Now it's time to adjust the p->flags accordingly.
3159                  */
3160                 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3161                         p->flags &= ~SWP_PAGE_DISCARD;
3162                 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3163                         p->flags &= ~SWP_AREA_DISCARD;
3164
3165                 /* issue a swapon-time discard if it's still required */
3166                 if (p->flags & SWP_AREA_DISCARD) {
3167                         int err = discard_swap(p);
3168                         if (unlikely(err))
3169                                 pr_err("swapon: discard_swap(%p): %d\n",
3170                                         p, err);
3171                 }
3172         }
3173
3174         error = init_swap_address_space(p->type, maxpages);
3175         if (error)
3176                 goto bad_swap_unlock_inode;
3177
3178         /*
3179          * Flush any pending IO and dirty mappings before we start using this
3180          * swap device.
3181          */
3182         inode->i_flags |= S_SWAPFILE;
3183         error = inode_drain_writes(inode);
3184         if (error) {
3185                 inode->i_flags &= ~S_SWAPFILE;
3186                 goto free_swap_address_space;
3187         }
3188
3189         mutex_lock(&swapon_mutex);
3190         prio = -1;
3191         if (swap_flags & SWAP_FLAG_PREFER)
3192                 prio =
3193                   (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3194         enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3195
3196         pr_info("Adding %uk swap on %s.  Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3197                 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3198                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3199                 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3200                 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3201                 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3202                 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3203                 (frontswap_map) ? "FS" : "");
3204
3205         mutex_unlock(&swapon_mutex);
3206         atomic_inc(&proc_poll_event);
3207         wake_up_interruptible(&proc_poll_wait);
3208
3209         error = 0;
3210         goto out;
3211 free_swap_address_space:
3212         exit_swap_address_space(p->type);
3213 bad_swap_unlock_inode:
3214         inode_unlock(inode);
3215 bad_swap:
3216         free_percpu(p->percpu_cluster);
3217         p->percpu_cluster = NULL;
3218         free_percpu(p->cluster_next_cpu);
3219         p->cluster_next_cpu = NULL;
3220         if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3221                 set_blocksize(p->bdev, p->old_block_size);
3222                 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3223         }
3224         inode = NULL;
3225         destroy_swap_extents(p);
3226         swap_cgroup_swapoff(p->type);
3227         spin_lock(&swap_lock);
3228         p->swap_file = NULL;
3229         p->flags = 0;
3230         spin_unlock(&swap_lock);
3231         vfree(swap_map);
3232         kvfree(cluster_info);
3233         kvfree(frontswap_map);
3234         if (inced_nr_rotate_swap)
3235                 atomic_dec(&nr_rotate_swap);
3236         if (swap_file)
3237                 filp_close(swap_file, NULL);
3238 out:
3239         if (page && !IS_ERR(page)) {
3240                 kunmap(page);
3241                 put_page(page);
3242         }
3243         if (name)
3244                 putname(name);
3245         if (inode)
3246                 inode_unlock(inode);
3247         if (!error)
3248                 enable_swap_slots_cache();
3249         return error;
3250 }
3251
3252 void si_swapinfo(struct sysinfo *val)
3253 {
3254         unsigned int type;
3255         unsigned long nr_to_be_unused = 0;
3256
3257         spin_lock(&swap_lock);
3258         for (type = 0; type < nr_swapfiles; type++) {
3259                 struct swap_info_struct *si = swap_info[type];
3260
3261                 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3262                         nr_to_be_unused += si->inuse_pages;
3263         }
3264         val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3265         val->totalswap = total_swap_pages + nr_to_be_unused;
3266         spin_unlock(&swap_lock);
3267 }
3268
3269 /*
3270  * Verify that a swap entry is valid and increment its swap map count.
3271  *
3272  * Returns error code in following case.
3273  * - success -> 0
3274  * - swp_entry is invalid -> EINVAL
3275  * - swp_entry is migration entry -> EINVAL
3276  * - swap-cache reference is requested but there is already one. -> EEXIST
3277  * - swap-cache reference is requested but the entry is not used. -> ENOENT
3278  * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3279  */
3280 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3281 {
3282         struct swap_info_struct *p;
3283         struct swap_cluster_info *ci;
3284         unsigned long offset;
3285         unsigned char count;
3286         unsigned char has_cache;
3287         int err;
3288
3289         p = get_swap_device(entry);
3290         if (!p)
3291                 return -EINVAL;
3292
3293         offset = swp_offset(entry);
3294         ci = lock_cluster_or_swap_info(p, offset);
3295
3296         count = p->swap_map[offset];
3297
3298         /*
3299          * swapin_readahead() doesn't check if a swap entry is valid, so the
3300          * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3301          */
3302         if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3303                 err = -ENOENT;
3304                 goto unlock_out;
3305         }
3306
3307         has_cache = count & SWAP_HAS_CACHE;
3308         count &= ~SWAP_HAS_CACHE;
3309         err = 0;
3310
3311         if (usage == SWAP_HAS_CACHE) {
3312
3313                 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3314                 if (!has_cache && count)
3315                         has_cache = SWAP_HAS_CACHE;
3316                 else if (has_cache)             /* someone else added cache */
3317                         err = -EEXIST;
3318                 else                            /* no users remaining */
3319                         err = -ENOENT;
3320
3321         } else if (count || has_cache) {
3322
3323                 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3324                         count += usage;
3325                 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3326                         err = -EINVAL;
3327                 else if (swap_count_continued(p, offset, count))
3328                         count = COUNT_CONTINUED;
3329                 else
3330                         err = -ENOMEM;
3331         } else
3332                 err = -ENOENT;                  /* unused swap entry */
3333
3334         WRITE_ONCE(p->swap_map[offset], count | has_cache);
3335
3336 unlock_out:
3337         unlock_cluster_or_swap_info(p, ci);
3338         put_swap_device(p);
3339         return err;
3340 }
3341
3342 /*
3343  * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3344  * (in which case its reference count is never incremented).
3345  */
3346 void swap_shmem_alloc(swp_entry_t entry)
3347 {
3348         __swap_duplicate(entry, SWAP_MAP_SHMEM);
3349 }
3350
3351 /*
3352  * Increase reference count of swap entry by 1.
3353  * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3354  * but could not be atomically allocated.  Returns 0, just as if it succeeded,
3355  * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3356  * might occur if a page table entry has got corrupted.
3357  */
3358 int swap_duplicate(swp_entry_t entry)
3359 {
3360         int err = 0;
3361
3362         while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3363                 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3364         return err;
3365 }
3366
3367 /*
3368  * @entry: swap entry for which we allocate swap cache.
3369  *
3370  * Called when allocating swap cache for existing swap entry,
3371  * This can return error codes. Returns 0 at success.
3372  * -EEXIST means there is a swap cache.
3373  * Note: return code is different from swap_duplicate().
3374  */
3375 int swapcache_prepare(swp_entry_t entry)
3376 {
3377         return __swap_duplicate(entry, SWAP_HAS_CACHE);
3378 }
3379
3380 struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3381 {
3382         return swap_type_to_swap_info(swp_type(entry));
3383 }
3384
3385 struct swap_info_struct *page_swap_info(struct page *page)
3386 {
3387         swp_entry_t entry = { .val = page_private(page) };
3388         return swp_swap_info(entry);
3389 }
3390
3391 /*
3392  * out-of-line methods to avoid include hell.
3393  */
3394 struct address_space *swapcache_mapping(struct folio *folio)
3395 {
3396         return page_swap_info(&folio->page)->swap_file->f_mapping;
3397 }
3398 EXPORT_SYMBOL_GPL(swapcache_mapping);
3399
3400 pgoff_t __page_file_index(struct page *page)
3401 {
3402         swp_entry_t swap = { .val = page_private(page) };
3403         return swp_offset(swap);
3404 }
3405 EXPORT_SYMBOL_GPL(__page_file_index);
3406
3407 /*
3408  * add_swap_count_continuation - called when a swap count is duplicated
3409  * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3410  * page of the original vmalloc'ed swap_map, to hold the continuation count
3411  * (for that entry and for its neighbouring PAGE_SIZE swap entries).  Called
3412  * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3413  *
3414  * These continuation pages are seldom referenced: the common paths all work
3415  * on the original swap_map, only referring to a continuation page when the
3416  * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3417  *
3418  * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3419  * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3420  * can be called after dropping locks.
3421  */
3422 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3423 {
3424         struct swap_info_struct *si;
3425         struct swap_cluster_info *ci;
3426         struct page *head;
3427         struct page *page;
3428         struct page *list_page;
3429         pgoff_t offset;
3430         unsigned char count;
3431         int ret = 0;
3432
3433         /*
3434          * When debugging, it's easier to use __GFP_ZERO here; but it's better
3435          * for latency not to zero a page while GFP_ATOMIC and holding locks.
3436          */
3437         page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3438
3439         si = get_swap_device(entry);
3440         if (!si) {
3441                 /*
3442                  * An acceptable race has occurred since the failing
3443                  * __swap_duplicate(): the swap device may be swapoff
3444                  */
3445                 goto outer;
3446         }
3447         spin_lock(&si->lock);
3448
3449         offset = swp_offset(entry);
3450
3451         ci = lock_cluster(si, offset);
3452
3453         count = swap_count(si->swap_map[offset]);
3454
3455         if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3456                 /*
3457                  * The higher the swap count, the more likely it is that tasks
3458                  * will race to add swap count continuation: we need to avoid
3459                  * over-provisioning.
3460                  */
3461                 goto out;
3462         }
3463
3464         if (!page) {
3465                 ret = -ENOMEM;
3466                 goto out;
3467         }
3468
3469         /*
3470          * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3471          * no architecture is using highmem pages for kernel page tables: so it
3472          * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3473          */
3474         head = vmalloc_to_page(si->swap_map + offset);
3475         offset &= ~PAGE_MASK;
3476
3477         spin_lock(&si->cont_lock);
3478         /*
3479          * Page allocation does not initialize the page's lru field,
3480          * but it does always reset its private field.
3481          */
3482         if (!page_private(head)) {
3483                 BUG_ON(count & COUNT_CONTINUED);
3484                 INIT_LIST_HEAD(&head->lru);
3485                 set_page_private(head, SWP_CONTINUED);
3486                 si->flags |= SWP_CONTINUED;
3487         }
3488
3489         list_for_each_entry(list_page, &head->lru, lru) {
3490                 unsigned char *map;
3491
3492                 /*
3493                  * If the previous map said no continuation, but we've found
3494                  * a continuation page, free our allocation and use this one.
3495                  */
3496                 if (!(count & COUNT_CONTINUED))
3497                         goto out_unlock_cont;
3498
3499                 map = kmap_atomic(list_page) + offset;
3500                 count = *map;
3501                 kunmap_atomic(map);
3502
3503                 /*
3504                  * If this continuation count now has some space in it,
3505                  * free our allocation and use this one.
3506                  */
3507                 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3508                         goto out_unlock_cont;
3509         }
3510
3511         list_add_tail(&page->lru, &head->lru);
3512         page = NULL;                    /* now it's attached, don't free it */
3513 out_unlock_cont:
3514         spin_unlock(&si->cont_lock);
3515 out:
3516         unlock_cluster(ci);
3517         spin_unlock(&si->lock);
3518         put_swap_device(si);
3519 outer:
3520         if (page)
3521                 __free_page(page);
3522         return ret;
3523 }
3524
3525 /*
3526  * swap_count_continued - when the original swap_map count is incremented
3527  * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3528  * into, carry if so, or else fail until a new continuation page is allocated;
3529  * when the original swap_map count is decremented from 0 with continuation,
3530  * borrow from the continuation and report whether it still holds more.
3531  * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3532  * lock.
3533  */
3534 static bool swap_count_continued(struct swap_info_struct *si,
3535                                  pgoff_t offset, unsigned char count)
3536 {
3537         struct page *head;
3538         struct page *page;
3539         unsigned char *map;
3540         bool ret;
3541
3542         head = vmalloc_to_page(si->swap_map + offset);
3543         if (page_private(head) != SWP_CONTINUED) {
3544                 BUG_ON(count & COUNT_CONTINUED);
3545                 return false;           /* need to add count continuation */
3546         }
3547
3548         spin_lock(&si->cont_lock);
3549         offset &= ~PAGE_MASK;
3550         page = list_next_entry(head, lru);
3551         map = kmap_atomic(page) + offset;
3552
3553         if (count == SWAP_MAP_MAX)      /* initial increment from swap_map */
3554                 goto init_map;          /* jump over SWAP_CONT_MAX checks */
3555
3556         if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3557                 /*
3558                  * Think of how you add 1 to 999
3559                  */
3560                 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3561                         kunmap_atomic(map);
3562                         page = list_next_entry(page, lru);
3563                         BUG_ON(page == head);
3564                         map = kmap_atomic(page) + offset;
3565                 }
3566                 if (*map == SWAP_CONT_MAX) {
3567                         kunmap_atomic(map);
3568                         page = list_next_entry(page, lru);
3569                         if (page == head) {
3570                                 ret = false;    /* add count continuation */
3571                                 goto out;
3572                         }
3573                         map = kmap_atomic(page) + offset;
3574 init_map:               *map = 0;               /* we didn't zero the page */
3575                 }
3576                 *map += 1;
3577                 kunmap_atomic(map);
3578                 while ((page = list_prev_entry(page, lru)) != head) {
3579                         map = kmap_atomic(page) + offset;
3580                         *map = COUNT_CONTINUED;
3581                         kunmap_atomic(map);
3582                 }
3583                 ret = true;                     /* incremented */
3584
3585         } else {                                /* decrementing */
3586                 /*
3587                  * Think of how you subtract 1 from 1000
3588                  */
3589                 BUG_ON(count != COUNT_CONTINUED);
3590                 while (*map == COUNT_CONTINUED) {
3591                         kunmap_atomic(map);
3592                         page = list_next_entry(page, lru);
3593                         BUG_ON(page == head);
3594                         map = kmap_atomic(page) + offset;
3595                 }
3596                 BUG_ON(*map == 0);
3597                 *map -= 1;
3598                 if (*map == 0)
3599                         count = 0;
3600                 kunmap_atomic(map);
3601                 while ((page = list_prev_entry(page, lru)) != head) {
3602                         map = kmap_atomic(page) + offset;
3603                         *map = SWAP_CONT_MAX | count;
3604                         count = COUNT_CONTINUED;
3605                         kunmap_atomic(map);
3606                 }
3607                 ret = count == COUNT_CONTINUED;
3608         }
3609 out:
3610         spin_unlock(&si->cont_lock);
3611         return ret;
3612 }
3613
3614 /*
3615  * free_swap_count_continuations - swapoff free all the continuation pages
3616  * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3617  */
3618 static void free_swap_count_continuations(struct swap_info_struct *si)
3619 {
3620         pgoff_t offset;
3621
3622         for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3623                 struct page *head;
3624                 head = vmalloc_to_page(si->swap_map + offset);
3625                 if (page_private(head)) {
3626                         struct page *page, *next;
3627
3628                         list_for_each_entry_safe(page, next, &head->lru, lru) {
3629                                 list_del(&page->lru);
3630                                 __free_page(page);
3631                         }
3632                 }
3633         }
3634 }
3635
3636 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3637 void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
3638 {
3639         struct swap_info_struct *si, *next;
3640         int nid = page_to_nid(page);
3641
3642         if (!(gfp_mask & __GFP_IO))
3643                 return;
3644
3645         if (!blk_cgroup_congested())
3646                 return;
3647
3648         /*
3649          * We've already scheduled a throttle, avoid taking the global swap
3650          * lock.
3651          */
3652         if (current->throttle_queue)
3653                 return;
3654
3655         spin_lock(&swap_avail_lock);
3656         plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
3657                                   avail_lists[nid]) {
3658                 if (si->bdev) {
3659                         blkcg_schedule_throttle(bdev_get_queue(si->bdev), true);
3660                         break;
3661                 }
3662         }
3663         spin_unlock(&swap_avail_lock);
3664 }
3665 #endif
3666
3667 static int __init swapfile_init(void)
3668 {
3669         int nid;
3670
3671         swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3672                                          GFP_KERNEL);
3673         if (!swap_avail_heads) {
3674                 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3675                 return -ENOMEM;
3676         }
3677
3678         for_each_node(nid)
3679                 plist_head_init(&swap_avail_heads[nid]);
3680
3681         return 0;
3682 }
3683 subsys_initcall(swapfile_init);