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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/swapfile.c
4 *
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie
7 */
8
9#include <linux/mm.h>
10#include <linux/sched/mm.h>
11#include <linux/sched/task.h>
12#include <linux/hugetlb.h>
13#include <linux/mman.h>
14#include <linux/slab.h>
15#include <linux/kernel_stat.h>
16#include <linux/swap.h>
17#include <linux/vmalloc.h>
18#include <linux/pagemap.h>
19#include <linux/namei.h>
20#include <linux/shmem_fs.h>
21#include <linux/blkdev.h>
22#include <linux/random.h>
23#include <linux/writeback.h>
24#include <linux/proc_fs.h>
25#include <linux/seq_file.h>
26#include <linux/init.h>
27#include <linux/ksm.h>
28#include <linux/rmap.h>
29#include <linux/security.h>
30#include <linux/backing-dev.h>
31#include <linux/mutex.h>
32#include <linux/capability.h>
33#include <linux/syscalls.h>
34#include <linux/memcontrol.h>
35#include <linux/poll.h>
36#include <linux/oom.h>
37#include <linux/frontswap.h>
38#include <linux/swapfile.h>
39#include <linux/export.h>
40#include <linux/swap_slots.h>
41#include <linux/sort.h>
42
43#include <asm/pgtable.h>
44#include <asm/tlbflush.h>
45#include <linux/swapops.h>
46#include <linux/swap_cgroup.h>
47
48static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
49 unsigned char);
50static void free_swap_count_continuations(struct swap_info_struct *);
51static sector_t map_swap_entry(swp_entry_t, struct block_device**);
52
53DEFINE_SPINLOCK(swap_lock);
54static unsigned int nr_swapfiles;
55atomic_long_t nr_swap_pages;
56/*
57 * Some modules use swappable objects and may try to swap them out under
58 * memory pressure (via the shrinker). Before doing so, they may wish to
59 * check to see if any swap space is available.
60 */
61EXPORT_SYMBOL_GPL(nr_swap_pages);
62/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
63long total_swap_pages;
64static int least_priority = -1;
65
66static const char Bad_file[] = "Bad swap file entry ";
67static const char Unused_file[] = "Unused swap file entry ";
68static const char Bad_offset[] = "Bad swap offset entry ";
69static const char Unused_offset[] = "Unused swap offset entry ";
70
71/*
72 * all active swap_info_structs
73 * protected with swap_lock, and ordered by priority.
74 */
75PLIST_HEAD(swap_active_head);
76
77/*
78 * all available (active, not full) swap_info_structs
79 * protected with swap_avail_lock, ordered by priority.
80 * This is used by get_swap_page() instead of swap_active_head
81 * because swap_active_head includes all swap_info_structs,
82 * but get_swap_page() doesn't need to look at full ones.
83 * This uses its own lock instead of swap_lock because when a
84 * swap_info_struct changes between not-full/full, it needs to
85 * add/remove itself to/from this list, but the swap_info_struct->lock
86 * is held and the locking order requires swap_lock to be taken
87 * before any swap_info_struct->lock.
88 */
89static struct plist_head *swap_avail_heads;
90static DEFINE_SPINLOCK(swap_avail_lock);
91
92struct swap_info_struct *swap_info[MAX_SWAPFILES];
93
94static DEFINE_MUTEX(swapon_mutex);
95
96static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
97/* Activity counter to indicate that a swapon or swapoff has occurred */
98static atomic_t proc_poll_event = ATOMIC_INIT(0);
99
100atomic_t nr_rotate_swap = ATOMIC_INIT(0);
101
102static struct swap_info_struct *swap_type_to_swap_info(int type)
103{
104 if (type >= READ_ONCE(nr_swapfiles))
105 return NULL;
106
107 smp_rmb(); /* Pairs with smp_wmb in alloc_swap_info. */
108 return READ_ONCE(swap_info[type]);
109}
110
111static 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 */
127static 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
155static 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
161static 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 */
171static 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, 0);
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, 0);
196 if (err)
197 break;
198
199 cond_resched();
200 }
201 return err; /* That will often be -EOPNOTSUPP */
202}
203
204static struct swap_extent *
205offset_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/*
225 * swap allocation tell device that a cluster of swap can now be discarded,
226 * to allow the swap device to optimize its wear-levelling.
227 */
228static void discard_swap_cluster(struct swap_info_struct *si,
229 pgoff_t start_page, pgoff_t nr_pages)
230{
231 struct swap_extent *se = offset_to_swap_extent(si, start_page);
232
233 while (nr_pages) {
234 pgoff_t offset = start_page - se->start_page;
235 sector_t start_block = se->start_block + offset;
236 sector_t nr_blocks = se->nr_pages - offset;
237
238 if (nr_blocks > nr_pages)
239 nr_blocks = nr_pages;
240 start_page += nr_blocks;
241 nr_pages -= nr_blocks;
242
243 start_block <<= PAGE_SHIFT - 9;
244 nr_blocks <<= PAGE_SHIFT - 9;
245 if (blkdev_issue_discard(si->bdev, start_block,
246 nr_blocks, GFP_NOIO, 0))
247 break;
248
249 se = next_se(se);
250 }
251}
252
253#ifdef CONFIG_THP_SWAP
254#define SWAPFILE_CLUSTER HPAGE_PMD_NR
255
256#define swap_entry_size(size) (size)
257#else
258#define SWAPFILE_CLUSTER 256
259
260/*
261 * Define swap_entry_size() as constant to let compiler to optimize
262 * out some code if !CONFIG_THP_SWAP
263 */
264#define swap_entry_size(size) 1
265#endif
266#define LATENCY_LIMIT 256
267
268static inline void cluster_set_flag(struct swap_cluster_info *info,
269 unsigned int flag)
270{
271 info->flags = flag;
272}
273
274static inline unsigned int cluster_count(struct swap_cluster_info *info)
275{
276 return info->data;
277}
278
279static inline void cluster_set_count(struct swap_cluster_info *info,
280 unsigned int c)
281{
282 info->data = c;
283}
284
285static inline void cluster_set_count_flag(struct swap_cluster_info *info,
286 unsigned int c, unsigned int f)
287{
288 info->flags = f;
289 info->data = c;
290}
291
292static inline unsigned int cluster_next(struct swap_cluster_info *info)
293{
294 return info->data;
295}
296
297static inline void cluster_set_next(struct swap_cluster_info *info,
298 unsigned int n)
299{
300 info->data = n;
301}
302
303static inline void cluster_set_next_flag(struct swap_cluster_info *info,
304 unsigned int n, unsigned int f)
305{
306 info->flags = f;
307 info->data = n;
308}
309
310static inline bool cluster_is_free(struct swap_cluster_info *info)
311{
312 return info->flags & CLUSTER_FLAG_FREE;
313}
314
315static inline bool cluster_is_null(struct swap_cluster_info *info)
316{
317 return info->flags & CLUSTER_FLAG_NEXT_NULL;
318}
319
320static inline void cluster_set_null(struct swap_cluster_info *info)
321{
322 info->flags = CLUSTER_FLAG_NEXT_NULL;
323 info->data = 0;
324}
325
326static inline bool cluster_is_huge(struct swap_cluster_info *info)
327{
328 if (IS_ENABLED(CONFIG_THP_SWAP))
329 return info->flags & CLUSTER_FLAG_HUGE;
330 return false;
331}
332
333static inline void cluster_clear_huge(struct swap_cluster_info *info)
334{
335 info->flags &= ~CLUSTER_FLAG_HUGE;
336}
337
338static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
339 unsigned long offset)
340{
341 struct swap_cluster_info *ci;
342
343 ci = si->cluster_info;
344 if (ci) {
345 ci += offset / SWAPFILE_CLUSTER;
346 spin_lock(&ci->lock);
347 }
348 return ci;
349}
350
351static inline void unlock_cluster(struct swap_cluster_info *ci)
352{
353 if (ci)
354 spin_unlock(&ci->lock);
355}
356
357/*
358 * Determine the locking method in use for this device. Return
359 * swap_cluster_info if SSD-style cluster-based locking is in place.
360 */
361static inline struct swap_cluster_info *lock_cluster_or_swap_info(
362 struct swap_info_struct *si, unsigned long offset)
363{
364 struct swap_cluster_info *ci;
365
366 /* Try to use fine-grained SSD-style locking if available: */
367 ci = lock_cluster(si, offset);
368 /* Otherwise, fall back to traditional, coarse locking: */
369 if (!ci)
370 spin_lock(&si->lock);
371
372 return ci;
373}
374
375static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
376 struct swap_cluster_info *ci)
377{
378 if (ci)
379 unlock_cluster(ci);
380 else
381 spin_unlock(&si->lock);
382}
383
384static inline bool cluster_list_empty(struct swap_cluster_list *list)
385{
386 return cluster_is_null(&list->head);
387}
388
389static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
390{
391 return cluster_next(&list->head);
392}
393
394static void cluster_list_init(struct swap_cluster_list *list)
395{
396 cluster_set_null(&list->head);
397 cluster_set_null(&list->tail);
398}
399
400static void cluster_list_add_tail(struct swap_cluster_list *list,
401 struct swap_cluster_info *ci,
402 unsigned int idx)
403{
404 if (cluster_list_empty(list)) {
405 cluster_set_next_flag(&list->head, idx, 0);
406 cluster_set_next_flag(&list->tail, idx, 0);
407 } else {
408 struct swap_cluster_info *ci_tail;
409 unsigned int tail = cluster_next(&list->tail);
410
411 /*
412 * Nested cluster lock, but both cluster locks are
413 * only acquired when we held swap_info_struct->lock
414 */
415 ci_tail = ci + tail;
416 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
417 cluster_set_next(ci_tail, idx);
418 spin_unlock(&ci_tail->lock);
419 cluster_set_next_flag(&list->tail, idx, 0);
420 }
421}
422
423static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
424 struct swap_cluster_info *ci)
425{
426 unsigned int idx;
427
428 idx = cluster_next(&list->head);
429 if (cluster_next(&list->tail) == idx) {
430 cluster_set_null(&list->head);
431 cluster_set_null(&list->tail);
432 } else
433 cluster_set_next_flag(&list->head,
434 cluster_next(&ci[idx]), 0);
435
436 return idx;
437}
438
439/* Add a cluster to discard list and schedule it to do discard */
440static void swap_cluster_schedule_discard(struct swap_info_struct *si,
441 unsigned int idx)
442{
443 /*
444 * If scan_swap_map() can't find a free cluster, it will check
445 * si->swap_map directly. To make sure the discarding cluster isn't
446 * taken by scan_swap_map(), mark the swap entries bad (occupied). It
447 * will be cleared after discard
448 */
449 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
450 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
451
452 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
453
454 schedule_work(&si->discard_work);
455}
456
457static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
458{
459 struct swap_cluster_info *ci = si->cluster_info;
460
461 cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
462 cluster_list_add_tail(&si->free_clusters, ci, idx);
463}
464
465/*
466 * Doing discard actually. After a cluster discard is finished, the cluster
467 * will be added to free cluster list. caller should hold si->lock.
468*/
469static void swap_do_scheduled_discard(struct swap_info_struct *si)
470{
471 struct swap_cluster_info *info, *ci;
472 unsigned int idx;
473
474 info = si->cluster_info;
475
476 while (!cluster_list_empty(&si->discard_clusters)) {
477 idx = cluster_list_del_first(&si->discard_clusters, info);
478 spin_unlock(&si->lock);
479
480 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
481 SWAPFILE_CLUSTER);
482
483 spin_lock(&si->lock);
484 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
485 __free_cluster(si, idx);
486 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
487 0, SWAPFILE_CLUSTER);
488 unlock_cluster(ci);
489 }
490}
491
492static void swap_discard_work(struct work_struct *work)
493{
494 struct swap_info_struct *si;
495
496 si = container_of(work, struct swap_info_struct, discard_work);
497
498 spin_lock(&si->lock);
499 swap_do_scheduled_discard(si);
500 spin_unlock(&si->lock);
501}
502
503static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
504{
505 struct swap_cluster_info *ci = si->cluster_info;
506
507 VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
508 cluster_list_del_first(&si->free_clusters, ci);
509 cluster_set_count_flag(ci + idx, 0, 0);
510}
511
512static void free_cluster(struct swap_info_struct *si, unsigned long idx)
513{
514 struct swap_cluster_info *ci = si->cluster_info + idx;
515
516 VM_BUG_ON(cluster_count(ci) != 0);
517 /*
518 * If the swap is discardable, prepare discard the cluster
519 * instead of free it immediately. The cluster will be freed
520 * after discard.
521 */
522 if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
523 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
524 swap_cluster_schedule_discard(si, idx);
525 return;
526 }
527
528 __free_cluster(si, idx);
529}
530
531/*
532 * The cluster corresponding to page_nr will be used. The cluster will be
533 * removed from free cluster list and its usage counter will be increased.
534 */
535static void inc_cluster_info_page(struct swap_info_struct *p,
536 struct swap_cluster_info *cluster_info, unsigned long page_nr)
537{
538 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
539
540 if (!cluster_info)
541 return;
542 if (cluster_is_free(&cluster_info[idx]))
543 alloc_cluster(p, idx);
544
545 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
546 cluster_set_count(&cluster_info[idx],
547 cluster_count(&cluster_info[idx]) + 1);
548}
549
550/*
551 * The cluster corresponding to page_nr decreases one usage. If the usage
552 * counter becomes 0, which means no page in the cluster is in using, we can
553 * optionally discard the cluster and add it to free cluster list.
554 */
555static void dec_cluster_info_page(struct swap_info_struct *p,
556 struct swap_cluster_info *cluster_info, unsigned long page_nr)
557{
558 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
559
560 if (!cluster_info)
561 return;
562
563 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
564 cluster_set_count(&cluster_info[idx],
565 cluster_count(&cluster_info[idx]) - 1);
566
567 if (cluster_count(&cluster_info[idx]) == 0)
568 free_cluster(p, idx);
569}
570
571/*
572 * It's possible scan_swap_map() uses a free cluster in the middle of free
573 * cluster list. Avoiding such abuse to avoid list corruption.
574 */
575static bool
576scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
577 unsigned long offset)
578{
579 struct percpu_cluster *percpu_cluster;
580 bool conflict;
581
582 offset /= SWAPFILE_CLUSTER;
583 conflict = !cluster_list_empty(&si->free_clusters) &&
584 offset != cluster_list_first(&si->free_clusters) &&
585 cluster_is_free(&si->cluster_info[offset]);
586
587 if (!conflict)
588 return false;
589
590 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
591 cluster_set_null(&percpu_cluster->index);
592 return true;
593}
594
595/*
596 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
597 * might involve allocating a new cluster for current CPU too.
598 */
599static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
600 unsigned long *offset, unsigned long *scan_base)
601{
602 struct percpu_cluster *cluster;
603 struct swap_cluster_info *ci;
604 bool found_free;
605 unsigned long tmp, max;
606
607new_cluster:
608 cluster = this_cpu_ptr(si->percpu_cluster);
609 if (cluster_is_null(&cluster->index)) {
610 if (!cluster_list_empty(&si->free_clusters)) {
611 cluster->index = si->free_clusters.head;
612 cluster->next = cluster_next(&cluster->index) *
613 SWAPFILE_CLUSTER;
614 } else if (!cluster_list_empty(&si->discard_clusters)) {
615 /*
616 * we don't have free cluster but have some clusters in
617 * discarding, do discard now and reclaim them
618 */
619 swap_do_scheduled_discard(si);
620 *scan_base = *offset = si->cluster_next;
621 goto new_cluster;
622 } else
623 return false;
624 }
625
626 found_free = false;
627
628 /*
629 * Other CPUs can use our cluster if they can't find a free cluster,
630 * check if there is still free entry in the cluster
631 */
632 tmp = cluster->next;
633 max = min_t(unsigned long, si->max,
634 (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
635 if (tmp >= max) {
636 cluster_set_null(&cluster->index);
637 goto new_cluster;
638 }
639 ci = lock_cluster(si, tmp);
640 while (tmp < max) {
641 if (!si->swap_map[tmp]) {
642 found_free = true;
643 break;
644 }
645 tmp++;
646 }
647 unlock_cluster(ci);
648 if (!found_free) {
649 cluster_set_null(&cluster->index);
650 goto new_cluster;
651 }
652 cluster->next = tmp + 1;
653 *offset = tmp;
654 *scan_base = tmp;
655 return found_free;
656}
657
658static void __del_from_avail_list(struct swap_info_struct *p)
659{
660 int nid;
661
662 for_each_node(nid)
663 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
664}
665
666static void del_from_avail_list(struct swap_info_struct *p)
667{
668 spin_lock(&swap_avail_lock);
669 __del_from_avail_list(p);
670 spin_unlock(&swap_avail_lock);
671}
672
673static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
674 unsigned int nr_entries)
675{
676 unsigned int end = offset + nr_entries - 1;
677
678 if (offset == si->lowest_bit)
679 si->lowest_bit += nr_entries;
680 if (end == si->highest_bit)
681 si->highest_bit -= nr_entries;
682 si->inuse_pages += nr_entries;
683 if (si->inuse_pages == si->pages) {
684 si->lowest_bit = si->max;
685 si->highest_bit = 0;
686 del_from_avail_list(si);
687 }
688}
689
690static void add_to_avail_list(struct swap_info_struct *p)
691{
692 int nid;
693
694 spin_lock(&swap_avail_lock);
695 for_each_node(nid) {
696 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
697 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
698 }
699 spin_unlock(&swap_avail_lock);
700}
701
702static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
703 unsigned int nr_entries)
704{
705 unsigned long end = offset + nr_entries - 1;
706 void (*swap_slot_free_notify)(struct block_device *, unsigned long);
707
708 if (offset < si->lowest_bit)
709 si->lowest_bit = offset;
710 if (end > si->highest_bit) {
711 bool was_full = !si->highest_bit;
712
713 si->highest_bit = end;
714 if (was_full && (si->flags & SWP_WRITEOK))
715 add_to_avail_list(si);
716 }
717 atomic_long_add(nr_entries, &nr_swap_pages);
718 si->inuse_pages -= nr_entries;
719 if (si->flags & SWP_BLKDEV)
720 swap_slot_free_notify =
721 si->bdev->bd_disk->fops->swap_slot_free_notify;
722 else
723 swap_slot_free_notify = NULL;
724 while (offset <= end) {
725 frontswap_invalidate_page(si->type, offset);
726 if (swap_slot_free_notify)
727 swap_slot_free_notify(si->bdev, offset);
728 offset++;
729 }
730}
731
732static int scan_swap_map_slots(struct swap_info_struct *si,
733 unsigned char usage, int nr,
734 swp_entry_t slots[])
735{
736 struct swap_cluster_info *ci;
737 unsigned long offset;
738 unsigned long scan_base;
739 unsigned long last_in_cluster = 0;
740 int latency_ration = LATENCY_LIMIT;
741 int n_ret = 0;
742
743 if (nr > SWAP_BATCH)
744 nr = SWAP_BATCH;
745
746 /*
747 * We try to cluster swap pages by allocating them sequentially
748 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
749 * way, however, we resort to first-free allocation, starting
750 * a new cluster. This prevents us from scattering swap pages
751 * all over the entire swap partition, so that we reduce
752 * overall disk seek times between swap pages. -- sct
753 * But we do now try to find an empty cluster. -Andrea
754 * And we let swap pages go all over an SSD partition. Hugh
755 */
756
757 si->flags += SWP_SCANNING;
758 scan_base = offset = si->cluster_next;
759
760 /* SSD algorithm */
761 if (si->cluster_info) {
762 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
763 goto checks;
764 else
765 goto scan;
766 }
767
768 if (unlikely(!si->cluster_nr--)) {
769 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
770 si->cluster_nr = SWAPFILE_CLUSTER - 1;
771 goto checks;
772 }
773
774 spin_unlock(&si->lock);
775
776 /*
777 * If seek is expensive, start searching for new cluster from
778 * start of partition, to minimize the span of allocated swap.
779 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
780 * case, just handled by scan_swap_map_try_ssd_cluster() above.
781 */
782 scan_base = offset = si->lowest_bit;
783 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
784
785 /* Locate the first empty (unaligned) cluster */
786 for (; last_in_cluster <= si->highest_bit; offset++) {
787 if (si->swap_map[offset])
788 last_in_cluster = offset + SWAPFILE_CLUSTER;
789 else if (offset == last_in_cluster) {
790 spin_lock(&si->lock);
791 offset -= SWAPFILE_CLUSTER - 1;
792 si->cluster_next = offset;
793 si->cluster_nr = SWAPFILE_CLUSTER - 1;
794 goto checks;
795 }
796 if (unlikely(--latency_ration < 0)) {
797 cond_resched();
798 latency_ration = LATENCY_LIMIT;
799 }
800 }
801
802 offset = scan_base;
803 spin_lock(&si->lock);
804 si->cluster_nr = SWAPFILE_CLUSTER - 1;
805 }
806
807checks:
808 if (si->cluster_info) {
809 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
810 /* take a break if we already got some slots */
811 if (n_ret)
812 goto done;
813 if (!scan_swap_map_try_ssd_cluster(si, &offset,
814 &scan_base))
815 goto scan;
816 }
817 }
818 if (!(si->flags & SWP_WRITEOK))
819 goto no_page;
820 if (!si->highest_bit)
821 goto no_page;
822 if (offset > si->highest_bit)
823 scan_base = offset = si->lowest_bit;
824
825 ci = lock_cluster(si, offset);
826 /* reuse swap entry of cache-only swap if not busy. */
827 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
828 int swap_was_freed;
829 unlock_cluster(ci);
830 spin_unlock(&si->lock);
831 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
832 spin_lock(&si->lock);
833 /* entry was freed successfully, try to use this again */
834 if (swap_was_freed)
835 goto checks;
836 goto scan; /* check next one */
837 }
838
839 if (si->swap_map[offset]) {
840 unlock_cluster(ci);
841 if (!n_ret)
842 goto scan;
843 else
844 goto done;
845 }
846 si->swap_map[offset] = usage;
847 inc_cluster_info_page(si, si->cluster_info, offset);
848 unlock_cluster(ci);
849
850 swap_range_alloc(si, offset, 1);
851 si->cluster_next = offset + 1;
852 slots[n_ret++] = swp_entry(si->type, offset);
853
854 /* got enough slots or reach max slots? */
855 if ((n_ret == nr) || (offset >= si->highest_bit))
856 goto done;
857
858 /* search for next available slot */
859
860 /* time to take a break? */
861 if (unlikely(--latency_ration < 0)) {
862 if (n_ret)
863 goto done;
864 spin_unlock(&si->lock);
865 cond_resched();
866 spin_lock(&si->lock);
867 latency_ration = LATENCY_LIMIT;
868 }
869
870 /* try to get more slots in cluster */
871 if (si->cluster_info) {
872 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
873 goto checks;
874 else
875 goto done;
876 }
877 /* non-ssd case */
878 ++offset;
879
880 /* non-ssd case, still more slots in cluster? */
881 if (si->cluster_nr && !si->swap_map[offset]) {
882 --si->cluster_nr;
883 goto checks;
884 }
885
886done:
887 si->flags -= SWP_SCANNING;
888 return n_ret;
889
890scan:
891 spin_unlock(&si->lock);
892 while (++offset <= si->highest_bit) {
893 if (!si->swap_map[offset]) {
894 spin_lock(&si->lock);
895 goto checks;
896 }
897 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
898 spin_lock(&si->lock);
899 goto checks;
900 }
901 if (unlikely(--latency_ration < 0)) {
902 cond_resched();
903 latency_ration = LATENCY_LIMIT;
904 }
905 }
906 offset = si->lowest_bit;
907 while (offset < scan_base) {
908 if (!si->swap_map[offset]) {
909 spin_lock(&si->lock);
910 goto checks;
911 }
912 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
913 spin_lock(&si->lock);
914 goto checks;
915 }
916 if (unlikely(--latency_ration < 0)) {
917 cond_resched();
918 latency_ration = LATENCY_LIMIT;
919 }
920 offset++;
921 }
922 spin_lock(&si->lock);
923
924no_page:
925 si->flags -= SWP_SCANNING;
926 return n_ret;
927}
928
929static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
930{
931 unsigned long idx;
932 struct swap_cluster_info *ci;
933 unsigned long offset, i;
934 unsigned char *map;
935
936 /*
937 * Should not even be attempting cluster allocations when huge
938 * page swap is disabled. Warn and fail the allocation.
939 */
940 if (!IS_ENABLED(CONFIG_THP_SWAP)) {
941 VM_WARN_ON_ONCE(1);
942 return 0;
943 }
944
945 if (cluster_list_empty(&si->free_clusters))
946 return 0;
947
948 idx = cluster_list_first(&si->free_clusters);
949 offset = idx * SWAPFILE_CLUSTER;
950 ci = lock_cluster(si, offset);
951 alloc_cluster(si, idx);
952 cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
953
954 map = si->swap_map + offset;
955 for (i = 0; i < SWAPFILE_CLUSTER; i++)
956 map[i] = SWAP_HAS_CACHE;
957 unlock_cluster(ci);
958 swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
959 *slot = swp_entry(si->type, offset);
960
961 return 1;
962}
963
964static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
965{
966 unsigned long offset = idx * SWAPFILE_CLUSTER;
967 struct swap_cluster_info *ci;
968
969 ci = lock_cluster(si, offset);
970 memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
971 cluster_set_count_flag(ci, 0, 0);
972 free_cluster(si, idx);
973 unlock_cluster(ci);
974 swap_range_free(si, offset, SWAPFILE_CLUSTER);
975}
976
977static unsigned long scan_swap_map(struct swap_info_struct *si,
978 unsigned char usage)
979{
980 swp_entry_t entry;
981 int n_ret;
982
983 n_ret = scan_swap_map_slots(si, usage, 1, &entry);
984
985 if (n_ret)
986 return swp_offset(entry);
987 else
988 return 0;
989
990}
991
992int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
993{
994 unsigned long size = swap_entry_size(entry_size);
995 struct swap_info_struct *si, *next;
996 long avail_pgs;
997 int n_ret = 0;
998 int node;
999
1000 /* Only single cluster request supported */
1001 WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1002
1003 avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1004 if (avail_pgs <= 0)
1005 goto noswap;
1006
1007 if (n_goal > SWAP_BATCH)
1008 n_goal = SWAP_BATCH;
1009
1010 if (n_goal > avail_pgs)
1011 n_goal = avail_pgs;
1012
1013 atomic_long_sub(n_goal * size, &nr_swap_pages);
1014
1015 spin_lock(&swap_avail_lock);
1016
1017start_over:
1018 node = numa_node_id();
1019 plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
1020 /* requeue si to after same-priority siblings */
1021 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
1022 spin_unlock(&swap_avail_lock);
1023 spin_lock(&si->lock);
1024 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
1025 spin_lock(&swap_avail_lock);
1026 if (plist_node_empty(&si->avail_lists[node])) {
1027 spin_unlock(&si->lock);
1028 goto nextsi;
1029 }
1030 WARN(!si->highest_bit,
1031 "swap_info %d in list but !highest_bit\n",
1032 si->type);
1033 WARN(!(si->flags & SWP_WRITEOK),
1034 "swap_info %d in list but !SWP_WRITEOK\n",
1035 si->type);
1036 __del_from_avail_list(si);
1037 spin_unlock(&si->lock);
1038 goto nextsi;
1039 }
1040 if (size == SWAPFILE_CLUSTER) {
1041 if (!(si->flags & SWP_FS))
1042 n_ret = swap_alloc_cluster(si, swp_entries);
1043 } else
1044 n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1045 n_goal, swp_entries);
1046 spin_unlock(&si->lock);
1047 if (n_ret || size == SWAPFILE_CLUSTER)
1048 goto check_out;
1049 pr_debug("scan_swap_map of si %d failed to find offset\n",
1050 si->type);
1051
1052 spin_lock(&swap_avail_lock);
1053nextsi:
1054 /*
1055 * if we got here, it's likely that si was almost full before,
1056 * and since scan_swap_map() can drop the si->lock, multiple
1057 * callers probably all tried to get a page from the same si
1058 * and it filled up before we could get one; or, the si filled
1059 * up between us dropping swap_avail_lock and taking si->lock.
1060 * Since we dropped the swap_avail_lock, the swap_avail_head
1061 * list may have been modified; so if next is still in the
1062 * swap_avail_head list then try it, otherwise start over
1063 * if we have not gotten any slots.
1064 */
1065 if (plist_node_empty(&next->avail_lists[node]))
1066 goto start_over;
1067 }
1068
1069 spin_unlock(&swap_avail_lock);
1070
1071check_out:
1072 if (n_ret < n_goal)
1073 atomic_long_add((long)(n_goal - n_ret) * size,
1074 &nr_swap_pages);
1075noswap:
1076 return n_ret;
1077}
1078
1079/* The only caller of this function is now suspend routine */
1080swp_entry_t get_swap_page_of_type(int type)
1081{
1082 struct swap_info_struct *si = swap_type_to_swap_info(type);
1083 pgoff_t offset;
1084
1085 if (!si)
1086 goto fail;
1087
1088 spin_lock(&si->lock);
1089 if (si->flags & SWP_WRITEOK) {
1090 atomic_long_dec(&nr_swap_pages);
1091 /* This is called for allocating swap entry, not cache */
1092 offset = scan_swap_map(si, 1);
1093 if (offset) {
1094 spin_unlock(&si->lock);
1095 return swp_entry(type, offset);
1096 }
1097 atomic_long_inc(&nr_swap_pages);
1098 }
1099 spin_unlock(&si->lock);
1100fail:
1101 return (swp_entry_t) {0};
1102}
1103
1104static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
1105{
1106 struct swap_info_struct *p;
1107 unsigned long offset;
1108
1109 if (!entry.val)
1110 goto out;
1111 p = swp_swap_info(entry);
1112 if (!p)
1113 goto bad_nofile;
1114 if (!(p->flags & SWP_USED))
1115 goto bad_device;
1116 offset = swp_offset(entry);
1117 if (offset >= p->max)
1118 goto bad_offset;
1119 return p;
1120
1121bad_offset:
1122 pr_err("swap_info_get: %s%08lx\n", Bad_offset, entry.val);
1123 goto out;
1124bad_device:
1125 pr_err("swap_info_get: %s%08lx\n", Unused_file, entry.val);
1126 goto out;
1127bad_nofile:
1128 pr_err("swap_info_get: %s%08lx\n", Bad_file, entry.val);
1129out:
1130 return NULL;
1131}
1132
1133static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1134{
1135 struct swap_info_struct *p;
1136
1137 p = __swap_info_get(entry);
1138 if (!p)
1139 goto out;
1140 if (!p->swap_map[swp_offset(entry)])
1141 goto bad_free;
1142 return p;
1143
1144bad_free:
1145 pr_err("swap_info_get: %s%08lx\n", Unused_offset, entry.val);
1146 goto out;
1147out:
1148 return NULL;
1149}
1150
1151static struct swap_info_struct *swap_info_get(swp_entry_t entry)
1152{
1153 struct swap_info_struct *p;
1154
1155 p = _swap_info_get(entry);
1156 if (p)
1157 spin_lock(&p->lock);
1158 return p;
1159}
1160
1161static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1162 struct swap_info_struct *q)
1163{
1164 struct swap_info_struct *p;
1165
1166 p = _swap_info_get(entry);
1167
1168 if (p != q) {
1169 if (q != NULL)
1170 spin_unlock(&q->lock);
1171 if (p != NULL)
1172 spin_lock(&p->lock);
1173 }
1174 return p;
1175}
1176
1177static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1178 unsigned long offset,
1179 unsigned char usage)
1180{
1181 unsigned char count;
1182 unsigned char has_cache;
1183
1184 count = p->swap_map[offset];
1185
1186 has_cache = count & SWAP_HAS_CACHE;
1187 count &= ~SWAP_HAS_CACHE;
1188
1189 if (usage == SWAP_HAS_CACHE) {
1190 VM_BUG_ON(!has_cache);
1191 has_cache = 0;
1192 } else if (count == SWAP_MAP_SHMEM) {
1193 /*
1194 * Or we could insist on shmem.c using a special
1195 * swap_shmem_free() and free_shmem_swap_and_cache()...
1196 */
1197 count = 0;
1198 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1199 if (count == COUNT_CONTINUED) {
1200 if (swap_count_continued(p, offset, count))
1201 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1202 else
1203 count = SWAP_MAP_MAX;
1204 } else
1205 count--;
1206 }
1207
1208 usage = count | has_cache;
1209 p->swap_map[offset] = usage ? : SWAP_HAS_CACHE;
1210
1211 return usage;
1212}
1213
1214/*
1215 * Check whether swap entry is valid in the swap device. If so,
1216 * return pointer to swap_info_struct, and keep the swap entry valid
1217 * via preventing the swap device from being swapoff, until
1218 * put_swap_device() is called. Otherwise return NULL.
1219 *
1220 * The entirety of the RCU read critical section must come before the
1221 * return from or after the call to synchronize_rcu() in
1222 * enable_swap_info() or swapoff(). So if "si->flags & SWP_VALID" is
1223 * true, the si->map, si->cluster_info, etc. must be valid in the
1224 * critical section.
1225 *
1226 * Notice that swapoff or swapoff+swapon can still happen before the
1227 * rcu_read_lock() in get_swap_device() or after the rcu_read_unlock()
1228 * in put_swap_device() if there isn't any other way to prevent
1229 * swapoff, such as page lock, page table lock, etc. The caller must
1230 * be prepared for that. For example, the following situation is
1231 * possible.
1232 *
1233 * CPU1 CPU2
1234 * do_swap_page()
1235 * ... swapoff+swapon
1236 * __read_swap_cache_async()
1237 * swapcache_prepare()
1238 * __swap_duplicate()
1239 * // check swap_map
1240 * // verify PTE not changed
1241 *
1242 * In __swap_duplicate(), the swap_map need to be checked before
1243 * changing partly because the specified swap entry may be for another
1244 * swap device which has been swapoff. And in do_swap_page(), after
1245 * the page is read from the swap device, the PTE is verified not
1246 * changed with the page table locked to check whether the swap device
1247 * has been swapoff or swapoff+swapon.
1248 */
1249struct swap_info_struct *get_swap_device(swp_entry_t entry)
1250{
1251 struct swap_info_struct *si;
1252 unsigned long offset;
1253
1254 if (!entry.val)
1255 goto out;
1256 si = swp_swap_info(entry);
1257 if (!si)
1258 goto bad_nofile;
1259
1260 rcu_read_lock();
1261 if (!(si->flags & SWP_VALID))
1262 goto unlock_out;
1263 offset = swp_offset(entry);
1264 if (offset >= si->max)
1265 goto unlock_out;
1266
1267 return si;
1268bad_nofile:
1269 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1270out:
1271 return NULL;
1272unlock_out:
1273 rcu_read_unlock();
1274 return NULL;
1275}
1276
1277static unsigned char __swap_entry_free(struct swap_info_struct *p,
1278 swp_entry_t entry, unsigned char usage)
1279{
1280 struct swap_cluster_info *ci;
1281 unsigned long offset = swp_offset(entry);
1282
1283 ci = lock_cluster_or_swap_info(p, offset);
1284 usage = __swap_entry_free_locked(p, offset, usage);
1285 unlock_cluster_or_swap_info(p, ci);
1286 if (!usage)
1287 free_swap_slot(entry);
1288
1289 return usage;
1290}
1291
1292static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1293{
1294 struct swap_cluster_info *ci;
1295 unsigned long offset = swp_offset(entry);
1296 unsigned char count;
1297
1298 ci = lock_cluster(p, offset);
1299 count = p->swap_map[offset];
1300 VM_BUG_ON(count != SWAP_HAS_CACHE);
1301 p->swap_map[offset] = 0;
1302 dec_cluster_info_page(p, p->cluster_info, offset);
1303 unlock_cluster(ci);
1304
1305 mem_cgroup_uncharge_swap(entry, 1);
1306 swap_range_free(p, offset, 1);
1307}
1308
1309/*
1310 * Caller has made sure that the swap device corresponding to entry
1311 * is still around or has not been recycled.
1312 */
1313void swap_free(swp_entry_t entry)
1314{
1315 struct swap_info_struct *p;
1316
1317 p = _swap_info_get(entry);
1318 if (p)
1319 __swap_entry_free(p, entry, 1);
1320}
1321
1322/*
1323 * Called after dropping swapcache to decrease refcnt to swap entries.
1324 */
1325void put_swap_page(struct page *page, swp_entry_t entry)
1326{
1327 unsigned long offset = swp_offset(entry);
1328 unsigned long idx = offset / SWAPFILE_CLUSTER;
1329 struct swap_cluster_info *ci;
1330 struct swap_info_struct *si;
1331 unsigned char *map;
1332 unsigned int i, free_entries = 0;
1333 unsigned char val;
1334 int size = swap_entry_size(hpage_nr_pages(page));
1335
1336 si = _swap_info_get(entry);
1337 if (!si)
1338 return;
1339
1340 ci = lock_cluster_or_swap_info(si, offset);
1341 if (size == SWAPFILE_CLUSTER) {
1342 VM_BUG_ON(!cluster_is_huge(ci));
1343 map = si->swap_map + offset;
1344 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1345 val = map[i];
1346 VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1347 if (val == SWAP_HAS_CACHE)
1348 free_entries++;
1349 }
1350 cluster_clear_huge(ci);
1351 if (free_entries == SWAPFILE_CLUSTER) {
1352 unlock_cluster_or_swap_info(si, ci);
1353 spin_lock(&si->lock);
1354 mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1355 swap_free_cluster(si, idx);
1356 spin_unlock(&si->lock);
1357 return;
1358 }
1359 }
1360 for (i = 0; i < size; i++, entry.val++) {
1361 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1362 unlock_cluster_or_swap_info(si, ci);
1363 free_swap_slot(entry);
1364 if (i == size - 1)
1365 return;
1366 lock_cluster_or_swap_info(si, offset);
1367 }
1368 }
1369 unlock_cluster_or_swap_info(si, ci);
1370}
1371
1372#ifdef CONFIG_THP_SWAP
1373int split_swap_cluster(swp_entry_t entry)
1374{
1375 struct swap_info_struct *si;
1376 struct swap_cluster_info *ci;
1377 unsigned long offset = swp_offset(entry);
1378
1379 si = _swap_info_get(entry);
1380 if (!si)
1381 return -EBUSY;
1382 ci = lock_cluster(si, offset);
1383 cluster_clear_huge(ci);
1384 unlock_cluster(ci);
1385 return 0;
1386}
1387#endif
1388
1389static int swp_entry_cmp(const void *ent1, const void *ent2)
1390{
1391 const swp_entry_t *e1 = ent1, *e2 = ent2;
1392
1393 return (int)swp_type(*e1) - (int)swp_type(*e2);
1394}
1395
1396void swapcache_free_entries(swp_entry_t *entries, int n)
1397{
1398 struct swap_info_struct *p, *prev;
1399 int i;
1400
1401 if (n <= 0)
1402 return;
1403
1404 prev = NULL;
1405 p = NULL;
1406
1407 /*
1408 * Sort swap entries by swap device, so each lock is only taken once.
1409 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1410 * so low that it isn't necessary to optimize further.
1411 */
1412 if (nr_swapfiles > 1)
1413 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1414 for (i = 0; i < n; ++i) {
1415 p = swap_info_get_cont(entries[i], prev);
1416 if (p)
1417 swap_entry_free(p, entries[i]);
1418 prev = p;
1419 }
1420 if (p)
1421 spin_unlock(&p->lock);
1422}
1423
1424/*
1425 * How many references to page are currently swapped out?
1426 * This does not give an exact answer when swap count is continued,
1427 * but does include the high COUNT_CONTINUED flag to allow for that.
1428 */
1429int page_swapcount(struct page *page)
1430{
1431 int count = 0;
1432 struct swap_info_struct *p;
1433 struct swap_cluster_info *ci;
1434 swp_entry_t entry;
1435 unsigned long offset;
1436
1437 entry.val = page_private(page);
1438 p = _swap_info_get(entry);
1439 if (p) {
1440 offset = swp_offset(entry);
1441 ci = lock_cluster_or_swap_info(p, offset);
1442 count = swap_count(p->swap_map[offset]);
1443 unlock_cluster_or_swap_info(p, ci);
1444 }
1445 return count;
1446}
1447
1448int __swap_count(swp_entry_t entry)
1449{
1450 struct swap_info_struct *si;
1451 pgoff_t offset = swp_offset(entry);
1452 int count = 0;
1453
1454 si = get_swap_device(entry);
1455 if (si) {
1456 count = swap_count(si->swap_map[offset]);
1457 put_swap_device(si);
1458 }
1459 return count;
1460}
1461
1462static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1463{
1464 int count = 0;
1465 pgoff_t offset = swp_offset(entry);
1466 struct swap_cluster_info *ci;
1467
1468 ci = lock_cluster_or_swap_info(si, offset);
1469 count = swap_count(si->swap_map[offset]);
1470 unlock_cluster_or_swap_info(si, ci);
1471 return count;
1472}
1473
1474/*
1475 * How many references to @entry are currently swapped out?
1476 * This does not give an exact answer when swap count is continued,
1477 * but does include the high COUNT_CONTINUED flag to allow for that.
1478 */
1479int __swp_swapcount(swp_entry_t entry)
1480{
1481 int count = 0;
1482 struct swap_info_struct *si;
1483
1484 si = get_swap_device(entry);
1485 if (si) {
1486 count = swap_swapcount(si, entry);
1487 put_swap_device(si);
1488 }
1489 return count;
1490}
1491
1492/*
1493 * How many references to @entry are currently swapped out?
1494 * This considers COUNT_CONTINUED so it returns exact answer.
1495 */
1496int swp_swapcount(swp_entry_t entry)
1497{
1498 int count, tmp_count, n;
1499 struct swap_info_struct *p;
1500 struct swap_cluster_info *ci;
1501 struct page *page;
1502 pgoff_t offset;
1503 unsigned char *map;
1504
1505 p = _swap_info_get(entry);
1506 if (!p)
1507 return 0;
1508
1509 offset = swp_offset(entry);
1510
1511 ci = lock_cluster_or_swap_info(p, offset);
1512
1513 count = swap_count(p->swap_map[offset]);
1514 if (!(count & COUNT_CONTINUED))
1515 goto out;
1516
1517 count &= ~COUNT_CONTINUED;
1518 n = SWAP_MAP_MAX + 1;
1519
1520 page = vmalloc_to_page(p->swap_map + offset);
1521 offset &= ~PAGE_MASK;
1522 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1523
1524 do {
1525 page = list_next_entry(page, lru);
1526 map = kmap_atomic(page);
1527 tmp_count = map[offset];
1528 kunmap_atomic(map);
1529
1530 count += (tmp_count & ~COUNT_CONTINUED) * n;
1531 n *= (SWAP_CONT_MAX + 1);
1532 } while (tmp_count & COUNT_CONTINUED);
1533out:
1534 unlock_cluster_or_swap_info(p, ci);
1535 return count;
1536}
1537
1538static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1539 swp_entry_t entry)
1540{
1541 struct swap_cluster_info *ci;
1542 unsigned char *map = si->swap_map;
1543 unsigned long roffset = swp_offset(entry);
1544 unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1545 int i;
1546 bool ret = false;
1547
1548 ci = lock_cluster_or_swap_info(si, offset);
1549 if (!ci || !cluster_is_huge(ci)) {
1550 if (swap_count(map[roffset]))
1551 ret = true;
1552 goto unlock_out;
1553 }
1554 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1555 if (swap_count(map[offset + i])) {
1556 ret = true;
1557 break;
1558 }
1559 }
1560unlock_out:
1561 unlock_cluster_or_swap_info(si, ci);
1562 return ret;
1563}
1564
1565static bool page_swapped(struct page *page)
1566{
1567 swp_entry_t entry;
1568 struct swap_info_struct *si;
1569
1570 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
1571 return page_swapcount(page) != 0;
1572
1573 page = compound_head(page);
1574 entry.val = page_private(page);
1575 si = _swap_info_get(entry);
1576 if (si)
1577 return swap_page_trans_huge_swapped(si, entry);
1578 return false;
1579}
1580
1581static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
1582 int *total_swapcount)
1583{
1584 int i, map_swapcount, _total_mapcount, _total_swapcount;
1585 unsigned long offset = 0;
1586 struct swap_info_struct *si;
1587 struct swap_cluster_info *ci = NULL;
1588 unsigned char *map = NULL;
1589 int mapcount, swapcount = 0;
1590
1591 /* hugetlbfs shouldn't call it */
1592 VM_BUG_ON_PAGE(PageHuge(page), page);
1593
1594 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {
1595 mapcount = page_trans_huge_mapcount(page, total_mapcount);
1596 if (PageSwapCache(page))
1597 swapcount = page_swapcount(page);
1598 if (total_swapcount)
1599 *total_swapcount = swapcount;
1600 return mapcount + swapcount;
1601 }
1602
1603 page = compound_head(page);
1604
1605 _total_mapcount = _total_swapcount = map_swapcount = 0;
1606 if (PageSwapCache(page)) {
1607 swp_entry_t entry;
1608
1609 entry.val = page_private(page);
1610 si = _swap_info_get(entry);
1611 if (si) {
1612 map = si->swap_map;
1613 offset = swp_offset(entry);
1614 }
1615 }
1616 if (map)
1617 ci = lock_cluster(si, offset);
1618 for (i = 0; i < HPAGE_PMD_NR; i++) {
1619 mapcount = atomic_read(&page[i]._mapcount) + 1;
1620 _total_mapcount += mapcount;
1621 if (map) {
1622 swapcount = swap_count(map[offset + i]);
1623 _total_swapcount += swapcount;
1624 }
1625 map_swapcount = max(map_swapcount, mapcount + swapcount);
1626 }
1627 unlock_cluster(ci);
1628 if (PageDoubleMap(page)) {
1629 map_swapcount -= 1;
1630 _total_mapcount -= HPAGE_PMD_NR;
1631 }
1632 mapcount = compound_mapcount(page);
1633 map_swapcount += mapcount;
1634 _total_mapcount += mapcount;
1635 if (total_mapcount)
1636 *total_mapcount = _total_mapcount;
1637 if (total_swapcount)
1638 *total_swapcount = _total_swapcount;
1639
1640 return map_swapcount;
1641}
1642
1643/*
1644 * We can write to an anon page without COW if there are no other references
1645 * to it. And as a side-effect, free up its swap: because the old content
1646 * on disk will never be read, and seeking back there to write new content
1647 * later would only waste time away from clustering.
1648 *
1649 * NOTE: total_map_swapcount should not be relied upon by the caller if
1650 * reuse_swap_page() returns false, but it may be always overwritten
1651 * (see the other implementation for CONFIG_SWAP=n).
1652 */
1653bool reuse_swap_page(struct page *page, int *total_map_swapcount)
1654{
1655 int count, total_mapcount, total_swapcount;
1656
1657 VM_BUG_ON_PAGE(!PageLocked(page), page);
1658 if (unlikely(PageKsm(page)))
1659 return false;
1660 count = page_trans_huge_map_swapcount(page, &total_mapcount,
1661 &total_swapcount);
1662 if (total_map_swapcount)
1663 *total_map_swapcount = total_mapcount + total_swapcount;
1664 if (count == 1 && PageSwapCache(page) &&
1665 (likely(!PageTransCompound(page)) ||
1666 /* The remaining swap count will be freed soon */
1667 total_swapcount == page_swapcount(page))) {
1668 if (!PageWriteback(page)) {
1669 page = compound_head(page);
1670 delete_from_swap_cache(page);
1671 SetPageDirty(page);
1672 } else {
1673 swp_entry_t entry;
1674 struct swap_info_struct *p;
1675
1676 entry.val = page_private(page);
1677 p = swap_info_get(entry);
1678 if (p->flags & SWP_STABLE_WRITES) {
1679 spin_unlock(&p->lock);
1680 return false;
1681 }
1682 spin_unlock(&p->lock);
1683 }
1684 }
1685
1686 return count <= 1;
1687}
1688
1689/*
1690 * If swap is getting full, or if there are no more mappings of this page,
1691 * then try_to_free_swap is called to free its swap space.
1692 */
1693int try_to_free_swap(struct page *page)
1694{
1695 VM_BUG_ON_PAGE(!PageLocked(page), page);
1696
1697 if (!PageSwapCache(page))
1698 return 0;
1699 if (PageWriteback(page))
1700 return 0;
1701 if (page_swapped(page))
1702 return 0;
1703
1704 /*
1705 * Once hibernation has begun to create its image of memory,
1706 * there's a danger that one of the calls to try_to_free_swap()
1707 * - most probably a call from __try_to_reclaim_swap() while
1708 * hibernation is allocating its own swap pages for the image,
1709 * but conceivably even a call from memory reclaim - will free
1710 * the swap from a page which has already been recorded in the
1711 * image as a clean swapcache page, and then reuse its swap for
1712 * another page of the image. On waking from hibernation, the
1713 * original page might be freed under memory pressure, then
1714 * later read back in from swap, now with the wrong data.
1715 *
1716 * Hibernation suspends storage while it is writing the image
1717 * to disk so check that here.
1718 */
1719 if (pm_suspended_storage())
1720 return 0;
1721
1722 page = compound_head(page);
1723 delete_from_swap_cache(page);
1724 SetPageDirty(page);
1725 return 1;
1726}
1727
1728/*
1729 * Free the swap entry like above, but also try to
1730 * free the page cache entry if it is the last user.
1731 */
1732int free_swap_and_cache(swp_entry_t entry)
1733{
1734 struct swap_info_struct *p;
1735 unsigned char count;
1736
1737 if (non_swap_entry(entry))
1738 return 1;
1739
1740 p = _swap_info_get(entry);
1741 if (p) {
1742 count = __swap_entry_free(p, entry, 1);
1743 if (count == SWAP_HAS_CACHE &&
1744 !swap_page_trans_huge_swapped(p, entry))
1745 __try_to_reclaim_swap(p, swp_offset(entry),
1746 TTRS_UNMAPPED | TTRS_FULL);
1747 }
1748 return p != NULL;
1749}
1750
1751#ifdef CONFIG_HIBERNATION
1752/*
1753 * Find the swap type that corresponds to given device (if any).
1754 *
1755 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1756 * from 0, in which the swap header is expected to be located.
1757 *
1758 * This is needed for the suspend to disk (aka swsusp).
1759 */
1760int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
1761{
1762 struct block_device *bdev = NULL;
1763 int type;
1764
1765 if (device)
1766 bdev = bdget(device);
1767
1768 spin_lock(&swap_lock);
1769 for (type = 0; type < nr_swapfiles; type++) {
1770 struct swap_info_struct *sis = swap_info[type];
1771
1772 if (!(sis->flags & SWP_WRITEOK))
1773 continue;
1774
1775 if (!bdev) {
1776 if (bdev_p)
1777 *bdev_p = bdgrab(sis->bdev);
1778
1779 spin_unlock(&swap_lock);
1780 return type;
1781 }
1782 if (bdev == sis->bdev) {
1783 struct swap_extent *se = first_se(sis);
1784
1785 if (se->start_block == offset) {
1786 if (bdev_p)
1787 *bdev_p = bdgrab(sis->bdev);
1788
1789 spin_unlock(&swap_lock);
1790 bdput(bdev);
1791 return type;
1792 }
1793 }
1794 }
1795 spin_unlock(&swap_lock);
1796 if (bdev)
1797 bdput(bdev);
1798
1799 return -ENODEV;
1800}
1801
1802/*
1803 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1804 * corresponding to given index in swap_info (swap type).
1805 */
1806sector_t swapdev_block(int type, pgoff_t offset)
1807{
1808 struct block_device *bdev;
1809 struct swap_info_struct *si = swap_type_to_swap_info(type);
1810
1811 if (!si || !(si->flags & SWP_WRITEOK))
1812 return 0;
1813 return map_swap_entry(swp_entry(type, offset), &bdev);
1814}
1815
1816/*
1817 * Return either the total number of swap pages of given type, or the number
1818 * of free pages of that type (depending on @free)
1819 *
1820 * This is needed for software suspend
1821 */
1822unsigned int count_swap_pages(int type, int free)
1823{
1824 unsigned int n = 0;
1825
1826 spin_lock(&swap_lock);
1827 if ((unsigned int)type < nr_swapfiles) {
1828 struct swap_info_struct *sis = swap_info[type];
1829
1830 spin_lock(&sis->lock);
1831 if (sis->flags & SWP_WRITEOK) {
1832 n = sis->pages;
1833 if (free)
1834 n -= sis->inuse_pages;
1835 }
1836 spin_unlock(&sis->lock);
1837 }
1838 spin_unlock(&swap_lock);
1839 return n;
1840}
1841#endif /* CONFIG_HIBERNATION */
1842
1843static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1844{
1845 return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte);
1846}
1847
1848/*
1849 * No need to decide whether this PTE shares the swap entry with others,
1850 * just let do_wp_page work it out if a write is requested later - to
1851 * force COW, vm_page_prot omits write permission from any private vma.
1852 */
1853static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1854 unsigned long addr, swp_entry_t entry, struct page *page)
1855{
1856 struct page *swapcache;
1857 struct mem_cgroup *memcg;
1858 spinlock_t *ptl;
1859 pte_t *pte;
1860 int ret = 1;
1861
1862 swapcache = page;
1863 page = ksm_might_need_to_copy(page, vma, addr);
1864 if (unlikely(!page))
1865 return -ENOMEM;
1866
1867 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL,
1868 &memcg, false)) {
1869 ret = -ENOMEM;
1870 goto out_nolock;
1871 }
1872
1873 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1874 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1875 mem_cgroup_cancel_charge(page, memcg, false);
1876 ret = 0;
1877 goto out;
1878 }
1879
1880 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1881 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1882 get_page(page);
1883 set_pte_at(vma->vm_mm, addr, pte,
1884 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1885 if (page == swapcache) {
1886 page_add_anon_rmap(page, vma, addr, false);
1887 mem_cgroup_commit_charge(page, memcg, true, false);
1888 } else { /* ksm created a completely new copy */
1889 page_add_new_anon_rmap(page, vma, addr, false);
1890 mem_cgroup_commit_charge(page, memcg, false, false);
1891 lru_cache_add_active_or_unevictable(page, vma);
1892 }
1893 swap_free(entry);
1894 /*
1895 * Move the page to the active list so it is not
1896 * immediately swapped out again after swapon.
1897 */
1898 activate_page(page);
1899out:
1900 pte_unmap_unlock(pte, ptl);
1901out_nolock:
1902 if (page != swapcache) {
1903 unlock_page(page);
1904 put_page(page);
1905 }
1906 return ret;
1907}
1908
1909static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1910 unsigned long addr, unsigned long end,
1911 unsigned int type, bool frontswap,
1912 unsigned long *fs_pages_to_unuse)
1913{
1914 struct page *page;
1915 swp_entry_t entry;
1916 pte_t *pte;
1917 struct swap_info_struct *si;
1918 unsigned long offset;
1919 int ret = 0;
1920 volatile unsigned char *swap_map;
1921
1922 si = swap_info[type];
1923 pte = pte_offset_map(pmd, addr);
1924 do {
1925 struct vm_fault vmf;
1926
1927 if (!is_swap_pte(*pte))
1928 continue;
1929
1930 entry = pte_to_swp_entry(*pte);
1931 if (swp_type(entry) != type)
1932 continue;
1933
1934 offset = swp_offset(entry);
1935 if (frontswap && !frontswap_test(si, offset))
1936 continue;
1937
1938 pte_unmap(pte);
1939 swap_map = &si->swap_map[offset];
1940 vmf.vma = vma;
1941 vmf.address = addr;
1942 vmf.pmd = pmd;
1943 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, &vmf);
1944 if (!page) {
1945 if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1946 goto try_next;
1947 return -ENOMEM;
1948 }
1949
1950 lock_page(page);
1951 wait_on_page_writeback(page);
1952 ret = unuse_pte(vma, pmd, addr, entry, page);
1953 if (ret < 0) {
1954 unlock_page(page);
1955 put_page(page);
1956 goto out;
1957 }
1958
1959 try_to_free_swap(page);
1960 unlock_page(page);
1961 put_page(page);
1962
1963 if (*fs_pages_to_unuse && !--(*fs_pages_to_unuse)) {
1964 ret = FRONTSWAP_PAGES_UNUSED;
1965 goto out;
1966 }
1967try_next:
1968 pte = pte_offset_map(pmd, addr);
1969 } while (pte++, addr += PAGE_SIZE, addr != end);
1970 pte_unmap(pte - 1);
1971
1972 ret = 0;
1973out:
1974 return ret;
1975}
1976
1977static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1978 unsigned long addr, unsigned long end,
1979 unsigned int type, bool frontswap,
1980 unsigned long *fs_pages_to_unuse)
1981{
1982 pmd_t *pmd;
1983 unsigned long next;
1984 int ret;
1985
1986 pmd = pmd_offset(pud, addr);
1987 do {
1988 cond_resched();
1989 next = pmd_addr_end(addr, end);
1990 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1991 continue;
1992 ret = unuse_pte_range(vma, pmd, addr, next, type,
1993 frontswap, fs_pages_to_unuse);
1994 if (ret)
1995 return ret;
1996 } while (pmd++, addr = next, addr != end);
1997 return 0;
1998}
1999
2000static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
2001 unsigned long addr, unsigned long end,
2002 unsigned int type, bool frontswap,
2003 unsigned long *fs_pages_to_unuse)
2004{
2005 pud_t *pud;
2006 unsigned long next;
2007 int ret;
2008
2009 pud = pud_offset(p4d, addr);
2010 do {
2011 next = pud_addr_end(addr, end);
2012 if (pud_none_or_clear_bad(pud))
2013 continue;
2014 ret = unuse_pmd_range(vma, pud, addr, next, type,
2015 frontswap, fs_pages_to_unuse);
2016 if (ret)
2017 return ret;
2018 } while (pud++, addr = next, addr != end);
2019 return 0;
2020}
2021
2022static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
2023 unsigned long addr, unsigned long end,
2024 unsigned int type, bool frontswap,
2025 unsigned long *fs_pages_to_unuse)
2026{
2027 p4d_t *p4d;
2028 unsigned long next;
2029 int ret;
2030
2031 p4d = p4d_offset(pgd, addr);
2032 do {
2033 next = p4d_addr_end(addr, end);
2034 if (p4d_none_or_clear_bad(p4d))
2035 continue;
2036 ret = unuse_pud_range(vma, p4d, addr, next, type,
2037 frontswap, fs_pages_to_unuse);
2038 if (ret)
2039 return ret;
2040 } while (p4d++, addr = next, addr != end);
2041 return 0;
2042}
2043
2044static int unuse_vma(struct vm_area_struct *vma, unsigned int type,
2045 bool frontswap, unsigned long *fs_pages_to_unuse)
2046{
2047 pgd_t *pgd;
2048 unsigned long addr, end, next;
2049 int ret;
2050
2051 addr = vma->vm_start;
2052 end = vma->vm_end;
2053
2054 pgd = pgd_offset(vma->vm_mm, addr);
2055 do {
2056 next = pgd_addr_end(addr, end);
2057 if (pgd_none_or_clear_bad(pgd))
2058 continue;
2059 ret = unuse_p4d_range(vma, pgd, addr, next, type,
2060 frontswap, fs_pages_to_unuse);
2061 if (ret)
2062 return ret;
2063 } while (pgd++, addr = next, addr != end);
2064 return 0;
2065}
2066
2067static int unuse_mm(struct mm_struct *mm, unsigned int type,
2068 bool frontswap, unsigned long *fs_pages_to_unuse)
2069{
2070 struct vm_area_struct *vma;
2071 int ret = 0;
2072
2073 down_read(&mm->mmap_sem);
2074 for (vma = mm->mmap; vma; vma = vma->vm_next) {
2075 if (vma->anon_vma) {
2076 ret = unuse_vma(vma, type, frontswap,
2077 fs_pages_to_unuse);
2078 if (ret)
2079 break;
2080 }
2081 cond_resched();
2082 }
2083 up_read(&mm->mmap_sem);
2084 return ret;
2085}
2086
2087/*
2088 * Scan swap_map (or frontswap_map if frontswap parameter is true)
2089 * from current position to next entry still in use. Return 0
2090 * if there are no inuse entries after prev till end of the map.
2091 */
2092static unsigned int find_next_to_unuse(struct swap_info_struct *si,
2093 unsigned int prev, bool frontswap)
2094{
2095 unsigned int i;
2096 unsigned char count;
2097
2098 /*
2099 * No need for swap_lock here: we're just looking
2100 * for whether an entry is in use, not modifying it; false
2101 * hits are okay, and sys_swapoff() has already prevented new
2102 * allocations from this area (while holding swap_lock).
2103 */
2104 for (i = prev + 1; i < si->max; i++) {
2105 count = READ_ONCE(si->swap_map[i]);
2106 if (count && swap_count(count) != SWAP_MAP_BAD)
2107 if (!frontswap || frontswap_test(si, i))
2108 break;
2109 if ((i % LATENCY_LIMIT) == 0)
2110 cond_resched();
2111 }
2112
2113 if (i == si->max)
2114 i = 0;
2115
2116 return i;
2117}
2118
2119/*
2120 * If the boolean frontswap is true, only unuse pages_to_unuse pages;
2121 * pages_to_unuse==0 means all pages; ignored if frontswap is false
2122 */
2123int try_to_unuse(unsigned int type, bool frontswap,
2124 unsigned long pages_to_unuse)
2125{
2126 struct mm_struct *prev_mm;
2127 struct mm_struct *mm;
2128 struct list_head *p;
2129 int retval = 0;
2130 struct swap_info_struct *si = swap_info[type];
2131 struct page *page;
2132 swp_entry_t entry;
2133 unsigned int i;
2134
2135 if (!si->inuse_pages)
2136 return 0;
2137
2138 if (!frontswap)
2139 pages_to_unuse = 0;
2140
2141retry:
2142 retval = shmem_unuse(type, frontswap, &pages_to_unuse);
2143 if (retval)
2144 goto out;
2145
2146 prev_mm = &init_mm;
2147 mmget(prev_mm);
2148
2149 spin_lock(&mmlist_lock);
2150 p = &init_mm.mmlist;
2151 while (si->inuse_pages &&
2152 !signal_pending(current) &&
2153 (p = p->next) != &init_mm.mmlist) {
2154
2155 mm = list_entry(p, struct mm_struct, mmlist);
2156 if (!mmget_not_zero(mm))
2157 continue;
2158 spin_unlock(&mmlist_lock);
2159 mmput(prev_mm);
2160 prev_mm = mm;
2161 retval = unuse_mm(mm, type, frontswap, &pages_to_unuse);
2162
2163 if (retval) {
2164 mmput(prev_mm);
2165 goto out;
2166 }
2167
2168 /*
2169 * Make sure that we aren't completely killing
2170 * interactive performance.
2171 */
2172 cond_resched();
2173 spin_lock(&mmlist_lock);
2174 }
2175 spin_unlock(&mmlist_lock);
2176
2177 mmput(prev_mm);
2178
2179 i = 0;
2180 while (si->inuse_pages &&
2181 !signal_pending(current) &&
2182 (i = find_next_to_unuse(si, i, frontswap)) != 0) {
2183
2184 entry = swp_entry(type, i);
2185 page = find_get_page(swap_address_space(entry), i);
2186 if (!page)
2187 continue;
2188
2189 /*
2190 * It is conceivable that a racing task removed this page from
2191 * swap cache just before we acquired the page lock. The page
2192 * might even be back in swap cache on another swap area. But
2193 * that is okay, try_to_free_swap() only removes stale pages.
2194 */
2195 lock_page(page);
2196 wait_on_page_writeback(page);
2197 try_to_free_swap(page);
2198 unlock_page(page);
2199 put_page(page);
2200
2201 /*
2202 * For frontswap, we just need to unuse pages_to_unuse, if
2203 * it was specified. Need not check frontswap again here as
2204 * we already zeroed out pages_to_unuse if not frontswap.
2205 */
2206 if (pages_to_unuse && --pages_to_unuse == 0)
2207 goto out;
2208 }
2209
2210 /*
2211 * Lets check again to see if there are still swap entries in the map.
2212 * If yes, we would need to do retry the unuse logic again.
2213 * Under global memory pressure, swap entries can be reinserted back
2214 * into process space after the mmlist loop above passes over them.
2215 *
2216 * Limit the number of retries? No: when mmget_not_zero() above fails,
2217 * that mm is likely to be freeing swap from exit_mmap(), which proceeds
2218 * at its own independent pace; and even shmem_writepage() could have
2219 * been preempted after get_swap_page(), temporarily hiding that swap.
2220 * It's easy and robust (though cpu-intensive) just to keep retrying.
2221 */
2222 if (si->inuse_pages) {
2223 if (!signal_pending(current))
2224 goto retry;
2225 retval = -EINTR;
2226 }
2227out:
2228 return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
2229}
2230
2231/*
2232 * After a successful try_to_unuse, if no swap is now in use, we know
2233 * we can empty the mmlist. swap_lock must be held on entry and exit.
2234 * Note that mmlist_lock nests inside swap_lock, and an mm must be
2235 * added to the mmlist just after page_duplicate - before would be racy.
2236 */
2237static void drain_mmlist(void)
2238{
2239 struct list_head *p, *next;
2240 unsigned int type;
2241
2242 for (type = 0; type < nr_swapfiles; type++)
2243 if (swap_info[type]->inuse_pages)
2244 return;
2245 spin_lock(&mmlist_lock);
2246 list_for_each_safe(p, next, &init_mm.mmlist)
2247 list_del_init(p);
2248 spin_unlock(&mmlist_lock);
2249}
2250
2251/*
2252 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
2253 * corresponds to page offset for the specified swap entry.
2254 * Note that the type of this function is sector_t, but it returns page offset
2255 * into the bdev, not sector offset.
2256 */
2257static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
2258{
2259 struct swap_info_struct *sis;
2260 struct swap_extent *se;
2261 pgoff_t offset;
2262
2263 sis = swp_swap_info(entry);
2264 *bdev = sis->bdev;
2265
2266 offset = swp_offset(entry);
2267 se = offset_to_swap_extent(sis, offset);
2268 return se->start_block + (offset - se->start_page);
2269}
2270
2271/*
2272 * Returns the page offset into bdev for the specified page's swap entry.
2273 */
2274sector_t map_swap_page(struct page *page, struct block_device **bdev)
2275{
2276 swp_entry_t entry;
2277 entry.val = page_private(page);
2278 return map_swap_entry(entry, bdev);
2279}
2280
2281/*
2282 * Free all of a swapdev's extent information
2283 */
2284static void destroy_swap_extents(struct swap_info_struct *sis)
2285{
2286 while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2287 struct rb_node *rb = sis->swap_extent_root.rb_node;
2288 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2289
2290 rb_erase(rb, &sis->swap_extent_root);
2291 kfree(se);
2292 }
2293
2294 if (sis->flags & SWP_ACTIVATED) {
2295 struct file *swap_file = sis->swap_file;
2296 struct address_space *mapping = swap_file->f_mapping;
2297
2298 sis->flags &= ~SWP_ACTIVATED;
2299 if (mapping->a_ops->swap_deactivate)
2300 mapping->a_ops->swap_deactivate(swap_file);
2301 }
2302}
2303
2304/*
2305 * Add a block range (and the corresponding page range) into this swapdev's
2306 * extent tree.
2307 *
2308 * This function rather assumes that it is called in ascending page order.
2309 */
2310int
2311add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2312 unsigned long nr_pages, sector_t start_block)
2313{
2314 struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2315 struct swap_extent *se;
2316 struct swap_extent *new_se;
2317
2318 /*
2319 * place the new node at the right most since the
2320 * function is called in ascending page order.
2321 */
2322 while (*link) {
2323 parent = *link;
2324 link = &parent->rb_right;
2325 }
2326
2327 if (parent) {
2328 se = rb_entry(parent, struct swap_extent, rb_node);
2329 BUG_ON(se->start_page + se->nr_pages != start_page);
2330 if (se->start_block + se->nr_pages == start_block) {
2331 /* Merge it */
2332 se->nr_pages += nr_pages;
2333 return 0;
2334 }
2335 }
2336
2337 /* No merge, insert a new extent. */
2338 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2339 if (new_se == NULL)
2340 return -ENOMEM;
2341 new_se->start_page = start_page;
2342 new_se->nr_pages = nr_pages;
2343 new_se->start_block = start_block;
2344
2345 rb_link_node(&new_se->rb_node, parent, link);
2346 rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2347 return 1;
2348}
2349EXPORT_SYMBOL_GPL(add_swap_extent);
2350
2351/*
2352 * A `swap extent' is a simple thing which maps a contiguous range of pages
2353 * onto a contiguous range of disk blocks. An ordered list of swap extents
2354 * is built at swapon time and is then used at swap_writepage/swap_readpage
2355 * time for locating where on disk a page belongs.
2356 *
2357 * If the swapfile is an S_ISBLK block device, a single extent is installed.
2358 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2359 * swap files identically.
2360 *
2361 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2362 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
2363 * swapfiles are handled *identically* after swapon time.
2364 *
2365 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2366 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
2367 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
2368 * requirements, they are simply tossed out - we will never use those blocks
2369 * for swapping.
2370 *
2371 * For all swap devices we set S_SWAPFILE across the life of the swapon. This
2372 * prevents users from writing to the swap device, which will corrupt memory.
2373 *
2374 * The amount of disk space which a single swap extent represents varies.
2375 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
2376 * extents in the list. To avoid much list walking, we cache the previous
2377 * search location in `curr_swap_extent', and start new searches from there.
2378 * This is extremely effective. The average number of iterations in
2379 * map_swap_page() has been measured at about 0.3 per page. - akpm.
2380 */
2381static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2382{
2383 struct file *swap_file = sis->swap_file;
2384 struct address_space *mapping = swap_file->f_mapping;
2385 struct inode *inode = mapping->host;
2386 int ret;
2387
2388 if (S_ISBLK(inode->i_mode)) {
2389 ret = add_swap_extent(sis, 0, sis->max, 0);
2390 *span = sis->pages;
2391 return ret;
2392 }
2393
2394 if (mapping->a_ops->swap_activate) {
2395 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2396 if (ret >= 0)
2397 sis->flags |= SWP_ACTIVATED;
2398 if (!ret) {
2399 sis->flags |= SWP_FS;
2400 ret = add_swap_extent(sis, 0, sis->max, 0);
2401 *span = sis->pages;
2402 }
2403 return ret;
2404 }
2405
2406 return generic_swapfile_activate(sis, swap_file, span);
2407}
2408
2409static int swap_node(struct swap_info_struct *p)
2410{
2411 struct block_device *bdev;
2412
2413 if (p->bdev)
2414 bdev = p->bdev;
2415 else
2416 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2417
2418 return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2419}
2420
2421static void setup_swap_info(struct swap_info_struct *p, int prio,
2422 unsigned char *swap_map,
2423 struct swap_cluster_info *cluster_info)
2424{
2425 int i;
2426
2427 if (prio >= 0)
2428 p->prio = prio;
2429 else
2430 p->prio = --least_priority;
2431 /*
2432 * the plist prio is negated because plist ordering is
2433 * low-to-high, while swap ordering is high-to-low
2434 */
2435 p->list.prio = -p->prio;
2436 for_each_node(i) {
2437 if (p->prio >= 0)
2438 p->avail_lists[i].prio = -p->prio;
2439 else {
2440 if (swap_node(p) == i)
2441 p->avail_lists[i].prio = 1;
2442 else
2443 p->avail_lists[i].prio = -p->prio;
2444 }
2445 }
2446 p->swap_map = swap_map;
2447 p->cluster_info = cluster_info;
2448}
2449
2450static void _enable_swap_info(struct swap_info_struct *p)
2451{
2452 p->flags |= SWP_WRITEOK | SWP_VALID;
2453 atomic_long_add(p->pages, &nr_swap_pages);
2454 total_swap_pages += p->pages;
2455
2456 assert_spin_locked(&swap_lock);
2457 /*
2458 * both lists are plists, and thus priority ordered.
2459 * swap_active_head needs to be priority ordered for swapoff(),
2460 * which on removal of any swap_info_struct with an auto-assigned
2461 * (i.e. negative) priority increments the auto-assigned priority
2462 * of any lower-priority swap_info_structs.
2463 * swap_avail_head needs to be priority ordered for get_swap_page(),
2464 * which allocates swap pages from the highest available priority
2465 * swap_info_struct.
2466 */
2467 plist_add(&p->list, &swap_active_head);
2468 add_to_avail_list(p);
2469}
2470
2471static void enable_swap_info(struct swap_info_struct *p, int prio,
2472 unsigned char *swap_map,
2473 struct swap_cluster_info *cluster_info,
2474 unsigned long *frontswap_map)
2475{
2476 frontswap_init(p->type, frontswap_map);
2477 spin_lock(&swap_lock);
2478 spin_lock(&p->lock);
2479 setup_swap_info(p, prio, swap_map, cluster_info);
2480 spin_unlock(&p->lock);
2481 spin_unlock(&swap_lock);
2482 /*
2483 * Guarantee swap_map, cluster_info, etc. fields are valid
2484 * between get/put_swap_device() if SWP_VALID bit is set
2485 */
2486 synchronize_rcu();
2487 spin_lock(&swap_lock);
2488 spin_lock(&p->lock);
2489 _enable_swap_info(p);
2490 spin_unlock(&p->lock);
2491 spin_unlock(&swap_lock);
2492}
2493
2494static void reinsert_swap_info(struct swap_info_struct *p)
2495{
2496 spin_lock(&swap_lock);
2497 spin_lock(&p->lock);
2498 setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2499 _enable_swap_info(p);
2500 spin_unlock(&p->lock);
2501 spin_unlock(&swap_lock);
2502}
2503
2504bool has_usable_swap(void)
2505{
2506 bool ret = true;
2507
2508 spin_lock(&swap_lock);
2509 if (plist_head_empty(&swap_active_head))
2510 ret = false;
2511 spin_unlock(&swap_lock);
2512 return ret;
2513}
2514
2515SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2516{
2517 struct swap_info_struct *p = NULL;
2518 unsigned char *swap_map;
2519 struct swap_cluster_info *cluster_info;
2520 unsigned long *frontswap_map;
2521 struct file *swap_file, *victim;
2522 struct address_space *mapping;
2523 struct inode *inode;
2524 struct filename *pathname;
2525 int err, found = 0;
2526 unsigned int old_block_size;
2527
2528 if (!capable(CAP_SYS_ADMIN))
2529 return -EPERM;
2530
2531 BUG_ON(!current->mm);
2532
2533 pathname = getname(specialfile);
2534 if (IS_ERR(pathname))
2535 return PTR_ERR(pathname);
2536
2537 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2538 err = PTR_ERR(victim);
2539 if (IS_ERR(victim))
2540 goto out;
2541
2542 mapping = victim->f_mapping;
2543 spin_lock(&swap_lock);
2544 plist_for_each_entry(p, &swap_active_head, list) {
2545 if (p->flags & SWP_WRITEOK) {
2546 if (p->swap_file->f_mapping == mapping) {
2547 found = 1;
2548 break;
2549 }
2550 }
2551 }
2552 if (!found) {
2553 err = -EINVAL;
2554 spin_unlock(&swap_lock);
2555 goto out_dput;
2556 }
2557 if (!security_vm_enough_memory_mm(current->mm, p->pages))
2558 vm_unacct_memory(p->pages);
2559 else {
2560 err = -ENOMEM;
2561 spin_unlock(&swap_lock);
2562 goto out_dput;
2563 }
2564 del_from_avail_list(p);
2565 spin_lock(&p->lock);
2566 if (p->prio < 0) {
2567 struct swap_info_struct *si = p;
2568 int nid;
2569
2570 plist_for_each_entry_continue(si, &swap_active_head, list) {
2571 si->prio++;
2572 si->list.prio--;
2573 for_each_node(nid) {
2574 if (si->avail_lists[nid].prio != 1)
2575 si->avail_lists[nid].prio--;
2576 }
2577 }
2578 least_priority++;
2579 }
2580 plist_del(&p->list, &swap_active_head);
2581 atomic_long_sub(p->pages, &nr_swap_pages);
2582 total_swap_pages -= p->pages;
2583 p->flags &= ~SWP_WRITEOK;
2584 spin_unlock(&p->lock);
2585 spin_unlock(&swap_lock);
2586
2587 disable_swap_slots_cache_lock();
2588
2589 set_current_oom_origin();
2590 err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
2591 clear_current_oom_origin();
2592
2593 if (err) {
2594 /* re-insert swap space back into swap_list */
2595 reinsert_swap_info(p);
2596 reenable_swap_slots_cache_unlock();
2597 goto out_dput;
2598 }
2599
2600 reenable_swap_slots_cache_unlock();
2601
2602 spin_lock(&swap_lock);
2603 spin_lock(&p->lock);
2604 p->flags &= ~SWP_VALID; /* mark swap device as invalid */
2605 spin_unlock(&p->lock);
2606 spin_unlock(&swap_lock);
2607 /*
2608 * wait for swap operations protected by get/put_swap_device()
2609 * to complete
2610 */
2611 synchronize_rcu();
2612
2613 flush_work(&p->discard_work);
2614
2615 destroy_swap_extents(p);
2616 if (p->flags & SWP_CONTINUED)
2617 free_swap_count_continuations(p);
2618
2619 if (!p->bdev || !blk_queue_nonrot(bdev_get_queue(p->bdev)))
2620 atomic_dec(&nr_rotate_swap);
2621
2622 mutex_lock(&swapon_mutex);
2623 spin_lock(&swap_lock);
2624 spin_lock(&p->lock);
2625 drain_mmlist();
2626
2627 /* wait for anyone still in scan_swap_map */
2628 p->highest_bit = 0; /* cuts scans short */
2629 while (p->flags >= SWP_SCANNING) {
2630 spin_unlock(&p->lock);
2631 spin_unlock(&swap_lock);
2632 schedule_timeout_uninterruptible(1);
2633 spin_lock(&swap_lock);
2634 spin_lock(&p->lock);
2635 }
2636
2637 swap_file = p->swap_file;
2638 old_block_size = p->old_block_size;
2639 p->swap_file = NULL;
2640 p->max = 0;
2641 swap_map = p->swap_map;
2642 p->swap_map = NULL;
2643 cluster_info = p->cluster_info;
2644 p->cluster_info = NULL;
2645 frontswap_map = frontswap_map_get(p);
2646 spin_unlock(&p->lock);
2647 spin_unlock(&swap_lock);
2648 frontswap_invalidate_area(p->type);
2649 frontswap_map_set(p, NULL);
2650 mutex_unlock(&swapon_mutex);
2651 free_percpu(p->percpu_cluster);
2652 p->percpu_cluster = NULL;
2653 vfree(swap_map);
2654 kvfree(cluster_info);
2655 kvfree(frontswap_map);
2656 /* Destroy swap account information */
2657 swap_cgroup_swapoff(p->type);
2658 exit_swap_address_space(p->type);
2659
2660 inode = mapping->host;
2661 if (S_ISBLK(inode->i_mode)) {
2662 struct block_device *bdev = I_BDEV(inode);
2663
2664 set_blocksize(bdev, old_block_size);
2665 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2666 }
2667
2668 inode_lock(inode);
2669 inode->i_flags &= ~S_SWAPFILE;
2670 inode_unlock(inode);
2671 filp_close(swap_file, NULL);
2672
2673 /*
2674 * Clear the SWP_USED flag after all resources are freed so that swapon
2675 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
2676 * not hold p->lock after we cleared its SWP_WRITEOK.
2677 */
2678 spin_lock(&swap_lock);
2679 p->flags = 0;
2680 spin_unlock(&swap_lock);
2681
2682 err = 0;
2683 atomic_inc(&proc_poll_event);
2684 wake_up_interruptible(&proc_poll_wait);
2685
2686out_dput:
2687 filp_close(victim, NULL);
2688out:
2689 putname(pathname);
2690 return err;
2691}
2692
2693#ifdef CONFIG_PROC_FS
2694static __poll_t swaps_poll(struct file *file, poll_table *wait)
2695{
2696 struct seq_file *seq = file->private_data;
2697
2698 poll_wait(file, &proc_poll_wait, wait);
2699
2700 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2701 seq->poll_event = atomic_read(&proc_poll_event);
2702 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2703 }
2704
2705 return EPOLLIN | EPOLLRDNORM;
2706}
2707
2708/* iterator */
2709static void *swap_start(struct seq_file *swap, loff_t *pos)
2710{
2711 struct swap_info_struct *si;
2712 int type;
2713 loff_t l = *pos;
2714
2715 mutex_lock(&swapon_mutex);
2716
2717 if (!l)
2718 return SEQ_START_TOKEN;
2719
2720 for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2721 if (!(si->flags & SWP_USED) || !si->swap_map)
2722 continue;
2723 if (!--l)
2724 return si;
2725 }
2726
2727 return NULL;
2728}
2729
2730static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2731{
2732 struct swap_info_struct *si = v;
2733 int type;
2734
2735 if (v == SEQ_START_TOKEN)
2736 type = 0;
2737 else
2738 type = si->type + 1;
2739
2740 for (; (si = swap_type_to_swap_info(type)); type++) {
2741 if (!(si->flags & SWP_USED) || !si->swap_map)
2742 continue;
2743 ++*pos;
2744 return si;
2745 }
2746
2747 return NULL;
2748}
2749
2750static void swap_stop(struct seq_file *swap, void *v)
2751{
2752 mutex_unlock(&swapon_mutex);
2753}
2754
2755static int swap_show(struct seq_file *swap, void *v)
2756{
2757 struct swap_info_struct *si = v;
2758 struct file *file;
2759 int len;
2760
2761 if (si == SEQ_START_TOKEN) {
2762 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
2763 return 0;
2764 }
2765
2766 file = si->swap_file;
2767 len = seq_file_path(swap, file, " \t\n\\");
2768 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
2769 len < 40 ? 40 - len : 1, " ",
2770 S_ISBLK(file_inode(file)->i_mode) ?
2771 "partition" : "file\t",
2772 si->pages << (PAGE_SHIFT - 10),
2773 si->inuse_pages << (PAGE_SHIFT - 10),
2774 si->prio);
2775 return 0;
2776}
2777
2778static const struct seq_operations swaps_op = {
2779 .start = swap_start,
2780 .next = swap_next,
2781 .stop = swap_stop,
2782 .show = swap_show
2783};
2784
2785static int swaps_open(struct inode *inode, struct file *file)
2786{
2787 struct seq_file *seq;
2788 int ret;
2789
2790 ret = seq_open(file, &swaps_op);
2791 if (ret)
2792 return ret;
2793
2794 seq = file->private_data;
2795 seq->poll_event = atomic_read(&proc_poll_event);
2796 return 0;
2797}
2798
2799static const struct file_operations proc_swaps_operations = {
2800 .open = swaps_open,
2801 .read = seq_read,
2802 .llseek = seq_lseek,
2803 .release = seq_release,
2804 .poll = swaps_poll,
2805};
2806
2807static int __init procswaps_init(void)
2808{
2809 proc_create("swaps", 0, NULL, &proc_swaps_operations);
2810 return 0;
2811}
2812__initcall(procswaps_init);
2813#endif /* CONFIG_PROC_FS */
2814
2815#ifdef MAX_SWAPFILES_CHECK
2816static int __init max_swapfiles_check(void)
2817{
2818 MAX_SWAPFILES_CHECK();
2819 return 0;
2820}
2821late_initcall(max_swapfiles_check);
2822#endif
2823
2824static struct swap_info_struct *alloc_swap_info(void)
2825{
2826 struct swap_info_struct *p;
2827 unsigned int type;
2828 int i;
2829
2830 p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2831 if (!p)
2832 return ERR_PTR(-ENOMEM);
2833
2834 spin_lock(&swap_lock);
2835 for (type = 0; type < nr_swapfiles; type++) {
2836 if (!(swap_info[type]->flags & SWP_USED))
2837 break;
2838 }
2839 if (type >= MAX_SWAPFILES) {
2840 spin_unlock(&swap_lock);
2841 kvfree(p);
2842 return ERR_PTR(-EPERM);
2843 }
2844 if (type >= nr_swapfiles) {
2845 p->type = type;
2846 WRITE_ONCE(swap_info[type], p);
2847 /*
2848 * Write swap_info[type] before nr_swapfiles, in case a
2849 * racing procfs swap_start() or swap_next() is reading them.
2850 * (We never shrink nr_swapfiles, we never free this entry.)
2851 */
2852 smp_wmb();
2853 WRITE_ONCE(nr_swapfiles, nr_swapfiles + 1);
2854 } else {
2855 kvfree(p);
2856 p = swap_info[type];
2857 /*
2858 * Do not memset this entry: a racing procfs swap_next()
2859 * would be relying on p->type to remain valid.
2860 */
2861 }
2862 p->swap_extent_root = RB_ROOT;
2863 plist_node_init(&p->list, 0);
2864 for_each_node(i)
2865 plist_node_init(&p->avail_lists[i], 0);
2866 p->flags = SWP_USED;
2867 spin_unlock(&swap_lock);
2868 spin_lock_init(&p->lock);
2869 spin_lock_init(&p->cont_lock);
2870
2871 return p;
2872}
2873
2874static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2875{
2876 int error;
2877
2878 if (S_ISBLK(inode->i_mode)) {
2879 p->bdev = bdgrab(I_BDEV(inode));
2880 error = blkdev_get(p->bdev,
2881 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2882 if (error < 0) {
2883 p->bdev = NULL;
2884 return error;
2885 }
2886 p->old_block_size = block_size(p->bdev);
2887 error = set_blocksize(p->bdev, PAGE_SIZE);
2888 if (error < 0)
2889 return error;
2890 p->flags |= SWP_BLKDEV;
2891 } else if (S_ISREG(inode->i_mode)) {
2892 p->bdev = inode->i_sb->s_bdev;
2893 }
2894
2895 inode_lock(inode);
2896 if (IS_SWAPFILE(inode))
2897 return -EBUSY;
2898
2899 return 0;
2900}
2901
2902
2903/*
2904 * Find out how many pages are allowed for a single swap device. There
2905 * are two limiting factors:
2906 * 1) the number of bits for the swap offset in the swp_entry_t type, and
2907 * 2) the number of bits in the swap pte, as defined by the different
2908 * architectures.
2909 *
2910 * In order to find the largest possible bit mask, a swap entry with
2911 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2912 * decoded to a swp_entry_t again, and finally the swap offset is
2913 * extracted.
2914 *
2915 * This will mask all the bits from the initial ~0UL mask that can't
2916 * be encoded in either the swp_entry_t or the architecture definition
2917 * of a swap pte.
2918 */
2919unsigned long generic_max_swapfile_size(void)
2920{
2921 return swp_offset(pte_to_swp_entry(
2922 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2923}
2924
2925/* Can be overridden by an architecture for additional checks. */
2926__weak unsigned long max_swapfile_size(void)
2927{
2928 return generic_max_swapfile_size();
2929}
2930
2931static unsigned long read_swap_header(struct swap_info_struct *p,
2932 union swap_header *swap_header,
2933 struct inode *inode)
2934{
2935 int i;
2936 unsigned long maxpages;
2937 unsigned long swapfilepages;
2938 unsigned long last_page;
2939
2940 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2941 pr_err("Unable to find swap-space signature\n");
2942 return 0;
2943 }
2944
2945 /* swap partition endianess hack... */
2946 if (swab32(swap_header->info.version) == 1) {
2947 swab32s(&swap_header->info.version);
2948 swab32s(&swap_header->info.last_page);
2949 swab32s(&swap_header->info.nr_badpages);
2950 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2951 return 0;
2952 for (i = 0; i < swap_header->info.nr_badpages; i++)
2953 swab32s(&swap_header->info.badpages[i]);
2954 }
2955 /* Check the swap header's sub-version */
2956 if (swap_header->info.version != 1) {
2957 pr_warn("Unable to handle swap header version %d\n",
2958 swap_header->info.version);
2959 return 0;
2960 }
2961
2962 p->lowest_bit = 1;
2963 p->cluster_next = 1;
2964 p->cluster_nr = 0;
2965
2966 maxpages = max_swapfile_size();
2967 last_page = swap_header->info.last_page;
2968 if (!last_page) {
2969 pr_warn("Empty swap-file\n");
2970 return 0;
2971 }
2972 if (last_page > maxpages) {
2973 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2974 maxpages << (PAGE_SHIFT - 10),
2975 last_page << (PAGE_SHIFT - 10));
2976 }
2977 if (maxpages > last_page) {
2978 maxpages = last_page + 1;
2979 /* p->max is an unsigned int: don't overflow it */
2980 if ((unsigned int)maxpages == 0)
2981 maxpages = UINT_MAX;
2982 }
2983 p->highest_bit = maxpages - 1;
2984
2985 if (!maxpages)
2986 return 0;
2987 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2988 if (swapfilepages && maxpages > swapfilepages) {
2989 pr_warn("Swap area shorter than signature indicates\n");
2990 return 0;
2991 }
2992 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2993 return 0;
2994 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2995 return 0;
2996
2997 return maxpages;
2998}
2999
3000#define SWAP_CLUSTER_INFO_COLS \
3001 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
3002#define SWAP_CLUSTER_SPACE_COLS \
3003 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
3004#define SWAP_CLUSTER_COLS \
3005 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
3006
3007static int setup_swap_map_and_extents(struct swap_info_struct *p,
3008 union swap_header *swap_header,
3009 unsigned char *swap_map,
3010 struct swap_cluster_info *cluster_info,
3011 unsigned long maxpages,
3012 sector_t *span)
3013{
3014 unsigned int j, k;
3015 unsigned int nr_good_pages;
3016 int nr_extents;
3017 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3018 unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
3019 unsigned long i, idx;
3020
3021 nr_good_pages = maxpages - 1; /* omit header page */
3022
3023 cluster_list_init(&p->free_clusters);
3024 cluster_list_init(&p->discard_clusters);
3025
3026 for (i = 0; i < swap_header->info.nr_badpages; i++) {
3027 unsigned int page_nr = swap_header->info.badpages[i];
3028 if (page_nr == 0 || page_nr > swap_header->info.last_page)
3029 return -EINVAL;
3030 if (page_nr < maxpages) {
3031 swap_map[page_nr] = SWAP_MAP_BAD;
3032 nr_good_pages--;
3033 /*
3034 * Haven't marked the cluster free yet, no list
3035 * operation involved
3036 */
3037 inc_cluster_info_page(p, cluster_info, page_nr);
3038 }
3039 }
3040
3041 /* Haven't marked the cluster free yet, no list operation involved */
3042 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
3043 inc_cluster_info_page(p, cluster_info, i);
3044
3045 if (nr_good_pages) {
3046 swap_map[0] = SWAP_MAP_BAD;
3047 /*
3048 * Not mark the cluster free yet, no list
3049 * operation involved
3050 */
3051 inc_cluster_info_page(p, cluster_info, 0);
3052 p->max = maxpages;
3053 p->pages = nr_good_pages;
3054 nr_extents = setup_swap_extents(p, span);
3055 if (nr_extents < 0)
3056 return nr_extents;
3057 nr_good_pages = p->pages;
3058 }
3059 if (!nr_good_pages) {
3060 pr_warn("Empty swap-file\n");
3061 return -EINVAL;
3062 }
3063
3064 if (!cluster_info)
3065 return nr_extents;
3066
3067
3068 /*
3069 * Reduce false cache line sharing between cluster_info and
3070 * sharing same address space.
3071 */
3072 for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
3073 j = (k + col) % SWAP_CLUSTER_COLS;
3074 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
3075 idx = i * SWAP_CLUSTER_COLS + j;
3076 if (idx >= nr_clusters)
3077 continue;
3078 if (cluster_count(&cluster_info[idx]))
3079 continue;
3080 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
3081 cluster_list_add_tail(&p->free_clusters, cluster_info,
3082 idx);
3083 }
3084 }
3085 return nr_extents;
3086}
3087
3088/*
3089 * Helper to sys_swapon determining if a given swap
3090 * backing device queue supports DISCARD operations.
3091 */
3092static bool swap_discardable(struct swap_info_struct *si)
3093{
3094 struct request_queue *q = bdev_get_queue(si->bdev);
3095
3096 if (!q || !blk_queue_discard(q))
3097 return false;
3098
3099 return true;
3100}
3101
3102SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
3103{
3104 struct swap_info_struct *p;
3105 struct filename *name;
3106 struct file *swap_file = NULL;
3107 struct address_space *mapping;
3108 int prio;
3109 int error;
3110 union swap_header *swap_header;
3111 int nr_extents;
3112 sector_t span;
3113 unsigned long maxpages;
3114 unsigned char *swap_map = NULL;
3115 struct swap_cluster_info *cluster_info = NULL;
3116 unsigned long *frontswap_map = NULL;
3117 struct page *page = NULL;
3118 struct inode *inode = NULL;
3119 bool inced_nr_rotate_swap = false;
3120
3121 if (swap_flags & ~SWAP_FLAGS_VALID)
3122 return -EINVAL;
3123
3124 if (!capable(CAP_SYS_ADMIN))
3125 return -EPERM;
3126
3127 if (!swap_avail_heads)
3128 return -ENOMEM;
3129
3130 p = alloc_swap_info();
3131 if (IS_ERR(p))
3132 return PTR_ERR(p);
3133
3134 INIT_WORK(&p->discard_work, swap_discard_work);
3135
3136 name = getname(specialfile);
3137 if (IS_ERR(name)) {
3138 error = PTR_ERR(name);
3139 name = NULL;
3140 goto bad_swap;
3141 }
3142 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3143 if (IS_ERR(swap_file)) {
3144 error = PTR_ERR(swap_file);
3145 swap_file = NULL;
3146 goto bad_swap;
3147 }
3148
3149 p->swap_file = swap_file;
3150 mapping = swap_file->f_mapping;
3151 inode = mapping->host;
3152
3153 /* If S_ISREG(inode->i_mode) will do inode_lock(inode); */
3154 error = claim_swapfile(p, inode);
3155 if (unlikely(error))
3156 goto bad_swap;
3157
3158 /*
3159 * Read the swap header.
3160 */
3161 if (!mapping->a_ops->readpage) {
3162 error = -EINVAL;
3163 goto bad_swap;
3164 }
3165 page = read_mapping_page(mapping, 0, swap_file);
3166 if (IS_ERR(page)) {
3167 error = PTR_ERR(page);
3168 goto bad_swap;
3169 }
3170 swap_header = kmap(page);
3171
3172 maxpages = read_swap_header(p, swap_header, inode);
3173 if (unlikely(!maxpages)) {
3174 error = -EINVAL;
3175 goto bad_swap;
3176 }
3177
3178 /* OK, set up the swap map and apply the bad block list */
3179 swap_map = vzalloc(maxpages);
3180 if (!swap_map) {
3181 error = -ENOMEM;
3182 goto bad_swap;
3183 }
3184
3185 if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))
3186 p->flags |= SWP_STABLE_WRITES;
3187
3188 if (bdi_cap_synchronous_io(inode_to_bdi(inode)))
3189 p->flags |= SWP_SYNCHRONOUS_IO;
3190
3191 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
3192 int cpu;
3193 unsigned long ci, nr_cluster;
3194
3195 p->flags |= SWP_SOLIDSTATE;
3196 /*
3197 * select a random position to start with to help wear leveling
3198 * SSD
3199 */
3200 p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
3201 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3202
3203 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3204 GFP_KERNEL);
3205 if (!cluster_info) {
3206 error = -ENOMEM;
3207 goto bad_swap;
3208 }
3209
3210 for (ci = 0; ci < nr_cluster; ci++)
3211 spin_lock_init(&((cluster_info + ci)->lock));
3212
3213 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3214 if (!p->percpu_cluster) {
3215 error = -ENOMEM;
3216 goto bad_swap;
3217 }
3218 for_each_possible_cpu(cpu) {
3219 struct percpu_cluster *cluster;
3220 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3221 cluster_set_null(&cluster->index);
3222 }
3223 } else {
3224 atomic_inc(&nr_rotate_swap);
3225 inced_nr_rotate_swap = true;
3226 }
3227
3228 error = swap_cgroup_swapon(p->type, maxpages);
3229 if (error)
3230 goto bad_swap;
3231
3232 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3233 cluster_info, maxpages, &span);
3234 if (unlikely(nr_extents < 0)) {
3235 error = nr_extents;
3236 goto bad_swap;
3237 }
3238 /* frontswap enabled? set up bit-per-page map for frontswap */
3239 if (IS_ENABLED(CONFIG_FRONTSWAP))
3240 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3241 sizeof(long),
3242 GFP_KERNEL);
3243
3244 if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
3245 /*
3246 * When discard is enabled for swap with no particular
3247 * policy flagged, we set all swap discard flags here in
3248 * order to sustain backward compatibility with older
3249 * swapon(8) releases.
3250 */
3251 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3252 SWP_PAGE_DISCARD);
3253
3254 /*
3255 * By flagging sys_swapon, a sysadmin can tell us to
3256 * either do single-time area discards only, or to just
3257 * perform discards for released swap page-clusters.
3258 * Now it's time to adjust the p->flags accordingly.
3259 */
3260 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3261 p->flags &= ~SWP_PAGE_DISCARD;
3262 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3263 p->flags &= ~SWP_AREA_DISCARD;
3264
3265 /* issue a swapon-time discard if it's still required */
3266 if (p->flags & SWP_AREA_DISCARD) {
3267 int err = discard_swap(p);
3268 if (unlikely(err))
3269 pr_err("swapon: discard_swap(%p): %d\n",
3270 p, err);
3271 }
3272 }
3273
3274 error = init_swap_address_space(p->type, maxpages);
3275 if (error)
3276 goto bad_swap;
3277
3278 /*
3279 * Flush any pending IO and dirty mappings before we start using this
3280 * swap device.
3281 */
3282 inode->i_flags |= S_SWAPFILE;
3283 error = inode_drain_writes(inode);
3284 if (error) {
3285 inode->i_flags &= ~S_SWAPFILE;
3286 goto bad_swap;
3287 }
3288
3289 mutex_lock(&swapon_mutex);
3290 prio = -1;
3291 if (swap_flags & SWAP_FLAG_PREFER)
3292 prio =
3293 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3294 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3295
3296 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3297 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3298 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3299 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3300 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3301 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3302 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3303 (frontswap_map) ? "FS" : "");
3304
3305 mutex_unlock(&swapon_mutex);
3306 atomic_inc(&proc_poll_event);
3307 wake_up_interruptible(&proc_poll_wait);
3308
3309 error = 0;
3310 goto out;
3311bad_swap:
3312 free_percpu(p->percpu_cluster);
3313 p->percpu_cluster = NULL;
3314 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3315 set_blocksize(p->bdev, p->old_block_size);
3316 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3317 }
3318 destroy_swap_extents(p);
3319 swap_cgroup_swapoff(p->type);
3320 spin_lock(&swap_lock);
3321 p->swap_file = NULL;
3322 p->flags = 0;
3323 spin_unlock(&swap_lock);
3324 vfree(swap_map);
3325 kvfree(cluster_info);
3326 kvfree(frontswap_map);
3327 if (inced_nr_rotate_swap)
3328 atomic_dec(&nr_rotate_swap);
3329 if (swap_file) {
3330 if (inode) {
3331 inode_unlock(inode);
3332 inode = NULL;
3333 }
3334 filp_close(swap_file, NULL);
3335 }
3336out:
3337 if (page && !IS_ERR(page)) {
3338 kunmap(page);
3339 put_page(page);
3340 }
3341 if (name)
3342 putname(name);
3343 if (inode)
3344 inode_unlock(inode);
3345 if (!error)
3346 enable_swap_slots_cache();
3347 return error;
3348}
3349
3350void si_swapinfo(struct sysinfo *val)
3351{
3352 unsigned int type;
3353 unsigned long nr_to_be_unused = 0;
3354
3355 spin_lock(&swap_lock);
3356 for (type = 0; type < nr_swapfiles; type++) {
3357 struct swap_info_struct *si = swap_info[type];
3358
3359 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3360 nr_to_be_unused += si->inuse_pages;
3361 }
3362 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3363 val->totalswap = total_swap_pages + nr_to_be_unused;
3364 spin_unlock(&swap_lock);
3365}
3366
3367/*
3368 * Verify that a swap entry is valid and increment its swap map count.
3369 *
3370 * Returns error code in following case.
3371 * - success -> 0
3372 * - swp_entry is invalid -> EINVAL
3373 * - swp_entry is migration entry -> EINVAL
3374 * - swap-cache reference is requested but there is already one. -> EEXIST
3375 * - swap-cache reference is requested but the entry is not used. -> ENOENT
3376 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3377 */
3378static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3379{
3380 struct swap_info_struct *p;
3381 struct swap_cluster_info *ci;
3382 unsigned long offset;
3383 unsigned char count;
3384 unsigned char has_cache;
3385 int err = -EINVAL;
3386
3387 p = get_swap_device(entry);
3388 if (!p)
3389 goto out;
3390
3391 offset = swp_offset(entry);
3392 ci = lock_cluster_or_swap_info(p, offset);
3393
3394 count = p->swap_map[offset];
3395
3396 /*
3397 * swapin_readahead() doesn't check if a swap entry is valid, so the
3398 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3399 */
3400 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3401 err = -ENOENT;
3402 goto unlock_out;
3403 }
3404
3405 has_cache = count & SWAP_HAS_CACHE;
3406 count &= ~SWAP_HAS_CACHE;
3407 err = 0;
3408
3409 if (usage == SWAP_HAS_CACHE) {
3410
3411 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3412 if (!has_cache && count)
3413 has_cache = SWAP_HAS_CACHE;
3414 else if (has_cache) /* someone else added cache */
3415 err = -EEXIST;
3416 else /* no users remaining */
3417 err = -ENOENT;
3418
3419 } else if (count || has_cache) {
3420
3421 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3422 count += usage;
3423 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3424 err = -EINVAL;
3425 else if (swap_count_continued(p, offset, count))
3426 count = COUNT_CONTINUED;
3427 else
3428 err = -ENOMEM;
3429 } else
3430 err = -ENOENT; /* unused swap entry */
3431
3432 p->swap_map[offset] = count | has_cache;
3433
3434unlock_out:
3435 unlock_cluster_or_swap_info(p, ci);
3436out:
3437 if (p)
3438 put_swap_device(p);
3439 return err;
3440}
3441
3442/*
3443 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3444 * (in which case its reference count is never incremented).
3445 */
3446void swap_shmem_alloc(swp_entry_t entry)
3447{
3448 __swap_duplicate(entry, SWAP_MAP_SHMEM);
3449}
3450
3451/*
3452 * Increase reference count of swap entry by 1.
3453 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3454 * but could not be atomically allocated. Returns 0, just as if it succeeded,
3455 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3456 * might occur if a page table entry has got corrupted.
3457 */
3458int swap_duplicate(swp_entry_t entry)
3459{
3460 int err = 0;
3461
3462 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3463 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3464 return err;
3465}
3466
3467/*
3468 * @entry: swap entry for which we allocate swap cache.
3469 *
3470 * Called when allocating swap cache for existing swap entry,
3471 * This can return error codes. Returns 0 at success.
3472 * -EBUSY means there is a swap cache.
3473 * Note: return code is different from swap_duplicate().
3474 */
3475int swapcache_prepare(swp_entry_t entry)
3476{
3477 return __swap_duplicate(entry, SWAP_HAS_CACHE);
3478}
3479
3480struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3481{
3482 return swap_type_to_swap_info(swp_type(entry));
3483}
3484
3485struct swap_info_struct *page_swap_info(struct page *page)
3486{
3487 swp_entry_t entry = { .val = page_private(page) };
3488 return swp_swap_info(entry);
3489}
3490
3491/*
3492 * out-of-line __page_file_ methods to avoid include hell.
3493 */
3494struct address_space *__page_file_mapping(struct page *page)
3495{
3496 return page_swap_info(page)->swap_file->f_mapping;
3497}
3498EXPORT_SYMBOL_GPL(__page_file_mapping);
3499
3500pgoff_t __page_file_index(struct page *page)
3501{
3502 swp_entry_t swap = { .val = page_private(page) };
3503 return swp_offset(swap);
3504}
3505EXPORT_SYMBOL_GPL(__page_file_index);
3506
3507/*
3508 * add_swap_count_continuation - called when a swap count is duplicated
3509 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3510 * page of the original vmalloc'ed swap_map, to hold the continuation count
3511 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
3512 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3513 *
3514 * These continuation pages are seldom referenced: the common paths all work
3515 * on the original swap_map, only referring to a continuation page when the
3516 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3517 *
3518 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3519 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3520 * can be called after dropping locks.
3521 */
3522int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3523{
3524 struct swap_info_struct *si;
3525 struct swap_cluster_info *ci;
3526 struct page *head;
3527 struct page *page;
3528 struct page *list_page;
3529 pgoff_t offset;
3530 unsigned char count;
3531 int ret = 0;
3532
3533 /*
3534 * When debugging, it's easier to use __GFP_ZERO here; but it's better
3535 * for latency not to zero a page while GFP_ATOMIC and holding locks.
3536 */
3537 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3538
3539 si = get_swap_device(entry);
3540 if (!si) {
3541 /*
3542 * An acceptable race has occurred since the failing
3543 * __swap_duplicate(): the swap device may be swapoff
3544 */
3545 goto outer;
3546 }
3547 spin_lock(&si->lock);
3548
3549 offset = swp_offset(entry);
3550
3551 ci = lock_cluster(si, offset);
3552
3553 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
3554
3555 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3556 /*
3557 * The higher the swap count, the more likely it is that tasks
3558 * will race to add swap count continuation: we need to avoid
3559 * over-provisioning.
3560 */
3561 goto out;
3562 }
3563
3564 if (!page) {
3565 ret = -ENOMEM;
3566 goto out;
3567 }
3568
3569 /*
3570 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3571 * no architecture is using highmem pages for kernel page tables: so it
3572 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3573 */
3574 head = vmalloc_to_page(si->swap_map + offset);
3575 offset &= ~PAGE_MASK;
3576
3577 spin_lock(&si->cont_lock);
3578 /*
3579 * Page allocation does not initialize the page's lru field,
3580 * but it does always reset its private field.
3581 */
3582 if (!page_private(head)) {
3583 BUG_ON(count & COUNT_CONTINUED);
3584 INIT_LIST_HEAD(&head->lru);
3585 set_page_private(head, SWP_CONTINUED);
3586 si->flags |= SWP_CONTINUED;
3587 }
3588
3589 list_for_each_entry(list_page, &head->lru, lru) {
3590 unsigned char *map;
3591
3592 /*
3593 * If the previous map said no continuation, but we've found
3594 * a continuation page, free our allocation and use this one.
3595 */
3596 if (!(count & COUNT_CONTINUED))
3597 goto out_unlock_cont;
3598
3599 map = kmap_atomic(list_page) + offset;
3600 count = *map;
3601 kunmap_atomic(map);
3602
3603 /*
3604 * If this continuation count now has some space in it,
3605 * free our allocation and use this one.
3606 */
3607 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3608 goto out_unlock_cont;
3609 }
3610
3611 list_add_tail(&page->lru, &head->lru);
3612 page = NULL; /* now it's attached, don't free it */
3613out_unlock_cont:
3614 spin_unlock(&si->cont_lock);
3615out:
3616 unlock_cluster(ci);
3617 spin_unlock(&si->lock);
3618 put_swap_device(si);
3619outer:
3620 if (page)
3621 __free_page(page);
3622 return ret;
3623}
3624
3625/*
3626 * swap_count_continued - when the original swap_map count is incremented
3627 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3628 * into, carry if so, or else fail until a new continuation page is allocated;
3629 * when the original swap_map count is decremented from 0 with continuation,
3630 * borrow from the continuation and report whether it still holds more.
3631 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3632 * lock.
3633 */
3634static bool swap_count_continued(struct swap_info_struct *si,
3635 pgoff_t offset, unsigned char count)
3636{
3637 struct page *head;
3638 struct page *page;
3639 unsigned char *map;
3640 bool ret;
3641
3642 head = vmalloc_to_page(si->swap_map + offset);
3643 if (page_private(head) != SWP_CONTINUED) {
3644 BUG_ON(count & COUNT_CONTINUED);
3645 return false; /* need to add count continuation */
3646 }
3647
3648 spin_lock(&si->cont_lock);
3649 offset &= ~PAGE_MASK;
3650 page = list_entry(head->lru.next, struct page, lru);
3651 map = kmap_atomic(page) + offset;
3652
3653 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
3654 goto init_map; /* jump over SWAP_CONT_MAX checks */
3655
3656 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3657 /*
3658 * Think of how you add 1 to 999
3659 */
3660 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3661 kunmap_atomic(map);
3662 page = list_entry(page->lru.next, struct page, lru);
3663 BUG_ON(page == head);
3664 map = kmap_atomic(page) + offset;
3665 }
3666 if (*map == SWAP_CONT_MAX) {
3667 kunmap_atomic(map);
3668 page = list_entry(page->lru.next, struct page, lru);
3669 if (page == head) {
3670 ret = false; /* add count continuation */
3671 goto out;
3672 }
3673 map = kmap_atomic(page) + offset;
3674init_map: *map = 0; /* we didn't zero the page */
3675 }
3676 *map += 1;
3677 kunmap_atomic(map);
3678 page = list_entry(page->lru.prev, struct page, lru);
3679 while (page != head) {
3680 map = kmap_atomic(page) + offset;
3681 *map = COUNT_CONTINUED;
3682 kunmap_atomic(map);
3683 page = list_entry(page->lru.prev, struct page, lru);
3684 }
3685 ret = true; /* incremented */
3686
3687 } else { /* decrementing */
3688 /*
3689 * Think of how you subtract 1 from 1000
3690 */
3691 BUG_ON(count != COUNT_CONTINUED);
3692 while (*map == COUNT_CONTINUED) {
3693 kunmap_atomic(map);
3694 page = list_entry(page->lru.next, struct page, lru);
3695 BUG_ON(page == head);
3696 map = kmap_atomic(page) + offset;
3697 }
3698 BUG_ON(*map == 0);
3699 *map -= 1;
3700 if (*map == 0)
3701 count = 0;
3702 kunmap_atomic(map);
3703 page = list_entry(page->lru.prev, struct page, lru);
3704 while (page != head) {
3705 map = kmap_atomic(page) + offset;
3706 *map = SWAP_CONT_MAX | count;
3707 count = COUNT_CONTINUED;
3708 kunmap_atomic(map);
3709 page = list_entry(page->lru.prev, struct page, lru);
3710 }
3711 ret = count == COUNT_CONTINUED;
3712 }
3713out:
3714 spin_unlock(&si->cont_lock);
3715 return ret;
3716}
3717
3718/*
3719 * free_swap_count_continuations - swapoff free all the continuation pages
3720 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3721 */
3722static void free_swap_count_continuations(struct swap_info_struct *si)
3723{
3724 pgoff_t offset;
3725
3726 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3727 struct page *head;
3728 head = vmalloc_to_page(si->swap_map + offset);
3729 if (page_private(head)) {
3730 struct page *page, *next;
3731
3732 list_for_each_entry_safe(page, next, &head->lru, lru) {
3733 list_del(&page->lru);
3734 __free_page(page);
3735 }
3736 }
3737 }
3738}
3739
3740#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3741void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg, int node,
3742 gfp_t gfp_mask)
3743{
3744 struct swap_info_struct *si, *next;
3745 if (!(gfp_mask & __GFP_IO) || !memcg)
3746 return;
3747
3748 if (!blk_cgroup_congested())
3749 return;
3750
3751 /*
3752 * We've already scheduled a throttle, avoid taking the global swap
3753 * lock.
3754 */
3755 if (current->throttle_queue)
3756 return;
3757
3758 spin_lock(&swap_avail_lock);
3759 plist_for_each_entry_safe(si, next, &swap_avail_heads[node],
3760 avail_lists[node]) {
3761 if (si->bdev) {
3762 blkcg_schedule_throttle(bdev_get_queue(si->bdev),
3763 true);
3764 break;
3765 }
3766 }
3767 spin_unlock(&swap_avail_lock);
3768}
3769#endif
3770
3771static int __init swapfile_init(void)
3772{
3773 int nid;
3774
3775 swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3776 GFP_KERNEL);
3777 if (!swap_avail_heads) {
3778 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3779 return -ENOMEM;
3780 }
3781
3782 for_each_node(nid)
3783 plist_head_init(&swap_avail_heads[nid]);
3784
3785 return 0;
3786}
3787subsys_initcall(swapfile_init);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/swapfile.c
4 *
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie
7 */
8
9#include <linux/mm.h>
10#include <linux/sched/mm.h>
11#include <linux/sched/task.h>
12#include <linux/hugetlb.h>
13#include <linux/mman.h>
14#include <linux/slab.h>
15#include <linux/kernel_stat.h>
16#include <linux/swap.h>
17#include <linux/vmalloc.h>
18#include <linux/pagemap.h>
19#include <linux/namei.h>
20#include <linux/shmem_fs.h>
21#include <linux/blkdev.h>
22#include <linux/random.h>
23#include <linux/writeback.h>
24#include <linux/proc_fs.h>
25#include <linux/seq_file.h>
26#include <linux/init.h>
27#include <linux/ksm.h>
28#include <linux/rmap.h>
29#include <linux/security.h>
30#include <linux/backing-dev.h>
31#include <linux/mutex.h>
32#include <linux/capability.h>
33#include <linux/syscalls.h>
34#include <linux/memcontrol.h>
35#include <linux/poll.h>
36#include <linux/oom.h>
37#include <linux/frontswap.h>
38#include <linux/swapfile.h>
39#include <linux/export.h>
40#include <linux/swap_slots.h>
41#include <linux/sort.h>
42
43#include <asm/tlbflush.h>
44#include <linux/swapops.h>
45#include <linux/swap_cgroup.h>
46
47static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
48 unsigned char);
49static void free_swap_count_continuations(struct swap_info_struct *);
50static sector_t map_swap_entry(swp_entry_t, struct block_device**);
51
52DEFINE_SPINLOCK(swap_lock);
53static unsigned int nr_swapfiles;
54atomic_long_t nr_swap_pages;
55/*
56 * Some modules use swappable objects and may try to swap them out under
57 * memory pressure (via the shrinker). Before doing so, they may wish to
58 * check to see if any swap space is available.
59 */
60EXPORT_SYMBOL_GPL(nr_swap_pages);
61/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
62long total_swap_pages;
63static int least_priority = -1;
64
65static const char Bad_file[] = "Bad swap file entry ";
66static const char Unused_file[] = "Unused swap file entry ";
67static const char Bad_offset[] = "Bad swap offset entry ";
68static const char Unused_offset[] = "Unused swap offset entry ";
69
70/*
71 * all active swap_info_structs
72 * protected with swap_lock, and ordered by priority.
73 */
74PLIST_HEAD(swap_active_head);
75
76/*
77 * all available (active, not full) swap_info_structs
78 * protected with swap_avail_lock, ordered by priority.
79 * This is used by get_swap_page() instead of swap_active_head
80 * because swap_active_head includes all swap_info_structs,
81 * but get_swap_page() doesn't need to look at full ones.
82 * This uses its own lock instead of swap_lock because when a
83 * swap_info_struct changes between not-full/full, it needs to
84 * add/remove itself to/from this list, but the swap_info_struct->lock
85 * is held and the locking order requires swap_lock to be taken
86 * before any swap_info_struct->lock.
87 */
88static struct plist_head *swap_avail_heads;
89static DEFINE_SPINLOCK(swap_avail_lock);
90
91struct swap_info_struct *swap_info[MAX_SWAPFILES];
92
93static DEFINE_MUTEX(swapon_mutex);
94
95static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
96/* Activity counter to indicate that a swapon or swapoff has occurred */
97static atomic_t proc_poll_event = ATOMIC_INIT(0);
98
99atomic_t nr_rotate_swap = ATOMIC_INIT(0);
100
101static struct swap_info_struct *swap_type_to_swap_info(int type)
102{
103 if (type >= READ_ONCE(nr_swapfiles))
104 return NULL;
105
106 smp_rmb(); /* Pairs with smp_wmb in alloc_swap_info. */
107 return READ_ONCE(swap_info[type]);
108}
109
110static inline unsigned char swap_count(unsigned char ent)
111{
112 return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
113}
114
115/* Reclaim the swap entry anyway if possible */
116#define TTRS_ANYWAY 0x1
117/*
118 * Reclaim the swap entry if there are no more mappings of the
119 * corresponding page
120 */
121#define TTRS_UNMAPPED 0x2
122/* Reclaim the swap entry if swap is getting full*/
123#define TTRS_FULL 0x4
124
125/* returns 1 if swap entry is freed */
126static int __try_to_reclaim_swap(struct swap_info_struct *si,
127 unsigned long offset, unsigned long flags)
128{
129 swp_entry_t entry = swp_entry(si->type, offset);
130 struct page *page;
131 int ret = 0;
132
133 page = find_get_page(swap_address_space(entry), offset);
134 if (!page)
135 return 0;
136 /*
137 * When this function is called from scan_swap_map_slots() and it's
138 * called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
139 * here. We have to use trylock for avoiding deadlock. This is a special
140 * case and you should use try_to_free_swap() with explicit lock_page()
141 * in usual operations.
142 */
143 if (trylock_page(page)) {
144 if ((flags & TTRS_ANYWAY) ||
145 ((flags & TTRS_UNMAPPED) && !page_mapped(page)) ||
146 ((flags & TTRS_FULL) && mem_cgroup_swap_full(page)))
147 ret = try_to_free_swap(page);
148 unlock_page(page);
149 }
150 put_page(page);
151 return ret;
152}
153
154static inline struct swap_extent *first_se(struct swap_info_struct *sis)
155{
156 struct rb_node *rb = rb_first(&sis->swap_extent_root);
157 return rb_entry(rb, struct swap_extent, rb_node);
158}
159
160static inline struct swap_extent *next_se(struct swap_extent *se)
161{
162 struct rb_node *rb = rb_next(&se->rb_node);
163 return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
164}
165
166/*
167 * swapon tell device that all the old swap contents can be discarded,
168 * to allow the swap device to optimize its wear-levelling.
169 */
170static int discard_swap(struct swap_info_struct *si)
171{
172 struct swap_extent *se;
173 sector_t start_block;
174 sector_t nr_blocks;
175 int err = 0;
176
177 /* Do not discard the swap header page! */
178 se = first_se(si);
179 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
180 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
181 if (nr_blocks) {
182 err = blkdev_issue_discard(si->bdev, start_block,
183 nr_blocks, GFP_KERNEL, 0);
184 if (err)
185 return err;
186 cond_resched();
187 }
188
189 for (se = next_se(se); se; se = next_se(se)) {
190 start_block = se->start_block << (PAGE_SHIFT - 9);
191 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
192
193 err = blkdev_issue_discard(si->bdev, start_block,
194 nr_blocks, GFP_KERNEL, 0);
195 if (err)
196 break;
197
198 cond_resched();
199 }
200 return err; /* That will often be -EOPNOTSUPP */
201}
202
203static struct swap_extent *
204offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
205{
206 struct swap_extent *se;
207 struct rb_node *rb;
208
209 rb = sis->swap_extent_root.rb_node;
210 while (rb) {
211 se = rb_entry(rb, struct swap_extent, rb_node);
212 if (offset < se->start_page)
213 rb = rb->rb_left;
214 else if (offset >= se->start_page + se->nr_pages)
215 rb = rb->rb_right;
216 else
217 return se;
218 }
219 /* It *must* be present */
220 BUG();
221}
222
223/*
224 * swap allocation tell device that a cluster of swap can now be discarded,
225 * to allow the swap device to optimize its wear-levelling.
226 */
227static void discard_swap_cluster(struct swap_info_struct *si,
228 pgoff_t start_page, pgoff_t nr_pages)
229{
230 struct swap_extent *se = offset_to_swap_extent(si, start_page);
231
232 while (nr_pages) {
233 pgoff_t offset = start_page - se->start_page;
234 sector_t start_block = se->start_block + offset;
235 sector_t nr_blocks = se->nr_pages - offset;
236
237 if (nr_blocks > nr_pages)
238 nr_blocks = nr_pages;
239 start_page += nr_blocks;
240 nr_pages -= nr_blocks;
241
242 start_block <<= PAGE_SHIFT - 9;
243 nr_blocks <<= PAGE_SHIFT - 9;
244 if (blkdev_issue_discard(si->bdev, start_block,
245 nr_blocks, GFP_NOIO, 0))
246 break;
247
248 se = next_se(se);
249 }
250}
251
252#ifdef CONFIG_THP_SWAP
253#define SWAPFILE_CLUSTER HPAGE_PMD_NR
254
255#define swap_entry_size(size) (size)
256#else
257#define SWAPFILE_CLUSTER 256
258
259/*
260 * Define swap_entry_size() as constant to let compiler to optimize
261 * out some code if !CONFIG_THP_SWAP
262 */
263#define swap_entry_size(size) 1
264#endif
265#define LATENCY_LIMIT 256
266
267static inline void cluster_set_flag(struct swap_cluster_info *info,
268 unsigned int flag)
269{
270 info->flags = flag;
271}
272
273static inline unsigned int cluster_count(struct swap_cluster_info *info)
274{
275 return info->data;
276}
277
278static inline void cluster_set_count(struct swap_cluster_info *info,
279 unsigned int c)
280{
281 info->data = c;
282}
283
284static inline void cluster_set_count_flag(struct swap_cluster_info *info,
285 unsigned int c, unsigned int f)
286{
287 info->flags = f;
288 info->data = c;
289}
290
291static inline unsigned int cluster_next(struct swap_cluster_info *info)
292{
293 return info->data;
294}
295
296static inline void cluster_set_next(struct swap_cluster_info *info,
297 unsigned int n)
298{
299 info->data = n;
300}
301
302static inline void cluster_set_next_flag(struct swap_cluster_info *info,
303 unsigned int n, unsigned int f)
304{
305 info->flags = f;
306 info->data = n;
307}
308
309static inline bool cluster_is_free(struct swap_cluster_info *info)
310{
311 return info->flags & CLUSTER_FLAG_FREE;
312}
313
314static inline bool cluster_is_null(struct swap_cluster_info *info)
315{
316 return info->flags & CLUSTER_FLAG_NEXT_NULL;
317}
318
319static inline void cluster_set_null(struct swap_cluster_info *info)
320{
321 info->flags = CLUSTER_FLAG_NEXT_NULL;
322 info->data = 0;
323}
324
325static inline bool cluster_is_huge(struct swap_cluster_info *info)
326{
327 if (IS_ENABLED(CONFIG_THP_SWAP))
328 return info->flags & CLUSTER_FLAG_HUGE;
329 return false;
330}
331
332static inline void cluster_clear_huge(struct swap_cluster_info *info)
333{
334 info->flags &= ~CLUSTER_FLAG_HUGE;
335}
336
337static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
338 unsigned long offset)
339{
340 struct swap_cluster_info *ci;
341
342 ci = si->cluster_info;
343 if (ci) {
344 ci += offset / SWAPFILE_CLUSTER;
345 spin_lock(&ci->lock);
346 }
347 return ci;
348}
349
350static inline void unlock_cluster(struct swap_cluster_info *ci)
351{
352 if (ci)
353 spin_unlock(&ci->lock);
354}
355
356/*
357 * Determine the locking method in use for this device. Return
358 * swap_cluster_info if SSD-style cluster-based locking is in place.
359 */
360static inline struct swap_cluster_info *lock_cluster_or_swap_info(
361 struct swap_info_struct *si, unsigned long offset)
362{
363 struct swap_cluster_info *ci;
364
365 /* Try to use fine-grained SSD-style locking if available: */
366 ci = lock_cluster(si, offset);
367 /* Otherwise, fall back to traditional, coarse locking: */
368 if (!ci)
369 spin_lock(&si->lock);
370
371 return ci;
372}
373
374static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
375 struct swap_cluster_info *ci)
376{
377 if (ci)
378 unlock_cluster(ci);
379 else
380 spin_unlock(&si->lock);
381}
382
383static inline bool cluster_list_empty(struct swap_cluster_list *list)
384{
385 return cluster_is_null(&list->head);
386}
387
388static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
389{
390 return cluster_next(&list->head);
391}
392
393static void cluster_list_init(struct swap_cluster_list *list)
394{
395 cluster_set_null(&list->head);
396 cluster_set_null(&list->tail);
397}
398
399static void cluster_list_add_tail(struct swap_cluster_list *list,
400 struct swap_cluster_info *ci,
401 unsigned int idx)
402{
403 if (cluster_list_empty(list)) {
404 cluster_set_next_flag(&list->head, idx, 0);
405 cluster_set_next_flag(&list->tail, idx, 0);
406 } else {
407 struct swap_cluster_info *ci_tail;
408 unsigned int tail = cluster_next(&list->tail);
409
410 /*
411 * Nested cluster lock, but both cluster locks are
412 * only acquired when we held swap_info_struct->lock
413 */
414 ci_tail = ci + tail;
415 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
416 cluster_set_next(ci_tail, idx);
417 spin_unlock(&ci_tail->lock);
418 cluster_set_next_flag(&list->tail, idx, 0);
419 }
420}
421
422static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
423 struct swap_cluster_info *ci)
424{
425 unsigned int idx;
426
427 idx = cluster_next(&list->head);
428 if (cluster_next(&list->tail) == idx) {
429 cluster_set_null(&list->head);
430 cluster_set_null(&list->tail);
431 } else
432 cluster_set_next_flag(&list->head,
433 cluster_next(&ci[idx]), 0);
434
435 return idx;
436}
437
438/* Add a cluster to discard list and schedule it to do discard */
439static void swap_cluster_schedule_discard(struct swap_info_struct *si,
440 unsigned int idx)
441{
442 /*
443 * If scan_swap_map() can't find a free cluster, it will check
444 * si->swap_map directly. To make sure the discarding cluster isn't
445 * taken by scan_swap_map(), mark the swap entries bad (occupied). It
446 * will be cleared after discard
447 */
448 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
449 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
450
451 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
452
453 schedule_work(&si->discard_work);
454}
455
456static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
457{
458 struct swap_cluster_info *ci = si->cluster_info;
459
460 cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
461 cluster_list_add_tail(&si->free_clusters, ci, idx);
462}
463
464/*
465 * Doing discard actually. After a cluster discard is finished, the cluster
466 * will be added to free cluster list. caller should hold si->lock.
467*/
468static void swap_do_scheduled_discard(struct swap_info_struct *si)
469{
470 struct swap_cluster_info *info, *ci;
471 unsigned int idx;
472
473 info = si->cluster_info;
474
475 while (!cluster_list_empty(&si->discard_clusters)) {
476 idx = cluster_list_del_first(&si->discard_clusters, info);
477 spin_unlock(&si->lock);
478
479 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
480 SWAPFILE_CLUSTER);
481
482 spin_lock(&si->lock);
483 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
484 __free_cluster(si, idx);
485 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
486 0, SWAPFILE_CLUSTER);
487 unlock_cluster(ci);
488 }
489}
490
491static void swap_discard_work(struct work_struct *work)
492{
493 struct swap_info_struct *si;
494
495 si = container_of(work, struct swap_info_struct, discard_work);
496
497 spin_lock(&si->lock);
498 swap_do_scheduled_discard(si);
499 spin_unlock(&si->lock);
500}
501
502static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
503{
504 struct swap_cluster_info *ci = si->cluster_info;
505
506 VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
507 cluster_list_del_first(&si->free_clusters, ci);
508 cluster_set_count_flag(ci + idx, 0, 0);
509}
510
511static void free_cluster(struct swap_info_struct *si, unsigned long idx)
512{
513 struct swap_cluster_info *ci = si->cluster_info + idx;
514
515 VM_BUG_ON(cluster_count(ci) != 0);
516 /*
517 * If the swap is discardable, prepare discard the cluster
518 * instead of free it immediately. The cluster will be freed
519 * after discard.
520 */
521 if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
522 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
523 swap_cluster_schedule_discard(si, idx);
524 return;
525 }
526
527 __free_cluster(si, idx);
528}
529
530/*
531 * The cluster corresponding to page_nr will be used. The cluster will be
532 * removed from free cluster list and its usage counter will be increased.
533 */
534static void inc_cluster_info_page(struct swap_info_struct *p,
535 struct swap_cluster_info *cluster_info, unsigned long page_nr)
536{
537 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
538
539 if (!cluster_info)
540 return;
541 if (cluster_is_free(&cluster_info[idx]))
542 alloc_cluster(p, idx);
543
544 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
545 cluster_set_count(&cluster_info[idx],
546 cluster_count(&cluster_info[idx]) + 1);
547}
548
549/*
550 * The cluster corresponding to page_nr decreases one usage. If the usage
551 * counter becomes 0, which means no page in the cluster is in using, we can
552 * optionally discard the cluster and add it to free cluster list.
553 */
554static void dec_cluster_info_page(struct swap_info_struct *p,
555 struct swap_cluster_info *cluster_info, unsigned long page_nr)
556{
557 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
558
559 if (!cluster_info)
560 return;
561
562 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
563 cluster_set_count(&cluster_info[idx],
564 cluster_count(&cluster_info[idx]) - 1);
565
566 if (cluster_count(&cluster_info[idx]) == 0)
567 free_cluster(p, idx);
568}
569
570/*
571 * It's possible scan_swap_map() uses a free cluster in the middle of free
572 * cluster list. Avoiding such abuse to avoid list corruption.
573 */
574static bool
575scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
576 unsigned long offset)
577{
578 struct percpu_cluster *percpu_cluster;
579 bool conflict;
580
581 offset /= SWAPFILE_CLUSTER;
582 conflict = !cluster_list_empty(&si->free_clusters) &&
583 offset != cluster_list_first(&si->free_clusters) &&
584 cluster_is_free(&si->cluster_info[offset]);
585
586 if (!conflict)
587 return false;
588
589 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
590 cluster_set_null(&percpu_cluster->index);
591 return true;
592}
593
594/*
595 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
596 * might involve allocating a new cluster for current CPU too.
597 */
598static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
599 unsigned long *offset, unsigned long *scan_base)
600{
601 struct percpu_cluster *cluster;
602 struct swap_cluster_info *ci;
603 unsigned long tmp, max;
604
605new_cluster:
606 cluster = this_cpu_ptr(si->percpu_cluster);
607 if (cluster_is_null(&cluster->index)) {
608 if (!cluster_list_empty(&si->free_clusters)) {
609 cluster->index = si->free_clusters.head;
610 cluster->next = cluster_next(&cluster->index) *
611 SWAPFILE_CLUSTER;
612 } else if (!cluster_list_empty(&si->discard_clusters)) {
613 /*
614 * we don't have free cluster but have some clusters in
615 * discarding, do discard now and reclaim them, then
616 * reread cluster_next_cpu since we dropped si->lock
617 */
618 swap_do_scheduled_discard(si);
619 *scan_base = this_cpu_read(*si->cluster_next_cpu);
620 *offset = *scan_base;
621 goto new_cluster;
622 } else
623 return false;
624 }
625
626 /*
627 * Other CPUs can use our cluster if they can't find a free cluster,
628 * check if there is still free entry in the cluster
629 */
630 tmp = cluster->next;
631 max = min_t(unsigned long, si->max,
632 (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
633 if (tmp < max) {
634 ci = lock_cluster(si, tmp);
635 while (tmp < max) {
636 if (!si->swap_map[tmp])
637 break;
638 tmp++;
639 }
640 unlock_cluster(ci);
641 }
642 if (tmp >= max) {
643 cluster_set_null(&cluster->index);
644 goto new_cluster;
645 }
646 cluster->next = tmp + 1;
647 *offset = tmp;
648 *scan_base = tmp;
649 return true;
650}
651
652static void __del_from_avail_list(struct swap_info_struct *p)
653{
654 int nid;
655
656 for_each_node(nid)
657 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
658}
659
660static void del_from_avail_list(struct swap_info_struct *p)
661{
662 spin_lock(&swap_avail_lock);
663 __del_from_avail_list(p);
664 spin_unlock(&swap_avail_lock);
665}
666
667static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
668 unsigned int nr_entries)
669{
670 unsigned int end = offset + nr_entries - 1;
671
672 if (offset == si->lowest_bit)
673 si->lowest_bit += nr_entries;
674 if (end == si->highest_bit)
675 WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
676 si->inuse_pages += nr_entries;
677 if (si->inuse_pages == si->pages) {
678 si->lowest_bit = si->max;
679 si->highest_bit = 0;
680 del_from_avail_list(si);
681 }
682}
683
684static void add_to_avail_list(struct swap_info_struct *p)
685{
686 int nid;
687
688 spin_lock(&swap_avail_lock);
689 for_each_node(nid) {
690 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
691 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
692 }
693 spin_unlock(&swap_avail_lock);
694}
695
696static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
697 unsigned int nr_entries)
698{
699 unsigned long begin = offset;
700 unsigned long end = offset + nr_entries - 1;
701 void (*swap_slot_free_notify)(struct block_device *, unsigned long);
702
703 if (offset < si->lowest_bit)
704 si->lowest_bit = offset;
705 if (end > si->highest_bit) {
706 bool was_full = !si->highest_bit;
707
708 WRITE_ONCE(si->highest_bit, end);
709 if (was_full && (si->flags & SWP_WRITEOK))
710 add_to_avail_list(si);
711 }
712 atomic_long_add(nr_entries, &nr_swap_pages);
713 si->inuse_pages -= nr_entries;
714 if (si->flags & SWP_BLKDEV)
715 swap_slot_free_notify =
716 si->bdev->bd_disk->fops->swap_slot_free_notify;
717 else
718 swap_slot_free_notify = NULL;
719 while (offset <= end) {
720 frontswap_invalidate_page(si->type, offset);
721 if (swap_slot_free_notify)
722 swap_slot_free_notify(si->bdev, offset);
723 offset++;
724 }
725 clear_shadow_from_swap_cache(si->type, begin, end);
726}
727
728static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
729{
730 unsigned long prev;
731
732 if (!(si->flags & SWP_SOLIDSTATE)) {
733 si->cluster_next = next;
734 return;
735 }
736
737 prev = this_cpu_read(*si->cluster_next_cpu);
738 /*
739 * Cross the swap address space size aligned trunk, choose
740 * another trunk randomly to avoid lock contention on swap
741 * address space if possible.
742 */
743 if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) !=
744 (next >> SWAP_ADDRESS_SPACE_SHIFT)) {
745 /* No free swap slots available */
746 if (si->highest_bit <= si->lowest_bit)
747 return;
748 next = si->lowest_bit +
749 prandom_u32_max(si->highest_bit - si->lowest_bit + 1);
750 next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
751 next = max_t(unsigned int, next, si->lowest_bit);
752 }
753 this_cpu_write(*si->cluster_next_cpu, next);
754}
755
756static int scan_swap_map_slots(struct swap_info_struct *si,
757 unsigned char usage, int nr,
758 swp_entry_t slots[])
759{
760 struct swap_cluster_info *ci;
761 unsigned long offset;
762 unsigned long scan_base;
763 unsigned long last_in_cluster = 0;
764 int latency_ration = LATENCY_LIMIT;
765 int n_ret = 0;
766 bool scanned_many = false;
767
768 /*
769 * We try to cluster swap pages by allocating them sequentially
770 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
771 * way, however, we resort to first-free allocation, starting
772 * a new cluster. This prevents us from scattering swap pages
773 * all over the entire swap partition, so that we reduce
774 * overall disk seek times between swap pages. -- sct
775 * But we do now try to find an empty cluster. -Andrea
776 * And we let swap pages go all over an SSD partition. Hugh
777 */
778
779 si->flags += SWP_SCANNING;
780 /*
781 * Use percpu scan base for SSD to reduce lock contention on
782 * cluster and swap cache. For HDD, sequential access is more
783 * important.
784 */
785 if (si->flags & SWP_SOLIDSTATE)
786 scan_base = this_cpu_read(*si->cluster_next_cpu);
787 else
788 scan_base = si->cluster_next;
789 offset = scan_base;
790
791 /* SSD algorithm */
792 if (si->cluster_info) {
793 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
794 goto scan;
795 } else if (unlikely(!si->cluster_nr--)) {
796 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
797 si->cluster_nr = SWAPFILE_CLUSTER - 1;
798 goto checks;
799 }
800
801 spin_unlock(&si->lock);
802
803 /*
804 * If seek is expensive, start searching for new cluster from
805 * start of partition, to minimize the span of allocated swap.
806 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
807 * case, just handled by scan_swap_map_try_ssd_cluster() above.
808 */
809 scan_base = offset = si->lowest_bit;
810 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
811
812 /* Locate the first empty (unaligned) cluster */
813 for (; last_in_cluster <= si->highest_bit; offset++) {
814 if (si->swap_map[offset])
815 last_in_cluster = offset + SWAPFILE_CLUSTER;
816 else if (offset == last_in_cluster) {
817 spin_lock(&si->lock);
818 offset -= SWAPFILE_CLUSTER - 1;
819 si->cluster_next = offset;
820 si->cluster_nr = SWAPFILE_CLUSTER - 1;
821 goto checks;
822 }
823 if (unlikely(--latency_ration < 0)) {
824 cond_resched();
825 latency_ration = LATENCY_LIMIT;
826 }
827 }
828
829 offset = scan_base;
830 spin_lock(&si->lock);
831 si->cluster_nr = SWAPFILE_CLUSTER - 1;
832 }
833
834checks:
835 if (si->cluster_info) {
836 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
837 /* take a break if we already got some slots */
838 if (n_ret)
839 goto done;
840 if (!scan_swap_map_try_ssd_cluster(si, &offset,
841 &scan_base))
842 goto scan;
843 }
844 }
845 if (!(si->flags & SWP_WRITEOK))
846 goto no_page;
847 if (!si->highest_bit)
848 goto no_page;
849 if (offset > si->highest_bit)
850 scan_base = offset = si->lowest_bit;
851
852 ci = lock_cluster(si, offset);
853 /* reuse swap entry of cache-only swap if not busy. */
854 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
855 int swap_was_freed;
856 unlock_cluster(ci);
857 spin_unlock(&si->lock);
858 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
859 spin_lock(&si->lock);
860 /* entry was freed successfully, try to use this again */
861 if (swap_was_freed)
862 goto checks;
863 goto scan; /* check next one */
864 }
865
866 if (si->swap_map[offset]) {
867 unlock_cluster(ci);
868 if (!n_ret)
869 goto scan;
870 else
871 goto done;
872 }
873 WRITE_ONCE(si->swap_map[offset], usage);
874 inc_cluster_info_page(si, si->cluster_info, offset);
875 unlock_cluster(ci);
876
877 swap_range_alloc(si, offset, 1);
878 slots[n_ret++] = swp_entry(si->type, offset);
879
880 /* got enough slots or reach max slots? */
881 if ((n_ret == nr) || (offset >= si->highest_bit))
882 goto done;
883
884 /* search for next available slot */
885
886 /* time to take a break? */
887 if (unlikely(--latency_ration < 0)) {
888 if (n_ret)
889 goto done;
890 spin_unlock(&si->lock);
891 cond_resched();
892 spin_lock(&si->lock);
893 latency_ration = LATENCY_LIMIT;
894 }
895
896 /* try to get more slots in cluster */
897 if (si->cluster_info) {
898 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
899 goto checks;
900 } else if (si->cluster_nr && !si->swap_map[++offset]) {
901 /* non-ssd case, still more slots in cluster? */
902 --si->cluster_nr;
903 goto checks;
904 }
905
906 /*
907 * Even if there's no free clusters available (fragmented),
908 * try to scan a little more quickly with lock held unless we
909 * have scanned too many slots already.
910 */
911 if (!scanned_many) {
912 unsigned long scan_limit;
913
914 if (offset < scan_base)
915 scan_limit = scan_base;
916 else
917 scan_limit = si->highest_bit;
918 for (; offset <= scan_limit && --latency_ration > 0;
919 offset++) {
920 if (!si->swap_map[offset])
921 goto checks;
922 }
923 }
924
925done:
926 set_cluster_next(si, offset + 1);
927 si->flags -= SWP_SCANNING;
928 return n_ret;
929
930scan:
931 spin_unlock(&si->lock);
932 while (++offset <= READ_ONCE(si->highest_bit)) {
933 if (data_race(!si->swap_map[offset])) {
934 spin_lock(&si->lock);
935 goto checks;
936 }
937 if (vm_swap_full() &&
938 READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
939 spin_lock(&si->lock);
940 goto checks;
941 }
942 if (unlikely(--latency_ration < 0)) {
943 cond_resched();
944 latency_ration = LATENCY_LIMIT;
945 scanned_many = true;
946 }
947 }
948 offset = si->lowest_bit;
949 while (offset < scan_base) {
950 if (data_race(!si->swap_map[offset])) {
951 spin_lock(&si->lock);
952 goto checks;
953 }
954 if (vm_swap_full() &&
955 READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
956 spin_lock(&si->lock);
957 goto checks;
958 }
959 if (unlikely(--latency_ration < 0)) {
960 cond_resched();
961 latency_ration = LATENCY_LIMIT;
962 scanned_many = true;
963 }
964 offset++;
965 }
966 spin_lock(&si->lock);
967
968no_page:
969 si->flags -= SWP_SCANNING;
970 return n_ret;
971}
972
973static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
974{
975 unsigned long idx;
976 struct swap_cluster_info *ci;
977 unsigned long offset, i;
978 unsigned char *map;
979
980 /*
981 * Should not even be attempting cluster allocations when huge
982 * page swap is disabled. Warn and fail the allocation.
983 */
984 if (!IS_ENABLED(CONFIG_THP_SWAP)) {
985 VM_WARN_ON_ONCE(1);
986 return 0;
987 }
988
989 if (cluster_list_empty(&si->free_clusters))
990 return 0;
991
992 idx = cluster_list_first(&si->free_clusters);
993 offset = idx * SWAPFILE_CLUSTER;
994 ci = lock_cluster(si, offset);
995 alloc_cluster(si, idx);
996 cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
997
998 map = si->swap_map + offset;
999 for (i = 0; i < SWAPFILE_CLUSTER; i++)
1000 map[i] = SWAP_HAS_CACHE;
1001 unlock_cluster(ci);
1002 swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
1003 *slot = swp_entry(si->type, offset);
1004
1005 return 1;
1006}
1007
1008static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
1009{
1010 unsigned long offset = idx * SWAPFILE_CLUSTER;
1011 struct swap_cluster_info *ci;
1012
1013 ci = lock_cluster(si, offset);
1014 memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
1015 cluster_set_count_flag(ci, 0, 0);
1016 free_cluster(si, idx);
1017 unlock_cluster(ci);
1018 swap_range_free(si, offset, SWAPFILE_CLUSTER);
1019}
1020
1021static unsigned long scan_swap_map(struct swap_info_struct *si,
1022 unsigned char usage)
1023{
1024 swp_entry_t entry;
1025 int n_ret;
1026
1027 n_ret = scan_swap_map_slots(si, usage, 1, &entry);
1028
1029 if (n_ret)
1030 return swp_offset(entry);
1031 else
1032 return 0;
1033
1034}
1035
1036int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
1037{
1038 unsigned long size = swap_entry_size(entry_size);
1039 struct swap_info_struct *si, *next;
1040 long avail_pgs;
1041 int n_ret = 0;
1042 int node;
1043
1044 /* Only single cluster request supported */
1045 WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1046
1047 avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1048 if (avail_pgs <= 0)
1049 goto noswap;
1050
1051 n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
1052
1053 atomic_long_sub(n_goal * size, &nr_swap_pages);
1054
1055 spin_lock(&swap_avail_lock);
1056
1057start_over:
1058 node = numa_node_id();
1059 plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
1060 /* requeue si to after same-priority siblings */
1061 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
1062 spin_unlock(&swap_avail_lock);
1063 spin_lock(&si->lock);
1064 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
1065 spin_lock(&swap_avail_lock);
1066 if (plist_node_empty(&si->avail_lists[node])) {
1067 spin_unlock(&si->lock);
1068 goto nextsi;
1069 }
1070 WARN(!si->highest_bit,
1071 "swap_info %d in list but !highest_bit\n",
1072 si->type);
1073 WARN(!(si->flags & SWP_WRITEOK),
1074 "swap_info %d in list but !SWP_WRITEOK\n",
1075 si->type);
1076 __del_from_avail_list(si);
1077 spin_unlock(&si->lock);
1078 goto nextsi;
1079 }
1080 if (size == SWAPFILE_CLUSTER) {
1081 if (si->flags & SWP_BLKDEV)
1082 n_ret = swap_alloc_cluster(si, swp_entries);
1083 } else
1084 n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1085 n_goal, swp_entries);
1086 spin_unlock(&si->lock);
1087 if (n_ret || size == SWAPFILE_CLUSTER)
1088 goto check_out;
1089 pr_debug("scan_swap_map of si %d failed to find offset\n",
1090 si->type);
1091
1092 spin_lock(&swap_avail_lock);
1093nextsi:
1094 /*
1095 * if we got here, it's likely that si was almost full before,
1096 * and since scan_swap_map() can drop the si->lock, multiple
1097 * callers probably all tried to get a page from the same si
1098 * and it filled up before we could get one; or, the si filled
1099 * up between us dropping swap_avail_lock and taking si->lock.
1100 * Since we dropped the swap_avail_lock, the swap_avail_head
1101 * list may have been modified; so if next is still in the
1102 * swap_avail_head list then try it, otherwise start over
1103 * if we have not gotten any slots.
1104 */
1105 if (plist_node_empty(&next->avail_lists[node]))
1106 goto start_over;
1107 }
1108
1109 spin_unlock(&swap_avail_lock);
1110
1111check_out:
1112 if (n_ret < n_goal)
1113 atomic_long_add((long)(n_goal - n_ret) * size,
1114 &nr_swap_pages);
1115noswap:
1116 return n_ret;
1117}
1118
1119/* The only caller of this function is now suspend routine */
1120swp_entry_t get_swap_page_of_type(int type)
1121{
1122 struct swap_info_struct *si = swap_type_to_swap_info(type);
1123 pgoff_t offset;
1124
1125 if (!si)
1126 goto fail;
1127
1128 spin_lock(&si->lock);
1129 if (si->flags & SWP_WRITEOK) {
1130 atomic_long_dec(&nr_swap_pages);
1131 /* This is called for allocating swap entry, not cache */
1132 offset = scan_swap_map(si, 1);
1133 if (offset) {
1134 spin_unlock(&si->lock);
1135 return swp_entry(type, offset);
1136 }
1137 atomic_long_inc(&nr_swap_pages);
1138 }
1139 spin_unlock(&si->lock);
1140fail:
1141 return (swp_entry_t) {0};
1142}
1143
1144static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
1145{
1146 struct swap_info_struct *p;
1147 unsigned long offset;
1148
1149 if (!entry.val)
1150 goto out;
1151 p = swp_swap_info(entry);
1152 if (!p)
1153 goto bad_nofile;
1154 if (data_race(!(p->flags & SWP_USED)))
1155 goto bad_device;
1156 offset = swp_offset(entry);
1157 if (offset >= p->max)
1158 goto bad_offset;
1159 return p;
1160
1161bad_offset:
1162 pr_err("swap_info_get: %s%08lx\n", Bad_offset, entry.val);
1163 goto out;
1164bad_device:
1165 pr_err("swap_info_get: %s%08lx\n", Unused_file, entry.val);
1166 goto out;
1167bad_nofile:
1168 pr_err("swap_info_get: %s%08lx\n", Bad_file, entry.val);
1169out:
1170 return NULL;
1171}
1172
1173static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1174{
1175 struct swap_info_struct *p;
1176
1177 p = __swap_info_get(entry);
1178 if (!p)
1179 goto out;
1180 if (data_race(!p->swap_map[swp_offset(entry)]))
1181 goto bad_free;
1182 return p;
1183
1184bad_free:
1185 pr_err("swap_info_get: %s%08lx\n", Unused_offset, entry.val);
1186 goto out;
1187out:
1188 return NULL;
1189}
1190
1191static struct swap_info_struct *swap_info_get(swp_entry_t entry)
1192{
1193 struct swap_info_struct *p;
1194
1195 p = _swap_info_get(entry);
1196 if (p)
1197 spin_lock(&p->lock);
1198 return p;
1199}
1200
1201static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1202 struct swap_info_struct *q)
1203{
1204 struct swap_info_struct *p;
1205
1206 p = _swap_info_get(entry);
1207
1208 if (p != q) {
1209 if (q != NULL)
1210 spin_unlock(&q->lock);
1211 if (p != NULL)
1212 spin_lock(&p->lock);
1213 }
1214 return p;
1215}
1216
1217static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1218 unsigned long offset,
1219 unsigned char usage)
1220{
1221 unsigned char count;
1222 unsigned char has_cache;
1223
1224 count = p->swap_map[offset];
1225
1226 has_cache = count & SWAP_HAS_CACHE;
1227 count &= ~SWAP_HAS_CACHE;
1228
1229 if (usage == SWAP_HAS_CACHE) {
1230 VM_BUG_ON(!has_cache);
1231 has_cache = 0;
1232 } else if (count == SWAP_MAP_SHMEM) {
1233 /*
1234 * Or we could insist on shmem.c using a special
1235 * swap_shmem_free() and free_shmem_swap_and_cache()...
1236 */
1237 count = 0;
1238 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1239 if (count == COUNT_CONTINUED) {
1240 if (swap_count_continued(p, offset, count))
1241 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1242 else
1243 count = SWAP_MAP_MAX;
1244 } else
1245 count--;
1246 }
1247
1248 usage = count | has_cache;
1249 if (usage)
1250 WRITE_ONCE(p->swap_map[offset], usage);
1251 else
1252 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
1253
1254 return usage;
1255}
1256
1257/*
1258 * Check whether swap entry is valid in the swap device. If so,
1259 * return pointer to swap_info_struct, and keep the swap entry valid
1260 * via preventing the swap device from being swapoff, until
1261 * put_swap_device() is called. Otherwise return NULL.
1262 *
1263 * The entirety of the RCU read critical section must come before the
1264 * return from or after the call to synchronize_rcu() in
1265 * enable_swap_info() or swapoff(). So if "si->flags & SWP_VALID" is
1266 * true, the si->map, si->cluster_info, etc. must be valid in the
1267 * critical section.
1268 *
1269 * Notice that swapoff or swapoff+swapon can still happen before the
1270 * rcu_read_lock() in get_swap_device() or after the rcu_read_unlock()
1271 * in put_swap_device() if there isn't any other way to prevent
1272 * swapoff, such as page lock, page table lock, etc. The caller must
1273 * be prepared for that. For example, the following situation is
1274 * possible.
1275 *
1276 * CPU1 CPU2
1277 * do_swap_page()
1278 * ... swapoff+swapon
1279 * __read_swap_cache_async()
1280 * swapcache_prepare()
1281 * __swap_duplicate()
1282 * // check swap_map
1283 * // verify PTE not changed
1284 *
1285 * In __swap_duplicate(), the swap_map need to be checked before
1286 * changing partly because the specified swap entry may be for another
1287 * swap device which has been swapoff. And in do_swap_page(), after
1288 * the page is read from the swap device, the PTE is verified not
1289 * changed with the page table locked to check whether the swap device
1290 * has been swapoff or swapoff+swapon.
1291 */
1292struct swap_info_struct *get_swap_device(swp_entry_t entry)
1293{
1294 struct swap_info_struct *si;
1295 unsigned long offset;
1296
1297 if (!entry.val)
1298 goto out;
1299 si = swp_swap_info(entry);
1300 if (!si)
1301 goto bad_nofile;
1302
1303 rcu_read_lock();
1304 if (data_race(!(si->flags & SWP_VALID)))
1305 goto unlock_out;
1306 offset = swp_offset(entry);
1307 if (offset >= si->max)
1308 goto unlock_out;
1309
1310 return si;
1311bad_nofile:
1312 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1313out:
1314 return NULL;
1315unlock_out:
1316 rcu_read_unlock();
1317 return NULL;
1318}
1319
1320static unsigned char __swap_entry_free(struct swap_info_struct *p,
1321 swp_entry_t entry)
1322{
1323 struct swap_cluster_info *ci;
1324 unsigned long offset = swp_offset(entry);
1325 unsigned char usage;
1326
1327 ci = lock_cluster_or_swap_info(p, offset);
1328 usage = __swap_entry_free_locked(p, offset, 1);
1329 unlock_cluster_or_swap_info(p, ci);
1330 if (!usage)
1331 free_swap_slot(entry);
1332
1333 return usage;
1334}
1335
1336static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1337{
1338 struct swap_cluster_info *ci;
1339 unsigned long offset = swp_offset(entry);
1340 unsigned char count;
1341
1342 ci = lock_cluster(p, offset);
1343 count = p->swap_map[offset];
1344 VM_BUG_ON(count != SWAP_HAS_CACHE);
1345 p->swap_map[offset] = 0;
1346 dec_cluster_info_page(p, p->cluster_info, offset);
1347 unlock_cluster(ci);
1348
1349 mem_cgroup_uncharge_swap(entry, 1);
1350 swap_range_free(p, offset, 1);
1351}
1352
1353/*
1354 * Caller has made sure that the swap device corresponding to entry
1355 * is still around or has not been recycled.
1356 */
1357void swap_free(swp_entry_t entry)
1358{
1359 struct swap_info_struct *p;
1360
1361 p = _swap_info_get(entry);
1362 if (p)
1363 __swap_entry_free(p, entry);
1364}
1365
1366/*
1367 * Called after dropping swapcache to decrease refcnt to swap entries.
1368 */
1369void put_swap_page(struct page *page, swp_entry_t entry)
1370{
1371 unsigned long offset = swp_offset(entry);
1372 unsigned long idx = offset / SWAPFILE_CLUSTER;
1373 struct swap_cluster_info *ci;
1374 struct swap_info_struct *si;
1375 unsigned char *map;
1376 unsigned int i, free_entries = 0;
1377 unsigned char val;
1378 int size = swap_entry_size(thp_nr_pages(page));
1379
1380 si = _swap_info_get(entry);
1381 if (!si)
1382 return;
1383
1384 ci = lock_cluster_or_swap_info(si, offset);
1385 if (size == SWAPFILE_CLUSTER) {
1386 VM_BUG_ON(!cluster_is_huge(ci));
1387 map = si->swap_map + offset;
1388 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1389 val = map[i];
1390 VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1391 if (val == SWAP_HAS_CACHE)
1392 free_entries++;
1393 }
1394 cluster_clear_huge(ci);
1395 if (free_entries == SWAPFILE_CLUSTER) {
1396 unlock_cluster_or_swap_info(si, ci);
1397 spin_lock(&si->lock);
1398 mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1399 swap_free_cluster(si, idx);
1400 spin_unlock(&si->lock);
1401 return;
1402 }
1403 }
1404 for (i = 0; i < size; i++, entry.val++) {
1405 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1406 unlock_cluster_or_swap_info(si, ci);
1407 free_swap_slot(entry);
1408 if (i == size - 1)
1409 return;
1410 lock_cluster_or_swap_info(si, offset);
1411 }
1412 }
1413 unlock_cluster_or_swap_info(si, ci);
1414}
1415
1416#ifdef CONFIG_THP_SWAP
1417int split_swap_cluster(swp_entry_t entry)
1418{
1419 struct swap_info_struct *si;
1420 struct swap_cluster_info *ci;
1421 unsigned long offset = swp_offset(entry);
1422
1423 si = _swap_info_get(entry);
1424 if (!si)
1425 return -EBUSY;
1426 ci = lock_cluster(si, offset);
1427 cluster_clear_huge(ci);
1428 unlock_cluster(ci);
1429 return 0;
1430}
1431#endif
1432
1433static int swp_entry_cmp(const void *ent1, const void *ent2)
1434{
1435 const swp_entry_t *e1 = ent1, *e2 = ent2;
1436
1437 return (int)swp_type(*e1) - (int)swp_type(*e2);
1438}
1439
1440void swapcache_free_entries(swp_entry_t *entries, int n)
1441{
1442 struct swap_info_struct *p, *prev;
1443 int i;
1444
1445 if (n <= 0)
1446 return;
1447
1448 prev = NULL;
1449 p = NULL;
1450
1451 /*
1452 * Sort swap entries by swap device, so each lock is only taken once.
1453 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1454 * so low that it isn't necessary to optimize further.
1455 */
1456 if (nr_swapfiles > 1)
1457 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1458 for (i = 0; i < n; ++i) {
1459 p = swap_info_get_cont(entries[i], prev);
1460 if (p)
1461 swap_entry_free(p, entries[i]);
1462 prev = p;
1463 }
1464 if (p)
1465 spin_unlock(&p->lock);
1466}
1467
1468/*
1469 * How many references to page are currently swapped out?
1470 * This does not give an exact answer when swap count is continued,
1471 * but does include the high COUNT_CONTINUED flag to allow for that.
1472 */
1473int page_swapcount(struct page *page)
1474{
1475 int count = 0;
1476 struct swap_info_struct *p;
1477 struct swap_cluster_info *ci;
1478 swp_entry_t entry;
1479 unsigned long offset;
1480
1481 entry.val = page_private(page);
1482 p = _swap_info_get(entry);
1483 if (p) {
1484 offset = swp_offset(entry);
1485 ci = lock_cluster_or_swap_info(p, offset);
1486 count = swap_count(p->swap_map[offset]);
1487 unlock_cluster_or_swap_info(p, ci);
1488 }
1489 return count;
1490}
1491
1492int __swap_count(swp_entry_t entry)
1493{
1494 struct swap_info_struct *si;
1495 pgoff_t offset = swp_offset(entry);
1496 int count = 0;
1497
1498 si = get_swap_device(entry);
1499 if (si) {
1500 count = swap_count(si->swap_map[offset]);
1501 put_swap_device(si);
1502 }
1503 return count;
1504}
1505
1506static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1507{
1508 int count = 0;
1509 pgoff_t offset = swp_offset(entry);
1510 struct swap_cluster_info *ci;
1511
1512 ci = lock_cluster_or_swap_info(si, offset);
1513 count = swap_count(si->swap_map[offset]);
1514 unlock_cluster_or_swap_info(si, ci);
1515 return count;
1516}
1517
1518/*
1519 * How many references to @entry are currently swapped out?
1520 * This does not give an exact answer when swap count is continued,
1521 * but does include the high COUNT_CONTINUED flag to allow for that.
1522 */
1523int __swp_swapcount(swp_entry_t entry)
1524{
1525 int count = 0;
1526 struct swap_info_struct *si;
1527
1528 si = get_swap_device(entry);
1529 if (si) {
1530 count = swap_swapcount(si, entry);
1531 put_swap_device(si);
1532 }
1533 return count;
1534}
1535
1536/*
1537 * How many references to @entry are currently swapped out?
1538 * This considers COUNT_CONTINUED so it returns exact answer.
1539 */
1540int swp_swapcount(swp_entry_t entry)
1541{
1542 int count, tmp_count, n;
1543 struct swap_info_struct *p;
1544 struct swap_cluster_info *ci;
1545 struct page *page;
1546 pgoff_t offset;
1547 unsigned char *map;
1548
1549 p = _swap_info_get(entry);
1550 if (!p)
1551 return 0;
1552
1553 offset = swp_offset(entry);
1554
1555 ci = lock_cluster_or_swap_info(p, offset);
1556
1557 count = swap_count(p->swap_map[offset]);
1558 if (!(count & COUNT_CONTINUED))
1559 goto out;
1560
1561 count &= ~COUNT_CONTINUED;
1562 n = SWAP_MAP_MAX + 1;
1563
1564 page = vmalloc_to_page(p->swap_map + offset);
1565 offset &= ~PAGE_MASK;
1566 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1567
1568 do {
1569 page = list_next_entry(page, lru);
1570 map = kmap_atomic(page);
1571 tmp_count = map[offset];
1572 kunmap_atomic(map);
1573
1574 count += (tmp_count & ~COUNT_CONTINUED) * n;
1575 n *= (SWAP_CONT_MAX + 1);
1576 } while (tmp_count & COUNT_CONTINUED);
1577out:
1578 unlock_cluster_or_swap_info(p, ci);
1579 return count;
1580}
1581
1582static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1583 swp_entry_t entry)
1584{
1585 struct swap_cluster_info *ci;
1586 unsigned char *map = si->swap_map;
1587 unsigned long roffset = swp_offset(entry);
1588 unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1589 int i;
1590 bool ret = false;
1591
1592 ci = lock_cluster_or_swap_info(si, offset);
1593 if (!ci || !cluster_is_huge(ci)) {
1594 if (swap_count(map[roffset]))
1595 ret = true;
1596 goto unlock_out;
1597 }
1598 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1599 if (swap_count(map[offset + i])) {
1600 ret = true;
1601 break;
1602 }
1603 }
1604unlock_out:
1605 unlock_cluster_or_swap_info(si, ci);
1606 return ret;
1607}
1608
1609static bool page_swapped(struct page *page)
1610{
1611 swp_entry_t entry;
1612 struct swap_info_struct *si;
1613
1614 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
1615 return page_swapcount(page) != 0;
1616
1617 page = compound_head(page);
1618 entry.val = page_private(page);
1619 si = _swap_info_get(entry);
1620 if (si)
1621 return swap_page_trans_huge_swapped(si, entry);
1622 return false;
1623}
1624
1625static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
1626 int *total_swapcount)
1627{
1628 int i, map_swapcount, _total_mapcount, _total_swapcount;
1629 unsigned long offset = 0;
1630 struct swap_info_struct *si;
1631 struct swap_cluster_info *ci = NULL;
1632 unsigned char *map = NULL;
1633 int mapcount, swapcount = 0;
1634
1635 /* hugetlbfs shouldn't call it */
1636 VM_BUG_ON_PAGE(PageHuge(page), page);
1637
1638 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {
1639 mapcount = page_trans_huge_mapcount(page, total_mapcount);
1640 if (PageSwapCache(page))
1641 swapcount = page_swapcount(page);
1642 if (total_swapcount)
1643 *total_swapcount = swapcount;
1644 return mapcount + swapcount;
1645 }
1646
1647 page = compound_head(page);
1648
1649 _total_mapcount = _total_swapcount = map_swapcount = 0;
1650 if (PageSwapCache(page)) {
1651 swp_entry_t entry;
1652
1653 entry.val = page_private(page);
1654 si = _swap_info_get(entry);
1655 if (si) {
1656 map = si->swap_map;
1657 offset = swp_offset(entry);
1658 }
1659 }
1660 if (map)
1661 ci = lock_cluster(si, offset);
1662 for (i = 0; i < HPAGE_PMD_NR; i++) {
1663 mapcount = atomic_read(&page[i]._mapcount) + 1;
1664 _total_mapcount += mapcount;
1665 if (map) {
1666 swapcount = swap_count(map[offset + i]);
1667 _total_swapcount += swapcount;
1668 }
1669 map_swapcount = max(map_swapcount, mapcount + swapcount);
1670 }
1671 unlock_cluster(ci);
1672 if (PageDoubleMap(page)) {
1673 map_swapcount -= 1;
1674 _total_mapcount -= HPAGE_PMD_NR;
1675 }
1676 mapcount = compound_mapcount(page);
1677 map_swapcount += mapcount;
1678 _total_mapcount += mapcount;
1679 if (total_mapcount)
1680 *total_mapcount = _total_mapcount;
1681 if (total_swapcount)
1682 *total_swapcount = _total_swapcount;
1683
1684 return map_swapcount;
1685}
1686
1687/*
1688 * We can write to an anon page without COW if there are no other references
1689 * to it. And as a side-effect, free up its swap: because the old content
1690 * on disk will never be read, and seeking back there to write new content
1691 * later would only waste time away from clustering.
1692 *
1693 * NOTE: total_map_swapcount should not be relied upon by the caller if
1694 * reuse_swap_page() returns false, but it may be always overwritten
1695 * (see the other implementation for CONFIG_SWAP=n).
1696 */
1697bool reuse_swap_page(struct page *page, int *total_map_swapcount)
1698{
1699 int count, total_mapcount, total_swapcount;
1700
1701 VM_BUG_ON_PAGE(!PageLocked(page), page);
1702 if (unlikely(PageKsm(page)))
1703 return false;
1704 count = page_trans_huge_map_swapcount(page, &total_mapcount,
1705 &total_swapcount);
1706 if (total_map_swapcount)
1707 *total_map_swapcount = total_mapcount + total_swapcount;
1708 if (count == 1 && PageSwapCache(page) &&
1709 (likely(!PageTransCompound(page)) ||
1710 /* The remaining swap count will be freed soon */
1711 total_swapcount == page_swapcount(page))) {
1712 if (!PageWriteback(page)) {
1713 page = compound_head(page);
1714 delete_from_swap_cache(page);
1715 SetPageDirty(page);
1716 } else {
1717 swp_entry_t entry;
1718 struct swap_info_struct *p;
1719
1720 entry.val = page_private(page);
1721 p = swap_info_get(entry);
1722 if (p->flags & SWP_STABLE_WRITES) {
1723 spin_unlock(&p->lock);
1724 return false;
1725 }
1726 spin_unlock(&p->lock);
1727 }
1728 }
1729
1730 return count <= 1;
1731}
1732
1733/*
1734 * If swap is getting full, or if there are no more mappings of this page,
1735 * then try_to_free_swap is called to free its swap space.
1736 */
1737int try_to_free_swap(struct page *page)
1738{
1739 VM_BUG_ON_PAGE(!PageLocked(page), page);
1740
1741 if (!PageSwapCache(page))
1742 return 0;
1743 if (PageWriteback(page))
1744 return 0;
1745 if (page_swapped(page))
1746 return 0;
1747
1748 /*
1749 * Once hibernation has begun to create its image of memory,
1750 * there's a danger that one of the calls to try_to_free_swap()
1751 * - most probably a call from __try_to_reclaim_swap() while
1752 * hibernation is allocating its own swap pages for the image,
1753 * but conceivably even a call from memory reclaim - will free
1754 * the swap from a page which has already been recorded in the
1755 * image as a clean swapcache page, and then reuse its swap for
1756 * another page of the image. On waking from hibernation, the
1757 * original page might be freed under memory pressure, then
1758 * later read back in from swap, now with the wrong data.
1759 *
1760 * Hibernation suspends storage while it is writing the image
1761 * to disk so check that here.
1762 */
1763 if (pm_suspended_storage())
1764 return 0;
1765
1766 page = compound_head(page);
1767 delete_from_swap_cache(page);
1768 SetPageDirty(page);
1769 return 1;
1770}
1771
1772/*
1773 * Free the swap entry like above, but also try to
1774 * free the page cache entry if it is the last user.
1775 */
1776int free_swap_and_cache(swp_entry_t entry)
1777{
1778 struct swap_info_struct *p;
1779 unsigned char count;
1780
1781 if (non_swap_entry(entry))
1782 return 1;
1783
1784 p = _swap_info_get(entry);
1785 if (p) {
1786 count = __swap_entry_free(p, entry);
1787 if (count == SWAP_HAS_CACHE &&
1788 !swap_page_trans_huge_swapped(p, entry))
1789 __try_to_reclaim_swap(p, swp_offset(entry),
1790 TTRS_UNMAPPED | TTRS_FULL);
1791 }
1792 return p != NULL;
1793}
1794
1795#ifdef CONFIG_HIBERNATION
1796/*
1797 * Find the swap type that corresponds to given device (if any).
1798 *
1799 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1800 * from 0, in which the swap header is expected to be located.
1801 *
1802 * This is needed for the suspend to disk (aka swsusp).
1803 */
1804int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
1805{
1806 struct block_device *bdev = NULL;
1807 int type;
1808
1809 if (device)
1810 bdev = bdget(device);
1811
1812 spin_lock(&swap_lock);
1813 for (type = 0; type < nr_swapfiles; type++) {
1814 struct swap_info_struct *sis = swap_info[type];
1815
1816 if (!(sis->flags & SWP_WRITEOK))
1817 continue;
1818
1819 if (!bdev) {
1820 if (bdev_p)
1821 *bdev_p = bdgrab(sis->bdev);
1822
1823 spin_unlock(&swap_lock);
1824 return type;
1825 }
1826 if (bdev == sis->bdev) {
1827 struct swap_extent *se = first_se(sis);
1828
1829 if (se->start_block == offset) {
1830 if (bdev_p)
1831 *bdev_p = bdgrab(sis->bdev);
1832
1833 spin_unlock(&swap_lock);
1834 bdput(bdev);
1835 return type;
1836 }
1837 }
1838 }
1839 spin_unlock(&swap_lock);
1840 if (bdev)
1841 bdput(bdev);
1842
1843 return -ENODEV;
1844}
1845
1846/*
1847 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1848 * corresponding to given index in swap_info (swap type).
1849 */
1850sector_t swapdev_block(int type, pgoff_t offset)
1851{
1852 struct block_device *bdev;
1853 struct swap_info_struct *si = swap_type_to_swap_info(type);
1854
1855 if (!si || !(si->flags & SWP_WRITEOK))
1856 return 0;
1857 return map_swap_entry(swp_entry(type, offset), &bdev);
1858}
1859
1860/*
1861 * Return either the total number of swap pages of given type, or the number
1862 * of free pages of that type (depending on @free)
1863 *
1864 * This is needed for software suspend
1865 */
1866unsigned int count_swap_pages(int type, int free)
1867{
1868 unsigned int n = 0;
1869
1870 spin_lock(&swap_lock);
1871 if ((unsigned int)type < nr_swapfiles) {
1872 struct swap_info_struct *sis = swap_info[type];
1873
1874 spin_lock(&sis->lock);
1875 if (sis->flags & SWP_WRITEOK) {
1876 n = sis->pages;
1877 if (free)
1878 n -= sis->inuse_pages;
1879 }
1880 spin_unlock(&sis->lock);
1881 }
1882 spin_unlock(&swap_lock);
1883 return n;
1884}
1885#endif /* CONFIG_HIBERNATION */
1886
1887static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1888{
1889 return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte);
1890}
1891
1892/*
1893 * No need to decide whether this PTE shares the swap entry with others,
1894 * just let do_wp_page work it out if a write is requested later - to
1895 * force COW, vm_page_prot omits write permission from any private vma.
1896 */
1897static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1898 unsigned long addr, swp_entry_t entry, struct page *page)
1899{
1900 struct page *swapcache;
1901 spinlock_t *ptl;
1902 pte_t *pte;
1903 int ret = 1;
1904
1905 swapcache = page;
1906 page = ksm_might_need_to_copy(page, vma, addr);
1907 if (unlikely(!page))
1908 return -ENOMEM;
1909
1910 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1911 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1912 ret = 0;
1913 goto out;
1914 }
1915
1916 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1917 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1918 get_page(page);
1919 set_pte_at(vma->vm_mm, addr, pte,
1920 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1921 if (page == swapcache) {
1922 page_add_anon_rmap(page, vma, addr, false);
1923 } else { /* ksm created a completely new copy */
1924 page_add_new_anon_rmap(page, vma, addr, false);
1925 lru_cache_add_inactive_or_unevictable(page, vma);
1926 }
1927 swap_free(entry);
1928 /*
1929 * Move the page to the active list so it is not
1930 * immediately swapped out again after swapon.
1931 */
1932 activate_page(page);
1933out:
1934 pte_unmap_unlock(pte, ptl);
1935 if (page != swapcache) {
1936 unlock_page(page);
1937 put_page(page);
1938 }
1939 return ret;
1940}
1941
1942static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1943 unsigned long addr, unsigned long end,
1944 unsigned int type, bool frontswap,
1945 unsigned long *fs_pages_to_unuse)
1946{
1947 struct page *page;
1948 swp_entry_t entry;
1949 pte_t *pte;
1950 struct swap_info_struct *si;
1951 unsigned long offset;
1952 int ret = 0;
1953 volatile unsigned char *swap_map;
1954
1955 si = swap_info[type];
1956 pte = pte_offset_map(pmd, addr);
1957 do {
1958 struct vm_fault vmf;
1959
1960 if (!is_swap_pte(*pte))
1961 continue;
1962
1963 entry = pte_to_swp_entry(*pte);
1964 if (swp_type(entry) != type)
1965 continue;
1966
1967 offset = swp_offset(entry);
1968 if (frontswap && !frontswap_test(si, offset))
1969 continue;
1970
1971 pte_unmap(pte);
1972 swap_map = &si->swap_map[offset];
1973 page = lookup_swap_cache(entry, vma, addr);
1974 if (!page) {
1975 vmf.vma = vma;
1976 vmf.address = addr;
1977 vmf.pmd = pmd;
1978 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
1979 &vmf);
1980 }
1981 if (!page) {
1982 if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1983 goto try_next;
1984 return -ENOMEM;
1985 }
1986
1987 lock_page(page);
1988 wait_on_page_writeback(page);
1989 ret = unuse_pte(vma, pmd, addr, entry, page);
1990 if (ret < 0) {
1991 unlock_page(page);
1992 put_page(page);
1993 goto out;
1994 }
1995
1996 try_to_free_swap(page);
1997 unlock_page(page);
1998 put_page(page);
1999
2000 if (*fs_pages_to_unuse && !--(*fs_pages_to_unuse)) {
2001 ret = FRONTSWAP_PAGES_UNUSED;
2002 goto out;
2003 }
2004try_next:
2005 pte = pte_offset_map(pmd, addr);
2006 } while (pte++, addr += PAGE_SIZE, addr != end);
2007 pte_unmap(pte - 1);
2008
2009 ret = 0;
2010out:
2011 return ret;
2012}
2013
2014static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
2015 unsigned long addr, unsigned long end,
2016 unsigned int type, bool frontswap,
2017 unsigned long *fs_pages_to_unuse)
2018{
2019 pmd_t *pmd;
2020 unsigned long next;
2021 int ret;
2022
2023 pmd = pmd_offset(pud, addr);
2024 do {
2025 cond_resched();
2026 next = pmd_addr_end(addr, end);
2027 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
2028 continue;
2029 ret = unuse_pte_range(vma, pmd, addr, next, type,
2030 frontswap, fs_pages_to_unuse);
2031 if (ret)
2032 return ret;
2033 } while (pmd++, addr = next, addr != end);
2034 return 0;
2035}
2036
2037static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
2038 unsigned long addr, unsigned long end,
2039 unsigned int type, bool frontswap,
2040 unsigned long *fs_pages_to_unuse)
2041{
2042 pud_t *pud;
2043 unsigned long next;
2044 int ret;
2045
2046 pud = pud_offset(p4d, addr);
2047 do {
2048 next = pud_addr_end(addr, end);
2049 if (pud_none_or_clear_bad(pud))
2050 continue;
2051 ret = unuse_pmd_range(vma, pud, addr, next, type,
2052 frontswap, fs_pages_to_unuse);
2053 if (ret)
2054 return ret;
2055 } while (pud++, addr = next, addr != end);
2056 return 0;
2057}
2058
2059static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
2060 unsigned long addr, unsigned long end,
2061 unsigned int type, bool frontswap,
2062 unsigned long *fs_pages_to_unuse)
2063{
2064 p4d_t *p4d;
2065 unsigned long next;
2066 int ret;
2067
2068 p4d = p4d_offset(pgd, addr);
2069 do {
2070 next = p4d_addr_end(addr, end);
2071 if (p4d_none_or_clear_bad(p4d))
2072 continue;
2073 ret = unuse_pud_range(vma, p4d, addr, next, type,
2074 frontswap, fs_pages_to_unuse);
2075 if (ret)
2076 return ret;
2077 } while (p4d++, addr = next, addr != end);
2078 return 0;
2079}
2080
2081static int unuse_vma(struct vm_area_struct *vma, unsigned int type,
2082 bool frontswap, unsigned long *fs_pages_to_unuse)
2083{
2084 pgd_t *pgd;
2085 unsigned long addr, end, next;
2086 int ret;
2087
2088 addr = vma->vm_start;
2089 end = vma->vm_end;
2090
2091 pgd = pgd_offset(vma->vm_mm, addr);
2092 do {
2093 next = pgd_addr_end(addr, end);
2094 if (pgd_none_or_clear_bad(pgd))
2095 continue;
2096 ret = unuse_p4d_range(vma, pgd, addr, next, type,
2097 frontswap, fs_pages_to_unuse);
2098 if (ret)
2099 return ret;
2100 } while (pgd++, addr = next, addr != end);
2101 return 0;
2102}
2103
2104static int unuse_mm(struct mm_struct *mm, unsigned int type,
2105 bool frontswap, unsigned long *fs_pages_to_unuse)
2106{
2107 struct vm_area_struct *vma;
2108 int ret = 0;
2109
2110 mmap_read_lock(mm);
2111 for (vma = mm->mmap; vma; vma = vma->vm_next) {
2112 if (vma->anon_vma) {
2113 ret = unuse_vma(vma, type, frontswap,
2114 fs_pages_to_unuse);
2115 if (ret)
2116 break;
2117 }
2118 cond_resched();
2119 }
2120 mmap_read_unlock(mm);
2121 return ret;
2122}
2123
2124/*
2125 * Scan swap_map (or frontswap_map if frontswap parameter is true)
2126 * from current position to next entry still in use. Return 0
2127 * if there are no inuse entries after prev till end of the map.
2128 */
2129static unsigned int find_next_to_unuse(struct swap_info_struct *si,
2130 unsigned int prev, bool frontswap)
2131{
2132 unsigned int i;
2133 unsigned char count;
2134
2135 /*
2136 * No need for swap_lock here: we're just looking
2137 * for whether an entry is in use, not modifying it; false
2138 * hits are okay, and sys_swapoff() has already prevented new
2139 * allocations from this area (while holding swap_lock).
2140 */
2141 for (i = prev + 1; i < si->max; i++) {
2142 count = READ_ONCE(si->swap_map[i]);
2143 if (count && swap_count(count) != SWAP_MAP_BAD)
2144 if (!frontswap || frontswap_test(si, i))
2145 break;
2146 if ((i % LATENCY_LIMIT) == 0)
2147 cond_resched();
2148 }
2149
2150 if (i == si->max)
2151 i = 0;
2152
2153 return i;
2154}
2155
2156/*
2157 * If the boolean frontswap is true, only unuse pages_to_unuse pages;
2158 * pages_to_unuse==0 means all pages; ignored if frontswap is false
2159 */
2160int try_to_unuse(unsigned int type, bool frontswap,
2161 unsigned long pages_to_unuse)
2162{
2163 struct mm_struct *prev_mm;
2164 struct mm_struct *mm;
2165 struct list_head *p;
2166 int retval = 0;
2167 struct swap_info_struct *si = swap_info[type];
2168 struct page *page;
2169 swp_entry_t entry;
2170 unsigned int i;
2171
2172 if (!READ_ONCE(si->inuse_pages))
2173 return 0;
2174
2175 if (!frontswap)
2176 pages_to_unuse = 0;
2177
2178retry:
2179 retval = shmem_unuse(type, frontswap, &pages_to_unuse);
2180 if (retval)
2181 goto out;
2182
2183 prev_mm = &init_mm;
2184 mmget(prev_mm);
2185
2186 spin_lock(&mmlist_lock);
2187 p = &init_mm.mmlist;
2188 while (READ_ONCE(si->inuse_pages) &&
2189 !signal_pending(current) &&
2190 (p = p->next) != &init_mm.mmlist) {
2191
2192 mm = list_entry(p, struct mm_struct, mmlist);
2193 if (!mmget_not_zero(mm))
2194 continue;
2195 spin_unlock(&mmlist_lock);
2196 mmput(prev_mm);
2197 prev_mm = mm;
2198 retval = unuse_mm(mm, type, frontswap, &pages_to_unuse);
2199
2200 if (retval) {
2201 mmput(prev_mm);
2202 goto out;
2203 }
2204
2205 /*
2206 * Make sure that we aren't completely killing
2207 * interactive performance.
2208 */
2209 cond_resched();
2210 spin_lock(&mmlist_lock);
2211 }
2212 spin_unlock(&mmlist_lock);
2213
2214 mmput(prev_mm);
2215
2216 i = 0;
2217 while (READ_ONCE(si->inuse_pages) &&
2218 !signal_pending(current) &&
2219 (i = find_next_to_unuse(si, i, frontswap)) != 0) {
2220
2221 entry = swp_entry(type, i);
2222 page = find_get_page(swap_address_space(entry), i);
2223 if (!page)
2224 continue;
2225
2226 /*
2227 * It is conceivable that a racing task removed this page from
2228 * swap cache just before we acquired the page lock. The page
2229 * might even be back in swap cache on another swap area. But
2230 * that is okay, try_to_free_swap() only removes stale pages.
2231 */
2232 lock_page(page);
2233 wait_on_page_writeback(page);
2234 try_to_free_swap(page);
2235 unlock_page(page);
2236 put_page(page);
2237
2238 /*
2239 * For frontswap, we just need to unuse pages_to_unuse, if
2240 * it was specified. Need not check frontswap again here as
2241 * we already zeroed out pages_to_unuse if not frontswap.
2242 */
2243 if (pages_to_unuse && --pages_to_unuse == 0)
2244 goto out;
2245 }
2246
2247 /*
2248 * Lets check again to see if there are still swap entries in the map.
2249 * If yes, we would need to do retry the unuse logic again.
2250 * Under global memory pressure, swap entries can be reinserted back
2251 * into process space after the mmlist loop above passes over them.
2252 *
2253 * Limit the number of retries? No: when mmget_not_zero() above fails,
2254 * that mm is likely to be freeing swap from exit_mmap(), which proceeds
2255 * at its own independent pace; and even shmem_writepage() could have
2256 * been preempted after get_swap_page(), temporarily hiding that swap.
2257 * It's easy and robust (though cpu-intensive) just to keep retrying.
2258 */
2259 if (READ_ONCE(si->inuse_pages)) {
2260 if (!signal_pending(current))
2261 goto retry;
2262 retval = -EINTR;
2263 }
2264out:
2265 return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
2266}
2267
2268/*
2269 * After a successful try_to_unuse, if no swap is now in use, we know
2270 * we can empty the mmlist. swap_lock must be held on entry and exit.
2271 * Note that mmlist_lock nests inside swap_lock, and an mm must be
2272 * added to the mmlist just after page_duplicate - before would be racy.
2273 */
2274static void drain_mmlist(void)
2275{
2276 struct list_head *p, *next;
2277 unsigned int type;
2278
2279 for (type = 0; type < nr_swapfiles; type++)
2280 if (swap_info[type]->inuse_pages)
2281 return;
2282 spin_lock(&mmlist_lock);
2283 list_for_each_safe(p, next, &init_mm.mmlist)
2284 list_del_init(p);
2285 spin_unlock(&mmlist_lock);
2286}
2287
2288/*
2289 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
2290 * corresponds to page offset for the specified swap entry.
2291 * Note that the type of this function is sector_t, but it returns page offset
2292 * into the bdev, not sector offset.
2293 */
2294static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
2295{
2296 struct swap_info_struct *sis;
2297 struct swap_extent *se;
2298 pgoff_t offset;
2299
2300 sis = swp_swap_info(entry);
2301 *bdev = sis->bdev;
2302
2303 offset = swp_offset(entry);
2304 se = offset_to_swap_extent(sis, offset);
2305 return se->start_block + (offset - se->start_page);
2306}
2307
2308/*
2309 * Returns the page offset into bdev for the specified page's swap entry.
2310 */
2311sector_t map_swap_page(struct page *page, struct block_device **bdev)
2312{
2313 swp_entry_t entry;
2314 entry.val = page_private(page);
2315 return map_swap_entry(entry, bdev);
2316}
2317
2318/*
2319 * Free all of a swapdev's extent information
2320 */
2321static void destroy_swap_extents(struct swap_info_struct *sis)
2322{
2323 while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2324 struct rb_node *rb = sis->swap_extent_root.rb_node;
2325 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2326
2327 rb_erase(rb, &sis->swap_extent_root);
2328 kfree(se);
2329 }
2330
2331 if (sis->flags & SWP_ACTIVATED) {
2332 struct file *swap_file = sis->swap_file;
2333 struct address_space *mapping = swap_file->f_mapping;
2334
2335 sis->flags &= ~SWP_ACTIVATED;
2336 if (mapping->a_ops->swap_deactivate)
2337 mapping->a_ops->swap_deactivate(swap_file);
2338 }
2339}
2340
2341/*
2342 * Add a block range (and the corresponding page range) into this swapdev's
2343 * extent tree.
2344 *
2345 * This function rather assumes that it is called in ascending page order.
2346 */
2347int
2348add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2349 unsigned long nr_pages, sector_t start_block)
2350{
2351 struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2352 struct swap_extent *se;
2353 struct swap_extent *new_se;
2354
2355 /*
2356 * place the new node at the right most since the
2357 * function is called in ascending page order.
2358 */
2359 while (*link) {
2360 parent = *link;
2361 link = &parent->rb_right;
2362 }
2363
2364 if (parent) {
2365 se = rb_entry(parent, struct swap_extent, rb_node);
2366 BUG_ON(se->start_page + se->nr_pages != start_page);
2367 if (se->start_block + se->nr_pages == start_block) {
2368 /* Merge it */
2369 se->nr_pages += nr_pages;
2370 return 0;
2371 }
2372 }
2373
2374 /* No merge, insert a new extent. */
2375 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2376 if (new_se == NULL)
2377 return -ENOMEM;
2378 new_se->start_page = start_page;
2379 new_se->nr_pages = nr_pages;
2380 new_se->start_block = start_block;
2381
2382 rb_link_node(&new_se->rb_node, parent, link);
2383 rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2384 return 1;
2385}
2386EXPORT_SYMBOL_GPL(add_swap_extent);
2387
2388/*
2389 * A `swap extent' is a simple thing which maps a contiguous range of pages
2390 * onto a contiguous range of disk blocks. An ordered list of swap extents
2391 * is built at swapon time and is then used at swap_writepage/swap_readpage
2392 * time for locating where on disk a page belongs.
2393 *
2394 * If the swapfile is an S_ISBLK block device, a single extent is installed.
2395 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2396 * swap files identically.
2397 *
2398 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2399 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
2400 * swapfiles are handled *identically* after swapon time.
2401 *
2402 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2403 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
2404 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
2405 * requirements, they are simply tossed out - we will never use those blocks
2406 * for swapping.
2407 *
2408 * For all swap devices we set S_SWAPFILE across the life of the swapon. This
2409 * prevents users from writing to the swap device, which will corrupt memory.
2410 *
2411 * The amount of disk space which a single swap extent represents varies.
2412 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
2413 * extents in the list. To avoid much list walking, we cache the previous
2414 * search location in `curr_swap_extent', and start new searches from there.
2415 * This is extremely effective. The average number of iterations in
2416 * map_swap_page() has been measured at about 0.3 per page. - akpm.
2417 */
2418static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2419{
2420 struct file *swap_file = sis->swap_file;
2421 struct address_space *mapping = swap_file->f_mapping;
2422 struct inode *inode = mapping->host;
2423 int ret;
2424
2425 if (S_ISBLK(inode->i_mode)) {
2426 ret = add_swap_extent(sis, 0, sis->max, 0);
2427 *span = sis->pages;
2428 return ret;
2429 }
2430
2431 if (mapping->a_ops->swap_activate) {
2432 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2433 if (ret >= 0)
2434 sis->flags |= SWP_ACTIVATED;
2435 if (!ret) {
2436 sis->flags |= SWP_FS;
2437 ret = add_swap_extent(sis, 0, sis->max, 0);
2438 *span = sis->pages;
2439 }
2440 return ret;
2441 }
2442
2443 return generic_swapfile_activate(sis, swap_file, span);
2444}
2445
2446static int swap_node(struct swap_info_struct *p)
2447{
2448 struct block_device *bdev;
2449
2450 if (p->bdev)
2451 bdev = p->bdev;
2452 else
2453 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2454
2455 return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2456}
2457
2458static void setup_swap_info(struct swap_info_struct *p, int prio,
2459 unsigned char *swap_map,
2460 struct swap_cluster_info *cluster_info)
2461{
2462 int i;
2463
2464 if (prio >= 0)
2465 p->prio = prio;
2466 else
2467 p->prio = --least_priority;
2468 /*
2469 * the plist prio is negated because plist ordering is
2470 * low-to-high, while swap ordering is high-to-low
2471 */
2472 p->list.prio = -p->prio;
2473 for_each_node(i) {
2474 if (p->prio >= 0)
2475 p->avail_lists[i].prio = -p->prio;
2476 else {
2477 if (swap_node(p) == i)
2478 p->avail_lists[i].prio = 1;
2479 else
2480 p->avail_lists[i].prio = -p->prio;
2481 }
2482 }
2483 p->swap_map = swap_map;
2484 p->cluster_info = cluster_info;
2485}
2486
2487static void _enable_swap_info(struct swap_info_struct *p)
2488{
2489 p->flags |= SWP_WRITEOK | SWP_VALID;
2490 atomic_long_add(p->pages, &nr_swap_pages);
2491 total_swap_pages += p->pages;
2492
2493 assert_spin_locked(&swap_lock);
2494 /*
2495 * both lists are plists, and thus priority ordered.
2496 * swap_active_head needs to be priority ordered for swapoff(),
2497 * which on removal of any swap_info_struct with an auto-assigned
2498 * (i.e. negative) priority increments the auto-assigned priority
2499 * of any lower-priority swap_info_structs.
2500 * swap_avail_head needs to be priority ordered for get_swap_page(),
2501 * which allocates swap pages from the highest available priority
2502 * swap_info_struct.
2503 */
2504 plist_add(&p->list, &swap_active_head);
2505 add_to_avail_list(p);
2506}
2507
2508static void enable_swap_info(struct swap_info_struct *p, int prio,
2509 unsigned char *swap_map,
2510 struct swap_cluster_info *cluster_info,
2511 unsigned long *frontswap_map)
2512{
2513 frontswap_init(p->type, frontswap_map);
2514 spin_lock(&swap_lock);
2515 spin_lock(&p->lock);
2516 setup_swap_info(p, prio, swap_map, cluster_info);
2517 spin_unlock(&p->lock);
2518 spin_unlock(&swap_lock);
2519 /*
2520 * Guarantee swap_map, cluster_info, etc. fields are valid
2521 * between get/put_swap_device() if SWP_VALID bit is set
2522 */
2523 synchronize_rcu();
2524 spin_lock(&swap_lock);
2525 spin_lock(&p->lock);
2526 _enable_swap_info(p);
2527 spin_unlock(&p->lock);
2528 spin_unlock(&swap_lock);
2529}
2530
2531static void reinsert_swap_info(struct swap_info_struct *p)
2532{
2533 spin_lock(&swap_lock);
2534 spin_lock(&p->lock);
2535 setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2536 _enable_swap_info(p);
2537 spin_unlock(&p->lock);
2538 spin_unlock(&swap_lock);
2539}
2540
2541bool has_usable_swap(void)
2542{
2543 bool ret = true;
2544
2545 spin_lock(&swap_lock);
2546 if (plist_head_empty(&swap_active_head))
2547 ret = false;
2548 spin_unlock(&swap_lock);
2549 return ret;
2550}
2551
2552SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2553{
2554 struct swap_info_struct *p = NULL;
2555 unsigned char *swap_map;
2556 struct swap_cluster_info *cluster_info;
2557 unsigned long *frontswap_map;
2558 struct file *swap_file, *victim;
2559 struct address_space *mapping;
2560 struct inode *inode;
2561 struct filename *pathname;
2562 int err, found = 0;
2563 unsigned int old_block_size;
2564
2565 if (!capable(CAP_SYS_ADMIN))
2566 return -EPERM;
2567
2568 BUG_ON(!current->mm);
2569
2570 pathname = getname(specialfile);
2571 if (IS_ERR(pathname))
2572 return PTR_ERR(pathname);
2573
2574 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2575 err = PTR_ERR(victim);
2576 if (IS_ERR(victim))
2577 goto out;
2578
2579 mapping = victim->f_mapping;
2580 spin_lock(&swap_lock);
2581 plist_for_each_entry(p, &swap_active_head, list) {
2582 if (p->flags & SWP_WRITEOK) {
2583 if (p->swap_file->f_mapping == mapping) {
2584 found = 1;
2585 break;
2586 }
2587 }
2588 }
2589 if (!found) {
2590 err = -EINVAL;
2591 spin_unlock(&swap_lock);
2592 goto out_dput;
2593 }
2594 if (!security_vm_enough_memory_mm(current->mm, p->pages))
2595 vm_unacct_memory(p->pages);
2596 else {
2597 err = -ENOMEM;
2598 spin_unlock(&swap_lock);
2599 goto out_dput;
2600 }
2601 del_from_avail_list(p);
2602 spin_lock(&p->lock);
2603 if (p->prio < 0) {
2604 struct swap_info_struct *si = p;
2605 int nid;
2606
2607 plist_for_each_entry_continue(si, &swap_active_head, list) {
2608 si->prio++;
2609 si->list.prio--;
2610 for_each_node(nid) {
2611 if (si->avail_lists[nid].prio != 1)
2612 si->avail_lists[nid].prio--;
2613 }
2614 }
2615 least_priority++;
2616 }
2617 plist_del(&p->list, &swap_active_head);
2618 atomic_long_sub(p->pages, &nr_swap_pages);
2619 total_swap_pages -= p->pages;
2620 p->flags &= ~SWP_WRITEOK;
2621 spin_unlock(&p->lock);
2622 spin_unlock(&swap_lock);
2623
2624 disable_swap_slots_cache_lock();
2625
2626 set_current_oom_origin();
2627 err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
2628 clear_current_oom_origin();
2629
2630 if (err) {
2631 /* re-insert swap space back into swap_list */
2632 reinsert_swap_info(p);
2633 reenable_swap_slots_cache_unlock();
2634 goto out_dput;
2635 }
2636
2637 reenable_swap_slots_cache_unlock();
2638
2639 spin_lock(&swap_lock);
2640 spin_lock(&p->lock);
2641 p->flags &= ~SWP_VALID; /* mark swap device as invalid */
2642 spin_unlock(&p->lock);
2643 spin_unlock(&swap_lock);
2644 /*
2645 * wait for swap operations protected by get/put_swap_device()
2646 * to complete
2647 */
2648 synchronize_rcu();
2649
2650 flush_work(&p->discard_work);
2651
2652 destroy_swap_extents(p);
2653 if (p->flags & SWP_CONTINUED)
2654 free_swap_count_continuations(p);
2655
2656 if (!p->bdev || !blk_queue_nonrot(bdev_get_queue(p->bdev)))
2657 atomic_dec(&nr_rotate_swap);
2658
2659 mutex_lock(&swapon_mutex);
2660 spin_lock(&swap_lock);
2661 spin_lock(&p->lock);
2662 drain_mmlist();
2663
2664 /* wait for anyone still in scan_swap_map */
2665 p->highest_bit = 0; /* cuts scans short */
2666 while (p->flags >= SWP_SCANNING) {
2667 spin_unlock(&p->lock);
2668 spin_unlock(&swap_lock);
2669 schedule_timeout_uninterruptible(1);
2670 spin_lock(&swap_lock);
2671 spin_lock(&p->lock);
2672 }
2673
2674 swap_file = p->swap_file;
2675 old_block_size = p->old_block_size;
2676 p->swap_file = NULL;
2677 p->max = 0;
2678 swap_map = p->swap_map;
2679 p->swap_map = NULL;
2680 cluster_info = p->cluster_info;
2681 p->cluster_info = NULL;
2682 frontswap_map = frontswap_map_get(p);
2683 spin_unlock(&p->lock);
2684 spin_unlock(&swap_lock);
2685 frontswap_invalidate_area(p->type);
2686 frontswap_map_set(p, NULL);
2687 mutex_unlock(&swapon_mutex);
2688 free_percpu(p->percpu_cluster);
2689 p->percpu_cluster = NULL;
2690 free_percpu(p->cluster_next_cpu);
2691 p->cluster_next_cpu = NULL;
2692 vfree(swap_map);
2693 kvfree(cluster_info);
2694 kvfree(frontswap_map);
2695 /* Destroy swap account information */
2696 swap_cgroup_swapoff(p->type);
2697 exit_swap_address_space(p->type);
2698
2699 inode = mapping->host;
2700 if (S_ISBLK(inode->i_mode)) {
2701 struct block_device *bdev = I_BDEV(inode);
2702
2703 set_blocksize(bdev, old_block_size);
2704 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2705 }
2706
2707 inode_lock(inode);
2708 inode->i_flags &= ~S_SWAPFILE;
2709 inode_unlock(inode);
2710 filp_close(swap_file, NULL);
2711
2712 /*
2713 * Clear the SWP_USED flag after all resources are freed so that swapon
2714 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
2715 * not hold p->lock after we cleared its SWP_WRITEOK.
2716 */
2717 spin_lock(&swap_lock);
2718 p->flags = 0;
2719 spin_unlock(&swap_lock);
2720
2721 err = 0;
2722 atomic_inc(&proc_poll_event);
2723 wake_up_interruptible(&proc_poll_wait);
2724
2725out_dput:
2726 filp_close(victim, NULL);
2727out:
2728 putname(pathname);
2729 return err;
2730}
2731
2732#ifdef CONFIG_PROC_FS
2733static __poll_t swaps_poll(struct file *file, poll_table *wait)
2734{
2735 struct seq_file *seq = file->private_data;
2736
2737 poll_wait(file, &proc_poll_wait, wait);
2738
2739 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2740 seq->poll_event = atomic_read(&proc_poll_event);
2741 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2742 }
2743
2744 return EPOLLIN | EPOLLRDNORM;
2745}
2746
2747/* iterator */
2748static void *swap_start(struct seq_file *swap, loff_t *pos)
2749{
2750 struct swap_info_struct *si;
2751 int type;
2752 loff_t l = *pos;
2753
2754 mutex_lock(&swapon_mutex);
2755
2756 if (!l)
2757 return SEQ_START_TOKEN;
2758
2759 for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2760 if (!(si->flags & SWP_USED) || !si->swap_map)
2761 continue;
2762 if (!--l)
2763 return si;
2764 }
2765
2766 return NULL;
2767}
2768
2769static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2770{
2771 struct swap_info_struct *si = v;
2772 int type;
2773
2774 if (v == SEQ_START_TOKEN)
2775 type = 0;
2776 else
2777 type = si->type + 1;
2778
2779 ++(*pos);
2780 for (; (si = swap_type_to_swap_info(type)); type++) {
2781 if (!(si->flags & SWP_USED) || !si->swap_map)
2782 continue;
2783 return si;
2784 }
2785
2786 return NULL;
2787}
2788
2789static void swap_stop(struct seq_file *swap, void *v)
2790{
2791 mutex_unlock(&swapon_mutex);
2792}
2793
2794static int swap_show(struct seq_file *swap, void *v)
2795{
2796 struct swap_info_struct *si = v;
2797 struct file *file;
2798 int len;
2799 unsigned int bytes, inuse;
2800
2801 if (si == SEQ_START_TOKEN) {
2802 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2803 return 0;
2804 }
2805
2806 bytes = si->pages << (PAGE_SHIFT - 10);
2807 inuse = si->inuse_pages << (PAGE_SHIFT - 10);
2808
2809 file = si->swap_file;
2810 len = seq_file_path(swap, file, " \t\n\\");
2811 seq_printf(swap, "%*s%s\t%u\t%s%u\t%s%d\n",
2812 len < 40 ? 40 - len : 1, " ",
2813 S_ISBLK(file_inode(file)->i_mode) ?
2814 "partition" : "file\t",
2815 bytes, bytes < 10000000 ? "\t" : "",
2816 inuse, inuse < 10000000 ? "\t" : "",
2817 si->prio);
2818 return 0;
2819}
2820
2821static const struct seq_operations swaps_op = {
2822 .start = swap_start,
2823 .next = swap_next,
2824 .stop = swap_stop,
2825 .show = swap_show
2826};
2827
2828static int swaps_open(struct inode *inode, struct file *file)
2829{
2830 struct seq_file *seq;
2831 int ret;
2832
2833 ret = seq_open(file, &swaps_op);
2834 if (ret)
2835 return ret;
2836
2837 seq = file->private_data;
2838 seq->poll_event = atomic_read(&proc_poll_event);
2839 return 0;
2840}
2841
2842static const struct proc_ops swaps_proc_ops = {
2843 .proc_flags = PROC_ENTRY_PERMANENT,
2844 .proc_open = swaps_open,
2845 .proc_read = seq_read,
2846 .proc_lseek = seq_lseek,
2847 .proc_release = seq_release,
2848 .proc_poll = swaps_poll,
2849};
2850
2851static int __init procswaps_init(void)
2852{
2853 proc_create("swaps", 0, NULL, &swaps_proc_ops);
2854 return 0;
2855}
2856__initcall(procswaps_init);
2857#endif /* CONFIG_PROC_FS */
2858
2859#ifdef MAX_SWAPFILES_CHECK
2860static int __init max_swapfiles_check(void)
2861{
2862 MAX_SWAPFILES_CHECK();
2863 return 0;
2864}
2865late_initcall(max_swapfiles_check);
2866#endif
2867
2868static struct swap_info_struct *alloc_swap_info(void)
2869{
2870 struct swap_info_struct *p;
2871 unsigned int type;
2872 int i;
2873
2874 p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2875 if (!p)
2876 return ERR_PTR(-ENOMEM);
2877
2878 spin_lock(&swap_lock);
2879 for (type = 0; type < nr_swapfiles; type++) {
2880 if (!(swap_info[type]->flags & SWP_USED))
2881 break;
2882 }
2883 if (type >= MAX_SWAPFILES) {
2884 spin_unlock(&swap_lock);
2885 kvfree(p);
2886 return ERR_PTR(-EPERM);
2887 }
2888 if (type >= nr_swapfiles) {
2889 p->type = type;
2890 WRITE_ONCE(swap_info[type], p);
2891 /*
2892 * Write swap_info[type] before nr_swapfiles, in case a
2893 * racing procfs swap_start() or swap_next() is reading them.
2894 * (We never shrink nr_swapfiles, we never free this entry.)
2895 */
2896 smp_wmb();
2897 WRITE_ONCE(nr_swapfiles, nr_swapfiles + 1);
2898 } else {
2899 kvfree(p);
2900 p = swap_info[type];
2901 /*
2902 * Do not memset this entry: a racing procfs swap_next()
2903 * would be relying on p->type to remain valid.
2904 */
2905 }
2906 p->swap_extent_root = RB_ROOT;
2907 plist_node_init(&p->list, 0);
2908 for_each_node(i)
2909 plist_node_init(&p->avail_lists[i], 0);
2910 p->flags = SWP_USED;
2911 spin_unlock(&swap_lock);
2912 spin_lock_init(&p->lock);
2913 spin_lock_init(&p->cont_lock);
2914
2915 return p;
2916}
2917
2918static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2919{
2920 int error;
2921
2922 if (S_ISBLK(inode->i_mode)) {
2923 p->bdev = bdgrab(I_BDEV(inode));
2924 error = blkdev_get(p->bdev,
2925 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2926 if (error < 0) {
2927 p->bdev = NULL;
2928 return error;
2929 }
2930 p->old_block_size = block_size(p->bdev);
2931 error = set_blocksize(p->bdev, PAGE_SIZE);
2932 if (error < 0)
2933 return error;
2934 /*
2935 * Zoned block devices contain zones that have a sequential
2936 * write only restriction. Hence zoned block devices are not
2937 * suitable for swapping. Disallow them here.
2938 */
2939 if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
2940 return -EINVAL;
2941 p->flags |= SWP_BLKDEV;
2942 } else if (S_ISREG(inode->i_mode)) {
2943 p->bdev = inode->i_sb->s_bdev;
2944 }
2945
2946 return 0;
2947}
2948
2949
2950/*
2951 * Find out how many pages are allowed for a single swap device. There
2952 * are two limiting factors:
2953 * 1) the number of bits for the swap offset in the swp_entry_t type, and
2954 * 2) the number of bits in the swap pte, as defined by the different
2955 * architectures.
2956 *
2957 * In order to find the largest possible bit mask, a swap entry with
2958 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2959 * decoded to a swp_entry_t again, and finally the swap offset is
2960 * extracted.
2961 *
2962 * This will mask all the bits from the initial ~0UL mask that can't
2963 * be encoded in either the swp_entry_t or the architecture definition
2964 * of a swap pte.
2965 */
2966unsigned long generic_max_swapfile_size(void)
2967{
2968 return swp_offset(pte_to_swp_entry(
2969 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2970}
2971
2972/* Can be overridden by an architecture for additional checks. */
2973__weak unsigned long max_swapfile_size(void)
2974{
2975 return generic_max_swapfile_size();
2976}
2977
2978static unsigned long read_swap_header(struct swap_info_struct *p,
2979 union swap_header *swap_header,
2980 struct inode *inode)
2981{
2982 int i;
2983 unsigned long maxpages;
2984 unsigned long swapfilepages;
2985 unsigned long last_page;
2986
2987 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2988 pr_err("Unable to find swap-space signature\n");
2989 return 0;
2990 }
2991
2992 /* swap partition endianess hack... */
2993 if (swab32(swap_header->info.version) == 1) {
2994 swab32s(&swap_header->info.version);
2995 swab32s(&swap_header->info.last_page);
2996 swab32s(&swap_header->info.nr_badpages);
2997 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2998 return 0;
2999 for (i = 0; i < swap_header->info.nr_badpages; i++)
3000 swab32s(&swap_header->info.badpages[i]);
3001 }
3002 /* Check the swap header's sub-version */
3003 if (swap_header->info.version != 1) {
3004 pr_warn("Unable to handle swap header version %d\n",
3005 swap_header->info.version);
3006 return 0;
3007 }
3008
3009 p->lowest_bit = 1;
3010 p->cluster_next = 1;
3011 p->cluster_nr = 0;
3012
3013 maxpages = max_swapfile_size();
3014 last_page = swap_header->info.last_page;
3015 if (!last_page) {
3016 pr_warn("Empty swap-file\n");
3017 return 0;
3018 }
3019 if (last_page > maxpages) {
3020 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
3021 maxpages << (PAGE_SHIFT - 10),
3022 last_page << (PAGE_SHIFT - 10));
3023 }
3024 if (maxpages > last_page) {
3025 maxpages = last_page + 1;
3026 /* p->max is an unsigned int: don't overflow it */
3027 if ((unsigned int)maxpages == 0)
3028 maxpages = UINT_MAX;
3029 }
3030 p->highest_bit = maxpages - 1;
3031
3032 if (!maxpages)
3033 return 0;
3034 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
3035 if (swapfilepages && maxpages > swapfilepages) {
3036 pr_warn("Swap area shorter than signature indicates\n");
3037 return 0;
3038 }
3039 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
3040 return 0;
3041 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
3042 return 0;
3043
3044 return maxpages;
3045}
3046
3047#define SWAP_CLUSTER_INFO_COLS \
3048 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
3049#define SWAP_CLUSTER_SPACE_COLS \
3050 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
3051#define SWAP_CLUSTER_COLS \
3052 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
3053
3054static int setup_swap_map_and_extents(struct swap_info_struct *p,
3055 union swap_header *swap_header,
3056 unsigned char *swap_map,
3057 struct swap_cluster_info *cluster_info,
3058 unsigned long maxpages,
3059 sector_t *span)
3060{
3061 unsigned int j, k;
3062 unsigned int nr_good_pages;
3063 int nr_extents;
3064 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3065 unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
3066 unsigned long i, idx;
3067
3068 nr_good_pages = maxpages - 1; /* omit header page */
3069
3070 cluster_list_init(&p->free_clusters);
3071 cluster_list_init(&p->discard_clusters);
3072
3073 for (i = 0; i < swap_header->info.nr_badpages; i++) {
3074 unsigned int page_nr = swap_header->info.badpages[i];
3075 if (page_nr == 0 || page_nr > swap_header->info.last_page)
3076 return -EINVAL;
3077 if (page_nr < maxpages) {
3078 swap_map[page_nr] = SWAP_MAP_BAD;
3079 nr_good_pages--;
3080 /*
3081 * Haven't marked the cluster free yet, no list
3082 * operation involved
3083 */
3084 inc_cluster_info_page(p, cluster_info, page_nr);
3085 }
3086 }
3087
3088 /* Haven't marked the cluster free yet, no list operation involved */
3089 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
3090 inc_cluster_info_page(p, cluster_info, i);
3091
3092 if (nr_good_pages) {
3093 swap_map[0] = SWAP_MAP_BAD;
3094 /*
3095 * Not mark the cluster free yet, no list
3096 * operation involved
3097 */
3098 inc_cluster_info_page(p, cluster_info, 0);
3099 p->max = maxpages;
3100 p->pages = nr_good_pages;
3101 nr_extents = setup_swap_extents(p, span);
3102 if (nr_extents < 0)
3103 return nr_extents;
3104 nr_good_pages = p->pages;
3105 }
3106 if (!nr_good_pages) {
3107 pr_warn("Empty swap-file\n");
3108 return -EINVAL;
3109 }
3110
3111 if (!cluster_info)
3112 return nr_extents;
3113
3114
3115 /*
3116 * Reduce false cache line sharing between cluster_info and
3117 * sharing same address space.
3118 */
3119 for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
3120 j = (k + col) % SWAP_CLUSTER_COLS;
3121 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
3122 idx = i * SWAP_CLUSTER_COLS + j;
3123 if (idx >= nr_clusters)
3124 continue;
3125 if (cluster_count(&cluster_info[idx]))
3126 continue;
3127 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
3128 cluster_list_add_tail(&p->free_clusters, cluster_info,
3129 idx);
3130 }
3131 }
3132 return nr_extents;
3133}
3134
3135/*
3136 * Helper to sys_swapon determining if a given swap
3137 * backing device queue supports DISCARD operations.
3138 */
3139static bool swap_discardable(struct swap_info_struct *si)
3140{
3141 struct request_queue *q = bdev_get_queue(si->bdev);
3142
3143 if (!q || !blk_queue_discard(q))
3144 return false;
3145
3146 return true;
3147}
3148
3149SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
3150{
3151 struct swap_info_struct *p;
3152 struct filename *name;
3153 struct file *swap_file = NULL;
3154 struct address_space *mapping;
3155 int prio;
3156 int error;
3157 union swap_header *swap_header;
3158 int nr_extents;
3159 sector_t span;
3160 unsigned long maxpages;
3161 unsigned char *swap_map = NULL;
3162 struct swap_cluster_info *cluster_info = NULL;
3163 unsigned long *frontswap_map = NULL;
3164 struct page *page = NULL;
3165 struct inode *inode = NULL;
3166 bool inced_nr_rotate_swap = false;
3167
3168 if (swap_flags & ~SWAP_FLAGS_VALID)
3169 return -EINVAL;
3170
3171 if (!capable(CAP_SYS_ADMIN))
3172 return -EPERM;
3173
3174 if (!swap_avail_heads)
3175 return -ENOMEM;
3176
3177 p = alloc_swap_info();
3178 if (IS_ERR(p))
3179 return PTR_ERR(p);
3180
3181 INIT_WORK(&p->discard_work, swap_discard_work);
3182
3183 name = getname(specialfile);
3184 if (IS_ERR(name)) {
3185 error = PTR_ERR(name);
3186 name = NULL;
3187 goto bad_swap;
3188 }
3189 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3190 if (IS_ERR(swap_file)) {
3191 error = PTR_ERR(swap_file);
3192 swap_file = NULL;
3193 goto bad_swap;
3194 }
3195
3196 p->swap_file = swap_file;
3197 mapping = swap_file->f_mapping;
3198 inode = mapping->host;
3199
3200 error = claim_swapfile(p, inode);
3201 if (unlikely(error))
3202 goto bad_swap;
3203
3204 inode_lock(inode);
3205 if (IS_SWAPFILE(inode)) {
3206 error = -EBUSY;
3207 goto bad_swap_unlock_inode;
3208 }
3209
3210 /*
3211 * Read the swap header.
3212 */
3213 if (!mapping->a_ops->readpage) {
3214 error = -EINVAL;
3215 goto bad_swap_unlock_inode;
3216 }
3217 page = read_mapping_page(mapping, 0, swap_file);
3218 if (IS_ERR(page)) {
3219 error = PTR_ERR(page);
3220 goto bad_swap_unlock_inode;
3221 }
3222 swap_header = kmap(page);
3223
3224 maxpages = read_swap_header(p, swap_header, inode);
3225 if (unlikely(!maxpages)) {
3226 error = -EINVAL;
3227 goto bad_swap_unlock_inode;
3228 }
3229
3230 /* OK, set up the swap map and apply the bad block list */
3231 swap_map = vzalloc(maxpages);
3232 if (!swap_map) {
3233 error = -ENOMEM;
3234 goto bad_swap_unlock_inode;
3235 }
3236
3237 if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))
3238 p->flags |= SWP_STABLE_WRITES;
3239
3240 if (bdi_cap_synchronous_io(inode_to_bdi(inode)))
3241 p->flags |= SWP_SYNCHRONOUS_IO;
3242
3243 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
3244 int cpu;
3245 unsigned long ci, nr_cluster;
3246
3247 p->flags |= SWP_SOLIDSTATE;
3248 p->cluster_next_cpu = alloc_percpu(unsigned int);
3249 if (!p->cluster_next_cpu) {
3250 error = -ENOMEM;
3251 goto bad_swap_unlock_inode;
3252 }
3253 /*
3254 * select a random position to start with to help wear leveling
3255 * SSD
3256 */
3257 for_each_possible_cpu(cpu) {
3258 per_cpu(*p->cluster_next_cpu, cpu) =
3259 1 + prandom_u32_max(p->highest_bit);
3260 }
3261 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3262
3263 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3264 GFP_KERNEL);
3265 if (!cluster_info) {
3266 error = -ENOMEM;
3267 goto bad_swap_unlock_inode;
3268 }
3269
3270 for (ci = 0; ci < nr_cluster; ci++)
3271 spin_lock_init(&((cluster_info + ci)->lock));
3272
3273 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3274 if (!p->percpu_cluster) {
3275 error = -ENOMEM;
3276 goto bad_swap_unlock_inode;
3277 }
3278 for_each_possible_cpu(cpu) {
3279 struct percpu_cluster *cluster;
3280 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3281 cluster_set_null(&cluster->index);
3282 }
3283 } else {
3284 atomic_inc(&nr_rotate_swap);
3285 inced_nr_rotate_swap = true;
3286 }
3287
3288 error = swap_cgroup_swapon(p->type, maxpages);
3289 if (error)
3290 goto bad_swap_unlock_inode;
3291
3292 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3293 cluster_info, maxpages, &span);
3294 if (unlikely(nr_extents < 0)) {
3295 error = nr_extents;
3296 goto bad_swap_unlock_inode;
3297 }
3298 /* frontswap enabled? set up bit-per-page map for frontswap */
3299 if (IS_ENABLED(CONFIG_FRONTSWAP))
3300 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3301 sizeof(long),
3302 GFP_KERNEL);
3303
3304 if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
3305 /*
3306 * When discard is enabled for swap with no particular
3307 * policy flagged, we set all swap discard flags here in
3308 * order to sustain backward compatibility with older
3309 * swapon(8) releases.
3310 */
3311 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3312 SWP_PAGE_DISCARD);
3313
3314 /*
3315 * By flagging sys_swapon, a sysadmin can tell us to
3316 * either do single-time area discards only, or to just
3317 * perform discards for released swap page-clusters.
3318 * Now it's time to adjust the p->flags accordingly.
3319 */
3320 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3321 p->flags &= ~SWP_PAGE_DISCARD;
3322 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3323 p->flags &= ~SWP_AREA_DISCARD;
3324
3325 /* issue a swapon-time discard if it's still required */
3326 if (p->flags & SWP_AREA_DISCARD) {
3327 int err = discard_swap(p);
3328 if (unlikely(err))
3329 pr_err("swapon: discard_swap(%p): %d\n",
3330 p, err);
3331 }
3332 }
3333
3334 error = init_swap_address_space(p->type, maxpages);
3335 if (error)
3336 goto bad_swap_unlock_inode;
3337
3338 /*
3339 * Flush any pending IO and dirty mappings before we start using this
3340 * swap device.
3341 */
3342 inode->i_flags |= S_SWAPFILE;
3343 error = inode_drain_writes(inode);
3344 if (error) {
3345 inode->i_flags &= ~S_SWAPFILE;
3346 goto bad_swap_unlock_inode;
3347 }
3348
3349 mutex_lock(&swapon_mutex);
3350 prio = -1;
3351 if (swap_flags & SWAP_FLAG_PREFER)
3352 prio =
3353 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3354 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3355
3356 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3357 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3358 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3359 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3360 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3361 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3362 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3363 (frontswap_map) ? "FS" : "");
3364
3365 mutex_unlock(&swapon_mutex);
3366 atomic_inc(&proc_poll_event);
3367 wake_up_interruptible(&proc_poll_wait);
3368
3369 error = 0;
3370 goto out;
3371bad_swap_unlock_inode:
3372 inode_unlock(inode);
3373bad_swap:
3374 free_percpu(p->percpu_cluster);
3375 p->percpu_cluster = NULL;
3376 free_percpu(p->cluster_next_cpu);
3377 p->cluster_next_cpu = NULL;
3378 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3379 set_blocksize(p->bdev, p->old_block_size);
3380 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3381 }
3382 inode = NULL;
3383 destroy_swap_extents(p);
3384 swap_cgroup_swapoff(p->type);
3385 spin_lock(&swap_lock);
3386 p->swap_file = NULL;
3387 p->flags = 0;
3388 spin_unlock(&swap_lock);
3389 vfree(swap_map);
3390 kvfree(cluster_info);
3391 kvfree(frontswap_map);
3392 if (inced_nr_rotate_swap)
3393 atomic_dec(&nr_rotate_swap);
3394 if (swap_file)
3395 filp_close(swap_file, NULL);
3396out:
3397 if (page && !IS_ERR(page)) {
3398 kunmap(page);
3399 put_page(page);
3400 }
3401 if (name)
3402 putname(name);
3403 if (inode)
3404 inode_unlock(inode);
3405 if (!error)
3406 enable_swap_slots_cache();
3407 return error;
3408}
3409
3410void si_swapinfo(struct sysinfo *val)
3411{
3412 unsigned int type;
3413 unsigned long nr_to_be_unused = 0;
3414
3415 spin_lock(&swap_lock);
3416 for (type = 0; type < nr_swapfiles; type++) {
3417 struct swap_info_struct *si = swap_info[type];
3418
3419 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3420 nr_to_be_unused += si->inuse_pages;
3421 }
3422 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3423 val->totalswap = total_swap_pages + nr_to_be_unused;
3424 spin_unlock(&swap_lock);
3425}
3426
3427/*
3428 * Verify that a swap entry is valid and increment its swap map count.
3429 *
3430 * Returns error code in following case.
3431 * - success -> 0
3432 * - swp_entry is invalid -> EINVAL
3433 * - swp_entry is migration entry -> EINVAL
3434 * - swap-cache reference is requested but there is already one. -> EEXIST
3435 * - swap-cache reference is requested but the entry is not used. -> ENOENT
3436 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3437 */
3438static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3439{
3440 struct swap_info_struct *p;
3441 struct swap_cluster_info *ci;
3442 unsigned long offset;
3443 unsigned char count;
3444 unsigned char has_cache;
3445 int err = -EINVAL;
3446
3447 p = get_swap_device(entry);
3448 if (!p)
3449 goto out;
3450
3451 offset = swp_offset(entry);
3452 ci = lock_cluster_or_swap_info(p, offset);
3453
3454 count = p->swap_map[offset];
3455
3456 /*
3457 * swapin_readahead() doesn't check if a swap entry is valid, so the
3458 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3459 */
3460 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3461 err = -ENOENT;
3462 goto unlock_out;
3463 }
3464
3465 has_cache = count & SWAP_HAS_CACHE;
3466 count &= ~SWAP_HAS_CACHE;
3467 err = 0;
3468
3469 if (usage == SWAP_HAS_CACHE) {
3470
3471 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3472 if (!has_cache && count)
3473 has_cache = SWAP_HAS_CACHE;
3474 else if (has_cache) /* someone else added cache */
3475 err = -EEXIST;
3476 else /* no users remaining */
3477 err = -ENOENT;
3478
3479 } else if (count || has_cache) {
3480
3481 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3482 count += usage;
3483 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3484 err = -EINVAL;
3485 else if (swap_count_continued(p, offset, count))
3486 count = COUNT_CONTINUED;
3487 else
3488 err = -ENOMEM;
3489 } else
3490 err = -ENOENT; /* unused swap entry */
3491
3492 WRITE_ONCE(p->swap_map[offset], count | has_cache);
3493
3494unlock_out:
3495 unlock_cluster_or_swap_info(p, ci);
3496out:
3497 if (p)
3498 put_swap_device(p);
3499 return err;
3500}
3501
3502/*
3503 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3504 * (in which case its reference count is never incremented).
3505 */
3506void swap_shmem_alloc(swp_entry_t entry)
3507{
3508 __swap_duplicate(entry, SWAP_MAP_SHMEM);
3509}
3510
3511/*
3512 * Increase reference count of swap entry by 1.
3513 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3514 * but could not be atomically allocated. Returns 0, just as if it succeeded,
3515 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3516 * might occur if a page table entry has got corrupted.
3517 */
3518int swap_duplicate(swp_entry_t entry)
3519{
3520 int err = 0;
3521
3522 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3523 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3524 return err;
3525}
3526
3527/*
3528 * @entry: swap entry for which we allocate swap cache.
3529 *
3530 * Called when allocating swap cache for existing swap entry,
3531 * This can return error codes. Returns 0 at success.
3532 * -EEXIST means there is a swap cache.
3533 * Note: return code is different from swap_duplicate().
3534 */
3535int swapcache_prepare(swp_entry_t entry)
3536{
3537 return __swap_duplicate(entry, SWAP_HAS_CACHE);
3538}
3539
3540struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3541{
3542 return swap_type_to_swap_info(swp_type(entry));
3543}
3544
3545struct swap_info_struct *page_swap_info(struct page *page)
3546{
3547 swp_entry_t entry = { .val = page_private(page) };
3548 return swp_swap_info(entry);
3549}
3550
3551/*
3552 * out-of-line __page_file_ methods to avoid include hell.
3553 */
3554struct address_space *__page_file_mapping(struct page *page)
3555{
3556 return page_swap_info(page)->swap_file->f_mapping;
3557}
3558EXPORT_SYMBOL_GPL(__page_file_mapping);
3559
3560pgoff_t __page_file_index(struct page *page)
3561{
3562 swp_entry_t swap = { .val = page_private(page) };
3563 return swp_offset(swap);
3564}
3565EXPORT_SYMBOL_GPL(__page_file_index);
3566
3567/*
3568 * add_swap_count_continuation - called when a swap count is duplicated
3569 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3570 * page of the original vmalloc'ed swap_map, to hold the continuation count
3571 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
3572 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3573 *
3574 * These continuation pages are seldom referenced: the common paths all work
3575 * on the original swap_map, only referring to a continuation page when the
3576 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3577 *
3578 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3579 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3580 * can be called after dropping locks.
3581 */
3582int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3583{
3584 struct swap_info_struct *si;
3585 struct swap_cluster_info *ci;
3586 struct page *head;
3587 struct page *page;
3588 struct page *list_page;
3589 pgoff_t offset;
3590 unsigned char count;
3591 int ret = 0;
3592
3593 /*
3594 * When debugging, it's easier to use __GFP_ZERO here; but it's better
3595 * for latency not to zero a page while GFP_ATOMIC and holding locks.
3596 */
3597 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3598
3599 si = get_swap_device(entry);
3600 if (!si) {
3601 /*
3602 * An acceptable race has occurred since the failing
3603 * __swap_duplicate(): the swap device may be swapoff
3604 */
3605 goto outer;
3606 }
3607 spin_lock(&si->lock);
3608
3609 offset = swp_offset(entry);
3610
3611 ci = lock_cluster(si, offset);
3612
3613 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
3614
3615 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3616 /*
3617 * The higher the swap count, the more likely it is that tasks
3618 * will race to add swap count continuation: we need to avoid
3619 * over-provisioning.
3620 */
3621 goto out;
3622 }
3623
3624 if (!page) {
3625 ret = -ENOMEM;
3626 goto out;
3627 }
3628
3629 /*
3630 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3631 * no architecture is using highmem pages for kernel page tables: so it
3632 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3633 */
3634 head = vmalloc_to_page(si->swap_map + offset);
3635 offset &= ~PAGE_MASK;
3636
3637 spin_lock(&si->cont_lock);
3638 /*
3639 * Page allocation does not initialize the page's lru field,
3640 * but it does always reset its private field.
3641 */
3642 if (!page_private(head)) {
3643 BUG_ON(count & COUNT_CONTINUED);
3644 INIT_LIST_HEAD(&head->lru);
3645 set_page_private(head, SWP_CONTINUED);
3646 si->flags |= SWP_CONTINUED;
3647 }
3648
3649 list_for_each_entry(list_page, &head->lru, lru) {
3650 unsigned char *map;
3651
3652 /*
3653 * If the previous map said no continuation, but we've found
3654 * a continuation page, free our allocation and use this one.
3655 */
3656 if (!(count & COUNT_CONTINUED))
3657 goto out_unlock_cont;
3658
3659 map = kmap_atomic(list_page) + offset;
3660 count = *map;
3661 kunmap_atomic(map);
3662
3663 /*
3664 * If this continuation count now has some space in it,
3665 * free our allocation and use this one.
3666 */
3667 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3668 goto out_unlock_cont;
3669 }
3670
3671 list_add_tail(&page->lru, &head->lru);
3672 page = NULL; /* now it's attached, don't free it */
3673out_unlock_cont:
3674 spin_unlock(&si->cont_lock);
3675out:
3676 unlock_cluster(ci);
3677 spin_unlock(&si->lock);
3678 put_swap_device(si);
3679outer:
3680 if (page)
3681 __free_page(page);
3682 return ret;
3683}
3684
3685/*
3686 * swap_count_continued - when the original swap_map count is incremented
3687 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3688 * into, carry if so, or else fail until a new continuation page is allocated;
3689 * when the original swap_map count is decremented from 0 with continuation,
3690 * borrow from the continuation and report whether it still holds more.
3691 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3692 * lock.
3693 */
3694static bool swap_count_continued(struct swap_info_struct *si,
3695 pgoff_t offset, unsigned char count)
3696{
3697 struct page *head;
3698 struct page *page;
3699 unsigned char *map;
3700 bool ret;
3701
3702 head = vmalloc_to_page(si->swap_map + offset);
3703 if (page_private(head) != SWP_CONTINUED) {
3704 BUG_ON(count & COUNT_CONTINUED);
3705 return false; /* need to add count continuation */
3706 }
3707
3708 spin_lock(&si->cont_lock);
3709 offset &= ~PAGE_MASK;
3710 page = list_next_entry(head, lru);
3711 map = kmap_atomic(page) + offset;
3712
3713 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
3714 goto init_map; /* jump over SWAP_CONT_MAX checks */
3715
3716 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3717 /*
3718 * Think of how you add 1 to 999
3719 */
3720 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3721 kunmap_atomic(map);
3722 page = list_next_entry(page, lru);
3723 BUG_ON(page == head);
3724 map = kmap_atomic(page) + offset;
3725 }
3726 if (*map == SWAP_CONT_MAX) {
3727 kunmap_atomic(map);
3728 page = list_next_entry(page, lru);
3729 if (page == head) {
3730 ret = false; /* add count continuation */
3731 goto out;
3732 }
3733 map = kmap_atomic(page) + offset;
3734init_map: *map = 0; /* we didn't zero the page */
3735 }
3736 *map += 1;
3737 kunmap_atomic(map);
3738 while ((page = list_prev_entry(page, lru)) != head) {
3739 map = kmap_atomic(page) + offset;
3740 *map = COUNT_CONTINUED;
3741 kunmap_atomic(map);
3742 }
3743 ret = true; /* incremented */
3744
3745 } else { /* decrementing */
3746 /*
3747 * Think of how you subtract 1 from 1000
3748 */
3749 BUG_ON(count != COUNT_CONTINUED);
3750 while (*map == COUNT_CONTINUED) {
3751 kunmap_atomic(map);
3752 page = list_next_entry(page, lru);
3753 BUG_ON(page == head);
3754 map = kmap_atomic(page) + offset;
3755 }
3756 BUG_ON(*map == 0);
3757 *map -= 1;
3758 if (*map == 0)
3759 count = 0;
3760 kunmap_atomic(map);
3761 while ((page = list_prev_entry(page, lru)) != head) {
3762 map = kmap_atomic(page) + offset;
3763 *map = SWAP_CONT_MAX | count;
3764 count = COUNT_CONTINUED;
3765 kunmap_atomic(map);
3766 }
3767 ret = count == COUNT_CONTINUED;
3768 }
3769out:
3770 spin_unlock(&si->cont_lock);
3771 return ret;
3772}
3773
3774/*
3775 * free_swap_count_continuations - swapoff free all the continuation pages
3776 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3777 */
3778static void free_swap_count_continuations(struct swap_info_struct *si)
3779{
3780 pgoff_t offset;
3781
3782 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3783 struct page *head;
3784 head = vmalloc_to_page(si->swap_map + offset);
3785 if (page_private(head)) {
3786 struct page *page, *next;
3787
3788 list_for_each_entry_safe(page, next, &head->lru, lru) {
3789 list_del(&page->lru);
3790 __free_page(page);
3791 }
3792 }
3793 }
3794}
3795
3796#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3797void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
3798{
3799 struct swap_info_struct *si, *next;
3800 int nid = page_to_nid(page);
3801
3802 if (!(gfp_mask & __GFP_IO))
3803 return;
3804
3805 if (!blk_cgroup_congested())
3806 return;
3807
3808 /*
3809 * We've already scheduled a throttle, avoid taking the global swap
3810 * lock.
3811 */
3812 if (current->throttle_queue)
3813 return;
3814
3815 spin_lock(&swap_avail_lock);
3816 plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
3817 avail_lists[nid]) {
3818 if (si->bdev) {
3819 blkcg_schedule_throttle(bdev_get_queue(si->bdev), true);
3820 break;
3821 }
3822 }
3823 spin_unlock(&swap_avail_lock);
3824}
3825#endif
3826
3827static int __init swapfile_init(void)
3828{
3829 int nid;
3830
3831 swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3832 GFP_KERNEL);
3833 if (!swap_avail_heads) {
3834 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3835 return -ENOMEM;
3836 }
3837
3838 for_each_node(nid)
3839 plist_head_init(&swap_avail_heads[nid]);
3840
3841 return 0;
3842}
3843subsys_initcall(swapfile_init);