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