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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), swp_offset(entry));
109 if (!page)
110 return 0;
111 /*
112 * This function is called from scan_swap_map() and it's called
113 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
114 * We have to use trylock for avoiding deadlock. This is a special
115 * case and you should use try_to_free_swap() with explicit lock_page()
116 * in usual operations.
117 */
118 if (trylock_page(page)) {
119 ret = try_to_free_swap(page);
120 unlock_page(page);
121 }
122 put_page(page);
123 return ret;
124}
125
126/*
127 * swapon tell device that all the old swap contents can be discarded,
128 * to allow the swap device to optimize its wear-levelling.
129 */
130static int discard_swap(struct swap_info_struct *si)
131{
132 struct swap_extent *se;
133 sector_t start_block;
134 sector_t nr_blocks;
135 int err = 0;
136
137 /* Do not discard the swap header page! */
138 se = &si->first_swap_extent;
139 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
140 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
141 if (nr_blocks) {
142 err = blkdev_issue_discard(si->bdev, start_block,
143 nr_blocks, GFP_KERNEL, 0);
144 if (err)
145 return err;
146 cond_resched();
147 }
148
149 list_for_each_entry(se, &si->first_swap_extent.list, list) {
150 start_block = se->start_block << (PAGE_SHIFT - 9);
151 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
152
153 err = blkdev_issue_discard(si->bdev, start_block,
154 nr_blocks, GFP_KERNEL, 0);
155 if (err)
156 break;
157
158 cond_resched();
159 }
160 return err; /* That will often be -EOPNOTSUPP */
161}
162
163/*
164 * swap allocation tell device that a cluster of swap can now be discarded,
165 * to allow the swap device to optimize its wear-levelling.
166 */
167static void discard_swap_cluster(struct swap_info_struct *si,
168 pgoff_t start_page, pgoff_t nr_pages)
169{
170 struct swap_extent *se = si->curr_swap_extent;
171 int found_extent = 0;
172
173 while (nr_pages) {
174 if (se->start_page <= start_page &&
175 start_page < se->start_page + se->nr_pages) {
176 pgoff_t offset = start_page - se->start_page;
177 sector_t start_block = se->start_block + offset;
178 sector_t nr_blocks = se->nr_pages - offset;
179
180 if (nr_blocks > nr_pages)
181 nr_blocks = nr_pages;
182 start_page += nr_blocks;
183 nr_pages -= nr_blocks;
184
185 if (!found_extent++)
186 si->curr_swap_extent = se;
187
188 start_block <<= PAGE_SHIFT - 9;
189 nr_blocks <<= PAGE_SHIFT - 9;
190 if (blkdev_issue_discard(si->bdev, start_block,
191 nr_blocks, GFP_NOIO, 0))
192 break;
193 }
194
195 se = list_next_entry(se, list);
196 }
197}
198
199#define SWAPFILE_CLUSTER 256
200#define LATENCY_LIMIT 256
201
202static inline void cluster_set_flag(struct swap_cluster_info *info,
203 unsigned int flag)
204{
205 info->flags = flag;
206}
207
208static inline unsigned int cluster_count(struct swap_cluster_info *info)
209{
210 return info->data;
211}
212
213static inline void cluster_set_count(struct swap_cluster_info *info,
214 unsigned int c)
215{
216 info->data = c;
217}
218
219static inline void cluster_set_count_flag(struct swap_cluster_info *info,
220 unsigned int c, unsigned int f)
221{
222 info->flags = f;
223 info->data = c;
224}
225
226static inline unsigned int cluster_next(struct swap_cluster_info *info)
227{
228 return info->data;
229}
230
231static inline void cluster_set_next(struct swap_cluster_info *info,
232 unsigned int n)
233{
234 info->data = n;
235}
236
237static inline void cluster_set_next_flag(struct swap_cluster_info *info,
238 unsigned int n, unsigned int f)
239{
240 info->flags = f;
241 info->data = n;
242}
243
244static inline bool cluster_is_free(struct swap_cluster_info *info)
245{
246 return info->flags & CLUSTER_FLAG_FREE;
247}
248
249static inline bool cluster_is_null(struct swap_cluster_info *info)
250{
251 return info->flags & CLUSTER_FLAG_NEXT_NULL;
252}
253
254static inline void cluster_set_null(struct swap_cluster_info *info)
255{
256 info->flags = CLUSTER_FLAG_NEXT_NULL;
257 info->data = 0;
258}
259
260static inline bool cluster_list_empty(struct swap_cluster_list *list)
261{
262 return cluster_is_null(&list->head);
263}
264
265static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
266{
267 return cluster_next(&list->head);
268}
269
270static void cluster_list_init(struct swap_cluster_list *list)
271{
272 cluster_set_null(&list->head);
273 cluster_set_null(&list->tail);
274}
275
276static void cluster_list_add_tail(struct swap_cluster_list *list,
277 struct swap_cluster_info *ci,
278 unsigned int idx)
279{
280 if (cluster_list_empty(list)) {
281 cluster_set_next_flag(&list->head, idx, 0);
282 cluster_set_next_flag(&list->tail, idx, 0);
283 } else {
284 unsigned int tail = cluster_next(&list->tail);
285
286 cluster_set_next(&ci[tail], idx);
287 cluster_set_next_flag(&list->tail, idx, 0);
288 }
289}
290
291static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
292 struct swap_cluster_info *ci)
293{
294 unsigned int idx;
295
296 idx = cluster_next(&list->head);
297 if (cluster_next(&list->tail) == idx) {
298 cluster_set_null(&list->head);
299 cluster_set_null(&list->tail);
300 } else
301 cluster_set_next_flag(&list->head,
302 cluster_next(&ci[idx]), 0);
303
304 return idx;
305}
306
307/* Add a cluster to discard list and schedule it to do discard */
308static void swap_cluster_schedule_discard(struct swap_info_struct *si,
309 unsigned int idx)
310{
311 /*
312 * If scan_swap_map() can't find a free cluster, it will check
313 * si->swap_map directly. To make sure the discarding cluster isn't
314 * taken by scan_swap_map(), mark the swap entries bad (occupied). It
315 * will be cleared after discard
316 */
317 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
318 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
319
320 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
321
322 schedule_work(&si->discard_work);
323}
324
325/*
326 * Doing discard actually. After a cluster discard is finished, the cluster
327 * will be added to free cluster list. caller should hold si->lock.
328*/
329static void swap_do_scheduled_discard(struct swap_info_struct *si)
330{
331 struct swap_cluster_info *info;
332 unsigned int idx;
333
334 info = si->cluster_info;
335
336 while (!cluster_list_empty(&si->discard_clusters)) {
337 idx = cluster_list_del_first(&si->discard_clusters, info);
338 spin_unlock(&si->lock);
339
340 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
341 SWAPFILE_CLUSTER);
342
343 spin_lock(&si->lock);
344 cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
345 cluster_list_add_tail(&si->free_clusters, info, idx);
346 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
347 0, SWAPFILE_CLUSTER);
348 }
349}
350
351static void swap_discard_work(struct work_struct *work)
352{
353 struct swap_info_struct *si;
354
355 si = container_of(work, struct swap_info_struct, discard_work);
356
357 spin_lock(&si->lock);
358 swap_do_scheduled_discard(si);
359 spin_unlock(&si->lock);
360}
361
362/*
363 * The cluster corresponding to page_nr will be used. The cluster will be
364 * removed from free cluster list and its usage counter will be increased.
365 */
366static void inc_cluster_info_page(struct swap_info_struct *p,
367 struct swap_cluster_info *cluster_info, unsigned long page_nr)
368{
369 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
370
371 if (!cluster_info)
372 return;
373 if (cluster_is_free(&cluster_info[idx])) {
374 VM_BUG_ON(cluster_list_first(&p->free_clusters) != idx);
375 cluster_list_del_first(&p->free_clusters, cluster_info);
376 cluster_set_count_flag(&cluster_info[idx], 0, 0);
377 }
378
379 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
380 cluster_set_count(&cluster_info[idx],
381 cluster_count(&cluster_info[idx]) + 1);
382}
383
384/*
385 * The cluster corresponding to page_nr decreases one usage. If the usage
386 * counter becomes 0, which means no page in the cluster is in using, we can
387 * optionally discard the cluster and add it to free cluster list.
388 */
389static void dec_cluster_info_page(struct swap_info_struct *p,
390 struct swap_cluster_info *cluster_info, unsigned long page_nr)
391{
392 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
393
394 if (!cluster_info)
395 return;
396
397 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
398 cluster_set_count(&cluster_info[idx],
399 cluster_count(&cluster_info[idx]) - 1);
400
401 if (cluster_count(&cluster_info[idx]) == 0) {
402 /*
403 * If the swap is discardable, prepare discard the cluster
404 * instead of free it immediately. The cluster will be freed
405 * after discard.
406 */
407 if ((p->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
408 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
409 swap_cluster_schedule_discard(p, idx);
410 return;
411 }
412
413 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
414 cluster_list_add_tail(&p->free_clusters, cluster_info, idx);
415 }
416}
417
418/*
419 * It's possible scan_swap_map() uses a free cluster in the middle of free
420 * cluster list. Avoiding such abuse to avoid list corruption.
421 */
422static bool
423scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
424 unsigned long offset)
425{
426 struct percpu_cluster *percpu_cluster;
427 bool conflict;
428
429 offset /= SWAPFILE_CLUSTER;
430 conflict = !cluster_list_empty(&si->free_clusters) &&
431 offset != cluster_list_first(&si->free_clusters) &&
432 cluster_is_free(&si->cluster_info[offset]);
433
434 if (!conflict)
435 return false;
436
437 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
438 cluster_set_null(&percpu_cluster->index);
439 return true;
440}
441
442/*
443 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
444 * might involve allocating a new cluster for current CPU too.
445 */
446static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
447 unsigned long *offset, unsigned long *scan_base)
448{
449 struct percpu_cluster *cluster;
450 bool found_free;
451 unsigned long tmp;
452
453new_cluster:
454 cluster = this_cpu_ptr(si->percpu_cluster);
455 if (cluster_is_null(&cluster->index)) {
456 if (!cluster_list_empty(&si->free_clusters)) {
457 cluster->index = si->free_clusters.head;
458 cluster->next = cluster_next(&cluster->index) *
459 SWAPFILE_CLUSTER;
460 } else if (!cluster_list_empty(&si->discard_clusters)) {
461 /*
462 * we don't have free cluster but have some clusters in
463 * discarding, do discard now and reclaim them
464 */
465 swap_do_scheduled_discard(si);
466 *scan_base = *offset = si->cluster_next;
467 goto new_cluster;
468 } else
469 return;
470 }
471
472 found_free = false;
473
474 /*
475 * Other CPUs can use our cluster if they can't find a free cluster,
476 * check if there is still free entry in the cluster
477 */
478 tmp = cluster->next;
479 while (tmp < si->max && tmp < (cluster_next(&cluster->index) + 1) *
480 SWAPFILE_CLUSTER) {
481 if (!si->swap_map[tmp]) {
482 found_free = true;
483 break;
484 }
485 tmp++;
486 }
487 if (!found_free) {
488 cluster_set_null(&cluster->index);
489 goto new_cluster;
490 }
491 cluster->next = tmp + 1;
492 *offset = tmp;
493 *scan_base = tmp;
494}
495
496static unsigned long scan_swap_map(struct swap_info_struct *si,
497 unsigned char usage)
498{
499 unsigned long offset;
500 unsigned long scan_base;
501 unsigned long last_in_cluster = 0;
502 int latency_ration = LATENCY_LIMIT;
503
504 /*
505 * We try to cluster swap pages by allocating them sequentially
506 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
507 * way, however, we resort to first-free allocation, starting
508 * a new cluster. This prevents us from scattering swap pages
509 * all over the entire swap partition, so that we reduce
510 * overall disk seek times between swap pages. -- sct
511 * But we do now try to find an empty cluster. -Andrea
512 * And we let swap pages go all over an SSD partition. Hugh
513 */
514
515 si->flags += SWP_SCANNING;
516 scan_base = offset = si->cluster_next;
517
518 /* SSD algorithm */
519 if (si->cluster_info) {
520 scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
521 goto checks;
522 }
523
524 if (unlikely(!si->cluster_nr--)) {
525 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
526 si->cluster_nr = SWAPFILE_CLUSTER - 1;
527 goto checks;
528 }
529
530 spin_unlock(&si->lock);
531
532 /*
533 * If seek is expensive, start searching for new cluster from
534 * start of partition, to minimize the span of allocated swap.
535 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
536 * case, just handled by scan_swap_map_try_ssd_cluster() above.
537 */
538 scan_base = offset = si->lowest_bit;
539 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
540
541 /* Locate the first empty (unaligned) cluster */
542 for (; last_in_cluster <= si->highest_bit; offset++) {
543 if (si->swap_map[offset])
544 last_in_cluster = offset + SWAPFILE_CLUSTER;
545 else if (offset == last_in_cluster) {
546 spin_lock(&si->lock);
547 offset -= SWAPFILE_CLUSTER - 1;
548 si->cluster_next = offset;
549 si->cluster_nr = SWAPFILE_CLUSTER - 1;
550 goto checks;
551 }
552 if (unlikely(--latency_ration < 0)) {
553 cond_resched();
554 latency_ration = LATENCY_LIMIT;
555 }
556 }
557
558 offset = scan_base;
559 spin_lock(&si->lock);
560 si->cluster_nr = SWAPFILE_CLUSTER - 1;
561 }
562
563checks:
564 if (si->cluster_info) {
565 while (scan_swap_map_ssd_cluster_conflict(si, offset))
566 scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
567 }
568 if (!(si->flags & SWP_WRITEOK))
569 goto no_page;
570 if (!si->highest_bit)
571 goto no_page;
572 if (offset > si->highest_bit)
573 scan_base = offset = si->lowest_bit;
574
575 /* reuse swap entry of cache-only swap if not busy. */
576 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
577 int swap_was_freed;
578 spin_unlock(&si->lock);
579 swap_was_freed = __try_to_reclaim_swap(si, offset);
580 spin_lock(&si->lock);
581 /* entry was freed successfully, try to use this again */
582 if (swap_was_freed)
583 goto checks;
584 goto scan; /* check next one */
585 }
586
587 if (si->swap_map[offset])
588 goto scan;
589
590 if (offset == si->lowest_bit)
591 si->lowest_bit++;
592 if (offset == si->highest_bit)
593 si->highest_bit--;
594 si->inuse_pages++;
595 if (si->inuse_pages == si->pages) {
596 si->lowest_bit = si->max;
597 si->highest_bit = 0;
598 spin_lock(&swap_avail_lock);
599 plist_del(&si->avail_list, &swap_avail_head);
600 spin_unlock(&swap_avail_lock);
601 }
602 si->swap_map[offset] = usage;
603 inc_cluster_info_page(si, si->cluster_info, offset);
604 si->cluster_next = offset + 1;
605 si->flags -= SWP_SCANNING;
606
607 return offset;
608
609scan:
610 spin_unlock(&si->lock);
611 while (++offset <= si->highest_bit) {
612 if (!si->swap_map[offset]) {
613 spin_lock(&si->lock);
614 goto checks;
615 }
616 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
617 spin_lock(&si->lock);
618 goto checks;
619 }
620 if (unlikely(--latency_ration < 0)) {
621 cond_resched();
622 latency_ration = LATENCY_LIMIT;
623 }
624 }
625 offset = si->lowest_bit;
626 while (offset < scan_base) {
627 if (!si->swap_map[offset]) {
628 spin_lock(&si->lock);
629 goto checks;
630 }
631 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
632 spin_lock(&si->lock);
633 goto checks;
634 }
635 if (unlikely(--latency_ration < 0)) {
636 cond_resched();
637 latency_ration = LATENCY_LIMIT;
638 }
639 offset++;
640 }
641 spin_lock(&si->lock);
642
643no_page:
644 si->flags -= SWP_SCANNING;
645 return 0;
646}
647
648swp_entry_t get_swap_page(void)
649{
650 struct swap_info_struct *si, *next;
651 pgoff_t offset;
652
653 if (atomic_long_read(&nr_swap_pages) <= 0)
654 goto noswap;
655 atomic_long_dec(&nr_swap_pages);
656
657 spin_lock(&swap_avail_lock);
658
659start_over:
660 plist_for_each_entry_safe(si, next, &swap_avail_head, avail_list) {
661 /* requeue si to after same-priority siblings */
662 plist_requeue(&si->avail_list, &swap_avail_head);
663 spin_unlock(&swap_avail_lock);
664 spin_lock(&si->lock);
665 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
666 spin_lock(&swap_avail_lock);
667 if (plist_node_empty(&si->avail_list)) {
668 spin_unlock(&si->lock);
669 goto nextsi;
670 }
671 WARN(!si->highest_bit,
672 "swap_info %d in list but !highest_bit\n",
673 si->type);
674 WARN(!(si->flags & SWP_WRITEOK),
675 "swap_info %d in list but !SWP_WRITEOK\n",
676 si->type);
677 plist_del(&si->avail_list, &swap_avail_head);
678 spin_unlock(&si->lock);
679 goto nextsi;
680 }
681
682 /* This is called for allocating swap entry for cache */
683 offset = scan_swap_map(si, SWAP_HAS_CACHE);
684 spin_unlock(&si->lock);
685 if (offset)
686 return swp_entry(si->type, offset);
687 pr_debug("scan_swap_map of si %d failed to find offset\n",
688 si->type);
689 spin_lock(&swap_avail_lock);
690nextsi:
691 /*
692 * if we got here, it's likely that si was almost full before,
693 * and since scan_swap_map() can drop the si->lock, multiple
694 * callers probably all tried to get a page from the same si
695 * and it filled up before we could get one; or, the si filled
696 * up between us dropping swap_avail_lock and taking si->lock.
697 * Since we dropped the swap_avail_lock, the swap_avail_head
698 * list may have been modified; so if next is still in the
699 * swap_avail_head list then try it, otherwise start over.
700 */
701 if (plist_node_empty(&next->avail_list))
702 goto start_over;
703 }
704
705 spin_unlock(&swap_avail_lock);
706
707 atomic_long_inc(&nr_swap_pages);
708noswap:
709 return (swp_entry_t) {0};
710}
711
712/* The only caller of this function is now suspend routine */
713swp_entry_t get_swap_page_of_type(int type)
714{
715 struct swap_info_struct *si;
716 pgoff_t offset;
717
718 si = swap_info[type];
719 spin_lock(&si->lock);
720 if (si && (si->flags & SWP_WRITEOK)) {
721 atomic_long_dec(&nr_swap_pages);
722 /* This is called for allocating swap entry, not cache */
723 offset = scan_swap_map(si, 1);
724 if (offset) {
725 spin_unlock(&si->lock);
726 return swp_entry(type, offset);
727 }
728 atomic_long_inc(&nr_swap_pages);
729 }
730 spin_unlock(&si->lock);
731 return (swp_entry_t) {0};
732}
733
734static struct swap_info_struct *swap_info_get(swp_entry_t entry)
735{
736 struct swap_info_struct *p;
737 unsigned long offset, type;
738
739 if (!entry.val)
740 goto out;
741 type = swp_type(entry);
742 if (type >= nr_swapfiles)
743 goto bad_nofile;
744 p = swap_info[type];
745 if (!(p->flags & SWP_USED))
746 goto bad_device;
747 offset = swp_offset(entry);
748 if (offset >= p->max)
749 goto bad_offset;
750 if (!p->swap_map[offset])
751 goto bad_free;
752 spin_lock(&p->lock);
753 return p;
754
755bad_free:
756 pr_err("swap_free: %s%08lx\n", Unused_offset, entry.val);
757 goto out;
758bad_offset:
759 pr_err("swap_free: %s%08lx\n", Bad_offset, entry.val);
760 goto out;
761bad_device:
762 pr_err("swap_free: %s%08lx\n", Unused_file, entry.val);
763 goto out;
764bad_nofile:
765 pr_err("swap_free: %s%08lx\n", Bad_file, entry.val);
766out:
767 return NULL;
768}
769
770static unsigned char swap_entry_free(struct swap_info_struct *p,
771 swp_entry_t entry, unsigned char usage)
772{
773 unsigned long offset = swp_offset(entry);
774 unsigned char count;
775 unsigned char has_cache;
776
777 count = p->swap_map[offset];
778 has_cache = count & SWAP_HAS_CACHE;
779 count &= ~SWAP_HAS_CACHE;
780
781 if (usage == SWAP_HAS_CACHE) {
782 VM_BUG_ON(!has_cache);
783 has_cache = 0;
784 } else if (count == SWAP_MAP_SHMEM) {
785 /*
786 * Or we could insist on shmem.c using a special
787 * swap_shmem_free() and free_shmem_swap_and_cache()...
788 */
789 count = 0;
790 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
791 if (count == COUNT_CONTINUED) {
792 if (swap_count_continued(p, offset, count))
793 count = SWAP_MAP_MAX | COUNT_CONTINUED;
794 else
795 count = SWAP_MAP_MAX;
796 } else
797 count--;
798 }
799
800 usage = count | has_cache;
801 p->swap_map[offset] = usage;
802
803 /* free if no reference */
804 if (!usage) {
805 mem_cgroup_uncharge_swap(entry);
806 dec_cluster_info_page(p, p->cluster_info, offset);
807 if (offset < p->lowest_bit)
808 p->lowest_bit = offset;
809 if (offset > p->highest_bit) {
810 bool was_full = !p->highest_bit;
811 p->highest_bit = offset;
812 if (was_full && (p->flags & SWP_WRITEOK)) {
813 spin_lock(&swap_avail_lock);
814 WARN_ON(!plist_node_empty(&p->avail_list));
815 if (plist_node_empty(&p->avail_list))
816 plist_add(&p->avail_list,
817 &swap_avail_head);
818 spin_unlock(&swap_avail_lock);
819 }
820 }
821 atomic_long_inc(&nr_swap_pages);
822 p->inuse_pages--;
823 frontswap_invalidate_page(p->type, offset);
824 if (p->flags & SWP_BLKDEV) {
825 struct gendisk *disk = p->bdev->bd_disk;
826 if (disk->fops->swap_slot_free_notify)
827 disk->fops->swap_slot_free_notify(p->bdev,
828 offset);
829 }
830 }
831
832 return usage;
833}
834
835/*
836 * Caller has made sure that the swap device corresponding to entry
837 * is still around or has not been recycled.
838 */
839void swap_free(swp_entry_t entry)
840{
841 struct swap_info_struct *p;
842
843 p = swap_info_get(entry);
844 if (p) {
845 swap_entry_free(p, entry, 1);
846 spin_unlock(&p->lock);
847 }
848}
849
850/*
851 * Called after dropping swapcache to decrease refcnt to swap entries.
852 */
853void swapcache_free(swp_entry_t entry)
854{
855 struct swap_info_struct *p;
856
857 p = swap_info_get(entry);
858 if (p) {
859 swap_entry_free(p, entry, SWAP_HAS_CACHE);
860 spin_unlock(&p->lock);
861 }
862}
863
864/*
865 * How many references to page are currently swapped out?
866 * This does not give an exact answer when swap count is continued,
867 * but does include the high COUNT_CONTINUED flag to allow for that.
868 */
869int page_swapcount(struct page *page)
870{
871 int count = 0;
872 struct swap_info_struct *p;
873 swp_entry_t entry;
874
875 entry.val = page_private(page);
876 p = swap_info_get(entry);
877 if (p) {
878 count = swap_count(p->swap_map[swp_offset(entry)]);
879 spin_unlock(&p->lock);
880 }
881 return count;
882}
883
884/*
885 * How many references to @entry are currently swapped out?
886 * This considers COUNT_CONTINUED so it returns exact answer.
887 */
888int swp_swapcount(swp_entry_t entry)
889{
890 int count, tmp_count, n;
891 struct swap_info_struct *p;
892 struct page *page;
893 pgoff_t offset;
894 unsigned char *map;
895
896 p = swap_info_get(entry);
897 if (!p)
898 return 0;
899
900 count = swap_count(p->swap_map[swp_offset(entry)]);
901 if (!(count & COUNT_CONTINUED))
902 goto out;
903
904 count &= ~COUNT_CONTINUED;
905 n = SWAP_MAP_MAX + 1;
906
907 offset = swp_offset(entry);
908 page = vmalloc_to_page(p->swap_map + offset);
909 offset &= ~PAGE_MASK;
910 VM_BUG_ON(page_private(page) != SWP_CONTINUED);
911
912 do {
913 page = list_next_entry(page, lru);
914 map = kmap_atomic(page);
915 tmp_count = map[offset];
916 kunmap_atomic(map);
917
918 count += (tmp_count & ~COUNT_CONTINUED) * n;
919 n *= (SWAP_CONT_MAX + 1);
920 } while (tmp_count & COUNT_CONTINUED);
921out:
922 spin_unlock(&p->lock);
923 return count;
924}
925
926/*
927 * We can write to an anon page without COW if there are no other references
928 * to it. And as a side-effect, free up its swap: because the old content
929 * on disk will never be read, and seeking back there to write new content
930 * later would only waste time away from clustering.
931 *
932 * NOTE: total_mapcount should not be relied upon by the caller if
933 * reuse_swap_page() returns false, but it may be always overwritten
934 * (see the other implementation for CONFIG_SWAP=n).
935 */
936bool reuse_swap_page(struct page *page, int *total_mapcount)
937{
938 int count;
939
940 VM_BUG_ON_PAGE(!PageLocked(page), page);
941 if (unlikely(PageKsm(page)))
942 return false;
943 count = page_trans_huge_mapcount(page, total_mapcount);
944 if (count <= 1 && PageSwapCache(page)) {
945 count += page_swapcount(page);
946 if (count != 1)
947 goto out;
948 if (!PageWriteback(page)) {
949 delete_from_swap_cache(page);
950 SetPageDirty(page);
951 } else {
952 swp_entry_t entry;
953 struct swap_info_struct *p;
954
955 entry.val = page_private(page);
956 p = swap_info_get(entry);
957 if (p->flags & SWP_STABLE_WRITES) {
958 spin_unlock(&p->lock);
959 return false;
960 }
961 spin_unlock(&p->lock);
962 }
963 }
964out:
965 return count <= 1;
966}
967
968/*
969 * If swap is getting full, or if there are no more mappings of this page,
970 * then try_to_free_swap is called to free its swap space.
971 */
972int try_to_free_swap(struct page *page)
973{
974 VM_BUG_ON_PAGE(!PageLocked(page), page);
975
976 if (!PageSwapCache(page))
977 return 0;
978 if (PageWriteback(page))
979 return 0;
980 if (page_swapcount(page))
981 return 0;
982
983 /*
984 * Once hibernation has begun to create its image of memory,
985 * there's a danger that one of the calls to try_to_free_swap()
986 * - most probably a call from __try_to_reclaim_swap() while
987 * hibernation is allocating its own swap pages for the image,
988 * but conceivably even a call from memory reclaim - will free
989 * the swap from a page which has already been recorded in the
990 * image as a clean swapcache page, and then reuse its swap for
991 * another page of the image. On waking from hibernation, the
992 * original page might be freed under memory pressure, then
993 * later read back in from swap, now with the wrong data.
994 *
995 * Hibernation suspends storage while it is writing the image
996 * to disk so check that here.
997 */
998 if (pm_suspended_storage())
999 return 0;
1000
1001 delete_from_swap_cache(page);
1002 SetPageDirty(page);
1003 return 1;
1004}
1005
1006/*
1007 * Free the swap entry like above, but also try to
1008 * free the page cache entry if it is the last user.
1009 */
1010int free_swap_and_cache(swp_entry_t entry)
1011{
1012 struct swap_info_struct *p;
1013 struct page *page = NULL;
1014
1015 if (non_swap_entry(entry))
1016 return 1;
1017
1018 p = swap_info_get(entry);
1019 if (p) {
1020 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
1021 page = find_get_page(swap_address_space(entry),
1022 swp_offset(entry));
1023 if (page && !trylock_page(page)) {
1024 put_page(page);
1025 page = NULL;
1026 }
1027 }
1028 spin_unlock(&p->lock);
1029 }
1030 if (page) {
1031 /*
1032 * Not mapped elsewhere, or swap space full? Free it!
1033 * Also recheck PageSwapCache now page is locked (above).
1034 */
1035 if (PageSwapCache(page) && !PageWriteback(page) &&
1036 (!page_mapped(page) || mem_cgroup_swap_full(page))) {
1037 delete_from_swap_cache(page);
1038 SetPageDirty(page);
1039 }
1040 unlock_page(page);
1041 put_page(page);
1042 }
1043 return p != NULL;
1044}
1045
1046#ifdef CONFIG_HIBERNATION
1047/*
1048 * Find the swap type that corresponds to given device (if any).
1049 *
1050 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1051 * from 0, in which the swap header is expected to be located.
1052 *
1053 * This is needed for the suspend to disk (aka swsusp).
1054 */
1055int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
1056{
1057 struct block_device *bdev = NULL;
1058 int type;
1059
1060 if (device)
1061 bdev = bdget(device);
1062
1063 spin_lock(&swap_lock);
1064 for (type = 0; type < nr_swapfiles; type++) {
1065 struct swap_info_struct *sis = swap_info[type];
1066
1067 if (!(sis->flags & SWP_WRITEOK))
1068 continue;
1069
1070 if (!bdev) {
1071 if (bdev_p)
1072 *bdev_p = bdgrab(sis->bdev);
1073
1074 spin_unlock(&swap_lock);
1075 return type;
1076 }
1077 if (bdev == sis->bdev) {
1078 struct swap_extent *se = &sis->first_swap_extent;
1079
1080 if (se->start_block == offset) {
1081 if (bdev_p)
1082 *bdev_p = bdgrab(sis->bdev);
1083
1084 spin_unlock(&swap_lock);
1085 bdput(bdev);
1086 return type;
1087 }
1088 }
1089 }
1090 spin_unlock(&swap_lock);
1091 if (bdev)
1092 bdput(bdev);
1093
1094 return -ENODEV;
1095}
1096
1097/*
1098 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1099 * corresponding to given index in swap_info (swap type).
1100 */
1101sector_t swapdev_block(int type, pgoff_t offset)
1102{
1103 struct block_device *bdev;
1104
1105 if ((unsigned int)type >= nr_swapfiles)
1106 return 0;
1107 if (!(swap_info[type]->flags & SWP_WRITEOK))
1108 return 0;
1109 return map_swap_entry(swp_entry(type, offset), &bdev);
1110}
1111
1112/*
1113 * Return either the total number of swap pages of given type, or the number
1114 * of free pages of that type (depending on @free)
1115 *
1116 * This is needed for software suspend
1117 */
1118unsigned int count_swap_pages(int type, int free)
1119{
1120 unsigned int n = 0;
1121
1122 spin_lock(&swap_lock);
1123 if ((unsigned int)type < nr_swapfiles) {
1124 struct swap_info_struct *sis = swap_info[type];
1125
1126 spin_lock(&sis->lock);
1127 if (sis->flags & SWP_WRITEOK) {
1128 n = sis->pages;
1129 if (free)
1130 n -= sis->inuse_pages;
1131 }
1132 spin_unlock(&sis->lock);
1133 }
1134 spin_unlock(&swap_lock);
1135 return n;
1136}
1137#endif /* CONFIG_HIBERNATION */
1138
1139static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1140{
1141 return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte);
1142}
1143
1144/*
1145 * No need to decide whether this PTE shares the swap entry with others,
1146 * just let do_wp_page work it out if a write is requested later - to
1147 * force COW, vm_page_prot omits write permission from any private vma.
1148 */
1149static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1150 unsigned long addr, swp_entry_t entry, struct page *page)
1151{
1152 struct page *swapcache;
1153 struct mem_cgroup *memcg;
1154 spinlock_t *ptl;
1155 pte_t *pte;
1156 int ret = 1;
1157
1158 swapcache = page;
1159 page = ksm_might_need_to_copy(page, vma, addr);
1160 if (unlikely(!page))
1161 return -ENOMEM;
1162
1163 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL,
1164 &memcg, false)) {
1165 ret = -ENOMEM;
1166 goto out_nolock;
1167 }
1168
1169 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1170 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1171 mem_cgroup_cancel_charge(page, memcg, false);
1172 ret = 0;
1173 goto out;
1174 }
1175
1176 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1177 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1178 get_page(page);
1179 set_pte_at(vma->vm_mm, addr, pte,
1180 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1181 if (page == swapcache) {
1182 page_add_anon_rmap(page, vma, addr, false);
1183 mem_cgroup_commit_charge(page, memcg, true, false);
1184 } else { /* ksm created a completely new copy */
1185 page_add_new_anon_rmap(page, vma, addr, false);
1186 mem_cgroup_commit_charge(page, memcg, false, false);
1187 lru_cache_add_active_or_unevictable(page, vma);
1188 }
1189 swap_free(entry);
1190 /*
1191 * Move the page to the active list so it is not
1192 * immediately swapped out again after swapon.
1193 */
1194 activate_page(page);
1195out:
1196 pte_unmap_unlock(pte, ptl);
1197out_nolock:
1198 if (page != swapcache) {
1199 unlock_page(page);
1200 put_page(page);
1201 }
1202 return ret;
1203}
1204
1205static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1206 unsigned long addr, unsigned long end,
1207 swp_entry_t entry, struct page *page)
1208{
1209 pte_t swp_pte = swp_entry_to_pte(entry);
1210 pte_t *pte;
1211 int ret = 0;
1212
1213 /*
1214 * We don't actually need pte lock while scanning for swp_pte: since
1215 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
1216 * page table while we're scanning; though it could get zapped, and on
1217 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
1218 * of unmatched parts which look like swp_pte, so unuse_pte must
1219 * recheck under pte lock. Scanning without pte lock lets it be
1220 * preemptable whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
1221 */
1222 pte = pte_offset_map(pmd, addr);
1223 do {
1224 /*
1225 * swapoff spends a _lot_ of time in this loop!
1226 * Test inline before going to call unuse_pte.
1227 */
1228 if (unlikely(pte_same_as_swp(*pte, swp_pte))) {
1229 pte_unmap(pte);
1230 ret = unuse_pte(vma, pmd, addr, entry, page);
1231 if (ret)
1232 goto out;
1233 pte = pte_offset_map(pmd, addr);
1234 }
1235 } while (pte++, addr += PAGE_SIZE, addr != end);
1236 pte_unmap(pte - 1);
1237out:
1238 return ret;
1239}
1240
1241static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1242 unsigned long addr, unsigned long end,
1243 swp_entry_t entry, struct page *page)
1244{
1245 pmd_t *pmd;
1246 unsigned long next;
1247 int ret;
1248
1249 pmd = pmd_offset(pud, addr);
1250 do {
1251 cond_resched();
1252 next = pmd_addr_end(addr, end);
1253 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1254 continue;
1255 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
1256 if (ret)
1257 return ret;
1258 } while (pmd++, addr = next, addr != end);
1259 return 0;
1260}
1261
1262static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
1263 unsigned long addr, unsigned long end,
1264 swp_entry_t entry, struct page *page)
1265{
1266 pud_t *pud;
1267 unsigned long next;
1268 int ret;
1269
1270 pud = pud_offset(pgd, addr);
1271 do {
1272 next = pud_addr_end(addr, end);
1273 if (pud_none_or_clear_bad(pud))
1274 continue;
1275 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
1276 if (ret)
1277 return ret;
1278 } while (pud++, addr = next, addr != end);
1279 return 0;
1280}
1281
1282static int unuse_vma(struct vm_area_struct *vma,
1283 swp_entry_t entry, struct page *page)
1284{
1285 pgd_t *pgd;
1286 unsigned long addr, end, next;
1287 int ret;
1288
1289 if (page_anon_vma(page)) {
1290 addr = page_address_in_vma(page, vma);
1291 if (addr == -EFAULT)
1292 return 0;
1293 else
1294 end = addr + PAGE_SIZE;
1295 } else {
1296 addr = vma->vm_start;
1297 end = vma->vm_end;
1298 }
1299
1300 pgd = pgd_offset(vma->vm_mm, addr);
1301 do {
1302 next = pgd_addr_end(addr, end);
1303 if (pgd_none_or_clear_bad(pgd))
1304 continue;
1305 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
1306 if (ret)
1307 return ret;
1308 } while (pgd++, addr = next, addr != end);
1309 return 0;
1310}
1311
1312static int unuse_mm(struct mm_struct *mm,
1313 swp_entry_t entry, struct page *page)
1314{
1315 struct vm_area_struct *vma;
1316 int ret = 0;
1317
1318 if (!down_read_trylock(&mm->mmap_sem)) {
1319 /*
1320 * Activate page so shrink_inactive_list is unlikely to unmap
1321 * its ptes while lock is dropped, so swapoff can make progress.
1322 */
1323 activate_page(page);
1324 unlock_page(page);
1325 down_read(&mm->mmap_sem);
1326 lock_page(page);
1327 }
1328 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1329 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
1330 break;
1331 cond_resched();
1332 }
1333 up_read(&mm->mmap_sem);
1334 return (ret < 0)? ret: 0;
1335}
1336
1337/*
1338 * Scan swap_map (or frontswap_map if frontswap parameter is true)
1339 * from current position to next entry still in use.
1340 * Recycle to start on reaching the end, returning 0 when empty.
1341 */
1342static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1343 unsigned int prev, bool frontswap)
1344{
1345 unsigned int max = si->max;
1346 unsigned int i = prev;
1347 unsigned char count;
1348
1349 /*
1350 * No need for swap_lock here: we're just looking
1351 * for whether an entry is in use, not modifying it; false
1352 * hits are okay, and sys_swapoff() has already prevented new
1353 * allocations from this area (while holding swap_lock).
1354 */
1355 for (;;) {
1356 if (++i >= max) {
1357 if (!prev) {
1358 i = 0;
1359 break;
1360 }
1361 /*
1362 * No entries in use at top of swap_map,
1363 * loop back to start and recheck there.
1364 */
1365 max = prev + 1;
1366 prev = 0;
1367 i = 1;
1368 }
1369 count = READ_ONCE(si->swap_map[i]);
1370 if (count && swap_count(count) != SWAP_MAP_BAD)
1371 if (!frontswap || frontswap_test(si, i))
1372 break;
1373 if ((i % LATENCY_LIMIT) == 0)
1374 cond_resched();
1375 }
1376 return i;
1377}
1378
1379/*
1380 * We completely avoid races by reading each swap page in advance,
1381 * and then search for the process using it. All the necessary
1382 * page table adjustments can then be made atomically.
1383 *
1384 * if the boolean frontswap is true, only unuse pages_to_unuse pages;
1385 * pages_to_unuse==0 means all pages; ignored if frontswap is false
1386 */
1387int try_to_unuse(unsigned int type, bool frontswap,
1388 unsigned long pages_to_unuse)
1389{
1390 struct swap_info_struct *si = swap_info[type];
1391 struct mm_struct *start_mm;
1392 volatile unsigned char *swap_map; /* swap_map is accessed without
1393 * locking. Mark it as volatile
1394 * to prevent compiler doing
1395 * something odd.
1396 */
1397 unsigned char swcount;
1398 struct page *page;
1399 swp_entry_t entry;
1400 unsigned int i = 0;
1401 int retval = 0;
1402
1403 /*
1404 * When searching mms for an entry, a good strategy is to
1405 * start at the first mm we freed the previous entry from
1406 * (though actually we don't notice whether we or coincidence
1407 * freed the entry). Initialize this start_mm with a hold.
1408 *
1409 * A simpler strategy would be to start at the last mm we
1410 * freed the previous entry from; but that would take less
1411 * advantage of mmlist ordering, which clusters forked mms
1412 * together, child after parent. If we race with dup_mmap(), we
1413 * prefer to resolve parent before child, lest we miss entries
1414 * duplicated after we scanned child: using last mm would invert
1415 * that.
1416 */
1417 start_mm = &init_mm;
1418 atomic_inc(&init_mm.mm_users);
1419
1420 /*
1421 * Keep on scanning until all entries have gone. Usually,
1422 * one pass through swap_map is enough, but not necessarily:
1423 * there are races when an instance of an entry might be missed.
1424 */
1425 while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
1426 if (signal_pending(current)) {
1427 retval = -EINTR;
1428 break;
1429 }
1430
1431 /*
1432 * Get a page for the entry, using the existing swap
1433 * cache page if there is one. Otherwise, get a clean
1434 * page and read the swap into it.
1435 */
1436 swap_map = &si->swap_map[i];
1437 entry = swp_entry(type, i);
1438 page = read_swap_cache_async(entry,
1439 GFP_HIGHUSER_MOVABLE, NULL, 0);
1440 if (!page) {
1441 /*
1442 * Either swap_duplicate() failed because entry
1443 * has been freed independently, and will not be
1444 * reused since sys_swapoff() already disabled
1445 * allocation from here, or alloc_page() failed.
1446 */
1447 swcount = *swap_map;
1448 /*
1449 * We don't hold lock here, so the swap entry could be
1450 * SWAP_MAP_BAD (when the cluster is discarding).
1451 * Instead of fail out, We can just skip the swap
1452 * entry because swapoff will wait for discarding
1453 * finish anyway.
1454 */
1455 if (!swcount || swcount == SWAP_MAP_BAD)
1456 continue;
1457 retval = -ENOMEM;
1458 break;
1459 }
1460
1461 /*
1462 * Don't hold on to start_mm if it looks like exiting.
1463 */
1464 if (atomic_read(&start_mm->mm_users) == 1) {
1465 mmput(start_mm);
1466 start_mm = &init_mm;
1467 atomic_inc(&init_mm.mm_users);
1468 }
1469
1470 /*
1471 * Wait for and lock page. When do_swap_page races with
1472 * try_to_unuse, do_swap_page can handle the fault much
1473 * faster than try_to_unuse can locate the entry. This
1474 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1475 * defer to do_swap_page in such a case - in some tests,
1476 * do_swap_page and try_to_unuse repeatedly compete.
1477 */
1478 wait_on_page_locked(page);
1479 wait_on_page_writeback(page);
1480 lock_page(page);
1481 wait_on_page_writeback(page);
1482
1483 /*
1484 * Remove all references to entry.
1485 */
1486 swcount = *swap_map;
1487 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1488 retval = shmem_unuse(entry, page);
1489 /* page has already been unlocked and released */
1490 if (retval < 0)
1491 break;
1492 continue;
1493 }
1494 if (swap_count(swcount) && start_mm != &init_mm)
1495 retval = unuse_mm(start_mm, entry, page);
1496
1497 if (swap_count(*swap_map)) {
1498 int set_start_mm = (*swap_map >= swcount);
1499 struct list_head *p = &start_mm->mmlist;
1500 struct mm_struct *new_start_mm = start_mm;
1501 struct mm_struct *prev_mm = start_mm;
1502 struct mm_struct *mm;
1503
1504 atomic_inc(&new_start_mm->mm_users);
1505 atomic_inc(&prev_mm->mm_users);
1506 spin_lock(&mmlist_lock);
1507 while (swap_count(*swap_map) && !retval &&
1508 (p = p->next) != &start_mm->mmlist) {
1509 mm = list_entry(p, struct mm_struct, mmlist);
1510 if (!atomic_inc_not_zero(&mm->mm_users))
1511 continue;
1512 spin_unlock(&mmlist_lock);
1513 mmput(prev_mm);
1514 prev_mm = mm;
1515
1516 cond_resched();
1517
1518 swcount = *swap_map;
1519 if (!swap_count(swcount)) /* any usage ? */
1520 ;
1521 else if (mm == &init_mm)
1522 set_start_mm = 1;
1523 else
1524 retval = unuse_mm(mm, entry, page);
1525
1526 if (set_start_mm && *swap_map < swcount) {
1527 mmput(new_start_mm);
1528 atomic_inc(&mm->mm_users);
1529 new_start_mm = mm;
1530 set_start_mm = 0;
1531 }
1532 spin_lock(&mmlist_lock);
1533 }
1534 spin_unlock(&mmlist_lock);
1535 mmput(prev_mm);
1536 mmput(start_mm);
1537 start_mm = new_start_mm;
1538 }
1539 if (retval) {
1540 unlock_page(page);
1541 put_page(page);
1542 break;
1543 }
1544
1545 /*
1546 * If a reference remains (rare), we would like to leave
1547 * the page in the swap cache; but try_to_unmap could
1548 * then re-duplicate the entry once we drop page lock,
1549 * so we might loop indefinitely; also, that page could
1550 * not be swapped out to other storage meanwhile. So:
1551 * delete from cache even if there's another reference,
1552 * after ensuring that the data has been saved to disk -
1553 * since if the reference remains (rarer), it will be
1554 * read from disk into another page. Splitting into two
1555 * pages would be incorrect if swap supported "shared
1556 * private" pages, but they are handled by tmpfs files.
1557 *
1558 * Given how unuse_vma() targets one particular offset
1559 * in an anon_vma, once the anon_vma has been determined,
1560 * this splitting happens to be just what is needed to
1561 * handle where KSM pages have been swapped out: re-reading
1562 * is unnecessarily slow, but we can fix that later on.
1563 */
1564 if (swap_count(*swap_map) &&
1565 PageDirty(page) && PageSwapCache(page)) {
1566 struct writeback_control wbc = {
1567 .sync_mode = WB_SYNC_NONE,
1568 };
1569
1570 swap_writepage(page, &wbc);
1571 lock_page(page);
1572 wait_on_page_writeback(page);
1573 }
1574
1575 /*
1576 * It is conceivable that a racing task removed this page from
1577 * swap cache just before we acquired the page lock at the top,
1578 * or while we dropped it in unuse_mm(). The page might even
1579 * be back in swap cache on another swap area: that we must not
1580 * delete, since it may not have been written out to swap yet.
1581 */
1582 if (PageSwapCache(page) &&
1583 likely(page_private(page) == entry.val))
1584 delete_from_swap_cache(page);
1585
1586 /*
1587 * So we could skip searching mms once swap count went
1588 * to 1, we did not mark any present ptes as dirty: must
1589 * mark page dirty so shrink_page_list will preserve it.
1590 */
1591 SetPageDirty(page);
1592 unlock_page(page);
1593 put_page(page);
1594
1595 /*
1596 * Make sure that we aren't completely killing
1597 * interactive performance.
1598 */
1599 cond_resched();
1600 if (frontswap && pages_to_unuse > 0) {
1601 if (!--pages_to_unuse)
1602 break;
1603 }
1604 }
1605
1606 mmput(start_mm);
1607 return retval;
1608}
1609
1610/*
1611 * After a successful try_to_unuse, if no swap is now in use, we know
1612 * we can empty the mmlist. swap_lock must be held on entry and exit.
1613 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1614 * added to the mmlist just after page_duplicate - before would be racy.
1615 */
1616static void drain_mmlist(void)
1617{
1618 struct list_head *p, *next;
1619 unsigned int type;
1620
1621 for (type = 0; type < nr_swapfiles; type++)
1622 if (swap_info[type]->inuse_pages)
1623 return;
1624 spin_lock(&mmlist_lock);
1625 list_for_each_safe(p, next, &init_mm.mmlist)
1626 list_del_init(p);
1627 spin_unlock(&mmlist_lock);
1628}
1629
1630/*
1631 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1632 * corresponds to page offset for the specified swap entry.
1633 * Note that the type of this function is sector_t, but it returns page offset
1634 * into the bdev, not sector offset.
1635 */
1636static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1637{
1638 struct swap_info_struct *sis;
1639 struct swap_extent *start_se;
1640 struct swap_extent *se;
1641 pgoff_t offset;
1642
1643 sis = swap_info[swp_type(entry)];
1644 *bdev = sis->bdev;
1645
1646 offset = swp_offset(entry);
1647 start_se = sis->curr_swap_extent;
1648 se = start_se;
1649
1650 for ( ; ; ) {
1651 if (se->start_page <= offset &&
1652 offset < (se->start_page + se->nr_pages)) {
1653 return se->start_block + (offset - se->start_page);
1654 }
1655 se = list_next_entry(se, list);
1656 sis->curr_swap_extent = se;
1657 BUG_ON(se == start_se); /* It *must* be present */
1658 }
1659}
1660
1661/*
1662 * Returns the page offset into bdev for the specified page's swap entry.
1663 */
1664sector_t map_swap_page(struct page *page, struct block_device **bdev)
1665{
1666 swp_entry_t entry;
1667 entry.val = page_private(page);
1668 return map_swap_entry(entry, bdev);
1669}
1670
1671/*
1672 * Free all of a swapdev's extent information
1673 */
1674static void destroy_swap_extents(struct swap_info_struct *sis)
1675{
1676 while (!list_empty(&sis->first_swap_extent.list)) {
1677 struct swap_extent *se;
1678
1679 se = list_first_entry(&sis->first_swap_extent.list,
1680 struct swap_extent, list);
1681 list_del(&se->list);
1682 kfree(se);
1683 }
1684
1685 if (sis->flags & SWP_FILE) {
1686 struct file *swap_file = sis->swap_file;
1687 struct address_space *mapping = swap_file->f_mapping;
1688
1689 sis->flags &= ~SWP_FILE;
1690 mapping->a_ops->swap_deactivate(swap_file);
1691 }
1692}
1693
1694/*
1695 * Add a block range (and the corresponding page range) into this swapdev's
1696 * extent list. The extent list is kept sorted in page order.
1697 *
1698 * This function rather assumes that it is called in ascending page order.
1699 */
1700int
1701add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1702 unsigned long nr_pages, sector_t start_block)
1703{
1704 struct swap_extent *se;
1705 struct swap_extent *new_se;
1706 struct list_head *lh;
1707
1708 if (start_page == 0) {
1709 se = &sis->first_swap_extent;
1710 sis->curr_swap_extent = se;
1711 se->start_page = 0;
1712 se->nr_pages = nr_pages;
1713 se->start_block = start_block;
1714 return 1;
1715 } else {
1716 lh = sis->first_swap_extent.list.prev; /* Highest extent */
1717 se = list_entry(lh, struct swap_extent, list);
1718 BUG_ON(se->start_page + se->nr_pages != start_page);
1719 if (se->start_block + se->nr_pages == start_block) {
1720 /* Merge it */
1721 se->nr_pages += nr_pages;
1722 return 0;
1723 }
1724 }
1725
1726 /*
1727 * No merge. Insert a new extent, preserving ordering.
1728 */
1729 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1730 if (new_se == NULL)
1731 return -ENOMEM;
1732 new_se->start_page = start_page;
1733 new_se->nr_pages = nr_pages;
1734 new_se->start_block = start_block;
1735
1736 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1737 return 1;
1738}
1739
1740/*
1741 * A `swap extent' is a simple thing which maps a contiguous range of pages
1742 * onto a contiguous range of disk blocks. An ordered list of swap extents
1743 * is built at swapon time and is then used at swap_writepage/swap_readpage
1744 * time for locating where on disk a page belongs.
1745 *
1746 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1747 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1748 * swap files identically.
1749 *
1750 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1751 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1752 * swapfiles are handled *identically* after swapon time.
1753 *
1754 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1755 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1756 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1757 * requirements, they are simply tossed out - we will never use those blocks
1758 * for swapping.
1759 *
1760 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1761 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1762 * which will scribble on the fs.
1763 *
1764 * The amount of disk space which a single swap extent represents varies.
1765 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1766 * extents in the list. To avoid much list walking, we cache the previous
1767 * search location in `curr_swap_extent', and start new searches from there.
1768 * This is extremely effective. The average number of iterations in
1769 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1770 */
1771static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1772{
1773 struct file *swap_file = sis->swap_file;
1774 struct address_space *mapping = swap_file->f_mapping;
1775 struct inode *inode = mapping->host;
1776 int ret;
1777
1778 if (S_ISBLK(inode->i_mode)) {
1779 ret = add_swap_extent(sis, 0, sis->max, 0);
1780 *span = sis->pages;
1781 return ret;
1782 }
1783
1784 if (mapping->a_ops->swap_activate) {
1785 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
1786 if (!ret) {
1787 sis->flags |= SWP_FILE;
1788 ret = add_swap_extent(sis, 0, sis->max, 0);
1789 *span = sis->pages;
1790 }
1791 return ret;
1792 }
1793
1794 return generic_swapfile_activate(sis, swap_file, span);
1795}
1796
1797static void _enable_swap_info(struct swap_info_struct *p, int prio,
1798 unsigned char *swap_map,
1799 struct swap_cluster_info *cluster_info)
1800{
1801 if (prio >= 0)
1802 p->prio = prio;
1803 else
1804 p->prio = --least_priority;
1805 /*
1806 * the plist prio is negated because plist ordering is
1807 * low-to-high, while swap ordering is high-to-low
1808 */
1809 p->list.prio = -p->prio;
1810 p->avail_list.prio = -p->prio;
1811 p->swap_map = swap_map;
1812 p->cluster_info = cluster_info;
1813 p->flags |= SWP_WRITEOK;
1814 atomic_long_add(p->pages, &nr_swap_pages);
1815 total_swap_pages += p->pages;
1816
1817 assert_spin_locked(&swap_lock);
1818 /*
1819 * both lists are plists, and thus priority ordered.
1820 * swap_active_head needs to be priority ordered for swapoff(),
1821 * which on removal of any swap_info_struct with an auto-assigned
1822 * (i.e. negative) priority increments the auto-assigned priority
1823 * of any lower-priority swap_info_structs.
1824 * swap_avail_head needs to be priority ordered for get_swap_page(),
1825 * which allocates swap pages from the highest available priority
1826 * swap_info_struct.
1827 */
1828 plist_add(&p->list, &swap_active_head);
1829 spin_lock(&swap_avail_lock);
1830 plist_add(&p->avail_list, &swap_avail_head);
1831 spin_unlock(&swap_avail_lock);
1832}
1833
1834static void enable_swap_info(struct swap_info_struct *p, int prio,
1835 unsigned char *swap_map,
1836 struct swap_cluster_info *cluster_info,
1837 unsigned long *frontswap_map)
1838{
1839 frontswap_init(p->type, frontswap_map);
1840 spin_lock(&swap_lock);
1841 spin_lock(&p->lock);
1842 _enable_swap_info(p, prio, swap_map, cluster_info);
1843 spin_unlock(&p->lock);
1844 spin_unlock(&swap_lock);
1845}
1846
1847static void reinsert_swap_info(struct swap_info_struct *p)
1848{
1849 spin_lock(&swap_lock);
1850 spin_lock(&p->lock);
1851 _enable_swap_info(p, p->prio, p->swap_map, p->cluster_info);
1852 spin_unlock(&p->lock);
1853 spin_unlock(&swap_lock);
1854}
1855
1856SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1857{
1858 struct swap_info_struct *p = NULL;
1859 unsigned char *swap_map;
1860 struct swap_cluster_info *cluster_info;
1861 unsigned long *frontswap_map;
1862 struct file *swap_file, *victim;
1863 struct address_space *mapping;
1864 struct inode *inode;
1865 struct filename *pathname;
1866 int err, found = 0;
1867 unsigned int old_block_size;
1868
1869 if (!capable(CAP_SYS_ADMIN))
1870 return -EPERM;
1871
1872 BUG_ON(!current->mm);
1873
1874 pathname = getname(specialfile);
1875 if (IS_ERR(pathname))
1876 return PTR_ERR(pathname);
1877
1878 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
1879 err = PTR_ERR(victim);
1880 if (IS_ERR(victim))
1881 goto out;
1882
1883 mapping = victim->f_mapping;
1884 spin_lock(&swap_lock);
1885 plist_for_each_entry(p, &swap_active_head, list) {
1886 if (p->flags & SWP_WRITEOK) {
1887 if (p->swap_file->f_mapping == mapping) {
1888 found = 1;
1889 break;
1890 }
1891 }
1892 }
1893 if (!found) {
1894 err = -EINVAL;
1895 spin_unlock(&swap_lock);
1896 goto out_dput;
1897 }
1898 if (!security_vm_enough_memory_mm(current->mm, p->pages))
1899 vm_unacct_memory(p->pages);
1900 else {
1901 err = -ENOMEM;
1902 spin_unlock(&swap_lock);
1903 goto out_dput;
1904 }
1905 spin_lock(&swap_avail_lock);
1906 plist_del(&p->avail_list, &swap_avail_head);
1907 spin_unlock(&swap_avail_lock);
1908 spin_lock(&p->lock);
1909 if (p->prio < 0) {
1910 struct swap_info_struct *si = p;
1911
1912 plist_for_each_entry_continue(si, &swap_active_head, list) {
1913 si->prio++;
1914 si->list.prio--;
1915 si->avail_list.prio--;
1916 }
1917 least_priority++;
1918 }
1919 plist_del(&p->list, &swap_active_head);
1920 atomic_long_sub(p->pages, &nr_swap_pages);
1921 total_swap_pages -= p->pages;
1922 p->flags &= ~SWP_WRITEOK;
1923 spin_unlock(&p->lock);
1924 spin_unlock(&swap_lock);
1925
1926 set_current_oom_origin();
1927 err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
1928 clear_current_oom_origin();
1929
1930 if (err) {
1931 /* re-insert swap space back into swap_list */
1932 reinsert_swap_info(p);
1933 goto out_dput;
1934 }
1935
1936 flush_work(&p->discard_work);
1937
1938 destroy_swap_extents(p);
1939 if (p->flags & SWP_CONTINUED)
1940 free_swap_count_continuations(p);
1941
1942 mutex_lock(&swapon_mutex);
1943 spin_lock(&swap_lock);
1944 spin_lock(&p->lock);
1945 drain_mmlist();
1946
1947 /* wait for anyone still in scan_swap_map */
1948 p->highest_bit = 0; /* cuts scans short */
1949 while (p->flags >= SWP_SCANNING) {
1950 spin_unlock(&p->lock);
1951 spin_unlock(&swap_lock);
1952 schedule_timeout_uninterruptible(1);
1953 spin_lock(&swap_lock);
1954 spin_lock(&p->lock);
1955 }
1956
1957 swap_file = p->swap_file;
1958 old_block_size = p->old_block_size;
1959 p->swap_file = NULL;
1960 p->max = 0;
1961 swap_map = p->swap_map;
1962 p->swap_map = NULL;
1963 cluster_info = p->cluster_info;
1964 p->cluster_info = NULL;
1965 frontswap_map = frontswap_map_get(p);
1966 spin_unlock(&p->lock);
1967 spin_unlock(&swap_lock);
1968 frontswap_invalidate_area(p->type);
1969 frontswap_map_set(p, NULL);
1970 mutex_unlock(&swapon_mutex);
1971 free_percpu(p->percpu_cluster);
1972 p->percpu_cluster = NULL;
1973 vfree(swap_map);
1974 vfree(cluster_info);
1975 vfree(frontswap_map);
1976 /* Destroy swap account information */
1977 swap_cgroup_swapoff(p->type);
1978
1979 inode = mapping->host;
1980 if (S_ISBLK(inode->i_mode)) {
1981 struct block_device *bdev = I_BDEV(inode);
1982 set_blocksize(bdev, old_block_size);
1983 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
1984 } else {
1985 inode_lock(inode);
1986 inode->i_flags &= ~S_SWAPFILE;
1987 inode_unlock(inode);
1988 }
1989 filp_close(swap_file, NULL);
1990
1991 /*
1992 * Clear the SWP_USED flag after all resources are freed so that swapon
1993 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
1994 * not hold p->lock after we cleared its SWP_WRITEOK.
1995 */
1996 spin_lock(&swap_lock);
1997 p->flags = 0;
1998 spin_unlock(&swap_lock);
1999
2000 err = 0;
2001 atomic_inc(&proc_poll_event);
2002 wake_up_interruptible(&proc_poll_wait);
2003
2004out_dput:
2005 filp_close(victim, NULL);
2006out:
2007 putname(pathname);
2008 return err;
2009}
2010
2011#ifdef CONFIG_PROC_FS
2012static unsigned swaps_poll(struct file *file, poll_table *wait)
2013{
2014 struct seq_file *seq = file->private_data;
2015
2016 poll_wait(file, &proc_poll_wait, wait);
2017
2018 if (seq->poll_event != atomic_read(&proc_poll_event)) {
2019 seq->poll_event = atomic_read(&proc_poll_event);
2020 return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
2021 }
2022
2023 return POLLIN | POLLRDNORM;
2024}
2025
2026/* iterator */
2027static void *swap_start(struct seq_file *swap, loff_t *pos)
2028{
2029 struct swap_info_struct *si;
2030 int type;
2031 loff_t l = *pos;
2032
2033 mutex_lock(&swapon_mutex);
2034
2035 if (!l)
2036 return SEQ_START_TOKEN;
2037
2038 for (type = 0; type < nr_swapfiles; type++) {
2039 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
2040 si = swap_info[type];
2041 if (!(si->flags & SWP_USED) || !si->swap_map)
2042 continue;
2043 if (!--l)
2044 return si;
2045 }
2046
2047 return NULL;
2048}
2049
2050static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2051{
2052 struct swap_info_struct *si = v;
2053 int type;
2054
2055 if (v == SEQ_START_TOKEN)
2056 type = 0;
2057 else
2058 type = si->type + 1;
2059
2060 for (; type < nr_swapfiles; type++) {
2061 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
2062 si = swap_info[type];
2063 if (!(si->flags & SWP_USED) || !si->swap_map)
2064 continue;
2065 ++*pos;
2066 return si;
2067 }
2068
2069 return NULL;
2070}
2071
2072static void swap_stop(struct seq_file *swap, void *v)
2073{
2074 mutex_unlock(&swapon_mutex);
2075}
2076
2077static int swap_show(struct seq_file *swap, void *v)
2078{
2079 struct swap_info_struct *si = v;
2080 struct file *file;
2081 int len;
2082
2083 if (si == SEQ_START_TOKEN) {
2084 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
2085 return 0;
2086 }
2087
2088 file = si->swap_file;
2089 len = seq_file_path(swap, file, " \t\n\\");
2090 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
2091 len < 40 ? 40 - len : 1, " ",
2092 S_ISBLK(file_inode(file)->i_mode) ?
2093 "partition" : "file\t",
2094 si->pages << (PAGE_SHIFT - 10),
2095 si->inuse_pages << (PAGE_SHIFT - 10),
2096 si->prio);
2097 return 0;
2098}
2099
2100static const struct seq_operations swaps_op = {
2101 .start = swap_start,
2102 .next = swap_next,
2103 .stop = swap_stop,
2104 .show = swap_show
2105};
2106
2107static int swaps_open(struct inode *inode, struct file *file)
2108{
2109 struct seq_file *seq;
2110 int ret;
2111
2112 ret = seq_open(file, &swaps_op);
2113 if (ret)
2114 return ret;
2115
2116 seq = file->private_data;
2117 seq->poll_event = atomic_read(&proc_poll_event);
2118 return 0;
2119}
2120
2121static const struct file_operations proc_swaps_operations = {
2122 .open = swaps_open,
2123 .read = seq_read,
2124 .llseek = seq_lseek,
2125 .release = seq_release,
2126 .poll = swaps_poll,
2127};
2128
2129static int __init procswaps_init(void)
2130{
2131 proc_create("swaps", 0, NULL, &proc_swaps_operations);
2132 return 0;
2133}
2134__initcall(procswaps_init);
2135#endif /* CONFIG_PROC_FS */
2136
2137#ifdef MAX_SWAPFILES_CHECK
2138static int __init max_swapfiles_check(void)
2139{
2140 MAX_SWAPFILES_CHECK();
2141 return 0;
2142}
2143late_initcall(max_swapfiles_check);
2144#endif
2145
2146static struct swap_info_struct *alloc_swap_info(void)
2147{
2148 struct swap_info_struct *p;
2149 unsigned int type;
2150
2151 p = kzalloc(sizeof(*p), GFP_KERNEL);
2152 if (!p)
2153 return ERR_PTR(-ENOMEM);
2154
2155 spin_lock(&swap_lock);
2156 for (type = 0; type < nr_swapfiles; type++) {
2157 if (!(swap_info[type]->flags & SWP_USED))
2158 break;
2159 }
2160 if (type >= MAX_SWAPFILES) {
2161 spin_unlock(&swap_lock);
2162 kfree(p);
2163 return ERR_PTR(-EPERM);
2164 }
2165 if (type >= nr_swapfiles) {
2166 p->type = type;
2167 swap_info[type] = p;
2168 /*
2169 * Write swap_info[type] before nr_swapfiles, in case a
2170 * racing procfs swap_start() or swap_next() is reading them.
2171 * (We never shrink nr_swapfiles, we never free this entry.)
2172 */
2173 smp_wmb();
2174 nr_swapfiles++;
2175 } else {
2176 kfree(p);
2177 p = swap_info[type];
2178 /*
2179 * Do not memset this entry: a racing procfs swap_next()
2180 * would be relying on p->type to remain valid.
2181 */
2182 }
2183 INIT_LIST_HEAD(&p->first_swap_extent.list);
2184 plist_node_init(&p->list, 0);
2185 plist_node_init(&p->avail_list, 0);
2186 p->flags = SWP_USED;
2187 spin_unlock(&swap_lock);
2188 spin_lock_init(&p->lock);
2189
2190 return p;
2191}
2192
2193static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2194{
2195 int error;
2196
2197 if (S_ISBLK(inode->i_mode)) {
2198 p->bdev = bdgrab(I_BDEV(inode));
2199 error = blkdev_get(p->bdev,
2200 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2201 if (error < 0) {
2202 p->bdev = NULL;
2203 return error;
2204 }
2205 p->old_block_size = block_size(p->bdev);
2206 error = set_blocksize(p->bdev, PAGE_SIZE);
2207 if (error < 0)
2208 return error;
2209 p->flags |= SWP_BLKDEV;
2210 } else if (S_ISREG(inode->i_mode)) {
2211 p->bdev = inode->i_sb->s_bdev;
2212 inode_lock(inode);
2213 if (IS_SWAPFILE(inode))
2214 return -EBUSY;
2215 } else
2216 return -EINVAL;
2217
2218 return 0;
2219}
2220
2221static unsigned long read_swap_header(struct swap_info_struct *p,
2222 union swap_header *swap_header,
2223 struct inode *inode)
2224{
2225 int i;
2226 unsigned long maxpages;
2227 unsigned long swapfilepages;
2228 unsigned long last_page;
2229
2230 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2231 pr_err("Unable to find swap-space signature\n");
2232 return 0;
2233 }
2234
2235 /* swap partition endianess hack... */
2236 if (swab32(swap_header->info.version) == 1) {
2237 swab32s(&swap_header->info.version);
2238 swab32s(&swap_header->info.last_page);
2239 swab32s(&swap_header->info.nr_badpages);
2240 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2241 return 0;
2242 for (i = 0; i < swap_header->info.nr_badpages; i++)
2243 swab32s(&swap_header->info.badpages[i]);
2244 }
2245 /* Check the swap header's sub-version */
2246 if (swap_header->info.version != 1) {
2247 pr_warn("Unable to handle swap header version %d\n",
2248 swap_header->info.version);
2249 return 0;
2250 }
2251
2252 p->lowest_bit = 1;
2253 p->cluster_next = 1;
2254 p->cluster_nr = 0;
2255
2256 /*
2257 * Find out how many pages are allowed for a single swap
2258 * device. There are two limiting factors: 1) the number
2259 * of bits for the swap offset in the swp_entry_t type, and
2260 * 2) the number of bits in the swap pte as defined by the
2261 * different architectures. In order to find the
2262 * largest possible bit mask, a swap entry with swap type 0
2263 * and swap offset ~0UL is created, encoded to a swap pte,
2264 * decoded to a swp_entry_t again, and finally the swap
2265 * offset is extracted. This will mask all the bits from
2266 * the initial ~0UL mask that can't be encoded in either
2267 * the swp_entry_t or the architecture definition of a
2268 * swap pte.
2269 */
2270 maxpages = swp_offset(pte_to_swp_entry(
2271 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2272 last_page = swap_header->info.last_page;
2273 if (last_page > maxpages) {
2274 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2275 maxpages << (PAGE_SHIFT - 10),
2276 last_page << (PAGE_SHIFT - 10));
2277 }
2278 if (maxpages > last_page) {
2279 maxpages = last_page + 1;
2280 /* p->max is an unsigned int: don't overflow it */
2281 if ((unsigned int)maxpages == 0)
2282 maxpages = UINT_MAX;
2283 }
2284 p->highest_bit = maxpages - 1;
2285
2286 if (!maxpages)
2287 return 0;
2288 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2289 if (swapfilepages && maxpages > swapfilepages) {
2290 pr_warn("Swap area shorter than signature indicates\n");
2291 return 0;
2292 }
2293 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2294 return 0;
2295 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2296 return 0;
2297
2298 return maxpages;
2299}
2300
2301static int setup_swap_map_and_extents(struct swap_info_struct *p,
2302 union swap_header *swap_header,
2303 unsigned char *swap_map,
2304 struct swap_cluster_info *cluster_info,
2305 unsigned long maxpages,
2306 sector_t *span)
2307{
2308 int i;
2309 unsigned int nr_good_pages;
2310 int nr_extents;
2311 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2312 unsigned long idx = p->cluster_next / SWAPFILE_CLUSTER;
2313
2314 nr_good_pages = maxpages - 1; /* omit header page */
2315
2316 cluster_list_init(&p->free_clusters);
2317 cluster_list_init(&p->discard_clusters);
2318
2319 for (i = 0; i < swap_header->info.nr_badpages; i++) {
2320 unsigned int page_nr = swap_header->info.badpages[i];
2321 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2322 return -EINVAL;
2323 if (page_nr < maxpages) {
2324 swap_map[page_nr] = SWAP_MAP_BAD;
2325 nr_good_pages--;
2326 /*
2327 * Haven't marked the cluster free yet, no list
2328 * operation involved
2329 */
2330 inc_cluster_info_page(p, cluster_info, page_nr);
2331 }
2332 }
2333
2334 /* Haven't marked the cluster free yet, no list operation involved */
2335 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2336 inc_cluster_info_page(p, cluster_info, i);
2337
2338 if (nr_good_pages) {
2339 swap_map[0] = SWAP_MAP_BAD;
2340 /*
2341 * Not mark the cluster free yet, no list
2342 * operation involved
2343 */
2344 inc_cluster_info_page(p, cluster_info, 0);
2345 p->max = maxpages;
2346 p->pages = nr_good_pages;
2347 nr_extents = setup_swap_extents(p, span);
2348 if (nr_extents < 0)
2349 return nr_extents;
2350 nr_good_pages = p->pages;
2351 }
2352 if (!nr_good_pages) {
2353 pr_warn("Empty swap-file\n");
2354 return -EINVAL;
2355 }
2356
2357 if (!cluster_info)
2358 return nr_extents;
2359
2360 for (i = 0; i < nr_clusters; i++) {
2361 if (!cluster_count(&cluster_info[idx])) {
2362 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2363 cluster_list_add_tail(&p->free_clusters, cluster_info,
2364 idx);
2365 }
2366 idx++;
2367 if (idx == nr_clusters)
2368 idx = 0;
2369 }
2370 return nr_extents;
2371}
2372
2373/*
2374 * Helper to sys_swapon determining if a given swap
2375 * backing device queue supports DISCARD operations.
2376 */
2377static bool swap_discardable(struct swap_info_struct *si)
2378{
2379 struct request_queue *q = bdev_get_queue(si->bdev);
2380
2381 if (!q || !blk_queue_discard(q))
2382 return false;
2383
2384 return true;
2385}
2386
2387SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2388{
2389 struct swap_info_struct *p;
2390 struct filename *name;
2391 struct file *swap_file = NULL;
2392 struct address_space *mapping;
2393 int prio;
2394 int error;
2395 union swap_header *swap_header;
2396 int nr_extents;
2397 sector_t span;
2398 unsigned long maxpages;
2399 unsigned char *swap_map = NULL;
2400 struct swap_cluster_info *cluster_info = NULL;
2401 unsigned long *frontswap_map = NULL;
2402 struct page *page = NULL;
2403 struct inode *inode = NULL;
2404
2405 if (swap_flags & ~SWAP_FLAGS_VALID)
2406 return -EINVAL;
2407
2408 if (!capable(CAP_SYS_ADMIN))
2409 return -EPERM;
2410
2411 p = alloc_swap_info();
2412 if (IS_ERR(p))
2413 return PTR_ERR(p);
2414
2415 INIT_WORK(&p->discard_work, swap_discard_work);
2416
2417 name = getname(specialfile);
2418 if (IS_ERR(name)) {
2419 error = PTR_ERR(name);
2420 name = NULL;
2421 goto bad_swap;
2422 }
2423 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
2424 if (IS_ERR(swap_file)) {
2425 error = PTR_ERR(swap_file);
2426 swap_file = NULL;
2427 goto bad_swap;
2428 }
2429
2430 p->swap_file = swap_file;
2431 mapping = swap_file->f_mapping;
2432 inode = mapping->host;
2433
2434 /* If S_ISREG(inode->i_mode) will do inode_lock(inode); */
2435 error = claim_swapfile(p, inode);
2436 if (unlikely(error))
2437 goto bad_swap;
2438
2439 /*
2440 * Read the swap header.
2441 */
2442 if (!mapping->a_ops->readpage) {
2443 error = -EINVAL;
2444 goto bad_swap;
2445 }
2446 page = read_mapping_page(mapping, 0, swap_file);
2447 if (IS_ERR(page)) {
2448 error = PTR_ERR(page);
2449 goto bad_swap;
2450 }
2451 swap_header = kmap(page);
2452
2453 maxpages = read_swap_header(p, swap_header, inode);
2454 if (unlikely(!maxpages)) {
2455 error = -EINVAL;
2456 goto bad_swap;
2457 }
2458
2459 /* OK, set up the swap map and apply the bad block list */
2460 swap_map = vzalloc(maxpages);
2461 if (!swap_map) {
2462 error = -ENOMEM;
2463 goto bad_swap;
2464 }
2465
2466 if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))
2467 p->flags |= SWP_STABLE_WRITES;
2468
2469 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2470 int cpu;
2471
2472 p->flags |= SWP_SOLIDSTATE;
2473 /*
2474 * select a random position to start with to help wear leveling
2475 * SSD
2476 */
2477 p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
2478
2479 cluster_info = vzalloc(DIV_ROUND_UP(maxpages,
2480 SWAPFILE_CLUSTER) * sizeof(*cluster_info));
2481 if (!cluster_info) {
2482 error = -ENOMEM;
2483 goto bad_swap;
2484 }
2485 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
2486 if (!p->percpu_cluster) {
2487 error = -ENOMEM;
2488 goto bad_swap;
2489 }
2490 for_each_possible_cpu(cpu) {
2491 struct percpu_cluster *cluster;
2492 cluster = per_cpu_ptr(p->percpu_cluster, cpu);
2493 cluster_set_null(&cluster->index);
2494 }
2495 }
2496
2497 error = swap_cgroup_swapon(p->type, maxpages);
2498 if (error)
2499 goto bad_swap;
2500
2501 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
2502 cluster_info, maxpages, &span);
2503 if (unlikely(nr_extents < 0)) {
2504 error = nr_extents;
2505 goto bad_swap;
2506 }
2507 /* frontswap enabled? set up bit-per-page map for frontswap */
2508 if (IS_ENABLED(CONFIG_FRONTSWAP))
2509 frontswap_map = vzalloc(BITS_TO_LONGS(maxpages) * sizeof(long));
2510
2511 if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
2512 /*
2513 * When discard is enabled for swap with no particular
2514 * policy flagged, we set all swap discard flags here in
2515 * order to sustain backward compatibility with older
2516 * swapon(8) releases.
2517 */
2518 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
2519 SWP_PAGE_DISCARD);
2520
2521 /*
2522 * By flagging sys_swapon, a sysadmin can tell us to
2523 * either do single-time area discards only, or to just
2524 * perform discards for released swap page-clusters.
2525 * Now it's time to adjust the p->flags accordingly.
2526 */
2527 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
2528 p->flags &= ~SWP_PAGE_DISCARD;
2529 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
2530 p->flags &= ~SWP_AREA_DISCARD;
2531
2532 /* issue a swapon-time discard if it's still required */
2533 if (p->flags & SWP_AREA_DISCARD) {
2534 int err = discard_swap(p);
2535 if (unlikely(err))
2536 pr_err("swapon: discard_swap(%p): %d\n",
2537 p, err);
2538 }
2539 }
2540
2541 mutex_lock(&swapon_mutex);
2542 prio = -1;
2543 if (swap_flags & SWAP_FLAG_PREFER)
2544 prio =
2545 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2546 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
2547
2548 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
2549 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
2550 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2551 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2552 (p->flags & SWP_DISCARDABLE) ? "D" : "",
2553 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
2554 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
2555 (frontswap_map) ? "FS" : "");
2556
2557 mutex_unlock(&swapon_mutex);
2558 atomic_inc(&proc_poll_event);
2559 wake_up_interruptible(&proc_poll_wait);
2560
2561 if (S_ISREG(inode->i_mode))
2562 inode->i_flags |= S_SWAPFILE;
2563 error = 0;
2564 goto out;
2565bad_swap:
2566 free_percpu(p->percpu_cluster);
2567 p->percpu_cluster = NULL;
2568 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
2569 set_blocksize(p->bdev, p->old_block_size);
2570 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2571 }
2572 destroy_swap_extents(p);
2573 swap_cgroup_swapoff(p->type);
2574 spin_lock(&swap_lock);
2575 p->swap_file = NULL;
2576 p->flags = 0;
2577 spin_unlock(&swap_lock);
2578 vfree(swap_map);
2579 vfree(cluster_info);
2580 if (swap_file) {
2581 if (inode && S_ISREG(inode->i_mode)) {
2582 inode_unlock(inode);
2583 inode = NULL;
2584 }
2585 filp_close(swap_file, NULL);
2586 }
2587out:
2588 if (page && !IS_ERR(page)) {
2589 kunmap(page);
2590 put_page(page);
2591 }
2592 if (name)
2593 putname(name);
2594 if (inode && S_ISREG(inode->i_mode))
2595 inode_unlock(inode);
2596 return error;
2597}
2598
2599void si_swapinfo(struct sysinfo *val)
2600{
2601 unsigned int type;
2602 unsigned long nr_to_be_unused = 0;
2603
2604 spin_lock(&swap_lock);
2605 for (type = 0; type < nr_swapfiles; type++) {
2606 struct swap_info_struct *si = swap_info[type];
2607
2608 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2609 nr_to_be_unused += si->inuse_pages;
2610 }
2611 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
2612 val->totalswap = total_swap_pages + nr_to_be_unused;
2613 spin_unlock(&swap_lock);
2614}
2615
2616/*
2617 * Verify that a swap entry is valid and increment its swap map count.
2618 *
2619 * Returns error code in following case.
2620 * - success -> 0
2621 * - swp_entry is invalid -> EINVAL
2622 * - swp_entry is migration entry -> EINVAL
2623 * - swap-cache reference is requested but there is already one. -> EEXIST
2624 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2625 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2626 */
2627static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2628{
2629 struct swap_info_struct *p;
2630 unsigned long offset, type;
2631 unsigned char count;
2632 unsigned char has_cache;
2633 int err = -EINVAL;
2634
2635 if (non_swap_entry(entry))
2636 goto out;
2637
2638 type = swp_type(entry);
2639 if (type >= nr_swapfiles)
2640 goto bad_file;
2641 p = swap_info[type];
2642 offset = swp_offset(entry);
2643
2644 spin_lock(&p->lock);
2645 if (unlikely(offset >= p->max))
2646 goto unlock_out;
2647
2648 count = p->swap_map[offset];
2649
2650 /*
2651 * swapin_readahead() doesn't check if a swap entry is valid, so the
2652 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
2653 */
2654 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
2655 err = -ENOENT;
2656 goto unlock_out;
2657 }
2658
2659 has_cache = count & SWAP_HAS_CACHE;
2660 count &= ~SWAP_HAS_CACHE;
2661 err = 0;
2662
2663 if (usage == SWAP_HAS_CACHE) {
2664
2665 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2666 if (!has_cache && count)
2667 has_cache = SWAP_HAS_CACHE;
2668 else if (has_cache) /* someone else added cache */
2669 err = -EEXIST;
2670 else /* no users remaining */
2671 err = -ENOENT;
2672
2673 } else if (count || has_cache) {
2674
2675 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2676 count += usage;
2677 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2678 err = -EINVAL;
2679 else if (swap_count_continued(p, offset, count))
2680 count = COUNT_CONTINUED;
2681 else
2682 err = -ENOMEM;
2683 } else
2684 err = -ENOENT; /* unused swap entry */
2685
2686 p->swap_map[offset] = count | has_cache;
2687
2688unlock_out:
2689 spin_unlock(&p->lock);
2690out:
2691 return err;
2692
2693bad_file:
2694 pr_err("swap_dup: %s%08lx\n", Bad_file, entry.val);
2695 goto out;
2696}
2697
2698/*
2699 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2700 * (in which case its reference count is never incremented).
2701 */
2702void swap_shmem_alloc(swp_entry_t entry)
2703{
2704 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2705}
2706
2707/*
2708 * Increase reference count of swap entry by 1.
2709 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2710 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2711 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2712 * might occur if a page table entry has got corrupted.
2713 */
2714int swap_duplicate(swp_entry_t entry)
2715{
2716 int err = 0;
2717
2718 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2719 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2720 return err;
2721}
2722
2723/*
2724 * @entry: swap entry for which we allocate swap cache.
2725 *
2726 * Called when allocating swap cache for existing swap entry,
2727 * This can return error codes. Returns 0 at success.
2728 * -EBUSY means there is a swap cache.
2729 * Note: return code is different from swap_duplicate().
2730 */
2731int swapcache_prepare(swp_entry_t entry)
2732{
2733 return __swap_duplicate(entry, SWAP_HAS_CACHE);
2734}
2735
2736struct swap_info_struct *page_swap_info(struct page *page)
2737{
2738 swp_entry_t swap = { .val = page_private(page) };
2739 return swap_info[swp_type(swap)];
2740}
2741
2742/*
2743 * out-of-line __page_file_ methods to avoid include hell.
2744 */
2745struct address_space *__page_file_mapping(struct page *page)
2746{
2747 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
2748 return page_swap_info(page)->swap_file->f_mapping;
2749}
2750EXPORT_SYMBOL_GPL(__page_file_mapping);
2751
2752pgoff_t __page_file_index(struct page *page)
2753{
2754 swp_entry_t swap = { .val = page_private(page) };
2755 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
2756 return swp_offset(swap);
2757}
2758EXPORT_SYMBOL_GPL(__page_file_index);
2759
2760/*
2761 * add_swap_count_continuation - called when a swap count is duplicated
2762 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2763 * page of the original vmalloc'ed swap_map, to hold the continuation count
2764 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2765 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2766 *
2767 * These continuation pages are seldom referenced: the common paths all work
2768 * on the original swap_map, only referring to a continuation page when the
2769 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2770 *
2771 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2772 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2773 * can be called after dropping locks.
2774 */
2775int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2776{
2777 struct swap_info_struct *si;
2778 struct page *head;
2779 struct page *page;
2780 struct page *list_page;
2781 pgoff_t offset;
2782 unsigned char count;
2783
2784 /*
2785 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2786 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2787 */
2788 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2789
2790 si = swap_info_get(entry);
2791 if (!si) {
2792 /*
2793 * An acceptable race has occurred since the failing
2794 * __swap_duplicate(): the swap entry has been freed,
2795 * perhaps even the whole swap_map cleared for swapoff.
2796 */
2797 goto outer;
2798 }
2799
2800 offset = swp_offset(entry);
2801 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2802
2803 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2804 /*
2805 * The higher the swap count, the more likely it is that tasks
2806 * will race to add swap count continuation: we need to avoid
2807 * over-provisioning.
2808 */
2809 goto out;
2810 }
2811
2812 if (!page) {
2813 spin_unlock(&si->lock);
2814 return -ENOMEM;
2815 }
2816
2817 /*
2818 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2819 * no architecture is using highmem pages for kernel page tables: so it
2820 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
2821 */
2822 head = vmalloc_to_page(si->swap_map + offset);
2823 offset &= ~PAGE_MASK;
2824
2825 /*
2826 * Page allocation does not initialize the page's lru field,
2827 * but it does always reset its private field.
2828 */
2829 if (!page_private(head)) {
2830 BUG_ON(count & COUNT_CONTINUED);
2831 INIT_LIST_HEAD(&head->lru);
2832 set_page_private(head, SWP_CONTINUED);
2833 si->flags |= SWP_CONTINUED;
2834 }
2835
2836 list_for_each_entry(list_page, &head->lru, lru) {
2837 unsigned char *map;
2838
2839 /*
2840 * If the previous map said no continuation, but we've found
2841 * a continuation page, free our allocation and use this one.
2842 */
2843 if (!(count & COUNT_CONTINUED))
2844 goto out;
2845
2846 map = kmap_atomic(list_page) + offset;
2847 count = *map;
2848 kunmap_atomic(map);
2849
2850 /*
2851 * If this continuation count now has some space in it,
2852 * free our allocation and use this one.
2853 */
2854 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2855 goto out;
2856 }
2857
2858 list_add_tail(&page->lru, &head->lru);
2859 page = NULL; /* now it's attached, don't free it */
2860out:
2861 spin_unlock(&si->lock);
2862outer:
2863 if (page)
2864 __free_page(page);
2865 return 0;
2866}
2867
2868/*
2869 * swap_count_continued - when the original swap_map count is incremented
2870 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2871 * into, carry if so, or else fail until a new continuation page is allocated;
2872 * when the original swap_map count is decremented from 0 with continuation,
2873 * borrow from the continuation and report whether it still holds more.
2874 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2875 */
2876static bool swap_count_continued(struct swap_info_struct *si,
2877 pgoff_t offset, unsigned char count)
2878{
2879 struct page *head;
2880 struct page *page;
2881 unsigned char *map;
2882
2883 head = vmalloc_to_page(si->swap_map + offset);
2884 if (page_private(head) != SWP_CONTINUED) {
2885 BUG_ON(count & COUNT_CONTINUED);
2886 return false; /* need to add count continuation */
2887 }
2888
2889 offset &= ~PAGE_MASK;
2890 page = list_entry(head->lru.next, struct page, lru);
2891 map = kmap_atomic(page) + offset;
2892
2893 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2894 goto init_map; /* jump over SWAP_CONT_MAX checks */
2895
2896 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2897 /*
2898 * Think of how you add 1 to 999
2899 */
2900 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2901 kunmap_atomic(map);
2902 page = list_entry(page->lru.next, struct page, lru);
2903 BUG_ON(page == head);
2904 map = kmap_atomic(page) + offset;
2905 }
2906 if (*map == SWAP_CONT_MAX) {
2907 kunmap_atomic(map);
2908 page = list_entry(page->lru.next, struct page, lru);
2909 if (page == head)
2910 return false; /* add count continuation */
2911 map = kmap_atomic(page) + offset;
2912init_map: *map = 0; /* we didn't zero the page */
2913 }
2914 *map += 1;
2915 kunmap_atomic(map);
2916 page = list_entry(page->lru.prev, struct page, lru);
2917 while (page != head) {
2918 map = kmap_atomic(page) + offset;
2919 *map = COUNT_CONTINUED;
2920 kunmap_atomic(map);
2921 page = list_entry(page->lru.prev, struct page, lru);
2922 }
2923 return true; /* incremented */
2924
2925 } else { /* decrementing */
2926 /*
2927 * Think of how you subtract 1 from 1000
2928 */
2929 BUG_ON(count != COUNT_CONTINUED);
2930 while (*map == COUNT_CONTINUED) {
2931 kunmap_atomic(map);
2932 page = list_entry(page->lru.next, struct page, lru);
2933 BUG_ON(page == head);
2934 map = kmap_atomic(page) + offset;
2935 }
2936 BUG_ON(*map == 0);
2937 *map -= 1;
2938 if (*map == 0)
2939 count = 0;
2940 kunmap_atomic(map);
2941 page = list_entry(page->lru.prev, struct page, lru);
2942 while (page != head) {
2943 map = kmap_atomic(page) + offset;
2944 *map = SWAP_CONT_MAX | count;
2945 count = COUNT_CONTINUED;
2946 kunmap_atomic(map);
2947 page = list_entry(page->lru.prev, struct page, lru);
2948 }
2949 return count == COUNT_CONTINUED;
2950 }
2951}
2952
2953/*
2954 * free_swap_count_continuations - swapoff free all the continuation pages
2955 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2956 */
2957static void free_swap_count_continuations(struct swap_info_struct *si)
2958{
2959 pgoff_t offset;
2960
2961 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2962 struct page *head;
2963 head = vmalloc_to_page(si->swap_map + offset);
2964 if (page_private(head)) {
2965 struct page *page, *next;
2966
2967 list_for_each_entry_safe(page, next, &head->lru, lru) {
2968 list_del(&page->lru);
2969 __free_page(page);
2970 }
2971 }
2972 }
2973}