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