1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie
9 #include <linux/blkdev.h>
11 #include <linux/sched/mm.h>
12 #include <linux/sched/task.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mman.h>
15 #include <linux/slab.h>
16 #include <linux/kernel_stat.h>
17 #include <linux/swap.h>
18 #include <linux/vmalloc.h>
19 #include <linux/pagemap.h>
20 #include <linux/namei.h>
21 #include <linux/shmem_fs.h>
22 #include <linux/blk-cgroup.h>
23 #include <linux/random.h>
24 #include <linux/writeback.h>
25 #include <linux/proc_fs.h>
26 #include <linux/seq_file.h>
27 #include <linux/init.h>
28 #include <linux/ksm.h>
29 #include <linux/rmap.h>
30 #include <linux/security.h>
31 #include <linux/backing-dev.h>
32 #include <linux/mutex.h>
33 #include <linux/capability.h>
34 #include <linux/syscalls.h>
35 #include <linux/memcontrol.h>
36 #include <linux/poll.h>
37 #include <linux/oom.h>
38 #include <linux/frontswap.h>
39 #include <linux/swapfile.h>
40 #include <linux/export.h>
41 #include <linux/swap_slots.h>
42 #include <linux/sort.h>
43 #include <linux/completion.h>
45 #include <asm/tlbflush.h>
46 #include <linux/swapops.h>
47 #include <linux/swap_cgroup.h>
50 static bool swap_count_continued(struct swap_info_struct
*, pgoff_t
,
52 static void free_swap_count_continuations(struct swap_info_struct
*);
54 static DEFINE_SPINLOCK(swap_lock
);
55 static unsigned int nr_swapfiles
;
56 atomic_long_t nr_swap_pages
;
58 * Some modules use swappable objects and may try to swap them out under
59 * memory pressure (via the shrinker). Before doing so, they may wish to
60 * check to see if any swap space is available.
62 EXPORT_SYMBOL_GPL(nr_swap_pages
);
63 /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
64 long total_swap_pages
;
65 static int least_priority
= -1;
67 static const char Bad_file
[] = "Bad swap file entry ";
68 static const char Unused_file
[] = "Unused swap file entry ";
69 static const char Bad_offset
[] = "Bad swap offset entry ";
70 static const char Unused_offset
[] = "Unused swap offset entry ";
73 * all active swap_info_structs
74 * protected with swap_lock, and ordered by priority.
76 static PLIST_HEAD(swap_active_head
);
79 * all available (active, not full) swap_info_structs
80 * protected with swap_avail_lock, ordered by priority.
81 * This is used by folio_alloc_swap() instead of swap_active_head
82 * because swap_active_head includes all swap_info_structs,
83 * but folio_alloc_swap() doesn't need to look at full ones.
84 * This uses its own lock instead of swap_lock because when a
85 * swap_info_struct changes between not-full/full, it needs to
86 * add/remove itself to/from this list, but the swap_info_struct->lock
87 * is held and the locking order requires swap_lock to be taken
88 * before any swap_info_struct->lock.
90 static struct plist_head
*swap_avail_heads
;
91 static DEFINE_SPINLOCK(swap_avail_lock
);
93 struct swap_info_struct
*swap_info
[MAX_SWAPFILES
];
95 static DEFINE_MUTEX(swapon_mutex
);
97 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait
);
98 /* Activity counter to indicate that a swapon or swapoff has occurred */
99 static atomic_t proc_poll_event
= ATOMIC_INIT(0);
101 atomic_t nr_rotate_swap
= ATOMIC_INIT(0);
103 static struct swap_info_struct
*swap_type_to_swap_info(int type
)
105 if (type
>= MAX_SWAPFILES
)
108 return READ_ONCE(swap_info
[type
]); /* rcu_dereference() */
111 static inline unsigned char swap_count(unsigned char ent
)
113 return ent
& ~SWAP_HAS_CACHE
; /* may include COUNT_CONTINUED flag */
116 /* Reclaim the swap entry anyway if possible */
117 #define TTRS_ANYWAY 0x1
119 * Reclaim the swap entry if there are no more mappings of the
122 #define TTRS_UNMAPPED 0x2
123 /* Reclaim the swap entry if swap is getting full*/
124 #define TTRS_FULL 0x4
126 /* returns 1 if swap entry is freed */
127 static int __try_to_reclaim_swap(struct swap_info_struct
*si
,
128 unsigned long offset
, unsigned long flags
)
130 swp_entry_t entry
= swp_entry(si
->type
, offset
);
134 page
= find_get_page(swap_address_space(entry
), offset
);
138 * When this function is called from scan_swap_map_slots() and it's
139 * called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
140 * here. We have to use trylock for avoiding deadlock. This is a special
141 * case and you should use try_to_free_swap() with explicit lock_page()
142 * in usual operations.
144 if (trylock_page(page
)) {
145 if ((flags
& TTRS_ANYWAY
) ||
146 ((flags
& TTRS_UNMAPPED
) && !page_mapped(page
)) ||
147 ((flags
& TTRS_FULL
) && mem_cgroup_swap_full(page
)))
148 ret
= try_to_free_swap(page
);
155 static inline struct swap_extent
*first_se(struct swap_info_struct
*sis
)
157 struct rb_node
*rb
= rb_first(&sis
->swap_extent_root
);
158 return rb_entry(rb
, struct swap_extent
, rb_node
);
161 static inline struct swap_extent
*next_se(struct swap_extent
*se
)
163 struct rb_node
*rb
= rb_next(&se
->rb_node
);
164 return rb
? rb_entry(rb
, struct swap_extent
, rb_node
) : NULL
;
168 * swapon tell device that all the old swap contents can be discarded,
169 * to allow the swap device to optimize its wear-levelling.
171 static int discard_swap(struct swap_info_struct
*si
)
173 struct swap_extent
*se
;
174 sector_t start_block
;
178 /* Do not discard the swap header page! */
180 start_block
= (se
->start_block
+ 1) << (PAGE_SHIFT
- 9);
181 nr_blocks
= ((sector_t
)se
->nr_pages
- 1) << (PAGE_SHIFT
- 9);
183 err
= blkdev_issue_discard(si
->bdev
, start_block
,
184 nr_blocks
, GFP_KERNEL
);
190 for (se
= next_se(se
); se
; se
= next_se(se
)) {
191 start_block
= se
->start_block
<< (PAGE_SHIFT
- 9);
192 nr_blocks
= (sector_t
)se
->nr_pages
<< (PAGE_SHIFT
- 9);
194 err
= blkdev_issue_discard(si
->bdev
, start_block
,
195 nr_blocks
, GFP_KERNEL
);
201 return err
; /* That will often be -EOPNOTSUPP */
204 static struct swap_extent
*
205 offset_to_swap_extent(struct swap_info_struct
*sis
, unsigned long offset
)
207 struct swap_extent
*se
;
210 rb
= sis
->swap_extent_root
.rb_node
;
212 se
= rb_entry(rb
, struct swap_extent
, rb_node
);
213 if (offset
< se
->start_page
)
215 else if (offset
>= se
->start_page
+ se
->nr_pages
)
220 /* It *must* be present */
224 sector_t
swap_page_sector(struct page
*page
)
226 struct swap_info_struct
*sis
= page_swap_info(page
);
227 struct swap_extent
*se
;
231 offset
= __page_file_index(page
);
232 se
= offset_to_swap_extent(sis
, offset
);
233 sector
= se
->start_block
+ (offset
- se
->start_page
);
234 return sector
<< (PAGE_SHIFT
- 9);
238 * swap allocation tell device that a cluster of swap can now be discarded,
239 * to allow the swap device to optimize its wear-levelling.
241 static void discard_swap_cluster(struct swap_info_struct
*si
,
242 pgoff_t start_page
, pgoff_t nr_pages
)
244 struct swap_extent
*se
= offset_to_swap_extent(si
, start_page
);
247 pgoff_t offset
= start_page
- se
->start_page
;
248 sector_t start_block
= se
->start_block
+ offset
;
249 sector_t nr_blocks
= se
->nr_pages
- offset
;
251 if (nr_blocks
> nr_pages
)
252 nr_blocks
= nr_pages
;
253 start_page
+= nr_blocks
;
254 nr_pages
-= nr_blocks
;
256 start_block
<<= PAGE_SHIFT
- 9;
257 nr_blocks
<<= PAGE_SHIFT
- 9;
258 if (blkdev_issue_discard(si
->bdev
, start_block
,
259 nr_blocks
, GFP_NOIO
))
266 #ifdef CONFIG_THP_SWAP
267 #define SWAPFILE_CLUSTER HPAGE_PMD_NR
269 #define swap_entry_size(size) (size)
271 #define SWAPFILE_CLUSTER 256
274 * Define swap_entry_size() as constant to let compiler to optimize
275 * out some code if !CONFIG_THP_SWAP
277 #define swap_entry_size(size) 1
279 #define LATENCY_LIMIT 256
281 static inline void cluster_set_flag(struct swap_cluster_info
*info
,
287 static inline unsigned int cluster_count(struct swap_cluster_info
*info
)
292 static inline void cluster_set_count(struct swap_cluster_info
*info
,
298 static inline void cluster_set_count_flag(struct swap_cluster_info
*info
,
299 unsigned int c
, unsigned int f
)
305 static inline unsigned int cluster_next(struct swap_cluster_info
*info
)
310 static inline void cluster_set_next(struct swap_cluster_info
*info
,
316 static inline void cluster_set_next_flag(struct swap_cluster_info
*info
,
317 unsigned int n
, unsigned int f
)
323 static inline bool cluster_is_free(struct swap_cluster_info
*info
)
325 return info
->flags
& CLUSTER_FLAG_FREE
;
328 static inline bool cluster_is_null(struct swap_cluster_info
*info
)
330 return info
->flags
& CLUSTER_FLAG_NEXT_NULL
;
333 static inline void cluster_set_null(struct swap_cluster_info
*info
)
335 info
->flags
= CLUSTER_FLAG_NEXT_NULL
;
339 static inline bool cluster_is_huge(struct swap_cluster_info
*info
)
341 if (IS_ENABLED(CONFIG_THP_SWAP
))
342 return info
->flags
& CLUSTER_FLAG_HUGE
;
346 static inline void cluster_clear_huge(struct swap_cluster_info
*info
)
348 info
->flags
&= ~CLUSTER_FLAG_HUGE
;
351 static inline struct swap_cluster_info
*lock_cluster(struct swap_info_struct
*si
,
352 unsigned long offset
)
354 struct swap_cluster_info
*ci
;
356 ci
= si
->cluster_info
;
358 ci
+= offset
/ SWAPFILE_CLUSTER
;
359 spin_lock(&ci
->lock
);
364 static inline void unlock_cluster(struct swap_cluster_info
*ci
)
367 spin_unlock(&ci
->lock
);
371 * Determine the locking method in use for this device. Return
372 * swap_cluster_info if SSD-style cluster-based locking is in place.
374 static inline struct swap_cluster_info
*lock_cluster_or_swap_info(
375 struct swap_info_struct
*si
, unsigned long offset
)
377 struct swap_cluster_info
*ci
;
379 /* Try to use fine-grained SSD-style locking if available: */
380 ci
= lock_cluster(si
, offset
);
381 /* Otherwise, fall back to traditional, coarse locking: */
383 spin_lock(&si
->lock
);
388 static inline void unlock_cluster_or_swap_info(struct swap_info_struct
*si
,
389 struct swap_cluster_info
*ci
)
394 spin_unlock(&si
->lock
);
397 static inline bool cluster_list_empty(struct swap_cluster_list
*list
)
399 return cluster_is_null(&list
->head
);
402 static inline unsigned int cluster_list_first(struct swap_cluster_list
*list
)
404 return cluster_next(&list
->head
);
407 static void cluster_list_init(struct swap_cluster_list
*list
)
409 cluster_set_null(&list
->head
);
410 cluster_set_null(&list
->tail
);
413 static void cluster_list_add_tail(struct swap_cluster_list
*list
,
414 struct swap_cluster_info
*ci
,
417 if (cluster_list_empty(list
)) {
418 cluster_set_next_flag(&list
->head
, idx
, 0);
419 cluster_set_next_flag(&list
->tail
, idx
, 0);
421 struct swap_cluster_info
*ci_tail
;
422 unsigned int tail
= cluster_next(&list
->tail
);
425 * Nested cluster lock, but both cluster locks are
426 * only acquired when we held swap_info_struct->lock
429 spin_lock_nested(&ci_tail
->lock
, SINGLE_DEPTH_NESTING
);
430 cluster_set_next(ci_tail
, idx
);
431 spin_unlock(&ci_tail
->lock
);
432 cluster_set_next_flag(&list
->tail
, idx
, 0);
436 static unsigned int cluster_list_del_first(struct swap_cluster_list
*list
,
437 struct swap_cluster_info
*ci
)
441 idx
= cluster_next(&list
->head
);
442 if (cluster_next(&list
->tail
) == idx
) {
443 cluster_set_null(&list
->head
);
444 cluster_set_null(&list
->tail
);
446 cluster_set_next_flag(&list
->head
,
447 cluster_next(&ci
[idx
]), 0);
452 /* Add a cluster to discard list and schedule it to do discard */
453 static void swap_cluster_schedule_discard(struct swap_info_struct
*si
,
457 * If scan_swap_map_slots() can't find a free cluster, it will check
458 * si->swap_map directly. To make sure the discarding cluster isn't
459 * taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
460 * It will be cleared after discard
462 memset(si
->swap_map
+ idx
* SWAPFILE_CLUSTER
,
463 SWAP_MAP_BAD
, SWAPFILE_CLUSTER
);
465 cluster_list_add_tail(&si
->discard_clusters
, si
->cluster_info
, idx
);
467 schedule_work(&si
->discard_work
);
470 static void __free_cluster(struct swap_info_struct
*si
, unsigned long idx
)
472 struct swap_cluster_info
*ci
= si
->cluster_info
;
474 cluster_set_flag(ci
+ idx
, CLUSTER_FLAG_FREE
);
475 cluster_list_add_tail(&si
->free_clusters
, ci
, idx
);
479 * Doing discard actually. After a cluster discard is finished, the cluster
480 * will be added to free cluster list. caller should hold si->lock.
482 static void swap_do_scheduled_discard(struct swap_info_struct
*si
)
484 struct swap_cluster_info
*info
, *ci
;
487 info
= si
->cluster_info
;
489 while (!cluster_list_empty(&si
->discard_clusters
)) {
490 idx
= cluster_list_del_first(&si
->discard_clusters
, info
);
491 spin_unlock(&si
->lock
);
493 discard_swap_cluster(si
, idx
* SWAPFILE_CLUSTER
,
496 spin_lock(&si
->lock
);
497 ci
= lock_cluster(si
, idx
* SWAPFILE_CLUSTER
);
498 __free_cluster(si
, idx
);
499 memset(si
->swap_map
+ idx
* SWAPFILE_CLUSTER
,
500 0, SWAPFILE_CLUSTER
);
505 static void swap_discard_work(struct work_struct
*work
)
507 struct swap_info_struct
*si
;
509 si
= container_of(work
, struct swap_info_struct
, discard_work
);
511 spin_lock(&si
->lock
);
512 swap_do_scheduled_discard(si
);
513 spin_unlock(&si
->lock
);
516 static void swap_users_ref_free(struct percpu_ref
*ref
)
518 struct swap_info_struct
*si
;
520 si
= container_of(ref
, struct swap_info_struct
, users
);
524 static void alloc_cluster(struct swap_info_struct
*si
, unsigned long idx
)
526 struct swap_cluster_info
*ci
= si
->cluster_info
;
528 VM_BUG_ON(cluster_list_first(&si
->free_clusters
) != idx
);
529 cluster_list_del_first(&si
->free_clusters
, ci
);
530 cluster_set_count_flag(ci
+ idx
, 0, 0);
533 static void free_cluster(struct swap_info_struct
*si
, unsigned long idx
)
535 struct swap_cluster_info
*ci
= si
->cluster_info
+ idx
;
537 VM_BUG_ON(cluster_count(ci
) != 0);
539 * If the swap is discardable, prepare discard the cluster
540 * instead of free it immediately. The cluster will be freed
543 if ((si
->flags
& (SWP_WRITEOK
| SWP_PAGE_DISCARD
)) ==
544 (SWP_WRITEOK
| SWP_PAGE_DISCARD
)) {
545 swap_cluster_schedule_discard(si
, idx
);
549 __free_cluster(si
, idx
);
553 * The cluster corresponding to page_nr will be used. The cluster will be
554 * removed from free cluster list and its usage counter will be increased.
556 static void inc_cluster_info_page(struct swap_info_struct
*p
,
557 struct swap_cluster_info
*cluster_info
, unsigned long page_nr
)
559 unsigned long idx
= page_nr
/ SWAPFILE_CLUSTER
;
563 if (cluster_is_free(&cluster_info
[idx
]))
564 alloc_cluster(p
, idx
);
566 VM_BUG_ON(cluster_count(&cluster_info
[idx
]) >= SWAPFILE_CLUSTER
);
567 cluster_set_count(&cluster_info
[idx
],
568 cluster_count(&cluster_info
[idx
]) + 1);
572 * The cluster corresponding to page_nr decreases one usage. If the usage
573 * counter becomes 0, which means no page in the cluster is in using, we can
574 * optionally discard the cluster and add it to free cluster list.
576 static void dec_cluster_info_page(struct swap_info_struct
*p
,
577 struct swap_cluster_info
*cluster_info
, unsigned long page_nr
)
579 unsigned long idx
= page_nr
/ SWAPFILE_CLUSTER
;
584 VM_BUG_ON(cluster_count(&cluster_info
[idx
]) == 0);
585 cluster_set_count(&cluster_info
[idx
],
586 cluster_count(&cluster_info
[idx
]) - 1);
588 if (cluster_count(&cluster_info
[idx
]) == 0)
589 free_cluster(p
, idx
);
593 * It's possible scan_swap_map_slots() uses a free cluster in the middle of free
594 * cluster list. Avoiding such abuse to avoid list corruption.
597 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct
*si
,
598 unsigned long offset
)
600 struct percpu_cluster
*percpu_cluster
;
603 offset
/= SWAPFILE_CLUSTER
;
604 conflict
= !cluster_list_empty(&si
->free_clusters
) &&
605 offset
!= cluster_list_first(&si
->free_clusters
) &&
606 cluster_is_free(&si
->cluster_info
[offset
]);
611 percpu_cluster
= this_cpu_ptr(si
->percpu_cluster
);
612 cluster_set_null(&percpu_cluster
->index
);
617 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
618 * might involve allocating a new cluster for current CPU too.
620 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct
*si
,
621 unsigned long *offset
, unsigned long *scan_base
)
623 struct percpu_cluster
*cluster
;
624 struct swap_cluster_info
*ci
;
625 unsigned long tmp
, max
;
628 cluster
= this_cpu_ptr(si
->percpu_cluster
);
629 if (cluster_is_null(&cluster
->index
)) {
630 if (!cluster_list_empty(&si
->free_clusters
)) {
631 cluster
->index
= si
->free_clusters
.head
;
632 cluster
->next
= cluster_next(&cluster
->index
) *
634 } else if (!cluster_list_empty(&si
->discard_clusters
)) {
636 * we don't have free cluster but have some clusters in
637 * discarding, do discard now and reclaim them, then
638 * reread cluster_next_cpu since we dropped si->lock
640 swap_do_scheduled_discard(si
);
641 *scan_base
= this_cpu_read(*si
->cluster_next_cpu
);
642 *offset
= *scan_base
;
649 * Other CPUs can use our cluster if they can't find a free cluster,
650 * check if there is still free entry in the cluster
653 max
= min_t(unsigned long, si
->max
,
654 (cluster_next(&cluster
->index
) + 1) * SWAPFILE_CLUSTER
);
656 ci
= lock_cluster(si
, tmp
);
658 if (!si
->swap_map
[tmp
])
665 cluster_set_null(&cluster
->index
);
668 cluster
->next
= tmp
+ 1;
674 static void __del_from_avail_list(struct swap_info_struct
*p
)
679 plist_del(&p
->avail_lists
[nid
], &swap_avail_heads
[nid
]);
682 static void del_from_avail_list(struct swap_info_struct
*p
)
684 spin_lock(&swap_avail_lock
);
685 __del_from_avail_list(p
);
686 spin_unlock(&swap_avail_lock
);
689 static void swap_range_alloc(struct swap_info_struct
*si
, unsigned long offset
,
690 unsigned int nr_entries
)
692 unsigned int end
= offset
+ nr_entries
- 1;
694 if (offset
== si
->lowest_bit
)
695 si
->lowest_bit
+= nr_entries
;
696 if (end
== si
->highest_bit
)
697 WRITE_ONCE(si
->highest_bit
, si
->highest_bit
- nr_entries
);
698 WRITE_ONCE(si
->inuse_pages
, si
->inuse_pages
+ nr_entries
);
699 if (si
->inuse_pages
== si
->pages
) {
700 si
->lowest_bit
= si
->max
;
702 del_from_avail_list(si
);
706 static void add_to_avail_list(struct swap_info_struct
*p
)
710 spin_lock(&swap_avail_lock
);
712 WARN_ON(!plist_node_empty(&p
->avail_lists
[nid
]));
713 plist_add(&p
->avail_lists
[nid
], &swap_avail_heads
[nid
]);
715 spin_unlock(&swap_avail_lock
);
718 static void swap_range_free(struct swap_info_struct
*si
, unsigned long offset
,
719 unsigned int nr_entries
)
721 unsigned long begin
= offset
;
722 unsigned long end
= offset
+ nr_entries
- 1;
723 void (*swap_slot_free_notify
)(struct block_device
*, unsigned long);
725 if (offset
< si
->lowest_bit
)
726 si
->lowest_bit
= offset
;
727 if (end
> si
->highest_bit
) {
728 bool was_full
= !si
->highest_bit
;
730 WRITE_ONCE(si
->highest_bit
, end
);
731 if (was_full
&& (si
->flags
& SWP_WRITEOK
))
732 add_to_avail_list(si
);
734 atomic_long_add(nr_entries
, &nr_swap_pages
);
735 WRITE_ONCE(si
->inuse_pages
, si
->inuse_pages
- nr_entries
);
736 if (si
->flags
& SWP_BLKDEV
)
737 swap_slot_free_notify
=
738 si
->bdev
->bd_disk
->fops
->swap_slot_free_notify
;
740 swap_slot_free_notify
= NULL
;
741 while (offset
<= end
) {
742 arch_swap_invalidate_page(si
->type
, offset
);
743 frontswap_invalidate_page(si
->type
, offset
);
744 if (swap_slot_free_notify
)
745 swap_slot_free_notify(si
->bdev
, offset
);
748 clear_shadow_from_swap_cache(si
->type
, begin
, end
);
751 static void set_cluster_next(struct swap_info_struct
*si
, unsigned long next
)
755 if (!(si
->flags
& SWP_SOLIDSTATE
)) {
756 si
->cluster_next
= next
;
760 prev
= this_cpu_read(*si
->cluster_next_cpu
);
762 * Cross the swap address space size aligned trunk, choose
763 * another trunk randomly to avoid lock contention on swap
764 * address space if possible.
766 if ((prev
>> SWAP_ADDRESS_SPACE_SHIFT
) !=
767 (next
>> SWAP_ADDRESS_SPACE_SHIFT
)) {
768 /* No free swap slots available */
769 if (si
->highest_bit
<= si
->lowest_bit
)
771 next
= si
->lowest_bit
+
772 prandom_u32_max(si
->highest_bit
- si
->lowest_bit
+ 1);
773 next
= ALIGN_DOWN(next
, SWAP_ADDRESS_SPACE_PAGES
);
774 next
= max_t(unsigned int, next
, si
->lowest_bit
);
776 this_cpu_write(*si
->cluster_next_cpu
, next
);
779 static bool swap_offset_available_and_locked(struct swap_info_struct
*si
,
780 unsigned long offset
)
782 if (data_race(!si
->swap_map
[offset
])) {
783 spin_lock(&si
->lock
);
787 if (vm_swap_full() && READ_ONCE(si
->swap_map
[offset
]) == SWAP_HAS_CACHE
) {
788 spin_lock(&si
->lock
);
795 static int scan_swap_map_slots(struct swap_info_struct
*si
,
796 unsigned char usage
, int nr
,
799 struct swap_cluster_info
*ci
;
800 unsigned long offset
;
801 unsigned long scan_base
;
802 unsigned long last_in_cluster
= 0;
803 int latency_ration
= LATENCY_LIMIT
;
805 bool scanned_many
= false;
808 * We try to cluster swap pages by allocating them sequentially
809 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
810 * way, however, we resort to first-free allocation, starting
811 * a new cluster. This prevents us from scattering swap pages
812 * all over the entire swap partition, so that we reduce
813 * overall disk seek times between swap pages. -- sct
814 * But we do now try to find an empty cluster. -Andrea
815 * And we let swap pages go all over an SSD partition. Hugh
818 si
->flags
+= SWP_SCANNING
;
820 * Use percpu scan base for SSD to reduce lock contention on
821 * cluster and swap cache. For HDD, sequential access is more
824 if (si
->flags
& SWP_SOLIDSTATE
)
825 scan_base
= this_cpu_read(*si
->cluster_next_cpu
);
827 scan_base
= si
->cluster_next
;
831 if (si
->cluster_info
) {
832 if (!scan_swap_map_try_ssd_cluster(si
, &offset
, &scan_base
))
834 } else if (unlikely(!si
->cluster_nr
--)) {
835 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
) {
836 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
840 spin_unlock(&si
->lock
);
843 * If seek is expensive, start searching for new cluster from
844 * start of partition, to minimize the span of allocated swap.
845 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
846 * case, just handled by scan_swap_map_try_ssd_cluster() above.
848 scan_base
= offset
= si
->lowest_bit
;
849 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
851 /* Locate the first empty (unaligned) cluster */
852 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
853 if (si
->swap_map
[offset
])
854 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
855 else if (offset
== last_in_cluster
) {
856 spin_lock(&si
->lock
);
857 offset
-= SWAPFILE_CLUSTER
- 1;
858 si
->cluster_next
= offset
;
859 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
862 if (unlikely(--latency_ration
< 0)) {
864 latency_ration
= LATENCY_LIMIT
;
869 spin_lock(&si
->lock
);
870 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
874 if (si
->cluster_info
) {
875 while (scan_swap_map_ssd_cluster_conflict(si
, offset
)) {
876 /* take a break if we already got some slots */
879 if (!scan_swap_map_try_ssd_cluster(si
, &offset
,
884 if (!(si
->flags
& SWP_WRITEOK
))
886 if (!si
->highest_bit
)
888 if (offset
> si
->highest_bit
)
889 scan_base
= offset
= si
->lowest_bit
;
891 ci
= lock_cluster(si
, offset
);
892 /* reuse swap entry of cache-only swap if not busy. */
893 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
896 spin_unlock(&si
->lock
);
897 swap_was_freed
= __try_to_reclaim_swap(si
, offset
, TTRS_ANYWAY
);
898 spin_lock(&si
->lock
);
899 /* entry was freed successfully, try to use this again */
902 goto scan
; /* check next one */
905 if (si
->swap_map
[offset
]) {
912 WRITE_ONCE(si
->swap_map
[offset
], usage
);
913 inc_cluster_info_page(si
, si
->cluster_info
, offset
);
916 swap_range_alloc(si
, offset
, 1);
917 slots
[n_ret
++] = swp_entry(si
->type
, offset
);
919 /* got enough slots or reach max slots? */
920 if ((n_ret
== nr
) || (offset
>= si
->highest_bit
))
923 /* search for next available slot */
925 /* time to take a break? */
926 if (unlikely(--latency_ration
< 0)) {
929 spin_unlock(&si
->lock
);
931 spin_lock(&si
->lock
);
932 latency_ration
= LATENCY_LIMIT
;
935 /* try to get more slots in cluster */
936 if (si
->cluster_info
) {
937 if (scan_swap_map_try_ssd_cluster(si
, &offset
, &scan_base
))
939 } else if (si
->cluster_nr
&& !si
->swap_map
[++offset
]) {
940 /* non-ssd case, still more slots in cluster? */
946 * Even if there's no free clusters available (fragmented),
947 * try to scan a little more quickly with lock held unless we
948 * have scanned too many slots already.
951 unsigned long scan_limit
;
953 if (offset
< scan_base
)
954 scan_limit
= scan_base
;
956 scan_limit
= si
->highest_bit
;
957 for (; offset
<= scan_limit
&& --latency_ration
> 0;
959 if (!si
->swap_map
[offset
])
965 set_cluster_next(si
, offset
+ 1);
966 si
->flags
-= SWP_SCANNING
;
970 spin_unlock(&si
->lock
);
971 while (++offset
<= READ_ONCE(si
->highest_bit
)) {
972 if (swap_offset_available_and_locked(si
, offset
))
974 if (unlikely(--latency_ration
< 0)) {
976 latency_ration
= LATENCY_LIMIT
;
980 offset
= si
->lowest_bit
;
981 while (offset
< scan_base
) {
982 if (swap_offset_available_and_locked(si
, offset
))
984 if (unlikely(--latency_ration
< 0)) {
986 latency_ration
= LATENCY_LIMIT
;
991 spin_lock(&si
->lock
);
994 si
->flags
-= SWP_SCANNING
;
998 static int swap_alloc_cluster(struct swap_info_struct
*si
, swp_entry_t
*slot
)
1001 struct swap_cluster_info
*ci
;
1002 unsigned long offset
;
1005 * Should not even be attempting cluster allocations when huge
1006 * page swap is disabled. Warn and fail the allocation.
1008 if (!IS_ENABLED(CONFIG_THP_SWAP
)) {
1013 if (cluster_list_empty(&si
->free_clusters
))
1016 idx
= cluster_list_first(&si
->free_clusters
);
1017 offset
= idx
* SWAPFILE_CLUSTER
;
1018 ci
= lock_cluster(si
, offset
);
1019 alloc_cluster(si
, idx
);
1020 cluster_set_count_flag(ci
, SWAPFILE_CLUSTER
, CLUSTER_FLAG_HUGE
);
1022 memset(si
->swap_map
+ offset
, SWAP_HAS_CACHE
, SWAPFILE_CLUSTER
);
1024 swap_range_alloc(si
, offset
, SWAPFILE_CLUSTER
);
1025 *slot
= swp_entry(si
->type
, offset
);
1030 static void swap_free_cluster(struct swap_info_struct
*si
, unsigned long idx
)
1032 unsigned long offset
= idx
* SWAPFILE_CLUSTER
;
1033 struct swap_cluster_info
*ci
;
1035 ci
= lock_cluster(si
, offset
);
1036 memset(si
->swap_map
+ offset
, 0, SWAPFILE_CLUSTER
);
1037 cluster_set_count_flag(ci
, 0, 0);
1038 free_cluster(si
, idx
);
1040 swap_range_free(si
, offset
, SWAPFILE_CLUSTER
);
1043 int get_swap_pages(int n_goal
, swp_entry_t swp_entries
[], int entry_size
)
1045 unsigned long size
= swap_entry_size(entry_size
);
1046 struct swap_info_struct
*si
, *next
;
1051 /* Only single cluster request supported */
1052 WARN_ON_ONCE(n_goal
> 1 && size
== SWAPFILE_CLUSTER
);
1054 spin_lock(&swap_avail_lock
);
1056 avail_pgs
= atomic_long_read(&nr_swap_pages
) / size
;
1057 if (avail_pgs
<= 0) {
1058 spin_unlock(&swap_avail_lock
);
1062 n_goal
= min3((long)n_goal
, (long)SWAP_BATCH
, avail_pgs
);
1064 atomic_long_sub(n_goal
* size
, &nr_swap_pages
);
1067 node
= numa_node_id();
1068 plist_for_each_entry_safe(si
, next
, &swap_avail_heads
[node
], avail_lists
[node
]) {
1069 /* requeue si to after same-priority siblings */
1070 plist_requeue(&si
->avail_lists
[node
], &swap_avail_heads
[node
]);
1071 spin_unlock(&swap_avail_lock
);
1072 spin_lock(&si
->lock
);
1073 if (!si
->highest_bit
|| !(si
->flags
& SWP_WRITEOK
)) {
1074 spin_lock(&swap_avail_lock
);
1075 if (plist_node_empty(&si
->avail_lists
[node
])) {
1076 spin_unlock(&si
->lock
);
1079 WARN(!si
->highest_bit
,
1080 "swap_info %d in list but !highest_bit\n",
1082 WARN(!(si
->flags
& SWP_WRITEOK
),
1083 "swap_info %d in list but !SWP_WRITEOK\n",
1085 __del_from_avail_list(si
);
1086 spin_unlock(&si
->lock
);
1089 if (size
== SWAPFILE_CLUSTER
) {
1090 if (si
->flags
& SWP_BLKDEV
)
1091 n_ret
= swap_alloc_cluster(si
, swp_entries
);
1093 n_ret
= scan_swap_map_slots(si
, SWAP_HAS_CACHE
,
1094 n_goal
, swp_entries
);
1095 spin_unlock(&si
->lock
);
1096 if (n_ret
|| size
== SWAPFILE_CLUSTER
)
1098 pr_debug("scan_swap_map of si %d failed to find offset\n",
1101 spin_lock(&swap_avail_lock
);
1104 * if we got here, it's likely that si was almost full before,
1105 * and since scan_swap_map_slots() can drop the si->lock,
1106 * multiple callers probably all tried to get a page from the
1107 * same si and it filled up before we could get one; or, the si
1108 * filled up between us dropping swap_avail_lock and taking
1109 * si->lock. Since we dropped the swap_avail_lock, the
1110 * swap_avail_head list may have been modified; so if next is
1111 * still in the swap_avail_head list then try it, otherwise
1112 * start over if we have not gotten any slots.
1114 if (plist_node_empty(&next
->avail_lists
[node
]))
1118 spin_unlock(&swap_avail_lock
);
1122 atomic_long_add((long)(n_goal
- n_ret
) * size
,
1128 static struct swap_info_struct
*_swap_info_get(swp_entry_t entry
)
1130 struct swap_info_struct
*p
;
1131 unsigned long offset
;
1135 p
= swp_swap_info(entry
);
1138 if (data_race(!(p
->flags
& SWP_USED
)))
1140 offset
= swp_offset(entry
);
1141 if (offset
>= p
->max
)
1143 if (data_race(!p
->swap_map
[swp_offset(entry
)]))
1148 pr_err("%s: %s%08lx\n", __func__
, Unused_offset
, entry
.val
);
1151 pr_err("%s: %s%08lx\n", __func__
, Bad_offset
, entry
.val
);
1154 pr_err("%s: %s%08lx\n", __func__
, Unused_file
, entry
.val
);
1157 pr_err("%s: %s%08lx\n", __func__
, Bad_file
, entry
.val
);
1162 static struct swap_info_struct
*swap_info_get_cont(swp_entry_t entry
,
1163 struct swap_info_struct
*q
)
1165 struct swap_info_struct
*p
;
1167 p
= _swap_info_get(entry
);
1171 spin_unlock(&q
->lock
);
1173 spin_lock(&p
->lock
);
1178 static unsigned char __swap_entry_free_locked(struct swap_info_struct
*p
,
1179 unsigned long offset
,
1180 unsigned char usage
)
1182 unsigned char count
;
1183 unsigned char has_cache
;
1185 count
= p
->swap_map
[offset
];
1187 has_cache
= count
& SWAP_HAS_CACHE
;
1188 count
&= ~SWAP_HAS_CACHE
;
1190 if (usage
== SWAP_HAS_CACHE
) {
1191 VM_BUG_ON(!has_cache
);
1193 } else if (count
== SWAP_MAP_SHMEM
) {
1195 * Or we could insist on shmem.c using a special
1196 * swap_shmem_free() and free_shmem_swap_and_cache()...
1199 } else if ((count
& ~COUNT_CONTINUED
) <= SWAP_MAP_MAX
) {
1200 if (count
== COUNT_CONTINUED
) {
1201 if (swap_count_continued(p
, offset
, count
))
1202 count
= SWAP_MAP_MAX
| COUNT_CONTINUED
;
1204 count
= SWAP_MAP_MAX
;
1209 usage
= count
| has_cache
;
1211 WRITE_ONCE(p
->swap_map
[offset
], usage
);
1213 WRITE_ONCE(p
->swap_map
[offset
], SWAP_HAS_CACHE
);
1219 * Check whether swap entry is valid in the swap device. If so,
1220 * return pointer to swap_info_struct, and keep the swap entry valid
1221 * via preventing the swap device from being swapoff, until
1222 * put_swap_device() is called. Otherwise return NULL.
1224 * Notice that swapoff or swapoff+swapon can still happen before the
1225 * percpu_ref_tryget_live() in get_swap_device() or after the
1226 * percpu_ref_put() in put_swap_device() if there isn't any other way
1227 * to prevent swapoff, such as page lock, page table lock, etc. The
1228 * caller must be prepared for that. For example, the following
1229 * situation is possible.
1233 * ... swapoff+swapon
1234 * __read_swap_cache_async()
1235 * swapcache_prepare()
1236 * __swap_duplicate()
1238 * // verify PTE not changed
1240 * In __swap_duplicate(), the swap_map need to be checked before
1241 * changing partly because the specified swap entry may be for another
1242 * swap device which has been swapoff. And in do_swap_page(), after
1243 * the page is read from the swap device, the PTE is verified not
1244 * changed with the page table locked to check whether the swap device
1245 * has been swapoff or swapoff+swapon.
1247 struct swap_info_struct
*get_swap_device(swp_entry_t entry
)
1249 struct swap_info_struct
*si
;
1250 unsigned long offset
;
1254 si
= swp_swap_info(entry
);
1257 if (!percpu_ref_tryget_live(&si
->users
))
1260 * Guarantee the si->users are checked before accessing other
1261 * fields of swap_info_struct.
1263 * Paired with the spin_unlock() after setup_swap_info() in
1264 * enable_swap_info().
1267 offset
= swp_offset(entry
);
1268 if (offset
>= si
->max
)
1273 pr_err("%s: %s%08lx\n", __func__
, Bad_file
, entry
.val
);
1277 pr_err("%s: %s%08lx\n", __func__
, Bad_offset
, entry
.val
);
1278 percpu_ref_put(&si
->users
);
1282 static unsigned char __swap_entry_free(struct swap_info_struct
*p
,
1285 struct swap_cluster_info
*ci
;
1286 unsigned long offset
= swp_offset(entry
);
1287 unsigned char usage
;
1289 ci
= lock_cluster_or_swap_info(p
, offset
);
1290 usage
= __swap_entry_free_locked(p
, offset
, 1);
1291 unlock_cluster_or_swap_info(p
, ci
);
1293 free_swap_slot(entry
);
1298 static void swap_entry_free(struct swap_info_struct
*p
, swp_entry_t entry
)
1300 struct swap_cluster_info
*ci
;
1301 unsigned long offset
= swp_offset(entry
);
1302 unsigned char count
;
1304 ci
= lock_cluster(p
, offset
);
1305 count
= p
->swap_map
[offset
];
1306 VM_BUG_ON(count
!= SWAP_HAS_CACHE
);
1307 p
->swap_map
[offset
] = 0;
1308 dec_cluster_info_page(p
, p
->cluster_info
, offset
);
1311 mem_cgroup_uncharge_swap(entry
, 1);
1312 swap_range_free(p
, offset
, 1);
1316 * Caller has made sure that the swap device corresponding to entry
1317 * is still around or has not been recycled.
1319 void swap_free(swp_entry_t entry
)
1321 struct swap_info_struct
*p
;
1323 p
= _swap_info_get(entry
);
1325 __swap_entry_free(p
, entry
);
1329 * Called after dropping swapcache to decrease refcnt to swap entries.
1331 void put_swap_page(struct page
*page
, swp_entry_t entry
)
1333 unsigned long offset
= swp_offset(entry
);
1334 unsigned long idx
= offset
/ SWAPFILE_CLUSTER
;
1335 struct swap_cluster_info
*ci
;
1336 struct swap_info_struct
*si
;
1338 unsigned int i
, free_entries
= 0;
1340 int size
= swap_entry_size(thp_nr_pages(page
));
1342 si
= _swap_info_get(entry
);
1346 ci
= lock_cluster_or_swap_info(si
, offset
);
1347 if (size
== SWAPFILE_CLUSTER
) {
1348 VM_BUG_ON(!cluster_is_huge(ci
));
1349 map
= si
->swap_map
+ offset
;
1350 for (i
= 0; i
< SWAPFILE_CLUSTER
; i
++) {
1352 VM_BUG_ON(!(val
& SWAP_HAS_CACHE
));
1353 if (val
== SWAP_HAS_CACHE
)
1356 cluster_clear_huge(ci
);
1357 if (free_entries
== SWAPFILE_CLUSTER
) {
1358 unlock_cluster_or_swap_info(si
, ci
);
1359 spin_lock(&si
->lock
);
1360 mem_cgroup_uncharge_swap(entry
, SWAPFILE_CLUSTER
);
1361 swap_free_cluster(si
, idx
);
1362 spin_unlock(&si
->lock
);
1366 for (i
= 0; i
< size
; i
++, entry
.val
++) {
1367 if (!__swap_entry_free_locked(si
, offset
+ i
, SWAP_HAS_CACHE
)) {
1368 unlock_cluster_or_swap_info(si
, ci
);
1369 free_swap_slot(entry
);
1372 lock_cluster_or_swap_info(si
, offset
);
1375 unlock_cluster_or_swap_info(si
, ci
);
1378 #ifdef CONFIG_THP_SWAP
1379 int split_swap_cluster(swp_entry_t entry
)
1381 struct swap_info_struct
*si
;
1382 struct swap_cluster_info
*ci
;
1383 unsigned long offset
= swp_offset(entry
);
1385 si
= _swap_info_get(entry
);
1388 ci
= lock_cluster(si
, offset
);
1389 cluster_clear_huge(ci
);
1395 static int swp_entry_cmp(const void *ent1
, const void *ent2
)
1397 const swp_entry_t
*e1
= ent1
, *e2
= ent2
;
1399 return (int)swp_type(*e1
) - (int)swp_type(*e2
);
1402 void swapcache_free_entries(swp_entry_t
*entries
, int n
)
1404 struct swap_info_struct
*p
, *prev
;
1414 * Sort swap entries by swap device, so each lock is only taken once.
1415 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1416 * so low that it isn't necessary to optimize further.
1418 if (nr_swapfiles
> 1)
1419 sort(entries
, n
, sizeof(entries
[0]), swp_entry_cmp
, NULL
);
1420 for (i
= 0; i
< n
; ++i
) {
1421 p
= swap_info_get_cont(entries
[i
], prev
);
1423 swap_entry_free(p
, entries
[i
]);
1427 spin_unlock(&p
->lock
);
1431 * How many references to page are currently swapped out?
1432 * This does not give an exact answer when swap count is continued,
1433 * but does include the high COUNT_CONTINUED flag to allow for that.
1435 static int page_swapcount(struct page
*page
)
1438 struct swap_info_struct
*p
;
1439 struct swap_cluster_info
*ci
;
1441 unsigned long offset
;
1443 entry
.val
= page_private(page
);
1444 p
= _swap_info_get(entry
);
1446 offset
= swp_offset(entry
);
1447 ci
= lock_cluster_or_swap_info(p
, offset
);
1448 count
= swap_count(p
->swap_map
[offset
]);
1449 unlock_cluster_or_swap_info(p
, ci
);
1454 int __swap_count(swp_entry_t entry
)
1456 struct swap_info_struct
*si
;
1457 pgoff_t offset
= swp_offset(entry
);
1460 si
= get_swap_device(entry
);
1462 count
= swap_count(si
->swap_map
[offset
]);
1463 put_swap_device(si
);
1468 static int swap_swapcount(struct swap_info_struct
*si
, swp_entry_t entry
)
1471 pgoff_t offset
= swp_offset(entry
);
1472 struct swap_cluster_info
*ci
;
1474 ci
= lock_cluster_or_swap_info(si
, offset
);
1475 count
= swap_count(si
->swap_map
[offset
]);
1476 unlock_cluster_or_swap_info(si
, ci
);
1481 * How many references to @entry are currently swapped out?
1482 * This does not give an exact answer when swap count is continued,
1483 * but does include the high COUNT_CONTINUED flag to allow for that.
1485 int __swp_swapcount(swp_entry_t entry
)
1488 struct swap_info_struct
*si
;
1490 si
= get_swap_device(entry
);
1492 count
= swap_swapcount(si
, entry
);
1493 put_swap_device(si
);
1499 * How many references to @entry are currently swapped out?
1500 * This considers COUNT_CONTINUED so it returns exact answer.
1502 int swp_swapcount(swp_entry_t entry
)
1504 int count
, tmp_count
, n
;
1505 struct swap_info_struct
*p
;
1506 struct swap_cluster_info
*ci
;
1511 p
= _swap_info_get(entry
);
1515 offset
= swp_offset(entry
);
1517 ci
= lock_cluster_or_swap_info(p
, offset
);
1519 count
= swap_count(p
->swap_map
[offset
]);
1520 if (!(count
& COUNT_CONTINUED
))
1523 count
&= ~COUNT_CONTINUED
;
1524 n
= SWAP_MAP_MAX
+ 1;
1526 page
= vmalloc_to_page(p
->swap_map
+ offset
);
1527 offset
&= ~PAGE_MASK
;
1528 VM_BUG_ON(page_private(page
) != SWP_CONTINUED
);
1531 page
= list_next_entry(page
, lru
);
1532 map
= kmap_atomic(page
);
1533 tmp_count
= map
[offset
];
1536 count
+= (tmp_count
& ~COUNT_CONTINUED
) * n
;
1537 n
*= (SWAP_CONT_MAX
+ 1);
1538 } while (tmp_count
& COUNT_CONTINUED
);
1540 unlock_cluster_or_swap_info(p
, ci
);
1544 static bool swap_page_trans_huge_swapped(struct swap_info_struct
*si
,
1547 struct swap_cluster_info
*ci
;
1548 unsigned char *map
= si
->swap_map
;
1549 unsigned long roffset
= swp_offset(entry
);
1550 unsigned long offset
= round_down(roffset
, SWAPFILE_CLUSTER
);
1554 ci
= lock_cluster_or_swap_info(si
, offset
);
1555 if (!ci
|| !cluster_is_huge(ci
)) {
1556 if (swap_count(map
[roffset
]))
1560 for (i
= 0; i
< SWAPFILE_CLUSTER
; i
++) {
1561 if (swap_count(map
[offset
+ i
])) {
1567 unlock_cluster_or_swap_info(si
, ci
);
1571 static bool folio_swapped(struct folio
*folio
)
1574 struct swap_info_struct
*si
;
1576 if (!IS_ENABLED(CONFIG_THP_SWAP
) || likely(!folio_test_large(folio
)))
1577 return page_swapcount(&folio
->page
) != 0;
1579 entry
= folio_swap_entry(folio
);
1580 si
= _swap_info_get(entry
);
1582 return swap_page_trans_huge_swapped(si
, entry
);
1587 * If swap is getting full, or if there are no more mappings of this page,
1588 * then try_to_free_swap is called to free its swap space.
1590 int try_to_free_swap(struct page
*page
)
1592 struct folio
*folio
= page_folio(page
);
1593 VM_BUG_ON_FOLIO(!folio_test_locked(folio
), folio
);
1595 if (!folio_test_swapcache(folio
))
1597 if (folio_test_writeback(folio
))
1599 if (folio_swapped(folio
))
1603 * Once hibernation has begun to create its image of memory,
1604 * there's a danger that one of the calls to try_to_free_swap()
1605 * - most probably a call from __try_to_reclaim_swap() while
1606 * hibernation is allocating its own swap pages for the image,
1607 * but conceivably even a call from memory reclaim - will free
1608 * the swap from a page which has already been recorded in the
1609 * image as a clean swapcache page, and then reuse its swap for
1610 * another page of the image. On waking from hibernation, the
1611 * original page might be freed under memory pressure, then
1612 * later read back in from swap, now with the wrong data.
1614 * Hibernation suspends storage while it is writing the image
1615 * to disk so check that here.
1617 if (pm_suspended_storage())
1620 delete_from_swap_cache(folio
);
1621 folio_set_dirty(folio
);
1626 * Free the swap entry like above, but also try to
1627 * free the page cache entry if it is the last user.
1629 int free_swap_and_cache(swp_entry_t entry
)
1631 struct swap_info_struct
*p
;
1632 unsigned char count
;
1634 if (non_swap_entry(entry
))
1637 p
= _swap_info_get(entry
);
1639 count
= __swap_entry_free(p
, entry
);
1640 if (count
== SWAP_HAS_CACHE
&&
1641 !swap_page_trans_huge_swapped(p
, entry
))
1642 __try_to_reclaim_swap(p
, swp_offset(entry
),
1643 TTRS_UNMAPPED
| TTRS_FULL
);
1648 #ifdef CONFIG_HIBERNATION
1650 swp_entry_t
get_swap_page_of_type(int type
)
1652 struct swap_info_struct
*si
= swap_type_to_swap_info(type
);
1653 swp_entry_t entry
= {0};
1658 /* This is called for allocating swap entry, not cache */
1659 spin_lock(&si
->lock
);
1660 if ((si
->flags
& SWP_WRITEOK
) && scan_swap_map_slots(si
, 1, 1, &entry
))
1661 atomic_long_dec(&nr_swap_pages
);
1662 spin_unlock(&si
->lock
);
1668 * Find the swap type that corresponds to given device (if any).
1670 * @offset - number of the PAGE_SIZE-sized block of the device, starting
1671 * from 0, in which the swap header is expected to be located.
1673 * This is needed for the suspend to disk (aka swsusp).
1675 int swap_type_of(dev_t device
, sector_t offset
)
1682 spin_lock(&swap_lock
);
1683 for (type
= 0; type
< nr_swapfiles
; type
++) {
1684 struct swap_info_struct
*sis
= swap_info
[type
];
1686 if (!(sis
->flags
& SWP_WRITEOK
))
1689 if (device
== sis
->bdev
->bd_dev
) {
1690 struct swap_extent
*se
= first_se(sis
);
1692 if (se
->start_block
== offset
) {
1693 spin_unlock(&swap_lock
);
1698 spin_unlock(&swap_lock
);
1702 int find_first_swap(dev_t
*device
)
1706 spin_lock(&swap_lock
);
1707 for (type
= 0; type
< nr_swapfiles
; type
++) {
1708 struct swap_info_struct
*sis
= swap_info
[type
];
1710 if (!(sis
->flags
& SWP_WRITEOK
))
1712 *device
= sis
->bdev
->bd_dev
;
1713 spin_unlock(&swap_lock
);
1716 spin_unlock(&swap_lock
);
1721 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1722 * corresponding to given index in swap_info (swap type).
1724 sector_t
swapdev_block(int type
, pgoff_t offset
)
1726 struct swap_info_struct
*si
= swap_type_to_swap_info(type
);
1727 struct swap_extent
*se
;
1729 if (!si
|| !(si
->flags
& SWP_WRITEOK
))
1731 se
= offset_to_swap_extent(si
, offset
);
1732 return se
->start_block
+ (offset
- se
->start_page
);
1736 * Return either the total number of swap pages of given type, or the number
1737 * of free pages of that type (depending on @free)
1739 * This is needed for software suspend
1741 unsigned int count_swap_pages(int type
, int free
)
1745 spin_lock(&swap_lock
);
1746 if ((unsigned int)type
< nr_swapfiles
) {
1747 struct swap_info_struct
*sis
= swap_info
[type
];
1749 spin_lock(&sis
->lock
);
1750 if (sis
->flags
& SWP_WRITEOK
) {
1753 n
-= sis
->inuse_pages
;
1755 spin_unlock(&sis
->lock
);
1757 spin_unlock(&swap_lock
);
1760 #endif /* CONFIG_HIBERNATION */
1762 static inline int pte_same_as_swp(pte_t pte
, pte_t swp_pte
)
1764 return pte_same(pte_swp_clear_flags(pte
), swp_pte
);
1768 * No need to decide whether this PTE shares the swap entry with others,
1769 * just let do_wp_page work it out if a write is requested later - to
1770 * force COW, vm_page_prot omits write permission from any private vma.
1772 static int unuse_pte(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1773 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
1775 struct page
*swapcache
;
1777 pte_t
*pte
, new_pte
;
1781 page
= ksm_might_need_to_copy(page
, vma
, addr
);
1782 if (unlikely(!page
))
1785 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
1786 if (unlikely(!pte_same_as_swp(*pte
, swp_entry_to_pte(entry
)))) {
1791 if (unlikely(!PageUptodate(page
))) {
1794 dec_mm_counter(vma
->vm_mm
, MM_SWAPENTS
);
1795 pteval
= swp_entry_to_pte(make_swapin_error_entry(page
));
1796 set_pte_at(vma
->vm_mm
, addr
, pte
, pteval
);
1802 /* See do_swap_page() */
1803 BUG_ON(!PageAnon(page
) && PageMappedToDisk(page
));
1804 BUG_ON(PageAnon(page
) && PageAnonExclusive(page
));
1806 dec_mm_counter(vma
->vm_mm
, MM_SWAPENTS
);
1807 inc_mm_counter(vma
->vm_mm
, MM_ANONPAGES
);
1809 if (page
== swapcache
) {
1810 rmap_t rmap_flags
= RMAP_NONE
;
1813 * See do_swap_page(): PageWriteback() would be problematic.
1814 * However, we do a wait_on_page_writeback() just before this
1815 * call and have the page locked.
1817 VM_BUG_ON_PAGE(PageWriteback(page
), page
);
1818 if (pte_swp_exclusive(*pte
))
1819 rmap_flags
|= RMAP_EXCLUSIVE
;
1821 page_add_anon_rmap(page
, vma
, addr
, rmap_flags
);
1822 } else { /* ksm created a completely new copy */
1823 page_add_new_anon_rmap(page
, vma
, addr
);
1824 lru_cache_add_inactive_or_unevictable(page
, vma
);
1826 new_pte
= pte_mkold(mk_pte(page
, vma
->vm_page_prot
));
1827 if (pte_swp_soft_dirty(*pte
))
1828 new_pte
= pte_mksoft_dirty(new_pte
);
1829 if (pte_swp_uffd_wp(*pte
))
1830 new_pte
= pte_mkuffd_wp(new_pte
);
1831 set_pte_at(vma
->vm_mm
, addr
, pte
, new_pte
);
1834 pte_unmap_unlock(pte
, ptl
);
1835 if (page
!= swapcache
) {
1842 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1843 unsigned long addr
, unsigned long end
,
1849 struct swap_info_struct
*si
;
1850 unsigned long offset
;
1852 volatile unsigned char *swap_map
;
1854 si
= swap_info
[type
];
1855 pte
= pte_offset_map(pmd
, addr
);
1857 if (!is_swap_pte(*pte
))
1860 entry
= pte_to_swp_entry(*pte
);
1861 if (swp_type(entry
) != type
)
1864 offset
= swp_offset(entry
);
1866 swap_map
= &si
->swap_map
[offset
];
1867 page
= lookup_swap_cache(entry
, vma
, addr
);
1869 struct vm_fault vmf
= {
1872 .real_address
= addr
,
1876 page
= swapin_readahead(entry
, GFP_HIGHUSER_MOVABLE
,
1880 if (*swap_map
== 0 || *swap_map
== SWAP_MAP_BAD
)
1886 wait_on_page_writeback(page
);
1887 ret
= unuse_pte(vma
, pmd
, addr
, entry
, page
);
1894 try_to_free_swap(page
);
1898 pte
= pte_offset_map(pmd
, addr
);
1899 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
1907 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
1908 unsigned long addr
, unsigned long end
,
1915 pmd
= pmd_offset(pud
, addr
);
1918 next
= pmd_addr_end(addr
, end
);
1919 if (pmd_none_or_trans_huge_or_clear_bad(pmd
))
1921 ret
= unuse_pte_range(vma
, pmd
, addr
, next
, type
);
1924 } while (pmd
++, addr
= next
, addr
!= end
);
1928 static inline int unuse_pud_range(struct vm_area_struct
*vma
, p4d_t
*p4d
,
1929 unsigned long addr
, unsigned long end
,
1936 pud
= pud_offset(p4d
, addr
);
1938 next
= pud_addr_end(addr
, end
);
1939 if (pud_none_or_clear_bad(pud
))
1941 ret
= unuse_pmd_range(vma
, pud
, addr
, next
, type
);
1944 } while (pud
++, addr
= next
, addr
!= end
);
1948 static inline int unuse_p4d_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
1949 unsigned long addr
, unsigned long end
,
1956 p4d
= p4d_offset(pgd
, addr
);
1958 next
= p4d_addr_end(addr
, end
);
1959 if (p4d_none_or_clear_bad(p4d
))
1961 ret
= unuse_pud_range(vma
, p4d
, addr
, next
, type
);
1964 } while (p4d
++, addr
= next
, addr
!= end
);
1968 static int unuse_vma(struct vm_area_struct
*vma
, unsigned int type
)
1971 unsigned long addr
, end
, next
;
1974 addr
= vma
->vm_start
;
1977 pgd
= pgd_offset(vma
->vm_mm
, addr
);
1979 next
= pgd_addr_end(addr
, end
);
1980 if (pgd_none_or_clear_bad(pgd
))
1982 ret
= unuse_p4d_range(vma
, pgd
, addr
, next
, type
);
1985 } while (pgd
++, addr
= next
, addr
!= end
);
1989 static int unuse_mm(struct mm_struct
*mm
, unsigned int type
)
1991 struct vm_area_struct
*vma
;
1995 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
1996 if (vma
->anon_vma
) {
1997 ret
= unuse_vma(vma
, type
);
2003 mmap_read_unlock(mm
);
2008 * Scan swap_map from current position to next entry still in use.
2009 * Return 0 if there are no inuse entries after prev till end of
2012 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
2016 unsigned char count
;
2019 * No need for swap_lock here: we're just looking
2020 * for whether an entry is in use, not modifying it; false
2021 * hits are okay, and sys_swapoff() has already prevented new
2022 * allocations from this area (while holding swap_lock).
2024 for (i
= prev
+ 1; i
< si
->max
; i
++) {
2025 count
= READ_ONCE(si
->swap_map
[i
]);
2026 if (count
&& swap_count(count
) != SWAP_MAP_BAD
)
2028 if ((i
% LATENCY_LIMIT
) == 0)
2038 static int try_to_unuse(unsigned int type
)
2040 struct mm_struct
*prev_mm
;
2041 struct mm_struct
*mm
;
2042 struct list_head
*p
;
2044 struct swap_info_struct
*si
= swap_info
[type
];
2049 if (!READ_ONCE(si
->inuse_pages
))
2053 retval
= shmem_unuse(type
);
2060 spin_lock(&mmlist_lock
);
2061 p
= &init_mm
.mmlist
;
2062 while (READ_ONCE(si
->inuse_pages
) &&
2063 !signal_pending(current
) &&
2064 (p
= p
->next
) != &init_mm
.mmlist
) {
2066 mm
= list_entry(p
, struct mm_struct
, mmlist
);
2067 if (!mmget_not_zero(mm
))
2069 spin_unlock(&mmlist_lock
);
2072 retval
= unuse_mm(mm
, type
);
2079 * Make sure that we aren't completely killing
2080 * interactive performance.
2083 spin_lock(&mmlist_lock
);
2085 spin_unlock(&mmlist_lock
);
2090 while (READ_ONCE(si
->inuse_pages
) &&
2091 !signal_pending(current
) &&
2092 (i
= find_next_to_unuse(si
, i
)) != 0) {
2094 entry
= swp_entry(type
, i
);
2095 page
= find_get_page(swap_address_space(entry
), i
);
2100 * It is conceivable that a racing task removed this page from
2101 * swap cache just before we acquired the page lock. The page
2102 * might even be back in swap cache on another swap area. But
2103 * that is okay, try_to_free_swap() only removes stale pages.
2106 wait_on_page_writeback(page
);
2107 try_to_free_swap(page
);
2113 * Lets check again to see if there are still swap entries in the map.
2114 * If yes, we would need to do retry the unuse logic again.
2115 * Under global memory pressure, swap entries can be reinserted back
2116 * into process space after the mmlist loop above passes over them.
2118 * Limit the number of retries? No: when mmget_not_zero()
2119 * above fails, that mm is likely to be freeing swap from
2120 * exit_mmap(), which proceeds at its own independent pace;
2121 * and even shmem_writepage() could have been preempted after
2122 * folio_alloc_swap(), temporarily hiding that swap. It's easy
2123 * and robust (though cpu-intensive) just to keep retrying.
2125 if (READ_ONCE(si
->inuse_pages
)) {
2126 if (!signal_pending(current
))
2135 * After a successful try_to_unuse, if no swap is now in use, we know
2136 * we can empty the mmlist. swap_lock must be held on entry and exit.
2137 * Note that mmlist_lock nests inside swap_lock, and an mm must be
2138 * added to the mmlist just after page_duplicate - before would be racy.
2140 static void drain_mmlist(void)
2142 struct list_head
*p
, *next
;
2145 for (type
= 0; type
< nr_swapfiles
; type
++)
2146 if (swap_info
[type
]->inuse_pages
)
2148 spin_lock(&mmlist_lock
);
2149 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
2151 spin_unlock(&mmlist_lock
);
2155 * Free all of a swapdev's extent information
2157 static void destroy_swap_extents(struct swap_info_struct
*sis
)
2159 while (!RB_EMPTY_ROOT(&sis
->swap_extent_root
)) {
2160 struct rb_node
*rb
= sis
->swap_extent_root
.rb_node
;
2161 struct swap_extent
*se
= rb_entry(rb
, struct swap_extent
, rb_node
);
2163 rb_erase(rb
, &sis
->swap_extent_root
);
2167 if (sis
->flags
& SWP_ACTIVATED
) {
2168 struct file
*swap_file
= sis
->swap_file
;
2169 struct address_space
*mapping
= swap_file
->f_mapping
;
2171 sis
->flags
&= ~SWP_ACTIVATED
;
2172 if (mapping
->a_ops
->swap_deactivate
)
2173 mapping
->a_ops
->swap_deactivate(swap_file
);
2178 * Add a block range (and the corresponding page range) into this swapdev's
2181 * This function rather assumes that it is called in ascending page order.
2184 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
2185 unsigned long nr_pages
, sector_t start_block
)
2187 struct rb_node
**link
= &sis
->swap_extent_root
.rb_node
, *parent
= NULL
;
2188 struct swap_extent
*se
;
2189 struct swap_extent
*new_se
;
2192 * place the new node at the right most since the
2193 * function is called in ascending page order.
2197 link
= &parent
->rb_right
;
2201 se
= rb_entry(parent
, struct swap_extent
, rb_node
);
2202 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
2203 if (se
->start_block
+ se
->nr_pages
== start_block
) {
2205 se
->nr_pages
+= nr_pages
;
2210 /* No merge, insert a new extent. */
2211 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
2214 new_se
->start_page
= start_page
;
2215 new_se
->nr_pages
= nr_pages
;
2216 new_se
->start_block
= start_block
;
2218 rb_link_node(&new_se
->rb_node
, parent
, link
);
2219 rb_insert_color(&new_se
->rb_node
, &sis
->swap_extent_root
);
2222 EXPORT_SYMBOL_GPL(add_swap_extent
);
2225 * A `swap extent' is a simple thing which maps a contiguous range of pages
2226 * onto a contiguous range of disk blocks. A rbtree of swap extents is
2227 * built at swapon time and is then used at swap_writepage/swap_readpage
2228 * time for locating where on disk a page belongs.
2230 * If the swapfile is an S_ISBLK block device, a single extent is installed.
2231 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2232 * swap files identically.
2234 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2235 * extent rbtree operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
2236 * swapfiles are handled *identically* after swapon time.
2238 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2239 * and will parse them into a rbtree, in PAGE_SIZE chunks. If some stray
2240 * blocks are found which do not fall within the PAGE_SIZE alignment
2241 * requirements, they are simply tossed out - we will never use those blocks
2244 * For all swap devices we set S_SWAPFILE across the life of the swapon. This
2245 * prevents users from writing to the swap device, which will corrupt memory.
2247 * The amount of disk space which a single swap extent represents varies.
2248 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
2249 * extents in the rbtree. - akpm.
2251 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
2253 struct file
*swap_file
= sis
->swap_file
;
2254 struct address_space
*mapping
= swap_file
->f_mapping
;
2255 struct inode
*inode
= mapping
->host
;
2258 if (S_ISBLK(inode
->i_mode
)) {
2259 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
2264 if (mapping
->a_ops
->swap_activate
) {
2265 ret
= mapping
->a_ops
->swap_activate(sis
, swap_file
, span
);
2268 sis
->flags
|= SWP_ACTIVATED
;
2269 if ((sis
->flags
& SWP_FS_OPS
) &&
2270 sio_pool_init() != 0) {
2271 destroy_swap_extents(sis
);
2277 return generic_swapfile_activate(sis
, swap_file
, span
);
2280 static int swap_node(struct swap_info_struct
*p
)
2282 struct block_device
*bdev
;
2287 bdev
= p
->swap_file
->f_inode
->i_sb
->s_bdev
;
2289 return bdev
? bdev
->bd_disk
->node_id
: NUMA_NO_NODE
;
2292 static void setup_swap_info(struct swap_info_struct
*p
, int prio
,
2293 unsigned char *swap_map
,
2294 struct swap_cluster_info
*cluster_info
)
2301 p
->prio
= --least_priority
;
2303 * the plist prio is negated because plist ordering is
2304 * low-to-high, while swap ordering is high-to-low
2306 p
->list
.prio
= -p
->prio
;
2309 p
->avail_lists
[i
].prio
= -p
->prio
;
2311 if (swap_node(p
) == i
)
2312 p
->avail_lists
[i
].prio
= 1;
2314 p
->avail_lists
[i
].prio
= -p
->prio
;
2317 p
->swap_map
= swap_map
;
2318 p
->cluster_info
= cluster_info
;
2321 static void _enable_swap_info(struct swap_info_struct
*p
)
2323 p
->flags
|= SWP_WRITEOK
;
2324 atomic_long_add(p
->pages
, &nr_swap_pages
);
2325 total_swap_pages
+= p
->pages
;
2327 assert_spin_locked(&swap_lock
);
2329 * both lists are plists, and thus priority ordered.
2330 * swap_active_head needs to be priority ordered for swapoff(),
2331 * which on removal of any swap_info_struct with an auto-assigned
2332 * (i.e. negative) priority increments the auto-assigned priority
2333 * of any lower-priority swap_info_structs.
2334 * swap_avail_head needs to be priority ordered for folio_alloc_swap(),
2335 * which allocates swap pages from the highest available priority
2338 plist_add(&p
->list
, &swap_active_head
);
2339 add_to_avail_list(p
);
2342 static void enable_swap_info(struct swap_info_struct
*p
, int prio
,
2343 unsigned char *swap_map
,
2344 struct swap_cluster_info
*cluster_info
,
2345 unsigned long *frontswap_map
)
2347 if (IS_ENABLED(CONFIG_FRONTSWAP
))
2348 frontswap_init(p
->type
, frontswap_map
);
2349 spin_lock(&swap_lock
);
2350 spin_lock(&p
->lock
);
2351 setup_swap_info(p
, prio
, swap_map
, cluster_info
);
2352 spin_unlock(&p
->lock
);
2353 spin_unlock(&swap_lock
);
2355 * Finished initializing swap device, now it's safe to reference it.
2357 percpu_ref_resurrect(&p
->users
);
2358 spin_lock(&swap_lock
);
2359 spin_lock(&p
->lock
);
2360 _enable_swap_info(p
);
2361 spin_unlock(&p
->lock
);
2362 spin_unlock(&swap_lock
);
2365 static void reinsert_swap_info(struct swap_info_struct
*p
)
2367 spin_lock(&swap_lock
);
2368 spin_lock(&p
->lock
);
2369 setup_swap_info(p
, p
->prio
, p
->swap_map
, p
->cluster_info
);
2370 _enable_swap_info(p
);
2371 spin_unlock(&p
->lock
);
2372 spin_unlock(&swap_lock
);
2375 bool has_usable_swap(void)
2379 spin_lock(&swap_lock
);
2380 if (plist_head_empty(&swap_active_head
))
2382 spin_unlock(&swap_lock
);
2386 SYSCALL_DEFINE1(swapoff
, const char __user
*, specialfile
)
2388 struct swap_info_struct
*p
= NULL
;
2389 unsigned char *swap_map
;
2390 struct swap_cluster_info
*cluster_info
;
2391 unsigned long *frontswap_map
;
2392 struct file
*swap_file
, *victim
;
2393 struct address_space
*mapping
;
2394 struct inode
*inode
;
2395 struct filename
*pathname
;
2397 unsigned int old_block_size
;
2399 if (!capable(CAP_SYS_ADMIN
))
2402 BUG_ON(!current
->mm
);
2404 pathname
= getname(specialfile
);
2405 if (IS_ERR(pathname
))
2406 return PTR_ERR(pathname
);
2408 victim
= file_open_name(pathname
, O_RDWR
|O_LARGEFILE
, 0);
2409 err
= PTR_ERR(victim
);
2413 mapping
= victim
->f_mapping
;
2414 spin_lock(&swap_lock
);
2415 plist_for_each_entry(p
, &swap_active_head
, list
) {
2416 if (p
->flags
& SWP_WRITEOK
) {
2417 if (p
->swap_file
->f_mapping
== mapping
) {
2425 spin_unlock(&swap_lock
);
2428 if (!security_vm_enough_memory_mm(current
->mm
, p
->pages
))
2429 vm_unacct_memory(p
->pages
);
2432 spin_unlock(&swap_lock
);
2435 del_from_avail_list(p
);
2436 spin_lock(&p
->lock
);
2438 struct swap_info_struct
*si
= p
;
2441 plist_for_each_entry_continue(si
, &swap_active_head
, list
) {
2444 for_each_node(nid
) {
2445 if (si
->avail_lists
[nid
].prio
!= 1)
2446 si
->avail_lists
[nid
].prio
--;
2451 plist_del(&p
->list
, &swap_active_head
);
2452 atomic_long_sub(p
->pages
, &nr_swap_pages
);
2453 total_swap_pages
-= p
->pages
;
2454 p
->flags
&= ~SWP_WRITEOK
;
2455 spin_unlock(&p
->lock
);
2456 spin_unlock(&swap_lock
);
2458 disable_swap_slots_cache_lock();
2460 set_current_oom_origin();
2461 err
= try_to_unuse(p
->type
);
2462 clear_current_oom_origin();
2465 /* re-insert swap space back into swap_list */
2466 reinsert_swap_info(p
);
2467 reenable_swap_slots_cache_unlock();
2471 reenable_swap_slots_cache_unlock();
2474 * Wait for swap operations protected by get/put_swap_device()
2477 * We need synchronize_rcu() here to protect the accessing to
2478 * the swap cache data structure.
2480 percpu_ref_kill(&p
->users
);
2482 wait_for_completion(&p
->comp
);
2484 flush_work(&p
->discard_work
);
2486 destroy_swap_extents(p
);
2487 if (p
->flags
& SWP_CONTINUED
)
2488 free_swap_count_continuations(p
);
2490 if (!p
->bdev
|| !bdev_nonrot(p
->bdev
))
2491 atomic_dec(&nr_rotate_swap
);
2493 mutex_lock(&swapon_mutex
);
2494 spin_lock(&swap_lock
);
2495 spin_lock(&p
->lock
);
2498 /* wait for anyone still in scan_swap_map_slots */
2499 p
->highest_bit
= 0; /* cuts scans short */
2500 while (p
->flags
>= SWP_SCANNING
) {
2501 spin_unlock(&p
->lock
);
2502 spin_unlock(&swap_lock
);
2503 schedule_timeout_uninterruptible(1);
2504 spin_lock(&swap_lock
);
2505 spin_lock(&p
->lock
);
2508 swap_file
= p
->swap_file
;
2509 old_block_size
= p
->old_block_size
;
2510 p
->swap_file
= NULL
;
2512 swap_map
= p
->swap_map
;
2514 cluster_info
= p
->cluster_info
;
2515 p
->cluster_info
= NULL
;
2516 frontswap_map
= frontswap_map_get(p
);
2517 spin_unlock(&p
->lock
);
2518 spin_unlock(&swap_lock
);
2519 arch_swap_invalidate_area(p
->type
);
2520 frontswap_invalidate_area(p
->type
);
2521 frontswap_map_set(p
, NULL
);
2522 mutex_unlock(&swapon_mutex
);
2523 free_percpu(p
->percpu_cluster
);
2524 p
->percpu_cluster
= NULL
;
2525 free_percpu(p
->cluster_next_cpu
);
2526 p
->cluster_next_cpu
= NULL
;
2528 kvfree(cluster_info
);
2529 kvfree(frontswap_map
);
2530 /* Destroy swap account information */
2531 swap_cgroup_swapoff(p
->type
);
2532 exit_swap_address_space(p
->type
);
2534 inode
= mapping
->host
;
2535 if (S_ISBLK(inode
->i_mode
)) {
2536 struct block_device
*bdev
= I_BDEV(inode
);
2538 set_blocksize(bdev
, old_block_size
);
2539 blkdev_put(bdev
, FMODE_READ
| FMODE_WRITE
| FMODE_EXCL
);
2543 inode
->i_flags
&= ~S_SWAPFILE
;
2544 inode_unlock(inode
);
2545 filp_close(swap_file
, NULL
);
2548 * Clear the SWP_USED flag after all resources are freed so that swapon
2549 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
2550 * not hold p->lock after we cleared its SWP_WRITEOK.
2552 spin_lock(&swap_lock
);
2554 spin_unlock(&swap_lock
);
2557 atomic_inc(&proc_poll_event
);
2558 wake_up_interruptible(&proc_poll_wait
);
2561 filp_close(victim
, NULL
);
2567 #ifdef CONFIG_PROC_FS
2568 static __poll_t
swaps_poll(struct file
*file
, poll_table
*wait
)
2570 struct seq_file
*seq
= file
->private_data
;
2572 poll_wait(file
, &proc_poll_wait
, wait
);
2574 if (seq
->poll_event
!= atomic_read(&proc_poll_event
)) {
2575 seq
->poll_event
= atomic_read(&proc_poll_event
);
2576 return EPOLLIN
| EPOLLRDNORM
| EPOLLERR
| EPOLLPRI
;
2579 return EPOLLIN
| EPOLLRDNORM
;
2583 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
2585 struct swap_info_struct
*si
;
2589 mutex_lock(&swapon_mutex
);
2592 return SEQ_START_TOKEN
;
2594 for (type
= 0; (si
= swap_type_to_swap_info(type
)); type
++) {
2595 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
2604 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
2606 struct swap_info_struct
*si
= v
;
2609 if (v
== SEQ_START_TOKEN
)
2612 type
= si
->type
+ 1;
2615 for (; (si
= swap_type_to_swap_info(type
)); type
++) {
2616 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
2624 static void swap_stop(struct seq_file
*swap
, void *v
)
2626 mutex_unlock(&swapon_mutex
);
2629 static int swap_show(struct seq_file
*swap
, void *v
)
2631 struct swap_info_struct
*si
= v
;
2634 unsigned long bytes
, inuse
;
2636 if (si
== SEQ_START_TOKEN
) {
2637 seq_puts(swap
, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2641 bytes
= si
->pages
<< (PAGE_SHIFT
- 10);
2642 inuse
= READ_ONCE(si
->inuse_pages
) << (PAGE_SHIFT
- 10);
2644 file
= si
->swap_file
;
2645 len
= seq_file_path(swap
, file
, " \t\n\\");
2646 seq_printf(swap
, "%*s%s\t%lu\t%s%lu\t%s%d\n",
2647 len
< 40 ? 40 - len
: 1, " ",
2648 S_ISBLK(file_inode(file
)->i_mode
) ?
2649 "partition" : "file\t",
2650 bytes
, bytes
< 10000000 ? "\t" : "",
2651 inuse
, inuse
< 10000000 ? "\t" : "",
2656 static const struct seq_operations swaps_op
= {
2657 .start
= swap_start
,
2663 static int swaps_open(struct inode
*inode
, struct file
*file
)
2665 struct seq_file
*seq
;
2668 ret
= seq_open(file
, &swaps_op
);
2672 seq
= file
->private_data
;
2673 seq
->poll_event
= atomic_read(&proc_poll_event
);
2677 static const struct proc_ops swaps_proc_ops
= {
2678 .proc_flags
= PROC_ENTRY_PERMANENT
,
2679 .proc_open
= swaps_open
,
2680 .proc_read
= seq_read
,
2681 .proc_lseek
= seq_lseek
,
2682 .proc_release
= seq_release
,
2683 .proc_poll
= swaps_poll
,
2686 static int __init
procswaps_init(void)
2688 proc_create("swaps", 0, NULL
, &swaps_proc_ops
);
2691 __initcall(procswaps_init
);
2692 #endif /* CONFIG_PROC_FS */
2694 #ifdef MAX_SWAPFILES_CHECK
2695 static int __init
max_swapfiles_check(void)
2697 MAX_SWAPFILES_CHECK();
2700 late_initcall(max_swapfiles_check
);
2703 static struct swap_info_struct
*alloc_swap_info(void)
2705 struct swap_info_struct
*p
;
2706 struct swap_info_struct
*defer
= NULL
;
2710 p
= kvzalloc(struct_size(p
, avail_lists
, nr_node_ids
), GFP_KERNEL
);
2712 return ERR_PTR(-ENOMEM
);
2714 if (percpu_ref_init(&p
->users
, swap_users_ref_free
,
2715 PERCPU_REF_INIT_DEAD
, GFP_KERNEL
)) {
2717 return ERR_PTR(-ENOMEM
);
2720 spin_lock(&swap_lock
);
2721 for (type
= 0; type
< nr_swapfiles
; type
++) {
2722 if (!(swap_info
[type
]->flags
& SWP_USED
))
2725 if (type
>= MAX_SWAPFILES
) {
2726 spin_unlock(&swap_lock
);
2727 percpu_ref_exit(&p
->users
);
2729 return ERR_PTR(-EPERM
);
2731 if (type
>= nr_swapfiles
) {
2734 * Publish the swap_info_struct after initializing it.
2735 * Note that kvzalloc() above zeroes all its fields.
2737 smp_store_release(&swap_info
[type
], p
); /* rcu_assign_pointer() */
2741 p
= swap_info
[type
];
2743 * Do not memset this entry: a racing procfs swap_next()
2744 * would be relying on p->type to remain valid.
2747 p
->swap_extent_root
= RB_ROOT
;
2748 plist_node_init(&p
->list
, 0);
2750 plist_node_init(&p
->avail_lists
[i
], 0);
2751 p
->flags
= SWP_USED
;
2752 spin_unlock(&swap_lock
);
2754 percpu_ref_exit(&defer
->users
);
2757 spin_lock_init(&p
->lock
);
2758 spin_lock_init(&p
->cont_lock
);
2759 init_completion(&p
->comp
);
2764 static int claim_swapfile(struct swap_info_struct
*p
, struct inode
*inode
)
2768 if (S_ISBLK(inode
->i_mode
)) {
2769 p
->bdev
= blkdev_get_by_dev(inode
->i_rdev
,
2770 FMODE_READ
| FMODE_WRITE
| FMODE_EXCL
, p
);
2771 if (IS_ERR(p
->bdev
)) {
2772 error
= PTR_ERR(p
->bdev
);
2776 p
->old_block_size
= block_size(p
->bdev
);
2777 error
= set_blocksize(p
->bdev
, PAGE_SIZE
);
2781 * Zoned block devices contain zones that have a sequential
2782 * write only restriction. Hence zoned block devices are not
2783 * suitable for swapping. Disallow them here.
2785 if (bdev_is_zoned(p
->bdev
))
2787 p
->flags
|= SWP_BLKDEV
;
2788 } else if (S_ISREG(inode
->i_mode
)) {
2789 p
->bdev
= inode
->i_sb
->s_bdev
;
2797 * Find out how many pages are allowed for a single swap device. There
2798 * are two limiting factors:
2799 * 1) the number of bits for the swap offset in the swp_entry_t type, and
2800 * 2) the number of bits in the swap pte, as defined by the different
2803 * In order to find the largest possible bit mask, a swap entry with
2804 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2805 * decoded to a swp_entry_t again, and finally the swap offset is
2808 * This will mask all the bits from the initial ~0UL mask that can't
2809 * be encoded in either the swp_entry_t or the architecture definition
2812 unsigned long generic_max_swapfile_size(void)
2814 return swp_offset(pte_to_swp_entry(
2815 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2818 /* Can be overridden by an architecture for additional checks. */
2819 __weak
unsigned long max_swapfile_size(void)
2821 return generic_max_swapfile_size();
2824 static unsigned long read_swap_header(struct swap_info_struct
*p
,
2825 union swap_header
*swap_header
,
2826 struct inode
*inode
)
2829 unsigned long maxpages
;
2830 unsigned long swapfilepages
;
2831 unsigned long last_page
;
2833 if (memcmp("SWAPSPACE2", swap_header
->magic
.magic
, 10)) {
2834 pr_err("Unable to find swap-space signature\n");
2838 /* swap partition endianness hack... */
2839 if (swab32(swap_header
->info
.version
) == 1) {
2840 swab32s(&swap_header
->info
.version
);
2841 swab32s(&swap_header
->info
.last_page
);
2842 swab32s(&swap_header
->info
.nr_badpages
);
2843 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
2845 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++)
2846 swab32s(&swap_header
->info
.badpages
[i
]);
2848 /* Check the swap header's sub-version */
2849 if (swap_header
->info
.version
!= 1) {
2850 pr_warn("Unable to handle swap header version %d\n",
2851 swap_header
->info
.version
);
2856 p
->cluster_next
= 1;
2859 maxpages
= max_swapfile_size();
2860 last_page
= swap_header
->info
.last_page
;
2862 pr_warn("Empty swap-file\n");
2865 if (last_page
> maxpages
) {
2866 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2867 maxpages
<< (PAGE_SHIFT
- 10),
2868 last_page
<< (PAGE_SHIFT
- 10));
2870 if (maxpages
> last_page
) {
2871 maxpages
= last_page
+ 1;
2872 /* p->max is an unsigned int: don't overflow it */
2873 if ((unsigned int)maxpages
== 0)
2874 maxpages
= UINT_MAX
;
2876 p
->highest_bit
= maxpages
- 1;
2880 swapfilepages
= i_size_read(inode
) >> PAGE_SHIFT
;
2881 if (swapfilepages
&& maxpages
> swapfilepages
) {
2882 pr_warn("Swap area shorter than signature indicates\n");
2885 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
2887 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
2893 #define SWAP_CLUSTER_INFO_COLS \
2894 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
2895 #define SWAP_CLUSTER_SPACE_COLS \
2896 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
2897 #define SWAP_CLUSTER_COLS \
2898 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
2900 static int setup_swap_map_and_extents(struct swap_info_struct
*p
,
2901 union swap_header
*swap_header
,
2902 unsigned char *swap_map
,
2903 struct swap_cluster_info
*cluster_info
,
2904 unsigned long maxpages
,
2908 unsigned int nr_good_pages
;
2910 unsigned long nr_clusters
= DIV_ROUND_UP(maxpages
, SWAPFILE_CLUSTER
);
2911 unsigned long col
= p
->cluster_next
/ SWAPFILE_CLUSTER
% SWAP_CLUSTER_COLS
;
2912 unsigned long i
, idx
;
2914 nr_good_pages
= maxpages
- 1; /* omit header page */
2916 cluster_list_init(&p
->free_clusters
);
2917 cluster_list_init(&p
->discard_clusters
);
2919 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
2920 unsigned int page_nr
= swap_header
->info
.badpages
[i
];
2921 if (page_nr
== 0 || page_nr
> swap_header
->info
.last_page
)
2923 if (page_nr
< maxpages
) {
2924 swap_map
[page_nr
] = SWAP_MAP_BAD
;
2927 * Haven't marked the cluster free yet, no list
2928 * operation involved
2930 inc_cluster_info_page(p
, cluster_info
, page_nr
);
2934 /* Haven't marked the cluster free yet, no list operation involved */
2935 for (i
= maxpages
; i
< round_up(maxpages
, SWAPFILE_CLUSTER
); i
++)
2936 inc_cluster_info_page(p
, cluster_info
, i
);
2938 if (nr_good_pages
) {
2939 swap_map
[0] = SWAP_MAP_BAD
;
2941 * Not mark the cluster free yet, no list
2942 * operation involved
2944 inc_cluster_info_page(p
, cluster_info
, 0);
2946 p
->pages
= nr_good_pages
;
2947 nr_extents
= setup_swap_extents(p
, span
);
2950 nr_good_pages
= p
->pages
;
2952 if (!nr_good_pages
) {
2953 pr_warn("Empty swap-file\n");
2962 * Reduce false cache line sharing between cluster_info and
2963 * sharing same address space.
2965 for (k
= 0; k
< SWAP_CLUSTER_COLS
; k
++) {
2966 j
= (k
+ col
) % SWAP_CLUSTER_COLS
;
2967 for (i
= 0; i
< DIV_ROUND_UP(nr_clusters
, SWAP_CLUSTER_COLS
); i
++) {
2968 idx
= i
* SWAP_CLUSTER_COLS
+ j
;
2969 if (idx
>= nr_clusters
)
2971 if (cluster_count(&cluster_info
[idx
]))
2973 cluster_set_flag(&cluster_info
[idx
], CLUSTER_FLAG_FREE
);
2974 cluster_list_add_tail(&p
->free_clusters
, cluster_info
,
2981 SYSCALL_DEFINE2(swapon
, const char __user
*, specialfile
, int, swap_flags
)
2983 struct swap_info_struct
*p
;
2984 struct filename
*name
;
2985 struct file
*swap_file
= NULL
;
2986 struct address_space
*mapping
;
2987 struct dentry
*dentry
;
2990 union swap_header
*swap_header
;
2993 unsigned long maxpages
;
2994 unsigned char *swap_map
= NULL
;
2995 struct swap_cluster_info
*cluster_info
= NULL
;
2996 unsigned long *frontswap_map
= NULL
;
2997 struct page
*page
= NULL
;
2998 struct inode
*inode
= NULL
;
2999 bool inced_nr_rotate_swap
= false;
3001 if (swap_flags
& ~SWAP_FLAGS_VALID
)
3004 if (!capable(CAP_SYS_ADMIN
))
3007 if (!swap_avail_heads
)
3010 p
= alloc_swap_info();
3014 INIT_WORK(&p
->discard_work
, swap_discard_work
);
3016 name
= getname(specialfile
);
3018 error
= PTR_ERR(name
);
3022 swap_file
= file_open_name(name
, O_RDWR
|O_LARGEFILE
, 0);
3023 if (IS_ERR(swap_file
)) {
3024 error
= PTR_ERR(swap_file
);
3029 p
->swap_file
= swap_file
;
3030 mapping
= swap_file
->f_mapping
;
3031 dentry
= swap_file
->f_path
.dentry
;
3032 inode
= mapping
->host
;
3034 error
= claim_swapfile(p
, inode
);
3035 if (unlikely(error
))
3039 if (d_unlinked(dentry
) || cant_mount(dentry
)) {
3041 goto bad_swap_unlock_inode
;
3043 if (IS_SWAPFILE(inode
)) {
3045 goto bad_swap_unlock_inode
;
3049 * Read the swap header.
3051 if (!mapping
->a_ops
->read_folio
) {
3053 goto bad_swap_unlock_inode
;
3055 page
= read_mapping_page(mapping
, 0, swap_file
);
3057 error
= PTR_ERR(page
);
3058 goto bad_swap_unlock_inode
;
3060 swap_header
= kmap(page
);
3062 maxpages
= read_swap_header(p
, swap_header
, inode
);
3063 if (unlikely(!maxpages
)) {
3065 goto bad_swap_unlock_inode
;
3068 /* OK, set up the swap map and apply the bad block list */
3069 swap_map
= vzalloc(maxpages
);
3072 goto bad_swap_unlock_inode
;
3075 if (p
->bdev
&& bdev_stable_writes(p
->bdev
))
3076 p
->flags
|= SWP_STABLE_WRITES
;
3078 if (p
->bdev
&& p
->bdev
->bd_disk
->fops
->rw_page
)
3079 p
->flags
|= SWP_SYNCHRONOUS_IO
;
3081 if (p
->bdev
&& bdev_nonrot(p
->bdev
)) {
3083 unsigned long ci
, nr_cluster
;
3085 p
->flags
|= SWP_SOLIDSTATE
;
3086 p
->cluster_next_cpu
= alloc_percpu(unsigned int);
3087 if (!p
->cluster_next_cpu
) {
3089 goto bad_swap_unlock_inode
;
3092 * select a random position to start with to help wear leveling
3095 for_each_possible_cpu(cpu
) {
3096 per_cpu(*p
->cluster_next_cpu
, cpu
) =
3097 1 + prandom_u32_max(p
->highest_bit
);
3099 nr_cluster
= DIV_ROUND_UP(maxpages
, SWAPFILE_CLUSTER
);
3101 cluster_info
= kvcalloc(nr_cluster
, sizeof(*cluster_info
),
3103 if (!cluster_info
) {
3105 goto bad_swap_unlock_inode
;
3108 for (ci
= 0; ci
< nr_cluster
; ci
++)
3109 spin_lock_init(&((cluster_info
+ ci
)->lock
));
3111 p
->percpu_cluster
= alloc_percpu(struct percpu_cluster
);
3112 if (!p
->percpu_cluster
) {
3114 goto bad_swap_unlock_inode
;
3116 for_each_possible_cpu(cpu
) {
3117 struct percpu_cluster
*cluster
;
3118 cluster
= per_cpu_ptr(p
->percpu_cluster
, cpu
);
3119 cluster_set_null(&cluster
->index
);
3122 atomic_inc(&nr_rotate_swap
);
3123 inced_nr_rotate_swap
= true;
3126 error
= swap_cgroup_swapon(p
->type
, maxpages
);
3128 goto bad_swap_unlock_inode
;
3130 nr_extents
= setup_swap_map_and_extents(p
, swap_header
, swap_map
,
3131 cluster_info
, maxpages
, &span
);
3132 if (unlikely(nr_extents
< 0)) {
3134 goto bad_swap_unlock_inode
;
3136 /* frontswap enabled? set up bit-per-page map for frontswap */
3137 if (IS_ENABLED(CONFIG_FRONTSWAP
))
3138 frontswap_map
= kvcalloc(BITS_TO_LONGS(maxpages
),
3142 if ((swap_flags
& SWAP_FLAG_DISCARD
) &&
3143 p
->bdev
&& bdev_max_discard_sectors(p
->bdev
)) {
3145 * When discard is enabled for swap with no particular
3146 * policy flagged, we set all swap discard flags here in
3147 * order to sustain backward compatibility with older
3148 * swapon(8) releases.
3150 p
->flags
|= (SWP_DISCARDABLE
| SWP_AREA_DISCARD
|
3154 * By flagging sys_swapon, a sysadmin can tell us to
3155 * either do single-time area discards only, or to just
3156 * perform discards for released swap page-clusters.
3157 * Now it's time to adjust the p->flags accordingly.
3159 if (swap_flags
& SWAP_FLAG_DISCARD_ONCE
)
3160 p
->flags
&= ~SWP_PAGE_DISCARD
;
3161 else if (swap_flags
& SWAP_FLAG_DISCARD_PAGES
)
3162 p
->flags
&= ~SWP_AREA_DISCARD
;
3164 /* issue a swapon-time discard if it's still required */
3165 if (p
->flags
& SWP_AREA_DISCARD
) {
3166 int err
= discard_swap(p
);
3168 pr_err("swapon: discard_swap(%p): %d\n",
3173 error
= init_swap_address_space(p
->type
, maxpages
);
3175 goto bad_swap_unlock_inode
;
3178 * Flush any pending IO and dirty mappings before we start using this
3181 inode
->i_flags
|= S_SWAPFILE
;
3182 error
= inode_drain_writes(inode
);
3184 inode
->i_flags
&= ~S_SWAPFILE
;
3185 goto free_swap_address_space
;
3188 mutex_lock(&swapon_mutex
);
3190 if (swap_flags
& SWAP_FLAG_PREFER
)
3192 (swap_flags
& SWAP_FLAG_PRIO_MASK
) >> SWAP_FLAG_PRIO_SHIFT
;
3193 enable_swap_info(p
, prio
, swap_map
, cluster_info
, frontswap_map
);
3195 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3196 p
->pages
<<(PAGE_SHIFT
-10), name
->name
, p
->prio
,
3197 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10),
3198 (p
->flags
& SWP_SOLIDSTATE
) ? "SS" : "",
3199 (p
->flags
& SWP_DISCARDABLE
) ? "D" : "",
3200 (p
->flags
& SWP_AREA_DISCARD
) ? "s" : "",
3201 (p
->flags
& SWP_PAGE_DISCARD
) ? "c" : "",
3202 (frontswap_map
) ? "FS" : "");
3204 mutex_unlock(&swapon_mutex
);
3205 atomic_inc(&proc_poll_event
);
3206 wake_up_interruptible(&proc_poll_wait
);
3210 free_swap_address_space
:
3211 exit_swap_address_space(p
->type
);
3212 bad_swap_unlock_inode
:
3213 inode_unlock(inode
);
3215 free_percpu(p
->percpu_cluster
);
3216 p
->percpu_cluster
= NULL
;
3217 free_percpu(p
->cluster_next_cpu
);
3218 p
->cluster_next_cpu
= NULL
;
3219 if (inode
&& S_ISBLK(inode
->i_mode
) && p
->bdev
) {
3220 set_blocksize(p
->bdev
, p
->old_block_size
);
3221 blkdev_put(p
->bdev
, FMODE_READ
| FMODE_WRITE
| FMODE_EXCL
);
3224 destroy_swap_extents(p
);
3225 swap_cgroup_swapoff(p
->type
);
3226 spin_lock(&swap_lock
);
3227 p
->swap_file
= NULL
;
3229 spin_unlock(&swap_lock
);
3231 kvfree(cluster_info
);
3232 kvfree(frontswap_map
);
3233 if (inced_nr_rotate_swap
)
3234 atomic_dec(&nr_rotate_swap
);
3236 filp_close(swap_file
, NULL
);
3238 if (page
&& !IS_ERR(page
)) {
3245 inode_unlock(inode
);
3247 enable_swap_slots_cache();
3251 void si_swapinfo(struct sysinfo
*val
)
3254 unsigned long nr_to_be_unused
= 0;
3256 spin_lock(&swap_lock
);
3257 for (type
= 0; type
< nr_swapfiles
; type
++) {
3258 struct swap_info_struct
*si
= swap_info
[type
];
3260 if ((si
->flags
& SWP_USED
) && !(si
->flags
& SWP_WRITEOK
))
3261 nr_to_be_unused
+= READ_ONCE(si
->inuse_pages
);
3263 val
->freeswap
= atomic_long_read(&nr_swap_pages
) + nr_to_be_unused
;
3264 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
3265 spin_unlock(&swap_lock
);
3269 * Verify that a swap entry is valid and increment its swap map count.
3271 * Returns error code in following case.
3273 * - swp_entry is invalid -> EINVAL
3274 * - swp_entry is migration entry -> EINVAL
3275 * - swap-cache reference is requested but there is already one. -> EEXIST
3276 * - swap-cache reference is requested but the entry is not used. -> ENOENT
3277 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3279 static int __swap_duplicate(swp_entry_t entry
, unsigned char usage
)
3281 struct swap_info_struct
*p
;
3282 struct swap_cluster_info
*ci
;
3283 unsigned long offset
;
3284 unsigned char count
;
3285 unsigned char has_cache
;
3288 p
= get_swap_device(entry
);
3292 offset
= swp_offset(entry
);
3293 ci
= lock_cluster_or_swap_info(p
, offset
);
3295 count
= p
->swap_map
[offset
];
3298 * swapin_readahead() doesn't check if a swap entry is valid, so the
3299 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3301 if (unlikely(swap_count(count
) == SWAP_MAP_BAD
)) {
3306 has_cache
= count
& SWAP_HAS_CACHE
;
3307 count
&= ~SWAP_HAS_CACHE
;
3310 if (usage
== SWAP_HAS_CACHE
) {
3312 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3313 if (!has_cache
&& count
)
3314 has_cache
= SWAP_HAS_CACHE
;
3315 else if (has_cache
) /* someone else added cache */
3317 else /* no users remaining */
3320 } else if (count
|| has_cache
) {
3322 if ((count
& ~COUNT_CONTINUED
) < SWAP_MAP_MAX
)
3324 else if ((count
& ~COUNT_CONTINUED
) > SWAP_MAP_MAX
)
3326 else if (swap_count_continued(p
, offset
, count
))
3327 count
= COUNT_CONTINUED
;
3331 err
= -ENOENT
; /* unused swap entry */
3333 WRITE_ONCE(p
->swap_map
[offset
], count
| has_cache
);
3336 unlock_cluster_or_swap_info(p
, ci
);
3342 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3343 * (in which case its reference count is never incremented).
3345 void swap_shmem_alloc(swp_entry_t entry
)
3347 __swap_duplicate(entry
, SWAP_MAP_SHMEM
);
3351 * Increase reference count of swap entry by 1.
3352 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3353 * but could not be atomically allocated. Returns 0, just as if it succeeded,
3354 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3355 * might occur if a page table entry has got corrupted.
3357 int swap_duplicate(swp_entry_t entry
)
3361 while (!err
&& __swap_duplicate(entry
, 1) == -ENOMEM
)
3362 err
= add_swap_count_continuation(entry
, GFP_ATOMIC
);
3367 * @entry: swap entry for which we allocate swap cache.
3369 * Called when allocating swap cache for existing swap entry,
3370 * This can return error codes. Returns 0 at success.
3371 * -EEXIST means there is a swap cache.
3372 * Note: return code is different from swap_duplicate().
3374 int swapcache_prepare(swp_entry_t entry
)
3376 return __swap_duplicate(entry
, SWAP_HAS_CACHE
);
3379 struct swap_info_struct
*swp_swap_info(swp_entry_t entry
)
3381 return swap_type_to_swap_info(swp_type(entry
));
3384 struct swap_info_struct
*page_swap_info(struct page
*page
)
3386 swp_entry_t entry
= { .val
= page_private(page
) };
3387 return swp_swap_info(entry
);
3391 * out-of-line methods to avoid include hell.
3393 struct address_space
*swapcache_mapping(struct folio
*folio
)
3395 return page_swap_info(&folio
->page
)->swap_file
->f_mapping
;
3397 EXPORT_SYMBOL_GPL(swapcache_mapping
);
3399 pgoff_t
__page_file_index(struct page
*page
)
3401 swp_entry_t swap
= { .val
= page_private(page
) };
3402 return swp_offset(swap
);
3404 EXPORT_SYMBOL_GPL(__page_file_index
);
3407 * add_swap_count_continuation - called when a swap count is duplicated
3408 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3409 * page of the original vmalloc'ed swap_map, to hold the continuation count
3410 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
3411 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3413 * These continuation pages are seldom referenced: the common paths all work
3414 * on the original swap_map, only referring to a continuation page when the
3415 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3417 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3418 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3419 * can be called after dropping locks.
3421 int add_swap_count_continuation(swp_entry_t entry
, gfp_t gfp_mask
)
3423 struct swap_info_struct
*si
;
3424 struct swap_cluster_info
*ci
;
3427 struct page
*list_page
;
3429 unsigned char count
;
3433 * When debugging, it's easier to use __GFP_ZERO here; but it's better
3434 * for latency not to zero a page while GFP_ATOMIC and holding locks.
3436 page
= alloc_page(gfp_mask
| __GFP_HIGHMEM
);
3438 si
= get_swap_device(entry
);
3441 * An acceptable race has occurred since the failing
3442 * __swap_duplicate(): the swap device may be swapoff
3446 spin_lock(&si
->lock
);
3448 offset
= swp_offset(entry
);
3450 ci
= lock_cluster(si
, offset
);
3452 count
= swap_count(si
->swap_map
[offset
]);
3454 if ((count
& ~COUNT_CONTINUED
) != SWAP_MAP_MAX
) {
3456 * The higher the swap count, the more likely it is that tasks
3457 * will race to add swap count continuation: we need to avoid
3458 * over-provisioning.
3469 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3470 * no architecture is using highmem pages for kernel page tables: so it
3471 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3473 head
= vmalloc_to_page(si
->swap_map
+ offset
);
3474 offset
&= ~PAGE_MASK
;
3476 spin_lock(&si
->cont_lock
);
3478 * Page allocation does not initialize the page's lru field,
3479 * but it does always reset its private field.
3481 if (!page_private(head
)) {
3482 BUG_ON(count
& COUNT_CONTINUED
);
3483 INIT_LIST_HEAD(&head
->lru
);
3484 set_page_private(head
, SWP_CONTINUED
);
3485 si
->flags
|= SWP_CONTINUED
;
3488 list_for_each_entry(list_page
, &head
->lru
, lru
) {
3492 * If the previous map said no continuation, but we've found
3493 * a continuation page, free our allocation and use this one.
3495 if (!(count
& COUNT_CONTINUED
))
3496 goto out_unlock_cont
;
3498 map
= kmap_atomic(list_page
) + offset
;
3503 * If this continuation count now has some space in it,
3504 * free our allocation and use this one.
3506 if ((count
& ~COUNT_CONTINUED
) != SWAP_CONT_MAX
)
3507 goto out_unlock_cont
;
3510 list_add_tail(&page
->lru
, &head
->lru
);
3511 page
= NULL
; /* now it's attached, don't free it */
3513 spin_unlock(&si
->cont_lock
);
3516 spin_unlock(&si
->lock
);
3517 put_swap_device(si
);
3525 * swap_count_continued - when the original swap_map count is incremented
3526 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3527 * into, carry if so, or else fail until a new continuation page is allocated;
3528 * when the original swap_map count is decremented from 0 with continuation,
3529 * borrow from the continuation and report whether it still holds more.
3530 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3533 static bool swap_count_continued(struct swap_info_struct
*si
,
3534 pgoff_t offset
, unsigned char count
)
3541 head
= vmalloc_to_page(si
->swap_map
+ offset
);
3542 if (page_private(head
) != SWP_CONTINUED
) {
3543 BUG_ON(count
& COUNT_CONTINUED
);
3544 return false; /* need to add count continuation */
3547 spin_lock(&si
->cont_lock
);
3548 offset
&= ~PAGE_MASK
;
3549 page
= list_next_entry(head
, lru
);
3550 map
= kmap_atomic(page
) + offset
;
3552 if (count
== SWAP_MAP_MAX
) /* initial increment from swap_map */
3553 goto init_map
; /* jump over SWAP_CONT_MAX checks */
3555 if (count
== (SWAP_MAP_MAX
| COUNT_CONTINUED
)) { /* incrementing */
3557 * Think of how you add 1 to 999
3559 while (*map
== (SWAP_CONT_MAX
| COUNT_CONTINUED
)) {
3561 page
= list_next_entry(page
, lru
);
3562 BUG_ON(page
== head
);
3563 map
= kmap_atomic(page
) + offset
;
3565 if (*map
== SWAP_CONT_MAX
) {
3567 page
= list_next_entry(page
, lru
);
3569 ret
= false; /* add count continuation */
3572 map
= kmap_atomic(page
) + offset
;
3573 init_map
: *map
= 0; /* we didn't zero the page */
3577 while ((page
= list_prev_entry(page
, lru
)) != head
) {
3578 map
= kmap_atomic(page
) + offset
;
3579 *map
= COUNT_CONTINUED
;
3582 ret
= true; /* incremented */
3584 } else { /* decrementing */
3586 * Think of how you subtract 1 from 1000
3588 BUG_ON(count
!= COUNT_CONTINUED
);
3589 while (*map
== COUNT_CONTINUED
) {
3591 page
= list_next_entry(page
, lru
);
3592 BUG_ON(page
== head
);
3593 map
= kmap_atomic(page
) + offset
;
3600 while ((page
= list_prev_entry(page
, lru
)) != head
) {
3601 map
= kmap_atomic(page
) + offset
;
3602 *map
= SWAP_CONT_MAX
| count
;
3603 count
= COUNT_CONTINUED
;
3606 ret
= count
== COUNT_CONTINUED
;
3609 spin_unlock(&si
->cont_lock
);
3614 * free_swap_count_continuations - swapoff free all the continuation pages
3615 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3617 static void free_swap_count_continuations(struct swap_info_struct
*si
)
3621 for (offset
= 0; offset
< si
->max
; offset
+= PAGE_SIZE
) {
3623 head
= vmalloc_to_page(si
->swap_map
+ offset
);
3624 if (page_private(head
)) {
3625 struct page
*page
, *next
;
3627 list_for_each_entry_safe(page
, next
, &head
->lru
, lru
) {
3628 list_del(&page
->lru
);
3635 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3636 void __cgroup_throttle_swaprate(struct page
*page
, gfp_t gfp_mask
)
3638 struct swap_info_struct
*si
, *next
;
3639 int nid
= page_to_nid(page
);
3641 if (!(gfp_mask
& __GFP_IO
))
3644 if (!blk_cgroup_congested())
3648 * We've already scheduled a throttle, avoid taking the global swap
3651 if (current
->throttle_queue
)
3654 spin_lock(&swap_avail_lock
);
3655 plist_for_each_entry_safe(si
, next
, &swap_avail_heads
[nid
],
3658 blkcg_schedule_throttle(si
->bdev
->bd_disk
, true);
3662 spin_unlock(&swap_avail_lock
);
3666 static int __init
swapfile_init(void)
3670 swap_avail_heads
= kmalloc_array(nr_node_ids
, sizeof(struct plist_head
),
3672 if (!swap_avail_heads
) {
3673 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3678 plist_head_init(&swap_avail_heads
[nid
]);
3682 subsys_initcall(swapfile_init
);