4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
9 #include <linux/hugetlb.h>
10 #include <linux/mman.h>
11 #include <linux/slab.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/swap.h>
14 #include <linux/vmalloc.h>
15 #include <linux/pagemap.h>
16 #include <linux/namei.h>
17 #include <linux/shm.h>
18 #include <linux/blkdev.h>
19 #include <linux/random.h>
20 #include <linux/writeback.h>
21 #include <linux/proc_fs.h>
22 #include <linux/seq_file.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/ksm.h>
26 #include <linux/rmap.h>
27 #include <linux/security.h>
28 #include <linux/backing-dev.h>
29 #include <linux/mutex.h>
30 #include <linux/capability.h>
31 #include <linux/syscalls.h>
32 #include <linux/memcontrol.h>
34 #include <asm/pgtable.h>
35 #include <asm/tlbflush.h>
36 #include <linux/swapops.h>
37 #include <linux/page_cgroup.h>
39 static bool swap_count_continued(struct swap_info_struct
*, pgoff_t
,
41 static void free_swap_count_continuations(struct swap_info_struct
*);
42 static sector_t
map_swap_entry(swp_entry_t
, struct block_device
**);
44 static DEFINE_SPINLOCK(swap_lock
);
45 static unsigned int nr_swapfiles
;
47 long total_swap_pages
;
48 static int least_priority
;
50 static const char Bad_file
[] = "Bad swap file entry ";
51 static const char Unused_file
[] = "Unused swap file entry ";
52 static const char Bad_offset
[] = "Bad swap offset entry ";
53 static const char Unused_offset
[] = "Unused swap offset entry ";
55 static struct swap_list_t swap_list
= {-1, -1};
57 static struct swap_info_struct
*swap_info
[MAX_SWAPFILES
];
59 static DEFINE_MUTEX(swapon_mutex
);
61 static inline unsigned char swap_count(unsigned char ent
)
63 return ent
& ~SWAP_HAS_CACHE
; /* may include SWAP_HAS_CONT flag */
66 /* returns 1 if swap entry is freed */
68 __try_to_reclaim_swap(struct swap_info_struct
*si
, unsigned long offset
)
70 swp_entry_t entry
= swp_entry(si
->type
, offset
);
74 page
= find_get_page(&swapper_space
, entry
.val
);
78 * This function is called from scan_swap_map() and it's called
79 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
80 * We have to use trylock for avoiding deadlock. This is a special
81 * case and you should use try_to_free_swap() with explicit lock_page()
82 * in usual operations.
84 if (trylock_page(page
)) {
85 ret
= try_to_free_swap(page
);
88 page_cache_release(page
);
93 * We need this because the bdev->unplug_fn can sleep and we cannot
94 * hold swap_lock while calling the unplug_fn. And swap_lock
95 * cannot be turned into a mutex.
97 static DECLARE_RWSEM(swap_unplug_sem
);
99 void swap_unplug_io_fn(struct backing_dev_info
*unused_bdi
, struct page
*page
)
103 down_read(&swap_unplug_sem
);
104 entry
.val
= page_private(page
);
105 if (PageSwapCache(page
)) {
106 struct block_device
*bdev
= swap_info
[swp_type(entry
)]->bdev
;
107 struct backing_dev_info
*bdi
;
110 * If the page is removed from swapcache from under us (with a
111 * racy try_to_unuse/swapoff) we need an additional reference
112 * count to avoid reading garbage from page_private(page) above.
113 * If the WARN_ON triggers during a swapoff it maybe the race
114 * condition and it's harmless. However if it triggers without
115 * swapoff it signals a problem.
117 WARN_ON(page_count(page
) <= 1);
119 bdi
= bdev
->bd_inode
->i_mapping
->backing_dev_info
;
120 blk_run_backing_dev(bdi
, page
);
122 up_read(&swap_unplug_sem
);
126 * swapon tell device that all the old swap contents can be discarded,
127 * to allow the swap device to optimize its wear-levelling.
129 static int discard_swap(struct swap_info_struct
*si
)
131 struct swap_extent
*se
;
132 sector_t start_block
;
136 /* Do not discard the swap header page! */
137 se
= &si
->first_swap_extent
;
138 start_block
= (se
->start_block
+ 1) << (PAGE_SHIFT
- 9);
139 nr_blocks
= ((sector_t
)se
->nr_pages
- 1) << (PAGE_SHIFT
- 9);
141 err
= blkdev_issue_discard(si
->bdev
, start_block
,
142 nr_blocks
, GFP_KERNEL
,
143 BLKDEV_IFL_WAIT
| BLKDEV_IFL_BARRIER
);
149 list_for_each_entry(se
, &si
->first_swap_extent
.list
, list
) {
150 start_block
= se
->start_block
<< (PAGE_SHIFT
- 9);
151 nr_blocks
= (sector_t
)se
->nr_pages
<< (PAGE_SHIFT
- 9);
153 err
= blkdev_issue_discard(si
->bdev
, start_block
,
154 nr_blocks
, GFP_KERNEL
,
155 BLKDEV_IFL_WAIT
| BLKDEV_IFL_BARRIER
);
161 return err
; /* That will often be -EOPNOTSUPP */
165 * swap allocation tell device that a cluster of swap can now be discarded,
166 * to allow the swap device to optimize its wear-levelling.
168 static void discard_swap_cluster(struct swap_info_struct
*si
,
169 pgoff_t start_page
, pgoff_t nr_pages
)
171 struct swap_extent
*se
= si
->curr_swap_extent
;
172 int found_extent
= 0;
175 struct list_head
*lh
;
177 if (se
->start_page
<= start_page
&&
178 start_page
< se
->start_page
+ se
->nr_pages
) {
179 pgoff_t offset
= start_page
- se
->start_page
;
180 sector_t start_block
= se
->start_block
+ offset
;
181 sector_t nr_blocks
= se
->nr_pages
- offset
;
183 if (nr_blocks
> nr_pages
)
184 nr_blocks
= nr_pages
;
185 start_page
+= nr_blocks
;
186 nr_pages
-= nr_blocks
;
189 si
->curr_swap_extent
= se
;
191 start_block
<<= PAGE_SHIFT
- 9;
192 nr_blocks
<<= PAGE_SHIFT
- 9;
193 if (blkdev_issue_discard(si
->bdev
, start_block
,
194 nr_blocks
, GFP_NOIO
, BLKDEV_IFL_WAIT
|
200 se
= list_entry(lh
, struct swap_extent
, list
);
204 static int wait_for_discard(void *word
)
210 #define SWAPFILE_CLUSTER 256
211 #define LATENCY_LIMIT 256
213 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
,
216 unsigned long offset
;
217 unsigned long scan_base
;
218 unsigned long last_in_cluster
= 0;
219 int latency_ration
= LATENCY_LIMIT
;
220 int found_free_cluster
= 0;
223 * We try to cluster swap pages by allocating them sequentially
224 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
225 * way, however, we resort to first-free allocation, starting
226 * a new cluster. This prevents us from scattering swap pages
227 * all over the entire swap partition, so that we reduce
228 * overall disk seek times between swap pages. -- sct
229 * But we do now try to find an empty cluster. -Andrea
230 * And we let swap pages go all over an SSD partition. Hugh
233 si
->flags
+= SWP_SCANNING
;
234 scan_base
= offset
= si
->cluster_next
;
236 if (unlikely(!si
->cluster_nr
--)) {
237 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
) {
238 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
241 if (si
->flags
& SWP_DISCARDABLE
) {
243 * Start range check on racing allocations, in case
244 * they overlap the cluster we eventually decide on
245 * (we scan without swap_lock to allow preemption).
246 * It's hardly conceivable that cluster_nr could be
247 * wrapped during our scan, but don't depend on it.
249 if (si
->lowest_alloc
)
251 si
->lowest_alloc
= si
->max
;
252 si
->highest_alloc
= 0;
254 spin_unlock(&swap_lock
);
257 * If seek is expensive, start searching for new cluster from
258 * start of partition, to minimize the span of allocated swap.
259 * But if seek is cheap, search from our current position, so
260 * that swap is allocated from all over the partition: if the
261 * Flash Translation Layer only remaps within limited zones,
262 * we don't want to wear out the first zone too quickly.
264 if (!(si
->flags
& SWP_SOLIDSTATE
))
265 scan_base
= offset
= si
->lowest_bit
;
266 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
268 /* Locate the first empty (unaligned) cluster */
269 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
270 if (si
->swap_map
[offset
])
271 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
272 else if (offset
== last_in_cluster
) {
273 spin_lock(&swap_lock
);
274 offset
-= SWAPFILE_CLUSTER
- 1;
275 si
->cluster_next
= offset
;
276 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
277 found_free_cluster
= 1;
280 if (unlikely(--latency_ration
< 0)) {
282 latency_ration
= LATENCY_LIMIT
;
286 offset
= si
->lowest_bit
;
287 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
289 /* Locate the first empty (unaligned) cluster */
290 for (; last_in_cluster
< scan_base
; offset
++) {
291 if (si
->swap_map
[offset
])
292 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
293 else if (offset
== last_in_cluster
) {
294 spin_lock(&swap_lock
);
295 offset
-= SWAPFILE_CLUSTER
- 1;
296 si
->cluster_next
= offset
;
297 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
298 found_free_cluster
= 1;
301 if (unlikely(--latency_ration
< 0)) {
303 latency_ration
= LATENCY_LIMIT
;
308 spin_lock(&swap_lock
);
309 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
310 si
->lowest_alloc
= 0;
314 if (!(si
->flags
& SWP_WRITEOK
))
316 if (!si
->highest_bit
)
318 if (offset
> si
->highest_bit
)
319 scan_base
= offset
= si
->lowest_bit
;
321 /* reuse swap entry of cache-only swap if not busy. */
322 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
324 spin_unlock(&swap_lock
);
325 swap_was_freed
= __try_to_reclaim_swap(si
, offset
);
326 spin_lock(&swap_lock
);
327 /* entry was freed successfully, try to use this again */
330 goto scan
; /* check next one */
333 if (si
->swap_map
[offset
])
336 if (offset
== si
->lowest_bit
)
338 if (offset
== si
->highest_bit
)
341 if (si
->inuse_pages
== si
->pages
) {
342 si
->lowest_bit
= si
->max
;
345 si
->swap_map
[offset
] = usage
;
346 si
->cluster_next
= offset
+ 1;
347 si
->flags
-= SWP_SCANNING
;
349 if (si
->lowest_alloc
) {
351 * Only set when SWP_DISCARDABLE, and there's a scan
352 * for a free cluster in progress or just completed.
354 if (found_free_cluster
) {
356 * To optimize wear-levelling, discard the
357 * old data of the cluster, taking care not to
358 * discard any of its pages that have already
359 * been allocated by racing tasks (offset has
360 * already stepped over any at the beginning).
362 if (offset
< si
->highest_alloc
&&
363 si
->lowest_alloc
<= last_in_cluster
)
364 last_in_cluster
= si
->lowest_alloc
- 1;
365 si
->flags
|= SWP_DISCARDING
;
366 spin_unlock(&swap_lock
);
368 if (offset
< last_in_cluster
)
369 discard_swap_cluster(si
, offset
,
370 last_in_cluster
- offset
+ 1);
372 spin_lock(&swap_lock
);
373 si
->lowest_alloc
= 0;
374 si
->flags
&= ~SWP_DISCARDING
;
376 smp_mb(); /* wake_up_bit advises this */
377 wake_up_bit(&si
->flags
, ilog2(SWP_DISCARDING
));
379 } else if (si
->flags
& SWP_DISCARDING
) {
381 * Delay using pages allocated by racing tasks
382 * until the whole discard has been issued. We
383 * could defer that delay until swap_writepage,
384 * but it's easier to keep this self-contained.
386 spin_unlock(&swap_lock
);
387 wait_on_bit(&si
->flags
, ilog2(SWP_DISCARDING
),
388 wait_for_discard
, TASK_UNINTERRUPTIBLE
);
389 spin_lock(&swap_lock
);
392 * Note pages allocated by racing tasks while
393 * scan for a free cluster is in progress, so
394 * that its final discard can exclude them.
396 if (offset
< si
->lowest_alloc
)
397 si
->lowest_alloc
= offset
;
398 if (offset
> si
->highest_alloc
)
399 si
->highest_alloc
= offset
;
405 spin_unlock(&swap_lock
);
406 while (++offset
<= si
->highest_bit
) {
407 if (!si
->swap_map
[offset
]) {
408 spin_lock(&swap_lock
);
411 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
412 spin_lock(&swap_lock
);
415 if (unlikely(--latency_ration
< 0)) {
417 latency_ration
= LATENCY_LIMIT
;
420 offset
= si
->lowest_bit
;
421 while (++offset
< scan_base
) {
422 if (!si
->swap_map
[offset
]) {
423 spin_lock(&swap_lock
);
426 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
427 spin_lock(&swap_lock
);
430 if (unlikely(--latency_ration
< 0)) {
432 latency_ration
= LATENCY_LIMIT
;
435 spin_lock(&swap_lock
);
438 si
->flags
-= SWP_SCANNING
;
442 swp_entry_t
get_swap_page(void)
444 struct swap_info_struct
*si
;
449 spin_lock(&swap_lock
);
450 if (nr_swap_pages
<= 0)
454 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
455 si
= swap_info
[type
];
458 (!wrapped
&& si
->prio
!= swap_info
[next
]->prio
)) {
459 next
= swap_list
.head
;
463 if (!si
->highest_bit
)
465 if (!(si
->flags
& SWP_WRITEOK
))
468 swap_list
.next
= next
;
469 /* This is called for allocating swap entry for cache */
470 offset
= scan_swap_map(si
, SWAP_HAS_CACHE
);
472 spin_unlock(&swap_lock
);
473 return swp_entry(type
, offset
);
475 next
= swap_list
.next
;
480 spin_unlock(&swap_lock
);
481 return (swp_entry_t
) {0};
484 /* The only caller of this function is now susupend routine */
485 swp_entry_t
get_swap_page_of_type(int type
)
487 struct swap_info_struct
*si
;
490 spin_lock(&swap_lock
);
491 si
= swap_info
[type
];
492 if (si
&& (si
->flags
& SWP_WRITEOK
)) {
494 /* This is called for allocating swap entry, not cache */
495 offset
= scan_swap_map(si
, 1);
497 spin_unlock(&swap_lock
);
498 return swp_entry(type
, offset
);
502 spin_unlock(&swap_lock
);
503 return (swp_entry_t
) {0};
506 static struct swap_info_struct
*swap_info_get(swp_entry_t entry
)
508 struct swap_info_struct
*p
;
509 unsigned long offset
, type
;
513 type
= swp_type(entry
);
514 if (type
>= nr_swapfiles
)
517 if (!(p
->flags
& SWP_USED
))
519 offset
= swp_offset(entry
);
520 if (offset
>= p
->max
)
522 if (!p
->swap_map
[offset
])
524 spin_lock(&swap_lock
);
528 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
531 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
534 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
537 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
542 static unsigned char swap_entry_free(struct swap_info_struct
*p
,
543 swp_entry_t entry
, unsigned char usage
)
545 unsigned long offset
= swp_offset(entry
);
547 unsigned char has_cache
;
549 count
= p
->swap_map
[offset
];
550 has_cache
= count
& SWAP_HAS_CACHE
;
551 count
&= ~SWAP_HAS_CACHE
;
553 if (usage
== SWAP_HAS_CACHE
) {
554 VM_BUG_ON(!has_cache
);
556 } else if (count
== SWAP_MAP_SHMEM
) {
558 * Or we could insist on shmem.c using a special
559 * swap_shmem_free() and free_shmem_swap_and_cache()...
562 } else if ((count
& ~COUNT_CONTINUED
) <= SWAP_MAP_MAX
) {
563 if (count
== COUNT_CONTINUED
) {
564 if (swap_count_continued(p
, offset
, count
))
565 count
= SWAP_MAP_MAX
| COUNT_CONTINUED
;
567 count
= SWAP_MAP_MAX
;
573 mem_cgroup_uncharge_swap(entry
);
575 usage
= count
| has_cache
;
576 p
->swap_map
[offset
] = usage
;
578 /* free if no reference */
580 if (offset
< p
->lowest_bit
)
581 p
->lowest_bit
= offset
;
582 if (offset
> p
->highest_bit
)
583 p
->highest_bit
= offset
;
584 if (swap_list
.next
>= 0 &&
585 p
->prio
> swap_info
[swap_list
.next
]->prio
)
586 swap_list
.next
= p
->type
;
595 * Caller has made sure that the swapdevice corresponding to entry
596 * is still around or has not been recycled.
598 void swap_free(swp_entry_t entry
)
600 struct swap_info_struct
*p
;
602 p
= swap_info_get(entry
);
604 swap_entry_free(p
, entry
, 1);
605 spin_unlock(&swap_lock
);
610 * Called after dropping swapcache to decrease refcnt to swap entries.
612 void swapcache_free(swp_entry_t entry
, struct page
*page
)
614 struct swap_info_struct
*p
;
617 p
= swap_info_get(entry
);
619 count
= swap_entry_free(p
, entry
, SWAP_HAS_CACHE
);
621 mem_cgroup_uncharge_swapcache(page
, entry
, count
!= 0);
622 spin_unlock(&swap_lock
);
627 * How many references to page are currently swapped out?
628 * This does not give an exact answer when swap count is continued,
629 * but does include the high COUNT_CONTINUED flag to allow for that.
631 static inline int page_swapcount(struct page
*page
)
634 struct swap_info_struct
*p
;
637 entry
.val
= page_private(page
);
638 p
= swap_info_get(entry
);
640 count
= swap_count(p
->swap_map
[swp_offset(entry
)]);
641 spin_unlock(&swap_lock
);
647 * We can write to an anon page without COW if there are no other references
648 * to it. And as a side-effect, free up its swap: because the old content
649 * on disk will never be read, and seeking back there to write new content
650 * later would only waste time away from clustering.
652 int reuse_swap_page(struct page
*page
)
656 VM_BUG_ON(!PageLocked(page
));
657 if (unlikely(PageKsm(page
)))
659 count
= page_mapcount(page
);
660 if (count
<= 1 && PageSwapCache(page
)) {
661 count
+= page_swapcount(page
);
662 if (count
== 1 && !PageWriteback(page
)) {
663 delete_from_swap_cache(page
);
671 * If swap is getting full, or if there are no more mappings of this page,
672 * then try_to_free_swap is called to free its swap space.
674 int try_to_free_swap(struct page
*page
)
676 VM_BUG_ON(!PageLocked(page
));
678 if (!PageSwapCache(page
))
680 if (PageWriteback(page
))
682 if (page_swapcount(page
))
685 delete_from_swap_cache(page
);
691 * Free the swap entry like above, but also try to
692 * free the page cache entry if it is the last user.
694 int free_swap_and_cache(swp_entry_t entry
)
696 struct swap_info_struct
*p
;
697 struct page
*page
= NULL
;
699 if (non_swap_entry(entry
))
702 p
= swap_info_get(entry
);
704 if (swap_entry_free(p
, entry
, 1) == SWAP_HAS_CACHE
) {
705 page
= find_get_page(&swapper_space
, entry
.val
);
706 if (page
&& !trylock_page(page
)) {
707 page_cache_release(page
);
711 spin_unlock(&swap_lock
);
715 * Not mapped elsewhere, or swap space full? Free it!
716 * Also recheck PageSwapCache now page is locked (above).
718 if (PageSwapCache(page
) && !PageWriteback(page
) &&
719 (!page_mapped(page
) || vm_swap_full())) {
720 delete_from_swap_cache(page
);
724 page_cache_release(page
);
729 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
731 * mem_cgroup_count_swap_user - count the user of a swap entry
732 * @ent: the swap entry to be checked
733 * @pagep: the pointer for the swap cache page of the entry to be stored
735 * Returns the number of the user of the swap entry. The number is valid only
736 * for swaps of anonymous pages.
737 * If the entry is found on swap cache, the page is stored to pagep with
738 * refcount of it being incremented.
740 int mem_cgroup_count_swap_user(swp_entry_t ent
, struct page
**pagep
)
743 struct swap_info_struct
*p
;
746 page
= find_get_page(&swapper_space
, ent
.val
);
748 count
+= page_mapcount(page
);
749 p
= swap_info_get(ent
);
751 count
+= swap_count(p
->swap_map
[swp_offset(ent
)]);
752 spin_unlock(&swap_lock
);
760 #ifdef CONFIG_HIBERNATION
762 * Find the swap type that corresponds to given device (if any).
764 * @offset - number of the PAGE_SIZE-sized block of the device, starting
765 * from 0, in which the swap header is expected to be located.
767 * This is needed for the suspend to disk (aka swsusp).
769 int swap_type_of(dev_t device
, sector_t offset
, struct block_device
**bdev_p
)
771 struct block_device
*bdev
= NULL
;
775 bdev
= bdget(device
);
777 spin_lock(&swap_lock
);
778 for (type
= 0; type
< nr_swapfiles
; type
++) {
779 struct swap_info_struct
*sis
= swap_info
[type
];
781 if (!(sis
->flags
& SWP_WRITEOK
))
786 *bdev_p
= bdgrab(sis
->bdev
);
788 spin_unlock(&swap_lock
);
791 if (bdev
== sis
->bdev
) {
792 struct swap_extent
*se
= &sis
->first_swap_extent
;
794 if (se
->start_block
== offset
) {
796 *bdev_p
= bdgrab(sis
->bdev
);
798 spin_unlock(&swap_lock
);
804 spin_unlock(&swap_lock
);
812 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
813 * corresponding to given index in swap_info (swap type).
815 sector_t
swapdev_block(int type
, pgoff_t offset
)
817 struct block_device
*bdev
;
819 if ((unsigned int)type
>= nr_swapfiles
)
821 if (!(swap_info
[type
]->flags
& SWP_WRITEOK
))
823 return map_swap_entry(swp_entry(type
, offset
), &bdev
);
827 * Return either the total number of swap pages of given type, or the number
828 * of free pages of that type (depending on @free)
830 * This is needed for software suspend
832 unsigned int count_swap_pages(int type
, int free
)
836 spin_lock(&swap_lock
);
837 if ((unsigned int)type
< nr_swapfiles
) {
838 struct swap_info_struct
*sis
= swap_info
[type
];
840 if (sis
->flags
& SWP_WRITEOK
) {
843 n
-= sis
->inuse_pages
;
846 spin_unlock(&swap_lock
);
849 #endif /* CONFIG_HIBERNATION */
852 * No need to decide whether this PTE shares the swap entry with others,
853 * just let do_wp_page work it out if a write is requested later - to
854 * force COW, vm_page_prot omits write permission from any private vma.
856 static int unuse_pte(struct vm_area_struct
*vma
, pmd_t
*pmd
,
857 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
859 struct mem_cgroup
*ptr
= NULL
;
864 if (mem_cgroup_try_charge_swapin(vma
->vm_mm
, page
, GFP_KERNEL
, &ptr
)) {
869 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
870 if (unlikely(!pte_same(*pte
, swp_entry_to_pte(entry
)))) {
872 mem_cgroup_cancel_charge_swapin(ptr
);
877 dec_mm_counter(vma
->vm_mm
, MM_SWAPENTS
);
878 inc_mm_counter(vma
->vm_mm
, MM_ANONPAGES
);
880 set_pte_at(vma
->vm_mm
, addr
, pte
,
881 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
882 page_add_anon_rmap(page
, vma
, addr
);
883 mem_cgroup_commit_charge_swapin(page
, ptr
);
886 * Move the page to the active list so it is not
887 * immediately swapped out again after swapon.
891 pte_unmap_unlock(pte
, ptl
);
896 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
897 unsigned long addr
, unsigned long end
,
898 swp_entry_t entry
, struct page
*page
)
900 pte_t swp_pte
= swp_entry_to_pte(entry
);
905 * We don't actually need pte lock while scanning for swp_pte: since
906 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
907 * page table while we're scanning; though it could get zapped, and on
908 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
909 * of unmatched parts which look like swp_pte, so unuse_pte must
910 * recheck under pte lock. Scanning without pte lock lets it be
911 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
913 pte
= pte_offset_map(pmd
, addr
);
916 * swapoff spends a _lot_ of time in this loop!
917 * Test inline before going to call unuse_pte.
919 if (unlikely(pte_same(*pte
, swp_pte
))) {
921 ret
= unuse_pte(vma
, pmd
, addr
, entry
, page
);
924 pte
= pte_offset_map(pmd
, addr
);
926 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
932 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
933 unsigned long addr
, unsigned long end
,
934 swp_entry_t entry
, struct page
*page
)
940 pmd
= pmd_offset(pud
, addr
);
942 next
= pmd_addr_end(addr
, end
);
943 if (pmd_none_or_clear_bad(pmd
))
945 ret
= unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
);
948 } while (pmd
++, addr
= next
, addr
!= end
);
952 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
953 unsigned long addr
, unsigned long end
,
954 swp_entry_t entry
, struct page
*page
)
960 pud
= pud_offset(pgd
, addr
);
962 next
= pud_addr_end(addr
, end
);
963 if (pud_none_or_clear_bad(pud
))
965 ret
= unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
);
968 } while (pud
++, addr
= next
, addr
!= end
);
972 static int unuse_vma(struct vm_area_struct
*vma
,
973 swp_entry_t entry
, struct page
*page
)
976 unsigned long addr
, end
, next
;
979 if (page_anon_vma(page
)) {
980 addr
= page_address_in_vma(page
, vma
);
984 end
= addr
+ PAGE_SIZE
;
986 addr
= vma
->vm_start
;
990 pgd
= pgd_offset(vma
->vm_mm
, addr
);
992 next
= pgd_addr_end(addr
, end
);
993 if (pgd_none_or_clear_bad(pgd
))
995 ret
= unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
);
998 } while (pgd
++, addr
= next
, addr
!= end
);
1002 static int unuse_mm(struct mm_struct
*mm
,
1003 swp_entry_t entry
, struct page
*page
)
1005 struct vm_area_struct
*vma
;
1008 if (!down_read_trylock(&mm
->mmap_sem
)) {
1010 * Activate page so shrink_inactive_list is unlikely to unmap
1011 * its ptes while lock is dropped, so swapoff can make progress.
1013 activate_page(page
);
1015 down_read(&mm
->mmap_sem
);
1018 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
1019 if (vma
->anon_vma
&& (ret
= unuse_vma(vma
, entry
, page
)))
1022 up_read(&mm
->mmap_sem
);
1023 return (ret
< 0)? ret
: 0;
1027 * Scan swap_map from current position to next entry still in use.
1028 * Recycle to start on reaching the end, returning 0 when empty.
1030 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
1033 unsigned int max
= si
->max
;
1034 unsigned int i
= prev
;
1035 unsigned char count
;
1038 * No need for swap_lock here: we're just looking
1039 * for whether an entry is in use, not modifying it; false
1040 * hits are okay, and sys_swapoff() has already prevented new
1041 * allocations from this area (while holding swap_lock).
1050 * No entries in use at top of swap_map,
1051 * loop back to start and recheck there.
1057 count
= si
->swap_map
[i
];
1058 if (count
&& swap_count(count
) != SWAP_MAP_BAD
)
1065 * We completely avoid races by reading each swap page in advance,
1066 * and then search for the process using it. All the necessary
1067 * page table adjustments can then be made atomically.
1069 static int try_to_unuse(unsigned int type
)
1071 struct swap_info_struct
*si
= swap_info
[type
];
1072 struct mm_struct
*start_mm
;
1073 unsigned char *swap_map
;
1074 unsigned char swcount
;
1081 * When searching mms for an entry, a good strategy is to
1082 * start at the first mm we freed the previous entry from
1083 * (though actually we don't notice whether we or coincidence
1084 * freed the entry). Initialize this start_mm with a hold.
1086 * A simpler strategy would be to start at the last mm we
1087 * freed the previous entry from; but that would take less
1088 * advantage of mmlist ordering, which clusters forked mms
1089 * together, child after parent. If we race with dup_mmap(), we
1090 * prefer to resolve parent before child, lest we miss entries
1091 * duplicated after we scanned child: using last mm would invert
1094 start_mm
= &init_mm
;
1095 atomic_inc(&init_mm
.mm_users
);
1098 * Keep on scanning until all entries have gone. Usually,
1099 * one pass through swap_map is enough, but not necessarily:
1100 * there are races when an instance of an entry might be missed.
1102 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
1103 if (signal_pending(current
)) {
1109 * Get a page for the entry, using the existing swap
1110 * cache page if there is one. Otherwise, get a clean
1111 * page and read the swap into it.
1113 swap_map
= &si
->swap_map
[i
];
1114 entry
= swp_entry(type
, i
);
1115 page
= read_swap_cache_async(entry
,
1116 GFP_HIGHUSER_MOVABLE
, NULL
, 0);
1119 * Either swap_duplicate() failed because entry
1120 * has been freed independently, and will not be
1121 * reused since sys_swapoff() already disabled
1122 * allocation from here, or alloc_page() failed.
1131 * Don't hold on to start_mm if it looks like exiting.
1133 if (atomic_read(&start_mm
->mm_users
) == 1) {
1135 start_mm
= &init_mm
;
1136 atomic_inc(&init_mm
.mm_users
);
1140 * Wait for and lock page. When do_swap_page races with
1141 * try_to_unuse, do_swap_page can handle the fault much
1142 * faster than try_to_unuse can locate the entry. This
1143 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1144 * defer to do_swap_page in such a case - in some tests,
1145 * do_swap_page and try_to_unuse repeatedly compete.
1147 wait_on_page_locked(page
);
1148 wait_on_page_writeback(page
);
1150 wait_on_page_writeback(page
);
1153 * Remove all references to entry.
1155 swcount
= *swap_map
;
1156 if (swap_count(swcount
) == SWAP_MAP_SHMEM
) {
1157 retval
= shmem_unuse(entry
, page
);
1158 /* page has already been unlocked and released */
1163 if (swap_count(swcount
) && start_mm
!= &init_mm
)
1164 retval
= unuse_mm(start_mm
, entry
, page
);
1166 if (swap_count(*swap_map
)) {
1167 int set_start_mm
= (*swap_map
>= swcount
);
1168 struct list_head
*p
= &start_mm
->mmlist
;
1169 struct mm_struct
*new_start_mm
= start_mm
;
1170 struct mm_struct
*prev_mm
= start_mm
;
1171 struct mm_struct
*mm
;
1173 atomic_inc(&new_start_mm
->mm_users
);
1174 atomic_inc(&prev_mm
->mm_users
);
1175 spin_lock(&mmlist_lock
);
1176 while (swap_count(*swap_map
) && !retval
&&
1177 (p
= p
->next
) != &start_mm
->mmlist
) {
1178 mm
= list_entry(p
, struct mm_struct
, mmlist
);
1179 if (!atomic_inc_not_zero(&mm
->mm_users
))
1181 spin_unlock(&mmlist_lock
);
1187 swcount
= *swap_map
;
1188 if (!swap_count(swcount
)) /* any usage ? */
1190 else if (mm
== &init_mm
)
1193 retval
= unuse_mm(mm
, entry
, page
);
1195 if (set_start_mm
&& *swap_map
< swcount
) {
1196 mmput(new_start_mm
);
1197 atomic_inc(&mm
->mm_users
);
1201 spin_lock(&mmlist_lock
);
1203 spin_unlock(&mmlist_lock
);
1206 start_mm
= new_start_mm
;
1210 page_cache_release(page
);
1215 * If a reference remains (rare), we would like to leave
1216 * the page in the swap cache; but try_to_unmap could
1217 * then re-duplicate the entry once we drop page lock,
1218 * so we might loop indefinitely; also, that page could
1219 * not be swapped out to other storage meanwhile. So:
1220 * delete from cache even if there's another reference,
1221 * after ensuring that the data has been saved to disk -
1222 * since if the reference remains (rarer), it will be
1223 * read from disk into another page. Splitting into two
1224 * pages would be incorrect if swap supported "shared
1225 * private" pages, but they are handled by tmpfs files.
1227 * Given how unuse_vma() targets one particular offset
1228 * in an anon_vma, once the anon_vma has been determined,
1229 * this splitting happens to be just what is needed to
1230 * handle where KSM pages have been swapped out: re-reading
1231 * is unnecessarily slow, but we can fix that later on.
1233 if (swap_count(*swap_map
) &&
1234 PageDirty(page
) && PageSwapCache(page
)) {
1235 struct writeback_control wbc
= {
1236 .sync_mode
= WB_SYNC_NONE
,
1239 swap_writepage(page
, &wbc
);
1241 wait_on_page_writeback(page
);
1245 * It is conceivable that a racing task removed this page from
1246 * swap cache just before we acquired the page lock at the top,
1247 * or while we dropped it in unuse_mm(). The page might even
1248 * be back in swap cache on another swap area: that we must not
1249 * delete, since it may not have been written out to swap yet.
1251 if (PageSwapCache(page
) &&
1252 likely(page_private(page
) == entry
.val
))
1253 delete_from_swap_cache(page
);
1256 * So we could skip searching mms once swap count went
1257 * to 1, we did not mark any present ptes as dirty: must
1258 * mark page dirty so shrink_page_list will preserve it.
1262 page_cache_release(page
);
1265 * Make sure that we aren't completely killing
1266 * interactive performance.
1276 * After a successful try_to_unuse, if no swap is now in use, we know
1277 * we can empty the mmlist. swap_lock must be held on entry and exit.
1278 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1279 * added to the mmlist just after page_duplicate - before would be racy.
1281 static void drain_mmlist(void)
1283 struct list_head
*p
, *next
;
1286 for (type
= 0; type
< nr_swapfiles
; type
++)
1287 if (swap_info
[type
]->inuse_pages
)
1289 spin_lock(&mmlist_lock
);
1290 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
1292 spin_unlock(&mmlist_lock
);
1296 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1297 * corresponds to page offset for the specified swap entry.
1298 * Note that the type of this function is sector_t, but it returns page offset
1299 * into the bdev, not sector offset.
1301 static sector_t
map_swap_entry(swp_entry_t entry
, struct block_device
**bdev
)
1303 struct swap_info_struct
*sis
;
1304 struct swap_extent
*start_se
;
1305 struct swap_extent
*se
;
1308 sis
= swap_info
[swp_type(entry
)];
1311 offset
= swp_offset(entry
);
1312 start_se
= sis
->curr_swap_extent
;
1316 struct list_head
*lh
;
1318 if (se
->start_page
<= offset
&&
1319 offset
< (se
->start_page
+ se
->nr_pages
)) {
1320 return se
->start_block
+ (offset
- se
->start_page
);
1323 se
= list_entry(lh
, struct swap_extent
, list
);
1324 sis
->curr_swap_extent
= se
;
1325 BUG_ON(se
== start_se
); /* It *must* be present */
1330 * Returns the page offset into bdev for the specified page's swap entry.
1332 sector_t
map_swap_page(struct page
*page
, struct block_device
**bdev
)
1335 entry
.val
= page_private(page
);
1336 return map_swap_entry(entry
, bdev
);
1340 * Free all of a swapdev's extent information
1342 static void destroy_swap_extents(struct swap_info_struct
*sis
)
1344 while (!list_empty(&sis
->first_swap_extent
.list
)) {
1345 struct swap_extent
*se
;
1347 se
= list_entry(sis
->first_swap_extent
.list
.next
,
1348 struct swap_extent
, list
);
1349 list_del(&se
->list
);
1355 * Add a block range (and the corresponding page range) into this swapdev's
1356 * extent list. The extent list is kept sorted in page order.
1358 * This function rather assumes that it is called in ascending page order.
1361 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
1362 unsigned long nr_pages
, sector_t start_block
)
1364 struct swap_extent
*se
;
1365 struct swap_extent
*new_se
;
1366 struct list_head
*lh
;
1368 if (start_page
== 0) {
1369 se
= &sis
->first_swap_extent
;
1370 sis
->curr_swap_extent
= se
;
1372 se
->nr_pages
= nr_pages
;
1373 se
->start_block
= start_block
;
1376 lh
= sis
->first_swap_extent
.list
.prev
; /* Highest extent */
1377 se
= list_entry(lh
, struct swap_extent
, list
);
1378 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
1379 if (se
->start_block
+ se
->nr_pages
== start_block
) {
1381 se
->nr_pages
+= nr_pages
;
1387 * No merge. Insert a new extent, preserving ordering.
1389 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
1392 new_se
->start_page
= start_page
;
1393 new_se
->nr_pages
= nr_pages
;
1394 new_se
->start_block
= start_block
;
1396 list_add_tail(&new_se
->list
, &sis
->first_swap_extent
.list
);
1401 * A `swap extent' is a simple thing which maps a contiguous range of pages
1402 * onto a contiguous range of disk blocks. An ordered list of swap extents
1403 * is built at swapon time and is then used at swap_writepage/swap_readpage
1404 * time for locating where on disk a page belongs.
1406 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1407 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1408 * swap files identically.
1410 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1411 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1412 * swapfiles are handled *identically* after swapon time.
1414 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1415 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1416 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1417 * requirements, they are simply tossed out - we will never use those blocks
1420 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1421 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1422 * which will scribble on the fs.
1424 * The amount of disk space which a single swap extent represents varies.
1425 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1426 * extents in the list. To avoid much list walking, we cache the previous
1427 * search location in `curr_swap_extent', and start new searches from there.
1428 * This is extremely effective. The average number of iterations in
1429 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1431 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1433 struct inode
*inode
;
1434 unsigned blocks_per_page
;
1435 unsigned long page_no
;
1437 sector_t probe_block
;
1438 sector_t last_block
;
1439 sector_t lowest_block
= -1;
1440 sector_t highest_block
= 0;
1444 inode
= sis
->swap_file
->f_mapping
->host
;
1445 if (S_ISBLK(inode
->i_mode
)) {
1446 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1451 blkbits
= inode
->i_blkbits
;
1452 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1455 * Map all the blocks into the extent list. This code doesn't try
1460 last_block
= i_size_read(inode
) >> blkbits
;
1461 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1462 page_no
< sis
->max
) {
1463 unsigned block_in_page
;
1464 sector_t first_block
;
1466 first_block
= bmap(inode
, probe_block
);
1467 if (first_block
== 0)
1471 * It must be PAGE_SIZE aligned on-disk
1473 if (first_block
& (blocks_per_page
- 1)) {
1478 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1482 block
= bmap(inode
, probe_block
+ block_in_page
);
1485 if (block
!= first_block
+ block_in_page
) {
1492 first_block
>>= (PAGE_SHIFT
- blkbits
);
1493 if (page_no
) { /* exclude the header page */
1494 if (first_block
< lowest_block
)
1495 lowest_block
= first_block
;
1496 if (first_block
> highest_block
)
1497 highest_block
= first_block
;
1501 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1503 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1508 probe_block
+= blocks_per_page
;
1513 *span
= 1 + highest_block
- lowest_block
;
1515 page_no
= 1; /* force Empty message */
1517 sis
->pages
= page_no
- 1;
1518 sis
->highest_bit
= page_no
- 1;
1522 printk(KERN_ERR
"swapon: swapfile has holes\n");
1527 SYSCALL_DEFINE1(swapoff
, const char __user
*, specialfile
)
1529 struct swap_info_struct
*p
= NULL
;
1530 unsigned char *swap_map
;
1531 struct file
*swap_file
, *victim
;
1532 struct address_space
*mapping
;
1533 struct inode
*inode
;
1538 if (!capable(CAP_SYS_ADMIN
))
1541 pathname
= getname(specialfile
);
1542 err
= PTR_ERR(pathname
);
1543 if (IS_ERR(pathname
))
1546 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1548 err
= PTR_ERR(victim
);
1552 mapping
= victim
->f_mapping
;
1554 spin_lock(&swap_lock
);
1555 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
]->next
) {
1556 p
= swap_info
[type
];
1557 if (p
->flags
& SWP_WRITEOK
) {
1558 if (p
->swap_file
->f_mapping
== mapping
)
1565 spin_unlock(&swap_lock
);
1568 if (!security_vm_enough_memory(p
->pages
))
1569 vm_unacct_memory(p
->pages
);
1572 spin_unlock(&swap_lock
);
1576 swap_list
.head
= p
->next
;
1578 swap_info
[prev
]->next
= p
->next
;
1579 if (type
== swap_list
.next
) {
1580 /* just pick something that's safe... */
1581 swap_list
.next
= swap_list
.head
;
1584 for (i
= p
->next
; i
>= 0; i
= swap_info
[i
]->next
)
1585 swap_info
[i
]->prio
= p
->prio
--;
1588 nr_swap_pages
-= p
->pages
;
1589 total_swap_pages
-= p
->pages
;
1590 p
->flags
&= ~SWP_WRITEOK
;
1591 spin_unlock(&swap_lock
);
1593 current
->flags
|= PF_OOM_ORIGIN
;
1594 err
= try_to_unuse(type
);
1595 current
->flags
&= ~PF_OOM_ORIGIN
;
1598 /* re-insert swap space back into swap_list */
1599 spin_lock(&swap_lock
);
1601 p
->prio
= --least_priority
;
1603 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
]->next
) {
1604 if (p
->prio
>= swap_info
[i
]->prio
)
1610 swap_list
.head
= swap_list
.next
= type
;
1612 swap_info
[prev
]->next
= type
;
1613 nr_swap_pages
+= p
->pages
;
1614 total_swap_pages
+= p
->pages
;
1615 p
->flags
|= SWP_WRITEOK
;
1616 spin_unlock(&swap_lock
);
1620 /* wait for any unplug function to finish */
1621 down_write(&swap_unplug_sem
);
1622 up_write(&swap_unplug_sem
);
1624 destroy_swap_extents(p
);
1625 if (p
->flags
& SWP_CONTINUED
)
1626 free_swap_count_continuations(p
);
1628 mutex_lock(&swapon_mutex
);
1629 spin_lock(&swap_lock
);
1632 /* wait for anyone still in scan_swap_map */
1633 p
->highest_bit
= 0; /* cuts scans short */
1634 while (p
->flags
>= SWP_SCANNING
) {
1635 spin_unlock(&swap_lock
);
1636 schedule_timeout_uninterruptible(1);
1637 spin_lock(&swap_lock
);
1640 swap_file
= p
->swap_file
;
1641 p
->swap_file
= NULL
;
1643 swap_map
= p
->swap_map
;
1646 spin_unlock(&swap_lock
);
1647 mutex_unlock(&swapon_mutex
);
1649 /* Destroy swap account informatin */
1650 swap_cgroup_swapoff(type
);
1652 inode
= mapping
->host
;
1653 if (S_ISBLK(inode
->i_mode
)) {
1654 struct block_device
*bdev
= I_BDEV(inode
);
1655 set_blocksize(bdev
, p
->old_block_size
);
1658 mutex_lock(&inode
->i_mutex
);
1659 inode
->i_flags
&= ~S_SWAPFILE
;
1660 mutex_unlock(&inode
->i_mutex
);
1662 filp_close(swap_file
, NULL
);
1666 filp_close(victim
, NULL
);
1671 #ifdef CONFIG_PROC_FS
1673 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1675 struct swap_info_struct
*si
;
1679 mutex_lock(&swapon_mutex
);
1682 return SEQ_START_TOKEN
;
1684 for (type
= 0; type
< nr_swapfiles
; type
++) {
1685 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1686 si
= swap_info
[type
];
1687 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1696 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1698 struct swap_info_struct
*si
= v
;
1701 if (v
== SEQ_START_TOKEN
)
1704 type
= si
->type
+ 1;
1706 for (; type
< nr_swapfiles
; type
++) {
1707 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1708 si
= swap_info
[type
];
1709 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1718 static void swap_stop(struct seq_file
*swap
, void *v
)
1720 mutex_unlock(&swapon_mutex
);
1723 static int swap_show(struct seq_file
*swap
, void *v
)
1725 struct swap_info_struct
*si
= v
;
1729 if (si
== SEQ_START_TOKEN
) {
1730 seq_puts(swap
,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1734 file
= si
->swap_file
;
1735 len
= seq_path(swap
, &file
->f_path
, " \t\n\\");
1736 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1737 len
< 40 ? 40 - len
: 1, " ",
1738 S_ISBLK(file
->f_path
.dentry
->d_inode
->i_mode
) ?
1739 "partition" : "file\t",
1740 si
->pages
<< (PAGE_SHIFT
- 10),
1741 si
->inuse_pages
<< (PAGE_SHIFT
- 10),
1746 static const struct seq_operations swaps_op
= {
1747 .start
= swap_start
,
1753 static int swaps_open(struct inode
*inode
, struct file
*file
)
1755 return seq_open(file
, &swaps_op
);
1758 static const struct file_operations proc_swaps_operations
= {
1761 .llseek
= seq_lseek
,
1762 .release
= seq_release
,
1765 static int __init
procswaps_init(void)
1767 proc_create("swaps", 0, NULL
, &proc_swaps_operations
);
1770 __initcall(procswaps_init
);
1771 #endif /* CONFIG_PROC_FS */
1773 #ifdef MAX_SWAPFILES_CHECK
1774 static int __init
max_swapfiles_check(void)
1776 MAX_SWAPFILES_CHECK();
1779 late_initcall(max_swapfiles_check
);
1783 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1785 * The swapon system call
1787 SYSCALL_DEFINE2(swapon
, const char __user
*, specialfile
, int, swap_flags
)
1789 struct swap_info_struct
*p
;
1791 struct block_device
*bdev
= NULL
;
1792 struct file
*swap_file
= NULL
;
1793 struct address_space
*mapping
;
1797 union swap_header
*swap_header
;
1798 unsigned int nr_good_pages
;
1801 unsigned long maxpages
;
1802 unsigned long swapfilepages
;
1803 unsigned char *swap_map
= NULL
;
1804 struct page
*page
= NULL
;
1805 struct inode
*inode
= NULL
;
1808 if (!capable(CAP_SYS_ADMIN
))
1811 p
= kzalloc(sizeof(*p
), GFP_KERNEL
);
1815 spin_lock(&swap_lock
);
1816 for (type
= 0; type
< nr_swapfiles
; type
++) {
1817 if (!(swap_info
[type
]->flags
& SWP_USED
))
1821 if (type
>= MAX_SWAPFILES
) {
1822 spin_unlock(&swap_lock
);
1826 if (type
>= nr_swapfiles
) {
1828 swap_info
[type
] = p
;
1830 * Write swap_info[type] before nr_swapfiles, in case a
1831 * racing procfs swap_start() or swap_next() is reading them.
1832 * (We never shrink nr_swapfiles, we never free this entry.)
1838 p
= swap_info
[type
];
1840 * Do not memset this entry: a racing procfs swap_next()
1841 * would be relying on p->type to remain valid.
1844 INIT_LIST_HEAD(&p
->first_swap_extent
.list
);
1845 p
->flags
= SWP_USED
;
1847 spin_unlock(&swap_lock
);
1849 name
= getname(specialfile
);
1850 error
= PTR_ERR(name
);
1855 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1856 error
= PTR_ERR(swap_file
);
1857 if (IS_ERR(swap_file
)) {
1862 p
->swap_file
= swap_file
;
1863 mapping
= swap_file
->f_mapping
;
1864 inode
= mapping
->host
;
1867 for (i
= 0; i
< nr_swapfiles
; i
++) {
1868 struct swap_info_struct
*q
= swap_info
[i
];
1870 if (i
== type
|| !q
->swap_file
)
1872 if (mapping
== q
->swap_file
->f_mapping
)
1877 if (S_ISBLK(inode
->i_mode
)) {
1878 bdev
= I_BDEV(inode
);
1879 error
= bd_claim(bdev
, sys_swapon
);
1885 p
->old_block_size
= block_size(bdev
);
1886 error
= set_blocksize(bdev
, PAGE_SIZE
);
1890 } else if (S_ISREG(inode
->i_mode
)) {
1891 p
->bdev
= inode
->i_sb
->s_bdev
;
1892 mutex_lock(&inode
->i_mutex
);
1894 if (IS_SWAPFILE(inode
)) {
1902 swapfilepages
= i_size_read(inode
) >> PAGE_SHIFT
;
1905 * Read the swap header.
1907 if (!mapping
->a_ops
->readpage
) {
1911 page
= read_mapping_page(mapping
, 0, swap_file
);
1913 error
= PTR_ERR(page
);
1916 swap_header
= kmap(page
);
1918 if (memcmp("SWAPSPACE2", swap_header
->magic
.magic
, 10)) {
1919 printk(KERN_ERR
"Unable to find swap-space signature\n");
1924 /* swap partition endianess hack... */
1925 if (swab32(swap_header
->info
.version
) == 1) {
1926 swab32s(&swap_header
->info
.version
);
1927 swab32s(&swap_header
->info
.last_page
);
1928 swab32s(&swap_header
->info
.nr_badpages
);
1929 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++)
1930 swab32s(&swap_header
->info
.badpages
[i
]);
1932 /* Check the swap header's sub-version */
1933 if (swap_header
->info
.version
!= 1) {
1935 "Unable to handle swap header version %d\n",
1936 swap_header
->info
.version
);
1942 p
->cluster_next
= 1;
1946 * Find out how many pages are allowed for a single swap
1947 * device. There are two limiting factors: 1) the number of
1948 * bits for the swap offset in the swp_entry_t type and
1949 * 2) the number of bits in the a swap pte as defined by
1950 * the different architectures. In order to find the
1951 * largest possible bit mask a swap entry with swap type 0
1952 * and swap offset ~0UL is created, encoded to a swap pte,
1953 * decoded to a swp_entry_t again and finally the swap
1954 * offset is extracted. This will mask all the bits from
1955 * the initial ~0UL mask that can't be encoded in either
1956 * the swp_entry_t or the architecture definition of a
1959 maxpages
= swp_offset(pte_to_swp_entry(
1960 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
1961 if (maxpages
> swap_header
->info
.last_page
) {
1962 maxpages
= swap_header
->info
.last_page
+ 1;
1963 /* p->max is an unsigned int: don't overflow it */
1964 if ((unsigned int)maxpages
== 0)
1965 maxpages
= UINT_MAX
;
1967 p
->highest_bit
= maxpages
- 1;
1972 if (swapfilepages
&& maxpages
> swapfilepages
) {
1974 "Swap area shorter than signature indicates\n");
1977 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1979 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1982 /* OK, set up the swap map and apply the bad block list */
1983 swap_map
= vmalloc(maxpages
);
1989 memset(swap_map
, 0, maxpages
);
1990 nr_good_pages
= maxpages
- 1; /* omit header page */
1992 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
1993 unsigned int page_nr
= swap_header
->info
.badpages
[i
];
1994 if (page_nr
== 0 || page_nr
> swap_header
->info
.last_page
) {
1998 if (page_nr
< maxpages
) {
1999 swap_map
[page_nr
] = SWAP_MAP_BAD
;
2004 error
= swap_cgroup_swapon(type
, maxpages
);
2008 if (nr_good_pages
) {
2009 swap_map
[0] = SWAP_MAP_BAD
;
2011 p
->pages
= nr_good_pages
;
2012 nr_extents
= setup_swap_extents(p
, &span
);
2013 if (nr_extents
< 0) {
2017 nr_good_pages
= p
->pages
;
2019 if (!nr_good_pages
) {
2020 printk(KERN_WARNING
"Empty swap-file\n");
2026 if (blk_queue_nonrot(bdev_get_queue(p
->bdev
))) {
2027 p
->flags
|= SWP_SOLIDSTATE
;
2028 p
->cluster_next
= 1 + (random32() % p
->highest_bit
);
2030 if (discard_swap(p
) == 0)
2031 p
->flags
|= SWP_DISCARDABLE
;
2034 mutex_lock(&swapon_mutex
);
2035 spin_lock(&swap_lock
);
2036 if (swap_flags
& SWAP_FLAG_PREFER
)
2038 (swap_flags
& SWAP_FLAG_PRIO_MASK
) >> SWAP_FLAG_PRIO_SHIFT
;
2040 p
->prio
= --least_priority
;
2041 p
->swap_map
= swap_map
;
2042 p
->flags
|= SWP_WRITEOK
;
2043 nr_swap_pages
+= nr_good_pages
;
2044 total_swap_pages
+= nr_good_pages
;
2046 printk(KERN_INFO
"Adding %uk swap on %s. "
2047 "Priority:%d extents:%d across:%lluk %s%s\n",
2048 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
2049 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10),
2050 (p
->flags
& SWP_SOLIDSTATE
) ? "SS" : "",
2051 (p
->flags
& SWP_DISCARDABLE
) ? "D" : "");
2053 /* insert swap space into swap_list: */
2055 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
]->next
) {
2056 if (p
->prio
>= swap_info
[i
]->prio
)
2062 swap_list
.head
= swap_list
.next
= type
;
2064 swap_info
[prev
]->next
= type
;
2065 spin_unlock(&swap_lock
);
2066 mutex_unlock(&swapon_mutex
);
2071 set_blocksize(bdev
, p
->old_block_size
);
2074 destroy_swap_extents(p
);
2075 swap_cgroup_swapoff(type
);
2077 spin_lock(&swap_lock
);
2078 p
->swap_file
= NULL
;
2080 spin_unlock(&swap_lock
);
2083 filp_close(swap_file
, NULL
);
2085 if (page
&& !IS_ERR(page
)) {
2087 page_cache_release(page
);
2093 inode
->i_flags
|= S_SWAPFILE
;
2094 mutex_unlock(&inode
->i_mutex
);
2099 void si_swapinfo(struct sysinfo
*val
)
2102 unsigned long nr_to_be_unused
= 0;
2104 spin_lock(&swap_lock
);
2105 for (type
= 0; type
< nr_swapfiles
; type
++) {
2106 struct swap_info_struct
*si
= swap_info
[type
];
2108 if ((si
->flags
& SWP_USED
) && !(si
->flags
& SWP_WRITEOK
))
2109 nr_to_be_unused
+= si
->inuse_pages
;
2111 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
2112 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
2113 spin_unlock(&swap_lock
);
2117 * Verify that a swap entry is valid and increment its swap map count.
2119 * Returns error code in following case.
2121 * - swp_entry is invalid -> EINVAL
2122 * - swp_entry is migration entry -> EINVAL
2123 * - swap-cache reference is requested but there is already one. -> EEXIST
2124 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2125 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2127 static int __swap_duplicate(swp_entry_t entry
, unsigned char usage
)
2129 struct swap_info_struct
*p
;
2130 unsigned long offset
, type
;
2131 unsigned char count
;
2132 unsigned char has_cache
;
2135 if (non_swap_entry(entry
))
2138 type
= swp_type(entry
);
2139 if (type
>= nr_swapfiles
)
2141 p
= swap_info
[type
];
2142 offset
= swp_offset(entry
);
2144 spin_lock(&swap_lock
);
2145 if (unlikely(offset
>= p
->max
))
2148 count
= p
->swap_map
[offset
];
2149 has_cache
= count
& SWAP_HAS_CACHE
;
2150 count
&= ~SWAP_HAS_CACHE
;
2153 if (usage
== SWAP_HAS_CACHE
) {
2155 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2156 if (!has_cache
&& count
)
2157 has_cache
= SWAP_HAS_CACHE
;
2158 else if (has_cache
) /* someone else added cache */
2160 else /* no users remaining */
2163 } else if (count
|| has_cache
) {
2165 if ((count
& ~COUNT_CONTINUED
) < SWAP_MAP_MAX
)
2167 else if ((count
& ~COUNT_CONTINUED
) > SWAP_MAP_MAX
)
2169 else if (swap_count_continued(p
, offset
, count
))
2170 count
= COUNT_CONTINUED
;
2174 err
= -ENOENT
; /* unused swap entry */
2176 p
->swap_map
[offset
] = count
| has_cache
;
2179 spin_unlock(&swap_lock
);
2184 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
2189 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2190 * (in which case its reference count is never incremented).
2192 void swap_shmem_alloc(swp_entry_t entry
)
2194 __swap_duplicate(entry
, SWAP_MAP_SHMEM
);
2198 * Increase reference count of swap entry by 1.
2199 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2200 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2201 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2202 * might occur if a page table entry has got corrupted.
2204 int swap_duplicate(swp_entry_t entry
)
2208 while (!err
&& __swap_duplicate(entry
, 1) == -ENOMEM
)
2209 err
= add_swap_count_continuation(entry
, GFP_ATOMIC
);
2214 * @entry: swap entry for which we allocate swap cache.
2216 * Called when allocating swap cache for existing swap entry,
2217 * This can return error codes. Returns 0 at success.
2218 * -EBUSY means there is a swap cache.
2219 * Note: return code is different from swap_duplicate().
2221 int swapcache_prepare(swp_entry_t entry
)
2223 return __swap_duplicate(entry
, SWAP_HAS_CACHE
);
2227 * swap_lock prevents swap_map being freed. Don't grab an extra
2228 * reference on the swaphandle, it doesn't matter if it becomes unused.
2230 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
2232 struct swap_info_struct
*si
;
2233 int our_page_cluster
= page_cluster
;
2234 pgoff_t target
, toff
;
2238 if (!our_page_cluster
) /* no readahead */
2241 si
= swap_info
[swp_type(entry
)];
2242 target
= swp_offset(entry
);
2243 base
= (target
>> our_page_cluster
) << our_page_cluster
;
2244 end
= base
+ (1 << our_page_cluster
);
2245 if (!base
) /* first page is swap header */
2248 spin_lock(&swap_lock
);
2249 if (end
> si
->max
) /* don't go beyond end of map */
2252 /* Count contiguous allocated slots above our target */
2253 for (toff
= target
; ++toff
< end
; nr_pages
++) {
2254 /* Don't read in free or bad pages */
2255 if (!si
->swap_map
[toff
])
2257 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2260 /* Count contiguous allocated slots below our target */
2261 for (toff
= target
; --toff
>= base
; nr_pages
++) {
2262 /* Don't read in free or bad pages */
2263 if (!si
->swap_map
[toff
])
2265 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2268 spin_unlock(&swap_lock
);
2271 * Indicate starting offset, and return number of pages to get:
2272 * if only 1, say 0, since there's then no readahead to be done.
2275 return nr_pages
? ++nr_pages
: 0;
2279 * add_swap_count_continuation - called when a swap count is duplicated
2280 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2281 * page of the original vmalloc'ed swap_map, to hold the continuation count
2282 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2283 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2285 * These continuation pages are seldom referenced: the common paths all work
2286 * on the original swap_map, only referring to a continuation page when the
2287 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2289 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2290 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2291 * can be called after dropping locks.
2293 int add_swap_count_continuation(swp_entry_t entry
, gfp_t gfp_mask
)
2295 struct swap_info_struct
*si
;
2298 struct page
*list_page
;
2300 unsigned char count
;
2303 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2304 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2306 page
= alloc_page(gfp_mask
| __GFP_HIGHMEM
);
2308 si
= swap_info_get(entry
);
2311 * An acceptable race has occurred since the failing
2312 * __swap_duplicate(): the swap entry has been freed,
2313 * perhaps even the whole swap_map cleared for swapoff.
2318 offset
= swp_offset(entry
);
2319 count
= si
->swap_map
[offset
] & ~SWAP_HAS_CACHE
;
2321 if ((count
& ~COUNT_CONTINUED
) != SWAP_MAP_MAX
) {
2323 * The higher the swap count, the more likely it is that tasks
2324 * will race to add swap count continuation: we need to avoid
2325 * over-provisioning.
2331 spin_unlock(&swap_lock
);
2336 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2337 * no architecture is using highmem pages for kernel pagetables: so it
2338 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2340 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2341 offset
&= ~PAGE_MASK
;
2344 * Page allocation does not initialize the page's lru field,
2345 * but it does always reset its private field.
2347 if (!page_private(head
)) {
2348 BUG_ON(count
& COUNT_CONTINUED
);
2349 INIT_LIST_HEAD(&head
->lru
);
2350 set_page_private(head
, SWP_CONTINUED
);
2351 si
->flags
|= SWP_CONTINUED
;
2354 list_for_each_entry(list_page
, &head
->lru
, lru
) {
2358 * If the previous map said no continuation, but we've found
2359 * a continuation page, free our allocation and use this one.
2361 if (!(count
& COUNT_CONTINUED
))
2364 map
= kmap_atomic(list_page
, KM_USER0
) + offset
;
2366 kunmap_atomic(map
, KM_USER0
);
2369 * If this continuation count now has some space in it,
2370 * free our allocation and use this one.
2372 if ((count
& ~COUNT_CONTINUED
) != SWAP_CONT_MAX
)
2376 list_add_tail(&page
->lru
, &head
->lru
);
2377 page
= NULL
; /* now it's attached, don't free it */
2379 spin_unlock(&swap_lock
);
2387 * swap_count_continued - when the original swap_map count is incremented
2388 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2389 * into, carry if so, or else fail until a new continuation page is allocated;
2390 * when the original swap_map count is decremented from 0 with continuation,
2391 * borrow from the continuation and report whether it still holds more.
2392 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2394 static bool swap_count_continued(struct swap_info_struct
*si
,
2395 pgoff_t offset
, unsigned char count
)
2401 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2402 if (page_private(head
) != SWP_CONTINUED
) {
2403 BUG_ON(count
& COUNT_CONTINUED
);
2404 return false; /* need to add count continuation */
2407 offset
&= ~PAGE_MASK
;
2408 page
= list_entry(head
->lru
.next
, struct page
, lru
);
2409 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2411 if (count
== SWAP_MAP_MAX
) /* initial increment from swap_map */
2412 goto init_map
; /* jump over SWAP_CONT_MAX checks */
2414 if (count
== (SWAP_MAP_MAX
| COUNT_CONTINUED
)) { /* incrementing */
2416 * Think of how you add 1 to 999
2418 while (*map
== (SWAP_CONT_MAX
| COUNT_CONTINUED
)) {
2419 kunmap_atomic(map
, KM_USER0
);
2420 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2421 BUG_ON(page
== head
);
2422 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2424 if (*map
== SWAP_CONT_MAX
) {
2425 kunmap_atomic(map
, KM_USER0
);
2426 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2428 return false; /* add count continuation */
2429 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2430 init_map
: *map
= 0; /* we didn't zero the page */
2433 kunmap_atomic(map
, KM_USER0
);
2434 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2435 while (page
!= head
) {
2436 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2437 *map
= COUNT_CONTINUED
;
2438 kunmap_atomic(map
, KM_USER0
);
2439 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2441 return true; /* incremented */
2443 } else { /* decrementing */
2445 * Think of how you subtract 1 from 1000
2447 BUG_ON(count
!= COUNT_CONTINUED
);
2448 while (*map
== COUNT_CONTINUED
) {
2449 kunmap_atomic(map
, KM_USER0
);
2450 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2451 BUG_ON(page
== head
);
2452 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2458 kunmap_atomic(map
, KM_USER0
);
2459 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2460 while (page
!= head
) {
2461 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2462 *map
= SWAP_CONT_MAX
| count
;
2463 count
= COUNT_CONTINUED
;
2464 kunmap_atomic(map
, KM_USER0
);
2465 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2467 return count
== COUNT_CONTINUED
;
2472 * free_swap_count_continuations - swapoff free all the continuation pages
2473 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2475 static void free_swap_count_continuations(struct swap_info_struct
*si
)
2479 for (offset
= 0; offset
< si
->max
; offset
+= PAGE_SIZE
) {
2481 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2482 if (page_private(head
)) {
2483 struct list_head
*this, *next
;
2484 list_for_each_safe(this, next
, &head
->lru
) {
2486 page
= list_entry(this, struct page
, lru
);