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
, DISCARD_FL_BARRIER
);
148 list_for_each_entry(se
, &si
->first_swap_extent
.list
, list
) {
149 start_block
= se
->start_block
<< (PAGE_SHIFT
- 9);
150 nr_blocks
= (sector_t
)se
->nr_pages
<< (PAGE_SHIFT
- 9);
152 err
= blkdev_issue_discard(si
->bdev
, start_block
,
153 nr_blocks
, GFP_KERNEL
, DISCARD_FL_BARRIER
);
159 return err
; /* That will often be -EOPNOTSUPP */
163 * swap allocation tell device that a cluster of swap can now be discarded,
164 * to allow the swap device to optimize its wear-levelling.
166 static void discard_swap_cluster(struct swap_info_struct
*si
,
167 pgoff_t start_page
, pgoff_t nr_pages
)
169 struct swap_extent
*se
= si
->curr_swap_extent
;
170 int found_extent
= 0;
173 struct list_head
*lh
;
175 if (se
->start_page
<= start_page
&&
176 start_page
< se
->start_page
+ se
->nr_pages
) {
177 pgoff_t offset
= start_page
- se
->start_page
;
178 sector_t start_block
= se
->start_block
+ offset
;
179 sector_t nr_blocks
= se
->nr_pages
- offset
;
181 if (nr_blocks
> nr_pages
)
182 nr_blocks
= nr_pages
;
183 start_page
+= nr_blocks
;
184 nr_pages
-= nr_blocks
;
187 si
->curr_swap_extent
= se
;
189 start_block
<<= PAGE_SHIFT
- 9;
190 nr_blocks
<<= PAGE_SHIFT
- 9;
191 if (blkdev_issue_discard(si
->bdev
, start_block
,
192 nr_blocks
, GFP_NOIO
, DISCARD_FL_BARRIER
))
197 se
= list_entry(lh
, struct swap_extent
, list
);
201 static int wait_for_discard(void *word
)
207 #define SWAPFILE_CLUSTER 256
208 #define LATENCY_LIMIT 256
210 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
,
213 unsigned long offset
;
214 unsigned long scan_base
;
215 unsigned long last_in_cluster
= 0;
216 int latency_ration
= LATENCY_LIMIT
;
217 int found_free_cluster
= 0;
220 * We try to cluster swap pages by allocating them sequentially
221 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
222 * way, however, we resort to first-free allocation, starting
223 * a new cluster. This prevents us from scattering swap pages
224 * all over the entire swap partition, so that we reduce
225 * overall disk seek times between swap pages. -- sct
226 * But we do now try to find an empty cluster. -Andrea
227 * And we let swap pages go all over an SSD partition. Hugh
230 si
->flags
+= SWP_SCANNING
;
231 scan_base
= offset
= si
->cluster_next
;
233 if (unlikely(!si
->cluster_nr
--)) {
234 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
) {
235 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
238 if (si
->flags
& SWP_DISCARDABLE
) {
240 * Start range check on racing allocations, in case
241 * they overlap the cluster we eventually decide on
242 * (we scan without swap_lock to allow preemption).
243 * It's hardly conceivable that cluster_nr could be
244 * wrapped during our scan, but don't depend on it.
246 if (si
->lowest_alloc
)
248 si
->lowest_alloc
= si
->max
;
249 si
->highest_alloc
= 0;
251 spin_unlock(&swap_lock
);
254 * If seek is expensive, start searching for new cluster from
255 * start of partition, to minimize the span of allocated swap.
256 * But if seek is cheap, search from our current position, so
257 * that swap is allocated from all over the partition: if the
258 * Flash Translation Layer only remaps within limited zones,
259 * we don't want to wear out the first zone too quickly.
261 if (!(si
->flags
& SWP_SOLIDSTATE
))
262 scan_base
= offset
= si
->lowest_bit
;
263 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
265 /* Locate the first empty (unaligned) cluster */
266 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
267 if (si
->swap_map
[offset
])
268 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
269 else if (offset
== last_in_cluster
) {
270 spin_lock(&swap_lock
);
271 offset
-= SWAPFILE_CLUSTER
- 1;
272 si
->cluster_next
= offset
;
273 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
274 found_free_cluster
= 1;
277 if (unlikely(--latency_ration
< 0)) {
279 latency_ration
= LATENCY_LIMIT
;
283 offset
= si
->lowest_bit
;
284 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
286 /* Locate the first empty (unaligned) cluster */
287 for (; last_in_cluster
< scan_base
; offset
++) {
288 if (si
->swap_map
[offset
])
289 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
290 else if (offset
== last_in_cluster
) {
291 spin_lock(&swap_lock
);
292 offset
-= SWAPFILE_CLUSTER
- 1;
293 si
->cluster_next
= offset
;
294 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
295 found_free_cluster
= 1;
298 if (unlikely(--latency_ration
< 0)) {
300 latency_ration
= LATENCY_LIMIT
;
305 spin_lock(&swap_lock
);
306 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
307 si
->lowest_alloc
= 0;
311 if (!(si
->flags
& SWP_WRITEOK
))
313 if (!si
->highest_bit
)
315 if (offset
> si
->highest_bit
)
316 scan_base
= offset
= si
->lowest_bit
;
318 /* reuse swap entry of cache-only swap if not busy. */
319 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
321 spin_unlock(&swap_lock
);
322 swap_was_freed
= __try_to_reclaim_swap(si
, offset
);
323 spin_lock(&swap_lock
);
324 /* entry was freed successfully, try to use this again */
327 goto scan
; /* check next one */
330 if (si
->swap_map
[offset
])
333 if (offset
== si
->lowest_bit
)
335 if (offset
== si
->highest_bit
)
338 if (si
->inuse_pages
== si
->pages
) {
339 si
->lowest_bit
= si
->max
;
342 si
->swap_map
[offset
] = usage
;
343 si
->cluster_next
= offset
+ 1;
344 si
->flags
-= SWP_SCANNING
;
346 if (si
->lowest_alloc
) {
348 * Only set when SWP_DISCARDABLE, and there's a scan
349 * for a free cluster in progress or just completed.
351 if (found_free_cluster
) {
353 * To optimize wear-levelling, discard the
354 * old data of the cluster, taking care not to
355 * discard any of its pages that have already
356 * been allocated by racing tasks (offset has
357 * already stepped over any at the beginning).
359 if (offset
< si
->highest_alloc
&&
360 si
->lowest_alloc
<= last_in_cluster
)
361 last_in_cluster
= si
->lowest_alloc
- 1;
362 si
->flags
|= SWP_DISCARDING
;
363 spin_unlock(&swap_lock
);
365 if (offset
< last_in_cluster
)
366 discard_swap_cluster(si
, offset
,
367 last_in_cluster
- offset
+ 1);
369 spin_lock(&swap_lock
);
370 si
->lowest_alloc
= 0;
371 si
->flags
&= ~SWP_DISCARDING
;
373 smp_mb(); /* wake_up_bit advises this */
374 wake_up_bit(&si
->flags
, ilog2(SWP_DISCARDING
));
376 } else if (si
->flags
& SWP_DISCARDING
) {
378 * Delay using pages allocated by racing tasks
379 * until the whole discard has been issued. We
380 * could defer that delay until swap_writepage,
381 * but it's easier to keep this self-contained.
383 spin_unlock(&swap_lock
);
384 wait_on_bit(&si
->flags
, ilog2(SWP_DISCARDING
),
385 wait_for_discard
, TASK_UNINTERRUPTIBLE
);
386 spin_lock(&swap_lock
);
389 * Note pages allocated by racing tasks while
390 * scan for a free cluster is in progress, so
391 * that its final discard can exclude them.
393 if (offset
< si
->lowest_alloc
)
394 si
->lowest_alloc
= offset
;
395 if (offset
> si
->highest_alloc
)
396 si
->highest_alloc
= offset
;
402 spin_unlock(&swap_lock
);
403 while (++offset
<= si
->highest_bit
) {
404 if (!si
->swap_map
[offset
]) {
405 spin_lock(&swap_lock
);
408 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
409 spin_lock(&swap_lock
);
412 if (unlikely(--latency_ration
< 0)) {
414 latency_ration
= LATENCY_LIMIT
;
417 offset
= si
->lowest_bit
;
418 while (++offset
< scan_base
) {
419 if (!si
->swap_map
[offset
]) {
420 spin_lock(&swap_lock
);
423 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
424 spin_lock(&swap_lock
);
427 if (unlikely(--latency_ration
< 0)) {
429 latency_ration
= LATENCY_LIMIT
;
432 spin_lock(&swap_lock
);
435 si
->flags
-= SWP_SCANNING
;
439 swp_entry_t
get_swap_page(void)
441 struct swap_info_struct
*si
;
446 spin_lock(&swap_lock
);
447 if (nr_swap_pages
<= 0)
451 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
452 si
= swap_info
[type
];
455 (!wrapped
&& si
->prio
!= swap_info
[next
]->prio
)) {
456 next
= swap_list
.head
;
460 if (!si
->highest_bit
)
462 if (!(si
->flags
& SWP_WRITEOK
))
465 swap_list
.next
= next
;
466 /* This is called for allocating swap entry for cache */
467 offset
= scan_swap_map(si
, SWAP_HAS_CACHE
);
469 spin_unlock(&swap_lock
);
470 return swp_entry(type
, offset
);
472 next
= swap_list
.next
;
477 spin_unlock(&swap_lock
);
478 return (swp_entry_t
) {0};
481 /* The only caller of this function is now susupend routine */
482 swp_entry_t
get_swap_page_of_type(int type
)
484 struct swap_info_struct
*si
;
487 spin_lock(&swap_lock
);
488 si
= swap_info
[type
];
489 if (si
&& (si
->flags
& SWP_WRITEOK
)) {
491 /* This is called for allocating swap entry, not cache */
492 offset
= scan_swap_map(si
, 1);
494 spin_unlock(&swap_lock
);
495 return swp_entry(type
, offset
);
499 spin_unlock(&swap_lock
);
500 return (swp_entry_t
) {0};
503 static struct swap_info_struct
*swap_info_get(swp_entry_t entry
)
505 struct swap_info_struct
*p
;
506 unsigned long offset
, type
;
510 type
= swp_type(entry
);
511 if (type
>= nr_swapfiles
)
514 if (!(p
->flags
& SWP_USED
))
516 offset
= swp_offset(entry
);
517 if (offset
>= p
->max
)
519 if (!p
->swap_map
[offset
])
521 spin_lock(&swap_lock
);
525 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
528 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
531 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
534 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
539 static unsigned char swap_entry_free(struct swap_info_struct
*p
,
540 swp_entry_t entry
, unsigned char usage
)
542 unsigned long offset
= swp_offset(entry
);
544 unsigned char has_cache
;
546 count
= p
->swap_map
[offset
];
547 has_cache
= count
& SWAP_HAS_CACHE
;
548 count
&= ~SWAP_HAS_CACHE
;
550 if (usage
== SWAP_HAS_CACHE
) {
551 VM_BUG_ON(!has_cache
);
553 } else if (count
== SWAP_MAP_SHMEM
) {
555 * Or we could insist on shmem.c using a special
556 * swap_shmem_free() and free_shmem_swap_and_cache()...
559 } else if ((count
& ~COUNT_CONTINUED
) <= SWAP_MAP_MAX
) {
560 if (count
== COUNT_CONTINUED
) {
561 if (swap_count_continued(p
, offset
, count
))
562 count
= SWAP_MAP_MAX
| COUNT_CONTINUED
;
564 count
= SWAP_MAP_MAX
;
570 mem_cgroup_uncharge_swap(entry
);
572 usage
= count
| has_cache
;
573 p
->swap_map
[offset
] = usage
;
575 /* free if no reference */
577 struct gendisk
*disk
= p
->bdev
->bd_disk
;
578 if (offset
< p
->lowest_bit
)
579 p
->lowest_bit
= offset
;
580 if (offset
> p
->highest_bit
)
581 p
->highest_bit
= offset
;
582 if (swap_list
.next
>= 0 &&
583 p
->prio
> swap_info
[swap_list
.next
]->prio
)
584 swap_list
.next
= p
->type
;
587 if ((p
->flags
& SWP_BLKDEV
) &&
588 disk
->fops
->swap_slot_free_notify
)
589 disk
->fops
->swap_slot_free_notify(p
->bdev
, offset
);
596 * Caller has made sure that the swapdevice corresponding to entry
597 * is still around or has not been recycled.
599 void swap_free(swp_entry_t entry
)
601 struct swap_info_struct
*p
;
603 p
= swap_info_get(entry
);
605 swap_entry_free(p
, entry
, 1);
606 spin_unlock(&swap_lock
);
611 * Called after dropping swapcache to decrease refcnt to swap entries.
613 void swapcache_free(swp_entry_t entry
, struct page
*page
)
615 struct swap_info_struct
*p
;
618 p
= swap_info_get(entry
);
620 count
= swap_entry_free(p
, entry
, SWAP_HAS_CACHE
);
622 mem_cgroup_uncharge_swapcache(page
, entry
, count
!= 0);
623 spin_unlock(&swap_lock
);
628 * How many references to page are currently swapped out?
629 * This does not give an exact answer when swap count is continued,
630 * but does include the high COUNT_CONTINUED flag to allow for that.
632 static inline int page_swapcount(struct page
*page
)
635 struct swap_info_struct
*p
;
638 entry
.val
= page_private(page
);
639 p
= swap_info_get(entry
);
641 count
= swap_count(p
->swap_map
[swp_offset(entry
)]);
642 spin_unlock(&swap_lock
);
648 * We can write to an anon page without COW if there are no other references
649 * to it. And as a side-effect, free up its swap: because the old content
650 * on disk will never be read, and seeking back there to write new content
651 * later would only waste time away from clustering.
653 int reuse_swap_page(struct page
*page
)
657 VM_BUG_ON(!PageLocked(page
));
658 if (unlikely(PageKsm(page
)))
660 count
= page_mapcount(page
);
661 if (count
<= 1 && PageSwapCache(page
)) {
662 count
+= page_swapcount(page
);
663 if (count
== 1 && !PageWriteback(page
)) {
664 delete_from_swap_cache(page
);
672 * If swap is getting full, or if there are no more mappings of this page,
673 * then try_to_free_swap is called to free its swap space.
675 int try_to_free_swap(struct page
*page
)
677 VM_BUG_ON(!PageLocked(page
));
679 if (!PageSwapCache(page
))
681 if (PageWriteback(page
))
683 if (page_swapcount(page
))
686 delete_from_swap_cache(page
);
692 * Free the swap entry like above, but also try to
693 * free the page cache entry if it is the last user.
695 int free_swap_and_cache(swp_entry_t entry
)
697 struct swap_info_struct
*p
;
698 struct page
*page
= NULL
;
700 if (non_swap_entry(entry
))
703 p
= swap_info_get(entry
);
705 if (swap_entry_free(p
, entry
, 1) == SWAP_HAS_CACHE
) {
706 page
= find_get_page(&swapper_space
, entry
.val
);
707 if (page
&& !trylock_page(page
)) {
708 page_cache_release(page
);
712 spin_unlock(&swap_lock
);
716 * Not mapped elsewhere, or swap space full? Free it!
717 * Also recheck PageSwapCache now page is locked (above).
719 if (PageSwapCache(page
) && !PageWriteback(page
) &&
720 (!page_mapped(page
) || vm_swap_full())) {
721 delete_from_swap_cache(page
);
725 page_cache_release(page
);
730 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
732 * mem_cgroup_count_swap_user - count the user of a swap entry
733 * @ent: the swap entry to be checked
734 * @pagep: the pointer for the swap cache page of the entry to be stored
736 * Returns the number of the user of the swap entry. The number is valid only
737 * for swaps of anonymous pages.
738 * If the entry is found on swap cache, the page is stored to pagep with
739 * refcount of it being incremented.
741 int mem_cgroup_count_swap_user(swp_entry_t ent
, struct page
**pagep
)
744 struct swap_info_struct
*p
;
747 page
= find_get_page(&swapper_space
, ent
.val
);
749 count
+= page_mapcount(page
);
750 p
= swap_info_get(ent
);
752 count
+= swap_count(p
->swap_map
[swp_offset(ent
)]);
753 spin_unlock(&swap_lock
);
761 #ifdef CONFIG_HIBERNATION
763 * Find the swap type that corresponds to given device (if any).
765 * @offset - number of the PAGE_SIZE-sized block of the device, starting
766 * from 0, in which the swap header is expected to be located.
768 * This is needed for the suspend to disk (aka swsusp).
770 int swap_type_of(dev_t device
, sector_t offset
, struct block_device
**bdev_p
)
772 struct block_device
*bdev
= NULL
;
776 bdev
= bdget(device
);
778 spin_lock(&swap_lock
);
779 for (type
= 0; type
< nr_swapfiles
; type
++) {
780 struct swap_info_struct
*sis
= swap_info
[type
];
782 if (!(sis
->flags
& SWP_WRITEOK
))
787 *bdev_p
= bdgrab(sis
->bdev
);
789 spin_unlock(&swap_lock
);
792 if (bdev
== sis
->bdev
) {
793 struct swap_extent
*se
= &sis
->first_swap_extent
;
795 if (se
->start_block
== offset
) {
797 *bdev_p
= bdgrab(sis
->bdev
);
799 spin_unlock(&swap_lock
);
805 spin_unlock(&swap_lock
);
813 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
814 * corresponding to given index in swap_info (swap type).
816 sector_t
swapdev_block(int type
, pgoff_t offset
)
818 struct block_device
*bdev
;
820 if ((unsigned int)type
>= nr_swapfiles
)
822 if (!(swap_info
[type
]->flags
& SWP_WRITEOK
))
824 return map_swap_entry(swp_entry(type
, offset
), &bdev
);
828 * Return either the total number of swap pages of given type, or the number
829 * of free pages of that type (depending on @free)
831 * This is needed for software suspend
833 unsigned int count_swap_pages(int type
, int free
)
837 spin_lock(&swap_lock
);
838 if ((unsigned int)type
< nr_swapfiles
) {
839 struct swap_info_struct
*sis
= swap_info
[type
];
841 if (sis
->flags
& SWP_WRITEOK
) {
844 n
-= sis
->inuse_pages
;
847 spin_unlock(&swap_lock
);
850 #endif /* CONFIG_HIBERNATION */
853 * No need to decide whether this PTE shares the swap entry with others,
854 * just let do_wp_page work it out if a write is requested later - to
855 * force COW, vm_page_prot omits write permission from any private vma.
857 static int unuse_pte(struct vm_area_struct
*vma
, pmd_t
*pmd
,
858 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
860 struct mem_cgroup
*ptr
= NULL
;
865 if (mem_cgroup_try_charge_swapin(vma
->vm_mm
, page
, GFP_KERNEL
, &ptr
)) {
870 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
871 if (unlikely(!pte_same(*pte
, swp_entry_to_pte(entry
)))) {
873 mem_cgroup_cancel_charge_swapin(ptr
);
878 dec_mm_counter(vma
->vm_mm
, MM_SWAPENTS
);
879 inc_mm_counter(vma
->vm_mm
, MM_ANONPAGES
);
881 set_pte_at(vma
->vm_mm
, addr
, pte
,
882 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
883 page_add_anon_rmap(page
, vma
, addr
);
884 mem_cgroup_commit_charge_swapin(page
, ptr
);
887 * Move the page to the active list so it is not
888 * immediately swapped out again after swapon.
892 pte_unmap_unlock(pte
, ptl
);
897 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
898 unsigned long addr
, unsigned long end
,
899 swp_entry_t entry
, struct page
*page
)
901 pte_t swp_pte
= swp_entry_to_pte(entry
);
906 * We don't actually need pte lock while scanning for swp_pte: since
907 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
908 * page table while we're scanning; though it could get zapped, and on
909 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
910 * of unmatched parts which look like swp_pte, so unuse_pte must
911 * recheck under pte lock. Scanning without pte lock lets it be
912 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
914 pte
= pte_offset_map(pmd
, addr
);
917 * swapoff spends a _lot_ of time in this loop!
918 * Test inline before going to call unuse_pte.
920 if (unlikely(pte_same(*pte
, swp_pte
))) {
922 ret
= unuse_pte(vma
, pmd
, addr
, entry
, page
);
925 pte
= pte_offset_map(pmd
, addr
);
927 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
933 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
934 unsigned long addr
, unsigned long end
,
935 swp_entry_t entry
, struct page
*page
)
941 pmd
= pmd_offset(pud
, addr
);
943 next
= pmd_addr_end(addr
, end
);
944 if (pmd_none_or_clear_bad(pmd
))
946 ret
= unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
);
949 } while (pmd
++, addr
= next
, addr
!= end
);
953 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
954 unsigned long addr
, unsigned long end
,
955 swp_entry_t entry
, struct page
*page
)
961 pud
= pud_offset(pgd
, addr
);
963 next
= pud_addr_end(addr
, end
);
964 if (pud_none_or_clear_bad(pud
))
966 ret
= unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
);
969 } while (pud
++, addr
= next
, addr
!= end
);
973 static int unuse_vma(struct vm_area_struct
*vma
,
974 swp_entry_t entry
, struct page
*page
)
977 unsigned long addr
, end
, next
;
980 if (page_anon_vma(page
)) {
981 addr
= page_address_in_vma(page
, vma
);
985 end
= addr
+ PAGE_SIZE
;
987 addr
= vma
->vm_start
;
991 pgd
= pgd_offset(vma
->vm_mm
, addr
);
993 next
= pgd_addr_end(addr
, end
);
994 if (pgd_none_or_clear_bad(pgd
))
996 ret
= unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
);
999 } while (pgd
++, addr
= next
, addr
!= end
);
1003 static int unuse_mm(struct mm_struct
*mm
,
1004 swp_entry_t entry
, struct page
*page
)
1006 struct vm_area_struct
*vma
;
1009 if (!down_read_trylock(&mm
->mmap_sem
)) {
1011 * Activate page so shrink_inactive_list is unlikely to unmap
1012 * its ptes while lock is dropped, so swapoff can make progress.
1014 activate_page(page
);
1016 down_read(&mm
->mmap_sem
);
1019 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
1020 if (vma
->anon_vma
&& (ret
= unuse_vma(vma
, entry
, page
)))
1023 up_read(&mm
->mmap_sem
);
1024 return (ret
< 0)? ret
: 0;
1028 * Scan swap_map from current position to next entry still in use.
1029 * Recycle to start on reaching the end, returning 0 when empty.
1031 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
1034 unsigned int max
= si
->max
;
1035 unsigned int i
= prev
;
1036 unsigned char count
;
1039 * No need for swap_lock here: we're just looking
1040 * for whether an entry is in use, not modifying it; false
1041 * hits are okay, and sys_swapoff() has already prevented new
1042 * allocations from this area (while holding swap_lock).
1051 * No entries in use at top of swap_map,
1052 * loop back to start and recheck there.
1058 count
= si
->swap_map
[i
];
1059 if (count
&& swap_count(count
) != SWAP_MAP_BAD
)
1066 * We completely avoid races by reading each swap page in advance,
1067 * and then search for the process using it. All the necessary
1068 * page table adjustments can then be made atomically.
1070 static int try_to_unuse(unsigned int type
)
1072 struct swap_info_struct
*si
= swap_info
[type
];
1073 struct mm_struct
*start_mm
;
1074 unsigned char *swap_map
;
1075 unsigned char swcount
;
1082 * When searching mms for an entry, a good strategy is to
1083 * start at the first mm we freed the previous entry from
1084 * (though actually we don't notice whether we or coincidence
1085 * freed the entry). Initialize this start_mm with a hold.
1087 * A simpler strategy would be to start at the last mm we
1088 * freed the previous entry from; but that would take less
1089 * advantage of mmlist ordering, which clusters forked mms
1090 * together, child after parent. If we race with dup_mmap(), we
1091 * prefer to resolve parent before child, lest we miss entries
1092 * duplicated after we scanned child: using last mm would invert
1095 start_mm
= &init_mm
;
1096 atomic_inc(&init_mm
.mm_users
);
1099 * Keep on scanning until all entries have gone. Usually,
1100 * one pass through swap_map is enough, but not necessarily:
1101 * there are races when an instance of an entry might be missed.
1103 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
1104 if (signal_pending(current
)) {
1110 * Get a page for the entry, using the existing swap
1111 * cache page if there is one. Otherwise, get a clean
1112 * page and read the swap into it.
1114 swap_map
= &si
->swap_map
[i
];
1115 entry
= swp_entry(type
, i
);
1116 page
= read_swap_cache_async(entry
,
1117 GFP_HIGHUSER_MOVABLE
, NULL
, 0);
1120 * Either swap_duplicate() failed because entry
1121 * has been freed independently, and will not be
1122 * reused since sys_swapoff() already disabled
1123 * allocation from here, or alloc_page() failed.
1132 * Don't hold on to start_mm if it looks like exiting.
1134 if (atomic_read(&start_mm
->mm_users
) == 1) {
1136 start_mm
= &init_mm
;
1137 atomic_inc(&init_mm
.mm_users
);
1141 * Wait for and lock page. When do_swap_page races with
1142 * try_to_unuse, do_swap_page can handle the fault much
1143 * faster than try_to_unuse can locate the entry. This
1144 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1145 * defer to do_swap_page in such a case - in some tests,
1146 * do_swap_page and try_to_unuse repeatedly compete.
1148 wait_on_page_locked(page
);
1149 wait_on_page_writeback(page
);
1151 wait_on_page_writeback(page
);
1154 * Remove all references to entry.
1156 swcount
= *swap_map
;
1157 if (swap_count(swcount
) == SWAP_MAP_SHMEM
) {
1158 retval
= shmem_unuse(entry
, page
);
1159 /* page has already been unlocked and released */
1164 if (swap_count(swcount
) && start_mm
!= &init_mm
)
1165 retval
= unuse_mm(start_mm
, entry
, page
);
1167 if (swap_count(*swap_map
)) {
1168 int set_start_mm
= (*swap_map
>= swcount
);
1169 struct list_head
*p
= &start_mm
->mmlist
;
1170 struct mm_struct
*new_start_mm
= start_mm
;
1171 struct mm_struct
*prev_mm
= start_mm
;
1172 struct mm_struct
*mm
;
1174 atomic_inc(&new_start_mm
->mm_users
);
1175 atomic_inc(&prev_mm
->mm_users
);
1176 spin_lock(&mmlist_lock
);
1177 while (swap_count(*swap_map
) && !retval
&&
1178 (p
= p
->next
) != &start_mm
->mmlist
) {
1179 mm
= list_entry(p
, struct mm_struct
, mmlist
);
1180 if (!atomic_inc_not_zero(&mm
->mm_users
))
1182 spin_unlock(&mmlist_lock
);
1188 swcount
= *swap_map
;
1189 if (!swap_count(swcount
)) /* any usage ? */
1191 else if (mm
== &init_mm
)
1194 retval
= unuse_mm(mm
, entry
, page
);
1196 if (set_start_mm
&& *swap_map
< swcount
) {
1197 mmput(new_start_mm
);
1198 atomic_inc(&mm
->mm_users
);
1202 spin_lock(&mmlist_lock
);
1204 spin_unlock(&mmlist_lock
);
1207 start_mm
= new_start_mm
;
1211 page_cache_release(page
);
1216 * If a reference remains (rare), we would like to leave
1217 * the page in the swap cache; but try_to_unmap could
1218 * then re-duplicate the entry once we drop page lock,
1219 * so we might loop indefinitely; also, that page could
1220 * not be swapped out to other storage meanwhile. So:
1221 * delete from cache even if there's another reference,
1222 * after ensuring that the data has been saved to disk -
1223 * since if the reference remains (rarer), it will be
1224 * read from disk into another page. Splitting into two
1225 * pages would be incorrect if swap supported "shared
1226 * private" pages, but they are handled by tmpfs files.
1228 * Given how unuse_vma() targets one particular offset
1229 * in an anon_vma, once the anon_vma has been determined,
1230 * this splitting happens to be just what is needed to
1231 * handle where KSM pages have been swapped out: re-reading
1232 * is unnecessarily slow, but we can fix that later on.
1234 if (swap_count(*swap_map
) &&
1235 PageDirty(page
) && PageSwapCache(page
)) {
1236 struct writeback_control wbc
= {
1237 .sync_mode
= WB_SYNC_NONE
,
1240 swap_writepage(page
, &wbc
);
1242 wait_on_page_writeback(page
);
1246 * It is conceivable that a racing task removed this page from
1247 * swap cache just before we acquired the page lock at the top,
1248 * or while we dropped it in unuse_mm(). The page might even
1249 * be back in swap cache on another swap area: that we must not
1250 * delete, since it may not have been written out to swap yet.
1252 if (PageSwapCache(page
) &&
1253 likely(page_private(page
) == entry
.val
))
1254 delete_from_swap_cache(page
);
1257 * So we could skip searching mms once swap count went
1258 * to 1, we did not mark any present ptes as dirty: must
1259 * mark page dirty so shrink_page_list will preserve it.
1263 page_cache_release(page
);
1266 * Make sure that we aren't completely killing
1267 * interactive performance.
1277 * After a successful try_to_unuse, if no swap is now in use, we know
1278 * we can empty the mmlist. swap_lock must be held on entry and exit.
1279 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1280 * added to the mmlist just after page_duplicate - before would be racy.
1282 static void drain_mmlist(void)
1284 struct list_head
*p
, *next
;
1287 for (type
= 0; type
< nr_swapfiles
; type
++)
1288 if (swap_info
[type
]->inuse_pages
)
1290 spin_lock(&mmlist_lock
);
1291 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
1293 spin_unlock(&mmlist_lock
);
1297 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1298 * corresponds to page offset for the specified swap entry.
1299 * Note that the type of this function is sector_t, but it returns page offset
1300 * into the bdev, not sector offset.
1302 static sector_t
map_swap_entry(swp_entry_t entry
, struct block_device
**bdev
)
1304 struct swap_info_struct
*sis
;
1305 struct swap_extent
*start_se
;
1306 struct swap_extent
*se
;
1309 sis
= swap_info
[swp_type(entry
)];
1312 offset
= swp_offset(entry
);
1313 start_se
= sis
->curr_swap_extent
;
1317 struct list_head
*lh
;
1319 if (se
->start_page
<= offset
&&
1320 offset
< (se
->start_page
+ se
->nr_pages
)) {
1321 return se
->start_block
+ (offset
- se
->start_page
);
1324 se
= list_entry(lh
, struct swap_extent
, list
);
1325 sis
->curr_swap_extent
= se
;
1326 BUG_ON(se
== start_se
); /* It *must* be present */
1331 * Returns the page offset into bdev for the specified page's swap entry.
1333 sector_t
map_swap_page(struct page
*page
, struct block_device
**bdev
)
1336 entry
.val
= page_private(page
);
1337 return map_swap_entry(entry
, bdev
);
1341 * Free all of a swapdev's extent information
1343 static void destroy_swap_extents(struct swap_info_struct
*sis
)
1345 while (!list_empty(&sis
->first_swap_extent
.list
)) {
1346 struct swap_extent
*se
;
1348 se
= list_entry(sis
->first_swap_extent
.list
.next
,
1349 struct swap_extent
, list
);
1350 list_del(&se
->list
);
1356 * Add a block range (and the corresponding page range) into this swapdev's
1357 * extent list. The extent list is kept sorted in page order.
1359 * This function rather assumes that it is called in ascending page order.
1362 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
1363 unsigned long nr_pages
, sector_t start_block
)
1365 struct swap_extent
*se
;
1366 struct swap_extent
*new_se
;
1367 struct list_head
*lh
;
1369 if (start_page
== 0) {
1370 se
= &sis
->first_swap_extent
;
1371 sis
->curr_swap_extent
= se
;
1373 se
->nr_pages
= nr_pages
;
1374 se
->start_block
= start_block
;
1377 lh
= sis
->first_swap_extent
.list
.prev
; /* Highest extent */
1378 se
= list_entry(lh
, struct swap_extent
, list
);
1379 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
1380 if (se
->start_block
+ se
->nr_pages
== start_block
) {
1382 se
->nr_pages
+= nr_pages
;
1388 * No merge. Insert a new extent, preserving ordering.
1390 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
1393 new_se
->start_page
= start_page
;
1394 new_se
->nr_pages
= nr_pages
;
1395 new_se
->start_block
= start_block
;
1397 list_add_tail(&new_se
->list
, &sis
->first_swap_extent
.list
);
1402 * A `swap extent' is a simple thing which maps a contiguous range of pages
1403 * onto a contiguous range of disk blocks. An ordered list of swap extents
1404 * is built at swapon time and is then used at swap_writepage/swap_readpage
1405 * time for locating where on disk a page belongs.
1407 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1408 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1409 * swap files identically.
1411 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1412 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1413 * swapfiles are handled *identically* after swapon time.
1415 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1416 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1417 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1418 * requirements, they are simply tossed out - we will never use those blocks
1421 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1422 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1423 * which will scribble on the fs.
1425 * The amount of disk space which a single swap extent represents varies.
1426 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1427 * extents in the list. To avoid much list walking, we cache the previous
1428 * search location in `curr_swap_extent', and start new searches from there.
1429 * This is extremely effective. The average number of iterations in
1430 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1432 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1434 struct inode
*inode
;
1435 unsigned blocks_per_page
;
1436 unsigned long page_no
;
1438 sector_t probe_block
;
1439 sector_t last_block
;
1440 sector_t lowest_block
= -1;
1441 sector_t highest_block
= 0;
1445 inode
= sis
->swap_file
->f_mapping
->host
;
1446 if (S_ISBLK(inode
->i_mode
)) {
1447 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1452 blkbits
= inode
->i_blkbits
;
1453 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1456 * Map all the blocks into the extent list. This code doesn't try
1461 last_block
= i_size_read(inode
) >> blkbits
;
1462 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1463 page_no
< sis
->max
) {
1464 unsigned block_in_page
;
1465 sector_t first_block
;
1467 first_block
= bmap(inode
, probe_block
);
1468 if (first_block
== 0)
1472 * It must be PAGE_SIZE aligned on-disk
1474 if (first_block
& (blocks_per_page
- 1)) {
1479 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1483 block
= bmap(inode
, probe_block
+ block_in_page
);
1486 if (block
!= first_block
+ block_in_page
) {
1493 first_block
>>= (PAGE_SHIFT
- blkbits
);
1494 if (page_no
) { /* exclude the header page */
1495 if (first_block
< lowest_block
)
1496 lowest_block
= first_block
;
1497 if (first_block
> highest_block
)
1498 highest_block
= first_block
;
1502 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1504 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1509 probe_block
+= blocks_per_page
;
1514 *span
= 1 + highest_block
- lowest_block
;
1516 page_no
= 1; /* force Empty message */
1518 sis
->pages
= page_no
- 1;
1519 sis
->highest_bit
= page_no
- 1;
1523 printk(KERN_ERR
"swapon: swapfile has holes\n");
1528 SYSCALL_DEFINE1(swapoff
, const char __user
*, specialfile
)
1530 struct swap_info_struct
*p
= NULL
;
1531 unsigned char *swap_map
;
1532 struct file
*swap_file
, *victim
;
1533 struct address_space
*mapping
;
1534 struct inode
*inode
;
1539 if (!capable(CAP_SYS_ADMIN
))
1542 pathname
= getname(specialfile
);
1543 err
= PTR_ERR(pathname
);
1544 if (IS_ERR(pathname
))
1547 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1549 err
= PTR_ERR(victim
);
1553 mapping
= victim
->f_mapping
;
1555 spin_lock(&swap_lock
);
1556 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
]->next
) {
1557 p
= swap_info
[type
];
1558 if (p
->flags
& SWP_WRITEOK
) {
1559 if (p
->swap_file
->f_mapping
== mapping
)
1566 spin_unlock(&swap_lock
);
1569 if (!security_vm_enough_memory(p
->pages
))
1570 vm_unacct_memory(p
->pages
);
1573 spin_unlock(&swap_lock
);
1577 swap_list
.head
= p
->next
;
1579 swap_info
[prev
]->next
= p
->next
;
1580 if (type
== swap_list
.next
) {
1581 /* just pick something that's safe... */
1582 swap_list
.next
= swap_list
.head
;
1585 for (i
= p
->next
; i
>= 0; i
= swap_info
[i
]->next
)
1586 swap_info
[i
]->prio
= p
->prio
--;
1589 nr_swap_pages
-= p
->pages
;
1590 total_swap_pages
-= p
->pages
;
1591 p
->flags
&= ~SWP_WRITEOK
;
1592 spin_unlock(&swap_lock
);
1594 current
->flags
|= PF_OOM_ORIGIN
;
1595 err
= try_to_unuse(type
);
1596 current
->flags
&= ~PF_OOM_ORIGIN
;
1599 /* re-insert swap space back into swap_list */
1600 spin_lock(&swap_lock
);
1602 p
->prio
= --least_priority
;
1604 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
]->next
) {
1605 if (p
->prio
>= swap_info
[i
]->prio
)
1611 swap_list
.head
= swap_list
.next
= type
;
1613 swap_info
[prev
]->next
= type
;
1614 nr_swap_pages
+= p
->pages
;
1615 total_swap_pages
+= p
->pages
;
1616 p
->flags
|= SWP_WRITEOK
;
1617 spin_unlock(&swap_lock
);
1621 /* wait for any unplug function to finish */
1622 down_write(&swap_unplug_sem
);
1623 up_write(&swap_unplug_sem
);
1625 destroy_swap_extents(p
);
1626 if (p
->flags
& SWP_CONTINUED
)
1627 free_swap_count_continuations(p
);
1629 mutex_lock(&swapon_mutex
);
1630 spin_lock(&swap_lock
);
1633 /* wait for anyone still in scan_swap_map */
1634 p
->highest_bit
= 0; /* cuts scans short */
1635 while (p
->flags
>= SWP_SCANNING
) {
1636 spin_unlock(&swap_lock
);
1637 schedule_timeout_uninterruptible(1);
1638 spin_lock(&swap_lock
);
1641 swap_file
= p
->swap_file
;
1642 p
->swap_file
= NULL
;
1644 swap_map
= p
->swap_map
;
1647 spin_unlock(&swap_lock
);
1648 mutex_unlock(&swapon_mutex
);
1650 /* Destroy swap account informatin */
1651 swap_cgroup_swapoff(type
);
1653 inode
= mapping
->host
;
1654 if (S_ISBLK(inode
->i_mode
)) {
1655 struct block_device
*bdev
= I_BDEV(inode
);
1656 set_blocksize(bdev
, p
->old_block_size
);
1659 mutex_lock(&inode
->i_mutex
);
1660 inode
->i_flags
&= ~S_SWAPFILE
;
1661 mutex_unlock(&inode
->i_mutex
);
1663 filp_close(swap_file
, NULL
);
1667 filp_close(victim
, NULL
);
1672 #ifdef CONFIG_PROC_FS
1674 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1676 struct swap_info_struct
*si
;
1680 mutex_lock(&swapon_mutex
);
1683 return SEQ_START_TOKEN
;
1685 for (type
= 0; type
< nr_swapfiles
; type
++) {
1686 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1687 si
= swap_info
[type
];
1688 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1697 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1699 struct swap_info_struct
*si
= v
;
1702 if (v
== SEQ_START_TOKEN
)
1705 type
= si
->type
+ 1;
1707 for (; type
< nr_swapfiles
; type
++) {
1708 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1709 si
= swap_info
[type
];
1710 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1719 static void swap_stop(struct seq_file
*swap
, void *v
)
1721 mutex_unlock(&swapon_mutex
);
1724 static int swap_show(struct seq_file
*swap
, void *v
)
1726 struct swap_info_struct
*si
= v
;
1730 if (si
== SEQ_START_TOKEN
) {
1731 seq_puts(swap
,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1735 file
= si
->swap_file
;
1736 len
= seq_path(swap
, &file
->f_path
, " \t\n\\");
1737 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1738 len
< 40 ? 40 - len
: 1, " ",
1739 S_ISBLK(file
->f_path
.dentry
->d_inode
->i_mode
) ?
1740 "partition" : "file\t",
1741 si
->pages
<< (PAGE_SHIFT
- 10),
1742 si
->inuse_pages
<< (PAGE_SHIFT
- 10),
1747 static const struct seq_operations swaps_op
= {
1748 .start
= swap_start
,
1754 static int swaps_open(struct inode
*inode
, struct file
*file
)
1756 return seq_open(file
, &swaps_op
);
1759 static const struct file_operations proc_swaps_operations
= {
1762 .llseek
= seq_lseek
,
1763 .release
= seq_release
,
1766 static int __init
procswaps_init(void)
1768 proc_create("swaps", 0, NULL
, &proc_swaps_operations
);
1771 __initcall(procswaps_init
);
1772 #endif /* CONFIG_PROC_FS */
1774 #ifdef MAX_SWAPFILES_CHECK
1775 static int __init
max_swapfiles_check(void)
1777 MAX_SWAPFILES_CHECK();
1780 late_initcall(max_swapfiles_check
);
1784 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1786 * The swapon system call
1788 SYSCALL_DEFINE2(swapon
, const char __user
*, specialfile
, int, swap_flags
)
1790 struct swap_info_struct
*p
;
1792 struct block_device
*bdev
= NULL
;
1793 struct file
*swap_file
= NULL
;
1794 struct address_space
*mapping
;
1798 union swap_header
*swap_header
;
1799 unsigned int nr_good_pages
;
1802 unsigned long maxpages
;
1803 unsigned long swapfilepages
;
1804 unsigned char *swap_map
= NULL
;
1805 struct page
*page
= NULL
;
1806 struct inode
*inode
= NULL
;
1809 if (!capable(CAP_SYS_ADMIN
))
1812 p
= kzalloc(sizeof(*p
), GFP_KERNEL
);
1816 spin_lock(&swap_lock
);
1817 for (type
= 0; type
< nr_swapfiles
; type
++) {
1818 if (!(swap_info
[type
]->flags
& SWP_USED
))
1822 if (type
>= MAX_SWAPFILES
) {
1823 spin_unlock(&swap_lock
);
1827 if (type
>= nr_swapfiles
) {
1829 swap_info
[type
] = p
;
1831 * Write swap_info[type] before nr_swapfiles, in case a
1832 * racing procfs swap_start() or swap_next() is reading them.
1833 * (We never shrink nr_swapfiles, we never free this entry.)
1839 p
= swap_info
[type
];
1841 * Do not memset this entry: a racing procfs swap_next()
1842 * would be relying on p->type to remain valid.
1845 INIT_LIST_HEAD(&p
->first_swap_extent
.list
);
1846 p
->flags
= SWP_USED
;
1848 spin_unlock(&swap_lock
);
1850 name
= getname(specialfile
);
1851 error
= PTR_ERR(name
);
1856 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1857 error
= PTR_ERR(swap_file
);
1858 if (IS_ERR(swap_file
)) {
1863 p
->swap_file
= swap_file
;
1864 mapping
= swap_file
->f_mapping
;
1865 inode
= mapping
->host
;
1868 for (i
= 0; i
< nr_swapfiles
; i
++) {
1869 struct swap_info_struct
*q
= swap_info
[i
];
1871 if (i
== type
|| !q
->swap_file
)
1873 if (mapping
== q
->swap_file
->f_mapping
)
1878 if (S_ISBLK(inode
->i_mode
)) {
1879 bdev
= I_BDEV(inode
);
1880 error
= bd_claim(bdev
, sys_swapon
);
1886 p
->old_block_size
= block_size(bdev
);
1887 error
= set_blocksize(bdev
, PAGE_SIZE
);
1891 p
->flags
|= SWP_BLKDEV
;
1892 } else if (S_ISREG(inode
->i_mode
)) {
1893 p
->bdev
= inode
->i_sb
->s_bdev
;
1894 mutex_lock(&inode
->i_mutex
);
1896 if (IS_SWAPFILE(inode
)) {
1904 swapfilepages
= i_size_read(inode
) >> PAGE_SHIFT
;
1907 * Read the swap header.
1909 if (!mapping
->a_ops
->readpage
) {
1913 page
= read_mapping_page(mapping
, 0, swap_file
);
1915 error
= PTR_ERR(page
);
1918 swap_header
= kmap(page
);
1920 if (memcmp("SWAPSPACE2", swap_header
->magic
.magic
, 10)) {
1921 printk(KERN_ERR
"Unable to find swap-space signature\n");
1926 /* swap partition endianess hack... */
1927 if (swab32(swap_header
->info
.version
) == 1) {
1928 swab32s(&swap_header
->info
.version
);
1929 swab32s(&swap_header
->info
.last_page
);
1930 swab32s(&swap_header
->info
.nr_badpages
);
1931 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++)
1932 swab32s(&swap_header
->info
.badpages
[i
]);
1934 /* Check the swap header's sub-version */
1935 if (swap_header
->info
.version
!= 1) {
1937 "Unable to handle swap header version %d\n",
1938 swap_header
->info
.version
);
1944 p
->cluster_next
= 1;
1948 * Find out how many pages are allowed for a single swap
1949 * device. There are two limiting factors: 1) the number of
1950 * bits for the swap offset in the swp_entry_t type and
1951 * 2) the number of bits in the a swap pte as defined by
1952 * the different architectures. In order to find the
1953 * largest possible bit mask a swap entry with swap type 0
1954 * and swap offset ~0UL is created, encoded to a swap pte,
1955 * decoded to a swp_entry_t again and finally the swap
1956 * offset is extracted. This will mask all the bits from
1957 * the initial ~0UL mask that can't be encoded in either
1958 * the swp_entry_t or the architecture definition of a
1961 maxpages
= swp_offset(pte_to_swp_entry(
1962 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
1963 if (maxpages
> swap_header
->info
.last_page
) {
1964 maxpages
= swap_header
->info
.last_page
+ 1;
1965 /* p->max is an unsigned int: don't overflow it */
1966 if ((unsigned int)maxpages
== 0)
1967 maxpages
= UINT_MAX
;
1969 p
->highest_bit
= maxpages
- 1;
1974 if (swapfilepages
&& maxpages
> swapfilepages
) {
1976 "Swap area shorter than signature indicates\n");
1979 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1981 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1984 /* OK, set up the swap map and apply the bad block list */
1985 swap_map
= vmalloc(maxpages
);
1991 memset(swap_map
, 0, maxpages
);
1992 nr_good_pages
= maxpages
- 1; /* omit header page */
1994 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
1995 unsigned int page_nr
= swap_header
->info
.badpages
[i
];
1996 if (page_nr
== 0 || page_nr
> swap_header
->info
.last_page
) {
2000 if (page_nr
< maxpages
) {
2001 swap_map
[page_nr
] = SWAP_MAP_BAD
;
2006 error
= swap_cgroup_swapon(type
, maxpages
);
2010 if (nr_good_pages
) {
2011 swap_map
[0] = SWAP_MAP_BAD
;
2013 p
->pages
= nr_good_pages
;
2014 nr_extents
= setup_swap_extents(p
, &span
);
2015 if (nr_extents
< 0) {
2019 nr_good_pages
= p
->pages
;
2021 if (!nr_good_pages
) {
2022 printk(KERN_WARNING
"Empty swap-file\n");
2028 if (blk_queue_nonrot(bdev_get_queue(p
->bdev
))) {
2029 p
->flags
|= SWP_SOLIDSTATE
;
2030 p
->cluster_next
= 1 + (random32() % p
->highest_bit
);
2032 if (discard_swap(p
) == 0)
2033 p
->flags
|= SWP_DISCARDABLE
;
2036 mutex_lock(&swapon_mutex
);
2037 spin_lock(&swap_lock
);
2038 if (swap_flags
& SWAP_FLAG_PREFER
)
2040 (swap_flags
& SWAP_FLAG_PRIO_MASK
) >> SWAP_FLAG_PRIO_SHIFT
;
2042 p
->prio
= --least_priority
;
2043 p
->swap_map
= swap_map
;
2044 p
->flags
|= SWP_WRITEOK
;
2045 nr_swap_pages
+= nr_good_pages
;
2046 total_swap_pages
+= nr_good_pages
;
2048 printk(KERN_INFO
"Adding %uk swap on %s. "
2049 "Priority:%d extents:%d across:%lluk %s%s\n",
2050 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
2051 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10),
2052 (p
->flags
& SWP_SOLIDSTATE
) ? "SS" : "",
2053 (p
->flags
& SWP_DISCARDABLE
) ? "D" : "");
2055 /* insert swap space into swap_list: */
2057 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
]->next
) {
2058 if (p
->prio
>= swap_info
[i
]->prio
)
2064 swap_list
.head
= swap_list
.next
= type
;
2066 swap_info
[prev
]->next
= type
;
2067 spin_unlock(&swap_lock
);
2068 mutex_unlock(&swapon_mutex
);
2073 set_blocksize(bdev
, p
->old_block_size
);
2076 destroy_swap_extents(p
);
2077 swap_cgroup_swapoff(type
);
2079 spin_lock(&swap_lock
);
2080 p
->swap_file
= NULL
;
2082 spin_unlock(&swap_lock
);
2085 filp_close(swap_file
, NULL
);
2087 if (page
&& !IS_ERR(page
)) {
2089 page_cache_release(page
);
2095 inode
->i_flags
|= S_SWAPFILE
;
2096 mutex_unlock(&inode
->i_mutex
);
2101 void si_swapinfo(struct sysinfo
*val
)
2104 unsigned long nr_to_be_unused
= 0;
2106 spin_lock(&swap_lock
);
2107 for (type
= 0; type
< nr_swapfiles
; type
++) {
2108 struct swap_info_struct
*si
= swap_info
[type
];
2110 if ((si
->flags
& SWP_USED
) && !(si
->flags
& SWP_WRITEOK
))
2111 nr_to_be_unused
+= si
->inuse_pages
;
2113 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
2114 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
2115 spin_unlock(&swap_lock
);
2119 * Verify that a swap entry is valid and increment its swap map count.
2121 * Returns error code in following case.
2123 * - swp_entry is invalid -> EINVAL
2124 * - swp_entry is migration entry -> EINVAL
2125 * - swap-cache reference is requested but there is already one. -> EEXIST
2126 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2127 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2129 static int __swap_duplicate(swp_entry_t entry
, unsigned char usage
)
2131 struct swap_info_struct
*p
;
2132 unsigned long offset
, type
;
2133 unsigned char count
;
2134 unsigned char has_cache
;
2137 if (non_swap_entry(entry
))
2140 type
= swp_type(entry
);
2141 if (type
>= nr_swapfiles
)
2143 p
= swap_info
[type
];
2144 offset
= swp_offset(entry
);
2146 spin_lock(&swap_lock
);
2147 if (unlikely(offset
>= p
->max
))
2150 count
= p
->swap_map
[offset
];
2151 has_cache
= count
& SWAP_HAS_CACHE
;
2152 count
&= ~SWAP_HAS_CACHE
;
2155 if (usage
== SWAP_HAS_CACHE
) {
2157 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2158 if (!has_cache
&& count
)
2159 has_cache
= SWAP_HAS_CACHE
;
2160 else if (has_cache
) /* someone else added cache */
2162 else /* no users remaining */
2165 } else if (count
|| has_cache
) {
2167 if ((count
& ~COUNT_CONTINUED
) < SWAP_MAP_MAX
)
2169 else if ((count
& ~COUNT_CONTINUED
) > SWAP_MAP_MAX
)
2171 else if (swap_count_continued(p
, offset
, count
))
2172 count
= COUNT_CONTINUED
;
2176 err
= -ENOENT
; /* unused swap entry */
2178 p
->swap_map
[offset
] = count
| has_cache
;
2181 spin_unlock(&swap_lock
);
2186 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
2191 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2192 * (in which case its reference count is never incremented).
2194 void swap_shmem_alloc(swp_entry_t entry
)
2196 __swap_duplicate(entry
, SWAP_MAP_SHMEM
);
2200 * Increase reference count of swap entry by 1.
2201 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2202 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2203 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2204 * might occur if a page table entry has got corrupted.
2206 int swap_duplicate(swp_entry_t entry
)
2210 while (!err
&& __swap_duplicate(entry
, 1) == -ENOMEM
)
2211 err
= add_swap_count_continuation(entry
, GFP_ATOMIC
);
2216 * @entry: swap entry for which we allocate swap cache.
2218 * Called when allocating swap cache for existing swap entry,
2219 * This can return error codes. Returns 0 at success.
2220 * -EBUSY means there is a swap cache.
2221 * Note: return code is different from swap_duplicate().
2223 int swapcache_prepare(swp_entry_t entry
)
2225 return __swap_duplicate(entry
, SWAP_HAS_CACHE
);
2229 * swap_lock prevents swap_map being freed. Don't grab an extra
2230 * reference on the swaphandle, it doesn't matter if it becomes unused.
2232 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
2234 struct swap_info_struct
*si
;
2235 int our_page_cluster
= page_cluster
;
2236 pgoff_t target
, toff
;
2240 if (!our_page_cluster
) /* no readahead */
2243 si
= swap_info
[swp_type(entry
)];
2244 target
= swp_offset(entry
);
2245 base
= (target
>> our_page_cluster
) << our_page_cluster
;
2246 end
= base
+ (1 << our_page_cluster
);
2247 if (!base
) /* first page is swap header */
2250 spin_lock(&swap_lock
);
2251 if (end
> si
->max
) /* don't go beyond end of map */
2254 /* Count contiguous allocated slots above our target */
2255 for (toff
= target
; ++toff
< end
; nr_pages
++) {
2256 /* Don't read in free or bad pages */
2257 if (!si
->swap_map
[toff
])
2259 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2262 /* Count contiguous allocated slots below our target */
2263 for (toff
= target
; --toff
>= base
; nr_pages
++) {
2264 /* Don't read in free or bad pages */
2265 if (!si
->swap_map
[toff
])
2267 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2270 spin_unlock(&swap_lock
);
2273 * Indicate starting offset, and return number of pages to get:
2274 * if only 1, say 0, since there's then no readahead to be done.
2277 return nr_pages
? ++nr_pages
: 0;
2281 * add_swap_count_continuation - called when a swap count is duplicated
2282 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2283 * page of the original vmalloc'ed swap_map, to hold the continuation count
2284 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2285 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2287 * These continuation pages are seldom referenced: the common paths all work
2288 * on the original swap_map, only referring to a continuation page when the
2289 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2291 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2292 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2293 * can be called after dropping locks.
2295 int add_swap_count_continuation(swp_entry_t entry
, gfp_t gfp_mask
)
2297 struct swap_info_struct
*si
;
2300 struct page
*list_page
;
2302 unsigned char count
;
2305 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2306 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2308 page
= alloc_page(gfp_mask
| __GFP_HIGHMEM
);
2310 si
= swap_info_get(entry
);
2313 * An acceptable race has occurred since the failing
2314 * __swap_duplicate(): the swap entry has been freed,
2315 * perhaps even the whole swap_map cleared for swapoff.
2320 offset
= swp_offset(entry
);
2321 count
= si
->swap_map
[offset
] & ~SWAP_HAS_CACHE
;
2323 if ((count
& ~COUNT_CONTINUED
) != SWAP_MAP_MAX
) {
2325 * The higher the swap count, the more likely it is that tasks
2326 * will race to add swap count continuation: we need to avoid
2327 * over-provisioning.
2333 spin_unlock(&swap_lock
);
2338 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2339 * no architecture is using highmem pages for kernel pagetables: so it
2340 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2342 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2343 offset
&= ~PAGE_MASK
;
2346 * Page allocation does not initialize the page's lru field,
2347 * but it does always reset its private field.
2349 if (!page_private(head
)) {
2350 BUG_ON(count
& COUNT_CONTINUED
);
2351 INIT_LIST_HEAD(&head
->lru
);
2352 set_page_private(head
, SWP_CONTINUED
);
2353 si
->flags
|= SWP_CONTINUED
;
2356 list_for_each_entry(list_page
, &head
->lru
, lru
) {
2360 * If the previous map said no continuation, but we've found
2361 * a continuation page, free our allocation and use this one.
2363 if (!(count
& COUNT_CONTINUED
))
2366 map
= kmap_atomic(list_page
, KM_USER0
) + offset
;
2368 kunmap_atomic(map
, KM_USER0
);
2371 * If this continuation count now has some space in it,
2372 * free our allocation and use this one.
2374 if ((count
& ~COUNT_CONTINUED
) != SWAP_CONT_MAX
)
2378 list_add_tail(&page
->lru
, &head
->lru
);
2379 page
= NULL
; /* now it's attached, don't free it */
2381 spin_unlock(&swap_lock
);
2389 * swap_count_continued - when the original swap_map count is incremented
2390 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2391 * into, carry if so, or else fail until a new continuation page is allocated;
2392 * when the original swap_map count is decremented from 0 with continuation,
2393 * borrow from the continuation and report whether it still holds more.
2394 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2396 static bool swap_count_continued(struct swap_info_struct
*si
,
2397 pgoff_t offset
, unsigned char count
)
2403 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2404 if (page_private(head
) != SWP_CONTINUED
) {
2405 BUG_ON(count
& COUNT_CONTINUED
);
2406 return false; /* need to add count continuation */
2409 offset
&= ~PAGE_MASK
;
2410 page
= list_entry(head
->lru
.next
, struct page
, lru
);
2411 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2413 if (count
== SWAP_MAP_MAX
) /* initial increment from swap_map */
2414 goto init_map
; /* jump over SWAP_CONT_MAX checks */
2416 if (count
== (SWAP_MAP_MAX
| COUNT_CONTINUED
)) { /* incrementing */
2418 * Think of how you add 1 to 999
2420 while (*map
== (SWAP_CONT_MAX
| COUNT_CONTINUED
)) {
2421 kunmap_atomic(map
, KM_USER0
);
2422 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2423 BUG_ON(page
== head
);
2424 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2426 if (*map
== SWAP_CONT_MAX
) {
2427 kunmap_atomic(map
, KM_USER0
);
2428 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2430 return false; /* add count continuation */
2431 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2432 init_map
: *map
= 0; /* we didn't zero the page */
2435 kunmap_atomic(map
, KM_USER0
);
2436 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2437 while (page
!= head
) {
2438 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2439 *map
= COUNT_CONTINUED
;
2440 kunmap_atomic(map
, KM_USER0
);
2441 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2443 return true; /* incremented */
2445 } else { /* decrementing */
2447 * Think of how you subtract 1 from 1000
2449 BUG_ON(count
!= COUNT_CONTINUED
);
2450 while (*map
== COUNT_CONTINUED
) {
2451 kunmap_atomic(map
, KM_USER0
);
2452 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2453 BUG_ON(page
== head
);
2454 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2460 kunmap_atomic(map
, KM_USER0
);
2461 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2462 while (page
!= head
) {
2463 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2464 *map
= SWAP_CONT_MAX
| count
;
2465 count
= COUNT_CONTINUED
;
2466 kunmap_atomic(map
, KM_USER0
);
2467 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2469 return count
== COUNT_CONTINUED
;
2474 * free_swap_count_continuations - swapoff free all the continuation pages
2475 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2477 static void free_swap_count_continuations(struct swap_info_struct
*si
)
2481 for (offset
= 0; offset
< si
->max
; offset
+= PAGE_SIZE
) {
2483 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2484 if (page_private(head
)) {
2485 struct list_head
*this, *next
;
2486 list_for_each_safe(this, next
, &head
->lru
) {
2488 page
= list_entry(this, struct page
, lru
);