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/shmem_fs.h>
18 #include <linux/blkdev.h>
19 #include <linux/random.h>
20 #include <linux/writeback.h>
21 #include <linux/proc_fs.h>
22 #include <linux/seq_file.h>
23 #include <linux/init.h>
24 #include <linux/ksm.h>
25 #include <linux/rmap.h>
26 #include <linux/security.h>
27 #include <linux/backing-dev.h>
28 #include <linux/mutex.h>
29 #include <linux/capability.h>
30 #include <linux/syscalls.h>
31 #include <linux/memcontrol.h>
32 #include <linux/poll.h>
33 #include <linux/oom.h>
34 #include <linux/frontswap.h>
35 #include <linux/swapfile.h>
37 #include <asm/pgtable.h>
38 #include <asm/tlbflush.h>
39 #include <linux/swapops.h>
40 #include <linux/page_cgroup.h>
42 static bool swap_count_continued(struct swap_info_struct
*, pgoff_t
,
44 static void free_swap_count_continuations(struct swap_info_struct
*);
45 static sector_t
map_swap_entry(swp_entry_t
, struct block_device
**);
47 DEFINE_SPINLOCK(swap_lock
);
48 static unsigned int nr_swapfiles
;
50 long total_swap_pages
;
51 static int least_priority
;
53 static const char Bad_file
[] = "Bad swap file entry ";
54 static const char Unused_file
[] = "Unused swap file entry ";
55 static const char Bad_offset
[] = "Bad swap offset entry ";
56 static const char Unused_offset
[] = "Unused swap offset entry ";
58 struct swap_list_t swap_list
= {-1, -1};
60 struct swap_info_struct
*swap_info
[MAX_SWAPFILES
];
62 static DEFINE_MUTEX(swapon_mutex
);
64 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait
);
65 /* Activity counter to indicate that a swapon or swapoff has occurred */
66 static atomic_t proc_poll_event
= ATOMIC_INIT(0);
68 static inline unsigned char swap_count(unsigned char ent
)
70 return ent
& ~SWAP_HAS_CACHE
; /* may include SWAP_HAS_CONT flag */
73 /* returns 1 if swap entry is freed */
75 __try_to_reclaim_swap(struct swap_info_struct
*si
, unsigned long offset
)
77 swp_entry_t entry
= swp_entry(si
->type
, offset
);
81 page
= find_get_page(&swapper_space
, entry
.val
);
85 * This function is called from scan_swap_map() and it's called
86 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
87 * We have to use trylock for avoiding deadlock. This is a special
88 * case and you should use try_to_free_swap() with explicit lock_page()
89 * in usual operations.
91 if (trylock_page(page
)) {
92 ret
= try_to_free_swap(page
);
95 page_cache_release(page
);
100 * swapon tell device that all the old swap contents can be discarded,
101 * to allow the swap device to optimize its wear-levelling.
103 static int discard_swap(struct swap_info_struct
*si
)
105 struct swap_extent
*se
;
106 sector_t start_block
;
110 /* Do not discard the swap header page! */
111 se
= &si
->first_swap_extent
;
112 start_block
= (se
->start_block
+ 1) << (PAGE_SHIFT
- 9);
113 nr_blocks
= ((sector_t
)se
->nr_pages
- 1) << (PAGE_SHIFT
- 9);
115 err
= blkdev_issue_discard(si
->bdev
, start_block
,
116 nr_blocks
, GFP_KERNEL
, 0);
122 list_for_each_entry(se
, &si
->first_swap_extent
.list
, list
) {
123 start_block
= se
->start_block
<< (PAGE_SHIFT
- 9);
124 nr_blocks
= (sector_t
)se
->nr_pages
<< (PAGE_SHIFT
- 9);
126 err
= blkdev_issue_discard(si
->bdev
, start_block
,
127 nr_blocks
, GFP_KERNEL
, 0);
133 return err
; /* That will often be -EOPNOTSUPP */
137 * swap allocation tell device that a cluster of swap can now be discarded,
138 * to allow the swap device to optimize its wear-levelling.
140 static void discard_swap_cluster(struct swap_info_struct
*si
,
141 pgoff_t start_page
, pgoff_t nr_pages
)
143 struct swap_extent
*se
= si
->curr_swap_extent
;
144 int found_extent
= 0;
147 struct list_head
*lh
;
149 if (se
->start_page
<= start_page
&&
150 start_page
< se
->start_page
+ se
->nr_pages
) {
151 pgoff_t offset
= start_page
- se
->start_page
;
152 sector_t start_block
= se
->start_block
+ offset
;
153 sector_t nr_blocks
= se
->nr_pages
- offset
;
155 if (nr_blocks
> nr_pages
)
156 nr_blocks
= nr_pages
;
157 start_page
+= nr_blocks
;
158 nr_pages
-= nr_blocks
;
161 si
->curr_swap_extent
= se
;
163 start_block
<<= PAGE_SHIFT
- 9;
164 nr_blocks
<<= PAGE_SHIFT
- 9;
165 if (blkdev_issue_discard(si
->bdev
, start_block
,
166 nr_blocks
, GFP_NOIO
, 0))
171 se
= list_entry(lh
, struct swap_extent
, list
);
175 static int wait_for_discard(void *word
)
181 #define SWAPFILE_CLUSTER 256
182 #define LATENCY_LIMIT 256
184 static unsigned long scan_swap_map(struct swap_info_struct
*si
,
187 unsigned long offset
;
188 unsigned long scan_base
;
189 unsigned long last_in_cluster
= 0;
190 int latency_ration
= LATENCY_LIMIT
;
191 int found_free_cluster
= 0;
194 * We try to cluster swap pages by allocating them sequentially
195 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
196 * way, however, we resort to first-free allocation, starting
197 * a new cluster. This prevents us from scattering swap pages
198 * all over the entire swap partition, so that we reduce
199 * overall disk seek times between swap pages. -- sct
200 * But we do now try to find an empty cluster. -Andrea
201 * And we let swap pages go all over an SSD partition. Hugh
204 si
->flags
+= SWP_SCANNING
;
205 scan_base
= offset
= si
->cluster_next
;
207 if (unlikely(!si
->cluster_nr
--)) {
208 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
) {
209 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
212 if (si
->flags
& SWP_DISCARDABLE
) {
214 * Start range check on racing allocations, in case
215 * they overlap the cluster we eventually decide on
216 * (we scan without swap_lock to allow preemption).
217 * It's hardly conceivable that cluster_nr could be
218 * wrapped during our scan, but don't depend on it.
220 if (si
->lowest_alloc
)
222 si
->lowest_alloc
= si
->max
;
223 si
->highest_alloc
= 0;
225 spin_unlock(&swap_lock
);
228 * If seek is expensive, start searching for new cluster from
229 * start of partition, to minimize the span of allocated swap.
230 * But if seek is cheap, search from our current position, so
231 * that swap is allocated from all over the partition: if the
232 * Flash Translation Layer only remaps within limited zones,
233 * we don't want to wear out the first zone too quickly.
235 if (!(si
->flags
& SWP_SOLIDSTATE
))
236 scan_base
= offset
= si
->lowest_bit
;
237 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
239 /* Locate the first empty (unaligned) cluster */
240 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
241 if (si
->swap_map
[offset
])
242 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
243 else if (offset
== last_in_cluster
) {
244 spin_lock(&swap_lock
);
245 offset
-= SWAPFILE_CLUSTER
- 1;
246 si
->cluster_next
= offset
;
247 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
248 found_free_cluster
= 1;
251 if (unlikely(--latency_ration
< 0)) {
253 latency_ration
= LATENCY_LIMIT
;
257 offset
= si
->lowest_bit
;
258 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
260 /* Locate the first empty (unaligned) cluster */
261 for (; last_in_cluster
< scan_base
; offset
++) {
262 if (si
->swap_map
[offset
])
263 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
264 else if (offset
== last_in_cluster
) {
265 spin_lock(&swap_lock
);
266 offset
-= SWAPFILE_CLUSTER
- 1;
267 si
->cluster_next
= offset
;
268 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
269 found_free_cluster
= 1;
272 if (unlikely(--latency_ration
< 0)) {
274 latency_ration
= LATENCY_LIMIT
;
279 spin_lock(&swap_lock
);
280 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
281 si
->lowest_alloc
= 0;
285 if (!(si
->flags
& SWP_WRITEOK
))
287 if (!si
->highest_bit
)
289 if (offset
> si
->highest_bit
)
290 scan_base
= offset
= si
->lowest_bit
;
292 /* reuse swap entry of cache-only swap if not busy. */
293 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
295 spin_unlock(&swap_lock
);
296 swap_was_freed
= __try_to_reclaim_swap(si
, offset
);
297 spin_lock(&swap_lock
);
298 /* entry was freed successfully, try to use this again */
301 goto scan
; /* check next one */
304 if (si
->swap_map
[offset
])
307 if (offset
== si
->lowest_bit
)
309 if (offset
== si
->highest_bit
)
312 if (si
->inuse_pages
== si
->pages
) {
313 si
->lowest_bit
= si
->max
;
316 si
->swap_map
[offset
] = usage
;
317 si
->cluster_next
= offset
+ 1;
318 si
->flags
-= SWP_SCANNING
;
320 if (si
->lowest_alloc
) {
322 * Only set when SWP_DISCARDABLE, and there's a scan
323 * for a free cluster in progress or just completed.
325 if (found_free_cluster
) {
327 * To optimize wear-levelling, discard the
328 * old data of the cluster, taking care not to
329 * discard any of its pages that have already
330 * been allocated by racing tasks (offset has
331 * already stepped over any at the beginning).
333 if (offset
< si
->highest_alloc
&&
334 si
->lowest_alloc
<= last_in_cluster
)
335 last_in_cluster
= si
->lowest_alloc
- 1;
336 si
->flags
|= SWP_DISCARDING
;
337 spin_unlock(&swap_lock
);
339 if (offset
< last_in_cluster
)
340 discard_swap_cluster(si
, offset
,
341 last_in_cluster
- offset
+ 1);
343 spin_lock(&swap_lock
);
344 si
->lowest_alloc
= 0;
345 si
->flags
&= ~SWP_DISCARDING
;
347 smp_mb(); /* wake_up_bit advises this */
348 wake_up_bit(&si
->flags
, ilog2(SWP_DISCARDING
));
350 } else if (si
->flags
& SWP_DISCARDING
) {
352 * Delay using pages allocated by racing tasks
353 * until the whole discard has been issued. We
354 * could defer that delay until swap_writepage,
355 * but it's easier to keep this self-contained.
357 spin_unlock(&swap_lock
);
358 wait_on_bit(&si
->flags
, ilog2(SWP_DISCARDING
),
359 wait_for_discard
, TASK_UNINTERRUPTIBLE
);
360 spin_lock(&swap_lock
);
363 * Note pages allocated by racing tasks while
364 * scan for a free cluster is in progress, so
365 * that its final discard can exclude them.
367 if (offset
< si
->lowest_alloc
)
368 si
->lowest_alloc
= offset
;
369 if (offset
> si
->highest_alloc
)
370 si
->highest_alloc
= offset
;
376 spin_unlock(&swap_lock
);
377 while (++offset
<= si
->highest_bit
) {
378 if (!si
->swap_map
[offset
]) {
379 spin_lock(&swap_lock
);
382 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
383 spin_lock(&swap_lock
);
386 if (unlikely(--latency_ration
< 0)) {
388 latency_ration
= LATENCY_LIMIT
;
391 offset
= si
->lowest_bit
;
392 while (++offset
< scan_base
) {
393 if (!si
->swap_map
[offset
]) {
394 spin_lock(&swap_lock
);
397 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
398 spin_lock(&swap_lock
);
401 if (unlikely(--latency_ration
< 0)) {
403 latency_ration
= LATENCY_LIMIT
;
406 spin_lock(&swap_lock
);
409 si
->flags
-= SWP_SCANNING
;
413 swp_entry_t
get_swap_page(void)
415 struct swap_info_struct
*si
;
420 spin_lock(&swap_lock
);
421 if (nr_swap_pages
<= 0)
425 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
426 si
= swap_info
[type
];
429 (!wrapped
&& si
->prio
!= swap_info
[next
]->prio
)) {
430 next
= swap_list
.head
;
434 if (!si
->highest_bit
)
436 if (!(si
->flags
& SWP_WRITEOK
))
439 swap_list
.next
= next
;
440 /* This is called for allocating swap entry for cache */
441 offset
= scan_swap_map(si
, SWAP_HAS_CACHE
);
443 spin_unlock(&swap_lock
);
444 return swp_entry(type
, offset
);
446 next
= swap_list
.next
;
451 spin_unlock(&swap_lock
);
452 return (swp_entry_t
) {0};
455 /* The only caller of this function is now susupend routine */
456 swp_entry_t
get_swap_page_of_type(int type
)
458 struct swap_info_struct
*si
;
461 spin_lock(&swap_lock
);
462 si
= swap_info
[type
];
463 if (si
&& (si
->flags
& SWP_WRITEOK
)) {
465 /* This is called for allocating swap entry, not cache */
466 offset
= scan_swap_map(si
, 1);
468 spin_unlock(&swap_lock
);
469 return swp_entry(type
, offset
);
473 spin_unlock(&swap_lock
);
474 return (swp_entry_t
) {0};
477 static struct swap_info_struct
*swap_info_get(swp_entry_t entry
)
479 struct swap_info_struct
*p
;
480 unsigned long offset
, type
;
484 type
= swp_type(entry
);
485 if (type
>= nr_swapfiles
)
488 if (!(p
->flags
& SWP_USED
))
490 offset
= swp_offset(entry
);
491 if (offset
>= p
->max
)
493 if (!p
->swap_map
[offset
])
495 spin_lock(&swap_lock
);
499 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
502 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
505 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
508 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
513 static unsigned char swap_entry_free(struct swap_info_struct
*p
,
514 swp_entry_t entry
, unsigned char usage
)
516 unsigned long offset
= swp_offset(entry
);
518 unsigned char has_cache
;
520 count
= p
->swap_map
[offset
];
521 has_cache
= count
& SWAP_HAS_CACHE
;
522 count
&= ~SWAP_HAS_CACHE
;
524 if (usage
== SWAP_HAS_CACHE
) {
525 VM_BUG_ON(!has_cache
);
527 } else if (count
== SWAP_MAP_SHMEM
) {
529 * Or we could insist on shmem.c using a special
530 * swap_shmem_free() and free_shmem_swap_and_cache()...
533 } else if ((count
& ~COUNT_CONTINUED
) <= SWAP_MAP_MAX
) {
534 if (count
== COUNT_CONTINUED
) {
535 if (swap_count_continued(p
, offset
, count
))
536 count
= SWAP_MAP_MAX
| COUNT_CONTINUED
;
538 count
= SWAP_MAP_MAX
;
544 mem_cgroup_uncharge_swap(entry
);
546 usage
= count
| has_cache
;
547 p
->swap_map
[offset
] = usage
;
549 /* free if no reference */
551 struct gendisk
*disk
= p
->bdev
->bd_disk
;
552 if (offset
< p
->lowest_bit
)
553 p
->lowest_bit
= offset
;
554 if (offset
> p
->highest_bit
)
555 p
->highest_bit
= offset
;
556 if (swap_list
.next
>= 0 &&
557 p
->prio
> swap_info
[swap_list
.next
]->prio
)
558 swap_list
.next
= p
->type
;
561 frontswap_flush_page(p
->type
, offset
);
562 if ((p
->flags
& SWP_BLKDEV
) &&
563 disk
->fops
->swap_slot_free_notify
)
564 disk
->fops
->swap_slot_free_notify(p
->bdev
, offset
);
571 * Caller has made sure that the swapdevice corresponding to entry
572 * is still around or has not been recycled.
574 void swap_free(swp_entry_t entry
)
576 struct swap_info_struct
*p
;
578 p
= swap_info_get(entry
);
580 swap_entry_free(p
, entry
, 1);
581 spin_unlock(&swap_lock
);
586 * Called after dropping swapcache to decrease refcnt to swap entries.
588 void swapcache_free(swp_entry_t entry
, struct page
*page
)
590 struct swap_info_struct
*p
;
593 p
= swap_info_get(entry
);
595 count
= swap_entry_free(p
, entry
, SWAP_HAS_CACHE
);
597 mem_cgroup_uncharge_swapcache(page
, entry
, count
!= 0);
598 spin_unlock(&swap_lock
);
603 * How many references to page are currently swapped out?
604 * This does not give an exact answer when swap count is continued,
605 * but does include the high COUNT_CONTINUED flag to allow for that.
607 static inline int page_swapcount(struct page
*page
)
610 struct swap_info_struct
*p
;
613 entry
.val
= page_private(page
);
614 p
= swap_info_get(entry
);
616 count
= swap_count(p
->swap_map
[swp_offset(entry
)]);
617 spin_unlock(&swap_lock
);
623 * We can write to an anon page without COW if there are no other references
624 * to it. And as a side-effect, free up its swap: because the old content
625 * on disk will never be read, and seeking back there to write new content
626 * later would only waste time away from clustering.
628 int reuse_swap_page(struct page
*page
)
632 VM_BUG_ON(!PageLocked(page
));
633 if (unlikely(PageKsm(page
)))
635 count
= page_mapcount(page
);
636 if (count
<= 1 && PageSwapCache(page
)) {
637 count
+= page_swapcount(page
);
638 if (count
== 1 && !PageWriteback(page
)) {
639 delete_from_swap_cache(page
);
647 * If swap is getting full, or if there are no more mappings of this page,
648 * then try_to_free_swap is called to free its swap space.
650 int try_to_free_swap(struct page
*page
)
652 VM_BUG_ON(!PageLocked(page
));
654 if (!PageSwapCache(page
))
656 if (PageWriteback(page
))
658 if (page_swapcount(page
))
662 * Once hibernation has begun to create its image of memory,
663 * there's a danger that one of the calls to try_to_free_swap()
664 * - most probably a call from __try_to_reclaim_swap() while
665 * hibernation is allocating its own swap pages for the image,
666 * but conceivably even a call from memory reclaim - will free
667 * the swap from a page which has already been recorded in the
668 * image as a clean swapcache page, and then reuse its swap for
669 * another page of the image. On waking from hibernation, the
670 * original page might be freed under memory pressure, then
671 * later read back in from swap, now with the wrong data.
673 * Hibernation clears bits from gfp_allowed_mask to prevent
674 * memory reclaim from writing to disk, so check that here.
676 if (!(gfp_allowed_mask
& __GFP_IO
))
679 delete_from_swap_cache(page
);
685 * Free the swap entry like above, but also try to
686 * free the page cache entry if it is the last user.
688 int free_swap_and_cache(swp_entry_t entry
)
690 struct swap_info_struct
*p
;
691 struct page
*page
= NULL
;
693 if (non_swap_entry(entry
))
696 p
= swap_info_get(entry
);
698 if (swap_entry_free(p
, entry
, 1) == SWAP_HAS_CACHE
) {
699 page
= find_get_page(&swapper_space
, entry
.val
);
700 if (page
&& !trylock_page(page
)) {
701 page_cache_release(page
);
705 spin_unlock(&swap_lock
);
709 * Not mapped elsewhere, or swap space full? Free it!
710 * Also recheck PageSwapCache now page is locked (above).
712 if (PageSwapCache(page
) && !PageWriteback(page
) &&
713 (!page_mapped(page
) || vm_swap_full())) {
714 delete_from_swap_cache(page
);
718 page_cache_release(page
);
723 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
725 * mem_cgroup_count_swap_user - count the user of a swap entry
726 * @ent: the swap entry to be checked
727 * @pagep: the pointer for the swap cache page of the entry to be stored
729 * Returns the number of the user of the swap entry. The number is valid only
730 * for swaps of anonymous pages.
731 * If the entry is found on swap cache, the page is stored to pagep with
732 * refcount of it being incremented.
734 int mem_cgroup_count_swap_user(swp_entry_t ent
, struct page
**pagep
)
737 struct swap_info_struct
*p
;
740 page
= find_get_page(&swapper_space
, ent
.val
);
742 count
+= page_mapcount(page
);
743 p
= swap_info_get(ent
);
745 count
+= swap_count(p
->swap_map
[swp_offset(ent
)]);
746 spin_unlock(&swap_lock
);
754 #ifdef CONFIG_HIBERNATION
756 * Find the swap type that corresponds to given device (if any).
758 * @offset - number of the PAGE_SIZE-sized block of the device, starting
759 * from 0, in which the swap header is expected to be located.
761 * This is needed for the suspend to disk (aka swsusp).
763 int swap_type_of(dev_t device
, sector_t offset
, struct block_device
**bdev_p
)
765 struct block_device
*bdev
= NULL
;
769 bdev
= bdget(device
);
771 spin_lock(&swap_lock
);
772 for (type
= 0; type
< nr_swapfiles
; type
++) {
773 struct swap_info_struct
*sis
= swap_info
[type
];
775 if (!(sis
->flags
& SWP_WRITEOK
))
780 *bdev_p
= bdgrab(sis
->bdev
);
782 spin_unlock(&swap_lock
);
785 if (bdev
== sis
->bdev
) {
786 struct swap_extent
*se
= &sis
->first_swap_extent
;
788 if (se
->start_block
== offset
) {
790 *bdev_p
= bdgrab(sis
->bdev
);
792 spin_unlock(&swap_lock
);
798 spin_unlock(&swap_lock
);
806 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
807 * corresponding to given index in swap_info (swap type).
809 sector_t
swapdev_block(int type
, pgoff_t offset
)
811 struct block_device
*bdev
;
813 if ((unsigned int)type
>= nr_swapfiles
)
815 if (!(swap_info
[type
]->flags
& SWP_WRITEOK
))
817 return map_swap_entry(swp_entry(type
, offset
), &bdev
);
821 * Return either the total number of swap pages of given type, or the number
822 * of free pages of that type (depending on @free)
824 * This is needed for software suspend
826 unsigned int count_swap_pages(int type
, int free
)
830 spin_lock(&swap_lock
);
831 if ((unsigned int)type
< nr_swapfiles
) {
832 struct swap_info_struct
*sis
= swap_info
[type
];
834 if (sis
->flags
& SWP_WRITEOK
) {
837 n
-= sis
->inuse_pages
;
840 spin_unlock(&swap_lock
);
843 #endif /* CONFIG_HIBERNATION */
846 * No need to decide whether this PTE shares the swap entry with others,
847 * just let do_wp_page work it out if a write is requested later - to
848 * force COW, vm_page_prot omits write permission from any private vma.
850 static int unuse_pte(struct vm_area_struct
*vma
, pmd_t
*pmd
,
851 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
853 struct mem_cgroup
*ptr
;
858 if (mem_cgroup_try_charge_swapin(vma
->vm_mm
, page
, GFP_KERNEL
, &ptr
)) {
863 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
864 if (unlikely(!pte_same(*pte
, swp_entry_to_pte(entry
)))) {
866 mem_cgroup_cancel_charge_swapin(ptr
);
871 dec_mm_counter(vma
->vm_mm
, MM_SWAPENTS
);
872 inc_mm_counter(vma
->vm_mm
, MM_ANONPAGES
);
874 set_pte_at(vma
->vm_mm
, addr
, pte
,
875 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
876 page_add_anon_rmap(page
, vma
, addr
);
877 mem_cgroup_commit_charge_swapin(page
, ptr
);
880 * Move the page to the active list so it is not
881 * immediately swapped out again after swapon.
885 pte_unmap_unlock(pte
, ptl
);
890 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
891 unsigned long addr
, unsigned long end
,
892 swp_entry_t entry
, struct page
*page
)
894 pte_t swp_pte
= swp_entry_to_pte(entry
);
899 * We don't actually need pte lock while scanning for swp_pte: since
900 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
901 * page table while we're scanning; though it could get zapped, and on
902 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
903 * of unmatched parts which look like swp_pte, so unuse_pte must
904 * recheck under pte lock. Scanning without pte lock lets it be
905 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
907 pte
= pte_offset_map(pmd
, addr
);
910 * swapoff spends a _lot_ of time in this loop!
911 * Test inline before going to call unuse_pte.
913 if (unlikely(pte_same(*pte
, swp_pte
))) {
915 ret
= unuse_pte(vma
, pmd
, addr
, entry
, page
);
918 pte
= pte_offset_map(pmd
, addr
);
920 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
926 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
927 unsigned long addr
, unsigned long end
,
928 swp_entry_t entry
, struct page
*page
)
934 pmd
= pmd_offset(pud
, addr
);
936 next
= pmd_addr_end(addr
, end
);
937 if (unlikely(pmd_trans_huge(*pmd
)))
939 if (pmd_none_or_clear_bad(pmd
))
941 ret
= unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
);
944 } while (pmd
++, addr
= next
, addr
!= end
);
948 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
949 unsigned long addr
, unsigned long end
,
950 swp_entry_t entry
, struct page
*page
)
956 pud
= pud_offset(pgd
, addr
);
958 next
= pud_addr_end(addr
, end
);
959 if (pud_none_or_clear_bad(pud
))
961 ret
= unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
);
964 } while (pud
++, addr
= next
, addr
!= end
);
968 static int unuse_vma(struct vm_area_struct
*vma
,
969 swp_entry_t entry
, struct page
*page
)
972 unsigned long addr
, end
, next
;
975 if (page_anon_vma(page
)) {
976 addr
= page_address_in_vma(page
, vma
);
980 end
= addr
+ PAGE_SIZE
;
982 addr
= vma
->vm_start
;
986 pgd
= pgd_offset(vma
->vm_mm
, addr
);
988 next
= pgd_addr_end(addr
, end
);
989 if (pgd_none_or_clear_bad(pgd
))
991 ret
= unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
);
994 } while (pgd
++, addr
= next
, addr
!= end
);
998 static int unuse_mm(struct mm_struct
*mm
,
999 swp_entry_t entry
, struct page
*page
)
1001 struct vm_area_struct
*vma
;
1004 if (!down_read_trylock(&mm
->mmap_sem
)) {
1006 * Activate page so shrink_inactive_list is unlikely to unmap
1007 * its ptes while lock is dropped, so swapoff can make progress.
1009 activate_page(page
);
1011 down_read(&mm
->mmap_sem
);
1014 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
1015 if (vma
->anon_vma
&& (ret
= unuse_vma(vma
, entry
, page
)))
1018 up_read(&mm
->mmap_sem
);
1019 return (ret
< 0)? ret
: 0;
1023 * Scan swap_map (or frontswap_map if frontswap parameter is true)
1024 * from current position to next entry still in use.
1025 * Recycle to start on reaching the end, returning 0 when empty.
1027 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
1028 unsigned int prev
, bool frontswap
)
1030 unsigned int max
= si
->max
;
1031 unsigned int i
= prev
;
1032 unsigned char count
;
1035 * No need for swap_lock here: we're just looking
1036 * for whether an entry is in use, not modifying it; false
1037 * hits are okay, and sys_swapoff() has already prevented new
1038 * allocations from this area (while holding swap_lock).
1047 * No entries in use at top of swap_map,
1048 * loop back to start and recheck there.
1055 if (frontswap_test(si
, i
))
1060 count
= si
->swap_map
[i
];
1061 if (count
&& swap_count(count
) != SWAP_MAP_BAD
)
1068 * We completely avoid races by reading each swap page in advance,
1069 * and then search for the process using it. All the necessary
1070 * page table adjustments can then be made atomically.
1072 * if the boolean frontswap is true, only unuse pages_to_unuse pages;
1073 * pages_to_unuse==0 means all pages; ignored if frontswap is false
1075 int try_to_unuse(unsigned int type
, bool frontswap
,
1076 unsigned long pages_to_unuse
)
1078 struct swap_info_struct
*si
= swap_info
[type
];
1079 struct mm_struct
*start_mm
;
1080 unsigned char *swap_map
;
1081 unsigned char swcount
;
1088 * When searching mms for an entry, a good strategy is to
1089 * start at the first mm we freed the previous entry from
1090 * (though actually we don't notice whether we or coincidence
1091 * freed the entry). Initialize this start_mm with a hold.
1093 * A simpler strategy would be to start at the last mm we
1094 * freed the previous entry from; but that would take less
1095 * advantage of mmlist ordering, which clusters forked mms
1096 * together, child after parent. If we race with dup_mmap(), we
1097 * prefer to resolve parent before child, lest we miss entries
1098 * duplicated after we scanned child: using last mm would invert
1101 start_mm
= &init_mm
;
1102 atomic_inc(&init_mm
.mm_users
);
1105 * Keep on scanning until all entries have gone. Usually,
1106 * one pass through swap_map is enough, but not necessarily:
1107 * there are races when an instance of an entry might be missed.
1109 while ((i
= find_next_to_unuse(si
, i
, frontswap
)) != 0) {
1110 if (signal_pending(current
)) {
1116 * Get a page for the entry, using the existing swap
1117 * cache page if there is one. Otherwise, get a clean
1118 * page and read the swap into it.
1120 swap_map
= &si
->swap_map
[i
];
1121 entry
= swp_entry(type
, i
);
1122 page
= read_swap_cache_async(entry
,
1123 GFP_HIGHUSER_MOVABLE
, NULL
, 0);
1126 * Either swap_duplicate() failed because entry
1127 * has been freed independently, and will not be
1128 * reused since sys_swapoff() already disabled
1129 * allocation from here, or alloc_page() failed.
1138 * Don't hold on to start_mm if it looks like exiting.
1140 if (atomic_read(&start_mm
->mm_users
) == 1) {
1142 start_mm
= &init_mm
;
1143 atomic_inc(&init_mm
.mm_users
);
1147 * Wait for and lock page. When do_swap_page races with
1148 * try_to_unuse, do_swap_page can handle the fault much
1149 * faster than try_to_unuse can locate the entry. This
1150 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1151 * defer to do_swap_page in such a case - in some tests,
1152 * do_swap_page and try_to_unuse repeatedly compete.
1154 wait_on_page_locked(page
);
1155 wait_on_page_writeback(page
);
1157 wait_on_page_writeback(page
);
1160 * Remove all references to entry.
1162 swcount
= *swap_map
;
1163 if (swap_count(swcount
) == SWAP_MAP_SHMEM
) {
1164 retval
= shmem_unuse(entry
, page
);
1165 /* page has already been unlocked and released */
1170 if (swap_count(swcount
) && start_mm
!= &init_mm
)
1171 retval
= unuse_mm(start_mm
, entry
, page
);
1173 if (swap_count(*swap_map
)) {
1174 int set_start_mm
= (*swap_map
>= swcount
);
1175 struct list_head
*p
= &start_mm
->mmlist
;
1176 struct mm_struct
*new_start_mm
= start_mm
;
1177 struct mm_struct
*prev_mm
= start_mm
;
1178 struct mm_struct
*mm
;
1180 atomic_inc(&new_start_mm
->mm_users
);
1181 atomic_inc(&prev_mm
->mm_users
);
1182 spin_lock(&mmlist_lock
);
1183 while (swap_count(*swap_map
) && !retval
&&
1184 (p
= p
->next
) != &start_mm
->mmlist
) {
1185 mm
= list_entry(p
, struct mm_struct
, mmlist
);
1186 if (!atomic_inc_not_zero(&mm
->mm_users
))
1188 spin_unlock(&mmlist_lock
);
1194 swcount
= *swap_map
;
1195 if (!swap_count(swcount
)) /* any usage ? */
1197 else if (mm
== &init_mm
)
1200 retval
= unuse_mm(mm
, entry
, page
);
1202 if (set_start_mm
&& *swap_map
< swcount
) {
1203 mmput(new_start_mm
);
1204 atomic_inc(&mm
->mm_users
);
1208 spin_lock(&mmlist_lock
);
1210 spin_unlock(&mmlist_lock
);
1213 start_mm
= new_start_mm
;
1217 page_cache_release(page
);
1222 * If a reference remains (rare), we would like to leave
1223 * the page in the swap cache; but try_to_unmap could
1224 * then re-duplicate the entry once we drop page lock,
1225 * so we might loop indefinitely; also, that page could
1226 * not be swapped out to other storage meanwhile. So:
1227 * delete from cache even if there's another reference,
1228 * after ensuring that the data has been saved to disk -
1229 * since if the reference remains (rarer), it will be
1230 * read from disk into another page. Splitting into two
1231 * pages would be incorrect if swap supported "shared
1232 * private" pages, but they are handled by tmpfs files.
1234 * Given how unuse_vma() targets one particular offset
1235 * in an anon_vma, once the anon_vma has been determined,
1236 * this splitting happens to be just what is needed to
1237 * handle where KSM pages have been swapped out: re-reading
1238 * is unnecessarily slow, but we can fix that later on.
1240 if (swap_count(*swap_map
) &&
1241 PageDirty(page
) && PageSwapCache(page
)) {
1242 struct writeback_control wbc
= {
1243 .sync_mode
= WB_SYNC_NONE
,
1246 swap_writepage(page
, &wbc
);
1248 wait_on_page_writeback(page
);
1252 * It is conceivable that a racing task removed this page from
1253 * swap cache just before we acquired the page lock at the top,
1254 * or while we dropped it in unuse_mm(). The page might even
1255 * be back in swap cache on another swap area: that we must not
1256 * delete, since it may not have been written out to swap yet.
1258 if (PageSwapCache(page
) &&
1259 likely(page_private(page
) == entry
.val
))
1260 delete_from_swap_cache(page
);
1263 * So we could skip searching mms once swap count went
1264 * to 1, we did not mark any present ptes as dirty: must
1265 * mark page dirty so shrink_page_list will preserve it.
1269 page_cache_release(page
);
1272 * Make sure that we aren't completely killing
1273 * interactive performance.
1276 if (frontswap
&& pages_to_unuse
> 0) {
1277 if (!--pages_to_unuse
)
1287 * After a successful try_to_unuse, if no swap is now in use, we know
1288 * we can empty the mmlist. swap_lock must be held on entry and exit.
1289 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1290 * added to the mmlist just after page_duplicate - before would be racy.
1292 static void drain_mmlist(void)
1294 struct list_head
*p
, *next
;
1297 for (type
= 0; type
< nr_swapfiles
; type
++)
1298 if (swap_info
[type
]->inuse_pages
)
1300 spin_lock(&mmlist_lock
);
1301 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
1303 spin_unlock(&mmlist_lock
);
1307 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1308 * corresponds to page offset for the specified swap entry.
1309 * Note that the type of this function is sector_t, but it returns page offset
1310 * into the bdev, not sector offset.
1312 static sector_t
map_swap_entry(swp_entry_t entry
, struct block_device
**bdev
)
1314 struct swap_info_struct
*sis
;
1315 struct swap_extent
*start_se
;
1316 struct swap_extent
*se
;
1319 sis
= swap_info
[swp_type(entry
)];
1322 offset
= swp_offset(entry
);
1323 start_se
= sis
->curr_swap_extent
;
1327 struct list_head
*lh
;
1329 if (se
->start_page
<= offset
&&
1330 offset
< (se
->start_page
+ se
->nr_pages
)) {
1331 return se
->start_block
+ (offset
- se
->start_page
);
1334 se
= list_entry(lh
, struct swap_extent
, list
);
1335 sis
->curr_swap_extent
= se
;
1336 BUG_ON(se
== start_se
); /* It *must* be present */
1341 * Returns the page offset into bdev for the specified page's swap entry.
1343 sector_t
map_swap_page(struct page
*page
, struct block_device
**bdev
)
1346 entry
.val
= page_private(page
);
1347 return map_swap_entry(entry
, bdev
);
1351 * Free all of a swapdev's extent information
1353 static void destroy_swap_extents(struct swap_info_struct
*sis
)
1355 while (!list_empty(&sis
->first_swap_extent
.list
)) {
1356 struct swap_extent
*se
;
1358 se
= list_entry(sis
->first_swap_extent
.list
.next
,
1359 struct swap_extent
, list
);
1360 list_del(&se
->list
);
1366 * Add a block range (and the corresponding page range) into this swapdev's
1367 * extent list. The extent list is kept sorted in page order.
1369 * This function rather assumes that it is called in ascending page order.
1372 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
1373 unsigned long nr_pages
, sector_t start_block
)
1375 struct swap_extent
*se
;
1376 struct swap_extent
*new_se
;
1377 struct list_head
*lh
;
1379 if (start_page
== 0) {
1380 se
= &sis
->first_swap_extent
;
1381 sis
->curr_swap_extent
= se
;
1383 se
->nr_pages
= nr_pages
;
1384 se
->start_block
= start_block
;
1387 lh
= sis
->first_swap_extent
.list
.prev
; /* Highest extent */
1388 se
= list_entry(lh
, struct swap_extent
, list
);
1389 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
1390 if (se
->start_block
+ se
->nr_pages
== start_block
) {
1392 se
->nr_pages
+= nr_pages
;
1398 * No merge. Insert a new extent, preserving ordering.
1400 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
1403 new_se
->start_page
= start_page
;
1404 new_se
->nr_pages
= nr_pages
;
1405 new_se
->start_block
= start_block
;
1407 list_add_tail(&new_se
->list
, &sis
->first_swap_extent
.list
);
1412 * A `swap extent' is a simple thing which maps a contiguous range of pages
1413 * onto a contiguous range of disk blocks. An ordered list of swap extents
1414 * is built at swapon time and is then used at swap_writepage/swap_readpage
1415 * time for locating where on disk a page belongs.
1417 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1418 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1419 * swap files identically.
1421 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1422 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1423 * swapfiles are handled *identically* after swapon time.
1425 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1426 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1427 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1428 * requirements, they are simply tossed out - we will never use those blocks
1431 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1432 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1433 * which will scribble on the fs.
1435 * The amount of disk space which a single swap extent represents varies.
1436 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1437 * extents in the list. To avoid much list walking, we cache the previous
1438 * search location in `curr_swap_extent', and start new searches from there.
1439 * This is extremely effective. The average number of iterations in
1440 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1442 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1444 struct inode
*inode
;
1445 unsigned blocks_per_page
;
1446 unsigned long page_no
;
1448 sector_t probe_block
;
1449 sector_t last_block
;
1450 sector_t lowest_block
= -1;
1451 sector_t highest_block
= 0;
1455 inode
= sis
->swap_file
->f_mapping
->host
;
1456 if (S_ISBLK(inode
->i_mode
)) {
1457 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1462 blkbits
= inode
->i_blkbits
;
1463 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1466 * Map all the blocks into the extent list. This code doesn't try
1471 last_block
= i_size_read(inode
) >> blkbits
;
1472 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1473 page_no
< sis
->max
) {
1474 unsigned block_in_page
;
1475 sector_t first_block
;
1477 first_block
= bmap(inode
, probe_block
);
1478 if (first_block
== 0)
1482 * It must be PAGE_SIZE aligned on-disk
1484 if (first_block
& (blocks_per_page
- 1)) {
1489 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1493 block
= bmap(inode
, probe_block
+ block_in_page
);
1496 if (block
!= first_block
+ block_in_page
) {
1503 first_block
>>= (PAGE_SHIFT
- blkbits
);
1504 if (page_no
) { /* exclude the header page */
1505 if (first_block
< lowest_block
)
1506 lowest_block
= first_block
;
1507 if (first_block
> highest_block
)
1508 highest_block
= first_block
;
1512 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1514 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1519 probe_block
+= blocks_per_page
;
1524 *span
= 1 + highest_block
- lowest_block
;
1526 page_no
= 1; /* force Empty message */
1528 sis
->pages
= page_no
- 1;
1529 sis
->highest_bit
= page_no
- 1;
1533 printk(KERN_ERR
"swapon: swapfile has holes\n");
1538 static void enable_swap_info(struct swap_info_struct
*p
, int prio
,
1539 unsigned char *swap_map
,
1540 unsigned long *frontswap_map
)
1544 spin_lock(&swap_lock
);
1548 p
->prio
= --least_priority
;
1549 p
->swap_map
= swap_map
;
1550 frontswap_map_set(p
, frontswap_map
);
1551 p
->flags
|= SWP_WRITEOK
;
1552 nr_swap_pages
+= p
->pages
;
1553 total_swap_pages
+= p
->pages
;
1555 /* insert swap space into swap_list: */
1557 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
]->next
) {
1558 if (p
->prio
>= swap_info
[i
]->prio
)
1564 swap_list
.head
= swap_list
.next
= p
->type
;
1566 swap_info
[prev
]->next
= p
->type
;
1567 frontswap_init(p
->type
);
1568 spin_unlock(&swap_lock
);
1571 SYSCALL_DEFINE1(swapoff
, const char __user
*, specialfile
)
1573 struct swap_info_struct
*p
= NULL
;
1574 unsigned char *swap_map
;
1575 struct file
*swap_file
, *victim
;
1576 struct address_space
*mapping
;
1577 struct inode
*inode
;
1583 if (!capable(CAP_SYS_ADMIN
))
1586 pathname
= getname(specialfile
);
1587 err
= PTR_ERR(pathname
);
1588 if (IS_ERR(pathname
))
1591 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1593 err
= PTR_ERR(victim
);
1597 mapping
= victim
->f_mapping
;
1599 spin_lock(&swap_lock
);
1600 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
]->next
) {
1601 p
= swap_info
[type
];
1602 if (p
->flags
& SWP_WRITEOK
) {
1603 if (p
->swap_file
->f_mapping
== mapping
)
1610 spin_unlock(&swap_lock
);
1613 if (!security_vm_enough_memory(p
->pages
))
1614 vm_unacct_memory(p
->pages
);
1617 spin_unlock(&swap_lock
);
1621 swap_list
.head
= p
->next
;
1623 swap_info
[prev
]->next
= p
->next
;
1624 if (type
== swap_list
.next
) {
1625 /* just pick something that's safe... */
1626 swap_list
.next
= swap_list
.head
;
1629 for (i
= p
->next
; i
>= 0; i
= swap_info
[i
]->next
)
1630 swap_info
[i
]->prio
= p
->prio
--;
1633 nr_swap_pages
-= p
->pages
;
1634 total_swap_pages
-= p
->pages
;
1635 p
->flags
&= ~SWP_WRITEOK
;
1636 spin_unlock(&swap_lock
);
1638 oom_score_adj
= test_set_oom_score_adj(OOM_SCORE_ADJ_MAX
);
1639 err
= try_to_unuse(type
, false, 0); /* force all pages to be unused */
1640 test_set_oom_score_adj(oom_score_adj
);
1644 * reading p->prio and p->swap_map outside the lock is
1645 * safe here because only sys_swapon and sys_swapoff
1646 * change them, and there can be no other sys_swapon or
1647 * sys_swapoff for this swap_info_struct at this point.
1649 /* re-insert swap space back into swap_list */
1650 enable_swap_info(p
, p
->prio
, p
->swap_map
, frontswap_map_get(p
));
1654 destroy_swap_extents(p
);
1655 if (p
->flags
& SWP_CONTINUED
)
1656 free_swap_count_continuations(p
);
1658 mutex_lock(&swapon_mutex
);
1659 spin_lock(&swap_lock
);
1662 /* wait for anyone still in scan_swap_map */
1663 p
->highest_bit
= 0; /* cuts scans short */
1664 while (p
->flags
>= SWP_SCANNING
) {
1665 spin_unlock(&swap_lock
);
1666 schedule_timeout_uninterruptible(1);
1667 spin_lock(&swap_lock
);
1670 swap_file
= p
->swap_file
;
1671 p
->swap_file
= NULL
;
1673 swap_map
= p
->swap_map
;
1676 frontswap_flush_area(type
);
1677 spin_unlock(&swap_lock
);
1678 mutex_unlock(&swapon_mutex
);
1680 vfree(frontswap_map_get(p
));
1681 /* Destroy swap account informatin */
1682 swap_cgroup_swapoff(type
);
1684 inode
= mapping
->host
;
1685 if (S_ISBLK(inode
->i_mode
)) {
1686 struct block_device
*bdev
= I_BDEV(inode
);
1687 set_blocksize(bdev
, p
->old_block_size
);
1688 blkdev_put(bdev
, FMODE_READ
| FMODE_WRITE
| FMODE_EXCL
);
1690 mutex_lock(&inode
->i_mutex
);
1691 inode
->i_flags
&= ~S_SWAPFILE
;
1692 mutex_unlock(&inode
->i_mutex
);
1694 filp_close(swap_file
, NULL
);
1696 atomic_inc(&proc_poll_event
);
1697 wake_up_interruptible(&proc_poll_wait
);
1700 filp_close(victim
, NULL
);
1705 #ifdef CONFIG_PROC_FS
1706 static unsigned swaps_poll(struct file
*file
, poll_table
*wait
)
1708 struct seq_file
*seq
= file
->private_data
;
1710 poll_wait(file
, &proc_poll_wait
, wait
);
1712 if (seq
->poll_event
!= atomic_read(&proc_poll_event
)) {
1713 seq
->poll_event
= atomic_read(&proc_poll_event
);
1714 return POLLIN
| POLLRDNORM
| POLLERR
| POLLPRI
;
1717 return POLLIN
| POLLRDNORM
;
1721 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1723 struct swap_info_struct
*si
;
1727 mutex_lock(&swapon_mutex
);
1730 return SEQ_START_TOKEN
;
1732 for (type
= 0; type
< nr_swapfiles
; type
++) {
1733 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1734 si
= swap_info
[type
];
1735 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1744 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1746 struct swap_info_struct
*si
= v
;
1749 if (v
== SEQ_START_TOKEN
)
1752 type
= si
->type
+ 1;
1754 for (; type
< nr_swapfiles
; type
++) {
1755 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1756 si
= swap_info
[type
];
1757 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1766 static void swap_stop(struct seq_file
*swap
, void *v
)
1768 mutex_unlock(&swapon_mutex
);
1771 static int swap_show(struct seq_file
*swap
, void *v
)
1773 struct swap_info_struct
*si
= v
;
1777 if (si
== SEQ_START_TOKEN
) {
1778 seq_puts(swap
,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1782 file
= si
->swap_file
;
1783 len
= seq_path(swap
, &file
->f_path
, " \t\n\\");
1784 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1785 len
< 40 ? 40 - len
: 1, " ",
1786 S_ISBLK(file
->f_path
.dentry
->d_inode
->i_mode
) ?
1787 "partition" : "file\t",
1788 si
->pages
<< (PAGE_SHIFT
- 10),
1789 si
->inuse_pages
<< (PAGE_SHIFT
- 10),
1794 static const struct seq_operations swaps_op
= {
1795 .start
= swap_start
,
1801 static int swaps_open(struct inode
*inode
, struct file
*file
)
1803 struct seq_file
*seq
;
1806 ret
= seq_open(file
, &swaps_op
);
1810 seq
= file
->private_data
;
1811 seq
->poll_event
= atomic_read(&proc_poll_event
);
1815 static const struct file_operations proc_swaps_operations
= {
1818 .llseek
= seq_lseek
,
1819 .release
= seq_release
,
1823 static int __init
procswaps_init(void)
1825 proc_create("swaps", 0, NULL
, &proc_swaps_operations
);
1828 __initcall(procswaps_init
);
1829 #endif /* CONFIG_PROC_FS */
1831 #ifdef MAX_SWAPFILES_CHECK
1832 static int __init
max_swapfiles_check(void)
1834 MAX_SWAPFILES_CHECK();
1837 late_initcall(max_swapfiles_check
);
1840 static struct swap_info_struct
*alloc_swap_info(void)
1842 struct swap_info_struct
*p
;
1845 p
= kzalloc(sizeof(*p
), GFP_KERNEL
);
1847 return ERR_PTR(-ENOMEM
);
1849 spin_lock(&swap_lock
);
1850 for (type
= 0; type
< nr_swapfiles
; type
++) {
1851 if (!(swap_info
[type
]->flags
& SWP_USED
))
1854 if (type
>= MAX_SWAPFILES
) {
1855 spin_unlock(&swap_lock
);
1857 return ERR_PTR(-EPERM
);
1859 if (type
>= nr_swapfiles
) {
1861 swap_info
[type
] = p
;
1863 * Write swap_info[type] before nr_swapfiles, in case a
1864 * racing procfs swap_start() or swap_next() is reading them.
1865 * (We never shrink nr_swapfiles, we never free this entry.)
1871 p
= swap_info
[type
];
1873 * Do not memset this entry: a racing procfs swap_next()
1874 * would be relying on p->type to remain valid.
1877 INIT_LIST_HEAD(&p
->first_swap_extent
.list
);
1878 p
->flags
= SWP_USED
;
1880 spin_unlock(&swap_lock
);
1885 static int claim_swapfile(struct swap_info_struct
*p
, struct inode
*inode
)
1889 if (S_ISBLK(inode
->i_mode
)) {
1890 p
->bdev
= bdgrab(I_BDEV(inode
));
1891 error
= blkdev_get(p
->bdev
,
1892 FMODE_READ
| FMODE_WRITE
| FMODE_EXCL
,
1898 p
->old_block_size
= block_size(p
->bdev
);
1899 error
= set_blocksize(p
->bdev
, PAGE_SIZE
);
1902 p
->flags
|= SWP_BLKDEV
;
1903 } else if (S_ISREG(inode
->i_mode
)) {
1904 p
->bdev
= inode
->i_sb
->s_bdev
;
1905 mutex_lock(&inode
->i_mutex
);
1906 if (IS_SWAPFILE(inode
))
1914 static unsigned long read_swap_header(struct swap_info_struct
*p
,
1915 union swap_header
*swap_header
,
1916 struct inode
*inode
)
1919 unsigned long maxpages
;
1920 unsigned long swapfilepages
;
1922 if (memcmp("SWAPSPACE2", swap_header
->magic
.magic
, 10)) {
1923 printk(KERN_ERR
"Unable to find swap-space signature\n");
1927 /* swap partition endianess hack... */
1928 if (swab32(swap_header
->info
.version
) == 1) {
1929 swab32s(&swap_header
->info
.version
);
1930 swab32s(&swap_header
->info
.last_page
);
1931 swab32s(&swap_header
->info
.nr_badpages
);
1932 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++)
1933 swab32s(&swap_header
->info
.badpages
[i
]);
1935 /* Check the swap header's sub-version */
1936 if (swap_header
->info
.version
!= 1) {
1938 "Unable to handle swap header version %d\n",
1939 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 three limiting factors: 1) the number
1950 * of bits for the swap offset in the swp_entry_t type, and
1951 * 2) the number of bits in the swap pte as defined by the
1952 * the different architectures, and 3) the number of free bits
1953 * in an exceptional radix_tree entry. In order to find the
1954 * largest possible bit mask, a swap entry with swap type 0
1955 * and swap offset ~0UL is created, encoded to a swap pte,
1956 * decoded to a swp_entry_t again, and finally the swap
1957 * offset is extracted. This will mask all the bits from
1958 * the initial ~0UL mask that can't be encoded in either
1959 * the swp_entry_t or the architecture definition of a
1960 * swap pte. Then the same is done for a radix_tree entry.
1962 maxpages
= swp_offset(pte_to_swp_entry(
1963 swp_entry_to_pte(swp_entry(0, ~0UL))));
1964 maxpages
= swp_offset(radix_to_swp_entry(
1965 swp_to_radix_entry(swp_entry(0, maxpages
)))) + 1;
1967 if (maxpages
> swap_header
->info
.last_page
) {
1968 maxpages
= swap_header
->info
.last_page
+ 1;
1969 /* p->max is an unsigned int: don't overflow it */
1970 if ((unsigned int)maxpages
== 0)
1971 maxpages
= UINT_MAX
;
1973 p
->highest_bit
= maxpages
- 1;
1977 swapfilepages
= i_size_read(inode
) >> PAGE_SHIFT
;
1978 if (swapfilepages
&& maxpages
> swapfilepages
) {
1980 "Swap area shorter than signature indicates\n");
1983 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1985 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1991 static int setup_swap_map_and_extents(struct swap_info_struct
*p
,
1992 union swap_header
*swap_header
,
1993 unsigned char *swap_map
,
1994 unsigned long maxpages
,
1998 unsigned int nr_good_pages
;
2001 nr_good_pages
= maxpages
- 1; /* omit header page */
2003 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
2004 unsigned int page_nr
= swap_header
->info
.badpages
[i
];
2005 if (page_nr
== 0 || page_nr
> swap_header
->info
.last_page
)
2007 if (page_nr
< maxpages
) {
2008 swap_map
[page_nr
] = SWAP_MAP_BAD
;
2013 if (nr_good_pages
) {
2014 swap_map
[0] = SWAP_MAP_BAD
;
2016 p
->pages
= nr_good_pages
;
2017 nr_extents
= setup_swap_extents(p
, span
);
2020 nr_good_pages
= p
->pages
;
2022 if (!nr_good_pages
) {
2023 printk(KERN_WARNING
"Empty swap-file\n");
2030 SYSCALL_DEFINE2(swapon
, const char __user
*, specialfile
, int, swap_flags
)
2032 struct swap_info_struct
*p
;
2034 struct file
*swap_file
= NULL
;
2035 struct address_space
*mapping
;
2039 union swap_header
*swap_header
;
2042 unsigned long maxpages
;
2043 unsigned char *swap_map
= NULL
;
2044 unsigned long *frontswap_map
= NULL
;
2045 struct page
*page
= NULL
;
2046 struct inode
*inode
= NULL
;
2048 if (!capable(CAP_SYS_ADMIN
))
2051 p
= alloc_swap_info();
2055 name
= getname(specialfile
);
2057 error
= PTR_ERR(name
);
2061 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
2062 if (IS_ERR(swap_file
)) {
2063 error
= PTR_ERR(swap_file
);
2068 p
->swap_file
= swap_file
;
2069 mapping
= swap_file
->f_mapping
;
2071 for (i
= 0; i
< nr_swapfiles
; i
++) {
2072 struct swap_info_struct
*q
= swap_info
[i
];
2074 if (q
== p
|| !q
->swap_file
)
2076 if (mapping
== q
->swap_file
->f_mapping
) {
2082 inode
= mapping
->host
;
2083 /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */
2084 error
= claim_swapfile(p
, inode
);
2085 if (unlikely(error
))
2089 * Read the swap header.
2091 if (!mapping
->a_ops
->readpage
) {
2095 page
= read_mapping_page(mapping
, 0, swap_file
);
2097 error
= PTR_ERR(page
);
2100 swap_header
= kmap(page
);
2102 maxpages
= read_swap_header(p
, swap_header
, inode
);
2103 if (unlikely(!maxpages
)) {
2108 /* OK, set up the swap map and apply the bad block list */
2109 swap_map
= vzalloc(maxpages
);
2115 error
= swap_cgroup_swapon(p
->type
, maxpages
);
2119 nr_extents
= setup_swap_map_and_extents(p
, swap_header
, swap_map
,
2121 if (unlikely(nr_extents
< 0)) {
2125 /* frontswap enabled? set up bit-per-page map for frontswap */
2126 if (frontswap_enabled
)
2127 frontswap_map
= vzalloc(maxpages
/ sizeof(long));
2130 if (blk_queue_nonrot(bdev_get_queue(p
->bdev
))) {
2131 p
->flags
|= SWP_SOLIDSTATE
;
2132 p
->cluster_next
= 1 + (random32() % p
->highest_bit
);
2134 if (discard_swap(p
) == 0 && (swap_flags
& SWAP_FLAG_DISCARD
))
2135 p
->flags
|= SWP_DISCARDABLE
;
2138 mutex_lock(&swapon_mutex
);
2140 if (swap_flags
& SWAP_FLAG_PREFER
)
2142 (swap_flags
& SWAP_FLAG_PRIO_MASK
) >> SWAP_FLAG_PRIO_SHIFT
;
2143 enable_swap_info(p
, prio
, swap_map
, frontswap_map
);
2145 printk(KERN_INFO
"Adding %uk swap on %s. "
2146 "Priority:%d extents:%d across:%lluk %s%s%s\n",
2147 p
->pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
2148 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10),
2149 (p
->flags
& SWP_SOLIDSTATE
) ? "SS" : "",
2150 (p
->flags
& SWP_DISCARDABLE
) ? "D" : "",
2151 (frontswap_map
) ? "FS" : "");
2153 mutex_unlock(&swapon_mutex
);
2154 atomic_inc(&proc_poll_event
);
2155 wake_up_interruptible(&proc_poll_wait
);
2157 if (S_ISREG(inode
->i_mode
))
2158 inode
->i_flags
|= S_SWAPFILE
;
2162 if (inode
&& S_ISBLK(inode
->i_mode
) && p
->bdev
) {
2163 set_blocksize(p
->bdev
, p
->old_block_size
);
2164 blkdev_put(p
->bdev
, FMODE_READ
| FMODE_WRITE
| FMODE_EXCL
);
2166 destroy_swap_extents(p
);
2167 swap_cgroup_swapoff(p
->type
);
2168 spin_lock(&swap_lock
);
2169 p
->swap_file
= NULL
;
2171 spin_unlock(&swap_lock
);
2174 if (inode
&& S_ISREG(inode
->i_mode
)) {
2175 mutex_unlock(&inode
->i_mutex
);
2178 filp_close(swap_file
, NULL
);
2181 if (page
&& !IS_ERR(page
)) {
2183 page_cache_release(page
);
2187 if (inode
&& S_ISREG(inode
->i_mode
))
2188 mutex_unlock(&inode
->i_mutex
);
2192 void si_swapinfo(struct sysinfo
*val
)
2195 unsigned long nr_to_be_unused
= 0;
2197 spin_lock(&swap_lock
);
2198 for (type
= 0; type
< nr_swapfiles
; type
++) {
2199 struct swap_info_struct
*si
= swap_info
[type
];
2201 if ((si
->flags
& SWP_USED
) && !(si
->flags
& SWP_WRITEOK
))
2202 nr_to_be_unused
+= si
->inuse_pages
;
2204 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
2205 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
2206 spin_unlock(&swap_lock
);
2210 * Verify that a swap entry is valid and increment its swap map count.
2212 * Returns error code in following case.
2214 * - swp_entry is invalid -> EINVAL
2215 * - swp_entry is migration entry -> EINVAL
2216 * - swap-cache reference is requested but there is already one. -> EEXIST
2217 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2218 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2220 static int __swap_duplicate(swp_entry_t entry
, unsigned char usage
)
2222 struct swap_info_struct
*p
;
2223 unsigned long offset
, type
;
2224 unsigned char count
;
2225 unsigned char has_cache
;
2228 if (non_swap_entry(entry
))
2231 type
= swp_type(entry
);
2232 if (type
>= nr_swapfiles
)
2234 p
= swap_info
[type
];
2235 offset
= swp_offset(entry
);
2237 spin_lock(&swap_lock
);
2238 if (unlikely(offset
>= p
->max
))
2241 count
= p
->swap_map
[offset
];
2242 has_cache
= count
& SWAP_HAS_CACHE
;
2243 count
&= ~SWAP_HAS_CACHE
;
2246 if (usage
== SWAP_HAS_CACHE
) {
2248 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2249 if (!has_cache
&& count
)
2250 has_cache
= SWAP_HAS_CACHE
;
2251 else if (has_cache
) /* someone else added cache */
2253 else /* no users remaining */
2256 } else if (count
|| has_cache
) {
2258 if ((count
& ~COUNT_CONTINUED
) < SWAP_MAP_MAX
)
2260 else if ((count
& ~COUNT_CONTINUED
) > SWAP_MAP_MAX
)
2262 else if (swap_count_continued(p
, offset
, count
))
2263 count
= COUNT_CONTINUED
;
2267 err
= -ENOENT
; /* unused swap entry */
2269 p
->swap_map
[offset
] = count
| has_cache
;
2272 spin_unlock(&swap_lock
);
2277 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
2282 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2283 * (in which case its reference count is never incremented).
2285 void swap_shmem_alloc(swp_entry_t entry
)
2287 __swap_duplicate(entry
, SWAP_MAP_SHMEM
);
2291 * Increase reference count of swap entry by 1.
2292 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2293 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2294 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2295 * might occur if a page table entry has got corrupted.
2297 int swap_duplicate(swp_entry_t entry
)
2301 while (!err
&& __swap_duplicate(entry
, 1) == -ENOMEM
)
2302 err
= add_swap_count_continuation(entry
, GFP_ATOMIC
);
2307 * @entry: swap entry for which we allocate swap cache.
2309 * Called when allocating swap cache for existing swap entry,
2310 * This can return error codes. Returns 0 at success.
2311 * -EBUSY means there is a swap cache.
2312 * Note: return code is different from swap_duplicate().
2314 int swapcache_prepare(swp_entry_t entry
)
2316 return __swap_duplicate(entry
, SWAP_HAS_CACHE
);
2320 * swap_lock prevents swap_map being freed. Don't grab an extra
2321 * reference on the swaphandle, it doesn't matter if it becomes unused.
2323 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
2325 struct swap_info_struct
*si
;
2326 int our_page_cluster
= page_cluster
;
2327 pgoff_t target
, toff
;
2331 if (!our_page_cluster
) /* no readahead */
2334 si
= swap_info
[swp_type(entry
)];
2335 target
= swp_offset(entry
);
2336 base
= (target
>> our_page_cluster
) << our_page_cluster
;
2337 end
= base
+ (1 << our_page_cluster
);
2338 if (!base
) /* first page is swap header */
2341 spin_lock(&swap_lock
);
2342 if (frontswap_test(si
, target
)) {
2343 spin_unlock(&swap_lock
);
2346 if (end
> si
->max
) /* don't go beyond end of map */
2349 /* Count contiguous allocated slots above our target */
2350 for (toff
= target
; ++toff
< end
; nr_pages
++) {
2351 /* Don't read in free or bad pages */
2352 if (!si
->swap_map
[toff
])
2354 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2356 /* Don't read in frontswap pages */
2357 if (frontswap_test(si
, toff
))
2360 /* Count contiguous allocated slots below our target */
2361 for (toff
= target
; --toff
>= base
; nr_pages
++) {
2362 /* Don't read in free or bad pages */
2363 if (!si
->swap_map
[toff
])
2365 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2367 /* Don't read in frontswap pages */
2368 if (frontswap_test(si
, toff
))
2371 spin_unlock(&swap_lock
);
2374 * Indicate starting offset, and return number of pages to get:
2375 * if only 1, say 0, since there's then no readahead to be done.
2378 return nr_pages
? ++nr_pages
: 0;
2382 * add_swap_count_continuation - called when a swap count is duplicated
2383 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2384 * page of the original vmalloc'ed swap_map, to hold the continuation count
2385 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2386 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2388 * These continuation pages are seldom referenced: the common paths all work
2389 * on the original swap_map, only referring to a continuation page when the
2390 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2392 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2393 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2394 * can be called after dropping locks.
2396 int add_swap_count_continuation(swp_entry_t entry
, gfp_t gfp_mask
)
2398 struct swap_info_struct
*si
;
2401 struct page
*list_page
;
2403 unsigned char count
;
2406 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2407 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2409 page
= alloc_page(gfp_mask
| __GFP_HIGHMEM
);
2411 si
= swap_info_get(entry
);
2414 * An acceptable race has occurred since the failing
2415 * __swap_duplicate(): the swap entry has been freed,
2416 * perhaps even the whole swap_map cleared for swapoff.
2421 offset
= swp_offset(entry
);
2422 count
= si
->swap_map
[offset
] & ~SWAP_HAS_CACHE
;
2424 if ((count
& ~COUNT_CONTINUED
) != SWAP_MAP_MAX
) {
2426 * The higher the swap count, the more likely it is that tasks
2427 * will race to add swap count continuation: we need to avoid
2428 * over-provisioning.
2434 spin_unlock(&swap_lock
);
2439 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2440 * no architecture is using highmem pages for kernel pagetables: so it
2441 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2443 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2444 offset
&= ~PAGE_MASK
;
2447 * Page allocation does not initialize the page's lru field,
2448 * but it does always reset its private field.
2450 if (!page_private(head
)) {
2451 BUG_ON(count
& COUNT_CONTINUED
);
2452 INIT_LIST_HEAD(&head
->lru
);
2453 set_page_private(head
, SWP_CONTINUED
);
2454 si
->flags
|= SWP_CONTINUED
;
2457 list_for_each_entry(list_page
, &head
->lru
, lru
) {
2461 * If the previous map said no continuation, but we've found
2462 * a continuation page, free our allocation and use this one.
2464 if (!(count
& COUNT_CONTINUED
))
2467 map
= kmap_atomic(list_page
, KM_USER0
) + offset
;
2469 kunmap_atomic(map
, KM_USER0
);
2472 * If this continuation count now has some space in it,
2473 * free our allocation and use this one.
2475 if ((count
& ~COUNT_CONTINUED
) != SWAP_CONT_MAX
)
2479 list_add_tail(&page
->lru
, &head
->lru
);
2480 page
= NULL
; /* now it's attached, don't free it */
2482 spin_unlock(&swap_lock
);
2490 * swap_count_continued - when the original swap_map count is incremented
2491 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2492 * into, carry if so, or else fail until a new continuation page is allocated;
2493 * when the original swap_map count is decremented from 0 with continuation,
2494 * borrow from the continuation and report whether it still holds more.
2495 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2497 static bool swap_count_continued(struct swap_info_struct
*si
,
2498 pgoff_t offset
, unsigned char count
)
2504 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2505 if (page_private(head
) != SWP_CONTINUED
) {
2506 BUG_ON(count
& COUNT_CONTINUED
);
2507 return false; /* need to add count continuation */
2510 offset
&= ~PAGE_MASK
;
2511 page
= list_entry(head
->lru
.next
, struct page
, lru
);
2512 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2514 if (count
== SWAP_MAP_MAX
) /* initial increment from swap_map */
2515 goto init_map
; /* jump over SWAP_CONT_MAX checks */
2517 if (count
== (SWAP_MAP_MAX
| COUNT_CONTINUED
)) { /* incrementing */
2519 * Think of how you add 1 to 999
2521 while (*map
== (SWAP_CONT_MAX
| COUNT_CONTINUED
)) {
2522 kunmap_atomic(map
, KM_USER0
);
2523 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2524 BUG_ON(page
== head
);
2525 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2527 if (*map
== SWAP_CONT_MAX
) {
2528 kunmap_atomic(map
, KM_USER0
);
2529 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2531 return false; /* add count continuation */
2532 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2533 init_map
: *map
= 0; /* we didn't zero the page */
2536 kunmap_atomic(map
, KM_USER0
);
2537 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2538 while (page
!= head
) {
2539 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2540 *map
= COUNT_CONTINUED
;
2541 kunmap_atomic(map
, KM_USER0
);
2542 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2544 return true; /* incremented */
2546 } else { /* decrementing */
2548 * Think of how you subtract 1 from 1000
2550 BUG_ON(count
!= COUNT_CONTINUED
);
2551 while (*map
== COUNT_CONTINUED
) {
2552 kunmap_atomic(map
, KM_USER0
);
2553 page
= list_entry(page
->lru
.next
, struct page
, lru
);
2554 BUG_ON(page
== head
);
2555 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2561 kunmap_atomic(map
, KM_USER0
);
2562 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2563 while (page
!= head
) {
2564 map
= kmap_atomic(page
, KM_USER0
) + offset
;
2565 *map
= SWAP_CONT_MAX
| count
;
2566 count
= COUNT_CONTINUED
;
2567 kunmap_atomic(map
, KM_USER0
);
2568 page
= list_entry(page
->lru
.prev
, struct page
, lru
);
2570 return count
== COUNT_CONTINUED
;
2575 * free_swap_count_continuations - swapoff free all the continuation pages
2576 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2578 static void free_swap_count_continuations(struct swap_info_struct
*si
)
2582 for (offset
= 0; offset
< si
->max
; offset
+= PAGE_SIZE
) {
2584 head
= vmalloc_to_page(si
->swap_map
+ offset
);
2585 if (page_private(head
)) {
2586 struct list_head
*this, *next
;
2587 list_for_each_safe(this, next
, &head
->lru
) {
2589 page
= list_entry(this, struct page
, lru
);