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/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>
33 #include <asm/pgtable.h>
34 #include <asm/tlbflush.h>
35 #include <linux/swapops.h>
36 #include <linux/page_cgroup.h>
38 static DEFINE_SPINLOCK(swap_lock
);
39 static unsigned int nr_swapfiles
;
41 long total_swap_pages
;
42 static int swap_overflow
;
43 static int least_priority
;
45 static const char Bad_file
[] = "Bad swap file entry ";
46 static const char Unused_file
[] = "Unused swap file entry ";
47 static const char Bad_offset
[] = "Bad swap offset entry ";
48 static const char Unused_offset
[] = "Unused swap offset entry ";
50 static struct swap_list_t swap_list
= {-1, -1};
52 static struct swap_info_struct
*swap_info
[MAX_SWAPFILES
];
54 static DEFINE_MUTEX(swapon_mutex
);
56 /* For reference count accounting in swap_map */
57 /* enum for swap_map[] handling. internal use only */
59 SWAP_MAP
= 0, /* ops for reference from swap users */
60 SWAP_CACHE
, /* ops for reference from swap cache */
63 static inline int swap_count(unsigned short ent
)
65 return ent
& SWAP_COUNT_MASK
;
68 static inline bool swap_has_cache(unsigned short ent
)
70 return !!(ent
& SWAP_HAS_CACHE
);
73 static inline unsigned short encode_swapmap(int count
, bool has_cache
)
75 unsigned short ret
= count
;
78 return SWAP_HAS_CACHE
| ret
;
82 /* returns 1 if swap entry is freed */
84 __try_to_reclaim_swap(struct swap_info_struct
*si
, unsigned long offset
)
86 swp_entry_t entry
= swp_entry(si
->type
, offset
);
90 page
= find_get_page(&swapper_space
, entry
.val
);
94 * This function is called from scan_swap_map() and it's called
95 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
96 * We have to use trylock for avoiding deadlock. This is a special
97 * case and you should use try_to_free_swap() with explicit lock_page()
98 * in usual operations.
100 if (trylock_page(page
)) {
101 ret
= try_to_free_swap(page
);
104 page_cache_release(page
);
109 * We need this because the bdev->unplug_fn can sleep and we cannot
110 * hold swap_lock while calling the unplug_fn. And swap_lock
111 * cannot be turned into a mutex.
113 static DECLARE_RWSEM(swap_unplug_sem
);
115 void swap_unplug_io_fn(struct backing_dev_info
*unused_bdi
, struct page
*page
)
119 down_read(&swap_unplug_sem
);
120 entry
.val
= page_private(page
);
121 if (PageSwapCache(page
)) {
122 struct block_device
*bdev
= swap_info
[swp_type(entry
)]->bdev
;
123 struct backing_dev_info
*bdi
;
126 * If the page is removed from swapcache from under us (with a
127 * racy try_to_unuse/swapoff) we need an additional reference
128 * count to avoid reading garbage from page_private(page) above.
129 * If the WARN_ON triggers during a swapoff it maybe the race
130 * condition and it's harmless. However if it triggers without
131 * swapoff it signals a problem.
133 WARN_ON(page_count(page
) <= 1);
135 bdi
= bdev
->bd_inode
->i_mapping
->backing_dev_info
;
136 blk_run_backing_dev(bdi
, page
);
138 up_read(&swap_unplug_sem
);
142 * swapon tell device that all the old swap contents can be discarded,
143 * to allow the swap device to optimize its wear-levelling.
145 static int discard_swap(struct swap_info_struct
*si
)
147 struct swap_extent
*se
;
150 list_for_each_entry(se
, &si
->extent_list
, list
) {
151 sector_t start_block
= se
->start_block
<< (PAGE_SHIFT
- 9);
152 sector_t nr_blocks
= (sector_t
)se
->nr_pages
<< (PAGE_SHIFT
- 9);
154 if (se
->start_page
== 0) {
155 /* Do not discard the swap header page! */
156 start_block
+= 1 << (PAGE_SHIFT
- 9);
157 nr_blocks
-= 1 << (PAGE_SHIFT
- 9);
162 err
= blkdev_issue_discard(si
->bdev
, start_block
,
163 nr_blocks
, GFP_KERNEL
,
170 return err
; /* That will often be -EOPNOTSUPP */
174 * swap allocation tell device that a cluster of swap can now be discarded,
175 * to allow the swap device to optimize its wear-levelling.
177 static void discard_swap_cluster(struct swap_info_struct
*si
,
178 pgoff_t start_page
, pgoff_t nr_pages
)
180 struct swap_extent
*se
= si
->curr_swap_extent
;
181 int found_extent
= 0;
184 struct list_head
*lh
;
186 if (se
->start_page
<= start_page
&&
187 start_page
< se
->start_page
+ se
->nr_pages
) {
188 pgoff_t offset
= start_page
- se
->start_page
;
189 sector_t start_block
= se
->start_block
+ offset
;
190 sector_t nr_blocks
= se
->nr_pages
- offset
;
192 if (nr_blocks
> nr_pages
)
193 nr_blocks
= nr_pages
;
194 start_page
+= nr_blocks
;
195 nr_pages
-= nr_blocks
;
198 si
->curr_swap_extent
= se
;
200 start_block
<<= PAGE_SHIFT
- 9;
201 nr_blocks
<<= PAGE_SHIFT
- 9;
202 if (blkdev_issue_discard(si
->bdev
, start_block
,
209 if (lh
== &si
->extent_list
)
211 se
= list_entry(lh
, struct swap_extent
, list
);
215 static int wait_for_discard(void *word
)
221 #define SWAPFILE_CLUSTER 256
222 #define LATENCY_LIMIT 256
224 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
,
227 unsigned long offset
;
228 unsigned long scan_base
;
229 unsigned long last_in_cluster
= 0;
230 int latency_ration
= LATENCY_LIMIT
;
231 int found_free_cluster
= 0;
234 * We try to cluster swap pages by allocating them sequentially
235 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
236 * way, however, we resort to first-free allocation, starting
237 * a new cluster. This prevents us from scattering swap pages
238 * all over the entire swap partition, so that we reduce
239 * overall disk seek times between swap pages. -- sct
240 * But we do now try to find an empty cluster. -Andrea
241 * And we let swap pages go all over an SSD partition. Hugh
244 si
->flags
+= SWP_SCANNING
;
245 scan_base
= offset
= si
->cluster_next
;
247 if (unlikely(!si
->cluster_nr
--)) {
248 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
) {
249 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
252 if (si
->flags
& SWP_DISCARDABLE
) {
254 * Start range check on racing allocations, in case
255 * they overlap the cluster we eventually decide on
256 * (we scan without swap_lock to allow preemption).
257 * It's hardly conceivable that cluster_nr could be
258 * wrapped during our scan, but don't depend on it.
260 if (si
->lowest_alloc
)
262 si
->lowest_alloc
= si
->max
;
263 si
->highest_alloc
= 0;
265 spin_unlock(&swap_lock
);
268 * If seek is expensive, start searching for new cluster from
269 * start of partition, to minimize the span of allocated swap.
270 * But if seek is cheap, search from our current position, so
271 * that swap is allocated from all over the partition: if the
272 * Flash Translation Layer only remaps within limited zones,
273 * we don't want to wear out the first zone too quickly.
275 if (!(si
->flags
& SWP_SOLIDSTATE
))
276 scan_base
= offset
= si
->lowest_bit
;
277 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
279 /* Locate the first empty (unaligned) cluster */
280 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
281 if (si
->swap_map
[offset
])
282 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
283 else if (offset
== last_in_cluster
) {
284 spin_lock(&swap_lock
);
285 offset
-= SWAPFILE_CLUSTER
- 1;
286 si
->cluster_next
= offset
;
287 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
288 found_free_cluster
= 1;
291 if (unlikely(--latency_ration
< 0)) {
293 latency_ration
= LATENCY_LIMIT
;
297 offset
= si
->lowest_bit
;
298 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
300 /* Locate the first empty (unaligned) cluster */
301 for (; last_in_cluster
< scan_base
; offset
++) {
302 if (si
->swap_map
[offset
])
303 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
304 else if (offset
== last_in_cluster
) {
305 spin_lock(&swap_lock
);
306 offset
-= SWAPFILE_CLUSTER
- 1;
307 si
->cluster_next
= offset
;
308 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
309 found_free_cluster
= 1;
312 if (unlikely(--latency_ration
< 0)) {
314 latency_ration
= LATENCY_LIMIT
;
319 spin_lock(&swap_lock
);
320 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
321 si
->lowest_alloc
= 0;
325 if (!(si
->flags
& SWP_WRITEOK
))
327 if (!si
->highest_bit
)
329 if (offset
> si
->highest_bit
)
330 scan_base
= offset
= si
->lowest_bit
;
332 /* reuse swap entry of cache-only swap if not busy. */
333 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
335 spin_unlock(&swap_lock
);
336 swap_was_freed
= __try_to_reclaim_swap(si
, offset
);
337 spin_lock(&swap_lock
);
338 /* entry was freed successfully, try to use this again */
341 goto scan
; /* check next one */
344 if (si
->swap_map
[offset
])
347 if (offset
== si
->lowest_bit
)
349 if (offset
== si
->highest_bit
)
352 if (si
->inuse_pages
== si
->pages
) {
353 si
->lowest_bit
= si
->max
;
356 if (cache
== SWAP_CACHE
) /* at usual swap-out via vmscan.c */
357 si
->swap_map
[offset
] = encode_swapmap(0, true);
358 else /* at suspend */
359 si
->swap_map
[offset
] = encode_swapmap(1, false);
360 si
->cluster_next
= offset
+ 1;
361 si
->flags
-= SWP_SCANNING
;
363 if (si
->lowest_alloc
) {
365 * Only set when SWP_DISCARDABLE, and there's a scan
366 * for a free cluster in progress or just completed.
368 if (found_free_cluster
) {
370 * To optimize wear-levelling, discard the
371 * old data of the cluster, taking care not to
372 * discard any of its pages that have already
373 * been allocated by racing tasks (offset has
374 * already stepped over any at the beginning).
376 if (offset
< si
->highest_alloc
&&
377 si
->lowest_alloc
<= last_in_cluster
)
378 last_in_cluster
= si
->lowest_alloc
- 1;
379 si
->flags
|= SWP_DISCARDING
;
380 spin_unlock(&swap_lock
);
382 if (offset
< last_in_cluster
)
383 discard_swap_cluster(si
, offset
,
384 last_in_cluster
- offset
+ 1);
386 spin_lock(&swap_lock
);
387 si
->lowest_alloc
= 0;
388 si
->flags
&= ~SWP_DISCARDING
;
390 smp_mb(); /* wake_up_bit advises this */
391 wake_up_bit(&si
->flags
, ilog2(SWP_DISCARDING
));
393 } else if (si
->flags
& SWP_DISCARDING
) {
395 * Delay using pages allocated by racing tasks
396 * until the whole discard has been issued. We
397 * could defer that delay until swap_writepage,
398 * but it's easier to keep this self-contained.
400 spin_unlock(&swap_lock
);
401 wait_on_bit(&si
->flags
, ilog2(SWP_DISCARDING
),
402 wait_for_discard
, TASK_UNINTERRUPTIBLE
);
403 spin_lock(&swap_lock
);
406 * Note pages allocated by racing tasks while
407 * scan for a free cluster is in progress, so
408 * that its final discard can exclude them.
410 if (offset
< si
->lowest_alloc
)
411 si
->lowest_alloc
= offset
;
412 if (offset
> si
->highest_alloc
)
413 si
->highest_alloc
= offset
;
419 spin_unlock(&swap_lock
);
420 while (++offset
<= si
->highest_bit
) {
421 if (!si
->swap_map
[offset
]) {
422 spin_lock(&swap_lock
);
425 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
426 spin_lock(&swap_lock
);
429 if (unlikely(--latency_ration
< 0)) {
431 latency_ration
= LATENCY_LIMIT
;
434 offset
= si
->lowest_bit
;
435 while (++offset
< scan_base
) {
436 if (!si
->swap_map
[offset
]) {
437 spin_lock(&swap_lock
);
440 if (vm_swap_full() && si
->swap_map
[offset
] == SWAP_HAS_CACHE
) {
441 spin_lock(&swap_lock
);
444 if (unlikely(--latency_ration
< 0)) {
446 latency_ration
= LATENCY_LIMIT
;
449 spin_lock(&swap_lock
);
452 si
->flags
-= SWP_SCANNING
;
456 swp_entry_t
get_swap_page(void)
458 struct swap_info_struct
*si
;
463 spin_lock(&swap_lock
);
464 if (nr_swap_pages
<= 0)
468 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
469 si
= swap_info
[type
];
472 (!wrapped
&& si
->prio
!= swap_info
[next
]->prio
)) {
473 next
= swap_list
.head
;
477 if (!si
->highest_bit
)
479 if (!(si
->flags
& SWP_WRITEOK
))
482 swap_list
.next
= next
;
483 /* This is called for allocating swap entry for cache */
484 offset
= scan_swap_map(si
, SWAP_CACHE
);
486 spin_unlock(&swap_lock
);
487 return swp_entry(type
, offset
);
489 next
= swap_list
.next
;
494 spin_unlock(&swap_lock
);
495 return (swp_entry_t
) {0};
498 /* The only caller of this function is now susupend routine */
499 swp_entry_t
get_swap_page_of_type(int type
)
501 struct swap_info_struct
*si
;
504 spin_lock(&swap_lock
);
505 si
= swap_info
[type
];
506 if (si
&& (si
->flags
& SWP_WRITEOK
)) {
508 /* This is called for allocating swap entry, not cache */
509 offset
= scan_swap_map(si
, SWAP_MAP
);
511 spin_unlock(&swap_lock
);
512 return swp_entry(type
, offset
);
516 spin_unlock(&swap_lock
);
517 return (swp_entry_t
) {0};
520 static struct swap_info_struct
* swap_info_get(swp_entry_t entry
)
522 struct swap_info_struct
* p
;
523 unsigned long offset
, type
;
527 type
= swp_type(entry
);
528 if (type
>= nr_swapfiles
)
531 if (!(p
->flags
& SWP_USED
))
533 offset
= swp_offset(entry
);
534 if (offset
>= p
->max
)
536 if (!p
->swap_map
[offset
])
538 spin_lock(&swap_lock
);
542 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
545 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
548 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
551 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
556 static int swap_entry_free(struct swap_info_struct
*p
,
557 swp_entry_t ent
, int cache
)
559 unsigned long offset
= swp_offset(ent
);
560 int count
= swap_count(p
->swap_map
[offset
]);
563 has_cache
= swap_has_cache(p
->swap_map
[offset
]);
565 if (cache
== SWAP_MAP
) { /* dropping usage count of swap */
566 if (count
< SWAP_MAP_MAX
) {
568 p
->swap_map
[offset
] = encode_swapmap(count
, has_cache
);
570 } else { /* dropping swap cache flag */
571 VM_BUG_ON(!has_cache
);
572 p
->swap_map
[offset
] = encode_swapmap(count
, false);
576 count
= p
->swap_map
[offset
];
577 /* free if no reference */
579 if (offset
< p
->lowest_bit
)
580 p
->lowest_bit
= offset
;
581 if (offset
> p
->highest_bit
)
582 p
->highest_bit
= offset
;
583 if (swap_list
.next
>= 0 &&
584 p
->prio
> swap_info
[swap_list
.next
]->prio
)
585 swap_list
.next
= p
->type
;
589 if (!swap_count(count
))
590 mem_cgroup_uncharge_swap(ent
);
595 * Caller has made sure that the swapdevice corresponding to entry
596 * is still around or has not been recycled.
598 void swap_free(swp_entry_t entry
)
600 struct swap_info_struct
* p
;
602 p
= swap_info_get(entry
);
604 swap_entry_free(p
, entry
, SWAP_MAP
);
605 spin_unlock(&swap_lock
);
610 * Called after dropping swapcache to decrease refcnt to swap entries.
612 void swapcache_free(swp_entry_t entry
, struct page
*page
)
614 struct swap_info_struct
*p
;
617 p
= swap_info_get(entry
);
619 ret
= swap_entry_free(p
, entry
, SWAP_CACHE
);
623 swapout
= true; /* the end of swap out */
625 swapout
= false; /* no more swap users! */
626 mem_cgroup_uncharge_swapcache(page
, entry
, swapout
);
628 spin_unlock(&swap_lock
);
634 * How many references to page are currently swapped out?
636 static inline int page_swapcount(struct page
*page
)
639 struct swap_info_struct
*p
;
642 entry
.val
= page_private(page
);
643 p
= swap_info_get(entry
);
645 count
= swap_count(p
->swap_map
[swp_offset(entry
)]);
646 spin_unlock(&swap_lock
);
652 * We can write to an anon page without COW if there are no other references
653 * to it. And as a side-effect, free up its swap: because the old content
654 * on disk will never be read, and seeking back there to write new content
655 * later would only waste time away from clustering.
657 int reuse_swap_page(struct page
*page
)
661 VM_BUG_ON(!PageLocked(page
));
662 count
= page_mapcount(page
);
663 if (count
<= 1 && PageSwapCache(page
)) {
664 count
+= page_swapcount(page
);
665 if (count
== 1 && !PageWriteback(page
)) {
666 delete_from_swap_cache(page
);
674 * If swap is getting full, or if there are no more mappings of this page,
675 * then try_to_free_swap is called to free its swap space.
677 int try_to_free_swap(struct page
*page
)
679 VM_BUG_ON(!PageLocked(page
));
681 if (!PageSwapCache(page
))
683 if (PageWriteback(page
))
685 if (page_swapcount(page
))
688 delete_from_swap_cache(page
);
694 * Free the swap entry like above, but also try to
695 * free the page cache entry if it is the last user.
697 int free_swap_and_cache(swp_entry_t entry
)
699 struct swap_info_struct
*p
;
700 struct page
*page
= NULL
;
702 if (non_swap_entry(entry
))
705 p
= swap_info_get(entry
);
707 if (swap_entry_free(p
, entry
, SWAP_MAP
) == SWAP_HAS_CACHE
) {
708 page
= find_get_page(&swapper_space
, entry
.val
);
709 if (page
&& !trylock_page(page
)) {
710 page_cache_release(page
);
714 spin_unlock(&swap_lock
);
718 * Not mapped elsewhere, or swap space full? Free it!
719 * Also recheck PageSwapCache now page is locked (above).
721 if (PageSwapCache(page
) && !PageWriteback(page
) &&
722 (!page_mapped(page
) || vm_swap_full())) {
723 delete_from_swap_cache(page
);
727 page_cache_release(page
);
732 #ifdef CONFIG_HIBERNATION
734 * Find the swap type that corresponds to given device (if any).
736 * @offset - number of the PAGE_SIZE-sized block of the device, starting
737 * from 0, in which the swap header is expected to be located.
739 * This is needed for the suspend to disk (aka swsusp).
741 int swap_type_of(dev_t device
, sector_t offset
, struct block_device
**bdev_p
)
743 struct block_device
*bdev
= NULL
;
747 bdev
= bdget(device
);
749 spin_lock(&swap_lock
);
750 for (type
= 0; type
< nr_swapfiles
; type
++) {
751 struct swap_info_struct
*sis
= swap_info
[type
];
753 if (!(sis
->flags
& SWP_WRITEOK
))
758 *bdev_p
= bdgrab(sis
->bdev
);
760 spin_unlock(&swap_lock
);
763 if (bdev
== sis
->bdev
) {
764 struct swap_extent
*se
;
766 se
= list_entry(sis
->extent_list
.next
,
767 struct swap_extent
, list
);
768 if (se
->start_block
== offset
) {
770 *bdev_p
= bdgrab(sis
->bdev
);
772 spin_unlock(&swap_lock
);
778 spin_unlock(&swap_lock
);
786 * Return either the total number of swap pages of given type, or the number
787 * of free pages of that type (depending on @free)
789 * This is needed for software suspend
791 unsigned int count_swap_pages(int type
, int free
)
795 spin_lock(&swap_lock
);
796 if ((unsigned int)type
< nr_swapfiles
) {
797 struct swap_info_struct
*sis
= swap_info
[type
];
799 if (sis
->flags
& SWP_WRITEOK
) {
802 n
-= sis
->inuse_pages
;
805 spin_unlock(&swap_lock
);
811 * No need to decide whether this PTE shares the swap entry with others,
812 * just let do_wp_page work it out if a write is requested later - to
813 * force COW, vm_page_prot omits write permission from any private vma.
815 static int unuse_pte(struct vm_area_struct
*vma
, pmd_t
*pmd
,
816 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
818 struct mem_cgroup
*ptr
= NULL
;
823 if (mem_cgroup_try_charge_swapin(vma
->vm_mm
, page
, GFP_KERNEL
, &ptr
)) {
828 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
829 if (unlikely(!pte_same(*pte
, swp_entry_to_pte(entry
)))) {
831 mem_cgroup_cancel_charge_swapin(ptr
);
836 inc_mm_counter(vma
->vm_mm
, anon_rss
);
838 set_pte_at(vma
->vm_mm
, addr
, pte
,
839 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
840 page_add_anon_rmap(page
, vma
, addr
);
841 mem_cgroup_commit_charge_swapin(page
, ptr
);
844 * Move the page to the active list so it is not
845 * immediately swapped out again after swapon.
849 pte_unmap_unlock(pte
, ptl
);
854 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
855 unsigned long addr
, unsigned long end
,
856 swp_entry_t entry
, struct page
*page
)
858 pte_t swp_pte
= swp_entry_to_pte(entry
);
863 * We don't actually need pte lock while scanning for swp_pte: since
864 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
865 * page table while we're scanning; though it could get zapped, and on
866 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
867 * of unmatched parts which look like swp_pte, so unuse_pte must
868 * recheck under pte lock. Scanning without pte lock lets it be
869 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
871 pte
= pte_offset_map(pmd
, addr
);
874 * swapoff spends a _lot_ of time in this loop!
875 * Test inline before going to call unuse_pte.
877 if (unlikely(pte_same(*pte
, swp_pte
))) {
879 ret
= unuse_pte(vma
, pmd
, addr
, entry
, page
);
882 pte
= pte_offset_map(pmd
, addr
);
884 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
890 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
891 unsigned long addr
, unsigned long end
,
892 swp_entry_t entry
, struct page
*page
)
898 pmd
= pmd_offset(pud
, addr
);
900 next
= pmd_addr_end(addr
, end
);
901 if (pmd_none_or_clear_bad(pmd
))
903 ret
= unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
);
906 } while (pmd
++, addr
= next
, addr
!= end
);
910 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
911 unsigned long addr
, unsigned long end
,
912 swp_entry_t entry
, struct page
*page
)
918 pud
= pud_offset(pgd
, addr
);
920 next
= pud_addr_end(addr
, end
);
921 if (pud_none_or_clear_bad(pud
))
923 ret
= unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
);
926 } while (pud
++, addr
= next
, addr
!= end
);
930 static int unuse_vma(struct vm_area_struct
*vma
,
931 swp_entry_t entry
, struct page
*page
)
934 unsigned long addr
, end
, next
;
938 addr
= page_address_in_vma(page
, vma
);
942 end
= addr
+ PAGE_SIZE
;
944 addr
= vma
->vm_start
;
948 pgd
= pgd_offset(vma
->vm_mm
, addr
);
950 next
= pgd_addr_end(addr
, end
);
951 if (pgd_none_or_clear_bad(pgd
))
953 ret
= unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
);
956 } while (pgd
++, addr
= next
, addr
!= end
);
960 static int unuse_mm(struct mm_struct
*mm
,
961 swp_entry_t entry
, struct page
*page
)
963 struct vm_area_struct
*vma
;
966 if (!down_read_trylock(&mm
->mmap_sem
)) {
968 * Activate page so shrink_inactive_list is unlikely to unmap
969 * its ptes while lock is dropped, so swapoff can make progress.
973 down_read(&mm
->mmap_sem
);
976 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
977 if (vma
->anon_vma
&& (ret
= unuse_vma(vma
, entry
, page
)))
980 up_read(&mm
->mmap_sem
);
981 return (ret
< 0)? ret
: 0;
985 * Scan swap_map from current position to next entry still in use.
986 * Recycle to start on reaching the end, returning 0 when empty.
988 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
991 unsigned int max
= si
->max
;
992 unsigned int i
= prev
;
996 * No need for swap_lock here: we're just looking
997 * for whether an entry is in use, not modifying it; false
998 * hits are okay, and sys_swapoff() has already prevented new
999 * allocations from this area (while holding swap_lock).
1008 * No entries in use at top of swap_map,
1009 * loop back to start and recheck there.
1015 count
= si
->swap_map
[i
];
1016 if (count
&& swap_count(count
) != SWAP_MAP_BAD
)
1023 * We completely avoid races by reading each swap page in advance,
1024 * and then search for the process using it. All the necessary
1025 * page table adjustments can then be made atomically.
1027 static int try_to_unuse(unsigned int type
)
1029 struct swap_info_struct
*si
= swap_info
[type
];
1030 struct mm_struct
*start_mm
;
1031 unsigned short *swap_map
;
1032 unsigned short swcount
;
1037 int reset_overflow
= 0;
1041 * When searching mms for an entry, a good strategy is to
1042 * start at the first mm we freed the previous entry from
1043 * (though actually we don't notice whether we or coincidence
1044 * freed the entry). Initialize this start_mm with a hold.
1046 * A simpler strategy would be to start at the last mm we
1047 * freed the previous entry from; but that would take less
1048 * advantage of mmlist ordering, which clusters forked mms
1049 * together, child after parent. If we race with dup_mmap(), we
1050 * prefer to resolve parent before child, lest we miss entries
1051 * duplicated after we scanned child: using last mm would invert
1052 * that. Though it's only a serious concern when an overflowed
1053 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
1055 start_mm
= &init_mm
;
1056 atomic_inc(&init_mm
.mm_users
);
1059 * Keep on scanning until all entries have gone. Usually,
1060 * one pass through swap_map is enough, but not necessarily:
1061 * there are races when an instance of an entry might be missed.
1063 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
1064 if (signal_pending(current
)) {
1070 * Get a page for the entry, using the existing swap
1071 * cache page if there is one. Otherwise, get a clean
1072 * page and read the swap into it.
1074 swap_map
= &si
->swap_map
[i
];
1075 entry
= swp_entry(type
, i
);
1076 page
= read_swap_cache_async(entry
,
1077 GFP_HIGHUSER_MOVABLE
, NULL
, 0);
1080 * Either swap_duplicate() failed because entry
1081 * has been freed independently, and will not be
1082 * reused since sys_swapoff() already disabled
1083 * allocation from here, or alloc_page() failed.
1092 * Don't hold on to start_mm if it looks like exiting.
1094 if (atomic_read(&start_mm
->mm_users
) == 1) {
1096 start_mm
= &init_mm
;
1097 atomic_inc(&init_mm
.mm_users
);
1101 * Wait for and lock page. When do_swap_page races with
1102 * try_to_unuse, do_swap_page can handle the fault much
1103 * faster than try_to_unuse can locate the entry. This
1104 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1105 * defer to do_swap_page in such a case - in some tests,
1106 * do_swap_page and try_to_unuse repeatedly compete.
1108 wait_on_page_locked(page
);
1109 wait_on_page_writeback(page
);
1111 wait_on_page_writeback(page
);
1114 * Remove all references to entry.
1115 * Whenever we reach init_mm, there's no address space
1116 * to search, but use it as a reminder to search shmem.
1119 swcount
= *swap_map
;
1120 if (swap_count(swcount
)) {
1121 if (start_mm
== &init_mm
)
1122 shmem
= shmem_unuse(entry
, page
);
1124 retval
= unuse_mm(start_mm
, entry
, page
);
1126 if (swap_count(*swap_map
)) {
1127 int set_start_mm
= (*swap_map
>= swcount
);
1128 struct list_head
*p
= &start_mm
->mmlist
;
1129 struct mm_struct
*new_start_mm
= start_mm
;
1130 struct mm_struct
*prev_mm
= start_mm
;
1131 struct mm_struct
*mm
;
1133 atomic_inc(&new_start_mm
->mm_users
);
1134 atomic_inc(&prev_mm
->mm_users
);
1135 spin_lock(&mmlist_lock
);
1136 while (swap_count(*swap_map
) && !retval
&& !shmem
&&
1137 (p
= p
->next
) != &start_mm
->mmlist
) {
1138 mm
= list_entry(p
, struct mm_struct
, mmlist
);
1139 if (!atomic_inc_not_zero(&mm
->mm_users
))
1141 spin_unlock(&mmlist_lock
);
1147 swcount
= *swap_map
;
1148 if (!swap_count(swcount
)) /* any usage ? */
1150 else if (mm
== &init_mm
) {
1152 shmem
= shmem_unuse(entry
, page
);
1154 retval
= unuse_mm(mm
, entry
, page
);
1156 if (set_start_mm
&& *swap_map
< swcount
) {
1157 mmput(new_start_mm
);
1158 atomic_inc(&mm
->mm_users
);
1162 spin_lock(&mmlist_lock
);
1164 spin_unlock(&mmlist_lock
);
1167 start_mm
= new_start_mm
;
1170 /* page has already been unlocked and released */
1178 page_cache_release(page
);
1183 * How could swap count reach 0x7ffe ?
1184 * There's no way to repeat a swap page within an mm
1185 * (except in shmem, where it's the shared object which takes
1186 * the reference count)?
1187 * We believe SWAP_MAP_MAX cannot occur.(if occur, unsigned
1188 * short is too small....)
1189 * If that's wrong, then we should worry more about
1190 * exit_mmap() and do_munmap() cases described above:
1191 * we might be resetting SWAP_MAP_MAX too early here.
1192 * We know "Undead"s can happen, they're okay, so don't
1193 * report them; but do report if we reset SWAP_MAP_MAX.
1195 /* We might release the lock_page() in unuse_mm(). */
1196 if (!PageSwapCache(page
) || page_private(page
) != entry
.val
)
1199 if (swap_count(*swap_map
) == SWAP_MAP_MAX
) {
1200 spin_lock(&swap_lock
);
1201 *swap_map
= encode_swapmap(0, true);
1202 spin_unlock(&swap_lock
);
1207 * If a reference remains (rare), we would like to leave
1208 * the page in the swap cache; but try_to_unmap could
1209 * then re-duplicate the entry once we drop page lock,
1210 * so we might loop indefinitely; also, that page could
1211 * not be swapped out to other storage meanwhile. So:
1212 * delete from cache even if there's another reference,
1213 * after ensuring that the data has been saved to disk -
1214 * since if the reference remains (rarer), it will be
1215 * read from disk into another page. Splitting into two
1216 * pages would be incorrect if swap supported "shared
1217 * private" pages, but they are handled by tmpfs files.
1219 if (swap_count(*swap_map
) &&
1220 PageDirty(page
) && PageSwapCache(page
)) {
1221 struct writeback_control wbc
= {
1222 .sync_mode
= WB_SYNC_NONE
,
1225 swap_writepage(page
, &wbc
);
1227 wait_on_page_writeback(page
);
1231 * It is conceivable that a racing task removed this page from
1232 * swap cache just before we acquired the page lock at the top,
1233 * or while we dropped it in unuse_mm(). The page might even
1234 * be back in swap cache on another swap area: that we must not
1235 * delete, since it may not have been written out to swap yet.
1237 if (PageSwapCache(page
) &&
1238 likely(page_private(page
) == entry
.val
))
1239 delete_from_swap_cache(page
);
1242 * So we could skip searching mms once swap count went
1243 * to 1, we did not mark any present ptes as dirty: must
1244 * mark page dirty so shrink_page_list will preserve it.
1249 page_cache_release(page
);
1252 * Make sure that we aren't completely killing
1253 * interactive performance.
1259 if (reset_overflow
) {
1260 printk(KERN_WARNING
"swapoff: cleared swap entry overflow\n");
1267 * After a successful try_to_unuse, if no swap is now in use, we know
1268 * we can empty the mmlist. swap_lock must be held on entry and exit.
1269 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1270 * added to the mmlist just after page_duplicate - before would be racy.
1272 static void drain_mmlist(void)
1274 struct list_head
*p
, *next
;
1277 for (type
= 0; type
< nr_swapfiles
; type
++)
1278 if (swap_info
[type
]->inuse_pages
)
1280 spin_lock(&mmlist_lock
);
1281 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
1283 spin_unlock(&mmlist_lock
);
1287 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1288 * corresponds to page offset `offset'. Note that the type of this function
1289 * is sector_t, but it returns page offset into the bdev, not sector offset.
1291 sector_t
map_swap_page(swp_entry_t entry
, struct block_device
**bdev
)
1293 struct swap_info_struct
*sis
;
1294 struct swap_extent
*start_se
;
1295 struct swap_extent
*se
;
1298 sis
= swap_info
[swp_type(entry
)];
1301 offset
= swp_offset(entry
);
1302 start_se
= sis
->curr_swap_extent
;
1306 struct list_head
*lh
;
1308 if (se
->start_page
<= offset
&&
1309 offset
< (se
->start_page
+ se
->nr_pages
)) {
1310 return se
->start_block
+ (offset
- se
->start_page
);
1313 if (lh
== &sis
->extent_list
)
1315 se
= list_entry(lh
, struct swap_extent
, list
);
1316 sis
->curr_swap_extent
= se
;
1317 BUG_ON(se
== start_se
); /* It *must* be present */
1321 #ifdef CONFIG_HIBERNATION
1323 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1324 * corresponding to given index in swap_info (swap type).
1326 sector_t
swapdev_block(int type
, pgoff_t offset
)
1328 struct block_device
*bdev
;
1330 if ((unsigned int)type
>= nr_swapfiles
)
1332 if (!(swap_info
[type
]->flags
& SWP_WRITEOK
))
1334 return map_swap_page(swp_entry(type
, offset
), &bdev
);
1336 #endif /* CONFIG_HIBERNATION */
1339 * Free all of a swapdev's extent information
1341 static void destroy_swap_extents(struct swap_info_struct
*sis
)
1343 while (!list_empty(&sis
->extent_list
)) {
1344 struct swap_extent
*se
;
1346 se
= list_entry(sis
->extent_list
.next
,
1347 struct swap_extent
, list
);
1348 list_del(&se
->list
);
1354 * Add a block range (and the corresponding page range) into this swapdev's
1355 * extent list. The extent list is kept sorted in page order.
1357 * This function rather assumes that it is called in ascending page order.
1360 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
1361 unsigned long nr_pages
, sector_t start_block
)
1363 struct swap_extent
*se
;
1364 struct swap_extent
*new_se
;
1365 struct list_head
*lh
;
1367 lh
= sis
->extent_list
.prev
; /* The highest page extent */
1368 if (lh
!= &sis
->extent_list
) {
1369 se
= list_entry(lh
, struct swap_extent
, list
);
1370 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
1371 if (se
->start_block
+ se
->nr_pages
== start_block
) {
1373 se
->nr_pages
+= nr_pages
;
1379 * No merge. Insert a new extent, preserving ordering.
1381 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
1384 new_se
->start_page
= start_page
;
1385 new_se
->nr_pages
= nr_pages
;
1386 new_se
->start_block
= start_block
;
1388 list_add_tail(&new_se
->list
, &sis
->extent_list
);
1393 * A `swap extent' is a simple thing which maps a contiguous range of pages
1394 * onto a contiguous range of disk blocks. An ordered list of swap extents
1395 * is built at swapon time and is then used at swap_writepage/swap_readpage
1396 * time for locating where on disk a page belongs.
1398 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1399 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1400 * swap files identically.
1402 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1403 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1404 * swapfiles are handled *identically* after swapon time.
1406 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1407 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1408 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1409 * requirements, they are simply tossed out - we will never use those blocks
1412 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1413 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1414 * which will scribble on the fs.
1416 * The amount of disk space which a single swap extent represents varies.
1417 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1418 * extents in the list. To avoid much list walking, we cache the previous
1419 * search location in `curr_swap_extent', and start new searches from there.
1420 * This is extremely effective. The average number of iterations in
1421 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1423 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1425 struct inode
*inode
;
1426 unsigned blocks_per_page
;
1427 unsigned long page_no
;
1429 sector_t probe_block
;
1430 sector_t last_block
;
1431 sector_t lowest_block
= -1;
1432 sector_t highest_block
= 0;
1436 inode
= sis
->swap_file
->f_mapping
->host
;
1437 if (S_ISBLK(inode
->i_mode
)) {
1438 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1443 blkbits
= inode
->i_blkbits
;
1444 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1447 * Map all the blocks into the extent list. This code doesn't try
1452 last_block
= i_size_read(inode
) >> blkbits
;
1453 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1454 page_no
< sis
->max
) {
1455 unsigned block_in_page
;
1456 sector_t first_block
;
1458 first_block
= bmap(inode
, probe_block
);
1459 if (first_block
== 0)
1463 * It must be PAGE_SIZE aligned on-disk
1465 if (first_block
& (blocks_per_page
- 1)) {
1470 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1474 block
= bmap(inode
, probe_block
+ block_in_page
);
1477 if (block
!= first_block
+ block_in_page
) {
1484 first_block
>>= (PAGE_SHIFT
- blkbits
);
1485 if (page_no
) { /* exclude the header page */
1486 if (first_block
< lowest_block
)
1487 lowest_block
= first_block
;
1488 if (first_block
> highest_block
)
1489 highest_block
= first_block
;
1493 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1495 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1500 probe_block
+= blocks_per_page
;
1505 *span
= 1 + highest_block
- lowest_block
;
1507 page_no
= 1; /* force Empty message */
1509 sis
->pages
= page_no
- 1;
1510 sis
->highest_bit
= page_no
- 1;
1512 sis
->curr_swap_extent
= list_entry(sis
->extent_list
.prev
,
1513 struct swap_extent
, list
);
1516 printk(KERN_ERR
"swapon: swapfile has holes\n");
1522 SYSCALL_DEFINE1(swapoff
, const char __user
*, specialfile
)
1524 struct swap_info_struct
* p
= NULL
;
1525 unsigned short *swap_map
;
1526 struct file
*swap_file
, *victim
;
1527 struct address_space
*mapping
;
1528 struct inode
*inode
;
1533 if (!capable(CAP_SYS_ADMIN
))
1536 pathname
= getname(specialfile
);
1537 err
= PTR_ERR(pathname
);
1538 if (IS_ERR(pathname
))
1541 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1543 err
= PTR_ERR(victim
);
1547 mapping
= victim
->f_mapping
;
1549 spin_lock(&swap_lock
);
1550 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
]->next
) {
1551 p
= swap_info
[type
];
1552 if (p
->flags
& SWP_WRITEOK
) {
1553 if (p
->swap_file
->f_mapping
== mapping
)
1560 spin_unlock(&swap_lock
);
1563 if (!security_vm_enough_memory(p
->pages
))
1564 vm_unacct_memory(p
->pages
);
1567 spin_unlock(&swap_lock
);
1571 swap_list
.head
= p
->next
;
1573 swap_info
[prev
]->next
= p
->next
;
1574 if (type
== swap_list
.next
) {
1575 /* just pick something that's safe... */
1576 swap_list
.next
= swap_list
.head
;
1579 for (i
= p
->next
; i
>= 0; i
= swap_info
[i
]->next
)
1580 swap_info
[i
]->prio
= p
->prio
--;
1583 nr_swap_pages
-= p
->pages
;
1584 total_swap_pages
-= p
->pages
;
1585 p
->flags
&= ~SWP_WRITEOK
;
1586 spin_unlock(&swap_lock
);
1588 current
->flags
|= PF_OOM_ORIGIN
;
1589 err
= try_to_unuse(type
);
1590 current
->flags
&= ~PF_OOM_ORIGIN
;
1593 /* re-insert swap space back into swap_list */
1594 spin_lock(&swap_lock
);
1596 p
->prio
= --least_priority
;
1598 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
]->next
) {
1599 if (p
->prio
>= swap_info
[i
]->prio
)
1605 swap_list
.head
= swap_list
.next
= type
;
1607 swap_info
[prev
]->next
= type
;
1608 nr_swap_pages
+= p
->pages
;
1609 total_swap_pages
+= p
->pages
;
1610 p
->flags
|= SWP_WRITEOK
;
1611 spin_unlock(&swap_lock
);
1615 /* wait for any unplug function to finish */
1616 down_write(&swap_unplug_sem
);
1617 up_write(&swap_unplug_sem
);
1619 destroy_swap_extents(p
);
1620 mutex_lock(&swapon_mutex
);
1621 spin_lock(&swap_lock
);
1624 /* wait for anyone still in scan_swap_map */
1625 p
->highest_bit
= 0; /* cuts scans short */
1626 while (p
->flags
>= SWP_SCANNING
) {
1627 spin_unlock(&swap_lock
);
1628 schedule_timeout_uninterruptible(1);
1629 spin_lock(&swap_lock
);
1632 swap_file
= p
->swap_file
;
1633 p
->swap_file
= NULL
;
1635 swap_map
= p
->swap_map
;
1638 spin_unlock(&swap_lock
);
1639 mutex_unlock(&swapon_mutex
);
1641 /* Destroy swap account informatin */
1642 swap_cgroup_swapoff(type
);
1644 inode
= mapping
->host
;
1645 if (S_ISBLK(inode
->i_mode
)) {
1646 struct block_device
*bdev
= I_BDEV(inode
);
1647 set_blocksize(bdev
, p
->old_block_size
);
1650 mutex_lock(&inode
->i_mutex
);
1651 inode
->i_flags
&= ~S_SWAPFILE
;
1652 mutex_unlock(&inode
->i_mutex
);
1654 filp_close(swap_file
, NULL
);
1658 filp_close(victim
, NULL
);
1663 #ifdef CONFIG_PROC_FS
1665 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1667 struct swap_info_struct
*si
;
1671 mutex_lock(&swapon_mutex
);
1674 return SEQ_START_TOKEN
;
1676 for (type
= 0; type
< nr_swapfiles
; type
++) {
1677 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1678 si
= swap_info
[type
];
1679 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1688 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1690 struct swap_info_struct
*si
= v
;
1693 if (v
== SEQ_START_TOKEN
)
1696 type
= si
->type
+ 1;
1698 for (; type
< nr_swapfiles
; type
++) {
1699 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1700 si
= swap_info
[type
];
1701 if (!(si
->flags
& SWP_USED
) || !si
->swap_map
)
1710 static void swap_stop(struct seq_file
*swap
, void *v
)
1712 mutex_unlock(&swapon_mutex
);
1715 static int swap_show(struct seq_file
*swap
, void *v
)
1717 struct swap_info_struct
*si
= v
;
1721 if (si
== SEQ_START_TOKEN
) {
1722 seq_puts(swap
,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1726 file
= si
->swap_file
;
1727 len
= seq_path(swap
, &file
->f_path
, " \t\n\\");
1728 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1729 len
< 40 ? 40 - len
: 1, " ",
1730 S_ISBLK(file
->f_path
.dentry
->d_inode
->i_mode
) ?
1731 "partition" : "file\t",
1732 si
->pages
<< (PAGE_SHIFT
- 10),
1733 si
->inuse_pages
<< (PAGE_SHIFT
- 10),
1738 static const struct seq_operations swaps_op
= {
1739 .start
= swap_start
,
1745 static int swaps_open(struct inode
*inode
, struct file
*file
)
1747 return seq_open(file
, &swaps_op
);
1750 static const struct file_operations proc_swaps_operations
= {
1753 .llseek
= seq_lseek
,
1754 .release
= seq_release
,
1757 static int __init
procswaps_init(void)
1759 proc_create("swaps", 0, NULL
, &proc_swaps_operations
);
1762 __initcall(procswaps_init
);
1763 #endif /* CONFIG_PROC_FS */
1765 #ifdef MAX_SWAPFILES_CHECK
1766 static int __init
max_swapfiles_check(void)
1768 MAX_SWAPFILES_CHECK();
1771 late_initcall(max_swapfiles_check
);
1775 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1777 * The swapon system call
1779 SYSCALL_DEFINE2(swapon
, const char __user
*, specialfile
, int, swap_flags
)
1781 struct swap_info_struct
* p
;
1783 struct block_device
*bdev
= NULL
;
1784 struct file
*swap_file
= NULL
;
1785 struct address_space
*mapping
;
1789 union swap_header
*swap_header
= NULL
;
1790 unsigned int nr_good_pages
= 0;
1793 unsigned long maxpages
= 1;
1794 unsigned long swapfilepages
;
1795 unsigned short *swap_map
= NULL
;
1796 struct page
*page
= NULL
;
1797 struct inode
*inode
= NULL
;
1800 if (!capable(CAP_SYS_ADMIN
))
1803 p
= kzalloc(sizeof(*p
), GFP_KERNEL
);
1807 spin_lock(&swap_lock
);
1808 for (type
= 0; type
< nr_swapfiles
; type
++) {
1809 if (!(swap_info
[type
]->flags
& SWP_USED
))
1813 if (type
>= MAX_SWAPFILES
) {
1814 spin_unlock(&swap_lock
);
1818 INIT_LIST_HEAD(&p
->extent_list
);
1819 if (type
>= nr_swapfiles
) {
1821 swap_info
[type
] = p
;
1823 * Write swap_info[type] before nr_swapfiles, in case a
1824 * racing procfs swap_start() or swap_next() is reading them.
1825 * (We never shrink nr_swapfiles, we never free this entry.)
1831 p
= swap_info
[type
];
1833 * Do not memset this entry: a racing procfs swap_next()
1834 * would be relying on p->type to remain valid.
1837 p
->flags
= SWP_USED
;
1839 spin_unlock(&swap_lock
);
1841 name
= getname(specialfile
);
1842 error
= PTR_ERR(name
);
1847 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1848 error
= PTR_ERR(swap_file
);
1849 if (IS_ERR(swap_file
)) {
1854 p
->swap_file
= swap_file
;
1855 mapping
= swap_file
->f_mapping
;
1856 inode
= mapping
->host
;
1859 for (i
= 0; i
< nr_swapfiles
; i
++) {
1860 struct swap_info_struct
*q
= swap_info
[i
];
1862 if (i
== type
|| !q
->swap_file
)
1864 if (mapping
== q
->swap_file
->f_mapping
)
1869 if (S_ISBLK(inode
->i_mode
)) {
1870 bdev
= I_BDEV(inode
);
1871 error
= bd_claim(bdev
, sys_swapon
);
1877 p
->old_block_size
= block_size(bdev
);
1878 error
= set_blocksize(bdev
, PAGE_SIZE
);
1882 } else if (S_ISREG(inode
->i_mode
)) {
1883 p
->bdev
= inode
->i_sb
->s_bdev
;
1884 mutex_lock(&inode
->i_mutex
);
1886 if (IS_SWAPFILE(inode
)) {
1894 swapfilepages
= i_size_read(inode
) >> PAGE_SHIFT
;
1897 * Read the swap header.
1899 if (!mapping
->a_ops
->readpage
) {
1903 page
= read_mapping_page(mapping
, 0, swap_file
);
1905 error
= PTR_ERR(page
);
1908 swap_header
= kmap(page
);
1910 if (memcmp("SWAPSPACE2", swap_header
->magic
.magic
, 10)) {
1911 printk(KERN_ERR
"Unable to find swap-space signature\n");
1916 /* swap partition endianess hack... */
1917 if (swab32(swap_header
->info
.version
) == 1) {
1918 swab32s(&swap_header
->info
.version
);
1919 swab32s(&swap_header
->info
.last_page
);
1920 swab32s(&swap_header
->info
.nr_badpages
);
1921 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++)
1922 swab32s(&swap_header
->info
.badpages
[i
]);
1924 /* Check the swap header's sub-version */
1925 if (swap_header
->info
.version
!= 1) {
1927 "Unable to handle swap header version %d\n",
1928 swap_header
->info
.version
);
1934 p
->cluster_next
= 1;
1938 * Find out how many pages are allowed for a single swap
1939 * device. There are two limiting factors: 1) the number of
1940 * bits for the swap offset in the swp_entry_t type and
1941 * 2) the number of bits in the a swap pte as defined by
1942 * the different architectures. In order to find the
1943 * largest possible bit mask a swap entry with swap type 0
1944 * and swap offset ~0UL is created, encoded to a swap pte,
1945 * decoded to a swp_entry_t again and finally the swap
1946 * offset is extracted. This will mask all the bits from
1947 * the initial ~0UL mask that can't be encoded in either
1948 * the swp_entry_t or the architecture definition of a
1951 maxpages
= swp_offset(pte_to_swp_entry(
1952 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1953 if (maxpages
> swap_header
->info
.last_page
)
1954 maxpages
= swap_header
->info
.last_page
;
1955 p
->highest_bit
= maxpages
- 1;
1960 if (swapfilepages
&& maxpages
> swapfilepages
) {
1962 "Swap area shorter than signature indicates\n");
1965 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1967 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1970 /* OK, set up the swap map and apply the bad block list */
1971 swap_map
= vmalloc(maxpages
* sizeof(short));
1977 memset(swap_map
, 0, maxpages
* sizeof(short));
1978 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
1979 int page_nr
= swap_header
->info
.badpages
[i
];
1980 if (page_nr
<= 0 || page_nr
>= swap_header
->info
.last_page
) {
1984 swap_map
[page_nr
] = SWAP_MAP_BAD
;
1987 error
= swap_cgroup_swapon(type
, maxpages
);
1991 nr_good_pages
= swap_header
->info
.last_page
-
1992 swap_header
->info
.nr_badpages
-
1993 1 /* header page */;
1995 if (nr_good_pages
) {
1996 swap_map
[0] = SWAP_MAP_BAD
;
1998 p
->pages
= nr_good_pages
;
1999 nr_extents
= setup_swap_extents(p
, &span
);
2000 if (nr_extents
< 0) {
2004 nr_good_pages
= p
->pages
;
2006 if (!nr_good_pages
) {
2007 printk(KERN_WARNING
"Empty swap-file\n");
2013 if (blk_queue_nonrot(bdev_get_queue(p
->bdev
))) {
2014 p
->flags
|= SWP_SOLIDSTATE
;
2015 p
->cluster_next
= 1 + (random32() % p
->highest_bit
);
2017 if (discard_swap(p
) == 0)
2018 p
->flags
|= SWP_DISCARDABLE
;
2021 mutex_lock(&swapon_mutex
);
2022 spin_lock(&swap_lock
);
2023 if (swap_flags
& SWAP_FLAG_PREFER
)
2025 (swap_flags
& SWAP_FLAG_PRIO_MASK
) >> SWAP_FLAG_PRIO_SHIFT
;
2027 p
->prio
= --least_priority
;
2028 p
->swap_map
= swap_map
;
2029 p
->flags
|= SWP_WRITEOK
;
2030 nr_swap_pages
+= nr_good_pages
;
2031 total_swap_pages
+= nr_good_pages
;
2033 printk(KERN_INFO
"Adding %uk swap on %s. "
2034 "Priority:%d extents:%d across:%lluk %s%s\n",
2035 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
2036 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10),
2037 (p
->flags
& SWP_SOLIDSTATE
) ? "SS" : "",
2038 (p
->flags
& SWP_DISCARDABLE
) ? "D" : "");
2040 /* insert swap space into swap_list: */
2042 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
]->next
) {
2043 if (p
->prio
>= swap_info
[i
]->prio
)
2049 swap_list
.head
= swap_list
.next
= type
;
2051 swap_info
[prev
]->next
= type
;
2052 spin_unlock(&swap_lock
);
2053 mutex_unlock(&swapon_mutex
);
2058 set_blocksize(bdev
, p
->old_block_size
);
2061 destroy_swap_extents(p
);
2062 swap_cgroup_swapoff(type
);
2064 spin_lock(&swap_lock
);
2065 p
->swap_file
= NULL
;
2067 spin_unlock(&swap_lock
);
2070 filp_close(swap_file
, NULL
);
2072 if (page
&& !IS_ERR(page
)) {
2074 page_cache_release(page
);
2080 inode
->i_flags
|= S_SWAPFILE
;
2081 mutex_unlock(&inode
->i_mutex
);
2086 void si_swapinfo(struct sysinfo
*val
)
2089 unsigned long nr_to_be_unused
= 0;
2091 spin_lock(&swap_lock
);
2092 for (type
= 0; type
< nr_swapfiles
; type
++) {
2093 struct swap_info_struct
*si
= swap_info
[type
];
2095 if ((si
->flags
& SWP_USED
) && !(si
->flags
& SWP_WRITEOK
))
2096 nr_to_be_unused
+= si
->inuse_pages
;
2098 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
2099 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
2100 spin_unlock(&swap_lock
);
2104 * Verify that a swap entry is valid and increment its swap map count.
2106 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
2107 * "permanent", but will be reclaimed by the next swapoff.
2108 * Returns error code in following case.
2110 * - swp_entry is invalid -> EINVAL
2111 * - swp_entry is migration entry -> EINVAL
2112 * - swap-cache reference is requested but there is already one. -> EEXIST
2113 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2115 static int __swap_duplicate(swp_entry_t entry
, bool cache
)
2117 struct swap_info_struct
* p
;
2118 unsigned long offset
, type
;
2119 int result
= -EINVAL
;
2123 if (non_swap_entry(entry
))
2126 type
= swp_type(entry
);
2127 if (type
>= nr_swapfiles
)
2129 p
= swap_info
[type
];
2130 offset
= swp_offset(entry
);
2132 spin_lock(&swap_lock
);
2134 if (unlikely(offset
>= p
->max
))
2137 count
= swap_count(p
->swap_map
[offset
]);
2138 has_cache
= swap_has_cache(p
->swap_map
[offset
]);
2140 if (cache
== SWAP_CACHE
) { /* called for swapcache/swapin-readahead */
2142 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2143 if (!has_cache
&& count
) {
2144 p
->swap_map
[offset
] = encode_swapmap(count
, true);
2146 } else if (has_cache
) /* someone added cache */
2148 else if (!count
) /* no users */
2151 } else if (count
|| has_cache
) {
2152 if (count
< SWAP_MAP_MAX
- 1) {
2153 p
->swap_map
[offset
] = encode_swapmap(count
+ 1,
2156 } else if (count
<= SWAP_MAP_MAX
) {
2157 if (swap_overflow
++ < 5)
2159 "swap_dup: swap entry overflow\n");
2160 p
->swap_map
[offset
] = encode_swapmap(SWAP_MAP_MAX
,
2165 result
= -ENOENT
; /* unused swap entry */
2167 spin_unlock(&swap_lock
);
2172 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
2176 * increase reference count of swap entry by 1.
2178 void swap_duplicate(swp_entry_t entry
)
2180 __swap_duplicate(entry
, SWAP_MAP
);
2184 * @entry: swap entry for which we allocate swap cache.
2186 * Called when allocating swap cache for exising swap entry,
2187 * This can return error codes. Returns 0 at success.
2188 * -EBUSY means there is a swap cache.
2189 * Note: return code is different from swap_duplicate().
2191 int swapcache_prepare(swp_entry_t entry
)
2193 return __swap_duplicate(entry
, SWAP_CACHE
);
2197 * swap_lock prevents swap_map being freed. Don't grab an extra
2198 * reference on the swaphandle, it doesn't matter if it becomes unused.
2200 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
2202 struct swap_info_struct
*si
;
2203 int our_page_cluster
= page_cluster
;
2204 pgoff_t target
, toff
;
2208 if (!our_page_cluster
) /* no readahead */
2211 si
= swap_info
[swp_type(entry
)];
2212 target
= swp_offset(entry
);
2213 base
= (target
>> our_page_cluster
) << our_page_cluster
;
2214 end
= base
+ (1 << our_page_cluster
);
2215 if (!base
) /* first page is swap header */
2218 spin_lock(&swap_lock
);
2219 if (end
> si
->max
) /* don't go beyond end of map */
2222 /* Count contiguous allocated slots above our target */
2223 for (toff
= target
; ++toff
< end
; nr_pages
++) {
2224 /* Don't read in free or bad pages */
2225 if (!si
->swap_map
[toff
])
2227 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2230 /* Count contiguous allocated slots below our target */
2231 for (toff
= target
; --toff
>= base
; nr_pages
++) {
2232 /* Don't read in free or bad pages */
2233 if (!si
->swap_map
[toff
])
2235 if (swap_count(si
->swap_map
[toff
]) == SWAP_MAP_BAD
)
2238 spin_unlock(&swap_lock
);
2241 * Indicate starting offset, and return number of pages to get:
2242 * if only 1, say 0, since there's then no readahead to be done.
2245 return nr_pages
? ++nr_pages
: 0;