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>
35
#include <asm/pgtable.h>
36
#include <asm/tlbflush.h>
37
#include <linux/swapops.h>
38
#include <linux/page_cgroup.h>
40
static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
42
static void free_swap_count_continuations(struct swap_info_struct *);
43
static sector_t map_swap_entry(swp_entry_t, struct block_device**);
45
static DEFINE_SPINLOCK(swap_lock);
46
static unsigned int nr_swapfiles;
48
long total_swap_pages;
49
static int least_priority;
51
static const char Bad_file[] = "Bad swap file entry ";
52
static const char Unused_file[] = "Unused swap file entry ";
53
static const char Bad_offset[] = "Bad swap offset entry ";
54
static const char Unused_offset[] = "Unused swap offset entry ";
56
static struct swap_list_t swap_list = {-1, -1};
58
static struct swap_info_struct *swap_info[MAX_SWAPFILES];
60
static DEFINE_MUTEX(swapon_mutex);
62
static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
63
/* Activity counter to indicate that a swapon or swapoff has occurred */
64
static atomic_t proc_poll_event = ATOMIC_INIT(0);
66
static inline unsigned char swap_count(unsigned char ent)
68
return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
71
/* returns 1 if swap entry is freed */
73
__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
75
swp_entry_t entry = swp_entry(si->type, offset);
79
page = find_get_page(&swapper_space, entry.val);
83
* This function is called from scan_swap_map() and it's called
84
* by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
85
* We have to use trylock for avoiding deadlock. This is a special
86
* case and you should use try_to_free_swap() with explicit lock_page()
87
* in usual operations.
89
if (trylock_page(page)) {
90
ret = try_to_free_swap(page);
93
page_cache_release(page);
98
* swapon tell device that all the old swap contents can be discarded,
99
* to allow the swap device to optimize its wear-levelling.
101
static int discard_swap(struct swap_info_struct *si)
103
struct swap_extent *se;
104
sector_t start_block;
108
/* Do not discard the swap header page! */
109
se = &si->first_swap_extent;
110
start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
111
nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
113
err = blkdev_issue_discard(si->bdev, start_block,
114
nr_blocks, GFP_KERNEL, 0);
120
list_for_each_entry(se, &si->first_swap_extent.list, list) {
121
start_block = se->start_block << (PAGE_SHIFT - 9);
122
nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
124
err = blkdev_issue_discard(si->bdev, start_block,
125
nr_blocks, GFP_KERNEL, 0);
131
return err; /* That will often be -EOPNOTSUPP */
135
* swap allocation tell device that a cluster of swap can now be discarded,
136
* to allow the swap device to optimize its wear-levelling.
138
static void discard_swap_cluster(struct swap_info_struct *si,
139
pgoff_t start_page, pgoff_t nr_pages)
141
struct swap_extent *se = si->curr_swap_extent;
142
int found_extent = 0;
145
struct list_head *lh;
147
if (se->start_page <= start_page &&
148
start_page < se->start_page + se->nr_pages) {
149
pgoff_t offset = start_page - se->start_page;
150
sector_t start_block = se->start_block + offset;
151
sector_t nr_blocks = se->nr_pages - offset;
153
if (nr_blocks > nr_pages)
154
nr_blocks = nr_pages;
155
start_page += nr_blocks;
156
nr_pages -= nr_blocks;
159
si->curr_swap_extent = se;
161
start_block <<= PAGE_SHIFT - 9;
162
nr_blocks <<= PAGE_SHIFT - 9;
163
if (blkdev_issue_discard(si->bdev, start_block,
164
nr_blocks, GFP_NOIO, 0))
169
se = list_entry(lh, struct swap_extent, list);
173
static int wait_for_discard(void *word)
179
#define SWAPFILE_CLUSTER 256
180
#define LATENCY_LIMIT 256
182
static unsigned long scan_swap_map(struct swap_info_struct *si,
185
unsigned long offset;
186
unsigned long scan_base;
187
unsigned long last_in_cluster = 0;
188
int latency_ration = LATENCY_LIMIT;
189
int found_free_cluster = 0;
192
* We try to cluster swap pages by allocating them sequentially
193
* in swap. Once we've allocated SWAPFILE_CLUSTER pages this
194
* way, however, we resort to first-free allocation, starting
195
* a new cluster. This prevents us from scattering swap pages
196
* all over the entire swap partition, so that we reduce
197
* overall disk seek times between swap pages. -- sct
198
* But we do now try to find an empty cluster. -Andrea
199
* And we let swap pages go all over an SSD partition. Hugh
202
si->flags += SWP_SCANNING;
203
scan_base = offset = si->cluster_next;
205
if (unlikely(!si->cluster_nr--)) {
206
if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
207
si->cluster_nr = SWAPFILE_CLUSTER - 1;
210
if (si->flags & SWP_DISCARDABLE) {
212
* Start range check on racing allocations, in case
213
* they overlap the cluster we eventually decide on
214
* (we scan without swap_lock to allow preemption).
215
* It's hardly conceivable that cluster_nr could be
216
* wrapped during our scan, but don't depend on it.
218
if (si->lowest_alloc)
220
si->lowest_alloc = si->max;
221
si->highest_alloc = 0;
223
spin_unlock(&swap_lock);
226
* If seek is expensive, start searching for new cluster from
227
* start of partition, to minimize the span of allocated swap.
228
* But if seek is cheap, search from our current position, so
229
* that swap is allocated from all over the partition: if the
230
* Flash Translation Layer only remaps within limited zones,
231
* we don't want to wear out the first zone too quickly.
233
if (!(si->flags & SWP_SOLIDSTATE))
234
scan_base = offset = si->lowest_bit;
235
last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
237
/* Locate the first empty (unaligned) cluster */
238
for (; last_in_cluster <= si->highest_bit; offset++) {
239
if (si->swap_map[offset])
240
last_in_cluster = offset + SWAPFILE_CLUSTER;
241
else if (offset == last_in_cluster) {
242
spin_lock(&swap_lock);
243
offset -= SWAPFILE_CLUSTER - 1;
244
si->cluster_next = offset;
245
si->cluster_nr = SWAPFILE_CLUSTER - 1;
246
found_free_cluster = 1;
249
if (unlikely(--latency_ration < 0)) {
251
latency_ration = LATENCY_LIMIT;
255
offset = si->lowest_bit;
256
last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
258
/* Locate the first empty (unaligned) cluster */
259
for (; last_in_cluster < scan_base; offset++) {
260
if (si->swap_map[offset])
261
last_in_cluster = offset + SWAPFILE_CLUSTER;
262
else if (offset == last_in_cluster) {
263
spin_lock(&swap_lock);
264
offset -= SWAPFILE_CLUSTER - 1;
265
si->cluster_next = offset;
266
si->cluster_nr = SWAPFILE_CLUSTER - 1;
267
found_free_cluster = 1;
270
if (unlikely(--latency_ration < 0)) {
272
latency_ration = LATENCY_LIMIT;
277
spin_lock(&swap_lock);
278
si->cluster_nr = SWAPFILE_CLUSTER - 1;
279
si->lowest_alloc = 0;
283
if (!(si->flags & SWP_WRITEOK))
285
if (!si->highest_bit)
287
if (offset > si->highest_bit)
288
scan_base = offset = si->lowest_bit;
290
/* reuse swap entry of cache-only swap if not busy. */
291
if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
293
spin_unlock(&swap_lock);
294
swap_was_freed = __try_to_reclaim_swap(si, offset);
295
spin_lock(&swap_lock);
296
/* entry was freed successfully, try to use this again */
299
goto scan; /* check next one */
302
if (si->swap_map[offset])
305
if (offset == si->lowest_bit)
307
if (offset == si->highest_bit)
310
if (si->inuse_pages == si->pages) {
311
si->lowest_bit = si->max;
314
si->swap_map[offset] = usage;
315
si->cluster_next = offset + 1;
316
si->flags -= SWP_SCANNING;
318
if (si->lowest_alloc) {
320
* Only set when SWP_DISCARDABLE, and there's a scan
321
* for a free cluster in progress or just completed.
323
if (found_free_cluster) {
325
* To optimize wear-levelling, discard the
326
* old data of the cluster, taking care not to
327
* discard any of its pages that have already
328
* been allocated by racing tasks (offset has
329
* already stepped over any at the beginning).
331
if (offset < si->highest_alloc &&
332
si->lowest_alloc <= last_in_cluster)
333
last_in_cluster = si->lowest_alloc - 1;
334
si->flags |= SWP_DISCARDING;
335
spin_unlock(&swap_lock);
337
if (offset < last_in_cluster)
338
discard_swap_cluster(si, offset,
339
last_in_cluster - offset + 1);
341
spin_lock(&swap_lock);
342
si->lowest_alloc = 0;
343
si->flags &= ~SWP_DISCARDING;
345
smp_mb(); /* wake_up_bit advises this */
346
wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
348
} else if (si->flags & SWP_DISCARDING) {
350
* Delay using pages allocated by racing tasks
351
* until the whole discard has been issued. We
352
* could defer that delay until swap_writepage,
353
* but it's easier to keep this self-contained.
355
spin_unlock(&swap_lock);
356
wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
357
wait_for_discard, TASK_UNINTERRUPTIBLE);
358
spin_lock(&swap_lock);
361
* Note pages allocated by racing tasks while
362
* scan for a free cluster is in progress, so
363
* that its final discard can exclude them.
365
if (offset < si->lowest_alloc)
366
si->lowest_alloc = offset;
367
if (offset > si->highest_alloc)
368
si->highest_alloc = offset;
374
spin_unlock(&swap_lock);
375
while (++offset <= si->highest_bit) {
376
if (!si->swap_map[offset]) {
377
spin_lock(&swap_lock);
380
if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
381
spin_lock(&swap_lock);
384
if (unlikely(--latency_ration < 0)) {
386
latency_ration = LATENCY_LIMIT;
389
offset = si->lowest_bit;
390
while (++offset < scan_base) {
391
if (!si->swap_map[offset]) {
392
spin_lock(&swap_lock);
395
if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
396
spin_lock(&swap_lock);
399
if (unlikely(--latency_ration < 0)) {
401
latency_ration = LATENCY_LIMIT;
404
spin_lock(&swap_lock);
407
si->flags -= SWP_SCANNING;
411
swp_entry_t get_swap_page(void)
413
struct swap_info_struct *si;
418
spin_lock(&swap_lock);
419
if (nr_swap_pages <= 0)
423
for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
424
si = swap_info[type];
427
(!wrapped && si->prio != swap_info[next]->prio)) {
428
next = swap_list.head;
432
if (!si->highest_bit)
434
if (!(si->flags & SWP_WRITEOK))
437
swap_list.next = next;
438
/* This is called for allocating swap entry for cache */
439
offset = scan_swap_map(si, SWAP_HAS_CACHE);
441
spin_unlock(&swap_lock);
442
return swp_entry(type, offset);
444
next = swap_list.next;
449
spin_unlock(&swap_lock);
450
return (swp_entry_t) {0};
453
/* The only caller of this function is now susupend routine */
454
swp_entry_t get_swap_page_of_type(int type)
456
struct swap_info_struct *si;
459
spin_lock(&swap_lock);
460
si = swap_info[type];
461
if (si && (si->flags & SWP_WRITEOK)) {
463
/* This is called for allocating swap entry, not cache */
464
offset = scan_swap_map(si, 1);
466
spin_unlock(&swap_lock);
467
return swp_entry(type, offset);
471
spin_unlock(&swap_lock);
472
return (swp_entry_t) {0};
475
static struct swap_info_struct *swap_info_get(swp_entry_t entry)
477
struct swap_info_struct *p;
478
unsigned long offset, type;
482
type = swp_type(entry);
483
if (type >= nr_swapfiles)
486
if (!(p->flags & SWP_USED))
488
offset = swp_offset(entry);
489
if (offset >= p->max)
491
if (!p->swap_map[offset])
493
spin_lock(&swap_lock);
497
printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
500
printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
503
printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
506
printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
511
static unsigned char swap_entry_free(struct swap_info_struct *p,
512
swp_entry_t entry, unsigned char usage)
514
unsigned long offset = swp_offset(entry);
516
unsigned char has_cache;
518
count = p->swap_map[offset];
519
has_cache = count & SWAP_HAS_CACHE;
520
count &= ~SWAP_HAS_CACHE;
522
if (usage == SWAP_HAS_CACHE) {
523
VM_BUG_ON(!has_cache);
525
} else if (count == SWAP_MAP_SHMEM) {
527
* Or we could insist on shmem.c using a special
528
* swap_shmem_free() and free_shmem_swap_and_cache()...
531
} else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
532
if (count == COUNT_CONTINUED) {
533
if (swap_count_continued(p, offset, count))
534
count = SWAP_MAP_MAX | COUNT_CONTINUED;
536
count = SWAP_MAP_MAX;
542
mem_cgroup_uncharge_swap(entry);
544
usage = count | has_cache;
545
p->swap_map[offset] = usage;
547
/* free if no reference */
549
struct gendisk *disk = p->bdev->bd_disk;
550
if (offset < p->lowest_bit)
551
p->lowest_bit = offset;
552
if (offset > p->highest_bit)
553
p->highest_bit = offset;
554
if (swap_list.next >= 0 &&
555
p->prio > swap_info[swap_list.next]->prio)
556
swap_list.next = p->type;
559
if ((p->flags & SWP_BLKDEV) &&
560
disk->fops->swap_slot_free_notify)
561
disk->fops->swap_slot_free_notify(p->bdev, offset);
568
* Caller has made sure that the swapdevice corresponding to entry
569
* is still around or has not been recycled.
571
void swap_free(swp_entry_t entry)
573
struct swap_info_struct *p;
575
p = swap_info_get(entry);
577
swap_entry_free(p, entry, 1);
578
spin_unlock(&swap_lock);
583
* Called after dropping swapcache to decrease refcnt to swap entries.
585
void swapcache_free(swp_entry_t entry, struct page *page)
587
struct swap_info_struct *p;
590
p = swap_info_get(entry);
592
count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
594
mem_cgroup_uncharge_swapcache(page, entry, count != 0);
595
spin_unlock(&swap_lock);
600
* How many references to page are currently swapped out?
601
* This does not give an exact answer when swap count is continued,
602
* but does include the high COUNT_CONTINUED flag to allow for that.
604
static inline int page_swapcount(struct page *page)
607
struct swap_info_struct *p;
610
entry.val = page_private(page);
611
p = swap_info_get(entry);
613
count = swap_count(p->swap_map[swp_offset(entry)]);
614
spin_unlock(&swap_lock);
620
* We can write to an anon page without COW if there are no other references
621
* to it. And as a side-effect, free up its swap: because the old content
622
* on disk will never be read, and seeking back there to write new content
623
* later would only waste time away from clustering.
625
int reuse_swap_page(struct page *page)
629
VM_BUG_ON(!PageLocked(page));
630
if (unlikely(PageKsm(page)))
632
count = page_mapcount(page);
633
if (count <= 1 && PageSwapCache(page)) {
634
count += page_swapcount(page);
635
if (count == 1 && !PageWriteback(page)) {
636
delete_from_swap_cache(page);
644
* If swap is getting full, or if there are no more mappings of this page,
645
* then try_to_free_swap is called to free its swap space.
647
int try_to_free_swap(struct page *page)
649
VM_BUG_ON(!PageLocked(page));
651
if (!PageSwapCache(page))
653
if (PageWriteback(page))
655
if (page_swapcount(page))
659
* Once hibernation has begun to create its image of memory,
660
* there's a danger that one of the calls to try_to_free_swap()
661
* - most probably a call from __try_to_reclaim_swap() while
662
* hibernation is allocating its own swap pages for the image,
663
* but conceivably even a call from memory reclaim - will free
664
* the swap from a page which has already been recorded in the
665
* image as a clean swapcache page, and then reuse its swap for
666
* another page of the image. On waking from hibernation, the
667
* original page might be freed under memory pressure, then
668
* later read back in from swap, now with the wrong data.
670
* Hibernation clears bits from gfp_allowed_mask to prevent
671
* memory reclaim from writing to disk, so check that here.
673
if (!(gfp_allowed_mask & __GFP_IO))
676
delete_from_swap_cache(page);
682
* Free the swap entry like above, but also try to
683
* free the page cache entry if it is the last user.
685
int free_swap_and_cache(swp_entry_t entry)
687
struct swap_info_struct *p;
688
struct page *page = NULL;
690
if (non_swap_entry(entry))
693
p = swap_info_get(entry);
695
if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
696
page = find_get_page(&swapper_space, entry.val);
697
if (page && !trylock_page(page)) {
698
page_cache_release(page);
702
spin_unlock(&swap_lock);
706
* Not mapped elsewhere, or swap space full? Free it!
707
* Also recheck PageSwapCache now page is locked (above).
709
if (PageSwapCache(page) && !PageWriteback(page) &&
710
(!page_mapped(page) || vm_swap_full())) {
711
delete_from_swap_cache(page);
715
page_cache_release(page);
720
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
722
* mem_cgroup_count_swap_user - count the user of a swap entry
723
* @ent: the swap entry to be checked
724
* @pagep: the pointer for the swap cache page of the entry to be stored
726
* Returns the number of the user of the swap entry. The number is valid only
727
* for swaps of anonymous pages.
728
* If the entry is found on swap cache, the page is stored to pagep with
729
* refcount of it being incremented.
731
int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
734
struct swap_info_struct *p;
737
page = find_get_page(&swapper_space, ent.val);
739
count += page_mapcount(page);
740
p = swap_info_get(ent);
742
count += swap_count(p->swap_map[swp_offset(ent)]);
743
spin_unlock(&swap_lock);
751
#ifdef CONFIG_HIBERNATION
753
* Find the swap type that corresponds to given device (if any).
755
* @offset - number of the PAGE_SIZE-sized block of the device, starting
756
* from 0, in which the swap header is expected to be located.
758
* This is needed for the suspend to disk (aka swsusp).
760
int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
762
struct block_device *bdev = NULL;
766
bdev = bdget(device);
768
spin_lock(&swap_lock);
769
for (type = 0; type < nr_swapfiles; type++) {
770
struct swap_info_struct *sis = swap_info[type];
772
if (!(sis->flags & SWP_WRITEOK))
777
*bdev_p = bdgrab(sis->bdev);
779
spin_unlock(&swap_lock);
782
if (bdev == sis->bdev) {
783
struct swap_extent *se = &sis->first_swap_extent;
785
if (se->start_block == offset) {
787
*bdev_p = bdgrab(sis->bdev);
789
spin_unlock(&swap_lock);
795
spin_unlock(&swap_lock);
803
* Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
804
* corresponding to given index in swap_info (swap type).
806
sector_t swapdev_block(int type, pgoff_t offset)
808
struct block_device *bdev;
810
if ((unsigned int)type >= nr_swapfiles)
812
if (!(swap_info[type]->flags & SWP_WRITEOK))
814
return map_swap_entry(swp_entry(type, offset), &bdev);
818
* Return either the total number of swap pages of given type, or the number
819
* of free pages of that type (depending on @free)
821
* This is needed for software suspend
823
unsigned int count_swap_pages(int type, int free)
827
spin_lock(&swap_lock);
828
if ((unsigned int)type < nr_swapfiles) {
829
struct swap_info_struct *sis = swap_info[type];
831
if (sis->flags & SWP_WRITEOK) {
834
n -= sis->inuse_pages;
837
spin_unlock(&swap_lock);
840
#endif /* CONFIG_HIBERNATION */
843
* No need to decide whether this PTE shares the swap entry with others,
844
* just let do_wp_page work it out if a write is requested later - to
845
* force COW, vm_page_prot omits write permission from any private vma.
847
static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
848
unsigned long addr, swp_entry_t entry, struct page *page)
850
struct mem_cgroup *ptr;
855
if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
860
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
861
if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
863
mem_cgroup_cancel_charge_swapin(ptr);
868
dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
869
inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
871
set_pte_at(vma->vm_mm, addr, pte,
872
pte_mkold(mk_pte(page, vma->vm_page_prot)));
873
page_add_anon_rmap(page, vma, addr);
874
mem_cgroup_commit_charge_swapin(page, ptr);
877
* Move the page to the active list so it is not
878
* immediately swapped out again after swapon.
882
pte_unmap_unlock(pte, ptl);
887
static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
888
unsigned long addr, unsigned long end,
889
swp_entry_t entry, struct page *page)
891
pte_t swp_pte = swp_entry_to_pte(entry);
896
* We don't actually need pte lock while scanning for swp_pte: since
897
* we hold page lock and mmap_sem, swp_pte cannot be inserted into the
898
* page table while we're scanning; though it could get zapped, and on
899
* some architectures (e.g. x86_32 with PAE) we might catch a glimpse
900
* of unmatched parts which look like swp_pte, so unuse_pte must
901
* recheck under pte lock. Scanning without pte lock lets it be
902
* preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
904
pte = pte_offset_map(pmd, addr);
907
* swapoff spends a _lot_ of time in this loop!
908
* Test inline before going to call unuse_pte.
910
if (unlikely(pte_same(*pte, swp_pte))) {
912
ret = unuse_pte(vma, pmd, addr, entry, page);
915
pte = pte_offset_map(pmd, addr);
917
} while (pte++, addr += PAGE_SIZE, addr != end);
923
static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
924
unsigned long addr, unsigned long end,
925
swp_entry_t entry, struct page *page)
931
pmd = pmd_offset(pud, addr);
933
next = pmd_addr_end(addr, end);
934
if (unlikely(pmd_trans_huge(*pmd)))
936
if (pmd_none_or_clear_bad(pmd))
938
ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
941
} while (pmd++, addr = next, addr != end);
945
static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
946
unsigned long addr, unsigned long end,
947
swp_entry_t entry, struct page *page)
953
pud = pud_offset(pgd, addr);
955
next = pud_addr_end(addr, end);
956
if (pud_none_or_clear_bad(pud))
958
ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
961
} while (pud++, addr = next, addr != end);
965
static int unuse_vma(struct vm_area_struct *vma,
966
swp_entry_t entry, struct page *page)
969
unsigned long addr, end, next;
972
if (page_anon_vma(page)) {
973
addr = page_address_in_vma(page, vma);
977
end = addr + PAGE_SIZE;
979
addr = vma->vm_start;
983
pgd = pgd_offset(vma->vm_mm, addr);
985
next = pgd_addr_end(addr, end);
986
if (pgd_none_or_clear_bad(pgd))
988
ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
991
} while (pgd++, addr = next, addr != end);
995
static int unuse_mm(struct mm_struct *mm,
996
swp_entry_t entry, struct page *page)
998
struct vm_area_struct *vma;
1001
if (!down_read_trylock(&mm->mmap_sem)) {
1003
* Activate page so shrink_inactive_list is unlikely to unmap
1004
* its ptes while lock is dropped, so swapoff can make progress.
1006
activate_page(page);
1008
down_read(&mm->mmap_sem);
1011
for (vma = mm->mmap; vma; vma = vma->vm_next) {
1012
if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
1015
up_read(&mm->mmap_sem);
1016
return (ret < 0)? ret: 0;
1020
* Scan swap_map from current position to next entry still in use.
1021
* Recycle to start on reaching the end, returning 0 when empty.
1023
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1026
unsigned int max = si->max;
1027
unsigned int i = prev;
1028
unsigned char count;
1031
* No need for swap_lock here: we're just looking
1032
* for whether an entry is in use, not modifying it; false
1033
* hits are okay, and sys_swapoff() has already prevented new
1034
* allocations from this area (while holding swap_lock).
1043
* No entries in use at top of swap_map,
1044
* loop back to start and recheck there.
1050
count = si->swap_map[i];
1051
if (count && swap_count(count) != SWAP_MAP_BAD)
1058
* We completely avoid races by reading each swap page in advance,
1059
* and then search for the process using it. All the necessary
1060
* page table adjustments can then be made atomically.
1062
static int try_to_unuse(unsigned int type)
1064
struct swap_info_struct *si = swap_info[type];
1065
struct mm_struct *start_mm;
1066
unsigned char *swap_map;
1067
unsigned char swcount;
1074
* When searching mms for an entry, a good strategy is to
1075
* start at the first mm we freed the previous entry from
1076
* (though actually we don't notice whether we or coincidence
1077
* freed the entry). Initialize this start_mm with a hold.
1079
* A simpler strategy would be to start at the last mm we
1080
* freed the previous entry from; but that would take less
1081
* advantage of mmlist ordering, which clusters forked mms
1082
* together, child after parent. If we race with dup_mmap(), we
1083
* prefer to resolve parent before child, lest we miss entries
1084
* duplicated after we scanned child: using last mm would invert
1087
start_mm = &init_mm;
1088
atomic_inc(&init_mm.mm_users);
1091
* Keep on scanning until all entries have gone. Usually,
1092
* one pass through swap_map is enough, but not necessarily:
1093
* there are races when an instance of an entry might be missed.
1095
while ((i = find_next_to_unuse(si, i)) != 0) {
1096
if (signal_pending(current)) {
1102
* Get a page for the entry, using the existing swap
1103
* cache page if there is one. Otherwise, get a clean
1104
* page and read the swap into it.
1106
swap_map = &si->swap_map[i];
1107
entry = swp_entry(type, i);
1108
page = read_swap_cache_async(entry,
1109
GFP_HIGHUSER_MOVABLE, NULL, 0);
1112
* Either swap_duplicate() failed because entry
1113
* has been freed independently, and will not be
1114
* reused since sys_swapoff() already disabled
1115
* allocation from here, or alloc_page() failed.
1124
* Don't hold on to start_mm if it looks like exiting.
1126
if (atomic_read(&start_mm->mm_users) == 1) {
1128
start_mm = &init_mm;
1129
atomic_inc(&init_mm.mm_users);
1133
* Wait for and lock page. When do_swap_page races with
1134
* try_to_unuse, do_swap_page can handle the fault much
1135
* faster than try_to_unuse can locate the entry. This
1136
* apparently redundant "wait_on_page_locked" lets try_to_unuse
1137
* defer to do_swap_page in such a case - in some tests,
1138
* do_swap_page and try_to_unuse repeatedly compete.
1140
wait_on_page_locked(page);
1141
wait_on_page_writeback(page);
1143
wait_on_page_writeback(page);
1146
* Remove all references to entry.
1148
swcount = *swap_map;
1149
if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1150
retval = shmem_unuse(entry, page);
1151
/* page has already been unlocked and released */
1156
if (swap_count(swcount) && start_mm != &init_mm)
1157
retval = unuse_mm(start_mm, entry, page);
1159
if (swap_count(*swap_map)) {
1160
int set_start_mm = (*swap_map >= swcount);
1161
struct list_head *p = &start_mm->mmlist;
1162
struct mm_struct *new_start_mm = start_mm;
1163
struct mm_struct *prev_mm = start_mm;
1164
struct mm_struct *mm;
1166
atomic_inc(&new_start_mm->mm_users);
1167
atomic_inc(&prev_mm->mm_users);
1168
spin_lock(&mmlist_lock);
1169
while (swap_count(*swap_map) && !retval &&
1170
(p = p->next) != &start_mm->mmlist) {
1171
mm = list_entry(p, struct mm_struct, mmlist);
1172
if (!atomic_inc_not_zero(&mm->mm_users))
1174
spin_unlock(&mmlist_lock);
1180
swcount = *swap_map;
1181
if (!swap_count(swcount)) /* any usage ? */
1183
else if (mm == &init_mm)
1186
retval = unuse_mm(mm, entry, page);
1188
if (set_start_mm && *swap_map < swcount) {
1189
mmput(new_start_mm);
1190
atomic_inc(&mm->mm_users);
1194
spin_lock(&mmlist_lock);
1196
spin_unlock(&mmlist_lock);
1199
start_mm = new_start_mm;
1203
page_cache_release(page);
1208
* If a reference remains (rare), we would like to leave
1209
* the page in the swap cache; but try_to_unmap could
1210
* then re-duplicate the entry once we drop page lock,
1211
* so we might loop indefinitely; also, that page could
1212
* not be swapped out to other storage meanwhile. So:
1213
* delete from cache even if there's another reference,
1214
* after ensuring that the data has been saved to disk -
1215
* since if the reference remains (rarer), it will be
1216
* read from disk into another page. Splitting into two
1217
* pages would be incorrect if swap supported "shared
1218
* private" pages, but they are handled by tmpfs files.
1220
* Given how unuse_vma() targets one particular offset
1221
* in an anon_vma, once the anon_vma has been determined,
1222
* this splitting happens to be just what is needed to
1223
* handle where KSM pages have been swapped out: re-reading
1224
* is unnecessarily slow, but we can fix that later on.
1226
if (swap_count(*swap_map) &&
1227
PageDirty(page) && PageSwapCache(page)) {
1228
struct writeback_control wbc = {
1229
.sync_mode = WB_SYNC_NONE,
1232
swap_writepage(page, &wbc);
1234
wait_on_page_writeback(page);
1238
* It is conceivable that a racing task removed this page from
1239
* swap cache just before we acquired the page lock at the top,
1240
* or while we dropped it in unuse_mm(). The page might even
1241
* be back in swap cache on another swap area: that we must not
1242
* delete, since it may not have been written out to swap yet.
1244
if (PageSwapCache(page) &&
1245
likely(page_private(page) == entry.val))
1246
delete_from_swap_cache(page);
1249
* So we could skip searching mms once swap count went
1250
* to 1, we did not mark any present ptes as dirty: must
1251
* mark page dirty so shrink_page_list will preserve it.
1255
page_cache_release(page);
1258
* Make sure that we aren't completely killing
1259
* interactive performance.
1269
* After a successful try_to_unuse, if no swap is now in use, we know
1270
* we can empty the mmlist. swap_lock must be held on entry and exit.
1271
* Note that mmlist_lock nests inside swap_lock, and an mm must be
1272
* added to the mmlist just after page_duplicate - before would be racy.
1274
static void drain_mmlist(void)
1276
struct list_head *p, *next;
1279
for (type = 0; type < nr_swapfiles; type++)
1280
if (swap_info[type]->inuse_pages)
1282
spin_lock(&mmlist_lock);
1283
list_for_each_safe(p, next, &init_mm.mmlist)
1285
spin_unlock(&mmlist_lock);
1289
* Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1290
* corresponds to page offset for the specified swap entry.
1291
* Note that the type of this function is sector_t, but it returns page offset
1292
* into the bdev, not sector offset.
1294
static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1296
struct swap_info_struct *sis;
1297
struct swap_extent *start_se;
1298
struct swap_extent *se;
1301
sis = swap_info[swp_type(entry)];
1304
offset = swp_offset(entry);
1305
start_se = sis->curr_swap_extent;
1309
struct list_head *lh;
1311
if (se->start_page <= offset &&
1312
offset < (se->start_page + se->nr_pages)) {
1313
return se->start_block + (offset - se->start_page);
1316
se = list_entry(lh, struct swap_extent, list);
1317
sis->curr_swap_extent = se;
1318
BUG_ON(se == start_se); /* It *must* be present */
1323
* Returns the page offset into bdev for the specified page's swap entry.
1325
sector_t map_swap_page(struct page *page, struct block_device **bdev)
1328
entry.val = page_private(page);
1329
return map_swap_entry(entry, bdev);
1333
* Free all of a swapdev's extent information
1335
static void destroy_swap_extents(struct swap_info_struct *sis)
1337
while (!list_empty(&sis->first_swap_extent.list)) {
1338
struct swap_extent *se;
1340
se = list_entry(sis->first_swap_extent.list.next,
1341
struct swap_extent, list);
1342
list_del(&se->list);
1348
* Add a block range (and the corresponding page range) into this swapdev's
1349
* extent list. The extent list is kept sorted in page order.
1351
* This function rather assumes that it is called in ascending page order.
1354
add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1355
unsigned long nr_pages, sector_t start_block)
1357
struct swap_extent *se;
1358
struct swap_extent *new_se;
1359
struct list_head *lh;
1361
if (start_page == 0) {
1362
se = &sis->first_swap_extent;
1363
sis->curr_swap_extent = se;
1365
se->nr_pages = nr_pages;
1366
se->start_block = start_block;
1369
lh = sis->first_swap_extent.list.prev; /* Highest extent */
1370
se = list_entry(lh, struct swap_extent, list);
1371
BUG_ON(se->start_page + se->nr_pages != start_page);
1372
if (se->start_block + se->nr_pages == start_block) {
1374
se->nr_pages += nr_pages;
1380
* No merge. Insert a new extent, preserving ordering.
1382
new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1385
new_se->start_page = start_page;
1386
new_se->nr_pages = nr_pages;
1387
new_se->start_block = start_block;
1389
list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1394
* A `swap extent' is a simple thing which maps a contiguous range of pages
1395
* onto a contiguous range of disk blocks. An ordered list of swap extents
1396
* is built at swapon time and is then used at swap_writepage/swap_readpage
1397
* time for locating where on disk a page belongs.
1399
* If the swapfile is an S_ISBLK block device, a single extent is installed.
1400
* This is done so that the main operating code can treat S_ISBLK and S_ISREG
1401
* swap files identically.
1403
* Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1404
* extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1405
* swapfiles are handled *identically* after swapon time.
1407
* For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1408
* and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1409
* some stray blocks are found which do not fall within the PAGE_SIZE alignment
1410
* requirements, they are simply tossed out - we will never use those blocks
1413
* For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1414
* prevents root from shooting her foot off by ftruncating an in-use swapfile,
1415
* which will scribble on the fs.
1417
* The amount of disk space which a single swap extent represents varies.
1418
* Typically it is in the 1-4 megabyte range. So we can have hundreds of
1419
* extents in the list. To avoid much list walking, we cache the previous
1420
* search location in `curr_swap_extent', and start new searches from there.
1421
* This is extremely effective. The average number of iterations in
1422
* map_swap_page() has been measured at about 0.3 per page. - akpm.
1424
static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1426
struct inode *inode;
1427
unsigned blocks_per_page;
1428
unsigned long page_no;
1430
sector_t probe_block;
1431
sector_t last_block;
1432
sector_t lowest_block = -1;
1433
sector_t highest_block = 0;
1437
inode = sis->swap_file->f_mapping->host;
1438
if (S_ISBLK(inode->i_mode)) {
1439
ret = add_swap_extent(sis, 0, sis->max, 0);
1444
blkbits = inode->i_blkbits;
1445
blocks_per_page = PAGE_SIZE >> blkbits;
1448
* Map all the blocks into the extent list. This code doesn't try
1453
last_block = i_size_read(inode) >> blkbits;
1454
while ((probe_block + blocks_per_page) <= last_block &&
1455
page_no < sis->max) {
1456
unsigned block_in_page;
1457
sector_t first_block;
1459
first_block = bmap(inode, probe_block);
1460
if (first_block == 0)
1464
* It must be PAGE_SIZE aligned on-disk
1466
if (first_block & (blocks_per_page - 1)) {
1471
for (block_in_page = 1; block_in_page < blocks_per_page;
1475
block = bmap(inode, probe_block + block_in_page);
1478
if (block != first_block + block_in_page) {
1485
first_block >>= (PAGE_SHIFT - blkbits);
1486
if (page_no) { /* exclude the header page */
1487
if (first_block < lowest_block)
1488
lowest_block = first_block;
1489
if (first_block > highest_block)
1490
highest_block = first_block;
1494
* We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1496
ret = add_swap_extent(sis, page_no, 1, first_block);
1501
probe_block += blocks_per_page;
1506
*span = 1 + highest_block - lowest_block;
1508
page_no = 1; /* force Empty message */
1510
sis->pages = page_no - 1;
1511
sis->highest_bit = page_no - 1;
1515
printk(KERN_ERR "swapon: swapfile has holes\n");
1520
static void enable_swap_info(struct swap_info_struct *p, int prio,
1521
unsigned char *swap_map)
1525
spin_lock(&swap_lock);
1529
p->prio = --least_priority;
1530
p->swap_map = swap_map;
1531
p->flags |= SWP_WRITEOK;
1532
nr_swap_pages += p->pages;
1533
total_swap_pages += p->pages;
1535
/* insert swap space into swap_list: */
1537
for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1538
if (p->prio >= swap_info[i]->prio)
1544
swap_list.head = swap_list.next = p->type;
1546
swap_info[prev]->next = p->type;
1547
spin_unlock(&swap_lock);
1550
SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1552
struct swap_info_struct *p = NULL;
1553
unsigned char *swap_map;
1554
struct file *swap_file, *victim;
1555
struct address_space *mapping;
1556
struct inode *inode;
1562
if (!capable(CAP_SYS_ADMIN))
1565
pathname = getname(specialfile);
1566
err = PTR_ERR(pathname);
1567
if (IS_ERR(pathname))
1570
victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1572
err = PTR_ERR(victim);
1576
mapping = victim->f_mapping;
1578
spin_lock(&swap_lock);
1579
for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1580
p = swap_info[type];
1581
if (p->flags & SWP_WRITEOK) {
1582
if (p->swap_file->f_mapping == mapping)
1589
spin_unlock(&swap_lock);
1592
if (!security_vm_enough_memory(p->pages))
1593
vm_unacct_memory(p->pages);
1596
spin_unlock(&swap_lock);
1600
swap_list.head = p->next;
1602
swap_info[prev]->next = p->next;
1603
if (type == swap_list.next) {
1604
/* just pick something that's safe... */
1605
swap_list.next = swap_list.head;
1608
for (i = p->next; i >= 0; i = swap_info[i]->next)
1609
swap_info[i]->prio = p->prio--;
1612
nr_swap_pages -= p->pages;
1613
total_swap_pages -= p->pages;
1614
p->flags &= ~SWP_WRITEOK;
1615
spin_unlock(&swap_lock);
1617
oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
1618
err = try_to_unuse(type);
1619
compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);
1623
* reading p->prio and p->swap_map outside the lock is
1624
* safe here because only sys_swapon and sys_swapoff
1625
* change them, and there can be no other sys_swapon or
1626
* sys_swapoff for this swap_info_struct at this point.
1628
/* re-insert swap space back into swap_list */
1629
enable_swap_info(p, p->prio, p->swap_map);
1633
destroy_swap_extents(p);
1634
if (p->flags & SWP_CONTINUED)
1635
free_swap_count_continuations(p);
1637
mutex_lock(&swapon_mutex);
1638
spin_lock(&swap_lock);
1641
/* wait for anyone still in scan_swap_map */
1642
p->highest_bit = 0; /* cuts scans short */
1643
while (p->flags >= SWP_SCANNING) {
1644
spin_unlock(&swap_lock);
1645
schedule_timeout_uninterruptible(1);
1646
spin_lock(&swap_lock);
1649
swap_file = p->swap_file;
1650
p->swap_file = NULL;
1652
swap_map = p->swap_map;
1655
spin_unlock(&swap_lock);
1656
mutex_unlock(&swapon_mutex);
1658
/* Destroy swap account informatin */
1659
swap_cgroup_swapoff(type);
1661
inode = mapping->host;
1662
if (S_ISBLK(inode->i_mode)) {
1663
struct block_device *bdev = I_BDEV(inode);
1664
set_blocksize(bdev, p->old_block_size);
1665
blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
1667
mutex_lock(&inode->i_mutex);
1668
inode->i_flags &= ~S_SWAPFILE;
1669
mutex_unlock(&inode->i_mutex);
1671
filp_close(swap_file, NULL);
1673
atomic_inc(&proc_poll_event);
1674
wake_up_interruptible(&proc_poll_wait);
1677
filp_close(victim, NULL);
1682
#ifdef CONFIG_PROC_FS
1683
static unsigned swaps_poll(struct file *file, poll_table *wait)
1685
struct seq_file *seq = file->private_data;
1687
poll_wait(file, &proc_poll_wait, wait);
1689
if (seq->poll_event != atomic_read(&proc_poll_event)) {
1690
seq->poll_event = atomic_read(&proc_poll_event);
1691
return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
1694
return POLLIN | POLLRDNORM;
1698
static void *swap_start(struct seq_file *swap, loff_t *pos)
1700
struct swap_info_struct *si;
1704
mutex_lock(&swapon_mutex);
1707
return SEQ_START_TOKEN;
1709
for (type = 0; type < nr_swapfiles; type++) {
1710
smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1711
si = swap_info[type];
1712
if (!(si->flags & SWP_USED) || !si->swap_map)
1721
static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1723
struct swap_info_struct *si = v;
1726
if (v == SEQ_START_TOKEN)
1729
type = si->type + 1;
1731
for (; type < nr_swapfiles; type++) {
1732
smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1733
si = swap_info[type];
1734
if (!(si->flags & SWP_USED) || !si->swap_map)
1743
static void swap_stop(struct seq_file *swap, void *v)
1745
mutex_unlock(&swapon_mutex);
1748
static int swap_show(struct seq_file *swap, void *v)
1750
struct swap_info_struct *si = v;
1754
if (si == SEQ_START_TOKEN) {
1755
seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1759
file = si->swap_file;
1760
len = seq_path(swap, &file->f_path, " \t\n\\");
1761
seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1762
len < 40 ? 40 - len : 1, " ",
1763
S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1764
"partition" : "file\t",
1765
si->pages << (PAGE_SHIFT - 10),
1766
si->inuse_pages << (PAGE_SHIFT - 10),
1771
static const struct seq_operations swaps_op = {
1772
.start = swap_start,
1778
static int swaps_open(struct inode *inode, struct file *file)
1780
struct seq_file *seq;
1783
ret = seq_open(file, &swaps_op);
1787
seq = file->private_data;
1788
seq->poll_event = atomic_read(&proc_poll_event);
1792
static const struct file_operations proc_swaps_operations = {
1795
.llseek = seq_lseek,
1796
.release = seq_release,
1800
static int __init procswaps_init(void)
1802
proc_create("swaps", 0, NULL, &proc_swaps_operations);
1805
__initcall(procswaps_init);
1806
#endif /* CONFIG_PROC_FS */
1808
#ifdef MAX_SWAPFILES_CHECK
1809
static int __init max_swapfiles_check(void)
1811
MAX_SWAPFILES_CHECK();
1814
late_initcall(max_swapfiles_check);
1817
static struct swap_info_struct *alloc_swap_info(void)
1819
struct swap_info_struct *p;
1822
p = kzalloc(sizeof(*p), GFP_KERNEL);
1824
return ERR_PTR(-ENOMEM);
1826
spin_lock(&swap_lock);
1827
for (type = 0; type < nr_swapfiles; type++) {
1828
if (!(swap_info[type]->flags & SWP_USED))
1831
if (type >= MAX_SWAPFILES) {
1832
spin_unlock(&swap_lock);
1834
return ERR_PTR(-EPERM);
1836
if (type >= nr_swapfiles) {
1838
swap_info[type] = p;
1840
* Write swap_info[type] before nr_swapfiles, in case a
1841
* racing procfs swap_start() or swap_next() is reading them.
1842
* (We never shrink nr_swapfiles, we never free this entry.)
1848
p = swap_info[type];
1850
* Do not memset this entry: a racing procfs swap_next()
1851
* would be relying on p->type to remain valid.
1854
INIT_LIST_HEAD(&p->first_swap_extent.list);
1855
p->flags = SWP_USED;
1857
spin_unlock(&swap_lock);
1862
static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
1866
if (S_ISBLK(inode->i_mode)) {
1867
p->bdev = bdgrab(I_BDEV(inode));
1868
error = blkdev_get(p->bdev,
1869
FMODE_READ | FMODE_WRITE | FMODE_EXCL,
1875
p->old_block_size = block_size(p->bdev);
1876
error = set_blocksize(p->bdev, PAGE_SIZE);
1879
p->flags |= SWP_BLKDEV;
1880
} else if (S_ISREG(inode->i_mode)) {
1881
p->bdev = inode->i_sb->s_bdev;
1882
mutex_lock(&inode->i_mutex);
1883
if (IS_SWAPFILE(inode))
1891
static unsigned long read_swap_header(struct swap_info_struct *p,
1892
union swap_header *swap_header,
1893
struct inode *inode)
1896
unsigned long maxpages;
1897
unsigned long swapfilepages;
1899
if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1900
printk(KERN_ERR "Unable to find swap-space signature\n");
1904
/* swap partition endianess hack... */
1905
if (swab32(swap_header->info.version) == 1) {
1906
swab32s(&swap_header->info.version);
1907
swab32s(&swap_header->info.last_page);
1908
swab32s(&swap_header->info.nr_badpages);
1909
for (i = 0; i < swap_header->info.nr_badpages; i++)
1910
swab32s(&swap_header->info.badpages[i]);
1912
/* Check the swap header's sub-version */
1913
if (swap_header->info.version != 1) {
1915
"Unable to handle swap header version %d\n",
1916
swap_header->info.version);
1921
p->cluster_next = 1;
1925
* Find out how many pages are allowed for a single swap
1926
* device. There are three limiting factors: 1) the number
1927
* of bits for the swap offset in the swp_entry_t type, and
1928
* 2) the number of bits in the swap pte as defined by the
1929
* the different architectures, and 3) the number of free bits
1930
* in an exceptional radix_tree entry. In order to find the
1931
* largest possible bit mask, a swap entry with swap type 0
1932
* and swap offset ~0UL is created, encoded to a swap pte,
1933
* decoded to a swp_entry_t again, and finally the swap
1934
* offset is extracted. This will mask all the bits from
1935
* the initial ~0UL mask that can't be encoded in either
1936
* the swp_entry_t or the architecture definition of a
1937
* swap pte. Then the same is done for a radix_tree entry.
1939
maxpages = swp_offset(pte_to_swp_entry(
1940
swp_entry_to_pte(swp_entry(0, ~0UL))));
1941
maxpages = swp_offset(radix_to_swp_entry(
1942
swp_to_radix_entry(swp_entry(0, maxpages)))) + 1;
1944
if (maxpages > swap_header->info.last_page) {
1945
maxpages = swap_header->info.last_page + 1;
1946
/* p->max is an unsigned int: don't overflow it */
1947
if ((unsigned int)maxpages == 0)
1948
maxpages = UINT_MAX;
1950
p->highest_bit = maxpages - 1;
1954
swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1955
if (swapfilepages && maxpages > swapfilepages) {
1957
"Swap area shorter than signature indicates\n");
1960
if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1962
if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1968
static int setup_swap_map_and_extents(struct swap_info_struct *p,
1969
union swap_header *swap_header,
1970
unsigned char *swap_map,
1971
unsigned long maxpages,
1975
unsigned int nr_good_pages;
1978
nr_good_pages = maxpages - 1; /* omit header page */
1980
for (i = 0; i < swap_header->info.nr_badpages; i++) {
1981
unsigned int page_nr = swap_header->info.badpages[i];
1982
if (page_nr == 0 || page_nr > swap_header->info.last_page)
1984
if (page_nr < maxpages) {
1985
swap_map[page_nr] = SWAP_MAP_BAD;
1990
if (nr_good_pages) {
1991
swap_map[0] = SWAP_MAP_BAD;
1993
p->pages = nr_good_pages;
1994
nr_extents = setup_swap_extents(p, span);
1997
nr_good_pages = p->pages;
1999
if (!nr_good_pages) {
2000
printk(KERN_WARNING "Empty swap-file\n");
2007
SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2009
struct swap_info_struct *p;
2011
struct file *swap_file = NULL;
2012
struct address_space *mapping;
2016
union swap_header *swap_header;
2019
unsigned long maxpages;
2020
unsigned char *swap_map = NULL;
2021
struct page *page = NULL;
2022
struct inode *inode = NULL;
2024
if (!capable(CAP_SYS_ADMIN))
2027
p = alloc_swap_info();
2031
name = getname(specialfile);
2033
error = PTR_ERR(name);
2037
swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
2038
if (IS_ERR(swap_file)) {
2039
error = PTR_ERR(swap_file);
2044
p->swap_file = swap_file;
2045
mapping = swap_file->f_mapping;
2047
for (i = 0; i < nr_swapfiles; i++) {
2048
struct swap_info_struct *q = swap_info[i];
2050
if (q == p || !q->swap_file)
2052
if (mapping == q->swap_file->f_mapping) {
2058
inode = mapping->host;
2059
/* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */
2060
error = claim_swapfile(p, inode);
2061
if (unlikely(error))
2065
* Read the swap header.
2067
if (!mapping->a_ops->readpage) {
2071
page = read_mapping_page(mapping, 0, swap_file);
2073
error = PTR_ERR(page);
2076
swap_header = kmap(page);
2078
maxpages = read_swap_header(p, swap_header, inode);
2079
if (unlikely(!maxpages)) {
2084
/* OK, set up the swap map and apply the bad block list */
2085
swap_map = vzalloc(maxpages);
2091
error = swap_cgroup_swapon(p->type, maxpages);
2095
nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
2097
if (unlikely(nr_extents < 0)) {
2103
if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2104
p->flags |= SWP_SOLIDSTATE;
2105
p->cluster_next = 1 + (random32() % p->highest_bit);
2107
if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
2108
p->flags |= SWP_DISCARDABLE;
2111
mutex_lock(&swapon_mutex);
2113
if (swap_flags & SWAP_FLAG_PREFER)
2115
(swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2116
enable_swap_info(p, prio, swap_map);
2118
printk(KERN_INFO "Adding %uk swap on %s. "
2119
"Priority:%d extents:%d across:%lluk %s%s\n",
2120
p->pages<<(PAGE_SHIFT-10), name, p->prio,
2121
nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2122
(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2123
(p->flags & SWP_DISCARDABLE) ? "D" : "");
2125
mutex_unlock(&swapon_mutex);
2126
atomic_inc(&proc_poll_event);
2127
wake_up_interruptible(&proc_poll_wait);
2129
if (S_ISREG(inode->i_mode))
2130
inode->i_flags |= S_SWAPFILE;
2134
if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
2135
set_blocksize(p->bdev, p->old_block_size);
2136
blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2138
destroy_swap_extents(p);
2139
swap_cgroup_swapoff(p->type);
2140
spin_lock(&swap_lock);
2141
p->swap_file = NULL;
2143
spin_unlock(&swap_lock);
2146
if (inode && S_ISREG(inode->i_mode)) {
2147
mutex_unlock(&inode->i_mutex);
2150
filp_close(swap_file, NULL);
2153
if (page && !IS_ERR(page)) {
2155
page_cache_release(page);
2159
if (inode && S_ISREG(inode->i_mode))
2160
mutex_unlock(&inode->i_mutex);
2164
void si_swapinfo(struct sysinfo *val)
2167
unsigned long nr_to_be_unused = 0;
2169
spin_lock(&swap_lock);
2170
for (type = 0; type < nr_swapfiles; type++) {
2171
struct swap_info_struct *si = swap_info[type];
2173
if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2174
nr_to_be_unused += si->inuse_pages;
2176
val->freeswap = nr_swap_pages + nr_to_be_unused;
2177
val->totalswap = total_swap_pages + nr_to_be_unused;
2178
spin_unlock(&swap_lock);
2182
* Verify that a swap entry is valid and increment its swap map count.
2184
* Returns error code in following case.
2186
* - swp_entry is invalid -> EINVAL
2187
* - swp_entry is migration entry -> EINVAL
2188
* - swap-cache reference is requested but there is already one. -> EEXIST
2189
* - swap-cache reference is requested but the entry is not used. -> ENOENT
2190
* - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2192
static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2194
struct swap_info_struct *p;
2195
unsigned long offset, type;
2196
unsigned char count;
2197
unsigned char has_cache;
2200
if (non_swap_entry(entry))
2203
type = swp_type(entry);
2204
if (type >= nr_swapfiles)
2206
p = swap_info[type];
2207
offset = swp_offset(entry);
2209
spin_lock(&swap_lock);
2210
if (unlikely(offset >= p->max))
2213
count = p->swap_map[offset];
2214
has_cache = count & SWAP_HAS_CACHE;
2215
count &= ~SWAP_HAS_CACHE;
2218
if (usage == SWAP_HAS_CACHE) {
2220
/* set SWAP_HAS_CACHE if there is no cache and entry is used */
2221
if (!has_cache && count)
2222
has_cache = SWAP_HAS_CACHE;
2223
else if (has_cache) /* someone else added cache */
2225
else /* no users remaining */
2228
} else if (count || has_cache) {
2230
if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2232
else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2234
else if (swap_count_continued(p, offset, count))
2235
count = COUNT_CONTINUED;
2239
err = -ENOENT; /* unused swap entry */
2241
p->swap_map[offset] = count | has_cache;
2244
spin_unlock(&swap_lock);
2249
printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2254
* Help swapoff by noting that swap entry belongs to shmem/tmpfs
2255
* (in which case its reference count is never incremented).
2257
void swap_shmem_alloc(swp_entry_t entry)
2259
__swap_duplicate(entry, SWAP_MAP_SHMEM);
2263
* Increase reference count of swap entry by 1.
2264
* Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2265
* but could not be atomically allocated. Returns 0, just as if it succeeded,
2266
* if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2267
* might occur if a page table entry has got corrupted.
2269
int swap_duplicate(swp_entry_t entry)
2273
while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2274
err = add_swap_count_continuation(entry, GFP_ATOMIC);
2279
* @entry: swap entry for which we allocate swap cache.
2281
* Called when allocating swap cache for existing swap entry,
2282
* This can return error codes. Returns 0 at success.
2283
* -EBUSY means there is a swap cache.
2284
* Note: return code is different from swap_duplicate().
2286
int swapcache_prepare(swp_entry_t entry)
2288
return __swap_duplicate(entry, SWAP_HAS_CACHE);
2292
* swap_lock prevents swap_map being freed. Don't grab an extra
2293
* reference on the swaphandle, it doesn't matter if it becomes unused.
2295
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2297
struct swap_info_struct *si;
2298
int our_page_cluster = page_cluster;
2299
pgoff_t target, toff;
2303
if (!our_page_cluster) /* no readahead */
2306
si = swap_info[swp_type(entry)];
2307
target = swp_offset(entry);
2308
base = (target >> our_page_cluster) << our_page_cluster;
2309
end = base + (1 << our_page_cluster);
2310
if (!base) /* first page is swap header */
2313
spin_lock(&swap_lock);
2314
if (end > si->max) /* don't go beyond end of map */
2317
/* Count contiguous allocated slots above our target */
2318
for (toff = target; ++toff < end; nr_pages++) {
2319
/* Don't read in free or bad pages */
2320
if (!si->swap_map[toff])
2322
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2325
/* Count contiguous allocated slots below our target */
2326
for (toff = target; --toff >= base; nr_pages++) {
2327
/* Don't read in free or bad pages */
2328
if (!si->swap_map[toff])
2330
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2333
spin_unlock(&swap_lock);
2336
* Indicate starting offset, and return number of pages to get:
2337
* if only 1, say 0, since there's then no readahead to be done.
2340
return nr_pages? ++nr_pages: 0;
2344
* add_swap_count_continuation - called when a swap count is duplicated
2345
* beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2346
* page of the original vmalloc'ed swap_map, to hold the continuation count
2347
* (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2348
* again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2350
* These continuation pages are seldom referenced: the common paths all work
2351
* on the original swap_map, only referring to a continuation page when the
2352
* low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2354
* add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2355
* page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2356
* can be called after dropping locks.
2358
int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2360
struct swap_info_struct *si;
2363
struct page *list_page;
2365
unsigned char count;
2368
* When debugging, it's easier to use __GFP_ZERO here; but it's better
2369
* for latency not to zero a page while GFP_ATOMIC and holding locks.
2371
page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2373
si = swap_info_get(entry);
2376
* An acceptable race has occurred since the failing
2377
* __swap_duplicate(): the swap entry has been freed,
2378
* perhaps even the whole swap_map cleared for swapoff.
2383
offset = swp_offset(entry);
2384
count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2386
if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2388
* The higher the swap count, the more likely it is that tasks
2389
* will race to add swap count continuation: we need to avoid
2390
* over-provisioning.
2396
spin_unlock(&swap_lock);
2401
* We are fortunate that although vmalloc_to_page uses pte_offset_map,
2402
* no architecture is using highmem pages for kernel pagetables: so it
2403
* will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2405
head = vmalloc_to_page(si->swap_map + offset);
2406
offset &= ~PAGE_MASK;
2409
* Page allocation does not initialize the page's lru field,
2410
* but it does always reset its private field.
2412
if (!page_private(head)) {
2413
BUG_ON(count & COUNT_CONTINUED);
2414
INIT_LIST_HEAD(&head->lru);
2415
set_page_private(head, SWP_CONTINUED);
2416
si->flags |= SWP_CONTINUED;
2419
list_for_each_entry(list_page, &head->lru, lru) {
2423
* If the previous map said no continuation, but we've found
2424
* a continuation page, free our allocation and use this one.
2426
if (!(count & COUNT_CONTINUED))
2429
map = kmap_atomic(list_page, KM_USER0) + offset;
2431
kunmap_atomic(map, KM_USER0);
2434
* If this continuation count now has some space in it,
2435
* free our allocation and use this one.
2437
if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2441
list_add_tail(&page->lru, &head->lru);
2442
page = NULL; /* now it's attached, don't free it */
2444
spin_unlock(&swap_lock);
2452
* swap_count_continued - when the original swap_map count is incremented
2453
* from SWAP_MAP_MAX, check if there is already a continuation page to carry
2454
* into, carry if so, or else fail until a new continuation page is allocated;
2455
* when the original swap_map count is decremented from 0 with continuation,
2456
* borrow from the continuation and report whether it still holds more.
2457
* Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2459
static bool swap_count_continued(struct swap_info_struct *si,
2460
pgoff_t offset, unsigned char count)
2466
head = vmalloc_to_page(si->swap_map + offset);
2467
if (page_private(head) != SWP_CONTINUED) {
2468
BUG_ON(count & COUNT_CONTINUED);
2469
return false; /* need to add count continuation */
2472
offset &= ~PAGE_MASK;
2473
page = list_entry(head->lru.next, struct page, lru);
2474
map = kmap_atomic(page, KM_USER0) + offset;
2476
if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2477
goto init_map; /* jump over SWAP_CONT_MAX checks */
2479
if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2481
* Think of how you add 1 to 999
2483
while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2484
kunmap_atomic(map, KM_USER0);
2485
page = list_entry(page->lru.next, struct page, lru);
2486
BUG_ON(page == head);
2487
map = kmap_atomic(page, KM_USER0) + offset;
2489
if (*map == SWAP_CONT_MAX) {
2490
kunmap_atomic(map, KM_USER0);
2491
page = list_entry(page->lru.next, struct page, lru);
2493
return false; /* add count continuation */
2494
map = kmap_atomic(page, KM_USER0) + offset;
2495
init_map: *map = 0; /* we didn't zero the page */
2498
kunmap_atomic(map, KM_USER0);
2499
page = list_entry(page->lru.prev, struct page, lru);
2500
while (page != head) {
2501
map = kmap_atomic(page, KM_USER0) + offset;
2502
*map = COUNT_CONTINUED;
2503
kunmap_atomic(map, KM_USER0);
2504
page = list_entry(page->lru.prev, struct page, lru);
2506
return true; /* incremented */
2508
} else { /* decrementing */
2510
* Think of how you subtract 1 from 1000
2512
BUG_ON(count != COUNT_CONTINUED);
2513
while (*map == COUNT_CONTINUED) {
2514
kunmap_atomic(map, KM_USER0);
2515
page = list_entry(page->lru.next, struct page, lru);
2516
BUG_ON(page == head);
2517
map = kmap_atomic(page, KM_USER0) + offset;
2523
kunmap_atomic(map, KM_USER0);
2524
page = list_entry(page->lru.prev, struct page, lru);
2525
while (page != head) {
2526
map = kmap_atomic(page, KM_USER0) + offset;
2527
*map = SWAP_CONT_MAX | count;
2528
count = COUNT_CONTINUED;
2529
kunmap_atomic(map, KM_USER0);
2530
page = list_entry(page->lru.prev, struct page, lru);
2532
return count == COUNT_CONTINUED;
2537
* free_swap_count_continuations - swapoff free all the continuation pages
2538
* appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2540
static void free_swap_count_continuations(struct swap_info_struct *si)
2544
for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2546
head = vmalloc_to_page(si->swap_map + offset);
2547
if (page_private(head)) {
2548
struct list_head *this, *next;
2549
list_for_each_safe(this, next, &head->lru) {
2551
page = list_entry(this, struct page, lru);