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
);
57 * We need this because the bdev->unplug_fn can sleep and we cannot
58 * hold swap_lock while calling the unplug_fn. And swap_lock
59 * cannot be turned into a mutex.
61 static DECLARE_RWSEM(swap_unplug_sem
);
63 void swap_unplug_io_fn(struct backing_dev_info
*unused_bdi
, struct page
*page
)
67 down_read(&swap_unplug_sem
);
68 entry
.val
= page_private(page
);
69 if (PageSwapCache(page
)) {
70 struct block_device
*bdev
= swap_info
[swp_type(entry
)].bdev
;
71 struct backing_dev_info
*bdi
;
74 * If the page is removed from swapcache from under us (with a
75 * racy try_to_unuse/swapoff) we need an additional reference
76 * count to avoid reading garbage from page_private(page) above.
77 * If the WARN_ON triggers during a swapoff it maybe the race
78 * condition and it's harmless. However if it triggers without
79 * swapoff it signals a problem.
81 WARN_ON(page_count(page
) <= 1);
83 bdi
= bdev
->bd_inode
->i_mapping
->backing_dev_info
;
84 blk_run_backing_dev(bdi
, page
);
86 up_read(&swap_unplug_sem
);
90 * swapon tell device that all the old swap contents can be discarded,
91 * to allow the swap device to optimize its wear-levelling.
93 static int discard_swap(struct swap_info_struct
*si
)
95 struct swap_extent
*se
;
98 list_for_each_entry(se
, &si
->extent_list
, list
) {
99 sector_t start_block
= se
->start_block
<< (PAGE_SHIFT
- 9);
100 sector_t nr_blocks
= (sector_t
)se
->nr_pages
<< (PAGE_SHIFT
- 9);
102 if (se
->start_page
== 0) {
103 /* Do not discard the swap header page! */
104 start_block
+= 1 << (PAGE_SHIFT
- 9);
105 nr_blocks
-= 1 << (PAGE_SHIFT
- 9);
110 err
= blkdev_issue_discard(si
->bdev
, start_block
,
111 nr_blocks
, GFP_KERNEL
);
117 return err
; /* That will often be -EOPNOTSUPP */
121 * swap allocation tell device that a cluster of swap can now be discarded,
122 * to allow the swap device to optimize its wear-levelling.
124 static void discard_swap_cluster(struct swap_info_struct
*si
,
125 pgoff_t start_page
, pgoff_t nr_pages
)
127 struct swap_extent
*se
= si
->curr_swap_extent
;
128 int found_extent
= 0;
131 struct list_head
*lh
;
133 if (se
->start_page
<= start_page
&&
134 start_page
< se
->start_page
+ se
->nr_pages
) {
135 pgoff_t offset
= start_page
- se
->start_page
;
136 sector_t start_block
= se
->start_block
+ offset
;
137 sector_t nr_blocks
= se
->nr_pages
- offset
;
139 if (nr_blocks
> nr_pages
)
140 nr_blocks
= nr_pages
;
141 start_page
+= nr_blocks
;
142 nr_pages
-= nr_blocks
;
145 si
->curr_swap_extent
= se
;
147 start_block
<<= PAGE_SHIFT
- 9;
148 nr_blocks
<<= PAGE_SHIFT
- 9;
149 if (blkdev_issue_discard(si
->bdev
, start_block
,
150 nr_blocks
, GFP_NOIO
))
155 if (lh
== &si
->extent_list
)
157 se
= list_entry(lh
, struct swap_extent
, list
);
161 static int wait_for_discard(void *word
)
167 #define SWAPFILE_CLUSTER 256
168 #define LATENCY_LIMIT 256
170 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
)
172 unsigned long offset
;
173 unsigned long scan_base
;
174 unsigned long last_in_cluster
= 0;
175 int latency_ration
= LATENCY_LIMIT
;
176 int found_free_cluster
= 0;
179 * We try to cluster swap pages by allocating them sequentially
180 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
181 * way, however, we resort to first-free allocation, starting
182 * a new cluster. This prevents us from scattering swap pages
183 * all over the entire swap partition, so that we reduce
184 * overall disk seek times between swap pages. -- sct
185 * But we do now try to find an empty cluster. -Andrea
186 * And we let swap pages go all over an SSD partition. Hugh
189 si
->flags
+= SWP_SCANNING
;
190 scan_base
= offset
= si
->cluster_next
;
192 if (unlikely(!si
->cluster_nr
--)) {
193 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
) {
194 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
197 if (si
->flags
& SWP_DISCARDABLE
) {
199 * Start range check on racing allocations, in case
200 * they overlap the cluster we eventually decide on
201 * (we scan without swap_lock to allow preemption).
202 * It's hardly conceivable that cluster_nr could be
203 * wrapped during our scan, but don't depend on it.
205 if (si
->lowest_alloc
)
207 si
->lowest_alloc
= si
->max
;
208 si
->highest_alloc
= 0;
210 spin_unlock(&swap_lock
);
213 * If seek is expensive, start searching for new cluster from
214 * start of partition, to minimize the span of allocated swap.
215 * But if seek is cheap, search from our current position, so
216 * that swap is allocated from all over the partition: if the
217 * Flash Translation Layer only remaps within limited zones,
218 * we don't want to wear out the first zone too quickly.
220 if (!(si
->flags
& SWP_SOLIDSTATE
))
221 scan_base
= offset
= si
->lowest_bit
;
222 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
224 /* Locate the first empty (unaligned) cluster */
225 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
226 if (si
->swap_map
[offset
])
227 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
228 else if (offset
== last_in_cluster
) {
229 spin_lock(&swap_lock
);
230 offset
-= SWAPFILE_CLUSTER
- 1;
231 si
->cluster_next
= offset
;
232 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
233 found_free_cluster
= 1;
236 if (unlikely(--latency_ration
< 0)) {
238 latency_ration
= LATENCY_LIMIT
;
242 offset
= si
->lowest_bit
;
243 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
245 /* Locate the first empty (unaligned) cluster */
246 for (; last_in_cluster
< scan_base
; offset
++) {
247 if (si
->swap_map
[offset
])
248 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
249 else if (offset
== last_in_cluster
) {
250 spin_lock(&swap_lock
);
251 offset
-= SWAPFILE_CLUSTER
- 1;
252 si
->cluster_next
= offset
;
253 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
254 found_free_cluster
= 1;
257 if (unlikely(--latency_ration
< 0)) {
259 latency_ration
= LATENCY_LIMIT
;
264 spin_lock(&swap_lock
);
265 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
266 si
->lowest_alloc
= 0;
270 if (!(si
->flags
& SWP_WRITEOK
))
272 if (!si
->highest_bit
)
274 if (offset
> si
->highest_bit
)
275 scan_base
= offset
= si
->lowest_bit
;
276 if (si
->swap_map
[offset
])
279 if (offset
== si
->lowest_bit
)
281 if (offset
== si
->highest_bit
)
284 if (si
->inuse_pages
== si
->pages
) {
285 si
->lowest_bit
= si
->max
;
288 si
->swap_map
[offset
] = 1;
289 si
->cluster_next
= offset
+ 1;
290 si
->flags
-= SWP_SCANNING
;
292 if (si
->lowest_alloc
) {
294 * Only set when SWP_DISCARDABLE, and there's a scan
295 * for a free cluster in progress or just completed.
297 if (found_free_cluster
) {
299 * To optimize wear-levelling, discard the
300 * old data of the cluster, taking care not to
301 * discard any of its pages that have already
302 * been allocated by racing tasks (offset has
303 * already stepped over any at the beginning).
305 if (offset
< si
->highest_alloc
&&
306 si
->lowest_alloc
<= last_in_cluster
)
307 last_in_cluster
= si
->lowest_alloc
- 1;
308 si
->flags
|= SWP_DISCARDING
;
309 spin_unlock(&swap_lock
);
311 if (offset
< last_in_cluster
)
312 discard_swap_cluster(si
, offset
,
313 last_in_cluster
- offset
+ 1);
315 spin_lock(&swap_lock
);
316 si
->lowest_alloc
= 0;
317 si
->flags
&= ~SWP_DISCARDING
;
319 smp_mb(); /* wake_up_bit advises this */
320 wake_up_bit(&si
->flags
, ilog2(SWP_DISCARDING
));
322 } else if (si
->flags
& SWP_DISCARDING
) {
324 * Delay using pages allocated by racing tasks
325 * until the whole discard has been issued. We
326 * could defer that delay until swap_writepage,
327 * but it's easier to keep this self-contained.
329 spin_unlock(&swap_lock
);
330 wait_on_bit(&si
->flags
, ilog2(SWP_DISCARDING
),
331 wait_for_discard
, TASK_UNINTERRUPTIBLE
);
332 spin_lock(&swap_lock
);
335 * Note pages allocated by racing tasks while
336 * scan for a free cluster is in progress, so
337 * that its final discard can exclude them.
339 if (offset
< si
->lowest_alloc
)
340 si
->lowest_alloc
= offset
;
341 if (offset
> si
->highest_alloc
)
342 si
->highest_alloc
= offset
;
348 spin_unlock(&swap_lock
);
349 while (++offset
<= si
->highest_bit
) {
350 if (!si
->swap_map
[offset
]) {
351 spin_lock(&swap_lock
);
354 if (unlikely(--latency_ration
< 0)) {
356 latency_ration
= LATENCY_LIMIT
;
359 offset
= si
->lowest_bit
;
360 while (++offset
< scan_base
) {
361 if (!si
->swap_map
[offset
]) {
362 spin_lock(&swap_lock
);
365 if (unlikely(--latency_ration
< 0)) {
367 latency_ration
= LATENCY_LIMIT
;
370 spin_lock(&swap_lock
);
373 si
->flags
-= SWP_SCANNING
;
377 swp_entry_t
get_swap_page(void)
379 struct swap_info_struct
*si
;
384 spin_lock(&swap_lock
);
385 if (nr_swap_pages
<= 0)
389 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
390 si
= swap_info
+ type
;
393 (!wrapped
&& si
->prio
!= swap_info
[next
].prio
)) {
394 next
= swap_list
.head
;
398 if (!si
->highest_bit
)
400 if (!(si
->flags
& SWP_WRITEOK
))
403 swap_list
.next
= next
;
404 offset
= scan_swap_map(si
);
406 spin_unlock(&swap_lock
);
407 return swp_entry(type
, offset
);
409 next
= swap_list
.next
;
414 spin_unlock(&swap_lock
);
415 return (swp_entry_t
) {0};
418 swp_entry_t
get_swap_page_of_type(int type
)
420 struct swap_info_struct
*si
;
423 spin_lock(&swap_lock
);
424 si
= swap_info
+ type
;
425 if (si
->flags
& SWP_WRITEOK
) {
427 offset
= scan_swap_map(si
);
429 spin_unlock(&swap_lock
);
430 return swp_entry(type
, offset
);
434 spin_unlock(&swap_lock
);
435 return (swp_entry_t
) {0};
438 static struct swap_info_struct
* swap_info_get(swp_entry_t entry
)
440 struct swap_info_struct
* p
;
441 unsigned long offset
, type
;
445 type
= swp_type(entry
);
446 if (type
>= nr_swapfiles
)
448 p
= & swap_info
[type
];
449 if (!(p
->flags
& SWP_USED
))
451 offset
= swp_offset(entry
);
452 if (offset
>= p
->max
)
454 if (!p
->swap_map
[offset
])
456 spin_lock(&swap_lock
);
460 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
463 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
466 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
469 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
474 static int swap_entry_free(struct swap_info_struct
*p
, swp_entry_t ent
)
476 unsigned long offset
= swp_offset(ent
);
477 int count
= p
->swap_map
[offset
];
479 if (count
< SWAP_MAP_MAX
) {
481 p
->swap_map
[offset
] = count
;
483 if (offset
< p
->lowest_bit
)
484 p
->lowest_bit
= offset
;
485 if (offset
> p
->highest_bit
)
486 p
->highest_bit
= offset
;
487 if (p
->prio
> swap_info
[swap_list
.next
].prio
)
488 swap_list
.next
= p
- swap_info
;
491 mem_cgroup_uncharge_swap(ent
);
498 * Caller has made sure that the swapdevice corresponding to entry
499 * is still around or has not been recycled.
501 void swap_free(swp_entry_t entry
)
503 struct swap_info_struct
* p
;
505 p
= swap_info_get(entry
);
507 swap_entry_free(p
, entry
);
508 spin_unlock(&swap_lock
);
513 * How many references to page are currently swapped out?
515 static inline int page_swapcount(struct page
*page
)
518 struct swap_info_struct
*p
;
521 entry
.val
= page_private(page
);
522 p
= swap_info_get(entry
);
524 /* Subtract the 1 for the swap cache itself */
525 count
= p
->swap_map
[swp_offset(entry
)] - 1;
526 spin_unlock(&swap_lock
);
532 * We can write to an anon page without COW if there are no other references
533 * to it. And as a side-effect, free up its swap: because the old content
534 * on disk will never be read, and seeking back there to write new content
535 * later would only waste time away from clustering.
537 int reuse_swap_page(struct page
*page
)
541 VM_BUG_ON(!PageLocked(page
));
542 count
= page_mapcount(page
);
543 if (count
<= 1 && PageSwapCache(page
)) {
544 count
+= page_swapcount(page
);
545 if (count
== 1 && !PageWriteback(page
)) {
546 delete_from_swap_cache(page
);
554 * If swap is getting full, or if there are no more mappings of this page,
555 * then try_to_free_swap is called to free its swap space.
557 int try_to_free_swap(struct page
*page
)
559 VM_BUG_ON(!PageLocked(page
));
561 if (!PageSwapCache(page
))
563 if (PageWriteback(page
))
565 if (page_swapcount(page
))
568 delete_from_swap_cache(page
);
574 * Free the swap entry like above, but also try to
575 * free the page cache entry if it is the last user.
577 int free_swap_and_cache(swp_entry_t entry
)
579 struct swap_info_struct
*p
;
580 struct page
*page
= NULL
;
582 if (is_migration_entry(entry
))
585 p
= swap_info_get(entry
);
587 if (swap_entry_free(p
, entry
) == 1) {
588 page
= find_get_page(&swapper_space
, entry
.val
);
589 if (page
&& !trylock_page(page
)) {
590 page_cache_release(page
);
594 spin_unlock(&swap_lock
);
598 * Not mapped elsewhere, or swap space full? Free it!
599 * Also recheck PageSwapCache now page is locked (above).
601 if (PageSwapCache(page
) && !PageWriteback(page
) &&
602 (!page_mapped(page
) || vm_swap_full())) {
603 delete_from_swap_cache(page
);
607 page_cache_release(page
);
612 #ifdef CONFIG_HIBERNATION
614 * Find the swap type that corresponds to given device (if any).
616 * @offset - number of the PAGE_SIZE-sized block of the device, starting
617 * from 0, in which the swap header is expected to be located.
619 * This is needed for the suspend to disk (aka swsusp).
621 int swap_type_of(dev_t device
, sector_t offset
, struct block_device
**bdev_p
)
623 struct block_device
*bdev
= NULL
;
627 bdev
= bdget(device
);
629 spin_lock(&swap_lock
);
630 for (i
= 0; i
< nr_swapfiles
; i
++) {
631 struct swap_info_struct
*sis
= swap_info
+ i
;
633 if (!(sis
->flags
& SWP_WRITEOK
))
640 spin_unlock(&swap_lock
);
643 if (bdev
== sis
->bdev
) {
644 struct swap_extent
*se
;
646 se
= list_entry(sis
->extent_list
.next
,
647 struct swap_extent
, list
);
648 if (se
->start_block
== offset
) {
652 spin_unlock(&swap_lock
);
658 spin_unlock(&swap_lock
);
666 * Return either the total number of swap pages of given type, or the number
667 * of free pages of that type (depending on @free)
669 * This is needed for software suspend
671 unsigned int count_swap_pages(int type
, int free
)
675 if (type
< nr_swapfiles
) {
676 spin_lock(&swap_lock
);
677 if (swap_info
[type
].flags
& SWP_WRITEOK
) {
678 n
= swap_info
[type
].pages
;
680 n
-= swap_info
[type
].inuse_pages
;
682 spin_unlock(&swap_lock
);
689 * No need to decide whether this PTE shares the swap entry with others,
690 * just let do_wp_page work it out if a write is requested later - to
691 * force COW, vm_page_prot omits write permission from any private vma.
693 static int unuse_pte(struct vm_area_struct
*vma
, pmd_t
*pmd
,
694 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
696 struct mem_cgroup
*ptr
= NULL
;
701 if (mem_cgroup_try_charge_swapin(vma
->vm_mm
, page
, GFP_KERNEL
, &ptr
))
704 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
705 if (unlikely(!pte_same(*pte
, swp_entry_to_pte(entry
)))) {
707 mem_cgroup_cancel_charge_swapin(ptr
);
712 inc_mm_counter(vma
->vm_mm
, anon_rss
);
714 set_pte_at(vma
->vm_mm
, addr
, pte
,
715 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
716 page_add_anon_rmap(page
, vma
, addr
);
717 mem_cgroup_commit_charge_swapin(page
, ptr
);
720 * Move the page to the active list so it is not
721 * immediately swapped out again after swapon.
725 pte_unmap_unlock(pte
, ptl
);
729 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
730 unsigned long addr
, unsigned long end
,
731 swp_entry_t entry
, struct page
*page
)
733 pte_t swp_pte
= swp_entry_to_pte(entry
);
738 * We don't actually need pte lock while scanning for swp_pte: since
739 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
740 * page table while we're scanning; though it could get zapped, and on
741 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
742 * of unmatched parts which look like swp_pte, so unuse_pte must
743 * recheck under pte lock. Scanning without pte lock lets it be
744 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
746 pte
= pte_offset_map(pmd
, addr
);
749 * swapoff spends a _lot_ of time in this loop!
750 * Test inline before going to call unuse_pte.
752 if (unlikely(pte_same(*pte
, swp_pte
))) {
754 ret
= unuse_pte(vma
, pmd
, addr
, entry
, page
);
757 pte
= pte_offset_map(pmd
, addr
);
759 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
765 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
766 unsigned long addr
, unsigned long end
,
767 swp_entry_t entry
, struct page
*page
)
773 pmd
= pmd_offset(pud
, addr
);
775 next
= pmd_addr_end(addr
, end
);
776 if (pmd_none_or_clear_bad(pmd
))
778 ret
= unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
);
781 } while (pmd
++, addr
= next
, addr
!= end
);
785 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
786 unsigned long addr
, unsigned long end
,
787 swp_entry_t entry
, struct page
*page
)
793 pud
= pud_offset(pgd
, addr
);
795 next
= pud_addr_end(addr
, end
);
796 if (pud_none_or_clear_bad(pud
))
798 ret
= unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
);
801 } while (pud
++, addr
= next
, addr
!= end
);
805 static int unuse_vma(struct vm_area_struct
*vma
,
806 swp_entry_t entry
, struct page
*page
)
809 unsigned long addr
, end
, next
;
813 addr
= page_address_in_vma(page
, vma
);
817 end
= addr
+ PAGE_SIZE
;
819 addr
= vma
->vm_start
;
823 pgd
= pgd_offset(vma
->vm_mm
, addr
);
825 next
= pgd_addr_end(addr
, end
);
826 if (pgd_none_or_clear_bad(pgd
))
828 ret
= unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
);
831 } while (pgd
++, addr
= next
, addr
!= end
);
835 static int unuse_mm(struct mm_struct
*mm
,
836 swp_entry_t entry
, struct page
*page
)
838 struct vm_area_struct
*vma
;
841 if (!down_read_trylock(&mm
->mmap_sem
)) {
843 * Activate page so shrink_inactive_list is unlikely to unmap
844 * its ptes while lock is dropped, so swapoff can make progress.
848 down_read(&mm
->mmap_sem
);
851 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
852 if (vma
->anon_vma
&& (ret
= unuse_vma(vma
, entry
, page
)))
855 up_read(&mm
->mmap_sem
);
856 return (ret
< 0)? ret
: 0;
860 * Scan swap_map from current position to next entry still in use.
861 * Recycle to start on reaching the end, returning 0 when empty.
863 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
866 unsigned int max
= si
->max
;
867 unsigned int i
= prev
;
871 * No need for swap_lock here: we're just looking
872 * for whether an entry is in use, not modifying it; false
873 * hits are okay, and sys_swapoff() has already prevented new
874 * allocations from this area (while holding swap_lock).
883 * No entries in use at top of swap_map,
884 * loop back to start and recheck there.
890 count
= si
->swap_map
[i
];
891 if (count
&& count
!= SWAP_MAP_BAD
)
898 * We completely avoid races by reading each swap page in advance,
899 * and then search for the process using it. All the necessary
900 * page table adjustments can then be made atomically.
902 static int try_to_unuse(unsigned int type
)
904 struct swap_info_struct
* si
= &swap_info
[type
];
905 struct mm_struct
*start_mm
;
906 unsigned short *swap_map
;
907 unsigned short swcount
;
912 int reset_overflow
= 0;
916 * When searching mms for an entry, a good strategy is to
917 * start at the first mm we freed the previous entry from
918 * (though actually we don't notice whether we or coincidence
919 * freed the entry). Initialize this start_mm with a hold.
921 * A simpler strategy would be to start at the last mm we
922 * freed the previous entry from; but that would take less
923 * advantage of mmlist ordering, which clusters forked mms
924 * together, child after parent. If we race with dup_mmap(), we
925 * prefer to resolve parent before child, lest we miss entries
926 * duplicated after we scanned child: using last mm would invert
927 * that. Though it's only a serious concern when an overflowed
928 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
931 atomic_inc(&init_mm
.mm_users
);
934 * Keep on scanning until all entries have gone. Usually,
935 * one pass through swap_map is enough, but not necessarily:
936 * there are races when an instance of an entry might be missed.
938 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
939 if (signal_pending(current
)) {
945 * Get a page for the entry, using the existing swap
946 * cache page if there is one. Otherwise, get a clean
947 * page and read the swap into it.
949 swap_map
= &si
->swap_map
[i
];
950 entry
= swp_entry(type
, i
);
951 page
= read_swap_cache_async(entry
,
952 GFP_HIGHUSER_MOVABLE
, NULL
, 0);
955 * Either swap_duplicate() failed because entry
956 * has been freed independently, and will not be
957 * reused since sys_swapoff() already disabled
958 * allocation from here, or alloc_page() failed.
967 * Don't hold on to start_mm if it looks like exiting.
969 if (atomic_read(&start_mm
->mm_users
) == 1) {
972 atomic_inc(&init_mm
.mm_users
);
976 * Wait for and lock page. When do_swap_page races with
977 * try_to_unuse, do_swap_page can handle the fault much
978 * faster than try_to_unuse can locate the entry. This
979 * apparently redundant "wait_on_page_locked" lets try_to_unuse
980 * defer to do_swap_page in such a case - in some tests,
981 * do_swap_page and try_to_unuse repeatedly compete.
983 wait_on_page_locked(page
);
984 wait_on_page_writeback(page
);
986 wait_on_page_writeback(page
);
989 * Remove all references to entry.
990 * Whenever we reach init_mm, there's no address space
991 * to search, but use it as a reminder to search shmem.
996 if (start_mm
== &init_mm
)
997 shmem
= shmem_unuse(entry
, page
);
999 retval
= unuse_mm(start_mm
, entry
, page
);
1001 if (*swap_map
> 1) {
1002 int set_start_mm
= (*swap_map
>= swcount
);
1003 struct list_head
*p
= &start_mm
->mmlist
;
1004 struct mm_struct
*new_start_mm
= start_mm
;
1005 struct mm_struct
*prev_mm
= start_mm
;
1006 struct mm_struct
*mm
;
1008 atomic_inc(&new_start_mm
->mm_users
);
1009 atomic_inc(&prev_mm
->mm_users
);
1010 spin_lock(&mmlist_lock
);
1011 while (*swap_map
> 1 && !retval
&& !shmem
&&
1012 (p
= p
->next
) != &start_mm
->mmlist
) {
1013 mm
= list_entry(p
, struct mm_struct
, mmlist
);
1014 if (!atomic_inc_not_zero(&mm
->mm_users
))
1016 spin_unlock(&mmlist_lock
);
1022 swcount
= *swap_map
;
1025 else if (mm
== &init_mm
) {
1027 shmem
= shmem_unuse(entry
, page
);
1029 retval
= unuse_mm(mm
, entry
, page
);
1030 if (set_start_mm
&& *swap_map
< swcount
) {
1031 mmput(new_start_mm
);
1032 atomic_inc(&mm
->mm_users
);
1036 spin_lock(&mmlist_lock
);
1038 spin_unlock(&mmlist_lock
);
1041 start_mm
= new_start_mm
;
1044 /* page has already been unlocked and released */
1052 page_cache_release(page
);
1057 * How could swap count reach 0x7fff when the maximum
1058 * pid is 0x7fff, and there's no way to repeat a swap
1059 * page within an mm (except in shmem, where it's the
1060 * shared object which takes the reference count)?
1061 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
1063 * If that's wrong, then we should worry more about
1064 * exit_mmap() and do_munmap() cases described above:
1065 * we might be resetting SWAP_MAP_MAX too early here.
1066 * We know "Undead"s can happen, they're okay, so don't
1067 * report them; but do report if we reset SWAP_MAP_MAX.
1069 if (*swap_map
== SWAP_MAP_MAX
) {
1070 spin_lock(&swap_lock
);
1072 spin_unlock(&swap_lock
);
1077 * If a reference remains (rare), we would like to leave
1078 * the page in the swap cache; but try_to_unmap could
1079 * then re-duplicate the entry once we drop page lock,
1080 * so we might loop indefinitely; also, that page could
1081 * not be swapped out to other storage meanwhile. So:
1082 * delete from cache even if there's another reference,
1083 * after ensuring that the data has been saved to disk -
1084 * since if the reference remains (rarer), it will be
1085 * read from disk into another page. Splitting into two
1086 * pages would be incorrect if swap supported "shared
1087 * private" pages, but they are handled by tmpfs files.
1089 if ((*swap_map
> 1) && PageDirty(page
) && PageSwapCache(page
)) {
1090 struct writeback_control wbc
= {
1091 .sync_mode
= WB_SYNC_NONE
,
1094 swap_writepage(page
, &wbc
);
1096 wait_on_page_writeback(page
);
1100 * It is conceivable that a racing task removed this page from
1101 * swap cache just before we acquired the page lock at the top,
1102 * or while we dropped it in unuse_mm(). The page might even
1103 * be back in swap cache on another swap area: that we must not
1104 * delete, since it may not have been written out to swap yet.
1106 if (PageSwapCache(page
) &&
1107 likely(page_private(page
) == entry
.val
))
1108 delete_from_swap_cache(page
);
1111 * So we could skip searching mms once swap count went
1112 * to 1, we did not mark any present ptes as dirty: must
1113 * mark page dirty so shrink_page_list will preserve it.
1117 page_cache_release(page
);
1120 * Make sure that we aren't completely killing
1121 * interactive performance.
1127 if (reset_overflow
) {
1128 printk(KERN_WARNING
"swapoff: cleared swap entry overflow\n");
1135 * After a successful try_to_unuse, if no swap is now in use, we know
1136 * we can empty the mmlist. swap_lock must be held on entry and exit.
1137 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1138 * added to the mmlist just after page_duplicate - before would be racy.
1140 static void drain_mmlist(void)
1142 struct list_head
*p
, *next
;
1145 for (i
= 0; i
< nr_swapfiles
; i
++)
1146 if (swap_info
[i
].inuse_pages
)
1148 spin_lock(&mmlist_lock
);
1149 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
1151 spin_unlock(&mmlist_lock
);
1155 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1156 * corresponds to page offset `offset'.
1158 sector_t
map_swap_page(struct swap_info_struct
*sis
, pgoff_t offset
)
1160 struct swap_extent
*se
= sis
->curr_swap_extent
;
1161 struct swap_extent
*start_se
= se
;
1164 struct list_head
*lh
;
1166 if (se
->start_page
<= offset
&&
1167 offset
< (se
->start_page
+ se
->nr_pages
)) {
1168 return se
->start_block
+ (offset
- se
->start_page
);
1171 if (lh
== &sis
->extent_list
)
1173 se
= list_entry(lh
, struct swap_extent
, list
);
1174 sis
->curr_swap_extent
= se
;
1175 BUG_ON(se
== start_se
); /* It *must* be present */
1179 #ifdef CONFIG_HIBERNATION
1181 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1182 * corresponding to given index in swap_info (swap type).
1184 sector_t
swapdev_block(int swap_type
, pgoff_t offset
)
1186 struct swap_info_struct
*sis
;
1188 if (swap_type
>= nr_swapfiles
)
1191 sis
= swap_info
+ swap_type
;
1192 return (sis
->flags
& SWP_WRITEOK
) ? map_swap_page(sis
, offset
) : 0;
1194 #endif /* CONFIG_HIBERNATION */
1197 * Free all of a swapdev's extent information
1199 static void destroy_swap_extents(struct swap_info_struct
*sis
)
1201 while (!list_empty(&sis
->extent_list
)) {
1202 struct swap_extent
*se
;
1204 se
= list_entry(sis
->extent_list
.next
,
1205 struct swap_extent
, list
);
1206 list_del(&se
->list
);
1212 * Add a block range (and the corresponding page range) into this swapdev's
1213 * extent list. The extent list is kept sorted in page order.
1215 * This function rather assumes that it is called in ascending page order.
1218 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
1219 unsigned long nr_pages
, sector_t start_block
)
1221 struct swap_extent
*se
;
1222 struct swap_extent
*new_se
;
1223 struct list_head
*lh
;
1225 lh
= sis
->extent_list
.prev
; /* The highest page extent */
1226 if (lh
!= &sis
->extent_list
) {
1227 se
= list_entry(lh
, struct swap_extent
, list
);
1228 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
1229 if (se
->start_block
+ se
->nr_pages
== start_block
) {
1231 se
->nr_pages
+= nr_pages
;
1237 * No merge. Insert a new extent, preserving ordering.
1239 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
1242 new_se
->start_page
= start_page
;
1243 new_se
->nr_pages
= nr_pages
;
1244 new_se
->start_block
= start_block
;
1246 list_add_tail(&new_se
->list
, &sis
->extent_list
);
1251 * A `swap extent' is a simple thing which maps a contiguous range of pages
1252 * onto a contiguous range of disk blocks. An ordered list of swap extents
1253 * is built at swapon time and is then used at swap_writepage/swap_readpage
1254 * time for locating where on disk a page belongs.
1256 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1257 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1258 * swap files identically.
1260 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1261 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1262 * swapfiles are handled *identically* after swapon time.
1264 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1265 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1266 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1267 * requirements, they are simply tossed out - we will never use those blocks
1270 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1271 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1272 * which will scribble on the fs.
1274 * The amount of disk space which a single swap extent represents varies.
1275 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1276 * extents in the list. To avoid much list walking, we cache the previous
1277 * search location in `curr_swap_extent', and start new searches from there.
1278 * This is extremely effective. The average number of iterations in
1279 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1281 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1283 struct inode
*inode
;
1284 unsigned blocks_per_page
;
1285 unsigned long page_no
;
1287 sector_t probe_block
;
1288 sector_t last_block
;
1289 sector_t lowest_block
= -1;
1290 sector_t highest_block
= 0;
1294 inode
= sis
->swap_file
->f_mapping
->host
;
1295 if (S_ISBLK(inode
->i_mode
)) {
1296 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1301 blkbits
= inode
->i_blkbits
;
1302 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1305 * Map all the blocks into the extent list. This code doesn't try
1310 last_block
= i_size_read(inode
) >> blkbits
;
1311 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1312 page_no
< sis
->max
) {
1313 unsigned block_in_page
;
1314 sector_t first_block
;
1316 first_block
= bmap(inode
, probe_block
);
1317 if (first_block
== 0)
1321 * It must be PAGE_SIZE aligned on-disk
1323 if (first_block
& (blocks_per_page
- 1)) {
1328 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1332 block
= bmap(inode
, probe_block
+ block_in_page
);
1335 if (block
!= first_block
+ block_in_page
) {
1342 first_block
>>= (PAGE_SHIFT
- blkbits
);
1343 if (page_no
) { /* exclude the header page */
1344 if (first_block
< lowest_block
)
1345 lowest_block
= first_block
;
1346 if (first_block
> highest_block
)
1347 highest_block
= first_block
;
1351 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1353 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1358 probe_block
+= blocks_per_page
;
1363 *span
= 1 + highest_block
- lowest_block
;
1365 page_no
= 1; /* force Empty message */
1367 sis
->pages
= page_no
- 1;
1368 sis
->highest_bit
= page_no
- 1;
1370 sis
->curr_swap_extent
= list_entry(sis
->extent_list
.prev
,
1371 struct swap_extent
, list
);
1374 printk(KERN_ERR
"swapon: swapfile has holes\n");
1380 asmlinkage
long sys_swapoff(const char __user
* specialfile
)
1382 struct swap_info_struct
* p
= NULL
;
1383 unsigned short *swap_map
;
1384 struct file
*swap_file
, *victim
;
1385 struct address_space
*mapping
;
1386 struct inode
*inode
;
1391 if (!capable(CAP_SYS_ADMIN
))
1394 pathname
= getname(specialfile
);
1395 err
= PTR_ERR(pathname
);
1396 if (IS_ERR(pathname
))
1399 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1401 err
= PTR_ERR(victim
);
1405 mapping
= victim
->f_mapping
;
1407 spin_lock(&swap_lock
);
1408 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
].next
) {
1409 p
= swap_info
+ type
;
1410 if (p
->flags
& SWP_WRITEOK
) {
1411 if (p
->swap_file
->f_mapping
== mapping
)
1418 spin_unlock(&swap_lock
);
1421 if (!security_vm_enough_memory(p
->pages
))
1422 vm_unacct_memory(p
->pages
);
1425 spin_unlock(&swap_lock
);
1429 swap_list
.head
= p
->next
;
1431 swap_info
[prev
].next
= p
->next
;
1433 if (type
== swap_list
.next
) {
1434 /* just pick something that's safe... */
1435 swap_list
.next
= swap_list
.head
;
1438 for (i
= p
->next
; i
>= 0; i
= swap_info
[i
].next
)
1439 swap_info
[i
].prio
= p
->prio
--;
1442 nr_swap_pages
-= p
->pages
;
1443 total_swap_pages
-= p
->pages
;
1444 p
->flags
&= ~SWP_WRITEOK
;
1445 spin_unlock(&swap_lock
);
1447 current
->flags
|= PF_SWAPOFF
;
1448 err
= try_to_unuse(type
);
1449 current
->flags
&= ~PF_SWAPOFF
;
1452 /* re-insert swap space back into swap_list */
1453 spin_lock(&swap_lock
);
1455 p
->prio
= --least_priority
;
1457 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1458 if (p
->prio
>= swap_info
[i
].prio
)
1464 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1466 swap_info
[prev
].next
= p
- swap_info
;
1467 nr_swap_pages
+= p
->pages
;
1468 total_swap_pages
+= p
->pages
;
1469 p
->flags
|= SWP_WRITEOK
;
1470 spin_unlock(&swap_lock
);
1474 /* wait for any unplug function to finish */
1475 down_write(&swap_unplug_sem
);
1476 up_write(&swap_unplug_sem
);
1478 destroy_swap_extents(p
);
1479 mutex_lock(&swapon_mutex
);
1480 spin_lock(&swap_lock
);
1483 /* wait for anyone still in scan_swap_map */
1484 p
->highest_bit
= 0; /* cuts scans short */
1485 while (p
->flags
>= SWP_SCANNING
) {
1486 spin_unlock(&swap_lock
);
1487 schedule_timeout_uninterruptible(1);
1488 spin_lock(&swap_lock
);
1491 swap_file
= p
->swap_file
;
1492 p
->swap_file
= NULL
;
1494 swap_map
= p
->swap_map
;
1497 spin_unlock(&swap_lock
);
1498 mutex_unlock(&swapon_mutex
);
1500 /* Destroy swap account informatin */
1501 swap_cgroup_swapoff(type
);
1503 inode
= mapping
->host
;
1504 if (S_ISBLK(inode
->i_mode
)) {
1505 struct block_device
*bdev
= I_BDEV(inode
);
1506 set_blocksize(bdev
, p
->old_block_size
);
1509 mutex_lock(&inode
->i_mutex
);
1510 inode
->i_flags
&= ~S_SWAPFILE
;
1511 mutex_unlock(&inode
->i_mutex
);
1513 filp_close(swap_file
, NULL
);
1517 filp_close(victim
, NULL
);
1522 #ifdef CONFIG_PROC_FS
1524 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1526 struct swap_info_struct
*ptr
= swap_info
;
1530 mutex_lock(&swapon_mutex
);
1533 return SEQ_START_TOKEN
;
1535 for (i
= 0; i
< nr_swapfiles
; i
++, ptr
++) {
1536 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1545 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1547 struct swap_info_struct
*ptr
;
1548 struct swap_info_struct
*endptr
= swap_info
+ nr_swapfiles
;
1550 if (v
== SEQ_START_TOKEN
)
1557 for (; ptr
< endptr
; ptr
++) {
1558 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1567 static void swap_stop(struct seq_file
*swap
, void *v
)
1569 mutex_unlock(&swapon_mutex
);
1572 static int swap_show(struct seq_file
*swap
, void *v
)
1574 struct swap_info_struct
*ptr
= v
;
1578 if (ptr
== SEQ_START_TOKEN
) {
1579 seq_puts(swap
,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1583 file
= ptr
->swap_file
;
1584 len
= seq_path(swap
, &file
->f_path
, " \t\n\\");
1585 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1586 len
< 40 ? 40 - len
: 1, " ",
1587 S_ISBLK(file
->f_path
.dentry
->d_inode
->i_mode
) ?
1588 "partition" : "file\t",
1589 ptr
->pages
<< (PAGE_SHIFT
- 10),
1590 ptr
->inuse_pages
<< (PAGE_SHIFT
- 10),
1595 static const struct seq_operations swaps_op
= {
1596 .start
= swap_start
,
1602 static int swaps_open(struct inode
*inode
, struct file
*file
)
1604 return seq_open(file
, &swaps_op
);
1607 static const struct file_operations proc_swaps_operations
= {
1610 .llseek
= seq_lseek
,
1611 .release
= seq_release
,
1614 static int __init
procswaps_init(void)
1616 proc_create("swaps", 0, NULL
, &proc_swaps_operations
);
1619 __initcall(procswaps_init
);
1620 #endif /* CONFIG_PROC_FS */
1622 #ifdef MAX_SWAPFILES_CHECK
1623 static int __init
max_swapfiles_check(void)
1625 MAX_SWAPFILES_CHECK();
1628 late_initcall(max_swapfiles_check
);
1632 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1634 * The swapon system call
1636 asmlinkage
long sys_swapon(const char __user
* specialfile
, int swap_flags
)
1638 struct swap_info_struct
* p
;
1640 struct block_device
*bdev
= NULL
;
1641 struct file
*swap_file
= NULL
;
1642 struct address_space
*mapping
;
1646 union swap_header
*swap_header
= NULL
;
1647 unsigned int nr_good_pages
= 0;
1650 unsigned long maxpages
= 1;
1651 unsigned long swapfilepages
;
1652 unsigned short *swap_map
= NULL
;
1653 struct page
*page
= NULL
;
1654 struct inode
*inode
= NULL
;
1657 if (!capable(CAP_SYS_ADMIN
))
1659 spin_lock(&swap_lock
);
1661 for (type
= 0 ; type
< nr_swapfiles
; type
++,p
++)
1662 if (!(p
->flags
& SWP_USED
))
1665 if (type
>= MAX_SWAPFILES
) {
1666 spin_unlock(&swap_lock
);
1669 if (type
>= nr_swapfiles
)
1670 nr_swapfiles
= type
+1;
1671 memset(p
, 0, sizeof(*p
));
1672 INIT_LIST_HEAD(&p
->extent_list
);
1673 p
->flags
= SWP_USED
;
1675 spin_unlock(&swap_lock
);
1676 name
= getname(specialfile
);
1677 error
= PTR_ERR(name
);
1682 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1683 error
= PTR_ERR(swap_file
);
1684 if (IS_ERR(swap_file
)) {
1689 p
->swap_file
= swap_file
;
1690 mapping
= swap_file
->f_mapping
;
1691 inode
= mapping
->host
;
1694 for (i
= 0; i
< nr_swapfiles
; i
++) {
1695 struct swap_info_struct
*q
= &swap_info
[i
];
1697 if (i
== type
|| !q
->swap_file
)
1699 if (mapping
== q
->swap_file
->f_mapping
)
1704 if (S_ISBLK(inode
->i_mode
)) {
1705 bdev
= I_BDEV(inode
);
1706 error
= bd_claim(bdev
, sys_swapon
);
1712 p
->old_block_size
= block_size(bdev
);
1713 error
= set_blocksize(bdev
, PAGE_SIZE
);
1717 } else if (S_ISREG(inode
->i_mode
)) {
1718 p
->bdev
= inode
->i_sb
->s_bdev
;
1719 mutex_lock(&inode
->i_mutex
);
1721 if (IS_SWAPFILE(inode
)) {
1729 swapfilepages
= i_size_read(inode
) >> PAGE_SHIFT
;
1732 * Read the swap header.
1734 if (!mapping
->a_ops
->readpage
) {
1738 page
= read_mapping_page(mapping
, 0, swap_file
);
1740 error
= PTR_ERR(page
);
1743 swap_header
= kmap(page
);
1745 if (memcmp("SWAPSPACE2", swap_header
->magic
.magic
, 10)) {
1746 printk(KERN_ERR
"Unable to find swap-space signature\n");
1751 /* swap partition endianess hack... */
1752 if (swab32(swap_header
->info
.version
) == 1) {
1753 swab32s(&swap_header
->info
.version
);
1754 swab32s(&swap_header
->info
.last_page
);
1755 swab32s(&swap_header
->info
.nr_badpages
);
1756 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++)
1757 swab32s(&swap_header
->info
.badpages
[i
]);
1759 /* Check the swap header's sub-version */
1760 if (swap_header
->info
.version
!= 1) {
1762 "Unable to handle swap header version %d\n",
1763 swap_header
->info
.version
);
1769 p
->cluster_next
= 1;
1772 * Find out how many pages are allowed for a single swap
1773 * device. There are two limiting factors: 1) the number of
1774 * bits for the swap offset in the swp_entry_t type and
1775 * 2) the number of bits in the a swap pte as defined by
1776 * the different architectures. In order to find the
1777 * largest possible bit mask a swap entry with swap type 0
1778 * and swap offset ~0UL is created, encoded to a swap pte,
1779 * decoded to a swp_entry_t again and finally the swap
1780 * offset is extracted. This will mask all the bits from
1781 * the initial ~0UL mask that can't be encoded in either
1782 * the swp_entry_t or the architecture definition of a
1785 maxpages
= swp_offset(pte_to_swp_entry(
1786 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1787 if (maxpages
> swap_header
->info
.last_page
)
1788 maxpages
= swap_header
->info
.last_page
;
1789 p
->highest_bit
= maxpages
- 1;
1794 if (swapfilepages
&& maxpages
> swapfilepages
) {
1796 "Swap area shorter than signature indicates\n");
1799 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1801 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1804 /* OK, set up the swap map and apply the bad block list */
1805 swap_map
= vmalloc(maxpages
* sizeof(short));
1811 memset(swap_map
, 0, maxpages
* sizeof(short));
1812 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
1813 int page_nr
= swap_header
->info
.badpages
[i
];
1814 if (page_nr
<= 0 || page_nr
>= swap_header
->info
.last_page
) {
1818 swap_map
[page_nr
] = SWAP_MAP_BAD
;
1821 error
= swap_cgroup_swapon(type
, maxpages
);
1825 nr_good_pages
= swap_header
->info
.last_page
-
1826 swap_header
->info
.nr_badpages
-
1827 1 /* header page */;
1829 if (nr_good_pages
) {
1830 swap_map
[0] = SWAP_MAP_BAD
;
1832 p
->pages
= nr_good_pages
;
1833 nr_extents
= setup_swap_extents(p
, &span
);
1834 if (nr_extents
< 0) {
1838 nr_good_pages
= p
->pages
;
1840 if (!nr_good_pages
) {
1841 printk(KERN_WARNING
"Empty swap-file\n");
1846 if (blk_queue_nonrot(bdev_get_queue(p
->bdev
))) {
1847 p
->flags
|= SWP_SOLIDSTATE
;
1848 p
->cluster_next
= 1 + (random32() % p
->highest_bit
);
1850 if (discard_swap(p
) == 0)
1851 p
->flags
|= SWP_DISCARDABLE
;
1853 mutex_lock(&swapon_mutex
);
1854 spin_lock(&swap_lock
);
1855 if (swap_flags
& SWAP_FLAG_PREFER
)
1857 (swap_flags
& SWAP_FLAG_PRIO_MASK
) >> SWAP_FLAG_PRIO_SHIFT
;
1859 p
->prio
= --least_priority
;
1860 p
->swap_map
= swap_map
;
1861 p
->flags
|= SWP_WRITEOK
;
1862 nr_swap_pages
+= nr_good_pages
;
1863 total_swap_pages
+= nr_good_pages
;
1865 printk(KERN_INFO
"Adding %uk swap on %s. "
1866 "Priority:%d extents:%d across:%lluk %s%s\n",
1867 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
1868 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10),
1869 (p
->flags
& SWP_SOLIDSTATE
) ? "SS" : "",
1870 (p
->flags
& SWP_DISCARDABLE
) ? "D" : "");
1872 /* insert swap space into swap_list: */
1874 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1875 if (p
->prio
>= swap_info
[i
].prio
) {
1882 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1884 swap_info
[prev
].next
= p
- swap_info
;
1886 spin_unlock(&swap_lock
);
1887 mutex_unlock(&swapon_mutex
);
1892 set_blocksize(bdev
, p
->old_block_size
);
1895 destroy_swap_extents(p
);
1896 swap_cgroup_swapoff(type
);
1898 spin_lock(&swap_lock
);
1899 p
->swap_file
= NULL
;
1901 spin_unlock(&swap_lock
);
1904 filp_close(swap_file
, NULL
);
1906 if (page
&& !IS_ERR(page
)) {
1908 page_cache_release(page
);
1914 inode
->i_flags
|= S_SWAPFILE
;
1915 mutex_unlock(&inode
->i_mutex
);
1920 void si_swapinfo(struct sysinfo
*val
)
1923 unsigned long nr_to_be_unused
= 0;
1925 spin_lock(&swap_lock
);
1926 for (i
= 0; i
< nr_swapfiles
; i
++) {
1927 if (!(swap_info
[i
].flags
& SWP_USED
) ||
1928 (swap_info
[i
].flags
& SWP_WRITEOK
))
1930 nr_to_be_unused
+= swap_info
[i
].inuse_pages
;
1932 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
1933 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
1934 spin_unlock(&swap_lock
);
1938 * Verify that a swap entry is valid and increment its swap map count.
1940 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1941 * "permanent", but will be reclaimed by the next swapoff.
1943 int swap_duplicate(swp_entry_t entry
)
1945 struct swap_info_struct
* p
;
1946 unsigned long offset
, type
;
1949 if (is_migration_entry(entry
))
1952 type
= swp_type(entry
);
1953 if (type
>= nr_swapfiles
)
1955 p
= type
+ swap_info
;
1956 offset
= swp_offset(entry
);
1958 spin_lock(&swap_lock
);
1959 if (offset
< p
->max
&& p
->swap_map
[offset
]) {
1960 if (p
->swap_map
[offset
] < SWAP_MAP_MAX
- 1) {
1961 p
->swap_map
[offset
]++;
1963 } else if (p
->swap_map
[offset
] <= SWAP_MAP_MAX
) {
1964 if (swap_overflow
++ < 5)
1965 printk(KERN_WARNING
"swap_dup: swap entry overflow\n");
1966 p
->swap_map
[offset
] = SWAP_MAP_MAX
;
1970 spin_unlock(&swap_lock
);
1975 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
1979 struct swap_info_struct
*
1980 get_swap_info_struct(unsigned type
)
1982 return &swap_info
[type
];
1986 * swap_lock prevents swap_map being freed. Don't grab an extra
1987 * reference on the swaphandle, it doesn't matter if it becomes unused.
1989 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
1991 struct swap_info_struct
*si
;
1992 int our_page_cluster
= page_cluster
;
1993 pgoff_t target
, toff
;
1997 if (!our_page_cluster
) /* no readahead */
2000 si
= &swap_info
[swp_type(entry
)];
2001 target
= swp_offset(entry
);
2002 base
= (target
>> our_page_cluster
) << our_page_cluster
;
2003 end
= base
+ (1 << our_page_cluster
);
2004 if (!base
) /* first page is swap header */
2007 spin_lock(&swap_lock
);
2008 if (end
> si
->max
) /* don't go beyond end of map */
2011 /* Count contiguous allocated slots above our target */
2012 for (toff
= target
; ++toff
< end
; nr_pages
++) {
2013 /* Don't read in free or bad pages */
2014 if (!si
->swap_map
[toff
])
2016 if (si
->swap_map
[toff
] == SWAP_MAP_BAD
)
2019 /* Count contiguous allocated slots below our target */
2020 for (toff
= target
; --toff
>= base
; nr_pages
++) {
2021 /* Don't read in free or bad pages */
2022 if (!si
->swap_map
[toff
])
2024 if (si
->swap_map
[toff
] == SWAP_MAP_BAD
)
2027 spin_unlock(&swap_lock
);
2030 * Indicate starting offset, and return number of pages to get:
2031 * if only 1, say 0, since there's then no readahead to be done.
2034 return nr_pages
? ++nr_pages
: 0;