4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
8 #include <linux/config.h>
10 #include <linux/hugetlb.h>
11 #include <linux/mman.h>
12 #include <linux/slab.h>
13 #include <linux/kernel_stat.h>
14 #include <linux/swap.h>
15 #include <linux/vmalloc.h>
16 #include <linux/pagemap.h>
17 #include <linux/namei.h>
18 #include <linux/shm.h>
19 #include <linux/blkdev.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>
32 #include <asm/pgtable.h>
33 #include <asm/tlbflush.h>
34 #include <linux/swapops.h>
36 DEFINE_SPINLOCK(swap_lock
);
37 unsigned int nr_swapfiles
;
38 long total_swap_pages
;
39 static int swap_overflow
;
41 static const char Bad_file
[] = "Bad swap file entry ";
42 static const char Unused_file
[] = "Unused swap file entry ";
43 static const char Bad_offset
[] = "Bad swap offset entry ";
44 static const char Unused_offset
[] = "Unused swap offset entry ";
46 struct swap_list_t swap_list
= {-1, -1};
48 static struct swap_info_struct swap_info
[MAX_SWAPFILES
];
50 static DEFINE_MUTEX(swapon_mutex
);
53 * We need this because the bdev->unplug_fn can sleep and we cannot
54 * hold swap_lock while calling the unplug_fn. And swap_lock
55 * cannot be turned into a mutex.
57 static DECLARE_RWSEM(swap_unplug_sem
);
59 void swap_unplug_io_fn(struct backing_dev_info
*unused_bdi
, struct page
*page
)
63 down_read(&swap_unplug_sem
);
64 entry
.val
= page_private(page
);
65 if (PageSwapCache(page
)) {
66 struct block_device
*bdev
= swap_info
[swp_type(entry
)].bdev
;
67 struct backing_dev_info
*bdi
;
70 * If the page is removed from swapcache from under us (with a
71 * racy try_to_unuse/swapoff) we need an additional reference
72 * count to avoid reading garbage from page_private(page) above.
73 * If the WARN_ON triggers during a swapoff it maybe the race
74 * condition and it's harmless. However if it triggers without
75 * swapoff it signals a problem.
77 WARN_ON(page_count(page
) <= 1);
79 bdi
= bdev
->bd_inode
->i_mapping
->backing_dev_info
;
80 blk_run_backing_dev(bdi
, page
);
82 up_read(&swap_unplug_sem
);
85 #define SWAPFILE_CLUSTER 256
86 #define LATENCY_LIMIT 256
88 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
)
90 unsigned long offset
, last_in_cluster
;
91 int latency_ration
= LATENCY_LIMIT
;
94 * We try to cluster swap pages by allocating them sequentially
95 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
96 * way, however, we resort to first-free allocation, starting
97 * a new cluster. This prevents us from scattering swap pages
98 * all over the entire swap partition, so that we reduce
99 * overall disk seek times between swap pages. -- sct
100 * But we do now try to find an empty cluster. -Andrea
103 si
->flags
+= SWP_SCANNING
;
104 if (unlikely(!si
->cluster_nr
)) {
105 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
106 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
)
108 spin_unlock(&swap_lock
);
110 offset
= si
->lowest_bit
;
111 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
113 /* Locate the first empty (unaligned) cluster */
114 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
115 if (si
->swap_map
[offset
])
116 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
117 else if (offset
== last_in_cluster
) {
118 spin_lock(&swap_lock
);
119 si
->cluster_next
= offset
-SWAPFILE_CLUSTER
+1;
122 if (unlikely(--latency_ration
< 0)) {
124 latency_ration
= LATENCY_LIMIT
;
127 spin_lock(&swap_lock
);
133 offset
= si
->cluster_next
;
134 if (offset
> si
->highest_bit
)
135 lowest
: offset
= si
->lowest_bit
;
136 checks
: if (!(si
->flags
& SWP_WRITEOK
))
138 if (!si
->highest_bit
)
140 if (!si
->swap_map
[offset
]) {
141 if (offset
== si
->lowest_bit
)
143 if (offset
== si
->highest_bit
)
146 if (si
->inuse_pages
== si
->pages
) {
147 si
->lowest_bit
= si
->max
;
150 si
->swap_map
[offset
] = 1;
151 si
->cluster_next
= offset
+ 1;
152 si
->flags
-= SWP_SCANNING
;
156 spin_unlock(&swap_lock
);
157 while (++offset
<= si
->highest_bit
) {
158 if (!si
->swap_map
[offset
]) {
159 spin_lock(&swap_lock
);
162 if (unlikely(--latency_ration
< 0)) {
164 latency_ration
= LATENCY_LIMIT
;
167 spin_lock(&swap_lock
);
171 si
->flags
-= SWP_SCANNING
;
175 swp_entry_t
get_swap_page(void)
177 struct swap_info_struct
*si
;
182 spin_lock(&swap_lock
);
183 if (nr_swap_pages
<= 0)
187 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
188 si
= swap_info
+ type
;
191 (!wrapped
&& si
->prio
!= swap_info
[next
].prio
)) {
192 next
= swap_list
.head
;
196 if (!si
->highest_bit
)
198 if (!(si
->flags
& SWP_WRITEOK
))
201 swap_list
.next
= next
;
202 offset
= scan_swap_map(si
);
204 spin_unlock(&swap_lock
);
205 return swp_entry(type
, offset
);
207 next
= swap_list
.next
;
212 spin_unlock(&swap_lock
);
213 return (swp_entry_t
) {0};
216 swp_entry_t
get_swap_page_of_type(int type
)
218 struct swap_info_struct
*si
;
221 spin_lock(&swap_lock
);
222 si
= swap_info
+ type
;
223 if (si
->flags
& SWP_WRITEOK
) {
225 offset
= scan_swap_map(si
);
227 spin_unlock(&swap_lock
);
228 return swp_entry(type
, offset
);
232 spin_unlock(&swap_lock
);
233 return (swp_entry_t
) {0};
236 static struct swap_info_struct
* swap_info_get(swp_entry_t entry
)
238 struct swap_info_struct
* p
;
239 unsigned long offset
, type
;
243 type
= swp_type(entry
);
244 if (type
>= nr_swapfiles
)
246 p
= & swap_info
[type
];
247 if (!(p
->flags
& SWP_USED
))
249 offset
= swp_offset(entry
);
250 if (offset
>= p
->max
)
252 if (!p
->swap_map
[offset
])
254 spin_lock(&swap_lock
);
258 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
261 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
264 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
267 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
272 static int swap_entry_free(struct swap_info_struct
*p
, unsigned long offset
)
274 int count
= p
->swap_map
[offset
];
276 if (count
< SWAP_MAP_MAX
) {
278 p
->swap_map
[offset
] = count
;
280 if (offset
< p
->lowest_bit
)
281 p
->lowest_bit
= offset
;
282 if (offset
> p
->highest_bit
)
283 p
->highest_bit
= offset
;
284 if (p
->prio
> swap_info
[swap_list
.next
].prio
)
285 swap_list
.next
= p
- swap_info
;
294 * Caller has made sure that the swapdevice corresponding to entry
295 * is still around or has not been recycled.
297 void swap_free(swp_entry_t entry
)
299 struct swap_info_struct
* p
;
301 p
= swap_info_get(entry
);
303 swap_entry_free(p
, swp_offset(entry
));
304 spin_unlock(&swap_lock
);
309 * How many references to page are currently swapped out?
311 static inline int page_swapcount(struct page
*page
)
314 struct swap_info_struct
*p
;
317 entry
.val
= page_private(page
);
318 p
= swap_info_get(entry
);
320 /* Subtract the 1 for the swap cache itself */
321 count
= p
->swap_map
[swp_offset(entry
)] - 1;
322 spin_unlock(&swap_lock
);
328 * We can use this swap cache entry directly
329 * if there are no other references to it.
331 int can_share_swap_page(struct page
*page
)
335 BUG_ON(!PageLocked(page
));
336 count
= page_mapcount(page
);
337 if (count
<= 1 && PageSwapCache(page
))
338 count
+= page_swapcount(page
);
343 * Work out if there are any other processes sharing this
344 * swap cache page. Free it if you can. Return success.
346 int remove_exclusive_swap_page(struct page
*page
)
349 struct swap_info_struct
* p
;
352 BUG_ON(PagePrivate(page
));
353 BUG_ON(!PageLocked(page
));
355 if (!PageSwapCache(page
))
357 if (PageWriteback(page
))
359 if (page_count(page
) != 2) /* 2: us + cache */
362 entry
.val
= page_private(page
);
363 p
= swap_info_get(entry
);
367 /* Is the only swap cache user the cache itself? */
369 if (p
->swap_map
[swp_offset(entry
)] == 1) {
370 /* Recheck the page count with the swapcache lock held.. */
371 write_lock_irq(&swapper_space
.tree_lock
);
372 if ((page_count(page
) == 2) && !PageWriteback(page
)) {
373 __delete_from_swap_cache(page
);
377 write_unlock_irq(&swapper_space
.tree_lock
);
379 spin_unlock(&swap_lock
);
383 page_cache_release(page
);
390 * Free the swap entry like above, but also try to
391 * free the page cache entry if it is the last user.
393 void free_swap_and_cache(swp_entry_t entry
)
395 struct swap_info_struct
* p
;
396 struct page
*page
= NULL
;
398 if (is_migration_entry(entry
))
401 p
= swap_info_get(entry
);
403 if (swap_entry_free(p
, swp_offset(entry
)) == 1) {
404 page
= find_get_page(&swapper_space
, entry
.val
);
405 if (page
&& unlikely(TestSetPageLocked(page
))) {
406 page_cache_release(page
);
410 spin_unlock(&swap_lock
);
415 BUG_ON(PagePrivate(page
));
416 one_user
= (page_count(page
) == 2);
417 /* Only cache user (+us), or swap space full? Free it! */
418 /* Also recheck PageSwapCache after page is locked (above) */
419 if (PageSwapCache(page
) && !PageWriteback(page
) &&
420 (one_user
|| vm_swap_full())) {
421 delete_from_swap_cache(page
);
425 page_cache_release(page
);
429 #ifdef CONFIG_SOFTWARE_SUSPEND
431 * Find the swap type that corresponds to given device (if any)
433 * This is needed for software suspend and is done in such a way that inode
434 * aliasing is allowed.
436 int swap_type_of(dev_t device
)
440 spin_lock(&swap_lock
);
441 for (i
= 0; i
< nr_swapfiles
; i
++) {
444 if (!(swap_info
[i
].flags
& SWP_WRITEOK
))
447 spin_unlock(&swap_lock
);
450 inode
= swap_info
->swap_file
->f_dentry
->d_inode
;
451 if (S_ISBLK(inode
->i_mode
) &&
452 device
== MKDEV(imajor(inode
), iminor(inode
))) {
453 spin_unlock(&swap_lock
);
457 spin_unlock(&swap_lock
);
462 * Return either the total number of swap pages of given type, or the number
463 * of free pages of that type (depending on @free)
465 * This is needed for software suspend
467 unsigned int count_swap_pages(int type
, int free
)
471 if (type
< nr_swapfiles
) {
472 spin_lock(&swap_lock
);
473 if (swap_info
[type
].flags
& SWP_WRITEOK
) {
474 n
= swap_info
[type
].pages
;
476 n
-= swap_info
[type
].inuse_pages
;
478 spin_unlock(&swap_lock
);
485 * No need to decide whether this PTE shares the swap entry with others,
486 * just let do_wp_page work it out if a write is requested later - to
487 * force COW, vm_page_prot omits write permission from any private vma.
489 static void unuse_pte(struct vm_area_struct
*vma
, pte_t
*pte
,
490 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
492 inc_mm_counter(vma
->vm_mm
, anon_rss
);
494 set_pte_at(vma
->vm_mm
, addr
, pte
,
495 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
496 page_add_anon_rmap(page
, vma
, addr
);
499 * Move the page to the active list so it is not
500 * immediately swapped out again after swapon.
505 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
506 unsigned long addr
, unsigned long end
,
507 swp_entry_t entry
, struct page
*page
)
509 pte_t swp_pte
= swp_entry_to_pte(entry
);
514 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
517 * swapoff spends a _lot_ of time in this loop!
518 * Test inline before going to call unuse_pte.
520 if (unlikely(pte_same(*pte
, swp_pte
))) {
521 unuse_pte(vma
, pte
++, addr
, entry
, page
);
525 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
526 pte_unmap_unlock(pte
- 1, ptl
);
530 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
531 unsigned long addr
, unsigned long end
,
532 swp_entry_t entry
, struct page
*page
)
537 pmd
= pmd_offset(pud
, addr
);
539 next
= pmd_addr_end(addr
, end
);
540 if (pmd_none_or_clear_bad(pmd
))
542 if (unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
))
544 } while (pmd
++, addr
= next
, addr
!= end
);
548 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
549 unsigned long addr
, unsigned long end
,
550 swp_entry_t entry
, struct page
*page
)
555 pud
= pud_offset(pgd
, addr
);
557 next
= pud_addr_end(addr
, end
);
558 if (pud_none_or_clear_bad(pud
))
560 if (unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
))
562 } while (pud
++, addr
= next
, addr
!= end
);
566 static int unuse_vma(struct vm_area_struct
*vma
,
567 swp_entry_t entry
, struct page
*page
)
570 unsigned long addr
, end
, next
;
573 addr
= page_address_in_vma(page
, vma
);
577 end
= addr
+ PAGE_SIZE
;
579 addr
= vma
->vm_start
;
583 pgd
= pgd_offset(vma
->vm_mm
, addr
);
585 next
= pgd_addr_end(addr
, end
);
586 if (pgd_none_or_clear_bad(pgd
))
588 if (unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
))
590 } while (pgd
++, addr
= next
, addr
!= end
);
594 static int unuse_mm(struct mm_struct
*mm
,
595 swp_entry_t entry
, struct page
*page
)
597 struct vm_area_struct
*vma
;
599 if (!down_read_trylock(&mm
->mmap_sem
)) {
601 * Activate page so shrink_cache is unlikely to unmap its
602 * ptes while lock is dropped, so swapoff can make progress.
606 down_read(&mm
->mmap_sem
);
609 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
610 if (vma
->anon_vma
&& unuse_vma(vma
, entry
, page
))
613 up_read(&mm
->mmap_sem
);
615 * Currently unuse_mm cannot fail, but leave error handling
616 * at call sites for now, since we change it from time to time.
621 #ifdef CONFIG_MIGRATION
622 int remove_vma_swap(struct vm_area_struct
*vma
, struct page
*page
)
624 swp_entry_t entry
= { .val
= page_private(page
) };
626 return unuse_vma(vma
, entry
, page
);
631 * Scan swap_map from current position to next entry still in use.
632 * Recycle to start on reaching the end, returning 0 when empty.
634 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
637 unsigned int max
= si
->max
;
638 unsigned int i
= prev
;
642 * No need for swap_lock here: we're just looking
643 * for whether an entry is in use, not modifying it; false
644 * hits are okay, and sys_swapoff() has already prevented new
645 * allocations from this area (while holding swap_lock).
654 * No entries in use at top of swap_map,
655 * loop back to start and recheck there.
661 count
= si
->swap_map
[i
];
662 if (count
&& count
!= SWAP_MAP_BAD
)
669 * We completely avoid races by reading each swap page in advance,
670 * and then search for the process using it. All the necessary
671 * page table adjustments can then be made atomically.
673 static int try_to_unuse(unsigned int type
)
675 struct swap_info_struct
* si
= &swap_info
[type
];
676 struct mm_struct
*start_mm
;
677 unsigned short *swap_map
;
678 unsigned short swcount
;
683 int reset_overflow
= 0;
687 * When searching mms for an entry, a good strategy is to
688 * start at the first mm we freed the previous entry from
689 * (though actually we don't notice whether we or coincidence
690 * freed the entry). Initialize this start_mm with a hold.
692 * A simpler strategy would be to start at the last mm we
693 * freed the previous entry from; but that would take less
694 * advantage of mmlist ordering, which clusters forked mms
695 * together, child after parent. If we race with dup_mmap(), we
696 * prefer to resolve parent before child, lest we miss entries
697 * duplicated after we scanned child: using last mm would invert
698 * that. Though it's only a serious concern when an overflowed
699 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
702 atomic_inc(&init_mm
.mm_users
);
705 * Keep on scanning until all entries have gone. Usually,
706 * one pass through swap_map is enough, but not necessarily:
707 * there are races when an instance of an entry might be missed.
709 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
710 if (signal_pending(current
)) {
716 * Get a page for the entry, using the existing swap
717 * cache page if there is one. Otherwise, get a clean
718 * page and read the swap into it.
720 swap_map
= &si
->swap_map
[i
];
721 entry
= swp_entry(type
, i
);
722 page
= read_swap_cache_async(entry
, NULL
, 0);
725 * Either swap_duplicate() failed because entry
726 * has been freed independently, and will not be
727 * reused since sys_swapoff() already disabled
728 * allocation from here, or alloc_page() failed.
737 * Don't hold on to start_mm if it looks like exiting.
739 if (atomic_read(&start_mm
->mm_users
) == 1) {
742 atomic_inc(&init_mm
.mm_users
);
746 * Wait for and lock page. When do_swap_page races with
747 * try_to_unuse, do_swap_page can handle the fault much
748 * faster than try_to_unuse can locate the entry. This
749 * apparently redundant "wait_on_page_locked" lets try_to_unuse
750 * defer to do_swap_page in such a case - in some tests,
751 * do_swap_page and try_to_unuse repeatedly compete.
753 wait_on_page_locked(page
);
754 wait_on_page_writeback(page
);
756 wait_on_page_writeback(page
);
759 * Remove all references to entry.
760 * Whenever we reach init_mm, there's no address space
761 * to search, but use it as a reminder to search shmem.
766 if (start_mm
== &init_mm
)
767 shmem
= shmem_unuse(entry
, page
);
769 retval
= unuse_mm(start_mm
, entry
, page
);
772 int set_start_mm
= (*swap_map
>= swcount
);
773 struct list_head
*p
= &start_mm
->mmlist
;
774 struct mm_struct
*new_start_mm
= start_mm
;
775 struct mm_struct
*prev_mm
= start_mm
;
776 struct mm_struct
*mm
;
778 atomic_inc(&new_start_mm
->mm_users
);
779 atomic_inc(&prev_mm
->mm_users
);
780 spin_lock(&mmlist_lock
);
781 while (*swap_map
> 1 && !retval
&&
782 (p
= p
->next
) != &start_mm
->mmlist
) {
783 mm
= list_entry(p
, struct mm_struct
, mmlist
);
784 if (atomic_inc_return(&mm
->mm_users
) == 1) {
785 atomic_dec(&mm
->mm_users
);
788 spin_unlock(&mmlist_lock
);
797 else if (mm
== &init_mm
) {
799 shmem
= shmem_unuse(entry
, page
);
801 retval
= unuse_mm(mm
, entry
, page
);
802 if (set_start_mm
&& *swap_map
< swcount
) {
804 atomic_inc(&mm
->mm_users
);
808 spin_lock(&mmlist_lock
);
810 spin_unlock(&mmlist_lock
);
813 start_mm
= new_start_mm
;
817 page_cache_release(page
);
822 * How could swap count reach 0x7fff when the maximum
823 * pid is 0x7fff, and there's no way to repeat a swap
824 * page within an mm (except in shmem, where it's the
825 * shared object which takes the reference count)?
826 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
828 * If that's wrong, then we should worry more about
829 * exit_mmap() and do_munmap() cases described above:
830 * we might be resetting SWAP_MAP_MAX too early here.
831 * We know "Undead"s can happen, they're okay, so don't
832 * report them; but do report if we reset SWAP_MAP_MAX.
834 if (*swap_map
== SWAP_MAP_MAX
) {
835 spin_lock(&swap_lock
);
837 spin_unlock(&swap_lock
);
842 * If a reference remains (rare), we would like to leave
843 * the page in the swap cache; but try_to_unmap could
844 * then re-duplicate the entry once we drop page lock,
845 * so we might loop indefinitely; also, that page could
846 * not be swapped out to other storage meanwhile. So:
847 * delete from cache even if there's another reference,
848 * after ensuring that the data has been saved to disk -
849 * since if the reference remains (rarer), it will be
850 * read from disk into another page. Splitting into two
851 * pages would be incorrect if swap supported "shared
852 * private" pages, but they are handled by tmpfs files.
854 * Note shmem_unuse already deleted a swappage from
855 * the swap cache, unless the move to filepage failed:
856 * in which case it left swappage in cache, lowered its
857 * swap count to pass quickly through the loops above,
858 * and now we must reincrement count to try again later.
860 if ((*swap_map
> 1) && PageDirty(page
) && PageSwapCache(page
)) {
861 struct writeback_control wbc
= {
862 .sync_mode
= WB_SYNC_NONE
,
865 swap_writepage(page
, &wbc
);
867 wait_on_page_writeback(page
);
869 if (PageSwapCache(page
)) {
871 swap_duplicate(entry
);
873 delete_from_swap_cache(page
);
877 * So we could skip searching mms once swap count went
878 * to 1, we did not mark any present ptes as dirty: must
879 * mark page dirty so shrink_list will preserve it.
883 page_cache_release(page
);
886 * Make sure that we aren't completely killing
887 * interactive performance.
893 if (reset_overflow
) {
894 printk(KERN_WARNING
"swapoff: cleared swap entry overflow\n");
901 * After a successful try_to_unuse, if no swap is now in use, we know
902 * we can empty the mmlist. swap_lock must be held on entry and exit.
903 * Note that mmlist_lock nests inside swap_lock, and an mm must be
904 * added to the mmlist just after page_duplicate - before would be racy.
906 static void drain_mmlist(void)
908 struct list_head
*p
, *next
;
911 for (i
= 0; i
< nr_swapfiles
; i
++)
912 if (swap_info
[i
].inuse_pages
)
914 spin_lock(&mmlist_lock
);
915 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
917 spin_unlock(&mmlist_lock
);
921 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
922 * corresponds to page offset `offset'.
924 sector_t
map_swap_page(struct swap_info_struct
*sis
, pgoff_t offset
)
926 struct swap_extent
*se
= sis
->curr_swap_extent
;
927 struct swap_extent
*start_se
= se
;
930 struct list_head
*lh
;
932 if (se
->start_page
<= offset
&&
933 offset
< (se
->start_page
+ se
->nr_pages
)) {
934 return se
->start_block
+ (offset
- se
->start_page
);
937 if (lh
== &sis
->extent_list
)
939 se
= list_entry(lh
, struct swap_extent
, list
);
940 sis
->curr_swap_extent
= se
;
941 BUG_ON(se
== start_se
); /* It *must* be present */
946 * Free all of a swapdev's extent information
948 static void destroy_swap_extents(struct swap_info_struct
*sis
)
950 while (!list_empty(&sis
->extent_list
)) {
951 struct swap_extent
*se
;
953 se
= list_entry(sis
->extent_list
.next
,
954 struct swap_extent
, list
);
961 * Add a block range (and the corresponding page range) into this swapdev's
962 * extent list. The extent list is kept sorted in page order.
964 * This function rather assumes that it is called in ascending page order.
967 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
968 unsigned long nr_pages
, sector_t start_block
)
970 struct swap_extent
*se
;
971 struct swap_extent
*new_se
;
972 struct list_head
*lh
;
974 lh
= sis
->extent_list
.prev
; /* The highest page extent */
975 if (lh
!= &sis
->extent_list
) {
976 se
= list_entry(lh
, struct swap_extent
, list
);
977 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
978 if (se
->start_block
+ se
->nr_pages
== start_block
) {
980 se
->nr_pages
+= nr_pages
;
986 * No merge. Insert a new extent, preserving ordering.
988 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
991 new_se
->start_page
= start_page
;
992 new_se
->nr_pages
= nr_pages
;
993 new_se
->start_block
= start_block
;
995 list_add_tail(&new_se
->list
, &sis
->extent_list
);
1000 * A `swap extent' is a simple thing which maps a contiguous range of pages
1001 * onto a contiguous range of disk blocks. An ordered list of swap extents
1002 * is built at swapon time and is then used at swap_writepage/swap_readpage
1003 * time for locating where on disk a page belongs.
1005 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1006 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1007 * swap files identically.
1009 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1010 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1011 * swapfiles are handled *identically* after swapon time.
1013 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1014 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1015 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1016 * requirements, they are simply tossed out - we will never use those blocks
1019 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1020 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1021 * which will scribble on the fs.
1023 * The amount of disk space which a single swap extent represents varies.
1024 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1025 * extents in the list. To avoid much list walking, we cache the previous
1026 * search location in `curr_swap_extent', and start new searches from there.
1027 * This is extremely effective. The average number of iterations in
1028 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1030 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1032 struct inode
*inode
;
1033 unsigned blocks_per_page
;
1034 unsigned long page_no
;
1036 sector_t probe_block
;
1037 sector_t last_block
;
1038 sector_t lowest_block
= -1;
1039 sector_t highest_block
= 0;
1043 inode
= sis
->swap_file
->f_mapping
->host
;
1044 if (S_ISBLK(inode
->i_mode
)) {
1045 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1050 blkbits
= inode
->i_blkbits
;
1051 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1054 * Map all the blocks into the extent list. This code doesn't try
1059 last_block
= i_size_read(inode
) >> blkbits
;
1060 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1061 page_no
< sis
->max
) {
1062 unsigned block_in_page
;
1063 sector_t first_block
;
1065 first_block
= bmap(inode
, probe_block
);
1066 if (first_block
== 0)
1070 * It must be PAGE_SIZE aligned on-disk
1072 if (first_block
& (blocks_per_page
- 1)) {
1077 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1081 block
= bmap(inode
, probe_block
+ block_in_page
);
1084 if (block
!= first_block
+ block_in_page
) {
1091 first_block
>>= (PAGE_SHIFT
- blkbits
);
1092 if (page_no
) { /* exclude the header page */
1093 if (first_block
< lowest_block
)
1094 lowest_block
= first_block
;
1095 if (first_block
> highest_block
)
1096 highest_block
= first_block
;
1100 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1102 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1107 probe_block
+= blocks_per_page
;
1112 *span
= 1 + highest_block
- lowest_block
;
1114 page_no
= 1; /* force Empty message */
1116 sis
->pages
= page_no
- 1;
1117 sis
->highest_bit
= page_no
- 1;
1119 sis
->curr_swap_extent
= list_entry(sis
->extent_list
.prev
,
1120 struct swap_extent
, list
);
1123 printk(KERN_ERR
"swapon: swapfile has holes\n");
1129 #if 0 /* We don't need this yet */
1130 #include <linux/backing-dev.h>
1131 int page_queue_congested(struct page
*page
)
1133 struct backing_dev_info
*bdi
;
1135 BUG_ON(!PageLocked(page
)); /* It pins the swap_info_struct */
1137 if (PageSwapCache(page
)) {
1138 swp_entry_t entry
= { .val
= page_private(page
) };
1139 struct swap_info_struct
*sis
;
1141 sis
= get_swap_info_struct(swp_type(entry
));
1142 bdi
= sis
->bdev
->bd_inode
->i_mapping
->backing_dev_info
;
1144 bdi
= page
->mapping
->backing_dev_info
;
1145 return bdi_write_congested(bdi
);
1149 asmlinkage
long sys_swapoff(const char __user
* specialfile
)
1151 struct swap_info_struct
* p
= NULL
;
1152 unsigned short *swap_map
;
1153 struct file
*swap_file
, *victim
;
1154 struct address_space
*mapping
;
1155 struct inode
*inode
;
1160 if (!capable(CAP_SYS_ADMIN
))
1163 pathname
= getname(specialfile
);
1164 err
= PTR_ERR(pathname
);
1165 if (IS_ERR(pathname
))
1168 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1170 err
= PTR_ERR(victim
);
1174 mapping
= victim
->f_mapping
;
1176 spin_lock(&swap_lock
);
1177 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
].next
) {
1178 p
= swap_info
+ type
;
1179 if ((p
->flags
& SWP_ACTIVE
) == SWP_ACTIVE
) {
1180 if (p
->swap_file
->f_mapping
== mapping
)
1187 spin_unlock(&swap_lock
);
1190 if (!security_vm_enough_memory(p
->pages
))
1191 vm_unacct_memory(p
->pages
);
1194 spin_unlock(&swap_lock
);
1198 swap_list
.head
= p
->next
;
1200 swap_info
[prev
].next
= p
->next
;
1202 if (type
== swap_list
.next
) {
1203 /* just pick something that's safe... */
1204 swap_list
.next
= swap_list
.head
;
1206 nr_swap_pages
-= p
->pages
;
1207 total_swap_pages
-= p
->pages
;
1208 p
->flags
&= ~SWP_WRITEOK
;
1209 spin_unlock(&swap_lock
);
1211 current
->flags
|= PF_SWAPOFF
;
1212 err
= try_to_unuse(type
);
1213 current
->flags
&= ~PF_SWAPOFF
;
1216 /* re-insert swap space back into swap_list */
1217 spin_lock(&swap_lock
);
1218 for (prev
= -1, i
= swap_list
.head
; i
>= 0; prev
= i
, i
= swap_info
[i
].next
)
1219 if (p
->prio
>= swap_info
[i
].prio
)
1223 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1225 swap_info
[prev
].next
= p
- swap_info
;
1226 nr_swap_pages
+= p
->pages
;
1227 total_swap_pages
+= p
->pages
;
1228 p
->flags
|= SWP_WRITEOK
;
1229 spin_unlock(&swap_lock
);
1233 /* wait for any unplug function to finish */
1234 down_write(&swap_unplug_sem
);
1235 up_write(&swap_unplug_sem
);
1237 destroy_swap_extents(p
);
1238 mutex_lock(&swapon_mutex
);
1239 spin_lock(&swap_lock
);
1242 /* wait for anyone still in scan_swap_map */
1243 p
->highest_bit
= 0; /* cuts scans short */
1244 while (p
->flags
>= SWP_SCANNING
) {
1245 spin_unlock(&swap_lock
);
1246 schedule_timeout_uninterruptible(1);
1247 spin_lock(&swap_lock
);
1250 swap_file
= p
->swap_file
;
1251 p
->swap_file
= NULL
;
1253 swap_map
= p
->swap_map
;
1256 spin_unlock(&swap_lock
);
1257 mutex_unlock(&swapon_mutex
);
1259 inode
= mapping
->host
;
1260 if (S_ISBLK(inode
->i_mode
)) {
1261 struct block_device
*bdev
= I_BDEV(inode
);
1262 set_blocksize(bdev
, p
->old_block_size
);
1265 mutex_lock(&inode
->i_mutex
);
1266 inode
->i_flags
&= ~S_SWAPFILE
;
1267 mutex_unlock(&inode
->i_mutex
);
1269 filp_close(swap_file
, NULL
);
1273 filp_close(victim
, NULL
);
1278 #ifdef CONFIG_PROC_FS
1280 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1282 struct swap_info_struct
*ptr
= swap_info
;
1286 mutex_lock(&swapon_mutex
);
1288 for (i
= 0; i
< nr_swapfiles
; i
++, ptr
++) {
1289 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1298 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1300 struct swap_info_struct
*ptr
= v
;
1301 struct swap_info_struct
*endptr
= swap_info
+ nr_swapfiles
;
1303 for (++ptr
; ptr
< endptr
; ptr
++) {
1304 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1313 static void swap_stop(struct seq_file
*swap
, void *v
)
1315 mutex_unlock(&swapon_mutex
);
1318 static int swap_show(struct seq_file
*swap
, void *v
)
1320 struct swap_info_struct
*ptr
= v
;
1325 seq_puts(swap
, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1327 file
= ptr
->swap_file
;
1328 len
= seq_path(swap
, file
->f_vfsmnt
, file
->f_dentry
, " \t\n\\");
1329 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1330 len
< 40 ? 40 - len
: 1, " ",
1331 S_ISBLK(file
->f_dentry
->d_inode
->i_mode
) ?
1332 "partition" : "file\t",
1333 ptr
->pages
<< (PAGE_SHIFT
- 10),
1334 ptr
->inuse_pages
<< (PAGE_SHIFT
- 10),
1339 static struct seq_operations swaps_op
= {
1340 .start
= swap_start
,
1346 static int swaps_open(struct inode
*inode
, struct file
*file
)
1348 return seq_open(file
, &swaps_op
);
1351 static struct file_operations proc_swaps_operations
= {
1354 .llseek
= seq_lseek
,
1355 .release
= seq_release
,
1358 static int __init
procswaps_init(void)
1360 struct proc_dir_entry
*entry
;
1362 entry
= create_proc_entry("swaps", 0, NULL
);
1364 entry
->proc_fops
= &proc_swaps_operations
;
1367 __initcall(procswaps_init
);
1368 #endif /* CONFIG_PROC_FS */
1371 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1373 * The swapon system call
1375 asmlinkage
long sys_swapon(const char __user
* specialfile
, int swap_flags
)
1377 struct swap_info_struct
* p
;
1379 struct block_device
*bdev
= NULL
;
1380 struct file
*swap_file
= NULL
;
1381 struct address_space
*mapping
;
1385 static int least_priority
;
1386 union swap_header
*swap_header
= NULL
;
1387 int swap_header_version
;
1388 unsigned int nr_good_pages
= 0;
1391 unsigned long maxpages
= 1;
1393 unsigned short *swap_map
;
1394 struct page
*page
= NULL
;
1395 struct inode
*inode
= NULL
;
1398 if (!capable(CAP_SYS_ADMIN
))
1400 spin_lock(&swap_lock
);
1402 for (type
= 0 ; type
< nr_swapfiles
; type
++,p
++)
1403 if (!(p
->flags
& SWP_USED
))
1406 if (type
>= MAX_SWAPFILES
) {
1407 spin_unlock(&swap_lock
);
1410 if (type
>= nr_swapfiles
)
1411 nr_swapfiles
= type
+1;
1412 INIT_LIST_HEAD(&p
->extent_list
);
1413 p
->flags
= SWP_USED
;
1414 p
->swap_file
= NULL
;
1415 p
->old_block_size
= 0;
1422 if (swap_flags
& SWAP_FLAG_PREFER
) {
1424 (swap_flags
& SWAP_FLAG_PRIO_MASK
)>>SWAP_FLAG_PRIO_SHIFT
;
1426 p
->prio
= --least_priority
;
1428 spin_unlock(&swap_lock
);
1429 name
= getname(specialfile
);
1430 error
= PTR_ERR(name
);
1435 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1436 error
= PTR_ERR(swap_file
);
1437 if (IS_ERR(swap_file
)) {
1442 p
->swap_file
= swap_file
;
1443 mapping
= swap_file
->f_mapping
;
1444 inode
= mapping
->host
;
1447 for (i
= 0; i
< nr_swapfiles
; i
++) {
1448 struct swap_info_struct
*q
= &swap_info
[i
];
1450 if (i
== type
|| !q
->swap_file
)
1452 if (mapping
== q
->swap_file
->f_mapping
)
1457 if (S_ISBLK(inode
->i_mode
)) {
1458 bdev
= I_BDEV(inode
);
1459 error
= bd_claim(bdev
, sys_swapon
);
1465 p
->old_block_size
= block_size(bdev
);
1466 error
= set_blocksize(bdev
, PAGE_SIZE
);
1470 } else if (S_ISREG(inode
->i_mode
)) {
1471 p
->bdev
= inode
->i_sb
->s_bdev
;
1472 mutex_lock(&inode
->i_mutex
);
1474 if (IS_SWAPFILE(inode
)) {
1482 swapfilesize
= i_size_read(inode
) >> PAGE_SHIFT
;
1485 * Read the swap header.
1487 if (!mapping
->a_ops
->readpage
) {
1491 page
= read_cache_page(mapping
, 0,
1492 (filler_t
*)mapping
->a_ops
->readpage
, swap_file
);
1494 error
= PTR_ERR(page
);
1497 wait_on_page_locked(page
);
1498 if (!PageUptodate(page
))
1501 swap_header
= page_address(page
);
1503 if (!memcmp("SWAP-SPACE",swap_header
->magic
.magic
,10))
1504 swap_header_version
= 1;
1505 else if (!memcmp("SWAPSPACE2",swap_header
->magic
.magic
,10))
1506 swap_header_version
= 2;
1508 printk(KERN_ERR
"Unable to find swap-space signature\n");
1513 switch (swap_header_version
) {
1515 printk(KERN_ERR
"version 0 swap is no longer supported. "
1516 "Use mkswap -v1 %s\n", name
);
1520 /* Check the swap header's sub-version and the size of
1521 the swap file and bad block lists */
1522 if (swap_header
->info
.version
!= 1) {
1524 "Unable to handle swap header version %d\n",
1525 swap_header
->info
.version
);
1531 p
->cluster_next
= 1;
1534 * Find out how many pages are allowed for a single swap
1535 * device. There are two limiting factors: 1) the number of
1536 * bits for the swap offset in the swp_entry_t type and
1537 * 2) the number of bits in the a swap pte as defined by
1538 * the different architectures. In order to find the
1539 * largest possible bit mask a swap entry with swap type 0
1540 * and swap offset ~0UL is created, encoded to a swap pte,
1541 * decoded to a swp_entry_t again and finally the swap
1542 * offset is extracted. This will mask all the bits from
1543 * the initial ~0UL mask that can't be encoded in either
1544 * the swp_entry_t or the architecture definition of a
1547 maxpages
= swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1548 if (maxpages
> swap_header
->info
.last_page
)
1549 maxpages
= swap_header
->info
.last_page
;
1550 p
->highest_bit
= maxpages
- 1;
1555 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1557 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1560 /* OK, set up the swap map and apply the bad block list */
1561 if (!(p
->swap_map
= vmalloc(maxpages
* sizeof(short)))) {
1567 memset(p
->swap_map
, 0, maxpages
* sizeof(short));
1568 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
1569 int page_nr
= swap_header
->info
.badpages
[i
];
1570 if (page_nr
<= 0 || page_nr
>= swap_header
->info
.last_page
)
1573 p
->swap_map
[page_nr
] = SWAP_MAP_BAD
;
1575 nr_good_pages
= swap_header
->info
.last_page
-
1576 swap_header
->info
.nr_badpages
-
1577 1 /* header page */;
1582 if (swapfilesize
&& maxpages
> swapfilesize
) {
1584 "Swap area shorter than signature indicates\n");
1588 if (nr_good_pages
) {
1589 p
->swap_map
[0] = SWAP_MAP_BAD
;
1591 p
->pages
= nr_good_pages
;
1592 nr_extents
= setup_swap_extents(p
, &span
);
1593 if (nr_extents
< 0) {
1597 nr_good_pages
= p
->pages
;
1599 if (!nr_good_pages
) {
1600 printk(KERN_WARNING
"Empty swap-file\n");
1605 mutex_lock(&swapon_mutex
);
1606 spin_lock(&swap_lock
);
1607 p
->flags
= SWP_ACTIVE
;
1608 nr_swap_pages
+= nr_good_pages
;
1609 total_swap_pages
+= nr_good_pages
;
1611 printk(KERN_INFO
"Adding %uk swap on %s. "
1612 "Priority:%d extents:%d across:%lluk\n",
1613 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
1614 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10));
1616 /* insert swap space into swap_list: */
1618 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1619 if (p
->prio
>= swap_info
[i
].prio
) {
1626 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1628 swap_info
[prev
].next
= p
- swap_info
;
1630 spin_unlock(&swap_lock
);
1631 mutex_unlock(&swapon_mutex
);
1636 set_blocksize(bdev
, p
->old_block_size
);
1639 destroy_swap_extents(p
);
1641 spin_lock(&swap_lock
);
1642 swap_map
= p
->swap_map
;
1643 p
->swap_file
= NULL
;
1646 if (!(swap_flags
& SWAP_FLAG_PREFER
))
1648 spin_unlock(&swap_lock
);
1651 filp_close(swap_file
, NULL
);
1653 if (page
&& !IS_ERR(page
)) {
1655 page_cache_release(page
);
1661 inode
->i_flags
|= S_SWAPFILE
;
1662 mutex_unlock(&inode
->i_mutex
);
1667 void si_swapinfo(struct sysinfo
*val
)
1670 unsigned long nr_to_be_unused
= 0;
1672 spin_lock(&swap_lock
);
1673 for (i
= 0; i
< nr_swapfiles
; i
++) {
1674 if (!(swap_info
[i
].flags
& SWP_USED
) ||
1675 (swap_info
[i
].flags
& SWP_WRITEOK
))
1677 nr_to_be_unused
+= swap_info
[i
].inuse_pages
;
1679 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
1680 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
1681 spin_unlock(&swap_lock
);
1685 * Verify that a swap entry is valid and increment its swap map count.
1687 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1688 * "permanent", but will be reclaimed by the next swapoff.
1690 int swap_duplicate(swp_entry_t entry
)
1692 struct swap_info_struct
* p
;
1693 unsigned long offset
, type
;
1696 if (is_migration_entry(entry
))
1699 type
= swp_type(entry
);
1700 if (type
>= nr_swapfiles
)
1702 p
= type
+ swap_info
;
1703 offset
= swp_offset(entry
);
1705 spin_lock(&swap_lock
);
1706 if (offset
< p
->max
&& p
->swap_map
[offset
]) {
1707 if (p
->swap_map
[offset
] < SWAP_MAP_MAX
- 1) {
1708 p
->swap_map
[offset
]++;
1710 } else if (p
->swap_map
[offset
] <= SWAP_MAP_MAX
) {
1711 if (swap_overflow
++ < 5)
1712 printk(KERN_WARNING
"swap_dup: swap entry overflow\n");
1713 p
->swap_map
[offset
] = SWAP_MAP_MAX
;
1717 spin_unlock(&swap_lock
);
1722 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
1726 struct swap_info_struct
*
1727 get_swap_info_struct(unsigned type
)
1729 return &swap_info
[type
];
1733 * swap_lock prevents swap_map being freed. Don't grab an extra
1734 * reference on the swaphandle, it doesn't matter if it becomes unused.
1736 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
1738 int ret
= 0, i
= 1 << page_cluster
;
1740 struct swap_info_struct
*swapdev
= swp_type(entry
) + swap_info
;
1742 if (!page_cluster
) /* no readahead */
1744 toff
= (swp_offset(entry
) >> page_cluster
) << page_cluster
;
1745 if (!toff
) /* first page is swap header */
1749 spin_lock(&swap_lock
);
1751 /* Don't read-ahead past the end of the swap area */
1752 if (toff
>= swapdev
->max
)
1754 /* Don't read in free or bad pages */
1755 if (!swapdev
->swap_map
[toff
])
1757 if (swapdev
->swap_map
[toff
] == SWAP_MAP_BAD
)
1762 spin_unlock(&swap_lock
);