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/writeback.h>
20 #include <linux/proc_fs.h>
21 #include <linux/seq_file.h>
22 #include <linux/init.h>
23 #include <linux/module.h>
24 #include <linux/rmap.h>
25 #include <linux/security.h>
26 #include <linux/backing-dev.h>
27 #include <linux/mutex.h>
28 #include <linux/capability.h>
29 #include <linux/syscalls.h>
30 #include <linux/memcontrol.h>
32 #include <asm/pgtable.h>
33 #include <asm/tlbflush.h>
34 #include <linux/swapops.h>
36 static DEFINE_SPINLOCK(swap_lock
);
37 static unsigned int nr_swapfiles
;
39 long total_swap_pages
;
40 static int swap_overflow
;
41 static int least_priority
;
43 static const char Bad_file
[] = "Bad swap file entry ";
44 static const char Unused_file
[] = "Unused swap file entry ";
45 static const char Bad_offset
[] = "Bad swap offset entry ";
46 static const char Unused_offset
[] = "Unused swap offset entry ";
48 static struct swap_list_t swap_list
= {-1, -1};
50 static struct swap_info_struct swap_info
[MAX_SWAPFILES
];
52 static DEFINE_MUTEX(swapon_mutex
);
55 * We need this because the bdev->unplug_fn can sleep and we cannot
56 * hold swap_lock while calling the unplug_fn. And swap_lock
57 * cannot be turned into a mutex.
59 static DECLARE_RWSEM(swap_unplug_sem
);
61 void swap_unplug_io_fn(struct backing_dev_info
*unused_bdi
, struct page
*page
)
65 down_read(&swap_unplug_sem
);
66 entry
.val
= page_private(page
);
67 if (PageSwapCache(page
)) {
68 struct block_device
*bdev
= swap_info
[swp_type(entry
)].bdev
;
69 struct backing_dev_info
*bdi
;
72 * If the page is removed from swapcache from under us (with a
73 * racy try_to_unuse/swapoff) we need an additional reference
74 * count to avoid reading garbage from page_private(page) above.
75 * If the WARN_ON triggers during a swapoff it maybe the race
76 * condition and it's harmless. However if it triggers without
77 * swapoff it signals a problem.
79 WARN_ON(page_count(page
) <= 1);
81 bdi
= bdev
->bd_inode
->i_mapping
->backing_dev_info
;
82 blk_run_backing_dev(bdi
, page
);
84 up_read(&swap_unplug_sem
);
87 #define SWAPFILE_CLUSTER 256
88 #define LATENCY_LIMIT 256
90 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
)
92 unsigned long offset
, last_in_cluster
;
93 int latency_ration
= LATENCY_LIMIT
;
96 * We try to cluster swap pages by allocating them sequentially
97 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
98 * way, however, we resort to first-free allocation, starting
99 * a new cluster. This prevents us from scattering swap pages
100 * all over the entire swap partition, so that we reduce
101 * overall disk seek times between swap pages. -- sct
102 * But we do now try to find an empty cluster. -Andrea
105 si
->flags
+= SWP_SCANNING
;
106 if (unlikely(!si
->cluster_nr
)) {
107 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
108 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
)
110 spin_unlock(&swap_lock
);
112 offset
= si
->lowest_bit
;
113 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
115 /* Locate the first empty (unaligned) cluster */
116 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
117 if (si
->swap_map
[offset
])
118 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
119 else if (offset
== last_in_cluster
) {
120 spin_lock(&swap_lock
);
121 si
->cluster_next
= offset
-SWAPFILE_CLUSTER
+1;
124 if (unlikely(--latency_ration
< 0)) {
126 latency_ration
= LATENCY_LIMIT
;
129 spin_lock(&swap_lock
);
135 offset
= si
->cluster_next
;
136 if (offset
> si
->highest_bit
)
137 lowest
: offset
= si
->lowest_bit
;
138 checks
: if (!(si
->flags
& SWP_WRITEOK
))
140 if (!si
->highest_bit
)
142 if (!si
->swap_map
[offset
]) {
143 if (offset
== si
->lowest_bit
)
145 if (offset
== si
->highest_bit
)
148 if (si
->inuse_pages
== si
->pages
) {
149 si
->lowest_bit
= si
->max
;
152 si
->swap_map
[offset
] = 1;
153 si
->cluster_next
= offset
+ 1;
154 si
->flags
-= SWP_SCANNING
;
158 spin_unlock(&swap_lock
);
159 while (++offset
<= si
->highest_bit
) {
160 if (!si
->swap_map
[offset
]) {
161 spin_lock(&swap_lock
);
164 if (unlikely(--latency_ration
< 0)) {
166 latency_ration
= LATENCY_LIMIT
;
169 spin_lock(&swap_lock
);
173 si
->flags
-= SWP_SCANNING
;
177 swp_entry_t
get_swap_page(void)
179 struct swap_info_struct
*si
;
184 spin_lock(&swap_lock
);
185 if (nr_swap_pages
<= 0)
189 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
190 si
= swap_info
+ type
;
193 (!wrapped
&& si
->prio
!= swap_info
[next
].prio
)) {
194 next
= swap_list
.head
;
198 if (!si
->highest_bit
)
200 if (!(si
->flags
& SWP_WRITEOK
))
203 swap_list
.next
= next
;
204 offset
= scan_swap_map(si
);
206 spin_unlock(&swap_lock
);
207 return swp_entry(type
, offset
);
209 next
= swap_list
.next
;
214 spin_unlock(&swap_lock
);
215 return (swp_entry_t
) {0};
218 swp_entry_t
get_swap_page_of_type(int type
)
220 struct swap_info_struct
*si
;
223 spin_lock(&swap_lock
);
224 si
= swap_info
+ type
;
225 if (si
->flags
& SWP_WRITEOK
) {
227 offset
= scan_swap_map(si
);
229 spin_unlock(&swap_lock
);
230 return swp_entry(type
, offset
);
234 spin_unlock(&swap_lock
);
235 return (swp_entry_t
) {0};
238 static struct swap_info_struct
* swap_info_get(swp_entry_t entry
)
240 struct swap_info_struct
* p
;
241 unsigned long offset
, type
;
245 type
= swp_type(entry
);
246 if (type
>= nr_swapfiles
)
248 p
= & swap_info
[type
];
249 if (!(p
->flags
& SWP_USED
))
251 offset
= swp_offset(entry
);
252 if (offset
>= p
->max
)
254 if (!p
->swap_map
[offset
])
256 spin_lock(&swap_lock
);
260 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
263 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
266 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
269 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
274 static int swap_entry_free(struct swap_info_struct
*p
, unsigned long offset
)
276 int count
= p
->swap_map
[offset
];
278 if (count
< SWAP_MAP_MAX
) {
280 p
->swap_map
[offset
] = count
;
282 if (offset
< p
->lowest_bit
)
283 p
->lowest_bit
= offset
;
284 if (offset
> p
->highest_bit
)
285 p
->highest_bit
= offset
;
286 if (p
->prio
> swap_info
[swap_list
.next
].prio
)
287 swap_list
.next
= p
- swap_info
;
296 * Caller has made sure that the swapdevice corresponding to entry
297 * is still around or has not been recycled.
299 void swap_free(swp_entry_t entry
)
301 struct swap_info_struct
* p
;
303 p
= swap_info_get(entry
);
305 swap_entry_free(p
, swp_offset(entry
));
306 spin_unlock(&swap_lock
);
311 * How many references to page are currently swapped out?
313 static inline int page_swapcount(struct page
*page
)
316 struct swap_info_struct
*p
;
319 entry
.val
= page_private(page
);
320 p
= swap_info_get(entry
);
322 /* Subtract the 1 for the swap cache itself */
323 count
= p
->swap_map
[swp_offset(entry
)] - 1;
324 spin_unlock(&swap_lock
);
330 * We can write to an anon page without COW if there are no other references
331 * to it. And as a side-effect, free up its swap: because the old content
332 * on disk will never be read, and seeking back there to write new content
333 * later would only waste time away from clustering.
335 int reuse_swap_page(struct page
*page
)
339 VM_BUG_ON(!PageLocked(page
));
340 count
= page_mapcount(page
);
341 if (count
<= 1 && PageSwapCache(page
)) {
342 count
+= page_swapcount(page
);
343 if (count
== 1 && !PageWriteback(page
)) {
344 delete_from_swap_cache(page
);
352 * If swap is getting full, or if there are no more mappings of this page,
353 * then try_to_free_swap is called to free its swap space.
355 int try_to_free_swap(struct page
*page
)
357 VM_BUG_ON(!PageLocked(page
));
359 if (!PageSwapCache(page
))
361 if (PageWriteback(page
))
363 if (page_swapcount(page
))
366 delete_from_swap_cache(page
);
372 * Free the swap entry like above, but also try to
373 * free the page cache entry if it is the last user.
375 void free_swap_and_cache(swp_entry_t entry
)
377 struct swap_info_struct
* p
;
378 struct page
*page
= NULL
;
380 if (is_migration_entry(entry
))
383 p
= swap_info_get(entry
);
385 if (swap_entry_free(p
, swp_offset(entry
)) == 1) {
386 page
= find_get_page(&swapper_space
, entry
.val
);
387 if (page
&& !trylock_page(page
)) {
388 page_cache_release(page
);
392 spin_unlock(&swap_lock
);
396 * Not mapped elsewhere, or swap space full? Free it!
397 * Also recheck PageSwapCache now page is locked (above).
399 if (PageSwapCache(page
) && !PageWriteback(page
) &&
400 (!page_mapped(page
) || vm_swap_full())) {
401 delete_from_swap_cache(page
);
405 page_cache_release(page
);
409 #ifdef CONFIG_HIBERNATION
411 * Find the swap type that corresponds to given device (if any).
413 * @offset - number of the PAGE_SIZE-sized block of the device, starting
414 * from 0, in which the swap header is expected to be located.
416 * This is needed for the suspend to disk (aka swsusp).
418 int swap_type_of(dev_t device
, sector_t offset
, struct block_device
**bdev_p
)
420 struct block_device
*bdev
= NULL
;
424 bdev
= bdget(device
);
426 spin_lock(&swap_lock
);
427 for (i
= 0; i
< nr_swapfiles
; i
++) {
428 struct swap_info_struct
*sis
= swap_info
+ i
;
430 if (!(sis
->flags
& SWP_WRITEOK
))
437 spin_unlock(&swap_lock
);
440 if (bdev
== sis
->bdev
) {
441 struct swap_extent
*se
;
443 se
= list_entry(sis
->extent_list
.next
,
444 struct swap_extent
, list
);
445 if (se
->start_block
== offset
) {
449 spin_unlock(&swap_lock
);
455 spin_unlock(&swap_lock
);
463 * Return either the total number of swap pages of given type, or the number
464 * of free pages of that type (depending on @free)
466 * This is needed for software suspend
468 unsigned int count_swap_pages(int type
, int free
)
472 if (type
< nr_swapfiles
) {
473 spin_lock(&swap_lock
);
474 if (swap_info
[type
].flags
& SWP_WRITEOK
) {
475 n
= swap_info
[type
].pages
;
477 n
-= swap_info
[type
].inuse_pages
;
479 spin_unlock(&swap_lock
);
486 * No need to decide whether this PTE shares the swap entry with others,
487 * just let do_wp_page work it out if a write is requested later - to
488 * force COW, vm_page_prot omits write permission from any private vma.
490 static int unuse_pte(struct vm_area_struct
*vma
, pmd_t
*pmd
,
491 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
497 if (mem_cgroup_charge(page
, vma
->vm_mm
, GFP_KERNEL
))
500 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
501 if (unlikely(!pte_same(*pte
, swp_entry_to_pte(entry
)))) {
503 mem_cgroup_uncharge_page(page
);
508 inc_mm_counter(vma
->vm_mm
, anon_rss
);
510 set_pte_at(vma
->vm_mm
, addr
, pte
,
511 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
512 page_add_anon_rmap(page
, vma
, addr
);
515 * Move the page to the active list so it is not
516 * immediately swapped out again after swapon.
520 pte_unmap_unlock(pte
, ptl
);
524 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
525 unsigned long addr
, unsigned long end
,
526 swp_entry_t entry
, struct page
*page
)
528 pte_t swp_pte
= swp_entry_to_pte(entry
);
533 * We don't actually need pte lock while scanning for swp_pte: since
534 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
535 * page table while we're scanning; though it could get zapped, and on
536 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
537 * of unmatched parts which look like swp_pte, so unuse_pte must
538 * recheck under pte lock. Scanning without pte lock lets it be
539 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
541 pte
= pte_offset_map(pmd
, addr
);
544 * swapoff spends a _lot_ of time in this loop!
545 * Test inline before going to call unuse_pte.
547 if (unlikely(pte_same(*pte
, swp_pte
))) {
549 ret
= unuse_pte(vma
, pmd
, addr
, entry
, page
);
552 pte
= pte_offset_map(pmd
, addr
);
554 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
560 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
561 unsigned long addr
, unsigned long end
,
562 swp_entry_t entry
, struct page
*page
)
568 pmd
= pmd_offset(pud
, addr
);
570 next
= pmd_addr_end(addr
, end
);
571 if (pmd_none_or_clear_bad(pmd
))
573 ret
= unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
);
576 } while (pmd
++, addr
= next
, addr
!= end
);
580 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
581 unsigned long addr
, unsigned long end
,
582 swp_entry_t entry
, struct page
*page
)
588 pud
= pud_offset(pgd
, addr
);
590 next
= pud_addr_end(addr
, end
);
591 if (pud_none_or_clear_bad(pud
))
593 ret
= unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
);
596 } while (pud
++, addr
= next
, addr
!= end
);
600 static int unuse_vma(struct vm_area_struct
*vma
,
601 swp_entry_t entry
, struct page
*page
)
604 unsigned long addr
, end
, next
;
608 addr
= page_address_in_vma(page
, vma
);
612 end
= addr
+ PAGE_SIZE
;
614 addr
= vma
->vm_start
;
618 pgd
= pgd_offset(vma
->vm_mm
, addr
);
620 next
= pgd_addr_end(addr
, end
);
621 if (pgd_none_or_clear_bad(pgd
))
623 ret
= unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
);
626 } while (pgd
++, addr
= next
, addr
!= end
);
630 static int unuse_mm(struct mm_struct
*mm
,
631 swp_entry_t entry
, struct page
*page
)
633 struct vm_area_struct
*vma
;
636 if (!down_read_trylock(&mm
->mmap_sem
)) {
638 * Activate page so shrink_inactive_list is unlikely to unmap
639 * its ptes while lock is dropped, so swapoff can make progress.
643 down_read(&mm
->mmap_sem
);
646 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
647 if (vma
->anon_vma
&& (ret
= unuse_vma(vma
, entry
, page
)))
650 up_read(&mm
->mmap_sem
);
651 return (ret
< 0)? ret
: 0;
655 * Scan swap_map from current position to next entry still in use.
656 * Recycle to start on reaching the end, returning 0 when empty.
658 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
661 unsigned int max
= si
->max
;
662 unsigned int i
= prev
;
666 * No need for swap_lock here: we're just looking
667 * for whether an entry is in use, not modifying it; false
668 * hits are okay, and sys_swapoff() has already prevented new
669 * allocations from this area (while holding swap_lock).
678 * No entries in use at top of swap_map,
679 * loop back to start and recheck there.
685 count
= si
->swap_map
[i
];
686 if (count
&& count
!= SWAP_MAP_BAD
)
693 * We completely avoid races by reading each swap page in advance,
694 * and then search for the process using it. All the necessary
695 * page table adjustments can then be made atomically.
697 static int try_to_unuse(unsigned int type
)
699 struct swap_info_struct
* si
= &swap_info
[type
];
700 struct mm_struct
*start_mm
;
701 unsigned short *swap_map
;
702 unsigned short swcount
;
707 int reset_overflow
= 0;
711 * When searching mms for an entry, a good strategy is to
712 * start at the first mm we freed the previous entry from
713 * (though actually we don't notice whether we or coincidence
714 * freed the entry). Initialize this start_mm with a hold.
716 * A simpler strategy would be to start at the last mm we
717 * freed the previous entry from; but that would take less
718 * advantage of mmlist ordering, which clusters forked mms
719 * together, child after parent. If we race with dup_mmap(), we
720 * prefer to resolve parent before child, lest we miss entries
721 * duplicated after we scanned child: using last mm would invert
722 * that. Though it's only a serious concern when an overflowed
723 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
726 atomic_inc(&init_mm
.mm_users
);
729 * Keep on scanning until all entries have gone. Usually,
730 * one pass through swap_map is enough, but not necessarily:
731 * there are races when an instance of an entry might be missed.
733 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
734 if (signal_pending(current
)) {
740 * Get a page for the entry, using the existing swap
741 * cache page if there is one. Otherwise, get a clean
742 * page and read the swap into it.
744 swap_map
= &si
->swap_map
[i
];
745 entry
= swp_entry(type
, i
);
746 page
= read_swap_cache_async(entry
,
747 GFP_HIGHUSER_MOVABLE
, NULL
, 0);
750 * Either swap_duplicate() failed because entry
751 * has been freed independently, and will not be
752 * reused since sys_swapoff() already disabled
753 * allocation from here, or alloc_page() failed.
762 * Don't hold on to start_mm if it looks like exiting.
764 if (atomic_read(&start_mm
->mm_users
) == 1) {
767 atomic_inc(&init_mm
.mm_users
);
771 * Wait for and lock page. When do_swap_page races with
772 * try_to_unuse, do_swap_page can handle the fault much
773 * faster than try_to_unuse can locate the entry. This
774 * apparently redundant "wait_on_page_locked" lets try_to_unuse
775 * defer to do_swap_page in such a case - in some tests,
776 * do_swap_page and try_to_unuse repeatedly compete.
778 wait_on_page_locked(page
);
779 wait_on_page_writeback(page
);
781 wait_on_page_writeback(page
);
784 * Remove all references to entry.
785 * Whenever we reach init_mm, there's no address space
786 * to search, but use it as a reminder to search shmem.
791 if (start_mm
== &init_mm
)
792 shmem
= shmem_unuse(entry
, page
);
794 retval
= unuse_mm(start_mm
, entry
, page
);
797 int set_start_mm
= (*swap_map
>= swcount
);
798 struct list_head
*p
= &start_mm
->mmlist
;
799 struct mm_struct
*new_start_mm
= start_mm
;
800 struct mm_struct
*prev_mm
= start_mm
;
801 struct mm_struct
*mm
;
803 atomic_inc(&new_start_mm
->mm_users
);
804 atomic_inc(&prev_mm
->mm_users
);
805 spin_lock(&mmlist_lock
);
806 while (*swap_map
> 1 && !retval
&& !shmem
&&
807 (p
= p
->next
) != &start_mm
->mmlist
) {
808 mm
= list_entry(p
, struct mm_struct
, mmlist
);
809 if (!atomic_inc_not_zero(&mm
->mm_users
))
811 spin_unlock(&mmlist_lock
);
820 else if (mm
== &init_mm
) {
822 shmem
= shmem_unuse(entry
, page
);
824 retval
= unuse_mm(mm
, entry
, page
);
825 if (set_start_mm
&& *swap_map
< swcount
) {
827 atomic_inc(&mm
->mm_users
);
831 spin_lock(&mmlist_lock
);
833 spin_unlock(&mmlist_lock
);
836 start_mm
= new_start_mm
;
839 /* page has already been unlocked and released */
847 page_cache_release(page
);
852 * How could swap count reach 0x7fff when the maximum
853 * pid is 0x7fff, and there's no way to repeat a swap
854 * page within an mm (except in shmem, where it's the
855 * shared object which takes the reference count)?
856 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
858 * If that's wrong, then we should worry more about
859 * exit_mmap() and do_munmap() cases described above:
860 * we might be resetting SWAP_MAP_MAX too early here.
861 * We know "Undead"s can happen, they're okay, so don't
862 * report them; but do report if we reset SWAP_MAP_MAX.
864 if (*swap_map
== SWAP_MAP_MAX
) {
865 spin_lock(&swap_lock
);
867 spin_unlock(&swap_lock
);
872 * If a reference remains (rare), we would like to leave
873 * the page in the swap cache; but try_to_unmap could
874 * then re-duplicate the entry once we drop page lock,
875 * so we might loop indefinitely; also, that page could
876 * not be swapped out to other storage meanwhile. So:
877 * delete from cache even if there's another reference,
878 * after ensuring that the data has been saved to disk -
879 * since if the reference remains (rarer), it will be
880 * read from disk into another page. Splitting into two
881 * pages would be incorrect if swap supported "shared
882 * private" pages, but they are handled by tmpfs files.
884 if ((*swap_map
> 1) && PageDirty(page
) && PageSwapCache(page
)) {
885 struct writeback_control wbc
= {
886 .sync_mode
= WB_SYNC_NONE
,
889 swap_writepage(page
, &wbc
);
891 wait_on_page_writeback(page
);
895 * It is conceivable that a racing task removed this page from
896 * swap cache just before we acquired the page lock at the top,
897 * or while we dropped it in unuse_mm(). The page might even
898 * be back in swap cache on another swap area: that we must not
899 * delete, since it may not have been written out to swap yet.
901 if (PageSwapCache(page
) &&
902 likely(page_private(page
) == entry
.val
))
903 delete_from_swap_cache(page
);
906 * So we could skip searching mms once swap count went
907 * to 1, we did not mark any present ptes as dirty: must
908 * mark page dirty so shrink_page_list will preserve it.
912 page_cache_release(page
);
915 * Make sure that we aren't completely killing
916 * interactive performance.
922 if (reset_overflow
) {
923 printk(KERN_WARNING
"swapoff: cleared swap entry overflow\n");
930 * After a successful try_to_unuse, if no swap is now in use, we know
931 * we can empty the mmlist. swap_lock must be held on entry and exit.
932 * Note that mmlist_lock nests inside swap_lock, and an mm must be
933 * added to the mmlist just after page_duplicate - before would be racy.
935 static void drain_mmlist(void)
937 struct list_head
*p
, *next
;
940 for (i
= 0; i
< nr_swapfiles
; i
++)
941 if (swap_info
[i
].inuse_pages
)
943 spin_lock(&mmlist_lock
);
944 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
946 spin_unlock(&mmlist_lock
);
950 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
951 * corresponds to page offset `offset'.
953 sector_t
map_swap_page(struct swap_info_struct
*sis
, pgoff_t offset
)
955 struct swap_extent
*se
= sis
->curr_swap_extent
;
956 struct swap_extent
*start_se
= se
;
959 struct list_head
*lh
;
961 if (se
->start_page
<= offset
&&
962 offset
< (se
->start_page
+ se
->nr_pages
)) {
963 return se
->start_block
+ (offset
- se
->start_page
);
966 if (lh
== &sis
->extent_list
)
968 se
= list_entry(lh
, struct swap_extent
, list
);
969 sis
->curr_swap_extent
= se
;
970 BUG_ON(se
== start_se
); /* It *must* be present */
974 #ifdef CONFIG_HIBERNATION
976 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
977 * corresponding to given index in swap_info (swap type).
979 sector_t
swapdev_block(int swap_type
, pgoff_t offset
)
981 struct swap_info_struct
*sis
;
983 if (swap_type
>= nr_swapfiles
)
986 sis
= swap_info
+ swap_type
;
987 return (sis
->flags
& SWP_WRITEOK
) ? map_swap_page(sis
, offset
) : 0;
989 #endif /* CONFIG_HIBERNATION */
992 * Free all of a swapdev's extent information
994 static void destroy_swap_extents(struct swap_info_struct
*sis
)
996 while (!list_empty(&sis
->extent_list
)) {
997 struct swap_extent
*se
;
999 se
= list_entry(sis
->extent_list
.next
,
1000 struct swap_extent
, list
);
1001 list_del(&se
->list
);
1007 * Add a block range (and the corresponding page range) into this swapdev's
1008 * extent list. The extent list is kept sorted in page order.
1010 * This function rather assumes that it is called in ascending page order.
1013 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
1014 unsigned long nr_pages
, sector_t start_block
)
1016 struct swap_extent
*se
;
1017 struct swap_extent
*new_se
;
1018 struct list_head
*lh
;
1020 lh
= sis
->extent_list
.prev
; /* The highest page extent */
1021 if (lh
!= &sis
->extent_list
) {
1022 se
= list_entry(lh
, struct swap_extent
, list
);
1023 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
1024 if (se
->start_block
+ se
->nr_pages
== start_block
) {
1026 se
->nr_pages
+= nr_pages
;
1032 * No merge. Insert a new extent, preserving ordering.
1034 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
1037 new_se
->start_page
= start_page
;
1038 new_se
->nr_pages
= nr_pages
;
1039 new_se
->start_block
= start_block
;
1041 list_add_tail(&new_se
->list
, &sis
->extent_list
);
1046 * A `swap extent' is a simple thing which maps a contiguous range of pages
1047 * onto a contiguous range of disk blocks. An ordered list of swap extents
1048 * is built at swapon time and is then used at swap_writepage/swap_readpage
1049 * time for locating where on disk a page belongs.
1051 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1052 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1053 * swap files identically.
1055 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1056 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1057 * swapfiles are handled *identically* after swapon time.
1059 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1060 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1061 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1062 * requirements, they are simply tossed out - we will never use those blocks
1065 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1066 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1067 * which will scribble on the fs.
1069 * The amount of disk space which a single swap extent represents varies.
1070 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1071 * extents in the list. To avoid much list walking, we cache the previous
1072 * search location in `curr_swap_extent', and start new searches from there.
1073 * This is extremely effective. The average number of iterations in
1074 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1076 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1078 struct inode
*inode
;
1079 unsigned blocks_per_page
;
1080 unsigned long page_no
;
1082 sector_t probe_block
;
1083 sector_t last_block
;
1084 sector_t lowest_block
= -1;
1085 sector_t highest_block
= 0;
1089 inode
= sis
->swap_file
->f_mapping
->host
;
1090 if (S_ISBLK(inode
->i_mode
)) {
1091 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1096 blkbits
= inode
->i_blkbits
;
1097 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1100 * Map all the blocks into the extent list. This code doesn't try
1105 last_block
= i_size_read(inode
) >> blkbits
;
1106 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1107 page_no
< sis
->max
) {
1108 unsigned block_in_page
;
1109 sector_t first_block
;
1111 first_block
= bmap(inode
, probe_block
);
1112 if (first_block
== 0)
1116 * It must be PAGE_SIZE aligned on-disk
1118 if (first_block
& (blocks_per_page
- 1)) {
1123 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1127 block
= bmap(inode
, probe_block
+ block_in_page
);
1130 if (block
!= first_block
+ block_in_page
) {
1137 first_block
>>= (PAGE_SHIFT
- blkbits
);
1138 if (page_no
) { /* exclude the header page */
1139 if (first_block
< lowest_block
)
1140 lowest_block
= first_block
;
1141 if (first_block
> highest_block
)
1142 highest_block
= first_block
;
1146 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1148 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1153 probe_block
+= blocks_per_page
;
1158 *span
= 1 + highest_block
- lowest_block
;
1160 page_no
= 1; /* force Empty message */
1162 sis
->pages
= page_no
- 1;
1163 sis
->highest_bit
= page_no
- 1;
1165 sis
->curr_swap_extent
= list_entry(sis
->extent_list
.prev
,
1166 struct swap_extent
, list
);
1169 printk(KERN_ERR
"swapon: swapfile has holes\n");
1175 #if 0 /* We don't need this yet */
1176 #include <linux/backing-dev.h>
1177 int page_queue_congested(struct page
*page
)
1179 struct backing_dev_info
*bdi
;
1181 VM_BUG_ON(!PageLocked(page
)); /* It pins the swap_info_struct */
1183 if (PageSwapCache(page
)) {
1184 swp_entry_t entry
= { .val
= page_private(page
) };
1185 struct swap_info_struct
*sis
;
1187 sis
= get_swap_info_struct(swp_type(entry
));
1188 bdi
= sis
->bdev
->bd_inode
->i_mapping
->backing_dev_info
;
1190 bdi
= page
->mapping
->backing_dev_info
;
1191 return bdi_write_congested(bdi
);
1195 asmlinkage
long sys_swapoff(const char __user
* specialfile
)
1197 struct swap_info_struct
* p
= NULL
;
1198 unsigned short *swap_map
;
1199 struct file
*swap_file
, *victim
;
1200 struct address_space
*mapping
;
1201 struct inode
*inode
;
1206 if (!capable(CAP_SYS_ADMIN
))
1209 pathname
= getname(specialfile
);
1210 err
= PTR_ERR(pathname
);
1211 if (IS_ERR(pathname
))
1214 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1216 err
= PTR_ERR(victim
);
1220 mapping
= victim
->f_mapping
;
1222 spin_lock(&swap_lock
);
1223 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
].next
) {
1224 p
= swap_info
+ type
;
1225 if (p
->flags
& SWP_WRITEOK
) {
1226 if (p
->swap_file
->f_mapping
== mapping
)
1233 spin_unlock(&swap_lock
);
1236 if (!security_vm_enough_memory(p
->pages
))
1237 vm_unacct_memory(p
->pages
);
1240 spin_unlock(&swap_lock
);
1244 swap_list
.head
= p
->next
;
1246 swap_info
[prev
].next
= p
->next
;
1248 if (type
== swap_list
.next
) {
1249 /* just pick something that's safe... */
1250 swap_list
.next
= swap_list
.head
;
1253 for (i
= p
->next
; i
>= 0; i
= swap_info
[i
].next
)
1254 swap_info
[i
].prio
= p
->prio
--;
1257 nr_swap_pages
-= p
->pages
;
1258 total_swap_pages
-= p
->pages
;
1259 p
->flags
&= ~SWP_WRITEOK
;
1260 spin_unlock(&swap_lock
);
1262 current
->flags
|= PF_SWAPOFF
;
1263 err
= try_to_unuse(type
);
1264 current
->flags
&= ~PF_SWAPOFF
;
1267 /* re-insert swap space back into swap_list */
1268 spin_lock(&swap_lock
);
1270 p
->prio
= --least_priority
;
1272 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1273 if (p
->prio
>= swap_info
[i
].prio
)
1279 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1281 swap_info
[prev
].next
= p
- swap_info
;
1282 nr_swap_pages
+= p
->pages
;
1283 total_swap_pages
+= p
->pages
;
1284 p
->flags
|= SWP_WRITEOK
;
1285 spin_unlock(&swap_lock
);
1289 /* wait for any unplug function to finish */
1290 down_write(&swap_unplug_sem
);
1291 up_write(&swap_unplug_sem
);
1293 destroy_swap_extents(p
);
1294 mutex_lock(&swapon_mutex
);
1295 spin_lock(&swap_lock
);
1298 /* wait for anyone still in scan_swap_map */
1299 p
->highest_bit
= 0; /* cuts scans short */
1300 while (p
->flags
>= SWP_SCANNING
) {
1301 spin_unlock(&swap_lock
);
1302 schedule_timeout_uninterruptible(1);
1303 spin_lock(&swap_lock
);
1306 swap_file
= p
->swap_file
;
1307 p
->swap_file
= NULL
;
1309 swap_map
= p
->swap_map
;
1312 spin_unlock(&swap_lock
);
1313 mutex_unlock(&swapon_mutex
);
1315 inode
= mapping
->host
;
1316 if (S_ISBLK(inode
->i_mode
)) {
1317 struct block_device
*bdev
= I_BDEV(inode
);
1318 set_blocksize(bdev
, p
->old_block_size
);
1321 mutex_lock(&inode
->i_mutex
);
1322 inode
->i_flags
&= ~S_SWAPFILE
;
1323 mutex_unlock(&inode
->i_mutex
);
1325 filp_close(swap_file
, NULL
);
1329 filp_close(victim
, NULL
);
1334 #ifdef CONFIG_PROC_FS
1336 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1338 struct swap_info_struct
*ptr
= swap_info
;
1342 mutex_lock(&swapon_mutex
);
1345 return SEQ_START_TOKEN
;
1347 for (i
= 0; i
< nr_swapfiles
; i
++, ptr
++) {
1348 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1357 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1359 struct swap_info_struct
*ptr
;
1360 struct swap_info_struct
*endptr
= swap_info
+ nr_swapfiles
;
1362 if (v
== SEQ_START_TOKEN
)
1369 for (; ptr
< endptr
; ptr
++) {
1370 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1379 static void swap_stop(struct seq_file
*swap
, void *v
)
1381 mutex_unlock(&swapon_mutex
);
1384 static int swap_show(struct seq_file
*swap
, void *v
)
1386 struct swap_info_struct
*ptr
= v
;
1390 if (ptr
== SEQ_START_TOKEN
) {
1391 seq_puts(swap
,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1395 file
= ptr
->swap_file
;
1396 len
= seq_path(swap
, &file
->f_path
, " \t\n\\");
1397 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1398 len
< 40 ? 40 - len
: 1, " ",
1399 S_ISBLK(file
->f_path
.dentry
->d_inode
->i_mode
) ?
1400 "partition" : "file\t",
1401 ptr
->pages
<< (PAGE_SHIFT
- 10),
1402 ptr
->inuse_pages
<< (PAGE_SHIFT
- 10),
1407 static const struct seq_operations swaps_op
= {
1408 .start
= swap_start
,
1414 static int swaps_open(struct inode
*inode
, struct file
*file
)
1416 return seq_open(file
, &swaps_op
);
1419 static const struct file_operations proc_swaps_operations
= {
1422 .llseek
= seq_lseek
,
1423 .release
= seq_release
,
1426 static int __init
procswaps_init(void)
1428 proc_create("swaps", 0, NULL
, &proc_swaps_operations
);
1431 __initcall(procswaps_init
);
1432 #endif /* CONFIG_PROC_FS */
1434 #ifdef MAX_SWAPFILES_CHECK
1435 static int __init
max_swapfiles_check(void)
1437 MAX_SWAPFILES_CHECK();
1440 late_initcall(max_swapfiles_check
);
1444 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1446 * The swapon system call
1448 asmlinkage
long sys_swapon(const char __user
* specialfile
, int swap_flags
)
1450 struct swap_info_struct
* p
;
1452 struct block_device
*bdev
= NULL
;
1453 struct file
*swap_file
= NULL
;
1454 struct address_space
*mapping
;
1458 union swap_header
*swap_header
= NULL
;
1459 int swap_header_version
;
1460 unsigned int nr_good_pages
= 0;
1463 unsigned long maxpages
= 1;
1464 unsigned long swapfilepages
;
1465 unsigned short *swap_map
= NULL
;
1466 struct page
*page
= NULL
;
1467 struct inode
*inode
= NULL
;
1470 if (!capable(CAP_SYS_ADMIN
))
1472 spin_lock(&swap_lock
);
1474 for (type
= 0 ; type
< nr_swapfiles
; type
++,p
++)
1475 if (!(p
->flags
& SWP_USED
))
1478 if (type
>= MAX_SWAPFILES
) {
1479 spin_unlock(&swap_lock
);
1482 if (type
>= nr_swapfiles
)
1483 nr_swapfiles
= type
+1;
1484 memset(p
, 0, sizeof(*p
));
1485 INIT_LIST_HEAD(&p
->extent_list
);
1486 p
->flags
= SWP_USED
;
1488 spin_unlock(&swap_lock
);
1489 name
= getname(specialfile
);
1490 error
= PTR_ERR(name
);
1495 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1496 error
= PTR_ERR(swap_file
);
1497 if (IS_ERR(swap_file
)) {
1502 p
->swap_file
= swap_file
;
1503 mapping
= swap_file
->f_mapping
;
1504 inode
= mapping
->host
;
1507 for (i
= 0; i
< nr_swapfiles
; i
++) {
1508 struct swap_info_struct
*q
= &swap_info
[i
];
1510 if (i
== type
|| !q
->swap_file
)
1512 if (mapping
== q
->swap_file
->f_mapping
)
1517 if (S_ISBLK(inode
->i_mode
)) {
1518 bdev
= I_BDEV(inode
);
1519 error
= bd_claim(bdev
, sys_swapon
);
1525 p
->old_block_size
= block_size(bdev
);
1526 error
= set_blocksize(bdev
, PAGE_SIZE
);
1530 } else if (S_ISREG(inode
->i_mode
)) {
1531 p
->bdev
= inode
->i_sb
->s_bdev
;
1532 mutex_lock(&inode
->i_mutex
);
1534 if (IS_SWAPFILE(inode
)) {
1542 swapfilepages
= i_size_read(inode
) >> PAGE_SHIFT
;
1545 * Read the swap header.
1547 if (!mapping
->a_ops
->readpage
) {
1551 page
= read_mapping_page(mapping
, 0, swap_file
);
1553 error
= PTR_ERR(page
);
1557 swap_header
= page_address(page
);
1559 if (!memcmp("SWAP-SPACE",swap_header
->magic
.magic
,10))
1560 swap_header_version
= 1;
1561 else if (!memcmp("SWAPSPACE2",swap_header
->magic
.magic
,10))
1562 swap_header_version
= 2;
1564 printk(KERN_ERR
"Unable to find swap-space signature\n");
1569 switch (swap_header_version
) {
1571 printk(KERN_ERR
"version 0 swap is no longer supported. "
1572 "Use mkswap -v1 %s\n", name
);
1576 /* swap partition endianess hack... */
1577 if (swab32(swap_header
->info
.version
) == 1) {
1578 swab32s(&swap_header
->info
.version
);
1579 swab32s(&swap_header
->info
.last_page
);
1580 swab32s(&swap_header
->info
.nr_badpages
);
1581 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++)
1582 swab32s(&swap_header
->info
.badpages
[i
]);
1584 /* Check the swap header's sub-version and the size of
1585 the swap file and bad block lists */
1586 if (swap_header
->info
.version
!= 1) {
1588 "Unable to handle swap header version %d\n",
1589 swap_header
->info
.version
);
1595 p
->cluster_next
= 1;
1598 * Find out how many pages are allowed for a single swap
1599 * device. There are two limiting factors: 1) the number of
1600 * bits for the swap offset in the swp_entry_t type and
1601 * 2) the number of bits in the a swap pte as defined by
1602 * the different architectures. In order to find the
1603 * largest possible bit mask a swap entry with swap type 0
1604 * and swap offset ~0UL is created, encoded to a swap pte,
1605 * decoded to a swp_entry_t again and finally the swap
1606 * offset is extracted. This will mask all the bits from
1607 * the initial ~0UL mask that can't be encoded in either
1608 * the swp_entry_t or the architecture definition of a
1611 maxpages
= swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1612 if (maxpages
> swap_header
->info
.last_page
)
1613 maxpages
= swap_header
->info
.last_page
;
1614 p
->highest_bit
= maxpages
- 1;
1619 if (swapfilepages
&& maxpages
> swapfilepages
) {
1621 "Swap area shorter than signature indicates\n");
1624 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1626 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1629 /* OK, set up the swap map and apply the bad block list */
1630 swap_map
= vmalloc(maxpages
* sizeof(short));
1637 memset(swap_map
, 0, maxpages
* sizeof(short));
1638 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
1639 int page_nr
= swap_header
->info
.badpages
[i
];
1640 if (page_nr
<= 0 || page_nr
>= swap_header
->info
.last_page
)
1643 swap_map
[page_nr
] = SWAP_MAP_BAD
;
1645 nr_good_pages
= swap_header
->info
.last_page
-
1646 swap_header
->info
.nr_badpages
-
1647 1 /* header page */;
1652 if (nr_good_pages
) {
1653 swap_map
[0] = SWAP_MAP_BAD
;
1655 p
->pages
= nr_good_pages
;
1656 nr_extents
= setup_swap_extents(p
, &span
);
1657 if (nr_extents
< 0) {
1661 nr_good_pages
= p
->pages
;
1663 if (!nr_good_pages
) {
1664 printk(KERN_WARNING
"Empty swap-file\n");
1669 mutex_lock(&swapon_mutex
);
1670 spin_lock(&swap_lock
);
1671 if (swap_flags
& SWAP_FLAG_PREFER
)
1673 (swap_flags
& SWAP_FLAG_PRIO_MASK
) >> SWAP_FLAG_PRIO_SHIFT
;
1675 p
->prio
= --least_priority
;
1676 p
->swap_map
= swap_map
;
1677 p
->flags
|= SWP_WRITEOK
;
1678 nr_swap_pages
+= nr_good_pages
;
1679 total_swap_pages
+= nr_good_pages
;
1681 printk(KERN_INFO
"Adding %uk swap on %s. "
1682 "Priority:%d extents:%d across:%lluk\n",
1683 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
1684 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10));
1686 /* insert swap space into swap_list: */
1688 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1689 if (p
->prio
>= swap_info
[i
].prio
) {
1696 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1698 swap_info
[prev
].next
= p
- swap_info
;
1700 spin_unlock(&swap_lock
);
1701 mutex_unlock(&swapon_mutex
);
1706 set_blocksize(bdev
, p
->old_block_size
);
1709 destroy_swap_extents(p
);
1711 spin_lock(&swap_lock
);
1712 p
->swap_file
= NULL
;
1714 spin_unlock(&swap_lock
);
1717 filp_close(swap_file
, NULL
);
1719 if (page
&& !IS_ERR(page
)) {
1721 page_cache_release(page
);
1727 inode
->i_flags
|= S_SWAPFILE
;
1728 mutex_unlock(&inode
->i_mutex
);
1733 void si_swapinfo(struct sysinfo
*val
)
1736 unsigned long nr_to_be_unused
= 0;
1738 spin_lock(&swap_lock
);
1739 for (i
= 0; i
< nr_swapfiles
; i
++) {
1740 if (!(swap_info
[i
].flags
& SWP_USED
) ||
1741 (swap_info
[i
].flags
& SWP_WRITEOK
))
1743 nr_to_be_unused
+= swap_info
[i
].inuse_pages
;
1745 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
1746 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
1747 spin_unlock(&swap_lock
);
1751 * Verify that a swap entry is valid and increment its swap map count.
1753 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1754 * "permanent", but will be reclaimed by the next swapoff.
1756 int swap_duplicate(swp_entry_t entry
)
1758 struct swap_info_struct
* p
;
1759 unsigned long offset
, type
;
1762 if (is_migration_entry(entry
))
1765 type
= swp_type(entry
);
1766 if (type
>= nr_swapfiles
)
1768 p
= type
+ swap_info
;
1769 offset
= swp_offset(entry
);
1771 spin_lock(&swap_lock
);
1772 if (offset
< p
->max
&& p
->swap_map
[offset
]) {
1773 if (p
->swap_map
[offset
] < SWAP_MAP_MAX
- 1) {
1774 p
->swap_map
[offset
]++;
1776 } else if (p
->swap_map
[offset
] <= SWAP_MAP_MAX
) {
1777 if (swap_overflow
++ < 5)
1778 printk(KERN_WARNING
"swap_dup: swap entry overflow\n");
1779 p
->swap_map
[offset
] = SWAP_MAP_MAX
;
1783 spin_unlock(&swap_lock
);
1788 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
1792 struct swap_info_struct
*
1793 get_swap_info_struct(unsigned type
)
1795 return &swap_info
[type
];
1799 * swap_lock prevents swap_map being freed. Don't grab an extra
1800 * reference on the swaphandle, it doesn't matter if it becomes unused.
1802 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
1804 struct swap_info_struct
*si
;
1805 int our_page_cluster
= page_cluster
;
1806 pgoff_t target
, toff
;
1810 if (!our_page_cluster
) /* no readahead */
1813 si
= &swap_info
[swp_type(entry
)];
1814 target
= swp_offset(entry
);
1815 base
= (target
>> our_page_cluster
) << our_page_cluster
;
1816 end
= base
+ (1 << our_page_cluster
);
1817 if (!base
) /* first page is swap header */
1820 spin_lock(&swap_lock
);
1821 if (end
> si
->max
) /* don't go beyond end of map */
1824 /* Count contiguous allocated slots above our target */
1825 for (toff
= target
; ++toff
< end
; nr_pages
++) {
1826 /* Don't read in free or bad pages */
1827 if (!si
->swap_map
[toff
])
1829 if (si
->swap_map
[toff
] == SWAP_MAP_BAD
)
1832 /* Count contiguous allocated slots below our target */
1833 for (toff
= target
; --toff
>= base
; nr_pages
++) {
1834 /* Don't read in free or bad pages */
1835 if (!si
->swap_map
[toff
])
1837 if (si
->swap_map
[toff
] == SWAP_MAP_BAD
)
1840 spin_unlock(&swap_lock
);
1843 * Indicate starting offset, and return number of pages to get:
1844 * if only 1, say 0, since there's then no readahead to be done.
1847 return nr_pages
? ++nr_pages
: 0;