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>
31 #include <asm/pgtable.h>
32 #include <asm/tlbflush.h>
33 #include <linux/swapops.h>
35 DEFINE_SPINLOCK(swap_lock
);
36 unsigned int nr_swapfiles
;
37 long total_swap_pages
;
38 static int swap_overflow
;
40 static const char Bad_file
[] = "Bad swap file entry ";
41 static const char Unused_file
[] = "Unused swap file entry ";
42 static const char Bad_offset
[] = "Bad swap offset entry ";
43 static const char Unused_offset
[] = "Unused swap offset entry ";
45 struct swap_list_t swap_list
= {-1, -1};
47 static struct swap_info_struct swap_info
[MAX_SWAPFILES
];
49 static DEFINE_MUTEX(swapon_mutex
);
52 * We need this because the bdev->unplug_fn can sleep and we cannot
53 * hold swap_lock while calling the unplug_fn. And swap_lock
54 * cannot be turned into a mutex.
56 static DECLARE_RWSEM(swap_unplug_sem
);
58 void swap_unplug_io_fn(struct backing_dev_info
*unused_bdi
, struct page
*page
)
62 down_read(&swap_unplug_sem
);
63 entry
.val
= page_private(page
);
64 if (PageSwapCache(page
)) {
65 struct block_device
*bdev
= swap_info
[swp_type(entry
)].bdev
;
66 struct backing_dev_info
*bdi
;
69 * If the page is removed from swapcache from under us (with a
70 * racy try_to_unuse/swapoff) we need an additional reference
71 * count to avoid reading garbage from page_private(page) above.
72 * If the WARN_ON triggers during a swapoff it maybe the race
73 * condition and it's harmless. However if it triggers without
74 * swapoff it signals a problem.
76 WARN_ON(page_count(page
) <= 1);
78 bdi
= bdev
->bd_inode
->i_mapping
->backing_dev_info
;
79 blk_run_backing_dev(bdi
, page
);
81 up_read(&swap_unplug_sem
);
84 #define SWAPFILE_CLUSTER 256
85 #define LATENCY_LIMIT 256
87 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
)
89 unsigned long offset
, last_in_cluster
;
90 int latency_ration
= LATENCY_LIMIT
;
93 * We try to cluster swap pages by allocating them sequentially
94 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
95 * way, however, we resort to first-free allocation, starting
96 * a new cluster. This prevents us from scattering swap pages
97 * all over the entire swap partition, so that we reduce
98 * overall disk seek times between swap pages. -- sct
99 * But we do now try to find an empty cluster. -Andrea
102 si
->flags
+= SWP_SCANNING
;
103 if (unlikely(!si
->cluster_nr
)) {
104 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
105 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
)
107 spin_unlock(&swap_lock
);
109 offset
= si
->lowest_bit
;
110 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
112 /* Locate the first empty (unaligned) cluster */
113 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
114 if (si
->swap_map
[offset
])
115 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
116 else if (offset
== last_in_cluster
) {
117 spin_lock(&swap_lock
);
118 si
->cluster_next
= offset
-SWAPFILE_CLUSTER
+1;
121 if (unlikely(--latency_ration
< 0)) {
123 latency_ration
= LATENCY_LIMIT
;
126 spin_lock(&swap_lock
);
132 offset
= si
->cluster_next
;
133 if (offset
> si
->highest_bit
)
134 lowest
: offset
= si
->lowest_bit
;
135 checks
: if (!(si
->flags
& SWP_WRITEOK
))
137 if (!si
->highest_bit
)
139 if (!si
->swap_map
[offset
]) {
140 if (offset
== si
->lowest_bit
)
142 if (offset
== si
->highest_bit
)
145 if (si
->inuse_pages
== si
->pages
) {
146 si
->lowest_bit
= si
->max
;
149 si
->swap_map
[offset
] = 1;
150 si
->cluster_next
= offset
+ 1;
151 si
->flags
-= SWP_SCANNING
;
155 spin_unlock(&swap_lock
);
156 while (++offset
<= si
->highest_bit
) {
157 if (!si
->swap_map
[offset
]) {
158 spin_lock(&swap_lock
);
161 if (unlikely(--latency_ration
< 0)) {
163 latency_ration
= LATENCY_LIMIT
;
166 spin_lock(&swap_lock
);
170 si
->flags
-= SWP_SCANNING
;
174 swp_entry_t
get_swap_page(void)
176 struct swap_info_struct
*si
;
181 spin_lock(&swap_lock
);
182 if (nr_swap_pages
<= 0)
186 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
187 si
= swap_info
+ type
;
190 (!wrapped
&& si
->prio
!= swap_info
[next
].prio
)) {
191 next
= swap_list
.head
;
195 if (!si
->highest_bit
)
197 if (!(si
->flags
& SWP_WRITEOK
))
200 swap_list
.next
= next
;
201 offset
= scan_swap_map(si
);
203 spin_unlock(&swap_lock
);
204 return swp_entry(type
, offset
);
206 next
= swap_list
.next
;
211 spin_unlock(&swap_lock
);
212 return (swp_entry_t
) {0};
215 swp_entry_t
get_swap_page_of_type(int type
)
217 struct swap_info_struct
*si
;
220 spin_lock(&swap_lock
);
221 si
= swap_info
+ type
;
222 if (si
->flags
& SWP_WRITEOK
) {
224 offset
= scan_swap_map(si
);
226 spin_unlock(&swap_lock
);
227 return swp_entry(type
, offset
);
231 spin_unlock(&swap_lock
);
232 return (swp_entry_t
) {0};
235 static struct swap_info_struct
* swap_info_get(swp_entry_t entry
)
237 struct swap_info_struct
* p
;
238 unsigned long offset
, type
;
242 type
= swp_type(entry
);
243 if (type
>= nr_swapfiles
)
245 p
= & swap_info
[type
];
246 if (!(p
->flags
& SWP_USED
))
248 offset
= swp_offset(entry
);
249 if (offset
>= p
->max
)
251 if (!p
->swap_map
[offset
])
253 spin_lock(&swap_lock
);
257 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
260 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
263 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
266 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
271 static int swap_entry_free(struct swap_info_struct
*p
, unsigned long offset
)
273 int count
= p
->swap_map
[offset
];
275 if (count
< SWAP_MAP_MAX
) {
277 p
->swap_map
[offset
] = count
;
279 if (offset
< p
->lowest_bit
)
280 p
->lowest_bit
= offset
;
281 if (offset
> p
->highest_bit
)
282 p
->highest_bit
= offset
;
283 if (p
->prio
> swap_info
[swap_list
.next
].prio
)
284 swap_list
.next
= p
- swap_info
;
293 * Caller has made sure that the swapdevice corresponding to entry
294 * is still around or has not been recycled.
296 void swap_free(swp_entry_t entry
)
298 struct swap_info_struct
* p
;
300 p
= swap_info_get(entry
);
302 swap_entry_free(p
, swp_offset(entry
));
303 spin_unlock(&swap_lock
);
308 * How many references to page are currently swapped out?
310 static inline int page_swapcount(struct page
*page
)
313 struct swap_info_struct
*p
;
316 entry
.val
= page_private(page
);
317 p
= swap_info_get(entry
);
319 /* Subtract the 1 for the swap cache itself */
320 count
= p
->swap_map
[swp_offset(entry
)] - 1;
321 spin_unlock(&swap_lock
);
327 * We can use this swap cache entry directly
328 * if there are no other references to it.
330 int can_share_swap_page(struct page
*page
)
334 BUG_ON(!PageLocked(page
));
335 count
= page_mapcount(page
);
336 if (count
<= 1 && PageSwapCache(page
))
337 count
+= page_swapcount(page
);
342 * Work out if there are any other processes sharing this
343 * swap cache page. Free it if you can. Return success.
345 int remove_exclusive_swap_page(struct page
*page
)
348 struct swap_info_struct
* p
;
351 BUG_ON(PagePrivate(page
));
352 BUG_ON(!PageLocked(page
));
354 if (!PageSwapCache(page
))
356 if (PageWriteback(page
))
358 if (page_count(page
) != 2) /* 2: us + cache */
361 entry
.val
= page_private(page
);
362 p
= swap_info_get(entry
);
366 /* Is the only swap cache user the cache itself? */
368 if (p
->swap_map
[swp_offset(entry
)] == 1) {
369 /* Recheck the page count with the swapcache lock held.. */
370 write_lock_irq(&swapper_space
.tree_lock
);
371 if ((page_count(page
) == 2) && !PageWriteback(page
)) {
372 __delete_from_swap_cache(page
);
376 write_unlock_irq(&swapper_space
.tree_lock
);
378 spin_unlock(&swap_lock
);
382 page_cache_release(page
);
389 * Free the swap entry like above, but also try to
390 * free the page cache entry if it is the last user.
392 void free_swap_and_cache(swp_entry_t entry
)
394 struct swap_info_struct
* p
;
395 struct page
*page
= NULL
;
397 if (is_migration_entry(entry
))
400 p
= swap_info_get(entry
);
402 if (swap_entry_free(p
, swp_offset(entry
)) == 1) {
403 page
= find_get_page(&swapper_space
, entry
.val
);
404 if (page
&& unlikely(TestSetPageLocked(page
))) {
405 page_cache_release(page
);
409 spin_unlock(&swap_lock
);
414 BUG_ON(PagePrivate(page
));
415 one_user
= (page_count(page
) == 2);
416 /* Only cache user (+us), or swap space full? Free it! */
417 /* Also recheck PageSwapCache after page is locked (above) */
418 if (PageSwapCache(page
) && !PageWriteback(page
) &&
419 (one_user
|| vm_swap_full())) {
420 delete_from_swap_cache(page
);
424 page_cache_release(page
);
428 #ifdef CONFIG_HIBERNATION
430 * Find the swap type that corresponds to given device (if any).
432 * @offset - number of the PAGE_SIZE-sized block of the device, starting
433 * from 0, in which the swap header is expected to be located.
435 * This is needed for the suspend to disk (aka swsusp).
437 int swap_type_of(dev_t device
, sector_t offset
, struct block_device
**bdev_p
)
439 struct block_device
*bdev
= NULL
;
443 bdev
= bdget(device
);
445 spin_lock(&swap_lock
);
446 for (i
= 0; i
< nr_swapfiles
; i
++) {
447 struct swap_info_struct
*sis
= swap_info
+ i
;
449 if (!(sis
->flags
& SWP_WRITEOK
))
456 spin_unlock(&swap_lock
);
459 if (bdev
== sis
->bdev
) {
460 struct swap_extent
*se
;
462 se
= list_entry(sis
->extent_list
.next
,
463 struct swap_extent
, list
);
464 if (se
->start_block
== offset
) {
468 spin_unlock(&swap_lock
);
474 spin_unlock(&swap_lock
);
482 * Return either the total number of swap pages of given type, or the number
483 * of free pages of that type (depending on @free)
485 * This is needed for software suspend
487 unsigned int count_swap_pages(int type
, int free
)
491 if (type
< nr_swapfiles
) {
492 spin_lock(&swap_lock
);
493 if (swap_info
[type
].flags
& SWP_WRITEOK
) {
494 n
= swap_info
[type
].pages
;
496 n
-= swap_info
[type
].inuse_pages
;
498 spin_unlock(&swap_lock
);
505 * No need to decide whether this PTE shares the swap entry with others,
506 * just let do_wp_page work it out if a write is requested later - to
507 * force COW, vm_page_prot omits write permission from any private vma.
509 static void unuse_pte(struct vm_area_struct
*vma
, pte_t
*pte
,
510 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
512 inc_mm_counter(vma
->vm_mm
, anon_rss
);
514 set_pte_at(vma
->vm_mm
, addr
, pte
,
515 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
516 page_add_anon_rmap(page
, vma
, addr
);
519 * Move the page to the active list so it is not
520 * immediately swapped out again after swapon.
525 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
526 unsigned long addr
, unsigned long end
,
527 swp_entry_t entry
, struct page
*page
)
529 pte_t swp_pte
= swp_entry_to_pte(entry
);
534 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
537 * swapoff spends a _lot_ of time in this loop!
538 * Test inline before going to call unuse_pte.
540 if (unlikely(pte_same(*pte
, swp_pte
))) {
541 unuse_pte(vma
, pte
++, addr
, entry
, page
);
545 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
546 pte_unmap_unlock(pte
- 1, ptl
);
550 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
551 unsigned long addr
, unsigned long end
,
552 swp_entry_t entry
, struct page
*page
)
557 pmd
= pmd_offset(pud
, addr
);
559 next
= pmd_addr_end(addr
, end
);
560 if (pmd_none_or_clear_bad(pmd
))
562 if (unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
))
564 } while (pmd
++, addr
= next
, addr
!= end
);
568 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
569 unsigned long addr
, unsigned long end
,
570 swp_entry_t entry
, struct page
*page
)
575 pud
= pud_offset(pgd
, addr
);
577 next
= pud_addr_end(addr
, end
);
578 if (pud_none_or_clear_bad(pud
))
580 if (unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
))
582 } while (pud
++, addr
= next
, addr
!= end
);
586 static int unuse_vma(struct vm_area_struct
*vma
,
587 swp_entry_t entry
, struct page
*page
)
590 unsigned long addr
, end
, next
;
593 addr
= page_address_in_vma(page
, vma
);
597 end
= addr
+ PAGE_SIZE
;
599 addr
= vma
->vm_start
;
603 pgd
= pgd_offset(vma
->vm_mm
, addr
);
605 next
= pgd_addr_end(addr
, end
);
606 if (pgd_none_or_clear_bad(pgd
))
608 if (unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
))
610 } while (pgd
++, addr
= next
, addr
!= end
);
614 static int unuse_mm(struct mm_struct
*mm
,
615 swp_entry_t entry
, struct page
*page
)
617 struct vm_area_struct
*vma
;
619 if (!down_read_trylock(&mm
->mmap_sem
)) {
621 * Activate page so shrink_cache is unlikely to unmap its
622 * ptes while lock is dropped, so swapoff can make progress.
626 down_read(&mm
->mmap_sem
);
629 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
630 if (vma
->anon_vma
&& unuse_vma(vma
, entry
, page
))
633 up_read(&mm
->mmap_sem
);
635 * Currently unuse_mm cannot fail, but leave error handling
636 * at call sites for now, since we change it from time to time.
642 * Scan swap_map from current position to next entry still in use.
643 * Recycle to start on reaching the end, returning 0 when empty.
645 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
648 unsigned int max
= si
->max
;
649 unsigned int i
= prev
;
653 * No need for swap_lock here: we're just looking
654 * for whether an entry is in use, not modifying it; false
655 * hits are okay, and sys_swapoff() has already prevented new
656 * allocations from this area (while holding swap_lock).
665 * No entries in use at top of swap_map,
666 * loop back to start and recheck there.
672 count
= si
->swap_map
[i
];
673 if (count
&& count
!= SWAP_MAP_BAD
)
680 * We completely avoid races by reading each swap page in advance,
681 * and then search for the process using it. All the necessary
682 * page table adjustments can then be made atomically.
684 static int try_to_unuse(unsigned int type
)
686 struct swap_info_struct
* si
= &swap_info
[type
];
687 struct mm_struct
*start_mm
;
688 unsigned short *swap_map
;
689 unsigned short swcount
;
694 int reset_overflow
= 0;
698 * When searching mms for an entry, a good strategy is to
699 * start at the first mm we freed the previous entry from
700 * (though actually we don't notice whether we or coincidence
701 * freed the entry). Initialize this start_mm with a hold.
703 * A simpler strategy would be to start at the last mm we
704 * freed the previous entry from; but that would take less
705 * advantage of mmlist ordering, which clusters forked mms
706 * together, child after parent. If we race with dup_mmap(), we
707 * prefer to resolve parent before child, lest we miss entries
708 * duplicated after we scanned child: using last mm would invert
709 * that. Though it's only a serious concern when an overflowed
710 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
713 atomic_inc(&init_mm
.mm_users
);
716 * Keep on scanning until all entries have gone. Usually,
717 * one pass through swap_map is enough, but not necessarily:
718 * there are races when an instance of an entry might be missed.
720 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
721 if (signal_pending(current
)) {
727 * Get a page for the entry, using the existing swap
728 * cache page if there is one. Otherwise, get a clean
729 * page and read the swap into it.
731 swap_map
= &si
->swap_map
[i
];
732 entry
= swp_entry(type
, i
);
733 page
= read_swap_cache_async(entry
,
734 GFP_HIGHUSER_MOVABLE
, NULL
, 0);
737 * Either swap_duplicate() failed because entry
738 * has been freed independently, and will not be
739 * reused since sys_swapoff() already disabled
740 * allocation from here, or alloc_page() failed.
749 * Don't hold on to start_mm if it looks like exiting.
751 if (atomic_read(&start_mm
->mm_users
) == 1) {
754 atomic_inc(&init_mm
.mm_users
);
758 * Wait for and lock page. When do_swap_page races with
759 * try_to_unuse, do_swap_page can handle the fault much
760 * faster than try_to_unuse can locate the entry. This
761 * apparently redundant "wait_on_page_locked" lets try_to_unuse
762 * defer to do_swap_page in such a case - in some tests,
763 * do_swap_page and try_to_unuse repeatedly compete.
765 wait_on_page_locked(page
);
766 wait_on_page_writeback(page
);
768 wait_on_page_writeback(page
);
771 * Remove all references to entry.
772 * Whenever we reach init_mm, there's no address space
773 * to search, but use it as a reminder to search shmem.
778 if (start_mm
== &init_mm
)
779 shmem
= shmem_unuse(entry
, page
);
781 retval
= unuse_mm(start_mm
, entry
, page
);
784 int set_start_mm
= (*swap_map
>= swcount
);
785 struct list_head
*p
= &start_mm
->mmlist
;
786 struct mm_struct
*new_start_mm
= start_mm
;
787 struct mm_struct
*prev_mm
= start_mm
;
788 struct mm_struct
*mm
;
790 atomic_inc(&new_start_mm
->mm_users
);
791 atomic_inc(&prev_mm
->mm_users
);
792 spin_lock(&mmlist_lock
);
793 while (*swap_map
> 1 && !retval
&&
794 (p
= p
->next
) != &start_mm
->mmlist
) {
795 mm
= list_entry(p
, struct mm_struct
, mmlist
);
796 if (!atomic_inc_not_zero(&mm
->mm_users
))
798 spin_unlock(&mmlist_lock
);
807 else if (mm
== &init_mm
) {
809 shmem
= shmem_unuse(entry
, page
);
811 retval
= unuse_mm(mm
, entry
, page
);
812 if (set_start_mm
&& *swap_map
< swcount
) {
814 atomic_inc(&mm
->mm_users
);
818 spin_lock(&mmlist_lock
);
820 spin_unlock(&mmlist_lock
);
823 start_mm
= new_start_mm
;
827 page_cache_release(page
);
832 * How could swap count reach 0x7fff when the maximum
833 * pid is 0x7fff, and there's no way to repeat a swap
834 * page within an mm (except in shmem, where it's the
835 * shared object which takes the reference count)?
836 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
838 * If that's wrong, then we should worry more about
839 * exit_mmap() and do_munmap() cases described above:
840 * we might be resetting SWAP_MAP_MAX too early here.
841 * We know "Undead"s can happen, they're okay, so don't
842 * report them; but do report if we reset SWAP_MAP_MAX.
844 if (*swap_map
== SWAP_MAP_MAX
) {
845 spin_lock(&swap_lock
);
847 spin_unlock(&swap_lock
);
852 * If a reference remains (rare), we would like to leave
853 * the page in the swap cache; but try_to_unmap could
854 * then re-duplicate the entry once we drop page lock,
855 * so we might loop indefinitely; also, that page could
856 * not be swapped out to other storage meanwhile. So:
857 * delete from cache even if there's another reference,
858 * after ensuring that the data has been saved to disk -
859 * since if the reference remains (rarer), it will be
860 * read from disk into another page. Splitting into two
861 * pages would be incorrect if swap supported "shared
862 * private" pages, but they are handled by tmpfs files.
864 * Note shmem_unuse already deleted a swappage from
865 * the swap cache, unless the move to filepage failed:
866 * in which case it left swappage in cache, lowered its
867 * swap count to pass quickly through the loops above,
868 * and now we must reincrement count to try again later.
870 if ((*swap_map
> 1) && PageDirty(page
) && PageSwapCache(page
)) {
871 struct writeback_control wbc
= {
872 .sync_mode
= WB_SYNC_NONE
,
875 swap_writepage(page
, &wbc
);
877 wait_on_page_writeback(page
);
879 if (PageSwapCache(page
)) {
881 swap_duplicate(entry
);
883 delete_from_swap_cache(page
);
887 * So we could skip searching mms once swap count went
888 * to 1, we did not mark any present ptes as dirty: must
889 * mark page dirty so shrink_page_list will preserve it.
893 page_cache_release(page
);
896 * Make sure that we aren't completely killing
897 * interactive performance.
903 if (reset_overflow
) {
904 printk(KERN_WARNING
"swapoff: cleared swap entry overflow\n");
911 * After a successful try_to_unuse, if no swap is now in use, we know
912 * we can empty the mmlist. swap_lock must be held on entry and exit.
913 * Note that mmlist_lock nests inside swap_lock, and an mm must be
914 * added to the mmlist just after page_duplicate - before would be racy.
916 static void drain_mmlist(void)
918 struct list_head
*p
, *next
;
921 for (i
= 0; i
< nr_swapfiles
; i
++)
922 if (swap_info
[i
].inuse_pages
)
924 spin_lock(&mmlist_lock
);
925 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
927 spin_unlock(&mmlist_lock
);
931 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
932 * corresponds to page offset `offset'.
934 sector_t
map_swap_page(struct swap_info_struct
*sis
, pgoff_t offset
)
936 struct swap_extent
*se
= sis
->curr_swap_extent
;
937 struct swap_extent
*start_se
= se
;
940 struct list_head
*lh
;
942 if (se
->start_page
<= offset
&&
943 offset
< (se
->start_page
+ se
->nr_pages
)) {
944 return se
->start_block
+ (offset
- se
->start_page
);
947 if (lh
== &sis
->extent_list
)
949 se
= list_entry(lh
, struct swap_extent
, list
);
950 sis
->curr_swap_extent
= se
;
951 BUG_ON(se
== start_se
); /* It *must* be present */
955 #ifdef CONFIG_HIBERNATION
957 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
958 * corresponding to given index in swap_info (swap type).
960 sector_t
swapdev_block(int swap_type
, pgoff_t offset
)
962 struct swap_info_struct
*sis
;
964 if (swap_type
>= nr_swapfiles
)
967 sis
= swap_info
+ swap_type
;
968 return (sis
->flags
& SWP_WRITEOK
) ? map_swap_page(sis
, offset
) : 0;
970 #endif /* CONFIG_HIBERNATION */
973 * Free all of a swapdev's extent information
975 static void destroy_swap_extents(struct swap_info_struct
*sis
)
977 while (!list_empty(&sis
->extent_list
)) {
978 struct swap_extent
*se
;
980 se
= list_entry(sis
->extent_list
.next
,
981 struct swap_extent
, list
);
988 * Add a block range (and the corresponding page range) into this swapdev's
989 * extent list. The extent list is kept sorted in page order.
991 * This function rather assumes that it is called in ascending page order.
994 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
995 unsigned long nr_pages
, sector_t start_block
)
997 struct swap_extent
*se
;
998 struct swap_extent
*new_se
;
999 struct list_head
*lh
;
1001 lh
= sis
->extent_list
.prev
; /* The highest page extent */
1002 if (lh
!= &sis
->extent_list
) {
1003 se
= list_entry(lh
, struct swap_extent
, list
);
1004 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
1005 if (se
->start_block
+ se
->nr_pages
== start_block
) {
1007 se
->nr_pages
+= nr_pages
;
1013 * No merge. Insert a new extent, preserving ordering.
1015 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
1018 new_se
->start_page
= start_page
;
1019 new_se
->nr_pages
= nr_pages
;
1020 new_se
->start_block
= start_block
;
1022 list_add_tail(&new_se
->list
, &sis
->extent_list
);
1027 * A `swap extent' is a simple thing which maps a contiguous range of pages
1028 * onto a contiguous range of disk blocks. An ordered list of swap extents
1029 * is built at swapon time and is then used at swap_writepage/swap_readpage
1030 * time for locating where on disk a page belongs.
1032 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1033 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1034 * swap files identically.
1036 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1037 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1038 * swapfiles are handled *identically* after swapon time.
1040 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1041 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1042 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1043 * requirements, they are simply tossed out - we will never use those blocks
1046 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1047 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1048 * which will scribble on the fs.
1050 * The amount of disk space which a single swap extent represents varies.
1051 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1052 * extents in the list. To avoid much list walking, we cache the previous
1053 * search location in `curr_swap_extent', and start new searches from there.
1054 * This is extremely effective. The average number of iterations in
1055 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1057 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
1059 struct inode
*inode
;
1060 unsigned blocks_per_page
;
1061 unsigned long page_no
;
1063 sector_t probe_block
;
1064 sector_t last_block
;
1065 sector_t lowest_block
= -1;
1066 sector_t highest_block
= 0;
1070 inode
= sis
->swap_file
->f_mapping
->host
;
1071 if (S_ISBLK(inode
->i_mode
)) {
1072 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
1077 blkbits
= inode
->i_blkbits
;
1078 blocks_per_page
= PAGE_SIZE
>> blkbits
;
1081 * Map all the blocks into the extent list. This code doesn't try
1086 last_block
= i_size_read(inode
) >> blkbits
;
1087 while ((probe_block
+ blocks_per_page
) <= last_block
&&
1088 page_no
< sis
->max
) {
1089 unsigned block_in_page
;
1090 sector_t first_block
;
1092 first_block
= bmap(inode
, probe_block
);
1093 if (first_block
== 0)
1097 * It must be PAGE_SIZE aligned on-disk
1099 if (first_block
& (blocks_per_page
- 1)) {
1104 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1108 block
= bmap(inode
, probe_block
+ block_in_page
);
1111 if (block
!= first_block
+ block_in_page
) {
1118 first_block
>>= (PAGE_SHIFT
- blkbits
);
1119 if (page_no
) { /* exclude the header page */
1120 if (first_block
< lowest_block
)
1121 lowest_block
= first_block
;
1122 if (first_block
> highest_block
)
1123 highest_block
= first_block
;
1127 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1129 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1134 probe_block
+= blocks_per_page
;
1139 *span
= 1 + highest_block
- lowest_block
;
1141 page_no
= 1; /* force Empty message */
1143 sis
->pages
= page_no
- 1;
1144 sis
->highest_bit
= page_no
- 1;
1146 sis
->curr_swap_extent
= list_entry(sis
->extent_list
.prev
,
1147 struct swap_extent
, list
);
1150 printk(KERN_ERR
"swapon: swapfile has holes\n");
1156 #if 0 /* We don't need this yet */
1157 #include <linux/backing-dev.h>
1158 int page_queue_congested(struct page
*page
)
1160 struct backing_dev_info
*bdi
;
1162 BUG_ON(!PageLocked(page
)); /* It pins the swap_info_struct */
1164 if (PageSwapCache(page
)) {
1165 swp_entry_t entry
= { .val
= page_private(page
) };
1166 struct swap_info_struct
*sis
;
1168 sis
= get_swap_info_struct(swp_type(entry
));
1169 bdi
= sis
->bdev
->bd_inode
->i_mapping
->backing_dev_info
;
1171 bdi
= page
->mapping
->backing_dev_info
;
1172 return bdi_write_congested(bdi
);
1176 asmlinkage
long sys_swapoff(const char __user
* specialfile
)
1178 struct swap_info_struct
* p
= NULL
;
1179 unsigned short *swap_map
;
1180 struct file
*swap_file
, *victim
;
1181 struct address_space
*mapping
;
1182 struct inode
*inode
;
1187 if (!capable(CAP_SYS_ADMIN
))
1190 pathname
= getname(specialfile
);
1191 err
= PTR_ERR(pathname
);
1192 if (IS_ERR(pathname
))
1195 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1197 err
= PTR_ERR(victim
);
1201 mapping
= victim
->f_mapping
;
1203 spin_lock(&swap_lock
);
1204 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
].next
) {
1205 p
= swap_info
+ type
;
1206 if ((p
->flags
& SWP_ACTIVE
) == SWP_ACTIVE
) {
1207 if (p
->swap_file
->f_mapping
== mapping
)
1214 spin_unlock(&swap_lock
);
1217 if (!security_vm_enough_memory(p
->pages
))
1218 vm_unacct_memory(p
->pages
);
1221 spin_unlock(&swap_lock
);
1225 swap_list
.head
= p
->next
;
1227 swap_info
[prev
].next
= p
->next
;
1229 if (type
== swap_list
.next
) {
1230 /* just pick something that's safe... */
1231 swap_list
.next
= swap_list
.head
;
1233 nr_swap_pages
-= p
->pages
;
1234 total_swap_pages
-= p
->pages
;
1235 p
->flags
&= ~SWP_WRITEOK
;
1236 spin_unlock(&swap_lock
);
1238 current
->flags
|= PF_SWAPOFF
;
1239 err
= try_to_unuse(type
);
1240 current
->flags
&= ~PF_SWAPOFF
;
1243 /* re-insert swap space back into swap_list */
1244 spin_lock(&swap_lock
);
1245 for (prev
= -1, i
= swap_list
.head
; i
>= 0; prev
= i
, i
= swap_info
[i
].next
)
1246 if (p
->prio
>= swap_info
[i
].prio
)
1250 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1252 swap_info
[prev
].next
= p
- swap_info
;
1253 nr_swap_pages
+= p
->pages
;
1254 total_swap_pages
+= p
->pages
;
1255 p
->flags
|= SWP_WRITEOK
;
1256 spin_unlock(&swap_lock
);
1260 /* wait for any unplug function to finish */
1261 down_write(&swap_unplug_sem
);
1262 up_write(&swap_unplug_sem
);
1264 destroy_swap_extents(p
);
1265 mutex_lock(&swapon_mutex
);
1266 spin_lock(&swap_lock
);
1269 /* wait for anyone still in scan_swap_map */
1270 p
->highest_bit
= 0; /* cuts scans short */
1271 while (p
->flags
>= SWP_SCANNING
) {
1272 spin_unlock(&swap_lock
);
1273 schedule_timeout_uninterruptible(1);
1274 spin_lock(&swap_lock
);
1277 swap_file
= p
->swap_file
;
1278 p
->swap_file
= NULL
;
1280 swap_map
= p
->swap_map
;
1283 spin_unlock(&swap_lock
);
1284 mutex_unlock(&swapon_mutex
);
1286 inode
= mapping
->host
;
1287 if (S_ISBLK(inode
->i_mode
)) {
1288 struct block_device
*bdev
= I_BDEV(inode
);
1289 set_blocksize(bdev
, p
->old_block_size
);
1292 mutex_lock(&inode
->i_mutex
);
1293 inode
->i_flags
&= ~S_SWAPFILE
;
1294 mutex_unlock(&inode
->i_mutex
);
1296 filp_close(swap_file
, NULL
);
1300 filp_close(victim
, NULL
);
1305 #ifdef CONFIG_PROC_FS
1307 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1309 struct swap_info_struct
*ptr
= swap_info
;
1313 mutex_lock(&swapon_mutex
);
1316 return SEQ_START_TOKEN
;
1318 for (i
= 0; i
< nr_swapfiles
; i
++, ptr
++) {
1319 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1328 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1330 struct swap_info_struct
*ptr
;
1331 struct swap_info_struct
*endptr
= swap_info
+ nr_swapfiles
;
1333 if (v
== SEQ_START_TOKEN
)
1340 for (; ptr
< endptr
; ptr
++) {
1341 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1350 static void swap_stop(struct seq_file
*swap
, void *v
)
1352 mutex_unlock(&swapon_mutex
);
1355 static int swap_show(struct seq_file
*swap
, void *v
)
1357 struct swap_info_struct
*ptr
= v
;
1361 if (ptr
== SEQ_START_TOKEN
) {
1362 seq_puts(swap
,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1366 file
= ptr
->swap_file
;
1367 len
= seq_path(swap
, file
->f_path
.mnt
, file
->f_path
.dentry
, " \t\n\\");
1368 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1369 len
< 40 ? 40 - len
: 1, " ",
1370 S_ISBLK(file
->f_path
.dentry
->d_inode
->i_mode
) ?
1371 "partition" : "file\t",
1372 ptr
->pages
<< (PAGE_SHIFT
- 10),
1373 ptr
->inuse_pages
<< (PAGE_SHIFT
- 10),
1378 static const struct seq_operations swaps_op
= {
1379 .start
= swap_start
,
1385 static int swaps_open(struct inode
*inode
, struct file
*file
)
1387 return seq_open(file
, &swaps_op
);
1390 static const struct file_operations proc_swaps_operations
= {
1393 .llseek
= seq_lseek
,
1394 .release
= seq_release
,
1397 static int __init
procswaps_init(void)
1399 struct proc_dir_entry
*entry
;
1401 entry
= create_proc_entry("swaps", 0, NULL
);
1403 entry
->proc_fops
= &proc_swaps_operations
;
1406 __initcall(procswaps_init
);
1407 #endif /* CONFIG_PROC_FS */
1410 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1412 * The swapon system call
1414 asmlinkage
long sys_swapon(const char __user
* specialfile
, int swap_flags
)
1416 struct swap_info_struct
* p
;
1418 struct block_device
*bdev
= NULL
;
1419 struct file
*swap_file
= NULL
;
1420 struct address_space
*mapping
;
1424 static int least_priority
;
1425 union swap_header
*swap_header
= NULL
;
1426 int swap_header_version
;
1427 unsigned int nr_good_pages
= 0;
1430 unsigned long maxpages
= 1;
1432 unsigned short *swap_map
;
1433 struct page
*page
= NULL
;
1434 struct inode
*inode
= NULL
;
1437 if (!capable(CAP_SYS_ADMIN
))
1439 spin_lock(&swap_lock
);
1441 for (type
= 0 ; type
< nr_swapfiles
; type
++,p
++)
1442 if (!(p
->flags
& SWP_USED
))
1445 if (type
>= MAX_SWAPFILES
) {
1446 spin_unlock(&swap_lock
);
1449 if (type
>= nr_swapfiles
)
1450 nr_swapfiles
= type
+1;
1451 INIT_LIST_HEAD(&p
->extent_list
);
1452 p
->flags
= SWP_USED
;
1453 p
->swap_file
= NULL
;
1454 p
->old_block_size
= 0;
1461 if (swap_flags
& SWAP_FLAG_PREFER
) {
1463 (swap_flags
& SWAP_FLAG_PRIO_MASK
)>>SWAP_FLAG_PRIO_SHIFT
;
1465 p
->prio
= --least_priority
;
1467 spin_unlock(&swap_lock
);
1468 name
= getname(specialfile
);
1469 error
= PTR_ERR(name
);
1474 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1475 error
= PTR_ERR(swap_file
);
1476 if (IS_ERR(swap_file
)) {
1481 p
->swap_file
= swap_file
;
1482 mapping
= swap_file
->f_mapping
;
1483 inode
= mapping
->host
;
1486 for (i
= 0; i
< nr_swapfiles
; i
++) {
1487 struct swap_info_struct
*q
= &swap_info
[i
];
1489 if (i
== type
|| !q
->swap_file
)
1491 if (mapping
== q
->swap_file
->f_mapping
)
1496 if (S_ISBLK(inode
->i_mode
)) {
1497 bdev
= I_BDEV(inode
);
1498 error
= bd_claim(bdev
, sys_swapon
);
1504 p
->old_block_size
= block_size(bdev
);
1505 error
= set_blocksize(bdev
, PAGE_SIZE
);
1509 } else if (S_ISREG(inode
->i_mode
)) {
1510 p
->bdev
= inode
->i_sb
->s_bdev
;
1511 mutex_lock(&inode
->i_mutex
);
1513 if (IS_SWAPFILE(inode
)) {
1521 swapfilesize
= i_size_read(inode
) >> PAGE_SHIFT
;
1524 * Read the swap header.
1526 if (!mapping
->a_ops
->readpage
) {
1530 page
= read_mapping_page(mapping
, 0, swap_file
);
1532 error
= PTR_ERR(page
);
1536 swap_header
= page_address(page
);
1538 if (!memcmp("SWAP-SPACE",swap_header
->magic
.magic
,10))
1539 swap_header_version
= 1;
1540 else if (!memcmp("SWAPSPACE2",swap_header
->magic
.magic
,10))
1541 swap_header_version
= 2;
1543 printk(KERN_ERR
"Unable to find swap-space signature\n");
1548 switch (swap_header_version
) {
1550 printk(KERN_ERR
"version 0 swap is no longer supported. "
1551 "Use mkswap -v1 %s\n", name
);
1555 /* Check the swap header's sub-version and the size of
1556 the swap file and bad block lists */
1557 if (swap_header
->info
.version
!= 1) {
1559 "Unable to handle swap header version %d\n",
1560 swap_header
->info
.version
);
1566 p
->cluster_next
= 1;
1569 * Find out how many pages are allowed for a single swap
1570 * device. There are two limiting factors: 1) the number of
1571 * bits for the swap offset in the swp_entry_t type and
1572 * 2) the number of bits in the a swap pte as defined by
1573 * the different architectures. In order to find the
1574 * largest possible bit mask a swap entry with swap type 0
1575 * and swap offset ~0UL is created, encoded to a swap pte,
1576 * decoded to a swp_entry_t again and finally the swap
1577 * offset is extracted. This will mask all the bits from
1578 * the initial ~0UL mask that can't be encoded in either
1579 * the swp_entry_t or the architecture definition of a
1582 maxpages
= swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1583 if (maxpages
> swap_header
->info
.last_page
)
1584 maxpages
= swap_header
->info
.last_page
;
1585 p
->highest_bit
= maxpages
- 1;
1590 if (swapfilesize
&& maxpages
> swapfilesize
) {
1592 "Swap area shorter than signature indicates\n");
1595 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1597 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1600 /* OK, set up the swap map and apply the bad block list */
1601 if (!(p
->swap_map
= vmalloc(maxpages
* sizeof(short)))) {
1607 memset(p
->swap_map
, 0, maxpages
* sizeof(short));
1608 for (i
= 0; i
< swap_header
->info
.nr_badpages
; i
++) {
1609 int page_nr
= swap_header
->info
.badpages
[i
];
1610 if (page_nr
<= 0 || page_nr
>= swap_header
->info
.last_page
)
1613 p
->swap_map
[page_nr
] = SWAP_MAP_BAD
;
1615 nr_good_pages
= swap_header
->info
.last_page
-
1616 swap_header
->info
.nr_badpages
-
1617 1 /* header page */;
1622 if (nr_good_pages
) {
1623 p
->swap_map
[0] = SWAP_MAP_BAD
;
1625 p
->pages
= nr_good_pages
;
1626 nr_extents
= setup_swap_extents(p
, &span
);
1627 if (nr_extents
< 0) {
1631 nr_good_pages
= p
->pages
;
1633 if (!nr_good_pages
) {
1634 printk(KERN_WARNING
"Empty swap-file\n");
1639 mutex_lock(&swapon_mutex
);
1640 spin_lock(&swap_lock
);
1641 p
->flags
= SWP_ACTIVE
;
1642 nr_swap_pages
+= nr_good_pages
;
1643 total_swap_pages
+= nr_good_pages
;
1645 printk(KERN_INFO
"Adding %uk swap on %s. "
1646 "Priority:%d extents:%d across:%lluk\n",
1647 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
1648 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10));
1650 /* insert swap space into swap_list: */
1652 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1653 if (p
->prio
>= swap_info
[i
].prio
) {
1660 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1662 swap_info
[prev
].next
= p
- swap_info
;
1664 spin_unlock(&swap_lock
);
1665 mutex_unlock(&swapon_mutex
);
1670 set_blocksize(bdev
, p
->old_block_size
);
1673 destroy_swap_extents(p
);
1675 spin_lock(&swap_lock
);
1676 swap_map
= p
->swap_map
;
1677 p
->swap_file
= NULL
;
1680 if (!(swap_flags
& SWAP_FLAG_PREFER
))
1682 spin_unlock(&swap_lock
);
1685 filp_close(swap_file
, NULL
);
1687 if (page
&& !IS_ERR(page
)) {
1689 page_cache_release(page
);
1695 inode
->i_flags
|= S_SWAPFILE
;
1696 mutex_unlock(&inode
->i_mutex
);
1701 void si_swapinfo(struct sysinfo
*val
)
1704 unsigned long nr_to_be_unused
= 0;
1706 spin_lock(&swap_lock
);
1707 for (i
= 0; i
< nr_swapfiles
; i
++) {
1708 if (!(swap_info
[i
].flags
& SWP_USED
) ||
1709 (swap_info
[i
].flags
& SWP_WRITEOK
))
1711 nr_to_be_unused
+= swap_info
[i
].inuse_pages
;
1713 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
1714 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
1715 spin_unlock(&swap_lock
);
1719 * Verify that a swap entry is valid and increment its swap map count.
1721 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1722 * "permanent", but will be reclaimed by the next swapoff.
1724 int swap_duplicate(swp_entry_t entry
)
1726 struct swap_info_struct
* p
;
1727 unsigned long offset
, type
;
1730 if (is_migration_entry(entry
))
1733 type
= swp_type(entry
);
1734 if (type
>= nr_swapfiles
)
1736 p
= type
+ swap_info
;
1737 offset
= swp_offset(entry
);
1739 spin_lock(&swap_lock
);
1740 if (offset
< p
->max
&& p
->swap_map
[offset
]) {
1741 if (p
->swap_map
[offset
] < SWAP_MAP_MAX
- 1) {
1742 p
->swap_map
[offset
]++;
1744 } else if (p
->swap_map
[offset
] <= SWAP_MAP_MAX
) {
1745 if (swap_overflow
++ < 5)
1746 printk(KERN_WARNING
"swap_dup: swap entry overflow\n");
1747 p
->swap_map
[offset
] = SWAP_MAP_MAX
;
1751 spin_unlock(&swap_lock
);
1756 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
1760 struct swap_info_struct
*
1761 get_swap_info_struct(unsigned type
)
1763 return &swap_info
[type
];
1767 * swap_lock prevents swap_map being freed. Don't grab an extra
1768 * reference on the swaphandle, it doesn't matter if it becomes unused.
1770 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
1772 struct swap_info_struct
*si
;
1773 int our_page_cluster
= page_cluster
;
1774 pgoff_t target
, toff
;
1778 if (!our_page_cluster
) /* no readahead */
1781 si
= &swap_info
[swp_type(entry
)];
1782 target
= swp_offset(entry
);
1783 base
= (target
>> our_page_cluster
) << our_page_cluster
;
1784 end
= base
+ (1 << our_page_cluster
);
1785 if (!base
) /* first page is swap header */
1788 spin_lock(&swap_lock
);
1789 if (end
> si
->max
) /* don't go beyond end of map */
1792 /* Count contiguous allocated slots above our target */
1793 for (toff
= target
; ++toff
< end
; nr_pages
++) {
1794 /* Don't read in free or bad pages */
1795 if (!si
->swap_map
[toff
])
1797 if (si
->swap_map
[toff
] == SWAP_MAP_BAD
)
1800 /* Count contiguous allocated slots below our target */
1801 for (toff
= target
; --toff
>= base
; nr_pages
++) {
1802 /* Don't read in free or bad pages */
1803 if (!si
->swap_map
[toff
])
1805 if (si
->swap_map
[toff
] == SWAP_MAP_BAD
)
1808 spin_unlock(&swap_lock
);
1811 * Indicate starting offset, and return number of pages to get:
1812 * if only 1, say 0, since there's then no readahead to be done.
1815 return nr_pages
? ++nr_pages
: 0;