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/syscalls.h>
30 #include <asm/pgtable.h>
31 #include <asm/tlbflush.h>
32 #include <linux/swapops.h>
34 DEFINE_SPINLOCK(swaplock
);
35 unsigned int nr_swapfiles
;
36 long total_swap_pages
;
37 static int swap_overflow
;
39 EXPORT_SYMBOL(total_swap_pages
);
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 struct swap_info_struct swap_info
[MAX_SWAPFILES
];
50 static DECLARE_MUTEX(swapon_sem
);
53 * We need this because the bdev->unplug_fn can sleep and we cannot
54 * hold swap_list_lock while calling the unplug_fn. And swap_list_lock
55 * cannot be turned into a semaphore.
57 static DECLARE_RWSEM(swap_unplug_sem
);
59 #define SWAPFILE_CLUSTER 256
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;
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 above. If
75 * 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 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
)
89 unsigned long offset
, last_in_cluster
;
92 * We try to cluster swap pages by allocating them sequentially
93 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
94 * way, however, we resort to first-free allocation, starting
95 * a new cluster. This prevents us from scattering swap pages
96 * all over the entire swap partition, so that we reduce
97 * overall disk seek times between swap pages. -- sct
98 * But we do now try to find an empty cluster. -Andrea
101 if (unlikely(!si
->cluster_nr
)) {
102 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
103 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
)
106 offset
= si
->lowest_bit
;
107 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
109 /* Locate the first empty (unaligned) cluster */
110 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
111 if (si
->swap_map
[offset
])
112 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
113 else if (offset
== last_in_cluster
) {
114 si
->cluster_next
= offset
-SWAPFILE_CLUSTER
-1;
123 offset
= si
->cluster_next
;
124 if (offset
> si
->highest_bit
)
125 lowest
: offset
= si
->lowest_bit
;
126 if (!si
->highest_bit
)
128 if (!si
->swap_map
[offset
]) {
129 got_page
: if (offset
== si
->lowest_bit
)
131 if (offset
== si
->highest_bit
)
134 if (si
->inuse_pages
== si
->pages
) {
135 si
->lowest_bit
= si
->max
;
138 si
->swap_map
[offset
] = 1;
139 si
->cluster_next
= offset
+ 1;
143 while (++offset
<= si
->highest_bit
) {
144 if (!si
->swap_map
[offset
])
153 swp_entry_t
get_swap_page(void)
155 struct swap_info_struct
*si
;
161 if (nr_swap_pages
<= 0)
165 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
166 si
= swap_info
+ type
;
169 (!wrapped
&& si
->prio
!= swap_info
[next
].prio
)) {
170 next
= swap_list
.head
;
174 if (!si
->highest_bit
)
176 if (!(si
->flags
& SWP_WRITEOK
))
179 swap_list
.next
= next
;
180 swap_device_lock(si
);
182 offset
= scan_swap_map(si
);
183 swap_device_unlock(si
);
185 return swp_entry(type
, offset
);
187 next
= swap_list
.next
;
193 return (swp_entry_t
) {0};
196 static struct swap_info_struct
* swap_info_get(swp_entry_t entry
)
198 struct swap_info_struct
* p
;
199 unsigned long offset
, type
;
203 type
= swp_type(entry
);
204 if (type
>= nr_swapfiles
)
206 p
= & swap_info
[type
];
207 if (!(p
->flags
& SWP_USED
))
209 offset
= swp_offset(entry
);
210 if (offset
>= p
->max
)
212 if (!p
->swap_map
[offset
])
219 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
222 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
225 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
228 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
233 static void swap_info_put(struct swap_info_struct
* p
)
235 swap_device_unlock(p
);
239 static int swap_entry_free(struct swap_info_struct
*p
, unsigned long offset
)
241 int count
= p
->swap_map
[offset
];
243 if (count
< SWAP_MAP_MAX
) {
245 p
->swap_map
[offset
] = count
;
247 if (offset
< p
->lowest_bit
)
248 p
->lowest_bit
= offset
;
249 if (offset
> p
->highest_bit
)
250 p
->highest_bit
= offset
;
251 if (p
->prio
> swap_info
[swap_list
.next
].prio
)
252 swap_list
.next
= p
- swap_info
;
261 * Caller has made sure that the swapdevice corresponding to entry
262 * is still around or has not been recycled.
264 void swap_free(swp_entry_t entry
)
266 struct swap_info_struct
* p
;
268 p
= swap_info_get(entry
);
270 swap_entry_free(p
, swp_offset(entry
));
276 * How many references to page are currently swapped out?
278 static inline int page_swapcount(struct page
*page
)
281 struct swap_info_struct
*p
;
284 entry
.val
= page
->private;
285 p
= swap_info_get(entry
);
287 /* Subtract the 1 for the swap cache itself */
288 count
= p
->swap_map
[swp_offset(entry
)] - 1;
295 * We can use this swap cache entry directly
296 * if there are no other references to it.
298 int can_share_swap_page(struct page
*page
)
302 BUG_ON(!PageLocked(page
));
303 count
= page_mapcount(page
);
304 if (count
<= 1 && PageSwapCache(page
))
305 count
+= page_swapcount(page
);
310 * Work out if there are any other processes sharing this
311 * swap cache page. Free it if you can. Return success.
313 int remove_exclusive_swap_page(struct page
*page
)
316 struct swap_info_struct
* p
;
319 BUG_ON(PagePrivate(page
));
320 BUG_ON(!PageLocked(page
));
322 if (!PageSwapCache(page
))
324 if (PageWriteback(page
))
326 if (page_count(page
) != 2) /* 2: us + cache */
329 entry
.val
= page
->private;
330 p
= swap_info_get(entry
);
334 /* Is the only swap cache user the cache itself? */
336 if (p
->swap_map
[swp_offset(entry
)] == 1) {
337 /* Recheck the page count with the swapcache lock held.. */
338 write_lock_irq(&swapper_space
.tree_lock
);
339 if ((page_count(page
) == 2) && !PageWriteback(page
)) {
340 __delete_from_swap_cache(page
);
344 write_unlock_irq(&swapper_space
.tree_lock
);
350 page_cache_release(page
);
357 * Free the swap entry like above, but also try to
358 * free the page cache entry if it is the last user.
360 void free_swap_and_cache(swp_entry_t entry
)
362 struct swap_info_struct
* p
;
363 struct page
*page
= NULL
;
365 p
= swap_info_get(entry
);
367 if (swap_entry_free(p
, swp_offset(entry
)) == 1)
368 page
= find_trylock_page(&swapper_space
, entry
.val
);
374 BUG_ON(PagePrivate(page
));
375 page_cache_get(page
);
376 one_user
= (page_count(page
) == 2);
377 /* Only cache user (+us), or swap space full? Free it! */
378 if (!PageWriteback(page
) && (one_user
|| vm_swap_full())) {
379 delete_from_swap_cache(page
);
383 page_cache_release(page
);
388 * Always set the resulting pte to be nowrite (the same as COW pages
389 * after one process has exited). We don't know just how many PTEs will
390 * share this swap entry, so be cautious and let do_wp_page work out
391 * what to do if a write is requested later.
393 * vma->vm_mm->page_table_lock is held.
395 static void unuse_pte(struct vm_area_struct
*vma
, pte_t
*pte
,
396 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
398 inc_mm_counter(vma
->vm_mm
, rss
);
400 set_pte_at(vma
->vm_mm
, addr
, pte
,
401 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
402 page_add_anon_rmap(page
, vma
, addr
);
405 * Move the page to the active list so it is not
406 * immediately swapped out again after swapon.
411 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
412 unsigned long addr
, unsigned long end
,
413 swp_entry_t entry
, struct page
*page
)
416 pte_t swp_pte
= swp_entry_to_pte(entry
);
418 pte
= pte_offset_map(pmd
, addr
);
421 * swapoff spends a _lot_ of time in this loop!
422 * Test inline before going to call unuse_pte.
424 if (unlikely(pte_same(*pte
, swp_pte
))) {
425 unuse_pte(vma
, pte
, addr
, entry
, page
);
429 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
434 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
435 unsigned long addr
, unsigned long end
,
436 swp_entry_t entry
, struct page
*page
)
441 pmd
= pmd_offset(pud
, addr
);
443 next
= pmd_addr_end(addr
, end
);
444 if (pmd_none_or_clear_bad(pmd
))
446 if (unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
))
448 } while (pmd
++, addr
= next
, addr
!= end
);
452 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
453 unsigned long addr
, unsigned long end
,
454 swp_entry_t entry
, struct page
*page
)
459 pud
= pud_offset(pgd
, addr
);
461 next
= pud_addr_end(addr
, end
);
462 if (pud_none_or_clear_bad(pud
))
464 if (unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
))
466 } while (pud
++, addr
= next
, addr
!= end
);
470 static int unuse_vma(struct vm_area_struct
*vma
,
471 swp_entry_t entry
, struct page
*page
)
474 unsigned long addr
, end
, next
;
477 addr
= page_address_in_vma(page
, vma
);
481 end
= addr
+ PAGE_SIZE
;
483 addr
= vma
->vm_start
;
487 pgd
= pgd_offset(vma
->vm_mm
, addr
);
489 next
= pgd_addr_end(addr
, end
);
490 if (pgd_none_or_clear_bad(pgd
))
492 if (unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
))
494 } while (pgd
++, addr
= next
, addr
!= end
);
498 static int unuse_mm(struct mm_struct
*mm
,
499 swp_entry_t entry
, struct page
*page
)
501 struct vm_area_struct
*vma
;
503 if (!down_read_trylock(&mm
->mmap_sem
)) {
505 * Activate page so shrink_cache is unlikely to unmap its
506 * ptes while lock is dropped, so swapoff can make progress.
510 down_read(&mm
->mmap_sem
);
513 spin_lock(&mm
->page_table_lock
);
514 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
515 if (vma
->anon_vma
&& unuse_vma(vma
, entry
, page
))
518 spin_unlock(&mm
->page_table_lock
);
519 up_read(&mm
->mmap_sem
);
521 * Currently unuse_mm cannot fail, but leave error handling
522 * at call sites for now, since we change it from time to time.
528 * Scan swap_map from current position to next entry still in use.
529 * Recycle to start on reaching the end, returning 0 when empty.
531 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
534 unsigned int max
= si
->max
;
535 unsigned int i
= prev
;
539 * No need for swap_device_lock(si) here: we're just looking
540 * for whether an entry is in use, not modifying it; false
541 * hits are okay, and sys_swapoff() has already prevented new
542 * allocations from this area (while holding swap_list_lock()).
551 * No entries in use at top of swap_map,
552 * loop back to start and recheck there.
558 count
= si
->swap_map
[i
];
559 if (count
&& count
!= SWAP_MAP_BAD
)
566 * We completely avoid races by reading each swap page in advance,
567 * and then search for the process using it. All the necessary
568 * page table adjustments can then be made atomically.
570 static int try_to_unuse(unsigned int type
)
572 struct swap_info_struct
* si
= &swap_info
[type
];
573 struct mm_struct
*start_mm
;
574 unsigned short *swap_map
;
575 unsigned short swcount
;
580 int reset_overflow
= 0;
584 * When searching mms for an entry, a good strategy is to
585 * start at the first mm we freed the previous entry from
586 * (though actually we don't notice whether we or coincidence
587 * freed the entry). Initialize this start_mm with a hold.
589 * A simpler strategy would be to start at the last mm we
590 * freed the previous entry from; but that would take less
591 * advantage of mmlist ordering, which clusters forked mms
592 * together, child after parent. If we race with dup_mmap(), we
593 * prefer to resolve parent before child, lest we miss entries
594 * duplicated after we scanned child: using last mm would invert
595 * that. Though it's only a serious concern when an overflowed
596 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
599 atomic_inc(&init_mm
.mm_users
);
602 * Keep on scanning until all entries have gone. Usually,
603 * one pass through swap_map is enough, but not necessarily:
604 * there are races when an instance of an entry might be missed.
606 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
607 if (signal_pending(current
)) {
613 * Get a page for the entry, using the existing swap
614 * cache page if there is one. Otherwise, get a clean
615 * page and read the swap into it.
617 swap_map
= &si
->swap_map
[i
];
618 entry
= swp_entry(type
, i
);
619 page
= read_swap_cache_async(entry
, NULL
, 0);
622 * Either swap_duplicate() failed because entry
623 * has been freed independently, and will not be
624 * reused since sys_swapoff() already disabled
625 * allocation from here, or alloc_page() failed.
634 * Don't hold on to start_mm if it looks like exiting.
636 if (atomic_read(&start_mm
->mm_users
) == 1) {
639 atomic_inc(&init_mm
.mm_users
);
643 * Wait for and lock page. When do_swap_page races with
644 * try_to_unuse, do_swap_page can handle the fault much
645 * faster than try_to_unuse can locate the entry. This
646 * apparently redundant "wait_on_page_locked" lets try_to_unuse
647 * defer to do_swap_page in such a case - in some tests,
648 * do_swap_page and try_to_unuse repeatedly compete.
650 wait_on_page_locked(page
);
651 wait_on_page_writeback(page
);
653 wait_on_page_writeback(page
);
656 * Remove all references to entry.
657 * Whenever we reach init_mm, there's no address space
658 * to search, but use it as a reminder to search shmem.
663 if (start_mm
== &init_mm
)
664 shmem
= shmem_unuse(entry
, page
);
666 retval
= unuse_mm(start_mm
, entry
, page
);
669 int set_start_mm
= (*swap_map
>= swcount
);
670 struct list_head
*p
= &start_mm
->mmlist
;
671 struct mm_struct
*new_start_mm
= start_mm
;
672 struct mm_struct
*prev_mm
= start_mm
;
673 struct mm_struct
*mm
;
675 atomic_inc(&new_start_mm
->mm_users
);
676 atomic_inc(&prev_mm
->mm_users
);
677 spin_lock(&mmlist_lock
);
678 while (*swap_map
> 1 && !retval
&&
679 (p
= p
->next
) != &start_mm
->mmlist
) {
680 mm
= list_entry(p
, struct mm_struct
, mmlist
);
681 if (atomic_inc_return(&mm
->mm_users
) == 1) {
682 atomic_dec(&mm
->mm_users
);
685 spin_unlock(&mmlist_lock
);
694 else if (mm
== &init_mm
) {
696 shmem
= shmem_unuse(entry
, page
);
698 retval
= unuse_mm(mm
, entry
, page
);
699 if (set_start_mm
&& *swap_map
< swcount
) {
701 atomic_inc(&mm
->mm_users
);
705 spin_lock(&mmlist_lock
);
707 spin_unlock(&mmlist_lock
);
710 start_mm
= new_start_mm
;
714 page_cache_release(page
);
719 * How could swap count reach 0x7fff when the maximum
720 * pid is 0x7fff, and there's no way to repeat a swap
721 * page within an mm (except in shmem, where it's the
722 * shared object which takes the reference count)?
723 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
725 * If that's wrong, then we should worry more about
726 * exit_mmap() and do_munmap() cases described above:
727 * we might be resetting SWAP_MAP_MAX too early here.
728 * We know "Undead"s can happen, they're okay, so don't
729 * report them; but do report if we reset SWAP_MAP_MAX.
731 if (*swap_map
== SWAP_MAP_MAX
) {
732 swap_device_lock(si
);
734 swap_device_unlock(si
);
739 * If a reference remains (rare), we would like to leave
740 * the page in the swap cache; but try_to_unmap could
741 * then re-duplicate the entry once we drop page lock,
742 * so we might loop indefinitely; also, that page could
743 * not be swapped out to other storage meanwhile. So:
744 * delete from cache even if there's another reference,
745 * after ensuring that the data has been saved to disk -
746 * since if the reference remains (rarer), it will be
747 * read from disk into another page. Splitting into two
748 * pages would be incorrect if swap supported "shared
749 * private" pages, but they are handled by tmpfs files.
751 * Note shmem_unuse already deleted a swappage from
752 * the swap cache, unless the move to filepage failed:
753 * in which case it left swappage in cache, lowered its
754 * swap count to pass quickly through the loops above,
755 * and now we must reincrement count to try again later.
757 if ((*swap_map
> 1) && PageDirty(page
) && PageSwapCache(page
)) {
758 struct writeback_control wbc
= {
759 .sync_mode
= WB_SYNC_NONE
,
762 swap_writepage(page
, &wbc
);
764 wait_on_page_writeback(page
);
766 if (PageSwapCache(page
)) {
768 swap_duplicate(entry
);
770 delete_from_swap_cache(page
);
774 * So we could skip searching mms once swap count went
775 * to 1, we did not mark any present ptes as dirty: must
776 * mark page dirty so shrink_list will preserve it.
780 page_cache_release(page
);
783 * Make sure that we aren't completely killing
784 * interactive performance.
790 if (reset_overflow
) {
791 printk(KERN_WARNING
"swapoff: cleared swap entry overflow\n");
798 * After a successful try_to_unuse, if no swap is now in use, we know we
799 * can empty the mmlist. swap_list_lock must be held on entry and exit.
800 * Note that mmlist_lock nests inside swap_list_lock, and an mm must be
801 * added to the mmlist just after page_duplicate - before would be racy.
803 static void drain_mmlist(void)
805 struct list_head
*p
, *next
;
808 for (i
= 0; i
< nr_swapfiles
; i
++)
809 if (swap_info
[i
].inuse_pages
)
811 spin_lock(&mmlist_lock
);
812 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
814 spin_unlock(&mmlist_lock
);
818 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
819 * corresponds to page offset `offset'.
821 sector_t
map_swap_page(struct swap_info_struct
*sis
, pgoff_t offset
)
823 struct swap_extent
*se
= sis
->curr_swap_extent
;
824 struct swap_extent
*start_se
= se
;
827 struct list_head
*lh
;
829 if (se
->start_page
<= offset
&&
830 offset
< (se
->start_page
+ se
->nr_pages
)) {
831 return se
->start_block
+ (offset
- se
->start_page
);
834 if (lh
== &sis
->extent_list
)
836 se
= list_entry(lh
, struct swap_extent
, list
);
837 sis
->curr_swap_extent
= se
;
838 BUG_ON(se
== start_se
); /* It *must* be present */
843 * Free all of a swapdev's extent information
845 static void destroy_swap_extents(struct swap_info_struct
*sis
)
847 while (!list_empty(&sis
->extent_list
)) {
848 struct swap_extent
*se
;
850 se
= list_entry(sis
->extent_list
.next
,
851 struct swap_extent
, list
);
858 * Add a block range (and the corresponding page range) into this swapdev's
859 * extent list. The extent list is kept sorted in page order.
861 * This function rather assumes that it is called in ascending page order.
864 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
865 unsigned long nr_pages
, sector_t start_block
)
867 struct swap_extent
*se
;
868 struct swap_extent
*new_se
;
869 struct list_head
*lh
;
871 lh
= sis
->extent_list
.prev
; /* The highest page extent */
872 if (lh
!= &sis
->extent_list
) {
873 se
= list_entry(lh
, struct swap_extent
, list
);
874 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
875 if (se
->start_block
+ se
->nr_pages
== start_block
) {
877 se
->nr_pages
+= nr_pages
;
883 * No merge. Insert a new extent, preserving ordering.
885 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
888 new_se
->start_page
= start_page
;
889 new_se
->nr_pages
= nr_pages
;
890 new_se
->start_block
= start_block
;
892 list_add_tail(&new_se
->list
, &sis
->extent_list
);
897 * A `swap extent' is a simple thing which maps a contiguous range of pages
898 * onto a contiguous range of disk blocks. An ordered list of swap extents
899 * is built at swapon time and is then used at swap_writepage/swap_readpage
900 * time for locating where on disk a page belongs.
902 * If the swapfile is an S_ISBLK block device, a single extent is installed.
903 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
904 * swap files identically.
906 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
907 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
908 * swapfiles are handled *identically* after swapon time.
910 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
911 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
912 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
913 * requirements, they are simply tossed out - we will never use those blocks
916 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
917 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
918 * which will scribble on the fs.
920 * The amount of disk space which a single swap extent represents varies.
921 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
922 * extents in the list. To avoid much list walking, we cache the previous
923 * search location in `curr_swap_extent', and start new searches from there.
924 * This is extremely effective. The average number of iterations in
925 * map_swap_page() has been measured at about 0.3 per page. - akpm.
927 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
930 unsigned blocks_per_page
;
931 unsigned long page_no
;
933 sector_t probe_block
;
935 sector_t lowest_block
= -1;
936 sector_t highest_block
= 0;
940 inode
= sis
->swap_file
->f_mapping
->host
;
941 if (S_ISBLK(inode
->i_mode
)) {
942 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
947 blkbits
= inode
->i_blkbits
;
948 blocks_per_page
= PAGE_SIZE
>> blkbits
;
951 * Map all the blocks into the extent list. This code doesn't try
956 last_block
= i_size_read(inode
) >> blkbits
;
957 while ((probe_block
+ blocks_per_page
) <= last_block
&&
958 page_no
< sis
->max
) {
959 unsigned block_in_page
;
960 sector_t first_block
;
962 first_block
= bmap(inode
, probe_block
);
963 if (first_block
== 0)
967 * It must be PAGE_SIZE aligned on-disk
969 if (first_block
& (blocks_per_page
- 1)) {
974 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
978 block
= bmap(inode
, probe_block
+ block_in_page
);
981 if (block
!= first_block
+ block_in_page
) {
988 first_block
>>= (PAGE_SHIFT
- blkbits
);
989 if (page_no
) { /* exclude the header page */
990 if (first_block
< lowest_block
)
991 lowest_block
= first_block
;
992 if (first_block
> highest_block
)
993 highest_block
= first_block
;
997 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
999 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1004 probe_block
+= blocks_per_page
;
1009 *span
= 1 + highest_block
- lowest_block
;
1011 page_no
= 1; /* force Empty message */
1013 sis
->pages
= page_no
- 1;
1014 sis
->highest_bit
= page_no
- 1;
1016 sis
->curr_swap_extent
= list_entry(sis
->extent_list
.prev
,
1017 struct swap_extent
, list
);
1020 printk(KERN_ERR
"swapon: swapfile has holes\n");
1026 #if 0 /* We don't need this yet */
1027 #include <linux/backing-dev.h>
1028 int page_queue_congested(struct page
*page
)
1030 struct backing_dev_info
*bdi
;
1032 BUG_ON(!PageLocked(page
)); /* It pins the swap_info_struct */
1034 if (PageSwapCache(page
)) {
1035 swp_entry_t entry
= { .val
= page
->private };
1036 struct swap_info_struct
*sis
;
1038 sis
= get_swap_info_struct(swp_type(entry
));
1039 bdi
= sis
->bdev
->bd_inode
->i_mapping
->backing_dev_info
;
1041 bdi
= page
->mapping
->backing_dev_info
;
1042 return bdi_write_congested(bdi
);
1046 asmlinkage
long sys_swapoff(const char __user
* specialfile
)
1048 struct swap_info_struct
* p
= NULL
;
1049 unsigned short *swap_map
;
1050 struct file
*swap_file
, *victim
;
1051 struct address_space
*mapping
;
1052 struct inode
*inode
;
1057 if (!capable(CAP_SYS_ADMIN
))
1060 pathname
= getname(specialfile
);
1061 err
= PTR_ERR(pathname
);
1062 if (IS_ERR(pathname
))
1065 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1067 err
= PTR_ERR(victim
);
1071 mapping
= victim
->f_mapping
;
1074 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
].next
) {
1075 p
= swap_info
+ type
;
1076 if ((p
->flags
& SWP_ACTIVE
) == SWP_ACTIVE
) {
1077 if (p
->swap_file
->f_mapping
== mapping
)
1087 if (!security_vm_enough_memory(p
->pages
))
1088 vm_unacct_memory(p
->pages
);
1095 swap_list
.head
= p
->next
;
1097 swap_info
[prev
].next
= p
->next
;
1099 if (type
== swap_list
.next
) {
1100 /* just pick something that's safe... */
1101 swap_list
.next
= swap_list
.head
;
1103 nr_swap_pages
-= p
->pages
;
1104 total_swap_pages
-= p
->pages
;
1105 swap_device_lock(p
);
1106 p
->flags
&= ~SWP_WRITEOK
;
1107 swap_device_unlock(p
);
1110 current
->flags
|= PF_SWAPOFF
;
1111 err
= try_to_unuse(type
);
1112 current
->flags
&= ~PF_SWAPOFF
;
1114 /* wait for any unplug function to finish */
1115 down_write(&swap_unplug_sem
);
1116 up_write(&swap_unplug_sem
);
1119 /* re-insert swap space back into swap_list */
1121 for (prev
= -1, i
= swap_list
.head
; i
>= 0; prev
= i
, i
= swap_info
[i
].next
)
1122 if (p
->prio
>= swap_info
[i
].prio
)
1126 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1128 swap_info
[prev
].next
= p
- swap_info
;
1129 nr_swap_pages
+= p
->pages
;
1130 total_swap_pages
+= p
->pages
;
1131 p
->flags
|= SWP_WRITEOK
;
1135 destroy_swap_extents(p
);
1139 swap_device_lock(p
);
1140 swap_file
= p
->swap_file
;
1141 p
->swap_file
= NULL
;
1143 swap_map
= p
->swap_map
;
1146 swap_device_unlock(p
);
1150 inode
= mapping
->host
;
1151 if (S_ISBLK(inode
->i_mode
)) {
1152 struct block_device
*bdev
= I_BDEV(inode
);
1153 set_blocksize(bdev
, p
->old_block_size
);
1156 down(&inode
->i_sem
);
1157 inode
->i_flags
&= ~S_SWAPFILE
;
1160 filp_close(swap_file
, NULL
);
1164 filp_close(victim
, NULL
);
1169 #ifdef CONFIG_PROC_FS
1171 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1173 struct swap_info_struct
*ptr
= swap_info
;
1179 for (i
= 0; i
< nr_swapfiles
; i
++, ptr
++) {
1180 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1189 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1191 struct swap_info_struct
*ptr
= v
;
1192 struct swap_info_struct
*endptr
= swap_info
+ nr_swapfiles
;
1194 for (++ptr
; ptr
< endptr
; ptr
++) {
1195 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1204 static void swap_stop(struct seq_file
*swap
, void *v
)
1209 static int swap_show(struct seq_file
*swap
, void *v
)
1211 struct swap_info_struct
*ptr
= v
;
1216 seq_puts(swap
, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1218 file
= ptr
->swap_file
;
1219 len
= seq_path(swap
, file
->f_vfsmnt
, file
->f_dentry
, " \t\n\\");
1220 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1221 len
< 40 ? 40 - len
: 1, " ",
1222 S_ISBLK(file
->f_dentry
->d_inode
->i_mode
) ?
1223 "partition" : "file\t",
1224 ptr
->pages
<< (PAGE_SHIFT
- 10),
1225 ptr
->inuse_pages
<< (PAGE_SHIFT
- 10),
1230 static struct seq_operations swaps_op
= {
1231 .start
= swap_start
,
1237 static int swaps_open(struct inode
*inode
, struct file
*file
)
1239 return seq_open(file
, &swaps_op
);
1242 static struct file_operations proc_swaps_operations
= {
1245 .llseek
= seq_lseek
,
1246 .release
= seq_release
,
1249 static int __init
procswaps_init(void)
1251 struct proc_dir_entry
*entry
;
1253 entry
= create_proc_entry("swaps", 0, NULL
);
1255 entry
->proc_fops
= &proc_swaps_operations
;
1258 __initcall(procswaps_init
);
1259 #endif /* CONFIG_PROC_FS */
1262 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1264 * The swapon system call
1266 asmlinkage
long sys_swapon(const char __user
* specialfile
, int swap_flags
)
1268 struct swap_info_struct
* p
;
1270 struct block_device
*bdev
= NULL
;
1271 struct file
*swap_file
= NULL
;
1272 struct address_space
*mapping
;
1276 static int least_priority
;
1277 union swap_header
*swap_header
= NULL
;
1278 int swap_header_version
;
1279 unsigned int nr_good_pages
= 0;
1282 unsigned long maxpages
= 1;
1284 unsigned short *swap_map
;
1285 struct page
*page
= NULL
;
1286 struct inode
*inode
= NULL
;
1289 if (!capable(CAP_SYS_ADMIN
))
1293 for (type
= 0 ; type
< nr_swapfiles
; type
++,p
++)
1294 if (!(p
->flags
& SWP_USED
))
1298 * Test if adding another swap device is possible. There are
1299 * two limiting factors: 1) the number of bits for the swap
1300 * type swp_entry_t definition and 2) the number of bits for
1301 * the swap type in the swap ptes as defined by the different
1302 * architectures. To honor both limitations a swap entry
1303 * with swap offset 0 and swap type ~0UL is created, encoded
1304 * to a swap pte, decoded to a swp_entry_t again and finally
1305 * the swap type part is extracted. This will mask all bits
1306 * from the initial ~0UL that can't be encoded in either the
1307 * swp_entry_t or the architecture definition of a swap pte.
1309 if (type
> swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1313 if (type
>= nr_swapfiles
)
1314 nr_swapfiles
= type
+1;
1315 INIT_LIST_HEAD(&p
->extent_list
);
1316 p
->flags
= SWP_USED
;
1317 p
->swap_file
= NULL
;
1318 p
->old_block_size
= 0;
1324 spin_lock_init(&p
->sdev_lock
);
1326 if (swap_flags
& SWAP_FLAG_PREFER
) {
1328 (swap_flags
& SWAP_FLAG_PRIO_MASK
)>>SWAP_FLAG_PRIO_SHIFT
;
1330 p
->prio
= --least_priority
;
1333 name
= getname(specialfile
);
1334 error
= PTR_ERR(name
);
1339 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1340 error
= PTR_ERR(swap_file
);
1341 if (IS_ERR(swap_file
)) {
1346 p
->swap_file
= swap_file
;
1347 mapping
= swap_file
->f_mapping
;
1348 inode
= mapping
->host
;
1351 for (i
= 0; i
< nr_swapfiles
; i
++) {
1352 struct swap_info_struct
*q
= &swap_info
[i
];
1354 if (i
== type
|| !q
->swap_file
)
1356 if (mapping
== q
->swap_file
->f_mapping
)
1361 if (S_ISBLK(inode
->i_mode
)) {
1362 bdev
= I_BDEV(inode
);
1363 error
= bd_claim(bdev
, sys_swapon
);
1368 p
->old_block_size
= block_size(bdev
);
1369 error
= set_blocksize(bdev
, PAGE_SIZE
);
1373 } else if (S_ISREG(inode
->i_mode
)) {
1374 p
->bdev
= inode
->i_sb
->s_bdev
;
1375 down(&inode
->i_sem
);
1377 if (IS_SWAPFILE(inode
)) {
1385 swapfilesize
= i_size_read(inode
) >> PAGE_SHIFT
;
1388 * Read the swap header.
1390 if (!mapping
->a_ops
->readpage
) {
1394 page
= read_cache_page(mapping
, 0,
1395 (filler_t
*)mapping
->a_ops
->readpage
, swap_file
);
1397 error
= PTR_ERR(page
);
1400 wait_on_page_locked(page
);
1401 if (!PageUptodate(page
))
1404 swap_header
= page_address(page
);
1406 if (!memcmp("SWAP-SPACE",swap_header
->magic
.magic
,10))
1407 swap_header_version
= 1;
1408 else if (!memcmp("SWAPSPACE2",swap_header
->magic
.magic
,10))
1409 swap_header_version
= 2;
1411 printk("Unable to find swap-space signature\n");
1416 switch (swap_header_version
) {
1418 printk(KERN_ERR
"version 0 swap is no longer supported. "
1419 "Use mkswap -v1 %s\n", name
);
1423 /* Check the swap header's sub-version and the size of
1424 the swap file and bad block lists */
1425 if (swap_header
->info
.version
!= 1) {
1427 "Unable to handle swap header version %d\n",
1428 swap_header
->info
.version
);
1435 * Find out how many pages are allowed for a single swap
1436 * device. There are two limiting factors: 1) the number of
1437 * bits for the swap offset in the swp_entry_t type and
1438 * 2) the number of bits in the a swap pte as defined by
1439 * the different architectures. In order to find the
1440 * largest possible bit mask a swap entry with swap type 0
1441 * and swap offset ~0UL is created, encoded to a swap pte,
1442 * decoded to a swp_entry_t again and finally the swap
1443 * offset is extracted. This will mask all the bits from
1444 * the initial ~0UL mask that can't be encoded in either
1445 * the swp_entry_t or the architecture definition of a
1448 maxpages
= swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1449 if (maxpages
> swap_header
->info
.last_page
)
1450 maxpages
= swap_header
->info
.last_page
;
1451 p
->highest_bit
= maxpages
- 1;
1456 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1458 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1461 /* OK, set up the swap map and apply the bad block list */
1462 if (!(p
->swap_map
= vmalloc(maxpages
* sizeof(short)))) {
1468 memset(p
->swap_map
, 0, maxpages
* sizeof(short));
1469 for (i
=0; i
<swap_header
->info
.nr_badpages
; i
++) {
1470 int page
= swap_header
->info
.badpages
[i
];
1471 if (page
<= 0 || page
>= swap_header
->info
.last_page
)
1474 p
->swap_map
[page
] = SWAP_MAP_BAD
;
1476 nr_good_pages
= swap_header
->info
.last_page
-
1477 swap_header
->info
.nr_badpages
-
1478 1 /* header page */;
1483 if (swapfilesize
&& maxpages
> swapfilesize
) {
1485 "Swap area shorter than signature indicates\n");
1489 if (nr_good_pages
) {
1490 p
->swap_map
[0] = SWAP_MAP_BAD
;
1492 p
->pages
= nr_good_pages
;
1493 nr_extents
= setup_swap_extents(p
, &span
);
1494 if (nr_extents
< 0) {
1498 nr_good_pages
= p
->pages
;
1500 if (!nr_good_pages
) {
1501 printk(KERN_WARNING
"Empty swap-file\n");
1508 swap_device_lock(p
);
1509 p
->flags
= SWP_ACTIVE
;
1510 nr_swap_pages
+= nr_good_pages
;
1511 total_swap_pages
+= nr_good_pages
;
1513 printk(KERN_INFO
"Adding %uk swap on %s. "
1514 "Priority:%d extents:%d across:%lluk\n",
1515 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
1516 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10));
1518 /* insert swap space into swap_list: */
1520 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1521 if (p
->prio
>= swap_info
[i
].prio
) {
1528 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1530 swap_info
[prev
].next
= p
- swap_info
;
1532 swap_device_unlock(p
);
1539 set_blocksize(bdev
, p
->old_block_size
);
1542 destroy_swap_extents(p
);
1545 swap_map
= p
->swap_map
;
1546 p
->swap_file
= NULL
;
1549 if (!(swap_flags
& SWAP_FLAG_PREFER
))
1554 filp_close(swap_file
, NULL
);
1556 if (page
&& !IS_ERR(page
)) {
1558 page_cache_release(page
);
1564 inode
->i_flags
|= S_SWAPFILE
;
1570 void si_swapinfo(struct sysinfo
*val
)
1573 unsigned long nr_to_be_unused
= 0;
1576 for (i
= 0; i
< nr_swapfiles
; i
++) {
1577 if (!(swap_info
[i
].flags
& SWP_USED
) ||
1578 (swap_info
[i
].flags
& SWP_WRITEOK
))
1580 nr_to_be_unused
+= swap_info
[i
].inuse_pages
;
1582 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
1583 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
1588 * Verify that a swap entry is valid and increment its swap map count.
1590 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1591 * "permanent", but will be reclaimed by the next swapoff.
1593 int swap_duplicate(swp_entry_t entry
)
1595 struct swap_info_struct
* p
;
1596 unsigned long offset
, type
;
1599 type
= swp_type(entry
);
1600 if (type
>= nr_swapfiles
)
1602 p
= type
+ swap_info
;
1603 offset
= swp_offset(entry
);
1605 swap_device_lock(p
);
1606 if (offset
< p
->max
&& p
->swap_map
[offset
]) {
1607 if (p
->swap_map
[offset
] < SWAP_MAP_MAX
- 1) {
1608 p
->swap_map
[offset
]++;
1610 } else if (p
->swap_map
[offset
] <= SWAP_MAP_MAX
) {
1611 if (swap_overflow
++ < 5)
1612 printk(KERN_WARNING
"swap_dup: swap entry overflow\n");
1613 p
->swap_map
[offset
] = SWAP_MAP_MAX
;
1617 swap_device_unlock(p
);
1622 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
1626 struct swap_info_struct
*
1627 get_swap_info_struct(unsigned type
)
1629 return &swap_info
[type
];
1633 * swap_device_lock prevents swap_map being freed. Don't grab an extra
1634 * reference on the swaphandle, it doesn't matter if it becomes unused.
1636 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
1638 int ret
= 0, i
= 1 << page_cluster
;
1640 struct swap_info_struct
*swapdev
= swp_type(entry
) + swap_info
;
1642 if (!page_cluster
) /* no readahead */
1644 toff
= (swp_offset(entry
) >> page_cluster
) << page_cluster
;
1645 if (!toff
) /* first page is swap header */
1649 swap_device_lock(swapdev
);
1651 /* Don't read-ahead past the end of the swap area */
1652 if (toff
>= swapdev
->max
)
1654 /* Don't read in free or bad pages */
1655 if (!swapdev
->swap_map
[toff
])
1657 if (swapdev
->swap_map
[toff
] == SWAP_MAP_BAD
)
1662 swap_device_unlock(swapdev
);