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 void swap_unplug_io_fn(struct backing_dev_info
*unused_bdi
, struct page
*page
)
63 down_read(&swap_unplug_sem
);
64 entry
.val
= page
->private;
65 if (PageSwapCache(page
)) {
66 struct block_device
*bdev
= swap_info
[swp_type(entry
)].bdev
;
67 struct backing_dev_info
*bdi
;
70 * If the page is removed from swapcache from under us (with a
71 * racy try_to_unuse/swapoff) we need an additional reference
72 * count to avoid reading garbage from page->private above. If
73 * the WARN_ON triggers during a swapoff it maybe the race
74 * condition and it's harmless. However if it triggers without
75 * swapoff it signals a problem.
77 WARN_ON(page_count(page
) <= 1);
79 bdi
= bdev
->bd_inode
->i_mapping
->backing_dev_info
;
80 blk_run_backing_dev(bdi
, page
);
82 up_read(&swap_unplug_sem
);
85 #define SWAPFILE_CLUSTER 256
86 #define LATENCY_LIMIT 256
88 static inline unsigned long scan_swap_map(struct swap_info_struct
*si
)
90 unsigned long offset
, last_in_cluster
;
91 int latency_ration
= LATENCY_LIMIT
;
94 * We try to cluster swap pages by allocating them sequentially
95 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
96 * way, however, we resort to first-free allocation, starting
97 * a new cluster. This prevents us from scattering swap pages
98 * all over the entire swap partition, so that we reduce
99 * overall disk seek times between swap pages. -- sct
100 * But we do now try to find an empty cluster. -Andrea
103 si
->flags
+= SWP_SCANNING
;
104 if (unlikely(!si
->cluster_nr
)) {
105 si
->cluster_nr
= SWAPFILE_CLUSTER
- 1;
106 if (si
->pages
- si
->inuse_pages
< SWAPFILE_CLUSTER
)
108 swap_device_unlock(si
);
110 offset
= si
->lowest_bit
;
111 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
- 1;
113 /* Locate the first empty (unaligned) cluster */
114 for (; last_in_cluster
<= si
->highest_bit
; offset
++) {
115 if (si
->swap_map
[offset
])
116 last_in_cluster
= offset
+ SWAPFILE_CLUSTER
;
117 else if (offset
== last_in_cluster
) {
118 swap_device_lock(si
);
119 si
->cluster_next
= offset
-SWAPFILE_CLUSTER
-1;
122 if (unlikely(--latency_ration
< 0)) {
124 latency_ration
= LATENCY_LIMIT
;
127 swap_device_lock(si
);
133 offset
= si
->cluster_next
;
134 if (offset
> si
->highest_bit
)
135 lowest
: offset
= si
->lowest_bit
;
136 checks
: if (!(si
->flags
& SWP_WRITEOK
))
138 if (!si
->highest_bit
)
140 if (!si
->swap_map
[offset
]) {
141 if (offset
== si
->lowest_bit
)
143 if (offset
== si
->highest_bit
)
146 if (si
->inuse_pages
== si
->pages
) {
147 si
->lowest_bit
= si
->max
;
150 si
->swap_map
[offset
] = 1;
151 si
->cluster_next
= offset
+ 1;
152 si
->flags
-= SWP_SCANNING
;
156 swap_device_unlock(si
);
157 while (++offset
<= si
->highest_bit
) {
158 if (!si
->swap_map
[offset
]) {
159 swap_device_lock(si
);
162 if (unlikely(--latency_ration
< 0)) {
164 latency_ration
= LATENCY_LIMIT
;
167 swap_device_lock(si
);
171 si
->flags
-= SWP_SCANNING
;
175 swp_entry_t
get_swap_page(void)
177 struct swap_info_struct
*si
;
183 if (nr_swap_pages
<= 0)
187 for (type
= swap_list
.next
; type
>= 0 && wrapped
< 2; type
= next
) {
188 si
= swap_info
+ type
;
191 (!wrapped
&& si
->prio
!= swap_info
[next
].prio
)) {
192 next
= swap_list
.head
;
196 if (!si
->highest_bit
)
198 if (!(si
->flags
& SWP_WRITEOK
))
201 swap_list
.next
= next
;
202 swap_device_lock(si
);
204 offset
= scan_swap_map(si
);
205 swap_device_unlock(si
);
207 return swp_entry(type
, offset
);
209 next
= swap_list
.next
;
215 return (swp_entry_t
) {0};
218 static struct swap_info_struct
* swap_info_get(swp_entry_t entry
)
220 struct swap_info_struct
* p
;
221 unsigned long offset
, type
;
225 type
= swp_type(entry
);
226 if (type
>= nr_swapfiles
)
228 p
= & swap_info
[type
];
229 if (!(p
->flags
& SWP_USED
))
231 offset
= swp_offset(entry
);
232 if (offset
>= p
->max
)
234 if (!p
->swap_map
[offset
])
241 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_offset
, entry
.val
);
244 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_offset
, entry
.val
);
247 printk(KERN_ERR
"swap_free: %s%08lx\n", Unused_file
, entry
.val
);
250 printk(KERN_ERR
"swap_free: %s%08lx\n", Bad_file
, entry
.val
);
255 static void swap_info_put(struct swap_info_struct
* p
)
257 swap_device_unlock(p
);
261 static int swap_entry_free(struct swap_info_struct
*p
, unsigned long offset
)
263 int count
= p
->swap_map
[offset
];
265 if (count
< SWAP_MAP_MAX
) {
267 p
->swap_map
[offset
] = count
;
269 if (offset
< p
->lowest_bit
)
270 p
->lowest_bit
= offset
;
271 if (offset
> p
->highest_bit
)
272 p
->highest_bit
= offset
;
273 if (p
->prio
> swap_info
[swap_list
.next
].prio
)
274 swap_list
.next
= p
- swap_info
;
283 * Caller has made sure that the swapdevice corresponding to entry
284 * is still around or has not been recycled.
286 void swap_free(swp_entry_t entry
)
288 struct swap_info_struct
* p
;
290 p
= swap_info_get(entry
);
292 swap_entry_free(p
, swp_offset(entry
));
298 * How many references to page are currently swapped out?
300 static inline int page_swapcount(struct page
*page
)
303 struct swap_info_struct
*p
;
306 entry
.val
= page
->private;
307 p
= swap_info_get(entry
);
309 /* Subtract the 1 for the swap cache itself */
310 count
= p
->swap_map
[swp_offset(entry
)] - 1;
317 * We can use this swap cache entry directly
318 * if there are no other references to it.
320 int can_share_swap_page(struct page
*page
)
324 BUG_ON(!PageLocked(page
));
325 count
= page_mapcount(page
);
326 if (count
<= 1 && PageSwapCache(page
))
327 count
+= page_swapcount(page
);
332 * Work out if there are any other processes sharing this
333 * swap cache page. Free it if you can. Return success.
335 int remove_exclusive_swap_page(struct page
*page
)
338 struct swap_info_struct
* p
;
341 BUG_ON(PagePrivate(page
));
342 BUG_ON(!PageLocked(page
));
344 if (!PageSwapCache(page
))
346 if (PageWriteback(page
))
348 if (page_count(page
) != 2) /* 2: us + cache */
351 entry
.val
= page
->private;
352 p
= swap_info_get(entry
);
356 /* Is the only swap cache user the cache itself? */
358 if (p
->swap_map
[swp_offset(entry
)] == 1) {
359 /* Recheck the page count with the swapcache lock held.. */
360 write_lock_irq(&swapper_space
.tree_lock
);
361 if ((page_count(page
) == 2) && !PageWriteback(page
)) {
362 __delete_from_swap_cache(page
);
366 write_unlock_irq(&swapper_space
.tree_lock
);
372 page_cache_release(page
);
379 * Free the swap entry like above, but also try to
380 * free the page cache entry if it is the last user.
382 void free_swap_and_cache(swp_entry_t entry
)
384 struct swap_info_struct
* p
;
385 struct page
*page
= NULL
;
387 p
= swap_info_get(entry
);
389 if (swap_entry_free(p
, swp_offset(entry
)) == 1)
390 page
= find_trylock_page(&swapper_space
, entry
.val
);
396 BUG_ON(PagePrivate(page
));
397 page_cache_get(page
);
398 one_user
= (page_count(page
) == 2);
399 /* Only cache user (+us), or swap space full? Free it! */
400 if (!PageWriteback(page
) && (one_user
|| vm_swap_full())) {
401 delete_from_swap_cache(page
);
405 page_cache_release(page
);
410 * Always set the resulting pte to be nowrite (the same as COW pages
411 * after one process has exited). We don't know just how many PTEs will
412 * share this swap entry, so be cautious and let do_wp_page work out
413 * what to do if a write is requested later.
415 * vma->vm_mm->page_table_lock is held.
417 static void unuse_pte(struct vm_area_struct
*vma
, pte_t
*pte
,
418 unsigned long addr
, swp_entry_t entry
, struct page
*page
)
420 inc_mm_counter(vma
->vm_mm
, rss
);
422 set_pte_at(vma
->vm_mm
, addr
, pte
,
423 pte_mkold(mk_pte(page
, vma
->vm_page_prot
)));
424 page_add_anon_rmap(page
, vma
, addr
);
427 * Move the page to the active list so it is not
428 * immediately swapped out again after swapon.
433 static int unuse_pte_range(struct vm_area_struct
*vma
, pmd_t
*pmd
,
434 unsigned long addr
, unsigned long end
,
435 swp_entry_t entry
, struct page
*page
)
438 pte_t swp_pte
= swp_entry_to_pte(entry
);
440 pte
= pte_offset_map(pmd
, addr
);
443 * swapoff spends a _lot_ of time in this loop!
444 * Test inline before going to call unuse_pte.
446 if (unlikely(pte_same(*pte
, swp_pte
))) {
447 unuse_pte(vma
, pte
, addr
, entry
, page
);
451 } while (pte
++, addr
+= PAGE_SIZE
, addr
!= end
);
456 static inline int unuse_pmd_range(struct vm_area_struct
*vma
, pud_t
*pud
,
457 unsigned long addr
, unsigned long end
,
458 swp_entry_t entry
, struct page
*page
)
463 pmd
= pmd_offset(pud
, addr
);
465 next
= pmd_addr_end(addr
, end
);
466 if (pmd_none_or_clear_bad(pmd
))
468 if (unuse_pte_range(vma
, pmd
, addr
, next
, entry
, page
))
470 } while (pmd
++, addr
= next
, addr
!= end
);
474 static inline int unuse_pud_range(struct vm_area_struct
*vma
, pgd_t
*pgd
,
475 unsigned long addr
, unsigned long end
,
476 swp_entry_t entry
, struct page
*page
)
481 pud
= pud_offset(pgd
, addr
);
483 next
= pud_addr_end(addr
, end
);
484 if (pud_none_or_clear_bad(pud
))
486 if (unuse_pmd_range(vma
, pud
, addr
, next
, entry
, page
))
488 } while (pud
++, addr
= next
, addr
!= end
);
492 static int unuse_vma(struct vm_area_struct
*vma
,
493 swp_entry_t entry
, struct page
*page
)
496 unsigned long addr
, end
, next
;
499 addr
= page_address_in_vma(page
, vma
);
503 end
= addr
+ PAGE_SIZE
;
505 addr
= vma
->vm_start
;
509 pgd
= pgd_offset(vma
->vm_mm
, addr
);
511 next
= pgd_addr_end(addr
, end
);
512 if (pgd_none_or_clear_bad(pgd
))
514 if (unuse_pud_range(vma
, pgd
, addr
, next
, entry
, page
))
516 } while (pgd
++, addr
= next
, addr
!= end
);
520 static int unuse_mm(struct mm_struct
*mm
,
521 swp_entry_t entry
, struct page
*page
)
523 struct vm_area_struct
*vma
;
525 if (!down_read_trylock(&mm
->mmap_sem
)) {
527 * Activate page so shrink_cache is unlikely to unmap its
528 * ptes while lock is dropped, so swapoff can make progress.
532 down_read(&mm
->mmap_sem
);
535 spin_lock(&mm
->page_table_lock
);
536 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
537 if (vma
->anon_vma
&& unuse_vma(vma
, entry
, page
))
540 spin_unlock(&mm
->page_table_lock
);
541 up_read(&mm
->mmap_sem
);
543 * Currently unuse_mm cannot fail, but leave error handling
544 * at call sites for now, since we change it from time to time.
550 * Scan swap_map from current position to next entry still in use.
551 * Recycle to start on reaching the end, returning 0 when empty.
553 static unsigned int find_next_to_unuse(struct swap_info_struct
*si
,
556 unsigned int max
= si
->max
;
557 unsigned int i
= prev
;
561 * No need for swap_device_lock(si) here: we're just looking
562 * for whether an entry is in use, not modifying it; false
563 * hits are okay, and sys_swapoff() has already prevented new
564 * allocations from this area (while holding swap_list_lock()).
573 * No entries in use at top of swap_map,
574 * loop back to start and recheck there.
580 count
= si
->swap_map
[i
];
581 if (count
&& count
!= SWAP_MAP_BAD
)
588 * We completely avoid races by reading each swap page in advance,
589 * and then search for the process using it. All the necessary
590 * page table adjustments can then be made atomically.
592 static int try_to_unuse(unsigned int type
)
594 struct swap_info_struct
* si
= &swap_info
[type
];
595 struct mm_struct
*start_mm
;
596 unsigned short *swap_map
;
597 unsigned short swcount
;
602 int reset_overflow
= 0;
606 * When searching mms for an entry, a good strategy is to
607 * start at the first mm we freed the previous entry from
608 * (though actually we don't notice whether we or coincidence
609 * freed the entry). Initialize this start_mm with a hold.
611 * A simpler strategy would be to start at the last mm we
612 * freed the previous entry from; but that would take less
613 * advantage of mmlist ordering, which clusters forked mms
614 * together, child after parent. If we race with dup_mmap(), we
615 * prefer to resolve parent before child, lest we miss entries
616 * duplicated after we scanned child: using last mm would invert
617 * that. Though it's only a serious concern when an overflowed
618 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
621 atomic_inc(&init_mm
.mm_users
);
624 * Keep on scanning until all entries have gone. Usually,
625 * one pass through swap_map is enough, but not necessarily:
626 * there are races when an instance of an entry might be missed.
628 while ((i
= find_next_to_unuse(si
, i
)) != 0) {
629 if (signal_pending(current
)) {
635 * Get a page for the entry, using the existing swap
636 * cache page if there is one. Otherwise, get a clean
637 * page and read the swap into it.
639 swap_map
= &si
->swap_map
[i
];
640 entry
= swp_entry(type
, i
);
641 page
= read_swap_cache_async(entry
, NULL
, 0);
644 * Either swap_duplicate() failed because entry
645 * has been freed independently, and will not be
646 * reused since sys_swapoff() already disabled
647 * allocation from here, or alloc_page() failed.
656 * Don't hold on to start_mm if it looks like exiting.
658 if (atomic_read(&start_mm
->mm_users
) == 1) {
661 atomic_inc(&init_mm
.mm_users
);
665 * Wait for and lock page. When do_swap_page races with
666 * try_to_unuse, do_swap_page can handle the fault much
667 * faster than try_to_unuse can locate the entry. This
668 * apparently redundant "wait_on_page_locked" lets try_to_unuse
669 * defer to do_swap_page in such a case - in some tests,
670 * do_swap_page and try_to_unuse repeatedly compete.
672 wait_on_page_locked(page
);
673 wait_on_page_writeback(page
);
675 wait_on_page_writeback(page
);
678 * Remove all references to entry.
679 * Whenever we reach init_mm, there's no address space
680 * to search, but use it as a reminder to search shmem.
685 if (start_mm
== &init_mm
)
686 shmem
= shmem_unuse(entry
, page
);
688 retval
= unuse_mm(start_mm
, entry
, page
);
691 int set_start_mm
= (*swap_map
>= swcount
);
692 struct list_head
*p
= &start_mm
->mmlist
;
693 struct mm_struct
*new_start_mm
= start_mm
;
694 struct mm_struct
*prev_mm
= start_mm
;
695 struct mm_struct
*mm
;
697 atomic_inc(&new_start_mm
->mm_users
);
698 atomic_inc(&prev_mm
->mm_users
);
699 spin_lock(&mmlist_lock
);
700 while (*swap_map
> 1 && !retval
&&
701 (p
= p
->next
) != &start_mm
->mmlist
) {
702 mm
= list_entry(p
, struct mm_struct
, mmlist
);
703 if (atomic_inc_return(&mm
->mm_users
) == 1) {
704 atomic_dec(&mm
->mm_users
);
707 spin_unlock(&mmlist_lock
);
716 else if (mm
== &init_mm
) {
718 shmem
= shmem_unuse(entry
, page
);
720 retval
= unuse_mm(mm
, entry
, page
);
721 if (set_start_mm
&& *swap_map
< swcount
) {
723 atomic_inc(&mm
->mm_users
);
727 spin_lock(&mmlist_lock
);
729 spin_unlock(&mmlist_lock
);
732 start_mm
= new_start_mm
;
736 page_cache_release(page
);
741 * How could swap count reach 0x7fff when the maximum
742 * pid is 0x7fff, and there's no way to repeat a swap
743 * page within an mm (except in shmem, where it's the
744 * shared object which takes the reference count)?
745 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
747 * If that's wrong, then we should worry more about
748 * exit_mmap() and do_munmap() cases described above:
749 * we might be resetting SWAP_MAP_MAX too early here.
750 * We know "Undead"s can happen, they're okay, so don't
751 * report them; but do report if we reset SWAP_MAP_MAX.
753 if (*swap_map
== SWAP_MAP_MAX
) {
754 swap_device_lock(si
);
756 swap_device_unlock(si
);
761 * If a reference remains (rare), we would like to leave
762 * the page in the swap cache; but try_to_unmap could
763 * then re-duplicate the entry once we drop page lock,
764 * so we might loop indefinitely; also, that page could
765 * not be swapped out to other storage meanwhile. So:
766 * delete from cache even if there's another reference,
767 * after ensuring that the data has been saved to disk -
768 * since if the reference remains (rarer), it will be
769 * read from disk into another page. Splitting into two
770 * pages would be incorrect if swap supported "shared
771 * private" pages, but they are handled by tmpfs files.
773 * Note shmem_unuse already deleted a swappage from
774 * the swap cache, unless the move to filepage failed:
775 * in which case it left swappage in cache, lowered its
776 * swap count to pass quickly through the loops above,
777 * and now we must reincrement count to try again later.
779 if ((*swap_map
> 1) && PageDirty(page
) && PageSwapCache(page
)) {
780 struct writeback_control wbc
= {
781 .sync_mode
= WB_SYNC_NONE
,
784 swap_writepage(page
, &wbc
);
786 wait_on_page_writeback(page
);
788 if (PageSwapCache(page
)) {
790 swap_duplicate(entry
);
792 delete_from_swap_cache(page
);
796 * So we could skip searching mms once swap count went
797 * to 1, we did not mark any present ptes as dirty: must
798 * mark page dirty so shrink_list will preserve it.
802 page_cache_release(page
);
805 * Make sure that we aren't completely killing
806 * interactive performance.
812 if (reset_overflow
) {
813 printk(KERN_WARNING
"swapoff: cleared swap entry overflow\n");
820 * After a successful try_to_unuse, if no swap is now in use, we know we
821 * can empty the mmlist. swap_list_lock must be held on entry and exit.
822 * Note that mmlist_lock nests inside swap_list_lock, and an mm must be
823 * added to the mmlist just after page_duplicate - before would be racy.
825 static void drain_mmlist(void)
827 struct list_head
*p
, *next
;
830 for (i
= 0; i
< nr_swapfiles
; i
++)
831 if (swap_info
[i
].inuse_pages
)
833 spin_lock(&mmlist_lock
);
834 list_for_each_safe(p
, next
, &init_mm
.mmlist
)
836 spin_unlock(&mmlist_lock
);
840 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
841 * corresponds to page offset `offset'.
843 sector_t
map_swap_page(struct swap_info_struct
*sis
, pgoff_t offset
)
845 struct swap_extent
*se
= sis
->curr_swap_extent
;
846 struct swap_extent
*start_se
= se
;
849 struct list_head
*lh
;
851 if (se
->start_page
<= offset
&&
852 offset
< (se
->start_page
+ se
->nr_pages
)) {
853 return se
->start_block
+ (offset
- se
->start_page
);
856 if (lh
== &sis
->extent_list
)
858 se
= list_entry(lh
, struct swap_extent
, list
);
859 sis
->curr_swap_extent
= se
;
860 BUG_ON(se
== start_se
); /* It *must* be present */
865 * Free all of a swapdev's extent information
867 static void destroy_swap_extents(struct swap_info_struct
*sis
)
869 while (!list_empty(&sis
->extent_list
)) {
870 struct swap_extent
*se
;
872 se
= list_entry(sis
->extent_list
.next
,
873 struct swap_extent
, list
);
880 * Add a block range (and the corresponding page range) into this swapdev's
881 * extent list. The extent list is kept sorted in page order.
883 * This function rather assumes that it is called in ascending page order.
886 add_swap_extent(struct swap_info_struct
*sis
, unsigned long start_page
,
887 unsigned long nr_pages
, sector_t start_block
)
889 struct swap_extent
*se
;
890 struct swap_extent
*new_se
;
891 struct list_head
*lh
;
893 lh
= sis
->extent_list
.prev
; /* The highest page extent */
894 if (lh
!= &sis
->extent_list
) {
895 se
= list_entry(lh
, struct swap_extent
, list
);
896 BUG_ON(se
->start_page
+ se
->nr_pages
!= start_page
);
897 if (se
->start_block
+ se
->nr_pages
== start_block
) {
899 se
->nr_pages
+= nr_pages
;
905 * No merge. Insert a new extent, preserving ordering.
907 new_se
= kmalloc(sizeof(*se
), GFP_KERNEL
);
910 new_se
->start_page
= start_page
;
911 new_se
->nr_pages
= nr_pages
;
912 new_se
->start_block
= start_block
;
914 list_add_tail(&new_se
->list
, &sis
->extent_list
);
919 * A `swap extent' is a simple thing which maps a contiguous range of pages
920 * onto a contiguous range of disk blocks. An ordered list of swap extents
921 * is built at swapon time and is then used at swap_writepage/swap_readpage
922 * time for locating where on disk a page belongs.
924 * If the swapfile is an S_ISBLK block device, a single extent is installed.
925 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
926 * swap files identically.
928 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
929 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
930 * swapfiles are handled *identically* after swapon time.
932 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
933 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
934 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
935 * requirements, they are simply tossed out - we will never use those blocks
938 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
939 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
940 * which will scribble on the fs.
942 * The amount of disk space which a single swap extent represents varies.
943 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
944 * extents in the list. To avoid much list walking, we cache the previous
945 * search location in `curr_swap_extent', and start new searches from there.
946 * This is extremely effective. The average number of iterations in
947 * map_swap_page() has been measured at about 0.3 per page. - akpm.
949 static int setup_swap_extents(struct swap_info_struct
*sis
, sector_t
*span
)
952 unsigned blocks_per_page
;
953 unsigned long page_no
;
955 sector_t probe_block
;
957 sector_t lowest_block
= -1;
958 sector_t highest_block
= 0;
962 inode
= sis
->swap_file
->f_mapping
->host
;
963 if (S_ISBLK(inode
->i_mode
)) {
964 ret
= add_swap_extent(sis
, 0, sis
->max
, 0);
969 blkbits
= inode
->i_blkbits
;
970 blocks_per_page
= PAGE_SIZE
>> blkbits
;
973 * Map all the blocks into the extent list. This code doesn't try
978 last_block
= i_size_read(inode
) >> blkbits
;
979 while ((probe_block
+ blocks_per_page
) <= last_block
&&
980 page_no
< sis
->max
) {
981 unsigned block_in_page
;
982 sector_t first_block
;
984 first_block
= bmap(inode
, probe_block
);
985 if (first_block
== 0)
989 * It must be PAGE_SIZE aligned on-disk
991 if (first_block
& (blocks_per_page
- 1)) {
996 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
1000 block
= bmap(inode
, probe_block
+ block_in_page
);
1003 if (block
!= first_block
+ block_in_page
) {
1010 first_block
>>= (PAGE_SHIFT
- blkbits
);
1011 if (page_no
) { /* exclude the header page */
1012 if (first_block
< lowest_block
)
1013 lowest_block
= first_block
;
1014 if (first_block
> highest_block
)
1015 highest_block
= first_block
;
1019 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1021 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
1026 probe_block
+= blocks_per_page
;
1031 *span
= 1 + highest_block
- lowest_block
;
1033 page_no
= 1; /* force Empty message */
1035 sis
->pages
= page_no
- 1;
1036 sis
->highest_bit
= page_no
- 1;
1038 sis
->curr_swap_extent
= list_entry(sis
->extent_list
.prev
,
1039 struct swap_extent
, list
);
1042 printk(KERN_ERR
"swapon: swapfile has holes\n");
1048 #if 0 /* We don't need this yet */
1049 #include <linux/backing-dev.h>
1050 int page_queue_congested(struct page
*page
)
1052 struct backing_dev_info
*bdi
;
1054 BUG_ON(!PageLocked(page
)); /* It pins the swap_info_struct */
1056 if (PageSwapCache(page
)) {
1057 swp_entry_t entry
= { .val
= page
->private };
1058 struct swap_info_struct
*sis
;
1060 sis
= get_swap_info_struct(swp_type(entry
));
1061 bdi
= sis
->bdev
->bd_inode
->i_mapping
->backing_dev_info
;
1063 bdi
= page
->mapping
->backing_dev_info
;
1064 return bdi_write_congested(bdi
);
1068 asmlinkage
long sys_swapoff(const char __user
* specialfile
)
1070 struct swap_info_struct
* p
= NULL
;
1071 unsigned short *swap_map
;
1072 struct file
*swap_file
, *victim
;
1073 struct address_space
*mapping
;
1074 struct inode
*inode
;
1079 if (!capable(CAP_SYS_ADMIN
))
1082 pathname
= getname(specialfile
);
1083 err
= PTR_ERR(pathname
);
1084 if (IS_ERR(pathname
))
1087 victim
= filp_open(pathname
, O_RDWR
|O_LARGEFILE
, 0);
1089 err
= PTR_ERR(victim
);
1093 mapping
= victim
->f_mapping
;
1096 for (type
= swap_list
.head
; type
>= 0; type
= swap_info
[type
].next
) {
1097 p
= swap_info
+ type
;
1098 if ((p
->flags
& SWP_ACTIVE
) == SWP_ACTIVE
) {
1099 if (p
->swap_file
->f_mapping
== mapping
)
1109 if (!security_vm_enough_memory(p
->pages
))
1110 vm_unacct_memory(p
->pages
);
1117 swap_list
.head
= p
->next
;
1119 swap_info
[prev
].next
= p
->next
;
1121 if (type
== swap_list
.next
) {
1122 /* just pick something that's safe... */
1123 swap_list
.next
= swap_list
.head
;
1125 nr_swap_pages
-= p
->pages
;
1126 total_swap_pages
-= p
->pages
;
1127 swap_device_lock(p
);
1128 p
->flags
&= ~SWP_WRITEOK
;
1129 swap_device_unlock(p
);
1132 current
->flags
|= PF_SWAPOFF
;
1133 err
= try_to_unuse(type
);
1134 current
->flags
&= ~PF_SWAPOFF
;
1137 /* re-insert swap space back into swap_list */
1139 for (prev
= -1, i
= swap_list
.head
; i
>= 0; prev
= i
, i
= swap_info
[i
].next
)
1140 if (p
->prio
>= swap_info
[i
].prio
)
1144 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1146 swap_info
[prev
].next
= p
- swap_info
;
1147 nr_swap_pages
+= p
->pages
;
1148 total_swap_pages
+= p
->pages
;
1149 swap_device_lock(p
);
1150 p
->flags
|= SWP_WRITEOK
;
1151 swap_device_unlock(p
);
1156 /* wait for any unplug function to finish */
1157 down_write(&swap_unplug_sem
);
1158 up_write(&swap_unplug_sem
);
1160 /* wait for anyone still in scan_swap_map */
1161 swap_device_lock(p
);
1162 p
->highest_bit
= 0; /* cuts scans short */
1163 while (p
->flags
>= SWP_SCANNING
) {
1164 swap_device_unlock(p
);
1165 set_current_state(TASK_UNINTERRUPTIBLE
);
1166 schedule_timeout(1);
1167 swap_device_lock(p
);
1169 swap_device_unlock(p
);
1171 destroy_swap_extents(p
);
1175 swap_device_lock(p
);
1176 swap_file
= p
->swap_file
;
1177 p
->swap_file
= NULL
;
1179 swap_map
= p
->swap_map
;
1182 swap_device_unlock(p
);
1186 inode
= mapping
->host
;
1187 if (S_ISBLK(inode
->i_mode
)) {
1188 struct block_device
*bdev
= I_BDEV(inode
);
1189 set_blocksize(bdev
, p
->old_block_size
);
1192 down(&inode
->i_sem
);
1193 inode
->i_flags
&= ~S_SWAPFILE
;
1196 filp_close(swap_file
, NULL
);
1200 filp_close(victim
, NULL
);
1205 #ifdef CONFIG_PROC_FS
1207 static void *swap_start(struct seq_file
*swap
, loff_t
*pos
)
1209 struct swap_info_struct
*ptr
= swap_info
;
1215 for (i
= 0; i
< nr_swapfiles
; i
++, ptr
++) {
1216 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1225 static void *swap_next(struct seq_file
*swap
, void *v
, loff_t
*pos
)
1227 struct swap_info_struct
*ptr
= v
;
1228 struct swap_info_struct
*endptr
= swap_info
+ nr_swapfiles
;
1230 for (++ptr
; ptr
< endptr
; ptr
++) {
1231 if (!(ptr
->flags
& SWP_USED
) || !ptr
->swap_map
)
1240 static void swap_stop(struct seq_file
*swap
, void *v
)
1245 static int swap_show(struct seq_file
*swap
, void *v
)
1247 struct swap_info_struct
*ptr
= v
;
1252 seq_puts(swap
, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1254 file
= ptr
->swap_file
;
1255 len
= seq_path(swap
, file
->f_vfsmnt
, file
->f_dentry
, " \t\n\\");
1256 seq_printf(swap
, "%*s%s\t%u\t%u\t%d\n",
1257 len
< 40 ? 40 - len
: 1, " ",
1258 S_ISBLK(file
->f_dentry
->d_inode
->i_mode
) ?
1259 "partition" : "file\t",
1260 ptr
->pages
<< (PAGE_SHIFT
- 10),
1261 ptr
->inuse_pages
<< (PAGE_SHIFT
- 10),
1266 static struct seq_operations swaps_op
= {
1267 .start
= swap_start
,
1273 static int swaps_open(struct inode
*inode
, struct file
*file
)
1275 return seq_open(file
, &swaps_op
);
1278 static struct file_operations proc_swaps_operations
= {
1281 .llseek
= seq_lseek
,
1282 .release
= seq_release
,
1285 static int __init
procswaps_init(void)
1287 struct proc_dir_entry
*entry
;
1289 entry
= create_proc_entry("swaps", 0, NULL
);
1291 entry
->proc_fops
= &proc_swaps_operations
;
1294 __initcall(procswaps_init
);
1295 #endif /* CONFIG_PROC_FS */
1298 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1300 * The swapon system call
1302 asmlinkage
long sys_swapon(const char __user
* specialfile
, int swap_flags
)
1304 struct swap_info_struct
* p
;
1306 struct block_device
*bdev
= NULL
;
1307 struct file
*swap_file
= NULL
;
1308 struct address_space
*mapping
;
1312 static int least_priority
;
1313 union swap_header
*swap_header
= NULL
;
1314 int swap_header_version
;
1315 unsigned int nr_good_pages
= 0;
1318 unsigned long maxpages
= 1;
1320 unsigned short *swap_map
;
1321 struct page
*page
= NULL
;
1322 struct inode
*inode
= NULL
;
1325 if (!capable(CAP_SYS_ADMIN
))
1329 for (type
= 0 ; type
< nr_swapfiles
; type
++,p
++)
1330 if (!(p
->flags
& SWP_USED
))
1334 * Test if adding another swap device is possible. There are
1335 * two limiting factors: 1) the number of bits for the swap
1336 * type swp_entry_t definition and 2) the number of bits for
1337 * the swap type in the swap ptes as defined by the different
1338 * architectures. To honor both limitations a swap entry
1339 * with swap offset 0 and swap type ~0UL is created, encoded
1340 * to a swap pte, decoded to a swp_entry_t again and finally
1341 * the swap type part is extracted. This will mask all bits
1342 * from the initial ~0UL that can't be encoded in either the
1343 * swp_entry_t or the architecture definition of a swap pte.
1345 if (type
> swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1349 if (type
>= nr_swapfiles
)
1350 nr_swapfiles
= type
+1;
1351 INIT_LIST_HEAD(&p
->extent_list
);
1352 p
->flags
= SWP_USED
;
1353 p
->swap_file
= NULL
;
1354 p
->old_block_size
= 0;
1360 spin_lock_init(&p
->sdev_lock
);
1362 if (swap_flags
& SWAP_FLAG_PREFER
) {
1364 (swap_flags
& SWAP_FLAG_PRIO_MASK
)>>SWAP_FLAG_PRIO_SHIFT
;
1366 p
->prio
= --least_priority
;
1369 name
= getname(specialfile
);
1370 error
= PTR_ERR(name
);
1375 swap_file
= filp_open(name
, O_RDWR
|O_LARGEFILE
, 0);
1376 error
= PTR_ERR(swap_file
);
1377 if (IS_ERR(swap_file
)) {
1382 p
->swap_file
= swap_file
;
1383 mapping
= swap_file
->f_mapping
;
1384 inode
= mapping
->host
;
1387 for (i
= 0; i
< nr_swapfiles
; i
++) {
1388 struct swap_info_struct
*q
= &swap_info
[i
];
1390 if (i
== type
|| !q
->swap_file
)
1392 if (mapping
== q
->swap_file
->f_mapping
)
1397 if (S_ISBLK(inode
->i_mode
)) {
1398 bdev
= I_BDEV(inode
);
1399 error
= bd_claim(bdev
, sys_swapon
);
1404 p
->old_block_size
= block_size(bdev
);
1405 error
= set_blocksize(bdev
, PAGE_SIZE
);
1409 } else if (S_ISREG(inode
->i_mode
)) {
1410 p
->bdev
= inode
->i_sb
->s_bdev
;
1411 down(&inode
->i_sem
);
1413 if (IS_SWAPFILE(inode
)) {
1421 swapfilesize
= i_size_read(inode
) >> PAGE_SHIFT
;
1424 * Read the swap header.
1426 if (!mapping
->a_ops
->readpage
) {
1430 page
= read_cache_page(mapping
, 0,
1431 (filler_t
*)mapping
->a_ops
->readpage
, swap_file
);
1433 error
= PTR_ERR(page
);
1436 wait_on_page_locked(page
);
1437 if (!PageUptodate(page
))
1440 swap_header
= page_address(page
);
1442 if (!memcmp("SWAP-SPACE",swap_header
->magic
.magic
,10))
1443 swap_header_version
= 1;
1444 else if (!memcmp("SWAPSPACE2",swap_header
->magic
.magic
,10))
1445 swap_header_version
= 2;
1447 printk("Unable to find swap-space signature\n");
1452 switch (swap_header_version
) {
1454 printk(KERN_ERR
"version 0 swap is no longer supported. "
1455 "Use mkswap -v1 %s\n", name
);
1459 /* Check the swap header's sub-version and the size of
1460 the swap file and bad block lists */
1461 if (swap_header
->info
.version
!= 1) {
1463 "Unable to handle swap header version %d\n",
1464 swap_header
->info
.version
);
1470 p
->cluster_next
= 1;
1473 * Find out how many pages are allowed for a single swap
1474 * device. There are two limiting factors: 1) the number of
1475 * bits for the swap offset in the swp_entry_t type and
1476 * 2) the number of bits in the a swap pte as defined by
1477 * the different architectures. In order to find the
1478 * largest possible bit mask a swap entry with swap type 0
1479 * and swap offset ~0UL is created, encoded to a swap pte,
1480 * decoded to a swp_entry_t again and finally the swap
1481 * offset is extracted. This will mask all the bits from
1482 * the initial ~0UL mask that can't be encoded in either
1483 * the swp_entry_t or the architecture definition of a
1486 maxpages
= swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1487 if (maxpages
> swap_header
->info
.last_page
)
1488 maxpages
= swap_header
->info
.last_page
;
1489 p
->highest_bit
= maxpages
- 1;
1494 if (swap_header
->info
.nr_badpages
&& S_ISREG(inode
->i_mode
))
1496 if (swap_header
->info
.nr_badpages
> MAX_SWAP_BADPAGES
)
1499 /* OK, set up the swap map and apply the bad block list */
1500 if (!(p
->swap_map
= vmalloc(maxpages
* sizeof(short)))) {
1506 memset(p
->swap_map
, 0, maxpages
* sizeof(short));
1507 for (i
=0; i
<swap_header
->info
.nr_badpages
; i
++) {
1508 int page
= swap_header
->info
.badpages
[i
];
1509 if (page
<= 0 || page
>= swap_header
->info
.last_page
)
1512 p
->swap_map
[page
] = SWAP_MAP_BAD
;
1514 nr_good_pages
= swap_header
->info
.last_page
-
1515 swap_header
->info
.nr_badpages
-
1516 1 /* header page */;
1521 if (swapfilesize
&& maxpages
> swapfilesize
) {
1523 "Swap area shorter than signature indicates\n");
1527 if (nr_good_pages
) {
1528 p
->swap_map
[0] = SWAP_MAP_BAD
;
1530 p
->pages
= nr_good_pages
;
1531 nr_extents
= setup_swap_extents(p
, &span
);
1532 if (nr_extents
< 0) {
1536 nr_good_pages
= p
->pages
;
1538 if (!nr_good_pages
) {
1539 printk(KERN_WARNING
"Empty swap-file\n");
1546 swap_device_lock(p
);
1547 p
->flags
= SWP_ACTIVE
;
1548 nr_swap_pages
+= nr_good_pages
;
1549 total_swap_pages
+= nr_good_pages
;
1551 printk(KERN_INFO
"Adding %uk swap on %s. "
1552 "Priority:%d extents:%d across:%lluk\n",
1553 nr_good_pages
<<(PAGE_SHIFT
-10), name
, p
->prio
,
1554 nr_extents
, (unsigned long long)span
<<(PAGE_SHIFT
-10));
1556 /* insert swap space into swap_list: */
1558 for (i
= swap_list
.head
; i
>= 0; i
= swap_info
[i
].next
) {
1559 if (p
->prio
>= swap_info
[i
].prio
) {
1566 swap_list
.head
= swap_list
.next
= p
- swap_info
;
1568 swap_info
[prev
].next
= p
- swap_info
;
1570 swap_device_unlock(p
);
1577 set_blocksize(bdev
, p
->old_block_size
);
1580 destroy_swap_extents(p
);
1583 swap_map
= p
->swap_map
;
1584 p
->swap_file
= NULL
;
1587 if (!(swap_flags
& SWAP_FLAG_PREFER
))
1592 filp_close(swap_file
, NULL
);
1594 if (page
&& !IS_ERR(page
)) {
1596 page_cache_release(page
);
1602 inode
->i_flags
|= S_SWAPFILE
;
1608 void si_swapinfo(struct sysinfo
*val
)
1611 unsigned long nr_to_be_unused
= 0;
1614 for (i
= 0; i
< nr_swapfiles
; i
++) {
1615 if (!(swap_info
[i
].flags
& SWP_USED
) ||
1616 (swap_info
[i
].flags
& SWP_WRITEOK
))
1618 nr_to_be_unused
+= swap_info
[i
].inuse_pages
;
1620 val
->freeswap
= nr_swap_pages
+ nr_to_be_unused
;
1621 val
->totalswap
= total_swap_pages
+ nr_to_be_unused
;
1626 * Verify that a swap entry is valid and increment its swap map count.
1628 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1629 * "permanent", but will be reclaimed by the next swapoff.
1631 int swap_duplicate(swp_entry_t entry
)
1633 struct swap_info_struct
* p
;
1634 unsigned long offset
, type
;
1637 type
= swp_type(entry
);
1638 if (type
>= nr_swapfiles
)
1640 p
= type
+ swap_info
;
1641 offset
= swp_offset(entry
);
1643 swap_device_lock(p
);
1644 if (offset
< p
->max
&& p
->swap_map
[offset
]) {
1645 if (p
->swap_map
[offset
] < SWAP_MAP_MAX
- 1) {
1646 p
->swap_map
[offset
]++;
1648 } else if (p
->swap_map
[offset
] <= SWAP_MAP_MAX
) {
1649 if (swap_overflow
++ < 5)
1650 printk(KERN_WARNING
"swap_dup: swap entry overflow\n");
1651 p
->swap_map
[offset
] = SWAP_MAP_MAX
;
1655 swap_device_unlock(p
);
1660 printk(KERN_ERR
"swap_dup: %s%08lx\n", Bad_file
, entry
.val
);
1664 struct swap_info_struct
*
1665 get_swap_info_struct(unsigned type
)
1667 return &swap_info
[type
];
1671 * swap_device_lock prevents swap_map being freed. Don't grab an extra
1672 * reference on the swaphandle, it doesn't matter if it becomes unused.
1674 int valid_swaphandles(swp_entry_t entry
, unsigned long *offset
)
1676 int ret
= 0, i
= 1 << page_cluster
;
1678 struct swap_info_struct
*swapdev
= swp_type(entry
) + swap_info
;
1680 if (!page_cluster
) /* no readahead */
1682 toff
= (swp_offset(entry
) >> page_cluster
) << page_cluster
;
1683 if (!toff
) /* first page is swap header */
1687 swap_device_lock(swapdev
);
1689 /* Don't read-ahead past the end of the swap area */
1690 if (toff
>= swapdev
->max
)
1692 /* Don't read in free or bad pages */
1693 if (!swapdev
->swap_map
[toff
])
1695 if (swapdev
->swap_map
[toff
] == SWAP_MAP_BAD
)
1700 swap_device_unlock(swapdev
);