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/random.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/ksm.h>
26 #include <linux/rmap.h>
27 #include <linux/security.h>
28 #include <linux/backing-dev.h>
29 #include <linux/mutex.h>
30 #include <linux/capability.h>
31 #include <linux/syscalls.h>
32 #include <linux/memcontrol.h>
33 #include <linux/poll.h>
35 #include <asm/pgtable.h>
36 #include <asm/tlbflush.h>
37 #include <linux/swapops.h>
38 #include <linux/page_cgroup.h>
40 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
42 static void free_swap_count_continuations(struct swap_info_struct *);
43 static sector_t map_swap_entry(swp_entry_t, struct block_device**);
45 static DEFINE_SPINLOCK(swap_lock);
46 static unsigned int nr_swapfiles;
48 long total_swap_pages;
49 static int least_priority;
51 static const char Bad_file[] = "Bad swap file entry ";
52 static const char Unused_file[] = "Unused swap file entry ";
53 static const char Bad_offset[] = "Bad swap offset entry ";
54 static const char Unused_offset[] = "Unused swap offset entry ";
56 static struct swap_list_t swap_list = {-1, -1};
58 static struct swap_info_struct *swap_info[MAX_SWAPFILES];
60 static DEFINE_MUTEX(swapon_mutex);
62 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
63 /* Activity counter to indicate that a swapon or swapoff has occurred */
64 static atomic_t proc_poll_event = ATOMIC_INIT(0);
66 static inline unsigned char swap_count(unsigned char ent)
68 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
71 /* returns 1 if swap entry is freed */
73 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
75 swp_entry_t entry = swp_entry(si->type, offset);
79 page = find_get_page(&swapper_space, entry.val);
83 * This function is called from scan_swap_map() and it's called
84 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
85 * We have to use trylock for avoiding deadlock. This is a special
86 * case and you should use try_to_free_swap() with explicit lock_page()
87 * in usual operations.
89 if (trylock_page(page)) {
90 ret = try_to_free_swap(page);
93 page_cache_release(page);
98 * We need this because the bdev->unplug_fn can sleep and we cannot
99 * hold swap_lock while calling the unplug_fn. And swap_lock
100 * cannot be turned into a mutex.
102 static DECLARE_RWSEM(swap_unplug_sem);
104 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
108 down_read(&swap_unplug_sem);
109 entry.val = page_private(page);
110 if (PageSwapCache(page)) {
111 struct block_device *bdev = swap_info[swp_type(entry)]->bdev;
112 struct backing_dev_info *bdi;
115 * If the page is removed from swapcache from under us (with a
116 * racy try_to_unuse/swapoff) we need an additional reference
117 * count to avoid reading garbage from page_private(page) above.
118 * If the WARN_ON triggers during a swapoff it maybe the race
119 * condition and it's harmless. However if it triggers without
120 * swapoff it signals a problem.
122 WARN_ON(page_count(page) <= 1);
124 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
125 blk_run_backing_dev(bdi, page);
127 up_read(&swap_unplug_sem);
131 * swapon tell device that all the old swap contents can be discarded,
132 * to allow the swap device to optimize its wear-levelling.
134 static int discard_swap(struct swap_info_struct *si)
136 struct swap_extent *se;
137 sector_t start_block;
141 /* Do not discard the swap header page! */
142 se = &si->first_swap_extent;
143 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
144 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
146 err = blkdev_issue_discard(si->bdev, start_block,
147 nr_blocks, GFP_KERNEL, 0);
153 list_for_each_entry(se, &si->first_swap_extent.list, list) {
154 start_block = se->start_block << (PAGE_SHIFT - 9);
155 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
157 err = blkdev_issue_discard(si->bdev, start_block,
158 nr_blocks, GFP_KERNEL, 0);
164 return err; /* That will often be -EOPNOTSUPP */
168 * swap allocation tell device that a cluster of swap can now be discarded,
169 * to allow the swap device to optimize its wear-levelling.
171 static void discard_swap_cluster(struct swap_info_struct *si,
172 pgoff_t start_page, pgoff_t nr_pages)
174 struct swap_extent *se = si->curr_swap_extent;
175 int found_extent = 0;
178 struct list_head *lh;
180 if (se->start_page <= start_page &&
181 start_page < se->start_page + se->nr_pages) {
182 pgoff_t offset = start_page - se->start_page;
183 sector_t start_block = se->start_block + offset;
184 sector_t nr_blocks = se->nr_pages - offset;
186 if (nr_blocks > nr_pages)
187 nr_blocks = nr_pages;
188 start_page += nr_blocks;
189 nr_pages -= nr_blocks;
192 si->curr_swap_extent = se;
194 start_block <<= PAGE_SHIFT - 9;
195 nr_blocks <<= PAGE_SHIFT - 9;
196 if (blkdev_issue_discard(si->bdev, start_block,
197 nr_blocks, GFP_NOIO, 0))
202 se = list_entry(lh, struct swap_extent, list);
206 static int wait_for_discard(void *word)
212 #define SWAPFILE_CLUSTER 256
213 #define LATENCY_LIMIT 256
215 static inline unsigned long scan_swap_map(struct swap_info_struct *si,
218 unsigned long offset;
219 unsigned long scan_base;
220 unsigned long last_in_cluster = 0;
221 int latency_ration = LATENCY_LIMIT;
222 int found_free_cluster = 0;
225 * We try to cluster swap pages by allocating them sequentially
226 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
227 * way, however, we resort to first-free allocation, starting
228 * a new cluster. This prevents us from scattering swap pages
229 * all over the entire swap partition, so that we reduce
230 * overall disk seek times between swap pages. -- sct
231 * But we do now try to find an empty cluster. -Andrea
232 * And we let swap pages go all over an SSD partition. Hugh
235 si->flags += SWP_SCANNING;
236 scan_base = offset = si->cluster_next;
238 if (unlikely(!si->cluster_nr--)) {
239 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
240 si->cluster_nr = SWAPFILE_CLUSTER - 1;
243 if (si->flags & SWP_DISCARDABLE) {
245 * Start range check on racing allocations, in case
246 * they overlap the cluster we eventually decide on
247 * (we scan without swap_lock to allow preemption).
248 * It's hardly conceivable that cluster_nr could be
249 * wrapped during our scan, but don't depend on it.
251 if (si->lowest_alloc)
253 si->lowest_alloc = si->max;
254 si->highest_alloc = 0;
256 spin_unlock(&swap_lock);
259 * If seek is expensive, start searching for new cluster from
260 * start of partition, to minimize the span of allocated swap.
261 * But if seek is cheap, search from our current position, so
262 * that swap is allocated from all over the partition: if the
263 * Flash Translation Layer only remaps within limited zones,
264 * we don't want to wear out the first zone too quickly.
266 if (!(si->flags & SWP_SOLIDSTATE))
267 scan_base = offset = si->lowest_bit;
268 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
270 /* Locate the first empty (unaligned) cluster */
271 for (; last_in_cluster <= si->highest_bit; offset++) {
272 if (si->swap_map[offset])
273 last_in_cluster = offset + SWAPFILE_CLUSTER;
274 else if (offset == last_in_cluster) {
275 spin_lock(&swap_lock);
276 offset -= SWAPFILE_CLUSTER - 1;
277 si->cluster_next = offset;
278 si->cluster_nr = SWAPFILE_CLUSTER - 1;
279 found_free_cluster = 1;
282 if (unlikely(--latency_ration < 0)) {
284 latency_ration = LATENCY_LIMIT;
288 offset = si->lowest_bit;
289 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
291 /* Locate the first empty (unaligned) cluster */
292 for (; last_in_cluster < scan_base; offset++) {
293 if (si->swap_map[offset])
294 last_in_cluster = offset + SWAPFILE_CLUSTER;
295 else if (offset == last_in_cluster) {
296 spin_lock(&swap_lock);
297 offset -= SWAPFILE_CLUSTER - 1;
298 si->cluster_next = offset;
299 si->cluster_nr = SWAPFILE_CLUSTER - 1;
300 found_free_cluster = 1;
303 if (unlikely(--latency_ration < 0)) {
305 latency_ration = LATENCY_LIMIT;
310 spin_lock(&swap_lock);
311 si->cluster_nr = SWAPFILE_CLUSTER - 1;
312 si->lowest_alloc = 0;
316 if (!(si->flags & SWP_WRITEOK))
318 if (!si->highest_bit)
320 if (offset > si->highest_bit)
321 scan_base = offset = si->lowest_bit;
323 /* reuse swap entry of cache-only swap if not busy. */
324 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
326 spin_unlock(&swap_lock);
327 swap_was_freed = __try_to_reclaim_swap(si, offset);
328 spin_lock(&swap_lock);
329 /* entry was freed successfully, try to use this again */
332 goto scan; /* check next one */
335 if (si->swap_map[offset])
338 if (offset == si->lowest_bit)
340 if (offset == si->highest_bit)
343 if (si->inuse_pages == si->pages) {
344 si->lowest_bit = si->max;
347 si->swap_map[offset] = usage;
348 si->cluster_next = offset + 1;
349 si->flags -= SWP_SCANNING;
351 if (si->lowest_alloc) {
353 * Only set when SWP_DISCARDABLE, and there's a scan
354 * for a free cluster in progress or just completed.
356 if (found_free_cluster) {
358 * To optimize wear-levelling, discard the
359 * old data of the cluster, taking care not to
360 * discard any of its pages that have already
361 * been allocated by racing tasks (offset has
362 * already stepped over any at the beginning).
364 if (offset < si->highest_alloc &&
365 si->lowest_alloc <= last_in_cluster)
366 last_in_cluster = si->lowest_alloc - 1;
367 si->flags |= SWP_DISCARDING;
368 spin_unlock(&swap_lock);
370 if (offset < last_in_cluster)
371 discard_swap_cluster(si, offset,
372 last_in_cluster - offset + 1);
374 spin_lock(&swap_lock);
375 si->lowest_alloc = 0;
376 si->flags &= ~SWP_DISCARDING;
378 smp_mb(); /* wake_up_bit advises this */
379 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
381 } else if (si->flags & SWP_DISCARDING) {
383 * Delay using pages allocated by racing tasks
384 * until the whole discard has been issued. We
385 * could defer that delay until swap_writepage,
386 * but it's easier to keep this self-contained.
388 spin_unlock(&swap_lock);
389 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
390 wait_for_discard, TASK_UNINTERRUPTIBLE);
391 spin_lock(&swap_lock);
394 * Note pages allocated by racing tasks while
395 * scan for a free cluster is in progress, so
396 * that its final discard can exclude them.
398 if (offset < si->lowest_alloc)
399 si->lowest_alloc = offset;
400 if (offset > si->highest_alloc)
401 si->highest_alloc = offset;
407 spin_unlock(&swap_lock);
408 while (++offset <= si->highest_bit) {
409 if (!si->swap_map[offset]) {
410 spin_lock(&swap_lock);
413 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
414 spin_lock(&swap_lock);
417 if (unlikely(--latency_ration < 0)) {
419 latency_ration = LATENCY_LIMIT;
422 offset = si->lowest_bit;
423 while (++offset < scan_base) {
424 if (!si->swap_map[offset]) {
425 spin_lock(&swap_lock);
428 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
429 spin_lock(&swap_lock);
432 if (unlikely(--latency_ration < 0)) {
434 latency_ration = LATENCY_LIMIT;
437 spin_lock(&swap_lock);
440 si->flags -= SWP_SCANNING;
444 swp_entry_t get_swap_page(void)
446 struct swap_info_struct *si;
451 spin_lock(&swap_lock);
452 if (nr_swap_pages <= 0)
456 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
457 si = swap_info[type];
460 (!wrapped && si->prio != swap_info[next]->prio)) {
461 next = swap_list.head;
465 if (!si->highest_bit)
467 if (!(si->flags & SWP_WRITEOK))
470 swap_list.next = next;
471 /* This is called for allocating swap entry for cache */
472 offset = scan_swap_map(si, SWAP_HAS_CACHE);
474 spin_unlock(&swap_lock);
475 return swp_entry(type, offset);
477 next = swap_list.next;
482 spin_unlock(&swap_lock);
483 return (swp_entry_t) {0};
486 /* The only caller of this function is now susupend routine */
487 swp_entry_t get_swap_page_of_type(int type)
489 struct swap_info_struct *si;
492 spin_lock(&swap_lock);
493 si = swap_info[type];
494 if (si && (si->flags & SWP_WRITEOK)) {
496 /* This is called for allocating swap entry, not cache */
497 offset = scan_swap_map(si, 1);
499 spin_unlock(&swap_lock);
500 return swp_entry(type, offset);
504 spin_unlock(&swap_lock);
505 return (swp_entry_t) {0};
508 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
510 struct swap_info_struct *p;
511 unsigned long offset, type;
515 type = swp_type(entry);
516 if (type >= nr_swapfiles)
519 if (!(p->flags & SWP_USED))
521 offset = swp_offset(entry);
522 if (offset >= p->max)
524 if (!p->swap_map[offset])
526 spin_lock(&swap_lock);
530 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
533 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
536 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
539 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
544 static unsigned char swap_entry_free(struct swap_info_struct *p,
545 swp_entry_t entry, unsigned char usage)
547 unsigned long offset = swp_offset(entry);
549 unsigned char has_cache;
551 count = p->swap_map[offset];
552 has_cache = count & SWAP_HAS_CACHE;
553 count &= ~SWAP_HAS_CACHE;
555 if (usage == SWAP_HAS_CACHE) {
556 VM_BUG_ON(!has_cache);
558 } else if (count == SWAP_MAP_SHMEM) {
560 * Or we could insist on shmem.c using a special
561 * swap_shmem_free() and free_shmem_swap_and_cache()...
564 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
565 if (count == COUNT_CONTINUED) {
566 if (swap_count_continued(p, offset, count))
567 count = SWAP_MAP_MAX | COUNT_CONTINUED;
569 count = SWAP_MAP_MAX;
575 mem_cgroup_uncharge_swap(entry);
577 usage = count | has_cache;
578 p->swap_map[offset] = usage;
580 /* free if no reference */
582 struct gendisk *disk = p->bdev->bd_disk;
583 if (offset < p->lowest_bit)
584 p->lowest_bit = offset;
585 if (offset > p->highest_bit)
586 p->highest_bit = offset;
587 if (swap_list.next >= 0 &&
588 p->prio > swap_info[swap_list.next]->prio)
589 swap_list.next = p->type;
592 if ((p->flags & SWP_BLKDEV) &&
593 disk->fops->swap_slot_free_notify)
594 disk->fops->swap_slot_free_notify(p->bdev, offset);
601 * Caller has made sure that the swapdevice corresponding to entry
602 * is still around or has not been recycled.
604 void swap_free(swp_entry_t entry)
606 struct swap_info_struct *p;
608 p = swap_info_get(entry);
610 swap_entry_free(p, entry, 1);
611 spin_unlock(&swap_lock);
616 * Called after dropping swapcache to decrease refcnt to swap entries.
618 void swapcache_free(swp_entry_t entry, struct page *page)
620 struct swap_info_struct *p;
623 p = swap_info_get(entry);
625 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
627 mem_cgroup_uncharge_swapcache(page, entry, count != 0);
628 spin_unlock(&swap_lock);
633 * How many references to page are currently swapped out?
634 * This does not give an exact answer when swap count is continued,
635 * but does include the high COUNT_CONTINUED flag to allow for that.
637 static inline int page_swapcount(struct page *page)
640 struct swap_info_struct *p;
643 entry.val = page_private(page);
644 p = swap_info_get(entry);
646 count = swap_count(p->swap_map[swp_offset(entry)]);
647 spin_unlock(&swap_lock);
653 * We can write to an anon page without COW if there are no other references
654 * to it. And as a side-effect, free up its swap: because the old content
655 * on disk will never be read, and seeking back there to write new content
656 * later would only waste time away from clustering.
658 int reuse_swap_page(struct page *page)
662 VM_BUG_ON(!PageLocked(page));
663 if (unlikely(PageKsm(page)))
665 count = page_mapcount(page);
666 if (count <= 1 && PageSwapCache(page)) {
667 count += page_swapcount(page);
668 if (count == 1 && !PageWriteback(page)) {
669 delete_from_swap_cache(page);
677 * If swap is getting full, or if there are no more mappings of this page,
678 * then try_to_free_swap is called to free its swap space.
680 int try_to_free_swap(struct page *page)
682 VM_BUG_ON(!PageLocked(page));
684 if (!PageSwapCache(page))
686 if (PageWriteback(page))
688 if (page_swapcount(page))
692 * Once hibernation has begun to create its image of memory,
693 * there's a danger that one of the calls to try_to_free_swap()
694 * - most probably a call from __try_to_reclaim_swap() while
695 * hibernation is allocating its own swap pages for the image,
696 * but conceivably even a call from memory reclaim - will free
697 * the swap from a page which has already been recorded in the
698 * image as a clean swapcache page, and then reuse its swap for
699 * another page of the image. On waking from hibernation, the
700 * original page might be freed under memory pressure, then
701 * later read back in from swap, now with the wrong data.
703 * Hibernation clears bits from gfp_allowed_mask to prevent
704 * memory reclaim from writing to disk, so check that here.
706 if (!(gfp_allowed_mask & __GFP_IO))
709 delete_from_swap_cache(page);
715 * Free the swap entry like above, but also try to
716 * free the page cache entry if it is the last user.
718 int free_swap_and_cache(swp_entry_t entry)
720 struct swap_info_struct *p;
721 struct page *page = NULL;
723 if (non_swap_entry(entry))
726 p = swap_info_get(entry);
728 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
729 page = find_get_page(&swapper_space, entry.val);
730 if (page && !trylock_page(page)) {
731 page_cache_release(page);
735 spin_unlock(&swap_lock);
739 * Not mapped elsewhere, or swap space full? Free it!
740 * Also recheck PageSwapCache now page is locked (above).
742 if (PageSwapCache(page) && !PageWriteback(page) &&
743 (!page_mapped(page) || vm_swap_full())) {
744 delete_from_swap_cache(page);
748 page_cache_release(page);
753 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
755 * mem_cgroup_count_swap_user - count the user of a swap entry
756 * @ent: the swap entry to be checked
757 * @pagep: the pointer for the swap cache page of the entry to be stored
759 * Returns the number of the user of the swap entry. The number is valid only
760 * for swaps of anonymous pages.
761 * If the entry is found on swap cache, the page is stored to pagep with
762 * refcount of it being incremented.
764 int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
767 struct swap_info_struct *p;
770 page = find_get_page(&swapper_space, ent.val);
772 count += page_mapcount(page);
773 p = swap_info_get(ent);
775 count += swap_count(p->swap_map[swp_offset(ent)]);
776 spin_unlock(&swap_lock);
784 #ifdef CONFIG_HIBERNATION
786 * Find the swap type that corresponds to given device (if any).
788 * @offset - number of the PAGE_SIZE-sized block of the device, starting
789 * from 0, in which the swap header is expected to be located.
791 * This is needed for the suspend to disk (aka swsusp).
793 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
795 struct block_device *bdev = NULL;
799 bdev = bdget(device);
801 spin_lock(&swap_lock);
802 for (type = 0; type < nr_swapfiles; type++) {
803 struct swap_info_struct *sis = swap_info[type];
805 if (!(sis->flags & SWP_WRITEOK))
810 *bdev_p = bdgrab(sis->bdev);
812 spin_unlock(&swap_lock);
815 if (bdev == sis->bdev) {
816 struct swap_extent *se = &sis->first_swap_extent;
818 if (se->start_block == offset) {
820 *bdev_p = bdgrab(sis->bdev);
822 spin_unlock(&swap_lock);
828 spin_unlock(&swap_lock);
836 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
837 * corresponding to given index in swap_info (swap type).
839 sector_t swapdev_block(int type, pgoff_t offset)
841 struct block_device *bdev;
843 if ((unsigned int)type >= nr_swapfiles)
845 if (!(swap_info[type]->flags & SWP_WRITEOK))
847 return map_swap_entry(swp_entry(type, offset), &bdev);
851 * Return either the total number of swap pages of given type, or the number
852 * of free pages of that type (depending on @free)
854 * This is needed for software suspend
856 unsigned int count_swap_pages(int type, int free)
860 spin_lock(&swap_lock);
861 if ((unsigned int)type < nr_swapfiles) {
862 struct swap_info_struct *sis = swap_info[type];
864 if (sis->flags & SWP_WRITEOK) {
867 n -= sis->inuse_pages;
870 spin_unlock(&swap_lock);
873 #endif /* CONFIG_HIBERNATION */
876 * No need to decide whether this PTE shares the swap entry with others,
877 * just let do_wp_page work it out if a write is requested later - to
878 * force COW, vm_page_prot omits write permission from any private vma.
880 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
881 unsigned long addr, swp_entry_t entry, struct page *page)
883 struct mem_cgroup *ptr = NULL;
888 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
893 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
894 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
896 mem_cgroup_cancel_charge_swapin(ptr);
901 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
902 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
904 set_pte_at(vma->vm_mm, addr, pte,
905 pte_mkold(mk_pte(page, vma->vm_page_prot)));
906 page_add_anon_rmap(page, vma, addr);
907 mem_cgroup_commit_charge_swapin(page, ptr);
910 * Move the page to the active list so it is not
911 * immediately swapped out again after swapon.
915 pte_unmap_unlock(pte, ptl);
920 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
921 unsigned long addr, unsigned long end,
922 swp_entry_t entry, struct page *page)
924 pte_t swp_pte = swp_entry_to_pte(entry);
929 * We don't actually need pte lock while scanning for swp_pte: since
930 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
931 * page table while we're scanning; though it could get zapped, and on
932 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
933 * of unmatched parts which look like swp_pte, so unuse_pte must
934 * recheck under pte lock. Scanning without pte lock lets it be
935 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
937 pte = pte_offset_map(pmd, addr);
940 * swapoff spends a _lot_ of time in this loop!
941 * Test inline before going to call unuse_pte.
943 if (unlikely(pte_same(*pte, swp_pte))) {
945 ret = unuse_pte(vma, pmd, addr, entry, page);
948 pte = pte_offset_map(pmd, addr);
950 } while (pte++, addr += PAGE_SIZE, addr != end);
956 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
957 unsigned long addr, unsigned long end,
958 swp_entry_t entry, struct page *page)
964 pmd = pmd_offset(pud, addr);
966 next = pmd_addr_end(addr, end);
967 if (unlikely(pmd_trans_huge(*pmd)))
969 if (pmd_none_or_clear_bad(pmd))
971 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
974 } while (pmd++, addr = next, addr != end);
978 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
979 unsigned long addr, unsigned long end,
980 swp_entry_t entry, struct page *page)
986 pud = pud_offset(pgd, addr);
988 next = pud_addr_end(addr, end);
989 if (pud_none_or_clear_bad(pud))
991 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
994 } while (pud++, addr = next, addr != end);
998 static int unuse_vma(struct vm_area_struct *vma,
999 swp_entry_t entry, struct page *page)
1002 unsigned long addr, end, next;
1005 if (page_anon_vma(page)) {
1006 addr = page_address_in_vma(page, vma);
1007 if (addr == -EFAULT)
1010 end = addr + PAGE_SIZE;
1012 addr = vma->vm_start;
1016 pgd = pgd_offset(vma->vm_mm, addr);
1018 next = pgd_addr_end(addr, end);
1019 if (pgd_none_or_clear_bad(pgd))
1021 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
1024 } while (pgd++, addr = next, addr != end);
1028 static int unuse_mm(struct mm_struct *mm,
1029 swp_entry_t entry, struct page *page)
1031 struct vm_area_struct *vma;
1034 if (!down_read_trylock(&mm->mmap_sem)) {
1036 * Activate page so shrink_inactive_list is unlikely to unmap
1037 * its ptes while lock is dropped, so swapoff can make progress.
1039 activate_page(page);
1041 down_read(&mm->mmap_sem);
1044 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1045 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
1048 up_read(&mm->mmap_sem);
1049 return (ret < 0)? ret: 0;
1053 * Scan swap_map from current position to next entry still in use.
1054 * Recycle to start on reaching the end, returning 0 when empty.
1056 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1059 unsigned int max = si->max;
1060 unsigned int i = prev;
1061 unsigned char count;
1064 * No need for swap_lock here: we're just looking
1065 * for whether an entry is in use, not modifying it; false
1066 * hits are okay, and sys_swapoff() has already prevented new
1067 * allocations from this area (while holding swap_lock).
1076 * No entries in use at top of swap_map,
1077 * loop back to start and recheck there.
1083 count = si->swap_map[i];
1084 if (count && swap_count(count) != SWAP_MAP_BAD)
1091 * We completely avoid races by reading each swap page in advance,
1092 * and then search for the process using it. All the necessary
1093 * page table adjustments can then be made atomically.
1095 static int try_to_unuse(unsigned int type)
1097 struct swap_info_struct *si = swap_info[type];
1098 struct mm_struct *start_mm;
1099 unsigned char *swap_map;
1100 unsigned char swcount;
1107 * When searching mms for an entry, a good strategy is to
1108 * start at the first mm we freed the previous entry from
1109 * (though actually we don't notice whether we or coincidence
1110 * freed the entry). Initialize this start_mm with a hold.
1112 * A simpler strategy would be to start at the last mm we
1113 * freed the previous entry from; but that would take less
1114 * advantage of mmlist ordering, which clusters forked mms
1115 * together, child after parent. If we race with dup_mmap(), we
1116 * prefer to resolve parent before child, lest we miss entries
1117 * duplicated after we scanned child: using last mm would invert
1120 start_mm = &init_mm;
1121 atomic_inc(&init_mm.mm_users);
1124 * Keep on scanning until all entries have gone. Usually,
1125 * one pass through swap_map is enough, but not necessarily:
1126 * there are races when an instance of an entry might be missed.
1128 while ((i = find_next_to_unuse(si, i)) != 0) {
1129 if (signal_pending(current)) {
1135 * Get a page for the entry, using the existing swap
1136 * cache page if there is one. Otherwise, get a clean
1137 * page and read the swap into it.
1139 swap_map = &si->swap_map[i];
1140 entry = swp_entry(type, i);
1141 page = read_swap_cache_async(entry,
1142 GFP_HIGHUSER_MOVABLE, NULL, 0);
1145 * Either swap_duplicate() failed because entry
1146 * has been freed independently, and will not be
1147 * reused since sys_swapoff() already disabled
1148 * allocation from here, or alloc_page() failed.
1157 * Don't hold on to start_mm if it looks like exiting.
1159 if (atomic_read(&start_mm->mm_users) == 1) {
1161 start_mm = &init_mm;
1162 atomic_inc(&init_mm.mm_users);
1166 * Wait for and lock page. When do_swap_page races with
1167 * try_to_unuse, do_swap_page can handle the fault much
1168 * faster than try_to_unuse can locate the entry. This
1169 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1170 * defer to do_swap_page in such a case - in some tests,
1171 * do_swap_page and try_to_unuse repeatedly compete.
1173 wait_on_page_locked(page);
1174 wait_on_page_writeback(page);
1176 wait_on_page_writeback(page);
1179 * Remove all references to entry.
1181 swcount = *swap_map;
1182 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1183 retval = shmem_unuse(entry, page);
1184 /* page has already been unlocked and released */
1189 if (swap_count(swcount) && start_mm != &init_mm)
1190 retval = unuse_mm(start_mm, entry, page);
1192 if (swap_count(*swap_map)) {
1193 int set_start_mm = (*swap_map >= swcount);
1194 struct list_head *p = &start_mm->mmlist;
1195 struct mm_struct *new_start_mm = start_mm;
1196 struct mm_struct *prev_mm = start_mm;
1197 struct mm_struct *mm;
1199 atomic_inc(&new_start_mm->mm_users);
1200 atomic_inc(&prev_mm->mm_users);
1201 spin_lock(&mmlist_lock);
1202 while (swap_count(*swap_map) && !retval &&
1203 (p = p->next) != &start_mm->mmlist) {
1204 mm = list_entry(p, struct mm_struct, mmlist);
1205 if (!atomic_inc_not_zero(&mm->mm_users))
1207 spin_unlock(&mmlist_lock);
1213 swcount = *swap_map;
1214 if (!swap_count(swcount)) /* any usage ? */
1216 else if (mm == &init_mm)
1219 retval = unuse_mm(mm, entry, page);
1221 if (set_start_mm && *swap_map < swcount) {
1222 mmput(new_start_mm);
1223 atomic_inc(&mm->mm_users);
1227 spin_lock(&mmlist_lock);
1229 spin_unlock(&mmlist_lock);
1232 start_mm = new_start_mm;
1236 page_cache_release(page);
1241 * If a reference remains (rare), we would like to leave
1242 * the page in the swap cache; but try_to_unmap could
1243 * then re-duplicate the entry once we drop page lock,
1244 * so we might loop indefinitely; also, that page could
1245 * not be swapped out to other storage meanwhile. So:
1246 * delete from cache even if there's another reference,
1247 * after ensuring that the data has been saved to disk -
1248 * since if the reference remains (rarer), it will be
1249 * read from disk into another page. Splitting into two
1250 * pages would be incorrect if swap supported "shared
1251 * private" pages, but they are handled by tmpfs files.
1253 * Given how unuse_vma() targets one particular offset
1254 * in an anon_vma, once the anon_vma has been determined,
1255 * this splitting happens to be just what is needed to
1256 * handle where KSM pages have been swapped out: re-reading
1257 * is unnecessarily slow, but we can fix that later on.
1259 if (swap_count(*swap_map) &&
1260 PageDirty(page) && PageSwapCache(page)) {
1261 struct writeback_control wbc = {
1262 .sync_mode = WB_SYNC_NONE,
1265 swap_writepage(page, &wbc);
1267 wait_on_page_writeback(page);
1271 * It is conceivable that a racing task removed this page from
1272 * swap cache just before we acquired the page lock at the top,
1273 * or while we dropped it in unuse_mm(). The page might even
1274 * be back in swap cache on another swap area: that we must not
1275 * delete, since it may not have been written out to swap yet.
1277 if (PageSwapCache(page) &&
1278 likely(page_private(page) == entry.val))
1279 delete_from_swap_cache(page);
1282 * So we could skip searching mms once swap count went
1283 * to 1, we did not mark any present ptes as dirty: must
1284 * mark page dirty so shrink_page_list will preserve it.
1288 page_cache_release(page);
1291 * Make sure that we aren't completely killing
1292 * interactive performance.
1302 * After a successful try_to_unuse, if no swap is now in use, we know
1303 * we can empty the mmlist. swap_lock must be held on entry and exit.
1304 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1305 * added to the mmlist just after page_duplicate - before would be racy.
1307 static void drain_mmlist(void)
1309 struct list_head *p, *next;
1312 for (type = 0; type < nr_swapfiles; type++)
1313 if (swap_info[type]->inuse_pages)
1315 spin_lock(&mmlist_lock);
1316 list_for_each_safe(p, next, &init_mm.mmlist)
1318 spin_unlock(&mmlist_lock);
1322 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1323 * corresponds to page offset for the specified swap entry.
1324 * Note that the type of this function is sector_t, but it returns page offset
1325 * into the bdev, not sector offset.
1327 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1329 struct swap_info_struct *sis;
1330 struct swap_extent *start_se;
1331 struct swap_extent *se;
1334 sis = swap_info[swp_type(entry)];
1337 offset = swp_offset(entry);
1338 start_se = sis->curr_swap_extent;
1342 struct list_head *lh;
1344 if (se->start_page <= offset &&
1345 offset < (se->start_page + se->nr_pages)) {
1346 return se->start_block + (offset - se->start_page);
1349 se = list_entry(lh, struct swap_extent, list);
1350 sis->curr_swap_extent = se;
1351 BUG_ON(se == start_se); /* It *must* be present */
1356 * Returns the page offset into bdev for the specified page's swap entry.
1358 sector_t map_swap_page(struct page *page, struct block_device **bdev)
1361 entry.val = page_private(page);
1362 return map_swap_entry(entry, bdev);
1366 * Free all of a swapdev's extent information
1368 static void destroy_swap_extents(struct swap_info_struct *sis)
1370 while (!list_empty(&sis->first_swap_extent.list)) {
1371 struct swap_extent *se;
1373 se = list_entry(sis->first_swap_extent.list.next,
1374 struct swap_extent, list);
1375 list_del(&se->list);
1381 * Add a block range (and the corresponding page range) into this swapdev's
1382 * extent list. The extent list is kept sorted in page order.
1384 * This function rather assumes that it is called in ascending page order.
1387 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1388 unsigned long nr_pages, sector_t start_block)
1390 struct swap_extent *se;
1391 struct swap_extent *new_se;
1392 struct list_head *lh;
1394 if (start_page == 0) {
1395 se = &sis->first_swap_extent;
1396 sis->curr_swap_extent = se;
1398 se->nr_pages = nr_pages;
1399 se->start_block = start_block;
1402 lh = sis->first_swap_extent.list.prev; /* Highest extent */
1403 se = list_entry(lh, struct swap_extent, list);
1404 BUG_ON(se->start_page + se->nr_pages != start_page);
1405 if (se->start_block + se->nr_pages == start_block) {
1407 se->nr_pages += nr_pages;
1413 * No merge. Insert a new extent, preserving ordering.
1415 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1418 new_se->start_page = start_page;
1419 new_se->nr_pages = nr_pages;
1420 new_se->start_block = start_block;
1422 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1427 * A `swap extent' is a simple thing which maps a contiguous range of pages
1428 * onto a contiguous range of disk blocks. An ordered list of swap extents
1429 * is built at swapon time and is then used at swap_writepage/swap_readpage
1430 * time for locating where on disk a page belongs.
1432 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1433 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1434 * swap files identically.
1436 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1437 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1438 * swapfiles are handled *identically* after swapon time.
1440 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1441 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1442 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1443 * requirements, they are simply tossed out - we will never use those blocks
1446 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1447 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1448 * which will scribble on the fs.
1450 * The amount of disk space which a single swap extent represents varies.
1451 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1452 * extents in the list. To avoid much list walking, we cache the previous
1453 * search location in `curr_swap_extent', and start new searches from there.
1454 * This is extremely effective. The average number of iterations in
1455 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1457 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1459 struct inode *inode;
1460 unsigned blocks_per_page;
1461 unsigned long page_no;
1463 sector_t probe_block;
1464 sector_t last_block;
1465 sector_t lowest_block = -1;
1466 sector_t highest_block = 0;
1470 inode = sis->swap_file->f_mapping->host;
1471 if (S_ISBLK(inode->i_mode)) {
1472 ret = add_swap_extent(sis, 0, sis->max, 0);
1477 blkbits = inode->i_blkbits;
1478 blocks_per_page = PAGE_SIZE >> blkbits;
1481 * Map all the blocks into the extent list. This code doesn't try
1486 last_block = i_size_read(inode) >> blkbits;
1487 while ((probe_block + blocks_per_page) <= last_block &&
1488 page_no < sis->max) {
1489 unsigned block_in_page;
1490 sector_t first_block;
1492 first_block = bmap(inode, probe_block);
1493 if (first_block == 0)
1497 * It must be PAGE_SIZE aligned on-disk
1499 if (first_block & (blocks_per_page - 1)) {
1504 for (block_in_page = 1; block_in_page < blocks_per_page;
1508 block = bmap(inode, probe_block + block_in_page);
1511 if (block != first_block + block_in_page) {
1518 first_block >>= (PAGE_SHIFT - blkbits);
1519 if (page_no) { /* exclude the header page */
1520 if (first_block < lowest_block)
1521 lowest_block = first_block;
1522 if (first_block > highest_block)
1523 highest_block = first_block;
1527 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1529 ret = add_swap_extent(sis, page_no, 1, first_block);
1534 probe_block += blocks_per_page;
1539 *span = 1 + highest_block - lowest_block;
1541 page_no = 1; /* force Empty message */
1543 sis->pages = page_no - 1;
1544 sis->highest_bit = page_no - 1;
1548 printk(KERN_ERR "swapon: swapfile has holes\n");
1553 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1555 struct swap_info_struct *p = NULL;
1556 unsigned char *swap_map;
1557 struct file *swap_file, *victim;
1558 struct address_space *mapping;
1559 struct inode *inode;
1564 if (!capable(CAP_SYS_ADMIN))
1567 pathname = getname(specialfile);
1568 err = PTR_ERR(pathname);
1569 if (IS_ERR(pathname))
1572 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1574 err = PTR_ERR(victim);
1578 mapping = victim->f_mapping;
1580 spin_lock(&swap_lock);
1581 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1582 p = swap_info[type];
1583 if (p->flags & SWP_WRITEOK) {
1584 if (p->swap_file->f_mapping == mapping)
1591 spin_unlock(&swap_lock);
1594 if (!security_vm_enough_memory(p->pages))
1595 vm_unacct_memory(p->pages);
1598 spin_unlock(&swap_lock);
1602 swap_list.head = p->next;
1604 swap_info[prev]->next = p->next;
1605 if (type == swap_list.next) {
1606 /* just pick something that's safe... */
1607 swap_list.next = swap_list.head;
1610 for (i = p->next; i >= 0; i = swap_info[i]->next)
1611 swap_info[i]->prio = p->prio--;
1614 nr_swap_pages -= p->pages;
1615 total_swap_pages -= p->pages;
1616 p->flags &= ~SWP_WRITEOK;
1617 spin_unlock(&swap_lock);
1619 current->flags |= PF_OOM_ORIGIN;
1620 err = try_to_unuse(type);
1621 current->flags &= ~PF_OOM_ORIGIN;
1624 /* re-insert swap space back into swap_list */
1625 spin_lock(&swap_lock);
1627 p->prio = --least_priority;
1629 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1630 if (p->prio >= swap_info[i]->prio)
1636 swap_list.head = swap_list.next = type;
1638 swap_info[prev]->next = type;
1639 nr_swap_pages += p->pages;
1640 total_swap_pages += p->pages;
1641 p->flags |= SWP_WRITEOK;
1642 spin_unlock(&swap_lock);
1646 /* wait for any unplug function to finish */
1647 down_write(&swap_unplug_sem);
1648 up_write(&swap_unplug_sem);
1650 destroy_swap_extents(p);
1651 if (p->flags & SWP_CONTINUED)
1652 free_swap_count_continuations(p);
1654 mutex_lock(&swapon_mutex);
1655 spin_lock(&swap_lock);
1658 /* wait for anyone still in scan_swap_map */
1659 p->highest_bit = 0; /* cuts scans short */
1660 while (p->flags >= SWP_SCANNING) {
1661 spin_unlock(&swap_lock);
1662 schedule_timeout_uninterruptible(1);
1663 spin_lock(&swap_lock);
1666 swap_file = p->swap_file;
1667 p->swap_file = NULL;
1669 swap_map = p->swap_map;
1672 spin_unlock(&swap_lock);
1673 mutex_unlock(&swapon_mutex);
1675 /* Destroy swap account informatin */
1676 swap_cgroup_swapoff(type);
1678 inode = mapping->host;
1679 if (S_ISBLK(inode->i_mode)) {
1680 struct block_device *bdev = I_BDEV(inode);
1681 set_blocksize(bdev, p->old_block_size);
1682 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
1684 mutex_lock(&inode->i_mutex);
1685 inode->i_flags &= ~S_SWAPFILE;
1686 mutex_unlock(&inode->i_mutex);
1688 filp_close(swap_file, NULL);
1690 atomic_inc(&proc_poll_event);
1691 wake_up_interruptible(&proc_poll_wait);
1694 filp_close(victim, NULL);
1699 #ifdef CONFIG_PROC_FS
1701 struct seq_file seq;
1705 static unsigned swaps_poll(struct file *file, poll_table *wait)
1707 struct proc_swaps *s = file->private_data;
1709 poll_wait(file, &proc_poll_wait, wait);
1711 if (s->event != atomic_read(&proc_poll_event)) {
1712 s->event = atomic_read(&proc_poll_event);
1713 return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
1716 return POLLIN | POLLRDNORM;
1720 static void *swap_start(struct seq_file *swap, loff_t *pos)
1722 struct swap_info_struct *si;
1726 mutex_lock(&swapon_mutex);
1729 return SEQ_START_TOKEN;
1731 for (type = 0; type < nr_swapfiles; type++) {
1732 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1733 si = swap_info[type];
1734 if (!(si->flags & SWP_USED) || !si->swap_map)
1743 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1745 struct swap_info_struct *si = v;
1748 if (v == SEQ_START_TOKEN)
1751 type = si->type + 1;
1753 for (; type < nr_swapfiles; type++) {
1754 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1755 si = swap_info[type];
1756 if (!(si->flags & SWP_USED) || !si->swap_map)
1765 static void swap_stop(struct seq_file *swap, void *v)
1767 mutex_unlock(&swapon_mutex);
1770 static int swap_show(struct seq_file *swap, void *v)
1772 struct swap_info_struct *si = v;
1776 if (si == SEQ_START_TOKEN) {
1777 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1781 file = si->swap_file;
1782 len = seq_path(swap, &file->f_path, " \t\n\\");
1783 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1784 len < 40 ? 40 - len : 1, " ",
1785 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1786 "partition" : "file\t",
1787 si->pages << (PAGE_SHIFT - 10),
1788 si->inuse_pages << (PAGE_SHIFT - 10),
1793 static const struct seq_operations swaps_op = {
1794 .start = swap_start,
1800 static int swaps_open(struct inode *inode, struct file *file)
1802 struct proc_swaps *s;
1805 s = kmalloc(sizeof(struct proc_swaps), GFP_KERNEL);
1809 file->private_data = s;
1811 ret = seq_open(file, &swaps_op);
1818 s->event = atomic_read(&proc_poll_event);
1822 static const struct file_operations proc_swaps_operations = {
1825 .llseek = seq_lseek,
1826 .release = seq_release,
1830 static int __init procswaps_init(void)
1832 proc_create("swaps", 0, NULL, &proc_swaps_operations);
1835 __initcall(procswaps_init);
1836 #endif /* CONFIG_PROC_FS */
1838 #ifdef MAX_SWAPFILES_CHECK
1839 static int __init max_swapfiles_check(void)
1841 MAX_SWAPFILES_CHECK();
1844 late_initcall(max_swapfiles_check);
1848 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1850 * The swapon system call
1852 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
1854 struct swap_info_struct *p;
1856 struct block_device *bdev = NULL;
1857 struct file *swap_file = NULL;
1858 struct address_space *mapping;
1862 union swap_header *swap_header;
1863 unsigned int nr_good_pages;
1866 unsigned long maxpages;
1867 unsigned long swapfilepages;
1868 unsigned char *swap_map = NULL;
1869 struct page *page = NULL;
1870 struct inode *inode = NULL;
1873 if (!capable(CAP_SYS_ADMIN))
1876 p = kzalloc(sizeof(*p), GFP_KERNEL);
1880 spin_lock(&swap_lock);
1881 for (type = 0; type < nr_swapfiles; type++) {
1882 if (!(swap_info[type]->flags & SWP_USED))
1886 if (type >= MAX_SWAPFILES) {
1887 spin_unlock(&swap_lock);
1891 if (type >= nr_swapfiles) {
1893 swap_info[type] = p;
1895 * Write swap_info[type] before nr_swapfiles, in case a
1896 * racing procfs swap_start() or swap_next() is reading them.
1897 * (We never shrink nr_swapfiles, we never free this entry.)
1903 p = swap_info[type];
1905 * Do not memset this entry: a racing procfs swap_next()
1906 * would be relying on p->type to remain valid.
1909 INIT_LIST_HEAD(&p->first_swap_extent.list);
1910 p->flags = SWP_USED;
1912 spin_unlock(&swap_lock);
1914 name = getname(specialfile);
1915 error = PTR_ERR(name);
1920 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1921 error = PTR_ERR(swap_file);
1922 if (IS_ERR(swap_file)) {
1927 p->swap_file = swap_file;
1928 mapping = swap_file->f_mapping;
1929 inode = mapping->host;
1932 for (i = 0; i < nr_swapfiles; i++) {
1933 struct swap_info_struct *q = swap_info[i];
1935 if (i == type || !q->swap_file)
1937 if (mapping == q->swap_file->f_mapping)
1942 if (S_ISBLK(inode->i_mode)) {
1943 bdev = bdgrab(I_BDEV(inode));
1944 error = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL,
1951 p->old_block_size = block_size(bdev);
1952 error = set_blocksize(bdev, PAGE_SIZE);
1956 p->flags |= SWP_BLKDEV;
1957 } else if (S_ISREG(inode->i_mode)) {
1958 p->bdev = inode->i_sb->s_bdev;
1959 mutex_lock(&inode->i_mutex);
1961 if (IS_SWAPFILE(inode)) {
1969 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1972 * Read the swap header.
1974 if (!mapping->a_ops->readpage) {
1978 page = read_mapping_page(mapping, 0, swap_file);
1980 error = PTR_ERR(page);
1983 swap_header = kmap(page);
1985 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1986 printk(KERN_ERR "Unable to find swap-space signature\n");
1991 /* swap partition endianess hack... */
1992 if (swab32(swap_header->info.version) == 1) {
1993 swab32s(&swap_header->info.version);
1994 swab32s(&swap_header->info.last_page);
1995 swab32s(&swap_header->info.nr_badpages);
1996 for (i = 0; i < swap_header->info.nr_badpages; i++)
1997 swab32s(&swap_header->info.badpages[i]);
1999 /* Check the swap header's sub-version */
2000 if (swap_header->info.version != 1) {
2002 "Unable to handle swap header version %d\n",
2003 swap_header->info.version);
2009 p->cluster_next = 1;
2013 * Find out how many pages are allowed for a single swap
2014 * device. There are two limiting factors: 1) the number of
2015 * bits for the swap offset in the swp_entry_t type and
2016 * 2) the number of bits in the a swap pte as defined by
2017 * the different architectures. In order to find the
2018 * largest possible bit mask a swap entry with swap type 0
2019 * and swap offset ~0UL is created, encoded to a swap pte,
2020 * decoded to a swp_entry_t again and finally the swap
2021 * offset is extracted. This will mask all the bits from
2022 * the initial ~0UL mask that can't be encoded in either
2023 * the swp_entry_t or the architecture definition of a
2026 maxpages = swp_offset(pte_to_swp_entry(
2027 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2028 if (maxpages > swap_header->info.last_page) {
2029 maxpages = swap_header->info.last_page + 1;
2030 /* p->max is an unsigned int: don't overflow it */
2031 if ((unsigned int)maxpages == 0)
2032 maxpages = UINT_MAX;
2034 p->highest_bit = maxpages - 1;
2039 if (swapfilepages && maxpages > swapfilepages) {
2041 "Swap area shorter than signature indicates\n");
2044 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2046 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2049 /* OK, set up the swap map and apply the bad block list */
2050 swap_map = vmalloc(maxpages);
2056 memset(swap_map, 0, maxpages);
2057 nr_good_pages = maxpages - 1; /* omit header page */
2059 for (i = 0; i < swap_header->info.nr_badpages; i++) {
2060 unsigned int page_nr = swap_header->info.badpages[i];
2061 if (page_nr == 0 || page_nr > swap_header->info.last_page) {
2065 if (page_nr < maxpages) {
2066 swap_map[page_nr] = SWAP_MAP_BAD;
2071 error = swap_cgroup_swapon(type, maxpages);
2075 if (nr_good_pages) {
2076 swap_map[0] = SWAP_MAP_BAD;
2078 p->pages = nr_good_pages;
2079 nr_extents = setup_swap_extents(p, &span);
2080 if (nr_extents < 0) {
2084 nr_good_pages = p->pages;
2086 if (!nr_good_pages) {
2087 printk(KERN_WARNING "Empty swap-file\n");
2093 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2094 p->flags |= SWP_SOLIDSTATE;
2095 p->cluster_next = 1 + (random32() % p->highest_bit);
2097 if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
2098 p->flags |= SWP_DISCARDABLE;
2101 mutex_lock(&swapon_mutex);
2102 spin_lock(&swap_lock);
2103 if (swap_flags & SWAP_FLAG_PREFER)
2105 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2107 p->prio = --least_priority;
2108 p->swap_map = swap_map;
2109 p->flags |= SWP_WRITEOK;
2110 nr_swap_pages += nr_good_pages;
2111 total_swap_pages += nr_good_pages;
2113 printk(KERN_INFO "Adding %uk swap on %s. "
2114 "Priority:%d extents:%d across:%lluk %s%s\n",
2115 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
2116 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2117 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2118 (p->flags & SWP_DISCARDABLE) ? "D" : "");
2120 /* insert swap space into swap_list: */
2122 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
2123 if (p->prio >= swap_info[i]->prio)
2129 swap_list.head = swap_list.next = type;
2131 swap_info[prev]->next = type;
2132 spin_unlock(&swap_lock);
2133 mutex_unlock(&swapon_mutex);
2134 atomic_inc(&proc_poll_event);
2135 wake_up_interruptible(&proc_poll_wait);
2141 set_blocksize(bdev, p->old_block_size);
2142 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2144 destroy_swap_extents(p);
2145 swap_cgroup_swapoff(type);
2147 spin_lock(&swap_lock);
2148 p->swap_file = NULL;
2150 spin_unlock(&swap_lock);
2154 mutex_unlock(&inode->i_mutex);
2157 filp_close(swap_file, NULL);
2160 if (page && !IS_ERR(page)) {
2162 page_cache_release(page);
2168 inode->i_flags |= S_SWAPFILE;
2169 mutex_unlock(&inode->i_mutex);
2174 void si_swapinfo(struct sysinfo *val)
2177 unsigned long nr_to_be_unused = 0;
2179 spin_lock(&swap_lock);
2180 for (type = 0; type < nr_swapfiles; type++) {
2181 struct swap_info_struct *si = swap_info[type];
2183 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2184 nr_to_be_unused += si->inuse_pages;
2186 val->freeswap = nr_swap_pages + nr_to_be_unused;
2187 val->totalswap = total_swap_pages + nr_to_be_unused;
2188 spin_unlock(&swap_lock);
2192 * Verify that a swap entry is valid and increment its swap map count.
2194 * Returns error code in following case.
2196 * - swp_entry is invalid -> EINVAL
2197 * - swp_entry is migration entry -> EINVAL
2198 * - swap-cache reference is requested but there is already one. -> EEXIST
2199 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2200 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2202 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2204 struct swap_info_struct *p;
2205 unsigned long offset, type;
2206 unsigned char count;
2207 unsigned char has_cache;
2210 if (non_swap_entry(entry))
2213 type = swp_type(entry);
2214 if (type >= nr_swapfiles)
2216 p = swap_info[type];
2217 offset = swp_offset(entry);
2219 spin_lock(&swap_lock);
2220 if (unlikely(offset >= p->max))
2223 count = p->swap_map[offset];
2224 has_cache = count & SWAP_HAS_CACHE;
2225 count &= ~SWAP_HAS_CACHE;
2228 if (usage == SWAP_HAS_CACHE) {
2230 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2231 if (!has_cache && count)
2232 has_cache = SWAP_HAS_CACHE;
2233 else if (has_cache) /* someone else added cache */
2235 else /* no users remaining */
2238 } else if (count || has_cache) {
2240 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2242 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2244 else if (swap_count_continued(p, offset, count))
2245 count = COUNT_CONTINUED;
2249 err = -ENOENT; /* unused swap entry */
2251 p->swap_map[offset] = count | has_cache;
2254 spin_unlock(&swap_lock);
2259 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2264 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2265 * (in which case its reference count is never incremented).
2267 void swap_shmem_alloc(swp_entry_t entry)
2269 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2273 * Increase reference count of swap entry by 1.
2274 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2275 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2276 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2277 * might occur if a page table entry has got corrupted.
2279 int swap_duplicate(swp_entry_t entry)
2283 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2284 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2289 * @entry: swap entry for which we allocate swap cache.
2291 * Called when allocating swap cache for existing swap entry,
2292 * This can return error codes. Returns 0 at success.
2293 * -EBUSY means there is a swap cache.
2294 * Note: return code is different from swap_duplicate().
2296 int swapcache_prepare(swp_entry_t entry)
2298 return __swap_duplicate(entry, SWAP_HAS_CACHE);
2302 * swap_lock prevents swap_map being freed. Don't grab an extra
2303 * reference on the swaphandle, it doesn't matter if it becomes unused.
2305 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2307 struct swap_info_struct *si;
2308 int our_page_cluster = page_cluster;
2309 pgoff_t target, toff;
2313 if (!our_page_cluster) /* no readahead */
2316 si = swap_info[swp_type(entry)];
2317 target = swp_offset(entry);
2318 base = (target >> our_page_cluster) << our_page_cluster;
2319 end = base + (1 << our_page_cluster);
2320 if (!base) /* first page is swap header */
2323 spin_lock(&swap_lock);
2324 if (end > si->max) /* don't go beyond end of map */
2327 /* Count contiguous allocated slots above our target */
2328 for (toff = target; ++toff < end; nr_pages++) {
2329 /* Don't read in free or bad pages */
2330 if (!si->swap_map[toff])
2332 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2335 /* Count contiguous allocated slots below our target */
2336 for (toff = target; --toff >= base; nr_pages++) {
2337 /* Don't read in free or bad pages */
2338 if (!si->swap_map[toff])
2340 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2343 spin_unlock(&swap_lock);
2346 * Indicate starting offset, and return number of pages to get:
2347 * if only 1, say 0, since there's then no readahead to be done.
2350 return nr_pages? ++nr_pages: 0;
2354 * add_swap_count_continuation - called when a swap count is duplicated
2355 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2356 * page of the original vmalloc'ed swap_map, to hold the continuation count
2357 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2358 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2360 * These continuation pages are seldom referenced: the common paths all work
2361 * on the original swap_map, only referring to a continuation page when the
2362 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2364 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2365 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2366 * can be called after dropping locks.
2368 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2370 struct swap_info_struct *si;
2373 struct page *list_page;
2375 unsigned char count;
2378 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2379 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2381 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2383 si = swap_info_get(entry);
2386 * An acceptable race has occurred since the failing
2387 * __swap_duplicate(): the swap entry has been freed,
2388 * perhaps even the whole swap_map cleared for swapoff.
2393 offset = swp_offset(entry);
2394 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2396 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2398 * The higher the swap count, the more likely it is that tasks
2399 * will race to add swap count continuation: we need to avoid
2400 * over-provisioning.
2406 spin_unlock(&swap_lock);
2411 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2412 * no architecture is using highmem pages for kernel pagetables: so it
2413 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2415 head = vmalloc_to_page(si->swap_map + offset);
2416 offset &= ~PAGE_MASK;
2419 * Page allocation does not initialize the page's lru field,
2420 * but it does always reset its private field.
2422 if (!page_private(head)) {
2423 BUG_ON(count & COUNT_CONTINUED);
2424 INIT_LIST_HEAD(&head->lru);
2425 set_page_private(head, SWP_CONTINUED);
2426 si->flags |= SWP_CONTINUED;
2429 list_for_each_entry(list_page, &head->lru, lru) {
2433 * If the previous map said no continuation, but we've found
2434 * a continuation page, free our allocation and use this one.
2436 if (!(count & COUNT_CONTINUED))
2439 map = kmap_atomic(list_page, KM_USER0) + offset;
2441 kunmap_atomic(map, KM_USER0);
2444 * If this continuation count now has some space in it,
2445 * free our allocation and use this one.
2447 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2451 list_add_tail(&page->lru, &head->lru);
2452 page = NULL; /* now it's attached, don't free it */
2454 spin_unlock(&swap_lock);
2462 * swap_count_continued - when the original swap_map count is incremented
2463 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2464 * into, carry if so, or else fail until a new continuation page is allocated;
2465 * when the original swap_map count is decremented from 0 with continuation,
2466 * borrow from the continuation and report whether it still holds more.
2467 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2469 static bool swap_count_continued(struct swap_info_struct *si,
2470 pgoff_t offset, unsigned char count)
2476 head = vmalloc_to_page(si->swap_map + offset);
2477 if (page_private(head) != SWP_CONTINUED) {
2478 BUG_ON(count & COUNT_CONTINUED);
2479 return false; /* need to add count continuation */
2482 offset &= ~PAGE_MASK;
2483 page = list_entry(head->lru.next, struct page, lru);
2484 map = kmap_atomic(page, KM_USER0) + offset;
2486 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2487 goto init_map; /* jump over SWAP_CONT_MAX checks */
2489 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2491 * Think of how you add 1 to 999
2493 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2494 kunmap_atomic(map, KM_USER0);
2495 page = list_entry(page->lru.next, struct page, lru);
2496 BUG_ON(page == head);
2497 map = kmap_atomic(page, KM_USER0) + offset;
2499 if (*map == SWAP_CONT_MAX) {
2500 kunmap_atomic(map, KM_USER0);
2501 page = list_entry(page->lru.next, struct page, lru);
2503 return false; /* add count continuation */
2504 map = kmap_atomic(page, KM_USER0) + offset;
2505 init_map: *map = 0; /* we didn't zero the page */
2508 kunmap_atomic(map, KM_USER0);
2509 page = list_entry(page->lru.prev, struct page, lru);
2510 while (page != head) {
2511 map = kmap_atomic(page, KM_USER0) + offset;
2512 *map = COUNT_CONTINUED;
2513 kunmap_atomic(map, KM_USER0);
2514 page = list_entry(page->lru.prev, struct page, lru);
2516 return true; /* incremented */
2518 } else { /* decrementing */
2520 * Think of how you subtract 1 from 1000
2522 BUG_ON(count != COUNT_CONTINUED);
2523 while (*map == COUNT_CONTINUED) {
2524 kunmap_atomic(map, KM_USER0);
2525 page = list_entry(page->lru.next, struct page, lru);
2526 BUG_ON(page == head);
2527 map = kmap_atomic(page, KM_USER0) + offset;
2533 kunmap_atomic(map, KM_USER0);
2534 page = list_entry(page->lru.prev, struct page, lru);
2535 while (page != head) {
2536 map = kmap_atomic(page, KM_USER0) + offset;
2537 *map = SWAP_CONT_MAX | count;
2538 count = COUNT_CONTINUED;
2539 kunmap_atomic(map, KM_USER0);
2540 page = list_entry(page->lru.prev, struct page, lru);
2542 return count == COUNT_CONTINUED;
2547 * free_swap_count_continuations - swapoff free all the continuation pages
2548 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2550 static void free_swap_count_continuations(struct swap_info_struct *si)
2554 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2556 head = vmalloc_to_page(si->swap_map + offset);
2557 if (page_private(head)) {
2558 struct list_head *this, *next;
2559 list_for_each_safe(this, next, &head->lru) {
2561 page = list_entry(this, struct page, lru);