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/rmap.h>
26 #include <linux/security.h>
27 #include <linux/backing-dev.h>
28 #include <linux/mutex.h>
29 #include <linux/capability.h>
30 #include <linux/syscalls.h>
31 #include <linux/memcontrol.h>
33 #include <asm/pgtable.h>
34 #include <asm/tlbflush.h>
35 #include <linux/swapops.h>
36 #include <linux/page_cgroup.h>
38 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
40 static void free_swap_count_continuations(struct swap_info_struct *);
41 static sector_t map_swap_entry(swp_entry_t, struct block_device**);
43 static DEFINE_SPINLOCK(swap_lock);
44 static unsigned int nr_swapfiles;
46 long total_swap_pages;
47 static int least_priority;
49 static const char Bad_file[] = "Bad swap file entry ";
50 static const char Unused_file[] = "Unused swap file entry ";
51 static const char Bad_offset[] = "Bad swap offset entry ";
52 static const char Unused_offset[] = "Unused swap offset entry ";
54 static struct swap_list_t swap_list = {-1, -1};
56 static struct swap_info_struct *swap_info[MAX_SWAPFILES];
58 static DEFINE_MUTEX(swapon_mutex);
60 static inline unsigned char swap_count(unsigned char ent)
62 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
65 /* returns 1 if swap entry is freed */
67 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
69 swp_entry_t entry = swp_entry(si->type, offset);
73 page = find_get_page(&swapper_space, entry.val);
77 * This function is called from scan_swap_map() and it's called
78 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
79 * We have to use trylock for avoiding deadlock. This is a special
80 * case and you should use try_to_free_swap() with explicit lock_page()
81 * in usual operations.
83 if (trylock_page(page)) {
84 ret = try_to_free_swap(page);
87 page_cache_release(page);
92 * We need this because the bdev->unplug_fn can sleep and we cannot
93 * hold swap_lock while calling the unplug_fn. And swap_lock
94 * cannot be turned into a mutex.
96 static DECLARE_RWSEM(swap_unplug_sem);
98 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
102 down_read(&swap_unplug_sem);
103 entry.val = page_private(page);
104 if (PageSwapCache(page)) {
105 struct block_device *bdev = swap_info[swp_type(entry)]->bdev;
106 struct backing_dev_info *bdi;
109 * If the page is removed from swapcache from under us (with a
110 * racy try_to_unuse/swapoff) we need an additional reference
111 * count to avoid reading garbage from page_private(page) above.
112 * If the WARN_ON triggers during a swapoff it maybe the race
113 * condition and it's harmless. However if it triggers without
114 * swapoff it signals a problem.
116 WARN_ON(page_count(page) <= 1);
118 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
119 blk_run_backing_dev(bdi, page);
121 up_read(&swap_unplug_sem);
125 * swapon tell device that all the old swap contents can be discarded,
126 * to allow the swap device to optimize its wear-levelling.
128 static int discard_swap(struct swap_info_struct *si)
130 struct swap_extent *se;
131 sector_t start_block;
135 /* Do not discard the swap header page! */
136 se = &si->first_swap_extent;
137 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
138 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
140 err = blkdev_issue_discard(si->bdev, start_block,
141 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
147 list_for_each_entry(se, &si->first_swap_extent.list, list) {
148 start_block = se->start_block << (PAGE_SHIFT - 9);
149 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
151 err = blkdev_issue_discard(si->bdev, start_block,
152 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
158 return err; /* That will often be -EOPNOTSUPP */
162 * swap allocation tell device that a cluster of swap can now be discarded,
163 * to allow the swap device to optimize its wear-levelling.
165 static void discard_swap_cluster(struct swap_info_struct *si,
166 pgoff_t start_page, pgoff_t nr_pages)
168 struct swap_extent *se = si->curr_swap_extent;
169 int found_extent = 0;
172 struct list_head *lh;
174 if (se->start_page <= start_page &&
175 start_page < se->start_page + se->nr_pages) {
176 pgoff_t offset = start_page - se->start_page;
177 sector_t start_block = se->start_block + offset;
178 sector_t nr_blocks = se->nr_pages - offset;
180 if (nr_blocks > nr_pages)
181 nr_blocks = nr_pages;
182 start_page += nr_blocks;
183 nr_pages -= nr_blocks;
186 si->curr_swap_extent = se;
188 start_block <<= PAGE_SHIFT - 9;
189 nr_blocks <<= PAGE_SHIFT - 9;
190 if (blkdev_issue_discard(si->bdev, start_block,
191 nr_blocks, GFP_NOIO, DISCARD_FL_BARRIER))
196 se = list_entry(lh, struct swap_extent, list);
200 static int wait_for_discard(void *word)
206 #define SWAPFILE_CLUSTER 256
207 #define LATENCY_LIMIT 256
209 static inline unsigned long scan_swap_map(struct swap_info_struct *si,
212 unsigned long offset;
213 unsigned long scan_base;
214 unsigned long last_in_cluster = 0;
215 int latency_ration = LATENCY_LIMIT;
216 int found_free_cluster = 0;
219 * We try to cluster swap pages by allocating them sequentially
220 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
221 * way, however, we resort to first-free allocation, starting
222 * a new cluster. This prevents us from scattering swap pages
223 * all over the entire swap partition, so that we reduce
224 * overall disk seek times between swap pages. -- sct
225 * But we do now try to find an empty cluster. -Andrea
226 * And we let swap pages go all over an SSD partition. Hugh
229 si->flags += SWP_SCANNING;
230 scan_base = offset = si->cluster_next;
232 if (unlikely(!si->cluster_nr--)) {
233 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
234 si->cluster_nr = SWAPFILE_CLUSTER - 1;
237 if (si->flags & SWP_DISCARDABLE) {
239 * Start range check on racing allocations, in case
240 * they overlap the cluster we eventually decide on
241 * (we scan without swap_lock to allow preemption).
242 * It's hardly conceivable that cluster_nr could be
243 * wrapped during our scan, but don't depend on it.
245 if (si->lowest_alloc)
247 si->lowest_alloc = si->max;
248 si->highest_alloc = 0;
250 spin_unlock(&swap_lock);
253 * If seek is expensive, start searching for new cluster from
254 * start of partition, to minimize the span of allocated swap.
255 * But if seek is cheap, search from our current position, so
256 * that swap is allocated from all over the partition: if the
257 * Flash Translation Layer only remaps within limited zones,
258 * we don't want to wear out the first zone too quickly.
260 if (!(si->flags & SWP_SOLIDSTATE))
261 scan_base = offset = si->lowest_bit;
262 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
264 /* Locate the first empty (unaligned) cluster */
265 for (; last_in_cluster <= si->highest_bit; offset++) {
266 if (si->swap_map[offset])
267 last_in_cluster = offset + SWAPFILE_CLUSTER;
268 else if (offset == last_in_cluster) {
269 spin_lock(&swap_lock);
270 offset -= SWAPFILE_CLUSTER - 1;
271 si->cluster_next = offset;
272 si->cluster_nr = SWAPFILE_CLUSTER - 1;
273 found_free_cluster = 1;
276 if (unlikely(--latency_ration < 0)) {
278 latency_ration = LATENCY_LIMIT;
282 offset = si->lowest_bit;
283 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
285 /* Locate the first empty (unaligned) cluster */
286 for (; last_in_cluster < scan_base; offset++) {
287 if (si->swap_map[offset])
288 last_in_cluster = offset + SWAPFILE_CLUSTER;
289 else if (offset == last_in_cluster) {
290 spin_lock(&swap_lock);
291 offset -= SWAPFILE_CLUSTER - 1;
292 si->cluster_next = offset;
293 si->cluster_nr = SWAPFILE_CLUSTER - 1;
294 found_free_cluster = 1;
297 if (unlikely(--latency_ration < 0)) {
299 latency_ration = LATENCY_LIMIT;
304 spin_lock(&swap_lock);
305 si->cluster_nr = SWAPFILE_CLUSTER - 1;
306 si->lowest_alloc = 0;
310 if (!(si->flags & SWP_WRITEOK))
312 if (!si->highest_bit)
314 if (offset > si->highest_bit)
315 scan_base = offset = si->lowest_bit;
317 /* reuse swap entry of cache-only swap if not busy. */
318 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
320 spin_unlock(&swap_lock);
321 swap_was_freed = __try_to_reclaim_swap(si, offset);
322 spin_lock(&swap_lock);
323 /* entry was freed successfully, try to use this again */
326 goto scan; /* check next one */
329 if (si->swap_map[offset])
332 if (offset == si->lowest_bit)
334 if (offset == si->highest_bit)
337 if (si->inuse_pages == si->pages) {
338 si->lowest_bit = si->max;
341 si->swap_map[offset] = usage;
342 si->cluster_next = offset + 1;
343 si->flags -= SWP_SCANNING;
345 if (si->lowest_alloc) {
347 * Only set when SWP_DISCARDABLE, and there's a scan
348 * for a free cluster in progress or just completed.
350 if (found_free_cluster) {
352 * To optimize wear-levelling, discard the
353 * old data of the cluster, taking care not to
354 * discard any of its pages that have already
355 * been allocated by racing tasks (offset has
356 * already stepped over any at the beginning).
358 if (offset < si->highest_alloc &&
359 si->lowest_alloc <= last_in_cluster)
360 last_in_cluster = si->lowest_alloc - 1;
361 si->flags |= SWP_DISCARDING;
362 spin_unlock(&swap_lock);
364 if (offset < last_in_cluster)
365 discard_swap_cluster(si, offset,
366 last_in_cluster - offset + 1);
368 spin_lock(&swap_lock);
369 si->lowest_alloc = 0;
370 si->flags &= ~SWP_DISCARDING;
372 smp_mb(); /* wake_up_bit advises this */
373 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
375 } else if (si->flags & SWP_DISCARDING) {
377 * Delay using pages allocated by racing tasks
378 * until the whole discard has been issued. We
379 * could defer that delay until swap_writepage,
380 * but it's easier to keep this self-contained.
382 spin_unlock(&swap_lock);
383 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
384 wait_for_discard, TASK_UNINTERRUPTIBLE);
385 spin_lock(&swap_lock);
388 * Note pages allocated by racing tasks while
389 * scan for a free cluster is in progress, so
390 * that its final discard can exclude them.
392 if (offset < si->lowest_alloc)
393 si->lowest_alloc = offset;
394 if (offset > si->highest_alloc)
395 si->highest_alloc = offset;
401 spin_unlock(&swap_lock);
402 while (++offset <= si->highest_bit) {
403 if (!si->swap_map[offset]) {
404 spin_lock(&swap_lock);
407 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
408 spin_lock(&swap_lock);
411 if (unlikely(--latency_ration < 0)) {
413 latency_ration = LATENCY_LIMIT;
416 offset = si->lowest_bit;
417 while (++offset < scan_base) {
418 if (!si->swap_map[offset]) {
419 spin_lock(&swap_lock);
422 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
423 spin_lock(&swap_lock);
426 if (unlikely(--latency_ration < 0)) {
428 latency_ration = LATENCY_LIMIT;
431 spin_lock(&swap_lock);
434 si->flags -= SWP_SCANNING;
438 swp_entry_t get_swap_page(void)
440 struct swap_info_struct *si;
445 spin_lock(&swap_lock);
446 if (nr_swap_pages <= 0)
450 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
451 si = swap_info[type];
454 (!wrapped && si->prio != swap_info[next]->prio)) {
455 next = swap_list.head;
459 if (!si->highest_bit)
461 if (!(si->flags & SWP_WRITEOK))
464 swap_list.next = next;
465 /* This is called for allocating swap entry for cache */
466 offset = scan_swap_map(si, SWAP_HAS_CACHE);
468 spin_unlock(&swap_lock);
469 return swp_entry(type, offset);
471 next = swap_list.next;
476 spin_unlock(&swap_lock);
477 return (swp_entry_t) {0};
480 /* The only caller of this function is now susupend routine */
481 swp_entry_t get_swap_page_of_type(int type)
483 struct swap_info_struct *si;
486 spin_lock(&swap_lock);
487 si = swap_info[type];
488 if (si && (si->flags & SWP_WRITEOK)) {
490 /* This is called for allocating swap entry, not cache */
491 offset = scan_swap_map(si, 1);
493 spin_unlock(&swap_lock);
494 return swp_entry(type, offset);
498 spin_unlock(&swap_lock);
499 return (swp_entry_t) {0};
502 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
504 struct swap_info_struct *p;
505 unsigned long offset, type;
509 type = swp_type(entry);
510 if (type >= nr_swapfiles)
513 if (!(p->flags & SWP_USED))
515 offset = swp_offset(entry);
516 if (offset >= p->max)
518 if (!p->swap_map[offset])
520 spin_lock(&swap_lock);
524 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
527 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
530 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
533 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
538 static unsigned char swap_entry_free(struct swap_info_struct *p,
539 swp_entry_t entry, unsigned char usage)
541 unsigned long offset = swp_offset(entry);
543 unsigned char has_cache;
545 count = p->swap_map[offset];
546 has_cache = count & SWAP_HAS_CACHE;
547 count &= ~SWAP_HAS_CACHE;
549 if (usage == SWAP_HAS_CACHE) {
550 VM_BUG_ON(!has_cache);
552 } else if (count == SWAP_MAP_SHMEM) {
554 * Or we could insist on shmem.c using a special
555 * swap_shmem_free() and free_shmem_swap_and_cache()...
558 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
559 if (count == COUNT_CONTINUED) {
560 if (swap_count_continued(p, offset, count))
561 count = SWAP_MAP_MAX | COUNT_CONTINUED;
563 count = SWAP_MAP_MAX;
569 mem_cgroup_uncharge_swap(entry);
571 usage = count | has_cache;
572 p->swap_map[offset] = usage;
574 /* free if no reference */
576 if (offset < p->lowest_bit)
577 p->lowest_bit = offset;
578 if (offset > p->highest_bit)
579 p->highest_bit = offset;
580 if (swap_list.next >= 0 &&
581 p->prio > swap_info[swap_list.next]->prio)
582 swap_list.next = p->type;
591 * Caller has made sure that the swapdevice corresponding to entry
592 * is still around or has not been recycled.
594 void swap_free(swp_entry_t entry)
596 struct swap_info_struct *p;
598 p = swap_info_get(entry);
600 swap_entry_free(p, entry, 1);
601 spin_unlock(&swap_lock);
606 * Called after dropping swapcache to decrease refcnt to swap entries.
608 void swapcache_free(swp_entry_t entry, struct page *page)
610 struct swap_info_struct *p;
613 p = swap_info_get(entry);
615 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
617 mem_cgroup_uncharge_swapcache(page, entry, count != 0);
618 spin_unlock(&swap_lock);
623 * How many references to page are currently swapped out?
624 * This does not give an exact answer when swap count is continued,
625 * but does include the high COUNT_CONTINUED flag to allow for that.
627 static inline int page_swapcount(struct page *page)
630 struct swap_info_struct *p;
633 entry.val = page_private(page);
634 p = swap_info_get(entry);
636 count = swap_count(p->swap_map[swp_offset(entry)]);
637 spin_unlock(&swap_lock);
643 * We can write to an anon page without COW if there are no other references
644 * to it. And as a side-effect, free up its swap: because the old content
645 * on disk will never be read, and seeking back there to write new content
646 * later would only waste time away from clustering.
648 int reuse_swap_page(struct page *page)
652 VM_BUG_ON(!PageLocked(page));
653 count = page_mapcount(page);
654 if (count <= 1 && PageSwapCache(page)) {
655 count += page_swapcount(page);
656 if (count == 1 && !PageWriteback(page)) {
657 delete_from_swap_cache(page);
665 * If swap is getting full, or if there are no more mappings of this page,
666 * then try_to_free_swap is called to free its swap space.
668 int try_to_free_swap(struct page *page)
670 VM_BUG_ON(!PageLocked(page));
672 if (!PageSwapCache(page))
674 if (PageWriteback(page))
676 if (page_swapcount(page))
679 delete_from_swap_cache(page);
685 * Free the swap entry like above, but also try to
686 * free the page cache entry if it is the last user.
688 int free_swap_and_cache(swp_entry_t entry)
690 struct swap_info_struct *p;
691 struct page *page = NULL;
693 if (non_swap_entry(entry))
696 p = swap_info_get(entry);
698 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
699 page = find_get_page(&swapper_space, entry.val);
700 if (page && !trylock_page(page)) {
701 page_cache_release(page);
705 spin_unlock(&swap_lock);
709 * Not mapped elsewhere, or swap space full? Free it!
710 * Also recheck PageSwapCache now page is locked (above).
712 if (PageSwapCache(page) && !PageWriteback(page) &&
713 (!page_mapped(page) || vm_swap_full())) {
714 delete_from_swap_cache(page);
718 page_cache_release(page);
723 #ifdef CONFIG_HIBERNATION
725 * Find the swap type that corresponds to given device (if any).
727 * @offset - number of the PAGE_SIZE-sized block of the device, starting
728 * from 0, in which the swap header is expected to be located.
730 * This is needed for the suspend to disk (aka swsusp).
732 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
734 struct block_device *bdev = NULL;
738 bdev = bdget(device);
740 spin_lock(&swap_lock);
741 for (type = 0; type < nr_swapfiles; type++) {
742 struct swap_info_struct *sis = swap_info[type];
744 if (!(sis->flags & SWP_WRITEOK))
749 *bdev_p = bdgrab(sis->bdev);
751 spin_unlock(&swap_lock);
754 if (bdev == sis->bdev) {
755 struct swap_extent *se = &sis->first_swap_extent;
757 if (se->start_block == offset) {
759 *bdev_p = bdgrab(sis->bdev);
761 spin_unlock(&swap_lock);
767 spin_unlock(&swap_lock);
775 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
776 * corresponding to given index in swap_info (swap type).
778 sector_t swapdev_block(int type, pgoff_t offset)
780 struct block_device *bdev;
782 if ((unsigned int)type >= nr_swapfiles)
784 if (!(swap_info[type]->flags & SWP_WRITEOK))
786 return map_swap_entry(swp_entry(type, offset), &bdev);
790 * Return either the total number of swap pages of given type, or the number
791 * of free pages of that type (depending on @free)
793 * This is needed for software suspend
795 unsigned int count_swap_pages(int type, int free)
799 spin_lock(&swap_lock);
800 if ((unsigned int)type < nr_swapfiles) {
801 struct swap_info_struct *sis = swap_info[type];
803 if (sis->flags & SWP_WRITEOK) {
806 n -= sis->inuse_pages;
809 spin_unlock(&swap_lock);
812 #endif /* CONFIG_HIBERNATION */
815 * No need to decide whether this PTE shares the swap entry with others,
816 * just let do_wp_page work it out if a write is requested later - to
817 * force COW, vm_page_prot omits write permission from any private vma.
819 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
820 unsigned long addr, swp_entry_t entry, struct page *page)
822 struct mem_cgroup *ptr = NULL;
827 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
832 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
833 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
835 mem_cgroup_cancel_charge_swapin(ptr);
840 inc_mm_counter(vma->vm_mm, anon_rss);
842 set_pte_at(vma->vm_mm, addr, pte,
843 pte_mkold(mk_pte(page, vma->vm_page_prot)));
844 page_add_anon_rmap(page, vma, addr);
845 mem_cgroup_commit_charge_swapin(page, ptr);
848 * Move the page to the active list so it is not
849 * immediately swapped out again after swapon.
853 pte_unmap_unlock(pte, ptl);
858 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
859 unsigned long addr, unsigned long end,
860 swp_entry_t entry, struct page *page)
862 pte_t swp_pte = swp_entry_to_pte(entry);
867 * We don't actually need pte lock while scanning for swp_pte: since
868 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
869 * page table while we're scanning; though it could get zapped, and on
870 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
871 * of unmatched parts which look like swp_pte, so unuse_pte must
872 * recheck under pte lock. Scanning without pte lock lets it be
873 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
875 pte = pte_offset_map(pmd, addr);
878 * swapoff spends a _lot_ of time in this loop!
879 * Test inline before going to call unuse_pte.
881 if (unlikely(pte_same(*pte, swp_pte))) {
883 ret = unuse_pte(vma, pmd, addr, entry, page);
886 pte = pte_offset_map(pmd, addr);
888 } while (pte++, addr += PAGE_SIZE, addr != end);
894 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
895 unsigned long addr, unsigned long end,
896 swp_entry_t entry, struct page *page)
902 pmd = pmd_offset(pud, addr);
904 next = pmd_addr_end(addr, end);
905 if (pmd_none_or_clear_bad(pmd))
907 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
910 } while (pmd++, addr = next, addr != end);
914 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
915 unsigned long addr, unsigned long end,
916 swp_entry_t entry, struct page *page)
922 pud = pud_offset(pgd, addr);
924 next = pud_addr_end(addr, end);
925 if (pud_none_or_clear_bad(pud))
927 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
930 } while (pud++, addr = next, addr != end);
934 static int unuse_vma(struct vm_area_struct *vma,
935 swp_entry_t entry, struct page *page)
938 unsigned long addr, end, next;
942 addr = page_address_in_vma(page, vma);
946 end = addr + PAGE_SIZE;
948 addr = vma->vm_start;
952 pgd = pgd_offset(vma->vm_mm, addr);
954 next = pgd_addr_end(addr, end);
955 if (pgd_none_or_clear_bad(pgd))
957 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
960 } while (pgd++, addr = next, addr != end);
964 static int unuse_mm(struct mm_struct *mm,
965 swp_entry_t entry, struct page *page)
967 struct vm_area_struct *vma;
970 if (!down_read_trylock(&mm->mmap_sem)) {
972 * Activate page so shrink_inactive_list is unlikely to unmap
973 * its ptes while lock is dropped, so swapoff can make progress.
977 down_read(&mm->mmap_sem);
980 for (vma = mm->mmap; vma; vma = vma->vm_next) {
981 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
984 up_read(&mm->mmap_sem);
985 return (ret < 0)? ret: 0;
989 * Scan swap_map from current position to next entry still in use.
990 * Recycle to start on reaching the end, returning 0 when empty.
992 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
995 unsigned int max = si->max;
996 unsigned int i = prev;
1000 * No need for swap_lock here: we're just looking
1001 * for whether an entry is in use, not modifying it; false
1002 * hits are okay, and sys_swapoff() has already prevented new
1003 * allocations from this area (while holding swap_lock).
1012 * No entries in use at top of swap_map,
1013 * loop back to start and recheck there.
1019 count = si->swap_map[i];
1020 if (count && swap_count(count) != SWAP_MAP_BAD)
1027 * We completely avoid races by reading each swap page in advance,
1028 * and then search for the process using it. All the necessary
1029 * page table adjustments can then be made atomically.
1031 static int try_to_unuse(unsigned int type)
1033 struct swap_info_struct *si = swap_info[type];
1034 struct mm_struct *start_mm;
1035 unsigned char *swap_map;
1036 unsigned char swcount;
1043 * When searching mms for an entry, a good strategy is to
1044 * start at the first mm we freed the previous entry from
1045 * (though actually we don't notice whether we or coincidence
1046 * freed the entry). Initialize this start_mm with a hold.
1048 * A simpler strategy would be to start at the last mm we
1049 * freed the previous entry from; but that would take less
1050 * advantage of mmlist ordering, which clusters forked mms
1051 * together, child after parent. If we race with dup_mmap(), we
1052 * prefer to resolve parent before child, lest we miss entries
1053 * duplicated after we scanned child: using last mm would invert
1056 start_mm = &init_mm;
1057 atomic_inc(&init_mm.mm_users);
1060 * Keep on scanning until all entries have gone. Usually,
1061 * one pass through swap_map is enough, but not necessarily:
1062 * there are races when an instance of an entry might be missed.
1064 while ((i = find_next_to_unuse(si, i)) != 0) {
1065 if (signal_pending(current)) {
1071 * Get a page for the entry, using the existing swap
1072 * cache page if there is one. Otherwise, get a clean
1073 * page and read the swap into it.
1075 swap_map = &si->swap_map[i];
1076 entry = swp_entry(type, i);
1077 page = read_swap_cache_async(entry,
1078 GFP_HIGHUSER_MOVABLE, NULL, 0);
1081 * Either swap_duplicate() failed because entry
1082 * has been freed independently, and will not be
1083 * reused since sys_swapoff() already disabled
1084 * allocation from here, or alloc_page() failed.
1093 * Don't hold on to start_mm if it looks like exiting.
1095 if (atomic_read(&start_mm->mm_users) == 1) {
1097 start_mm = &init_mm;
1098 atomic_inc(&init_mm.mm_users);
1102 * Wait for and lock page. When do_swap_page races with
1103 * try_to_unuse, do_swap_page can handle the fault much
1104 * faster than try_to_unuse can locate the entry. This
1105 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1106 * defer to do_swap_page in such a case - in some tests,
1107 * do_swap_page and try_to_unuse repeatedly compete.
1109 wait_on_page_locked(page);
1110 wait_on_page_writeback(page);
1112 wait_on_page_writeback(page);
1115 * Remove all references to entry.
1117 swcount = *swap_map;
1118 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1119 retval = shmem_unuse(entry, page);
1120 /* page has already been unlocked and released */
1125 if (swap_count(swcount) && start_mm != &init_mm)
1126 retval = unuse_mm(start_mm, entry, page);
1128 if (swap_count(*swap_map)) {
1129 int set_start_mm = (*swap_map >= swcount);
1130 struct list_head *p = &start_mm->mmlist;
1131 struct mm_struct *new_start_mm = start_mm;
1132 struct mm_struct *prev_mm = start_mm;
1133 struct mm_struct *mm;
1135 atomic_inc(&new_start_mm->mm_users);
1136 atomic_inc(&prev_mm->mm_users);
1137 spin_lock(&mmlist_lock);
1138 while (swap_count(*swap_map) && !retval &&
1139 (p = p->next) != &start_mm->mmlist) {
1140 mm = list_entry(p, struct mm_struct, mmlist);
1141 if (!atomic_inc_not_zero(&mm->mm_users))
1143 spin_unlock(&mmlist_lock);
1149 swcount = *swap_map;
1150 if (!swap_count(swcount)) /* any usage ? */
1152 else if (mm == &init_mm)
1155 retval = unuse_mm(mm, entry, page);
1157 if (set_start_mm && *swap_map < swcount) {
1158 mmput(new_start_mm);
1159 atomic_inc(&mm->mm_users);
1163 spin_lock(&mmlist_lock);
1165 spin_unlock(&mmlist_lock);
1168 start_mm = new_start_mm;
1172 page_cache_release(page);
1177 * If a reference remains (rare), we would like to leave
1178 * the page in the swap cache; but try_to_unmap could
1179 * then re-duplicate the entry once we drop page lock,
1180 * so we might loop indefinitely; also, that page could
1181 * not be swapped out to other storage meanwhile. So:
1182 * delete from cache even if there's another reference,
1183 * after ensuring that the data has been saved to disk -
1184 * since if the reference remains (rarer), it will be
1185 * read from disk into another page. Splitting into two
1186 * pages would be incorrect if swap supported "shared
1187 * private" pages, but they are handled by tmpfs files.
1189 if (swap_count(*swap_map) &&
1190 PageDirty(page) && PageSwapCache(page)) {
1191 struct writeback_control wbc = {
1192 .sync_mode = WB_SYNC_NONE,
1195 swap_writepage(page, &wbc);
1197 wait_on_page_writeback(page);
1201 * It is conceivable that a racing task removed this page from
1202 * swap cache just before we acquired the page lock at the top,
1203 * or while we dropped it in unuse_mm(). The page might even
1204 * be back in swap cache on another swap area: that we must not
1205 * delete, since it may not have been written out to swap yet.
1207 if (PageSwapCache(page) &&
1208 likely(page_private(page) == entry.val))
1209 delete_from_swap_cache(page);
1212 * So we could skip searching mms once swap count went
1213 * to 1, we did not mark any present ptes as dirty: must
1214 * mark page dirty so shrink_page_list will preserve it.
1218 page_cache_release(page);
1221 * Make sure that we aren't completely killing
1222 * interactive performance.
1232 * After a successful try_to_unuse, if no swap is now in use, we know
1233 * we can empty the mmlist. swap_lock must be held on entry and exit.
1234 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1235 * added to the mmlist just after page_duplicate - before would be racy.
1237 static void drain_mmlist(void)
1239 struct list_head *p, *next;
1242 for (type = 0; type < nr_swapfiles; type++)
1243 if (swap_info[type]->inuse_pages)
1245 spin_lock(&mmlist_lock);
1246 list_for_each_safe(p, next, &init_mm.mmlist)
1248 spin_unlock(&mmlist_lock);
1252 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1253 * corresponds to page offset for the specified swap entry.
1254 * Note that the type of this function is sector_t, but it returns page offset
1255 * into the bdev, not sector offset.
1257 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1259 struct swap_info_struct *sis;
1260 struct swap_extent *start_se;
1261 struct swap_extent *se;
1264 sis = swap_info[swp_type(entry)];
1267 offset = swp_offset(entry);
1268 start_se = sis->curr_swap_extent;
1272 struct list_head *lh;
1274 if (se->start_page <= offset &&
1275 offset < (se->start_page + se->nr_pages)) {
1276 return se->start_block + (offset - se->start_page);
1279 se = list_entry(lh, struct swap_extent, list);
1280 sis->curr_swap_extent = se;
1281 BUG_ON(se == start_se); /* It *must* be present */
1286 * Returns the page offset into bdev for the specified page's swap entry.
1288 sector_t map_swap_page(struct page *page, struct block_device **bdev)
1291 entry.val = page_private(page);
1292 return map_swap_entry(entry, bdev);
1296 * Free all of a swapdev's extent information
1298 static void destroy_swap_extents(struct swap_info_struct *sis)
1300 while (!list_empty(&sis->first_swap_extent.list)) {
1301 struct swap_extent *se;
1303 se = list_entry(sis->first_swap_extent.list.next,
1304 struct swap_extent, list);
1305 list_del(&se->list);
1311 * Add a block range (and the corresponding page range) into this swapdev's
1312 * extent list. The extent list is kept sorted in page order.
1314 * This function rather assumes that it is called in ascending page order.
1317 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1318 unsigned long nr_pages, sector_t start_block)
1320 struct swap_extent *se;
1321 struct swap_extent *new_se;
1322 struct list_head *lh;
1324 if (start_page == 0) {
1325 se = &sis->first_swap_extent;
1326 sis->curr_swap_extent = se;
1328 se->nr_pages = nr_pages;
1329 se->start_block = start_block;
1332 lh = sis->first_swap_extent.list.prev; /* Highest extent */
1333 se = list_entry(lh, struct swap_extent, list);
1334 BUG_ON(se->start_page + se->nr_pages != start_page);
1335 if (se->start_block + se->nr_pages == start_block) {
1337 se->nr_pages += nr_pages;
1343 * No merge. Insert a new extent, preserving ordering.
1345 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1348 new_se->start_page = start_page;
1349 new_se->nr_pages = nr_pages;
1350 new_se->start_block = start_block;
1352 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1357 * A `swap extent' is a simple thing which maps a contiguous range of pages
1358 * onto a contiguous range of disk blocks. An ordered list of swap extents
1359 * is built at swapon time and is then used at swap_writepage/swap_readpage
1360 * time for locating where on disk a page belongs.
1362 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1363 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1364 * swap files identically.
1366 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1367 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1368 * swapfiles are handled *identically* after swapon time.
1370 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1371 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1372 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1373 * requirements, they are simply tossed out - we will never use those blocks
1376 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1377 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1378 * which will scribble on the fs.
1380 * The amount of disk space which a single swap extent represents varies.
1381 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1382 * extents in the list. To avoid much list walking, we cache the previous
1383 * search location in `curr_swap_extent', and start new searches from there.
1384 * This is extremely effective. The average number of iterations in
1385 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1387 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1389 struct inode *inode;
1390 unsigned blocks_per_page;
1391 unsigned long page_no;
1393 sector_t probe_block;
1394 sector_t last_block;
1395 sector_t lowest_block = -1;
1396 sector_t highest_block = 0;
1400 inode = sis->swap_file->f_mapping->host;
1401 if (S_ISBLK(inode->i_mode)) {
1402 ret = add_swap_extent(sis, 0, sis->max, 0);
1407 blkbits = inode->i_blkbits;
1408 blocks_per_page = PAGE_SIZE >> blkbits;
1411 * Map all the blocks into the extent list. This code doesn't try
1416 last_block = i_size_read(inode) >> blkbits;
1417 while ((probe_block + blocks_per_page) <= last_block &&
1418 page_no < sis->max) {
1419 unsigned block_in_page;
1420 sector_t first_block;
1422 first_block = bmap(inode, probe_block);
1423 if (first_block == 0)
1427 * It must be PAGE_SIZE aligned on-disk
1429 if (first_block & (blocks_per_page - 1)) {
1434 for (block_in_page = 1; block_in_page < blocks_per_page;
1438 block = bmap(inode, probe_block + block_in_page);
1441 if (block != first_block + block_in_page) {
1448 first_block >>= (PAGE_SHIFT - blkbits);
1449 if (page_no) { /* exclude the header page */
1450 if (first_block < lowest_block)
1451 lowest_block = first_block;
1452 if (first_block > highest_block)
1453 highest_block = first_block;
1457 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1459 ret = add_swap_extent(sis, page_no, 1, first_block);
1464 probe_block += blocks_per_page;
1469 *span = 1 + highest_block - lowest_block;
1471 page_no = 1; /* force Empty message */
1473 sis->pages = page_no - 1;
1474 sis->highest_bit = page_no - 1;
1478 printk(KERN_ERR "swapon: swapfile has holes\n");
1483 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1485 struct swap_info_struct *p = NULL;
1486 unsigned char *swap_map;
1487 struct file *swap_file, *victim;
1488 struct address_space *mapping;
1489 struct inode *inode;
1494 if (!capable(CAP_SYS_ADMIN))
1497 pathname = getname(specialfile);
1498 err = PTR_ERR(pathname);
1499 if (IS_ERR(pathname))
1502 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1504 err = PTR_ERR(victim);
1508 mapping = victim->f_mapping;
1510 spin_lock(&swap_lock);
1511 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1512 p = swap_info[type];
1513 if (p->flags & SWP_WRITEOK) {
1514 if (p->swap_file->f_mapping == mapping)
1521 spin_unlock(&swap_lock);
1524 if (!security_vm_enough_memory(p->pages))
1525 vm_unacct_memory(p->pages);
1528 spin_unlock(&swap_lock);
1532 swap_list.head = p->next;
1534 swap_info[prev]->next = p->next;
1535 if (type == swap_list.next) {
1536 /* just pick something that's safe... */
1537 swap_list.next = swap_list.head;
1540 for (i = p->next; i >= 0; i = swap_info[i]->next)
1541 swap_info[i]->prio = p->prio--;
1544 nr_swap_pages -= p->pages;
1545 total_swap_pages -= p->pages;
1546 p->flags &= ~SWP_WRITEOK;
1547 spin_unlock(&swap_lock);
1549 current->flags |= PF_OOM_ORIGIN;
1550 err = try_to_unuse(type);
1551 current->flags &= ~PF_OOM_ORIGIN;
1554 /* re-insert swap space back into swap_list */
1555 spin_lock(&swap_lock);
1557 p->prio = --least_priority;
1559 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1560 if (p->prio >= swap_info[i]->prio)
1566 swap_list.head = swap_list.next = type;
1568 swap_info[prev]->next = type;
1569 nr_swap_pages += p->pages;
1570 total_swap_pages += p->pages;
1571 p->flags |= SWP_WRITEOK;
1572 spin_unlock(&swap_lock);
1576 /* wait for any unplug function to finish */
1577 down_write(&swap_unplug_sem);
1578 up_write(&swap_unplug_sem);
1580 destroy_swap_extents(p);
1581 if (p->flags & SWP_CONTINUED)
1582 free_swap_count_continuations(p);
1584 mutex_lock(&swapon_mutex);
1585 spin_lock(&swap_lock);
1588 /* wait for anyone still in scan_swap_map */
1589 p->highest_bit = 0; /* cuts scans short */
1590 while (p->flags >= SWP_SCANNING) {
1591 spin_unlock(&swap_lock);
1592 schedule_timeout_uninterruptible(1);
1593 spin_lock(&swap_lock);
1596 swap_file = p->swap_file;
1597 p->swap_file = NULL;
1599 swap_map = p->swap_map;
1602 spin_unlock(&swap_lock);
1603 mutex_unlock(&swapon_mutex);
1605 /* Destroy swap account informatin */
1606 swap_cgroup_swapoff(type);
1608 inode = mapping->host;
1609 if (S_ISBLK(inode->i_mode)) {
1610 struct block_device *bdev = I_BDEV(inode);
1611 set_blocksize(bdev, p->old_block_size);
1614 mutex_lock(&inode->i_mutex);
1615 inode->i_flags &= ~S_SWAPFILE;
1616 mutex_unlock(&inode->i_mutex);
1618 filp_close(swap_file, NULL);
1622 filp_close(victim, NULL);
1627 #ifdef CONFIG_PROC_FS
1629 static void *swap_start(struct seq_file *swap, loff_t *pos)
1631 struct swap_info_struct *si;
1635 mutex_lock(&swapon_mutex);
1638 return SEQ_START_TOKEN;
1640 for (type = 0; type < nr_swapfiles; type++) {
1641 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1642 si = swap_info[type];
1643 if (!(si->flags & SWP_USED) || !si->swap_map)
1652 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1654 struct swap_info_struct *si = v;
1657 if (v == SEQ_START_TOKEN)
1660 type = si->type + 1;
1662 for (; type < nr_swapfiles; type++) {
1663 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1664 si = swap_info[type];
1665 if (!(si->flags & SWP_USED) || !si->swap_map)
1674 static void swap_stop(struct seq_file *swap, void *v)
1676 mutex_unlock(&swapon_mutex);
1679 static int swap_show(struct seq_file *swap, void *v)
1681 struct swap_info_struct *si = v;
1685 if (si == SEQ_START_TOKEN) {
1686 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1690 file = si->swap_file;
1691 len = seq_path(swap, &file->f_path, " \t\n\\");
1692 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1693 len < 40 ? 40 - len : 1, " ",
1694 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1695 "partition" : "file\t",
1696 si->pages << (PAGE_SHIFT - 10),
1697 si->inuse_pages << (PAGE_SHIFT - 10),
1702 static const struct seq_operations swaps_op = {
1703 .start = swap_start,
1709 static int swaps_open(struct inode *inode, struct file *file)
1711 return seq_open(file, &swaps_op);
1714 static const struct file_operations proc_swaps_operations = {
1717 .llseek = seq_lseek,
1718 .release = seq_release,
1721 static int __init procswaps_init(void)
1723 proc_create("swaps", 0, NULL, &proc_swaps_operations);
1726 __initcall(procswaps_init);
1727 #endif /* CONFIG_PROC_FS */
1729 #ifdef MAX_SWAPFILES_CHECK
1730 static int __init max_swapfiles_check(void)
1732 MAX_SWAPFILES_CHECK();
1735 late_initcall(max_swapfiles_check);
1739 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1741 * The swapon system call
1743 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
1745 struct swap_info_struct *p;
1747 struct block_device *bdev = NULL;
1748 struct file *swap_file = NULL;
1749 struct address_space *mapping;
1753 union swap_header *swap_header = NULL;
1754 unsigned int nr_good_pages = 0;
1757 unsigned long maxpages = 1;
1758 unsigned long swapfilepages;
1759 unsigned char *swap_map = NULL;
1760 struct page *page = NULL;
1761 struct inode *inode = NULL;
1764 if (!capable(CAP_SYS_ADMIN))
1767 p = kzalloc(sizeof(*p), GFP_KERNEL);
1771 spin_lock(&swap_lock);
1772 for (type = 0; type < nr_swapfiles; type++) {
1773 if (!(swap_info[type]->flags & SWP_USED))
1777 if (type >= MAX_SWAPFILES) {
1778 spin_unlock(&swap_lock);
1782 if (type >= nr_swapfiles) {
1784 swap_info[type] = p;
1786 * Write swap_info[type] before nr_swapfiles, in case a
1787 * racing procfs swap_start() or swap_next() is reading them.
1788 * (We never shrink nr_swapfiles, we never free this entry.)
1794 p = swap_info[type];
1796 * Do not memset this entry: a racing procfs swap_next()
1797 * would be relying on p->type to remain valid.
1800 INIT_LIST_HEAD(&p->first_swap_extent.list);
1801 p->flags = SWP_USED;
1803 spin_unlock(&swap_lock);
1805 name = getname(specialfile);
1806 error = PTR_ERR(name);
1811 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1812 error = PTR_ERR(swap_file);
1813 if (IS_ERR(swap_file)) {
1818 p->swap_file = swap_file;
1819 mapping = swap_file->f_mapping;
1820 inode = mapping->host;
1823 for (i = 0; i < nr_swapfiles; i++) {
1824 struct swap_info_struct *q = swap_info[i];
1826 if (i == type || !q->swap_file)
1828 if (mapping == q->swap_file->f_mapping)
1833 if (S_ISBLK(inode->i_mode)) {
1834 bdev = I_BDEV(inode);
1835 error = bd_claim(bdev, sys_swapon);
1841 p->old_block_size = block_size(bdev);
1842 error = set_blocksize(bdev, PAGE_SIZE);
1846 } else if (S_ISREG(inode->i_mode)) {
1847 p->bdev = inode->i_sb->s_bdev;
1848 mutex_lock(&inode->i_mutex);
1850 if (IS_SWAPFILE(inode)) {
1858 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1861 * Read the swap header.
1863 if (!mapping->a_ops->readpage) {
1867 page = read_mapping_page(mapping, 0, swap_file);
1869 error = PTR_ERR(page);
1872 swap_header = kmap(page);
1874 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1875 printk(KERN_ERR "Unable to find swap-space signature\n");
1880 /* swap partition endianess hack... */
1881 if (swab32(swap_header->info.version) == 1) {
1882 swab32s(&swap_header->info.version);
1883 swab32s(&swap_header->info.last_page);
1884 swab32s(&swap_header->info.nr_badpages);
1885 for (i = 0; i < swap_header->info.nr_badpages; i++)
1886 swab32s(&swap_header->info.badpages[i]);
1888 /* Check the swap header's sub-version */
1889 if (swap_header->info.version != 1) {
1891 "Unable to handle swap header version %d\n",
1892 swap_header->info.version);
1898 p->cluster_next = 1;
1902 * Find out how many pages are allowed for a single swap
1903 * device. There are two limiting factors: 1) the number of
1904 * bits for the swap offset in the swp_entry_t type and
1905 * 2) the number of bits in the a swap pte as defined by
1906 * the different architectures. In order to find the
1907 * largest possible bit mask a swap entry with swap type 0
1908 * and swap offset ~0UL is created, encoded to a swap pte,
1909 * decoded to a swp_entry_t again and finally the swap
1910 * offset is extracted. This will mask all the bits from
1911 * the initial ~0UL mask that can't be encoded in either
1912 * the swp_entry_t or the architecture definition of a
1915 maxpages = swp_offset(pte_to_swp_entry(
1916 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1917 if (maxpages > swap_header->info.last_page)
1918 maxpages = swap_header->info.last_page;
1919 p->highest_bit = maxpages - 1;
1924 if (swapfilepages && maxpages > swapfilepages) {
1926 "Swap area shorter than signature indicates\n");
1929 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1931 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1934 /* OK, set up the swap map and apply the bad block list */
1935 swap_map = vmalloc(maxpages);
1941 memset(swap_map, 0, maxpages);
1942 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1943 int page_nr = swap_header->info.badpages[i];
1944 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
1948 swap_map[page_nr] = SWAP_MAP_BAD;
1951 error = swap_cgroup_swapon(type, maxpages);
1955 nr_good_pages = swap_header->info.last_page -
1956 swap_header->info.nr_badpages -
1957 1 /* header page */;
1959 if (nr_good_pages) {
1960 swap_map[0] = SWAP_MAP_BAD;
1962 p->pages = nr_good_pages;
1963 nr_extents = setup_swap_extents(p, &span);
1964 if (nr_extents < 0) {
1968 nr_good_pages = p->pages;
1970 if (!nr_good_pages) {
1971 printk(KERN_WARNING "Empty swap-file\n");
1977 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
1978 p->flags |= SWP_SOLIDSTATE;
1979 p->cluster_next = 1 + (random32() % p->highest_bit);
1981 if (discard_swap(p) == 0)
1982 p->flags |= SWP_DISCARDABLE;
1985 mutex_lock(&swapon_mutex);
1986 spin_lock(&swap_lock);
1987 if (swap_flags & SWAP_FLAG_PREFER)
1989 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1991 p->prio = --least_priority;
1992 p->swap_map = swap_map;
1993 p->flags |= SWP_WRITEOK;
1994 nr_swap_pages += nr_good_pages;
1995 total_swap_pages += nr_good_pages;
1997 printk(KERN_INFO "Adding %uk swap on %s. "
1998 "Priority:%d extents:%d across:%lluk %s%s\n",
1999 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
2000 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2001 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2002 (p->flags & SWP_DISCARDABLE) ? "D" : "");
2004 /* insert swap space into swap_list: */
2006 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
2007 if (p->prio >= swap_info[i]->prio)
2013 swap_list.head = swap_list.next = type;
2015 swap_info[prev]->next = type;
2016 spin_unlock(&swap_lock);
2017 mutex_unlock(&swapon_mutex);
2022 set_blocksize(bdev, p->old_block_size);
2025 destroy_swap_extents(p);
2026 swap_cgroup_swapoff(type);
2028 spin_lock(&swap_lock);
2029 p->swap_file = NULL;
2031 spin_unlock(&swap_lock);
2034 filp_close(swap_file, NULL);
2036 if (page && !IS_ERR(page)) {
2038 page_cache_release(page);
2044 inode->i_flags |= S_SWAPFILE;
2045 mutex_unlock(&inode->i_mutex);
2050 void si_swapinfo(struct sysinfo *val)
2053 unsigned long nr_to_be_unused = 0;
2055 spin_lock(&swap_lock);
2056 for (type = 0; type < nr_swapfiles; type++) {
2057 struct swap_info_struct *si = swap_info[type];
2059 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2060 nr_to_be_unused += si->inuse_pages;
2062 val->freeswap = nr_swap_pages + nr_to_be_unused;
2063 val->totalswap = total_swap_pages + nr_to_be_unused;
2064 spin_unlock(&swap_lock);
2068 * Verify that a swap entry is valid and increment its swap map count.
2070 * Returns error code in following case.
2072 * - swp_entry is invalid -> EINVAL
2073 * - swp_entry is migration entry -> EINVAL
2074 * - swap-cache reference is requested but there is already one. -> EEXIST
2075 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2076 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2078 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2080 struct swap_info_struct *p;
2081 unsigned long offset, type;
2082 unsigned char count;
2083 unsigned char has_cache;
2086 if (non_swap_entry(entry))
2089 type = swp_type(entry);
2090 if (type >= nr_swapfiles)
2092 p = swap_info[type];
2093 offset = swp_offset(entry);
2095 spin_lock(&swap_lock);
2096 if (unlikely(offset >= p->max))
2099 count = p->swap_map[offset];
2100 has_cache = count & SWAP_HAS_CACHE;
2101 count &= ~SWAP_HAS_CACHE;
2104 if (usage == SWAP_HAS_CACHE) {
2106 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2107 if (!has_cache && count)
2108 has_cache = SWAP_HAS_CACHE;
2109 else if (has_cache) /* someone else added cache */
2111 else /* no users remaining */
2114 } else if (count || has_cache) {
2116 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2118 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2120 else if (swap_count_continued(p, offset, count))
2121 count = COUNT_CONTINUED;
2125 err = -ENOENT; /* unused swap entry */
2127 p->swap_map[offset] = count | has_cache;
2130 spin_unlock(&swap_lock);
2135 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2140 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2141 * (in which case its reference count is never incremented).
2143 void swap_shmem_alloc(swp_entry_t entry)
2145 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2149 * increase reference count of swap entry by 1.
2151 int swap_duplicate(swp_entry_t entry)
2155 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2156 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2161 * @entry: swap entry for which we allocate swap cache.
2163 * Called when allocating swap cache for existing swap entry,
2164 * This can return error codes. Returns 0 at success.
2165 * -EBUSY means there is a swap cache.
2166 * Note: return code is different from swap_duplicate().
2168 int swapcache_prepare(swp_entry_t entry)
2170 return __swap_duplicate(entry, SWAP_HAS_CACHE);
2174 * swap_lock prevents swap_map being freed. Don't grab an extra
2175 * reference on the swaphandle, it doesn't matter if it becomes unused.
2177 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2179 struct swap_info_struct *si;
2180 int our_page_cluster = page_cluster;
2181 pgoff_t target, toff;
2185 if (!our_page_cluster) /* no readahead */
2188 si = swap_info[swp_type(entry)];
2189 target = swp_offset(entry);
2190 base = (target >> our_page_cluster) << our_page_cluster;
2191 end = base + (1 << our_page_cluster);
2192 if (!base) /* first page is swap header */
2195 spin_lock(&swap_lock);
2196 if (end > si->max) /* don't go beyond end of map */
2199 /* Count contiguous allocated slots above our target */
2200 for (toff = target; ++toff < end; nr_pages++) {
2201 /* Don't read in free or bad pages */
2202 if (!si->swap_map[toff])
2204 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2207 /* Count contiguous allocated slots below our target */
2208 for (toff = target; --toff >= base; nr_pages++) {
2209 /* Don't read in free or bad pages */
2210 if (!si->swap_map[toff])
2212 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2215 spin_unlock(&swap_lock);
2218 * Indicate starting offset, and return number of pages to get:
2219 * if only 1, say 0, since there's then no readahead to be done.
2222 return nr_pages? ++nr_pages: 0;
2226 * add_swap_count_continuation - called when a swap count is duplicated
2227 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2228 * page of the original vmalloc'ed swap_map, to hold the continuation count
2229 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2230 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2232 * These continuation pages are seldom referenced: the common paths all work
2233 * on the original swap_map, only referring to a continuation page when the
2234 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2236 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2237 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2238 * can be called after dropping locks.
2240 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2242 struct swap_info_struct *si;
2245 struct page *list_page;
2247 unsigned char count;
2250 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2251 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2253 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2255 si = swap_info_get(entry);
2258 * An acceptable race has occurred since the failing
2259 * __swap_duplicate(): the swap entry has been freed,
2260 * perhaps even the whole swap_map cleared for swapoff.
2265 offset = swp_offset(entry);
2266 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2268 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2270 * The higher the swap count, the more likely it is that tasks
2271 * will race to add swap count continuation: we need to avoid
2272 * over-provisioning.
2278 spin_unlock(&swap_lock);
2283 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2284 * no architecture is using highmem pages for kernel pagetables: so it
2285 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2287 head = vmalloc_to_page(si->swap_map + offset);
2288 offset &= ~PAGE_MASK;
2291 * Page allocation does not initialize the page's lru field,
2292 * but it does always reset its private field.
2294 if (!page_private(head)) {
2295 BUG_ON(count & COUNT_CONTINUED);
2296 INIT_LIST_HEAD(&head->lru);
2297 set_page_private(head, SWP_CONTINUED);
2298 si->flags |= SWP_CONTINUED;
2301 list_for_each_entry(list_page, &head->lru, lru) {
2305 * If the previous map said no continuation, but we've found
2306 * a continuation page, free our allocation and use this one.
2308 if (!(count & COUNT_CONTINUED))
2311 map = kmap_atomic(list_page, KM_USER0) + offset;
2313 kunmap_atomic(map, KM_USER0);
2316 * If this continuation count now has some space in it,
2317 * free our allocation and use this one.
2319 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2323 list_add_tail(&page->lru, &head->lru);
2324 page = NULL; /* now it's attached, don't free it */
2326 spin_unlock(&swap_lock);
2334 * swap_count_continued - when the original swap_map count is incremented
2335 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2336 * into, carry if so, or else fail until a new continuation page is allocated;
2337 * when the original swap_map count is decremented from 0 with continuation,
2338 * borrow from the continuation and report whether it still holds more.
2339 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2341 static bool swap_count_continued(struct swap_info_struct *si,
2342 pgoff_t offset, unsigned char count)
2348 head = vmalloc_to_page(si->swap_map + offset);
2349 if (page_private(head) != SWP_CONTINUED) {
2350 BUG_ON(count & COUNT_CONTINUED);
2351 return false; /* need to add count continuation */
2354 offset &= ~PAGE_MASK;
2355 page = list_entry(head->lru.next, struct page, lru);
2356 map = kmap_atomic(page, KM_USER0) + offset;
2358 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2359 goto init_map; /* jump over SWAP_CONT_MAX checks */
2361 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2363 * Think of how you add 1 to 999
2365 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2366 kunmap_atomic(map, KM_USER0);
2367 page = list_entry(page->lru.next, struct page, lru);
2368 BUG_ON(page == head);
2369 map = kmap_atomic(page, KM_USER0) + offset;
2371 if (*map == SWAP_CONT_MAX) {
2372 kunmap_atomic(map, KM_USER0);
2373 page = list_entry(page->lru.next, struct page, lru);
2375 return false; /* add count continuation */
2376 map = kmap_atomic(page, KM_USER0) + offset;
2377 init_map: *map = 0; /* we didn't zero the page */
2380 kunmap_atomic(map, KM_USER0);
2381 page = list_entry(page->lru.prev, struct page, lru);
2382 while (page != head) {
2383 map = kmap_atomic(page, KM_USER0) + offset;
2384 *map = COUNT_CONTINUED;
2385 kunmap_atomic(map, KM_USER0);
2386 page = list_entry(page->lru.prev, struct page, lru);
2388 return true; /* incremented */
2390 } else { /* decrementing */
2392 * Think of how you subtract 1 from 1000
2394 BUG_ON(count != COUNT_CONTINUED);
2395 while (*map == COUNT_CONTINUED) {
2396 kunmap_atomic(map, KM_USER0);
2397 page = list_entry(page->lru.next, struct page, lru);
2398 BUG_ON(page == head);
2399 map = kmap_atomic(page, KM_USER0) + offset;
2405 kunmap_atomic(map, KM_USER0);
2406 page = list_entry(page->lru.prev, struct page, lru);
2407 while (page != head) {
2408 map = kmap_atomic(page, KM_USER0) + offset;
2409 *map = SWAP_CONT_MAX | count;
2410 count = COUNT_CONTINUED;
2411 kunmap_atomic(map, KM_USER0);
2412 page = list_entry(page->lru.prev, struct page, lru);
2414 return count == COUNT_CONTINUED;
2419 * free_swap_count_continuations - swapoff free all the continuation pages
2420 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2422 static void free_swap_count_continuations(struct swap_info_struct *si)
2426 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2428 head = vmalloc_to_page(si->swap_map + offset);
2429 if (page_private(head)) {
2430 struct list_head *this, *next;
2431 list_for_each_safe(this, next, &head->lru) {
2433 page = list_entry(this, struct page, lru);