/* * linux/mm/swapfile.c * * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds * Swap reorganised 29.12.95, Stephen Tweedie */ #include <linux/mm.h> #include <linux/hugetlb.h> #include <linux/mman.h> #include <linux/slab.h> #include <linux/kernel_stat.h> #include <linux/swap.h> #include <linux/vmalloc.h> #include <linux/pagemap.h> #include <linux/namei.h> #include <linux/shm.h> #include <linux/blkdev.h> #include <linux/random.h> #include <linux/writeback.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> #include <linux/init.h> #include <linux/module.h> #include <linux/ksm.h> #include <linux/rmap.h> #include <linux/security.h> #include <linux/backing-dev.h> #include <linux/mutex.h> #include <linux/capability.h> #include <linux/syscalls.h> #include <linux/memcontrol.h> #include <asm/pgtable.h> #include <asm/tlbflush.h> #include <linux/swapops.h> #include <linux/page_cgroup.h> static bool swap_count_continued(struct swap_info_struct *, pgoff_t, unsigned char); static void free_swap_count_continuations(struct swap_info_struct *); static sector_t map_swap_entry(swp_entry_t, struct block_device**); static DEFINE_SPINLOCK(swap_lock); static unsigned int nr_swapfiles; long nr_swap_pages; long total_swap_pages; static int least_priority; static bool swap_for_hibernation; static const char Bad_file[] = "Bad swap file entry "; static const char Unused_file[] = "Unused swap file entry "; static const char Bad_offset[] = "Bad swap offset entry "; static const char Unused_offset[] = "Unused swap offset entry "; static struct swap_list_t swap_list = {-1, -1}; static struct swap_info_struct *swap_info[MAX_SWAPFILES]; static DEFINE_MUTEX(swapon_mutex); static inline unsigned char swap_count(unsigned char ent) { return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */ } /* returns 1 if swap entry is freed */ static int __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset) { swp_entry_t entry = swp_entry(si->type, offset); struct page *page; int ret = 0; page = find_get_page(&swapper_space, entry.val); if (!page) return 0; /* * This function is called from scan_swap_map() and it's called * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here. * We have to use trylock for avoiding deadlock. This is a special * case and you should use try_to_free_swap() with explicit lock_page() * in usual operations. */ if (trylock_page(page)) { ret = try_to_free_swap(page); unlock_page(page); } page_cache_release(page); return ret; } /* * We need this because the bdev->unplug_fn can sleep and we cannot * hold swap_lock while calling the unplug_fn. And swap_lock * cannot be turned into a mutex. */ static DECLARE_RWSEM(swap_unplug_sem); void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page) { swp_entry_t entry; down_read(&swap_unplug_sem); entry.val = page_private(page); if (PageSwapCache(page)) { struct block_device *bdev = swap_info[swp_type(entry)]->bdev; struct backing_dev_info *bdi; /* * If the page is removed from swapcache from under us (with a * racy try_to_unuse/swapoff) we need an additional reference * count to avoid reading garbage from page_private(page) above. * If the WARN_ON triggers during a swapoff it maybe the race * condition and it's harmless. However if it triggers without * swapoff it signals a problem. */ WARN_ON(page_count(page) <= 1); bdi = bdev->bd_inode->i_mapping->backing_dev_info; blk_run_backing_dev(bdi, page); } up_read(&swap_unplug_sem); } /* * swapon tell device that all the old swap contents can be discarded, * to allow the swap device to optimize its wear-levelling. */ static int discard_swap(struct swap_info_struct *si) { struct swap_extent *se; sector_t start_block; sector_t nr_blocks; int err = 0; /* Do not discard the swap header page! */ se = &si->first_swap_extent; start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); if (nr_blocks) { err = blkdev_issue_discard(si->bdev, start_block, nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER); if (err) return err; cond_resched(); } list_for_each_entry(se, &si->first_swap_extent.list, list) { start_block = se->start_block << (PAGE_SHIFT - 9); nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); err = blkdev_issue_discard(si->bdev, start_block, nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER); if (err) break; cond_resched(); } return err; /* That will often be -EOPNOTSUPP */ } /* * swap allocation tell device that a cluster of swap can now be discarded, * to allow the swap device to optimize its wear-levelling. */ static void discard_swap_cluster(struct swap_info_struct *si, pgoff_t start_page, pgoff_t nr_pages) { struct swap_extent *se = si->curr_swap_extent; int found_extent = 0; while (nr_pages) { struct list_head *lh; if (se->start_page <= start_page && start_page < se->start_page + se->nr_pages) { pgoff_t offset = start_page - se->start_page; sector_t start_block = se->start_block + offset; sector_t nr_blocks = se->nr_pages - offset; if (nr_blocks > nr_pages) nr_blocks = nr_pages; start_page += nr_blocks; nr_pages -= nr_blocks; if (!found_extent++) si->curr_swap_extent = se; start_block <<= PAGE_SHIFT - 9; nr_blocks <<= PAGE_SHIFT - 9; if (blkdev_issue_discard(si->bdev, start_block, nr_blocks, GFP_NOIO, BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER)) break; } lh = se->list.next; se = list_entry(lh, struct swap_extent, list); } } static int wait_for_discard(void *word) { schedule(); return 0; } #define SWAPFILE_CLUSTER 256 #define LATENCY_LIMIT 256 static inline unsigned long scan_swap_map(struct swap_info_struct *si, unsigned char usage) { unsigned long offset; unsigned long scan_base; unsigned long last_in_cluster = 0; int latency_ration = LATENCY_LIMIT; int found_free_cluster = 0; /* * We try to cluster swap pages by allocating them sequentially * in swap. Once we've allocated SWAPFILE_CLUSTER pages this * way, however, we resort to first-free allocation, starting * a new cluster. This prevents us from scattering swap pages * all over the entire swap partition, so that we reduce * overall disk seek times between swap pages. -- sct * But we do now try to find an empty cluster. -Andrea * And we let swap pages go all over an SSD partition. Hugh */ si->flags += SWP_SCANNING; scan_base = offset = si->cluster_next; if (unlikely(!si->cluster_nr--)) { if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { si->cluster_nr = SWAPFILE_CLUSTER - 1; goto checks; } if (si->flags & SWP_DISCARDABLE) { /* * Start range check on racing allocations, in case * they overlap the cluster we eventually decide on * (we scan without swap_lock to allow preemption). * It's hardly conceivable that cluster_nr could be * wrapped during our scan, but don't depend on it. */ if (si->lowest_alloc) goto checks; si->lowest_alloc = si->max; si->highest_alloc = 0; } spin_unlock(&swap_lock); /* * If seek is expensive, start searching for new cluster from * start of partition, to minimize the span of allocated swap. * But if seek is cheap, search from our current position, so * that swap is allocated from all over the partition: if the * Flash Translation Layer only remaps within limited zones, * we don't want to wear out the first zone too quickly. */ if (!(si->flags & SWP_SOLIDSTATE)) scan_base = offset = si->lowest_bit; last_in_cluster = offset + SWAPFILE_CLUSTER - 1; /* Locate the first empty (unaligned) cluster */ for (; last_in_cluster <= si->highest_bit; offset++) { if (si->swap_map[offset]) last_in_cluster = offset + SWAPFILE_CLUSTER; else if (offset == last_in_cluster) { spin_lock(&swap_lock); offset -= SWAPFILE_CLUSTER - 1; si->cluster_next = offset; si->cluster_nr = SWAPFILE_CLUSTER - 1; found_free_cluster = 1; goto checks; } if (unlikely(--latency_ration < 0)) { cond_resched(); latency_ration = LATENCY_LIMIT; } } offset = si->lowest_bit; last_in_cluster = offset + SWAPFILE_CLUSTER - 1; /* Locate the first empty (unaligned) cluster */ for (; last_in_cluster < scan_base; offset++) { if (si->swap_map[offset]) last_in_cluster = offset + SWAPFILE_CLUSTER; else if (offset == last_in_cluster) { spin_lock(&swap_lock); offset -= SWAPFILE_CLUSTER - 1; si->cluster_next = offset; si->cluster_nr = SWAPFILE_CLUSTER - 1; found_free_cluster = 1; goto checks; } if (unlikely(--latency_ration < 0)) { cond_resched(); latency_ration = LATENCY_LIMIT; } } offset = scan_base; spin_lock(&swap_lock); si->cluster_nr = SWAPFILE_CLUSTER - 1; si->lowest_alloc = 0; } checks: if (!(si->flags & SWP_WRITEOK)) goto no_page; if (!si->highest_bit) goto no_page; if (offset > si->highest_bit) scan_base = offset = si->lowest_bit; /* reuse swap entry of cache-only swap if not hibernation. */ if (vm_swap_full() && usage == SWAP_HAS_CACHE && si->swap_map[offset] == SWAP_HAS_CACHE) { int swap_was_freed; spin_unlock(&swap_lock); swap_was_freed = __try_to_reclaim_swap(si, offset); spin_lock(&swap_lock); /* entry was freed successfully, try to use this again */ if (swap_was_freed) goto checks; goto scan; /* check next one */ } if (si->swap_map[offset]) goto scan; if (offset == si->lowest_bit) si->lowest_bit++; if (offset == si->highest_bit) si->highest_bit--; si->inuse_pages++; if (si->inuse_pages == si->pages) { si->lowest_bit = si->max; si->highest_bit = 0; } si->swap_map[offset] = usage; si->cluster_next = offset + 1; si->flags -= SWP_SCANNING; if (si->lowest_alloc) { /* * Only set when SWP_DISCARDABLE, and there's a scan * for a free cluster in progress or just completed. */ if (found_free_cluster) { /* * To optimize wear-levelling, discard the * old data of the cluster, taking care not to * discard any of its pages that have already * been allocated by racing tasks (offset has * already stepped over any at the beginning). */ if (offset < si->highest_alloc && si->lowest_alloc <= last_in_cluster) last_in_cluster = si->lowest_alloc - 1; si->flags |= SWP_DISCARDING; spin_unlock(&swap_lock); if (offset < last_in_cluster) discard_swap_cluster(si, offset, last_in_cluster - offset + 1); spin_lock(&swap_lock); si->lowest_alloc = 0; si->flags &= ~SWP_DISCARDING; smp_mb(); /* wake_up_bit advises this */ wake_up_bit(&si->flags, ilog2(SWP_DISCARDING)); } else if (si->flags & SWP_DISCARDING) { /* * Delay using pages allocated by racing tasks * until the whole discard has been issued. We * could defer that delay until swap_writepage, * but it's easier to keep this self-contained. */ spin_unlock(&swap_lock); wait_on_bit(&si->flags, ilog2(SWP_DISCARDING), wait_for_discard, TASK_UNINTERRUPTIBLE); spin_lock(&swap_lock); } else { /* * Note pages allocated by racing tasks while * scan for a free cluster is in progress, so * that its final discard can exclude them. */ if (offset < si->lowest_alloc) si->lowest_alloc = offset; if (offset > si->highest_alloc) si->highest_alloc = offset; } } return offset; scan: spin_unlock(&swap_lock); while (++offset <= si->highest_bit) { if (!si->swap_map[offset]) { spin_lock(&swap_lock); goto checks; } if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { spin_lock(&swap_lock); goto checks; } if (unlikely(--latency_ration < 0)) { cond_resched(); latency_ration = LATENCY_LIMIT; } } offset = si->lowest_bit; while (++offset < scan_base) { if (!si->swap_map[offset]) { spin_lock(&swap_lock); goto checks; } if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { spin_lock(&swap_lock); goto checks; } if (unlikely(--latency_ration < 0)) { cond_resched(); latency_ration = LATENCY_LIMIT; } } spin_lock(&swap_lock); no_page: si->flags -= SWP_SCANNING; return 0; } swp_entry_t get_swap_page(void) { struct swap_info_struct *si; pgoff_t offset; int type, next; int wrapped = 0; spin_lock(&swap_lock); if (nr_swap_pages <= 0) goto noswap; if (swap_for_hibernation) goto noswap; nr_swap_pages--; for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { si = swap_info[type]; next = si->next; if (next < 0 || (!wrapped && si->prio != swap_info[next]->prio)) { next = swap_list.head; wrapped++; } if (!si->highest_bit) continue; if (!(si->flags & SWP_WRITEOK)) continue; swap_list.next = next; /* This is called for allocating swap entry for cache */ offset = scan_swap_map(si, SWAP_HAS_CACHE); if (offset) { spin_unlock(&swap_lock); return swp_entry(type, offset); } next = swap_list.next; } nr_swap_pages++; noswap: spin_unlock(&swap_lock); return (swp_entry_t) {0}; } static struct swap_info_struct *swap_info_get(swp_entry_t entry) { struct swap_info_struct *p; unsigned long offset, type; if (!entry.val) goto out; type = swp_type(entry); if (type >= nr_swapfiles) goto bad_nofile; p = swap_info[type]; if (!(p->flags & SWP_USED)) goto bad_device; offset = swp_offset(entry); if (offset >= p->max) goto bad_offset; if (!p->swap_map[offset]) goto bad_free; spin_lock(&swap_lock); return p; bad_free: printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); goto out; bad_offset: printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); goto out; bad_device: printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); goto out; bad_nofile: printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); out: return NULL; } static unsigned char swap_entry_free(struct swap_info_struct *p, swp_entry_t entry, unsigned char usage) { unsigned long offset = swp_offset(entry); unsigned char count; unsigned char has_cache; count = p->swap_map[offset]; has_cache = count & SWAP_HAS_CACHE; count &= ~SWAP_HAS_CACHE; if (usage == SWAP_HAS_CACHE) { VM_BUG_ON(!has_cache); has_cache = 0; } else if (count == SWAP_MAP_SHMEM) { /* * Or we could insist on shmem.c using a special * swap_shmem_free() and free_shmem_swap_and_cache()... */ count = 0; } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { if (count == COUNT_CONTINUED) { if (swap_count_continued(p, offset, count)) count = SWAP_MAP_MAX | COUNT_CONTINUED; else count = SWAP_MAP_MAX; } else count--; } if (!count) mem_cgroup_uncharge_swap(entry); usage = count | has_cache; p->swap_map[offset] = usage; /* free if no reference */ if (!usage) { struct gendisk *disk = p->bdev->bd_disk; if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit) p->highest_bit = offset; if (swap_list.next >= 0 && p->prio > swap_info[swap_list.next]->prio) swap_list.next = p->type; nr_swap_pages++; p->inuse_pages--; if ((p->flags & SWP_BLKDEV) && disk->fops->swap_slot_free_notify) disk->fops->swap_slot_free_notify(p->bdev, offset); } return usage; } /* * Caller has made sure that the swapdevice corresponding to entry * is still around or has not been recycled. */ void swap_free(swp_entry_t entry) { struct swap_info_struct *p; p = swap_info_get(entry); if (p) { swap_entry_free(p, entry, 1); spin_unlock(&swap_lock); } } /* * Called after dropping swapcache to decrease refcnt to swap entries. */ void swapcache_free(swp_entry_t entry, struct page *page) { struct swap_info_struct *p; unsigned char count; p = swap_info_get(entry); if (p) { count = swap_entry_free(p, entry, SWAP_HAS_CACHE); if (page) mem_cgroup_uncharge_swapcache(page, entry, count != 0); spin_unlock(&swap_lock); } } /* * How many references to page are currently swapped out? * This does not give an exact answer when swap count is continued, * but does include the high COUNT_CONTINUED flag to allow for that. */ static inline int page_swapcount(struct page *page) { int count = 0; struct swap_info_struct *p; swp_entry_t entry; entry.val = page_private(page); p = swap_info_get(entry); if (p) { count = swap_count(p->swap_map[swp_offset(entry)]); spin_unlock(&swap_lock); } return count; } /* * We can write to an anon page without COW if there are no other references * to it. And as a side-effect, free up its swap: because the old content * on disk will never be read, and seeking back there to write new content * later would only waste time away from clustering. */ int reuse_swap_page(struct page *page) { int count; VM_BUG_ON(!PageLocked(page)); if (unlikely(PageKsm(page))) return 0; count = page_mapcount(page); if (count <= 1 && PageSwapCache(page)) { count += page_swapcount(page); if (count == 1 && !PageWriteback(page)) { delete_from_swap_cache(page); SetPageDirty(page); } } return count <= 1; } /* * If swap is getting full, or if there are no more mappings of this page, * then try_to_free_swap is called to free its swap space. */ int try_to_free_swap(struct page *page) { VM_BUG_ON(!PageLocked(page)); if (!PageSwapCache(page)) return 0; if (PageWriteback(page)) return 0; if (page_swapcount(page)) return 0; delete_from_swap_cache(page); SetPageDirty(page); return 1; } /* * Free the swap entry like above, but also try to * free the page cache entry if it is the last user. */ int free_swap_and_cache(swp_entry_t entry) { struct swap_info_struct *p; struct page *page = NULL; if (non_swap_entry(entry)) return 1; p = swap_info_get(entry); if (p) { if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) { page = find_get_page(&swapper_space, entry.val); if (page && !trylock_page(page)) { page_cache_release(page); page = NULL; } } spin_unlock(&swap_lock); } if (page) { /* * Not mapped elsewhere, or swap space full? Free it! * Also recheck PageSwapCache now page is locked (above). */ if (PageSwapCache(page) && !PageWriteback(page) && (!page_mapped(page) || vm_swap_full())) { delete_from_swap_cache(page); SetPageDirty(page); } unlock_page(page); page_cache_release(page); } return p != NULL; } #ifdef CONFIG_CGROUP_MEM_RES_CTLR /** * mem_cgroup_count_swap_user - count the user of a swap entry * @ent: the swap entry to be checked * @pagep: the pointer for the swap cache page of the entry to be stored * * Returns the number of the user of the swap entry. The number is valid only * for swaps of anonymous pages. * If the entry is found on swap cache, the page is stored to pagep with * refcount of it being incremented. */ int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep) { struct page *page; struct swap_info_struct *p; int count = 0; page = find_get_page(&swapper_space, ent.val); if (page) count += page_mapcount(page); p = swap_info_get(ent); if (p) { count += swap_count(p->swap_map[swp_offset(ent)]); spin_unlock(&swap_lock); } *pagep = page; return count; } #endif #ifdef CONFIG_HIBERNATION static pgoff_t hibernation_offset[MAX_SWAPFILES]; /* * Once hibernation starts to use swap, we freeze swap_map[]. Otherwise, * saved swap_map[] image to the disk will be an incomplete because it's * changing without synchronization with hibernation snap shot. * At resume, we just make swap_for_hibernation=false. We can forget * used maps easily. */ void hibernation_freeze_swap(void) { int i; spin_lock(&swap_lock); printk(KERN_INFO "PM: Freeze Swap\n"); swap_for_hibernation = true; for (i = 0; i < MAX_SWAPFILES; i++) hibernation_offset[i] = 1; spin_unlock(&swap_lock); } void hibernation_thaw_swap(void) { spin_lock(&swap_lock); if (swap_for_hibernation) { printk(KERN_INFO "PM: Thaw Swap\n"); swap_for_hibernation = false; } spin_unlock(&swap_lock); } /* * Because updateing swap_map[] can make not-saved-status-change, * we use our own easy allocator. * Please see kernel/power/swap.c, Used swaps are recorded into * RB-tree. */ swp_entry_t get_swap_for_hibernation(int type) { pgoff_t off; swp_entry_t val = {0}; struct swap_info_struct *si; spin_lock(&swap_lock); si = swap_info[type]; if (!si || !(si->flags & SWP_WRITEOK)) goto done; for (off = hibernation_offset[type]; off < si->max; ++off) { if (!si->swap_map[off]) break; } if (off < si->max) { val = swp_entry(type, off); hibernation_offset[type] = off + 1; } done: spin_unlock(&swap_lock); return val; } void swap_free_for_hibernation(swp_entry_t ent) { /* Nothing to do */ } /* * Find the swap type that corresponds to given device (if any). * * @offset - number of the PAGE_SIZE-sized block of the device, starting * from 0, in which the swap header is expected to be located. * * This is needed for the suspend to disk (aka swsusp). */ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p) { struct block_device *bdev = NULL; int type; if (device) bdev = bdget(device); spin_lock(&swap_lock); for (type = 0; type < nr_swapfiles; type++) { struct swap_info_struct *sis = swap_info[type]; if (!(sis->flags & SWP_WRITEOK)) continue; if (!bdev) { if (bdev_p) *bdev_p = bdgrab(sis->bdev); spin_unlock(&swap_lock); return type; } if (bdev == sis->bdev) { struct swap_extent *se = &sis->first_swap_extent; if (se->start_block == offset) { if (bdev_p) *bdev_p = bdgrab(sis->bdev); spin_unlock(&swap_lock); bdput(bdev); return type; } } } spin_unlock(&swap_lock); if (bdev) bdput(bdev); return -ENODEV; } /* * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev * corresponding to given index in swap_info (swap type). */ sector_t swapdev_block(int type, pgoff_t offset) { struct block_device *bdev; if ((unsigned int)type >= nr_swapfiles) return 0; if (!(swap_info[type]->flags & SWP_WRITEOK)) return 0; return map_swap_entry(swp_entry(type, offset), &bdev); } /* * Return either the total number of swap pages of given type, or the number * of free pages of that type (depending on @free) * * This is needed for software suspend */ unsigned int count_swap_pages(int type, int free) { unsigned int n = 0; spin_lock(&swap_lock); if ((unsigned int)type < nr_swapfiles) { struct swap_info_struct *sis = swap_info[type]; if (sis->flags & SWP_WRITEOK) { n = sis->pages; if (free) n -= sis->inuse_pages; } } spin_unlock(&swap_lock); return n; } #endif /* CONFIG_HIBERNATION */ /* * No need to decide whether this PTE shares the swap entry with others, * just let do_wp_page work it out if a write is requested later - to * force COW, vm_page_prot omits write permission from any private vma. */ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, swp_entry_t entry, struct page *page) { struct mem_cgroup *ptr = NULL; spinlock_t *ptl; pte_t *pte; int ret = 1; if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) { ret = -ENOMEM; goto out_nolock; } pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { if (ret > 0) mem_cgroup_cancel_charge_swapin(ptr); ret = 0; goto out; } dec_mm_counter(vma->vm_mm, MM_SWAPENTS); inc_mm_counter(vma->vm_mm, MM_ANONPAGES); get_page(page); set_pte_at(vma->vm_mm, addr, pte, pte_mkold(mk_pte(page, vma->vm_page_prot))); page_add_anon_rmap(page, vma, addr); mem_cgroup_commit_charge_swapin(page, ptr); swap_free(entry); /* * Move the page to the active list so it is not * immediately swapped out again after swapon. */ activate_page(page); out: pte_unmap_unlock(pte, ptl); out_nolock: return ret; } static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long end, swp_entry_t entry, struct page *page) { pte_t swp_pte = swp_entry_to_pte(entry); pte_t *pte; int ret = 0; /* * We don't actually need pte lock while scanning for swp_pte: since * we hold page lock and mmap_sem, swp_pte cannot be inserted into the * page table while we're scanning; though it could get zapped, and on * some architectures (e.g. x86_32 with PAE) we might catch a glimpse * of unmatched parts which look like swp_pte, so unuse_pte must * recheck under pte lock. Scanning without pte lock lets it be * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE. */ pte = pte_offset_map(pmd, addr); do { /* * swapoff spends a _lot_ of time in this loop! * Test inline before going to call unuse_pte. */ if (unlikely(pte_same(*pte, swp_pte))) { pte_unmap(pte); ret = unuse_pte(vma, pmd, addr, entry, page); if (ret) goto out; pte = pte_offset_map(pmd, addr); } } while (pte++, addr += PAGE_SIZE, addr != end); pte_unmap(pte - 1); out: return ret; } static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, unsigned long addr, unsigned long end, swp_entry_t entry, struct page *page) { pmd_t *pmd; unsigned long next; int ret; pmd = pmd_offset(pud, addr); do { next = pmd_addr_end(addr, end); if (pmd_none_or_clear_bad(pmd)) continue; ret = unuse_pte_range(vma, pmd, addr, next, entry, page); if (ret) return ret; } while (pmd++, addr = next, addr != end); return 0; } static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr, unsigned long end, swp_entry_t entry, struct page *page) { pud_t *pud; unsigned long next; int ret; pud = pud_offset(pgd, addr); do { next = pud_addr_end(addr, end); if (pud_none_or_clear_bad(pud)) continue; ret = unuse_pmd_range(vma, pud, addr, next, entry, page); if (ret) return ret; } while (pud++, addr = next, addr != end); return 0; } static int unuse_vma(struct vm_area_struct *vma, swp_entry_t entry, struct page *page) { pgd_t *pgd; unsigned long addr, end, next; int ret; if (page_anon_vma(page)) { addr = page_address_in_vma(page, vma); if (addr == -EFAULT) return 0; else end = addr + PAGE_SIZE; } else { addr = vma->vm_start; end = vma->vm_end; } pgd = pgd_offset(vma->vm_mm, addr); do { next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) continue; ret = unuse_pud_range(vma, pgd, addr, next, entry, page); if (ret) return ret; } while (pgd++, addr = next, addr != end); return 0; } static int unuse_mm(struct mm_struct *mm, swp_entry_t entry, struct page *page) { struct vm_area_struct *vma; int ret = 0; if (!down_read_trylock(&mm->mmap_sem)) { /* * Activate page so shrink_inactive_list is unlikely to unmap * its ptes while lock is dropped, so swapoff can make progress. */ activate_page(page); unlock_page(page); down_read(&mm->mmap_sem); lock_page(page); } for (vma = mm->mmap; vma; vma = vma->vm_next) { if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) break; } up_read(&mm->mmap_sem); return (ret < 0)? ret: 0; } /* * Scan swap_map from current position to next entry still in use. * Recycle to start on reaching the end, returning 0 when empty. */ static unsigned int find_next_to_unuse(struct swap_info_struct *si, unsigned int prev) { unsigned int max = si->max; unsigned int i = prev; unsigned char count; /* * No need for swap_lock here: we're just looking * for whether an entry is in use, not modifying it; false * hits are okay, and sys_swapoff() has already prevented new * allocations from this area (while holding swap_lock). */ for (;;) { if (++i >= max) { if (!prev) { i = 0; break; } /* * No entries in use at top of swap_map, * loop back to start and recheck there. */ max = prev + 1; prev = 0; i = 1; } count = si->swap_map[i]; if (count && swap_count(count) != SWAP_MAP_BAD) break; } return i; } /* * We completely avoid races by reading each swap page in advance, * and then search for the process using it. All the necessary * page table adjustments can then be made atomically. */ static int try_to_unuse(unsigned int type) { struct swap_info_struct *si = swap_info[type]; struct mm_struct *start_mm; unsigned char *swap_map; unsigned char swcount; struct page *page; swp_entry_t entry; unsigned int i = 0; int retval = 0; /* * When searching mms for an entry, a good strategy is to * start at the first mm we freed the previous entry from * (though actually we don't notice whether we or coincidence * freed the entry). Initialize this start_mm with a hold. * * A simpler strategy would be to start at the last mm we * freed the previous entry from; but that would take less * advantage of mmlist ordering, which clusters forked mms * together, child after parent. If we race with dup_mmap(), we * prefer to resolve parent before child, lest we miss entries * duplicated after we scanned child: using last mm would invert * that. */ start_mm = &init_mm; atomic_inc(&init_mm.mm_users); /* * Keep on scanning until all entries have gone. Usually, * one pass through swap_map is enough, but not necessarily: * there are races when an instance of an entry might be missed. */ while ((i = find_next_to_unuse(si, i)) != 0) { if (signal_pending(current)) { retval = -EINTR; break; } /* * Get a page for the entry, using the existing swap * cache page if there is one. Otherwise, get a clean * page and read the swap into it. */ swap_map = &si->swap_map[i]; entry = swp_entry(type, i); page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE, NULL, 0); if (!page) { /* * Either swap_duplicate() failed because entry * has been freed independently, and will not be * reused since sys_swapoff() already disabled * allocation from here, or alloc_page() failed. */ if (!*swap_map) continue; retval = -ENOMEM; break; } /* * Don't hold on to start_mm if it looks like exiting. */ if (atomic_read(&start_mm->mm_users) == 1) { mmput(start_mm); start_mm = &init_mm; atomic_inc(&init_mm.mm_users); } /* * Wait for and lock page. When do_swap_page races with * try_to_unuse, do_swap_page can handle the fault much * faster than try_to_unuse can locate the entry. This * apparently redundant "wait_on_page_locked" lets try_to_unuse * defer to do_swap_page in such a case - in some tests, * do_swap_page and try_to_unuse repeatedly compete. */ wait_on_page_locked(page); wait_on_page_writeback(page); lock_page(page); wait_on_page_writeback(page); /* * Remove all references to entry. */ swcount = *swap_map; if (swap_count(swcount) == SWAP_MAP_SHMEM) { retval = shmem_unuse(entry, page); /* page has already been unlocked and released */ if (retval < 0) break; continue; } if (swap_count(swcount) && start_mm != &init_mm) retval = unuse_mm(start_mm, entry, page); if (swap_count(*swap_map)) { int set_start_mm = (*swap_map >= swcount); struct list_head *p = &start_mm->mmlist; struct mm_struct *new_start_mm = start_mm; struct mm_struct *prev_mm = start_mm; struct mm_struct *mm; atomic_inc(&new_start_mm->mm_users); atomic_inc(&prev_mm->mm_users); spin_lock(&mmlist_lock); while (swap_count(*swap_map) && !retval && (p = p->next) != &start_mm->mmlist) { mm = list_entry(p, struct mm_struct, mmlist); if (!atomic_inc_not_zero(&mm->mm_users)) continue; spin_unlock(&mmlist_lock); mmput(prev_mm); prev_mm = mm; cond_resched(); swcount = *swap_map; if (!swap_count(swcount)) /* any usage ? */ ; else if (mm == &init_mm) set_start_mm = 1; else retval = unuse_mm(mm, entry, page); if (set_start_mm && *swap_map < swcount) { mmput(new_start_mm); atomic_inc(&mm->mm_users); new_start_mm = mm; set_start_mm = 0; } spin_lock(&mmlist_lock); } spin_unlock(&mmlist_lock); mmput(prev_mm); mmput(start_mm); start_mm = new_start_mm; } if (retval) { unlock_page(page); page_cache_release(page); break; } /* * If a reference remains (rare), we would like to leave * the page in the swap cache; but try_to_unmap could * then re-duplicate the entry once we drop page lock, * so we might loop indefinitely; also, that page could * not be swapped out to other storage meanwhile. So: * delete from cache even if there's another reference, * after ensuring that the data has been saved to disk - * since if the reference remains (rarer), it will be * read from disk into another page. Splitting into two * pages would be incorrect if swap supported "shared * private" pages, but they are handled by tmpfs files. * * Given how unuse_vma() targets one particular offset * in an anon_vma, once the anon_vma has been determined, * this splitting happens to be just what is needed to * handle where KSM pages have been swapped out: re-reading * is unnecessarily slow, but we can fix that later on. */ if (swap_count(*swap_map) && PageDirty(page) && PageSwapCache(page)) { struct writeback_control wbc = { .sync_mode = WB_SYNC_NONE, }; swap_writepage(page, &wbc); lock_page(page); wait_on_page_writeback(page); } /* * It is conceivable that a racing task removed this page from * swap cache just before we acquired the page lock at the top, * or while we dropped it in unuse_mm(). The page might even * be back in swap cache on another swap area: that we must not * delete, since it may not have been written out to swap yet. */ if (PageSwapCache(page) && likely(page_private(page) == entry.val)) delete_from_swap_cache(page); /* * So we could skip searching mms once swap count went * to 1, we did not mark any present ptes as dirty: must * mark page dirty so shrink_page_list will preserve it. */ SetPageDirty(page); unlock_page(page); page_cache_release(page); /* * Make sure that we aren't completely killing * interactive performance. */ cond_resched(); } mmput(start_mm); return retval; } /* * After a successful try_to_unuse, if no swap is now in use, we know * we can empty the mmlist. swap_lock must be held on entry and exit. * Note that mmlist_lock nests inside swap_lock, and an mm must be * added to the mmlist just after page_duplicate - before would be racy. */ static void drain_mmlist(void) { struct list_head *p, *next; unsigned int type; for (type = 0; type < nr_swapfiles; type++) if (swap_info[type]->inuse_pages) return; spin_lock(&mmlist_lock); list_for_each_safe(p, next, &init_mm.mmlist) list_del_init(p); spin_unlock(&mmlist_lock); } /* * Use this swapdev's extent info to locate the (PAGE_SIZE) block which * corresponds to page offset for the specified swap entry. * Note that the type of this function is sector_t, but it returns page offset * into the bdev, not sector offset. */ static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev) { struct swap_info_struct *sis; struct swap_extent *start_se; struct swap_extent *se; pgoff_t offset; sis = swap_info[swp_type(entry)]; *bdev = sis->bdev; offset = swp_offset(entry); start_se = sis->curr_swap_extent; se = start_se; for ( ; ; ) { struct list_head *lh; if (se->start_page <= offset && offset < (se->start_page + se->nr_pages)) { return se->start_block + (offset - se->start_page); } lh = se->list.next; se = list_entry(lh, struct swap_extent, list); sis->curr_swap_extent = se; BUG_ON(se == start_se); /* It *must* be present */ } } /* * Returns the page offset into bdev for the specified page's swap entry. */ sector_t map_swap_page(struct page *page, struct block_device **bdev) { swp_entry_t entry; entry.val = page_private(page); return map_swap_entry(entry, bdev); } /* * Free all of a swapdev's extent information */ static void destroy_swap_extents(struct swap_info_struct *sis) { while (!list_empty(&sis->first_swap_extent.list)) { struct swap_extent *se; se = list_entry(sis->first_swap_extent.list.next, struct swap_extent, list); list_del(&se->list); kfree(se); } } /* * Add a block range (and the corresponding page range) into this swapdev's * extent list. The extent list is kept sorted in page order. * * This function rather assumes that it is called in ascending page order. */ static int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, unsigned long nr_pages, sector_t start_block) { struct swap_extent *se; struct swap_extent *new_se; struct list_head *lh; if (start_page == 0) { se = &sis->first_swap_extent; sis->curr_swap_extent = se; se->start_page = 0; se->nr_pages = nr_pages; se->start_block = start_block; return 1; } else { lh = sis->first_swap_extent.list.prev; /* Highest extent */ se = list_entry(lh, struct swap_extent, list); BUG_ON(se->start_page + se->nr_pages != start_page); if (se->start_block + se->nr_pages == start_block) { /* Merge it */ se->nr_pages += nr_pages; return 0; } } /* * No merge. Insert a new extent, preserving ordering. */ new_se = kmalloc(sizeof(*se), GFP_KERNEL); if (new_se == NULL) return -ENOMEM; new_se->start_page = start_page; new_se->nr_pages = nr_pages; new_se->start_block = start_block; list_add_tail(&new_se->list, &sis->first_swap_extent.list); return 1; } /* * A `swap extent' is a simple thing which maps a contiguous range of pages * onto a contiguous range of disk blocks. An ordered list of swap extents * is built at swapon time and is then used at swap_writepage/swap_readpage * time for locating where on disk a page belongs. * * If the swapfile is an S_ISBLK block device, a single extent is installed. * This is done so that the main operating code can treat S_ISBLK and S_ISREG * swap files identically. * * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK * swapfiles are handled *identically* after swapon time. * * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If * some stray blocks are found which do not fall within the PAGE_SIZE alignment * requirements, they are simply tossed out - we will never use those blocks * for swapping. * * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This * prevents root from shooting her foot off by ftruncating an in-use swapfile, * which will scribble on the fs. * * The amount of disk space which a single swap extent represents varies. * Typically it is in the 1-4 megabyte range. So we can have hundreds of * extents in the list. To avoid much list walking, we cache the previous * search location in `curr_swap_extent', and start new searches from there. * This is extremely effective. The average number of iterations in * map_swap_page() has been measured at about 0.3 per page. - akpm. */ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) { struct inode *inode; unsigned blocks_per_page; unsigned long page_no; unsigned blkbits; sector_t probe_block; sector_t last_block; sector_t lowest_block = -1; sector_t highest_block = 0; int nr_extents = 0; int ret; inode = sis->swap_file->f_mapping->host; if (S_ISBLK(inode->i_mode)) { ret = add_swap_extent(sis, 0, sis->max, 0); *span = sis->pages; goto out; } blkbits = inode->i_blkbits; blocks_per_page = PAGE_SIZE >> blkbits; /* * Map all the blocks into the extent list. This code doesn't try * to be very smart. */ probe_block = 0; page_no = 0; last_block = i_size_read(inode) >> blkbits; while ((probe_block + blocks_per_page) <= last_block && page_no < sis->max) { unsigned block_in_page; sector_t first_block; first_block = bmap(inode, probe_block); if (first_block == 0) goto bad_bmap; /* * It must be PAGE_SIZE aligned on-disk */ if (first_block & (blocks_per_page - 1)) { probe_block++; goto reprobe; } for (block_in_page = 1; block_in_page < blocks_per_page; block_in_page++) { sector_t block; block = bmap(inode, probe_block + block_in_page); if (block == 0) goto bad_bmap; if (block != first_block + block_in_page) { /* Discontiguity */ probe_block++; goto reprobe; } } first_block >>= (PAGE_SHIFT - blkbits); if (page_no) { /* exclude the header page */ if (first_block < lowest_block) lowest_block = first_block; if (first_block > highest_block) highest_block = first_block; } /* * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks */ ret = add_swap_extent(sis, page_no, 1, first_block); if (ret < 0) goto out; nr_extents += ret; page_no++; probe_block += blocks_per_page; reprobe: continue; } ret = nr_extents; *span = 1 + highest_block - lowest_block; if (page_no == 0) page_no = 1; /* force Empty message */ sis->max = page_no; sis->pages = page_no - 1; sis->highest_bit = page_no - 1; out: return ret; bad_bmap: printk(KERN_ERR "swapon: swapfile has holes\n"); ret = -EINVAL; goto out; } SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) { struct swap_info_struct *p = NULL; unsigned char *swap_map; struct file *swap_file, *victim; struct address_space *mapping; struct inode *inode; char *pathname; int i, type, prev; int err; if (!capable(CAP_SYS_ADMIN)) return -EPERM; pathname = getname(specialfile); err = PTR_ERR(pathname); if (IS_ERR(pathname)) goto out; victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0); putname(pathname); err = PTR_ERR(victim); if (IS_ERR(victim)) goto out; mapping = victim->f_mapping; prev = -1; spin_lock(&swap_lock); for (type = swap_list.head; type >= 0; type = swap_info[type]->next) { p = swap_info[type]; if (p->flags & SWP_WRITEOK) { if (p->swap_file->f_mapping == mapping) break; } prev = type; } if (type < 0) { err = -EINVAL; spin_unlock(&swap_lock); goto out_dput; } if (!security_vm_enough_memory(p->pages)) vm_unacct_memory(p->pages); else { err = -ENOMEM; spin_unlock(&swap_lock); goto out_dput; } if (prev < 0) swap_list.head = p->next; else swap_info[prev]->next = p->next; if (type == swap_list.next) { /* just pick something that's safe... */ swap_list.next = swap_list.head; } if (p->prio < 0) { for (i = p->next; i >= 0; i = swap_info[i]->next) swap_info[i]->prio = p->prio--; least_priority++; } nr_swap_pages -= p->pages; total_swap_pages -= p->pages; p->flags &= ~SWP_WRITEOK; spin_unlock(&swap_lock); current->flags |= PF_OOM_ORIGIN; err = try_to_unuse(type); current->flags &= ~PF_OOM_ORIGIN; if (err) { /* re-insert swap space back into swap_list */ spin_lock(&swap_lock); if (p->prio < 0) p->prio = --least_priority; prev = -1; for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { if (p->prio >= swap_info[i]->prio) break; prev = i; } p->next = i; if (prev < 0) swap_list.head = swap_list.next = type; else swap_info[prev]->next = type; nr_swap_pages += p->pages; total_swap_pages += p->pages; p->flags |= SWP_WRITEOK; spin_unlock(&swap_lock); goto out_dput; } /* wait for any unplug function to finish */ down_write(&swap_unplug_sem); up_write(&swap_unplug_sem); destroy_swap_extents(p); if (p->flags & SWP_CONTINUED) free_swap_count_continuations(p); mutex_lock(&swapon_mutex); spin_lock(&swap_lock); drain_mmlist(); /* wait for anyone still in scan_swap_map */ p->highest_bit = 0; /* cuts scans short */ while (p->flags >= SWP_SCANNING) { spin_unlock(&swap_lock); schedule_timeout_uninterruptible(1); spin_lock(&swap_lock); } swap_file = p->swap_file; p->swap_file = NULL; p->max = 0; swap_map = p->swap_map; p->swap_map = NULL; p->flags = 0; spin_unlock(&swap_lock); mutex_unlock(&swapon_mutex); vfree(swap_map); /* Destroy swap account informatin */ swap_cgroup_swapoff(type); inode = mapping->host; if (S_ISBLK(inode->i_mode)) { struct block_device *bdev = I_BDEV(inode); set_blocksize(bdev, p->old_block_size); bd_release(bdev); } else { mutex_lock(&inode->i_mutex); inode->i_flags &= ~S_SWAPFILE; mutex_unlock(&inode->i_mutex); } filp_close(swap_file, NULL); err = 0; out_dput: filp_close(victim, NULL); out: return err; } #ifdef CONFIG_PROC_FS /* iterator */ static void *swap_start(struct seq_file *swap, loff_t *pos) { struct swap_info_struct *si; int type; loff_t l = *pos; mutex_lock(&swapon_mutex); if (!l) return SEQ_START_TOKEN; for (type = 0; type < nr_swapfiles; type++) { smp_rmb(); /* read nr_swapfiles before swap_info[type] */ si = swap_info[type]; if (!(si->flags & SWP_USED) || !si->swap_map) continue; if (!--l) return si; } return NULL; } static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) { struct swap_info_struct *si = v; int type; if (v == SEQ_START_TOKEN) type = 0; else type = si->type + 1; for (; type < nr_swapfiles; type++) { smp_rmb(); /* read nr_swapfiles before swap_info[type] */ si = swap_info[type]; if (!(si->flags & SWP_USED) || !si->swap_map) continue; ++*pos; return si; } return NULL; } static void swap_stop(struct seq_file *swap, void *v) { mutex_unlock(&swapon_mutex); } static int swap_show(struct seq_file *swap, void *v) { struct swap_info_struct *si = v; struct file *file; int len; if (si == SEQ_START_TOKEN) { seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); return 0; } file = si->swap_file; len = seq_path(swap, &file->f_path, " \t\n\\"); seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", len < 40 ? 40 - len : 1, " ", S_ISBLK(file->f_path.dentry->d_inode->i_mode) ? "partition" : "file\t", si->pages << (PAGE_SHIFT - 10), si->inuse_pages << (PAGE_SHIFT - 10), si->prio); return 0; } static const struct seq_operations swaps_op = { .start = swap_start, .next = swap_next, .stop = swap_stop, .show = swap_show }; static int swaps_open(struct inode *inode, struct file *file) { return seq_open(file, &swaps_op); } static const struct file_operations proc_swaps_operations = { .open = swaps_open, .read = seq_read, .llseek = seq_lseek, .release = seq_release, }; static int __init procswaps_init(void) { proc_create("swaps", 0, NULL, &proc_swaps_operations); return 0; } __initcall(procswaps_init); #endif /* CONFIG_PROC_FS */ #ifdef MAX_SWAPFILES_CHECK static int __init max_swapfiles_check(void) { MAX_SWAPFILES_CHECK(); return 0; } late_initcall(max_swapfiles_check); #endif /* * Written 01/25/92 by Simmule Turner, heavily changed by Linus. * * The swapon system call */ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) { struct swap_info_struct *p; char *name = NULL; struct block_device *bdev = NULL; struct file *swap_file = NULL; struct address_space *mapping; unsigned int type; int i, prev; int error; union swap_header *swap_header; unsigned int nr_good_pages; int nr_extents = 0; sector_t span; unsigned long maxpages; unsigned long swapfilepages; unsigned char *swap_map = NULL; struct page *page = NULL; struct inode *inode = NULL; int did_down = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; p = kzalloc(sizeof(*p), GFP_KERNEL); if (!p) return -ENOMEM; spin_lock(&swap_lock); for (type = 0; type < nr_swapfiles; type++) { if (!(swap_info[type]->flags & SWP_USED)) break; } error = -EPERM; if (type >= MAX_SWAPFILES) { spin_unlock(&swap_lock); kfree(p); goto out; } if (type >= nr_swapfiles) { p->type = type; swap_info[type] = p; /* * Write swap_info[type] before nr_swapfiles, in case a * racing procfs swap_start() or swap_next() is reading them. * (We never shrink nr_swapfiles, we never free this entry.) */ smp_wmb(); nr_swapfiles++; } else { kfree(p); p = swap_info[type]; /* * Do not memset this entry: a racing procfs swap_next() * would be relying on p->type to remain valid. */ } INIT_LIST_HEAD(&p->first_swap_extent.list); p->flags = SWP_USED; p->next = -1; spin_unlock(&swap_lock); name = getname(specialfile); error = PTR_ERR(name); if (IS_ERR(name)) { name = NULL; goto bad_swap_2; } swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); error = PTR_ERR(swap_file); if (IS_ERR(swap_file)) { swap_file = NULL; goto bad_swap_2; } p->swap_file = swap_file; mapping = swap_file->f_mapping; inode = mapping->host; error = -EBUSY; for (i = 0; i < nr_swapfiles; i++) { struct swap_info_struct *q = swap_info[i]; if (i == type || !q->swap_file) continue; if (mapping == q->swap_file->f_mapping) goto bad_swap; } error = -EINVAL; if (S_ISBLK(inode->i_mode)) { bdev = I_BDEV(inode); error = bd_claim(bdev, sys_swapon); if (error < 0) { bdev = NULL; error = -EINVAL; goto bad_swap; } p->old_block_size = block_size(bdev); error = set_blocksize(bdev, PAGE_SIZE); if (error < 0) goto bad_swap; p->bdev = bdev; p->flags |= SWP_BLKDEV; } else if (S_ISREG(inode->i_mode)) { p->bdev = inode->i_sb->s_bdev; mutex_lock(&inode->i_mutex); did_down = 1; if (IS_SWAPFILE(inode)) { error = -EBUSY; goto bad_swap; } } else { goto bad_swap; } swapfilepages = i_size_read(inode) >> PAGE_SHIFT; /* * Read the swap header. */ if (!mapping->a_ops->readpage) { error = -EINVAL; goto bad_swap; } page = read_mapping_page(mapping, 0, swap_file); if (IS_ERR(page)) { error = PTR_ERR(page); goto bad_swap; } swap_header = kmap(page); if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { printk(KERN_ERR "Unable to find swap-space signature\n"); error = -EINVAL; goto bad_swap; } /* swap partition endianess hack... */ if (swab32(swap_header->info.version) == 1) { swab32s(&swap_header->info.version); swab32s(&swap_header->info.last_page); swab32s(&swap_header->info.nr_badpages); for (i = 0; i < swap_header->info.nr_badpages; i++) swab32s(&swap_header->info.badpages[i]); } /* Check the swap header's sub-version */ if (swap_header->info.version != 1) { printk(KERN_WARNING "Unable to handle swap header version %d\n", swap_header->info.version); error = -EINVAL; goto bad_swap; } p->lowest_bit = 1; p->cluster_next = 1; p->cluster_nr = 0; /* * Find out how many pages are allowed for a single swap * device. There are two limiting factors: 1) the number of * bits for the swap offset in the swp_entry_t type and * 2) the number of bits in the a swap pte as defined by * the different architectures. In order to find the * largest possible bit mask a swap entry with swap type 0 * and swap offset ~0UL is created, encoded to a swap pte, * decoded to a swp_entry_t again and finally the swap * offset is extracted. This will mask all the bits from * the initial ~0UL mask that can't be encoded in either * the swp_entry_t or the architecture definition of a * swap pte. */ maxpages = swp_offset(pte_to_swp_entry( swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; if (maxpages > swap_header->info.last_page) { maxpages = swap_header->info.last_page + 1; /* p->max is an unsigned int: don't overflow it */ if ((unsigned int)maxpages == 0) maxpages = UINT_MAX; } p->highest_bit = maxpages - 1; error = -EINVAL; if (!maxpages) goto bad_swap; if (swapfilepages && maxpages > swapfilepages) { printk(KERN_WARNING "Swap area shorter than signature indicates\n"); goto bad_swap; } if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) goto bad_swap; if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) goto bad_swap; /* OK, set up the swap map and apply the bad block list */ swap_map = vmalloc(maxpages); if (!swap_map) { error = -ENOMEM; goto bad_swap; } memset(swap_map, 0, maxpages); nr_good_pages = maxpages - 1; /* omit header page */ for (i = 0; i < swap_header->info.nr_badpages; i++) { unsigned int page_nr = swap_header->info.badpages[i]; if (page_nr == 0 || page_nr > swap_header->info.last_page) { error = -EINVAL; goto bad_swap; } if (page_nr < maxpages) { swap_map[page_nr] = SWAP_MAP_BAD; nr_good_pages--; } } error = swap_cgroup_swapon(type, maxpages); if (error) goto bad_swap; if (nr_good_pages) { swap_map[0] = SWAP_MAP_BAD; p->max = maxpages; p->pages = nr_good_pages; nr_extents = setup_swap_extents(p, &span); if (nr_extents < 0) { error = nr_extents; goto bad_swap; } nr_good_pages = p->pages; } if (!nr_good_pages) { printk(KERN_WARNING "Empty swap-file\n"); error = -EINVAL; goto bad_swap; } if (p->bdev) { if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { p->flags |= SWP_SOLIDSTATE; p->cluster_next = 1 + (random32() % p->highest_bit); } if (discard_swap(p) == 0) p->flags |= SWP_DISCARDABLE; } mutex_lock(&swapon_mutex); spin_lock(&swap_lock); if (swap_flags & SWAP_FLAG_PREFER) p->prio = (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; else p->prio = --least_priority; p->swap_map = swap_map; p->flags |= SWP_WRITEOK; nr_swap_pages += nr_good_pages; total_swap_pages += nr_good_pages; printk(KERN_INFO "Adding %uk swap on %s. " "Priority:%d extents:%d across:%lluk %s%s\n", nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), (p->flags & SWP_SOLIDSTATE) ? "SS" : "", (p->flags & SWP_DISCARDABLE) ? "D" : ""); /* insert swap space into swap_list: */ prev = -1; for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { if (p->prio >= swap_info[i]->prio) break; prev = i; } p->next = i; if (prev < 0) swap_list.head = swap_list.next = type; else swap_info[prev]->next = type; spin_unlock(&swap_lock); mutex_unlock(&swapon_mutex); error = 0; goto out; bad_swap: if (bdev) { set_blocksize(bdev, p->old_block_size); bd_release(bdev); } destroy_swap_extents(p); swap_cgroup_swapoff(type); bad_swap_2: spin_lock(&swap_lock); p->swap_file = NULL; p->flags = 0; spin_unlock(&swap_lock); vfree(swap_map); if (swap_file) filp_close(swap_file, NULL); out: if (page && !IS_ERR(page)) { kunmap(page); page_cache_release(page); } if (name) putname(name); if (did_down) { if (!error) inode->i_flags |= S_SWAPFILE; mutex_unlock(&inode->i_mutex); } return error; } void si_swapinfo(struct sysinfo *val) { unsigned int type; unsigned long nr_to_be_unused = 0; spin_lock(&swap_lock); for (type = 0; type < nr_swapfiles; type++) { struct swap_info_struct *si = swap_info[type]; if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) nr_to_be_unused += si->inuse_pages; } val->freeswap = nr_swap_pages + nr_to_be_unused; val->totalswap = total_swap_pages + nr_to_be_unused; spin_unlock(&swap_lock); } /* * Verify that a swap entry is valid and increment its swap map count. * * Returns error code in following case. * - success -> 0 * - swp_entry is invalid -> EINVAL * - swp_entry is migration entry -> EINVAL * - swap-cache reference is requested but there is already one. -> EEXIST * - swap-cache reference is requested but the entry is not used. -> ENOENT * - swap-mapped reference requested but needs continued swap count. -> ENOMEM */ static int __swap_duplicate(swp_entry_t entry, unsigned char usage) { struct swap_info_struct *p; unsigned long offset, type; unsigned char count; unsigned char has_cache; int err = -EINVAL; if (non_swap_entry(entry)) goto out; type = swp_type(entry); if (type >= nr_swapfiles) goto bad_file; p = swap_info[type]; offset = swp_offset(entry); spin_lock(&swap_lock); if (unlikely(offset >= p->max)) goto unlock_out; count = p->swap_map[offset]; has_cache = count & SWAP_HAS_CACHE; count &= ~SWAP_HAS_CACHE; err = 0; if (usage == SWAP_HAS_CACHE) { /* set SWAP_HAS_CACHE if there is no cache and entry is used */ if (!has_cache && count) has_cache = SWAP_HAS_CACHE; else if (has_cache) /* someone else added cache */ err = -EEXIST; else /* no users remaining */ err = -ENOENT; } else if (count || has_cache) { if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) count += usage; else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) err = -EINVAL; else if (swap_count_continued(p, offset, count)) count = COUNT_CONTINUED; else err = -ENOMEM; } else err = -ENOENT; /* unused swap entry */ p->swap_map[offset] = count | has_cache; unlock_out: spin_unlock(&swap_lock); out: return err; bad_file: printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); goto out; } /* * Help swapoff by noting that swap entry belongs to shmem/tmpfs * (in which case its reference count is never incremented). */ void swap_shmem_alloc(swp_entry_t entry) { __swap_duplicate(entry, SWAP_MAP_SHMEM); } /* * Increase reference count of swap entry by 1. * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required * but could not be atomically allocated. Returns 0, just as if it succeeded, * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which * might occur if a page table entry has got corrupted. */ int swap_duplicate(swp_entry_t entry) { int err = 0; while (!err && __swap_duplicate(entry, 1) == -ENOMEM) err = add_swap_count_continuation(entry, GFP_ATOMIC); return err; } /* * @entry: swap entry for which we allocate swap cache. * * Called when allocating swap cache for existing swap entry, * This can return error codes. Returns 0 at success. * -EBUSY means there is a swap cache. * Note: return code is different from swap_duplicate(). */ int swapcache_prepare(swp_entry_t entry) { return __swap_duplicate(entry, SWAP_HAS_CACHE); } /* * swap_lock prevents swap_map being freed. Don't grab an extra * reference on the swaphandle, it doesn't matter if it becomes unused. */ int valid_swaphandles(swp_entry_t entry, unsigned long *offset) { struct swap_info_struct *si; int our_page_cluster = page_cluster; pgoff_t target, toff; pgoff_t base, end; int nr_pages = 0; if (!our_page_cluster) /* no readahead */ return 0; si = swap_info[swp_type(entry)]; target = swp_offset(entry); base = (target >> our_page_cluster) << our_page_cluster; end = base + (1 << our_page_cluster); if (!base) /* first page is swap header */ base++; spin_lock(&swap_lock); if (end > si->max) /* don't go beyond end of map */ end = si->max; /* Count contiguous allocated slots above our target */ for (toff = target; ++toff < end; nr_pages++) { /* Don't read in free or bad pages */ if (!si->swap_map[toff]) break; if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) break; } /* Count contiguous allocated slots below our target */ for (toff = target; --toff >= base; nr_pages++) { /* Don't read in free or bad pages */ if (!si->swap_map[toff]) break; if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) break; } spin_unlock(&swap_lock); /* * Indicate starting offset, and return number of pages to get: * if only 1, say 0, since there's then no readahead to be done. */ *offset = ++toff; return nr_pages? ++nr_pages: 0; } /* * add_swap_count_continuation - called when a swap count is duplicated * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's * page of the original vmalloc'ed swap_map, to hold the continuation count * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc. * * These continuation pages are seldom referenced: the common paths all work * on the original swap_map, only referring to a continuation page when the * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. * * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL) * can be called after dropping locks. */ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) { struct swap_info_struct *si; struct page *head; struct page *page; struct page *list_page; pgoff_t offset; unsigned char count; /* * When debugging, it's easier to use __GFP_ZERO here; but it's better * for latency not to zero a page while GFP_ATOMIC and holding locks. */ page = alloc_page(gfp_mask | __GFP_HIGHMEM); si = swap_info_get(entry); if (!si) { /* * An acceptable race has occurred since the failing * __swap_duplicate(): the swap entry has been freed, * perhaps even the whole swap_map cleared for swapoff. */ goto outer; } offset = swp_offset(entry); count = si->swap_map[offset] & ~SWAP_HAS_CACHE; if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) { /* * The higher the swap count, the more likely it is that tasks * will race to add swap count continuation: we need to avoid * over-provisioning. */ goto out; } if (!page) { spin_unlock(&swap_lock); return -ENOMEM; } /* * We are fortunate that although vmalloc_to_page uses pte_offset_map, * no architecture is using highmem pages for kernel pagetables: so it * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps. */ head = vmalloc_to_page(si->swap_map + offset); offset &= ~PAGE_MASK; /* * Page allocation does not initialize the page's lru field, * but it does always reset its private field. */ if (!page_private(head)) { BUG_ON(count & COUNT_CONTINUED); INIT_LIST_HEAD(&head->lru); set_page_private(head, SWP_CONTINUED); si->flags |= SWP_CONTINUED; } list_for_each_entry(list_page, &head->lru, lru) { unsigned char *map; /* * If the previous map said no continuation, but we've found * a continuation page, free our allocation and use this one. */ if (!(count & COUNT_CONTINUED)) goto out; map = kmap_atomic(list_page, KM_USER0) + offset; count = *map; kunmap_atomic(map, KM_USER0); /* * If this continuation count now has some space in it, * free our allocation and use this one. */ if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX) goto out; } list_add_tail(&page->lru, &head->lru); page = NULL; /* now it's attached, don't free it */ out: spin_unlock(&swap_lock); outer: if (page) __free_page(page); return 0; } /* * swap_count_continued - when the original swap_map count is incremented * from SWAP_MAP_MAX, check if there is already a continuation page to carry * into, carry if so, or else fail until a new continuation page is allocated; * when the original swap_map count is decremented from 0 with continuation, * borrow from the continuation and report whether it still holds more. * Called while __swap_duplicate() or swap_entry_free() holds swap_lock. */ static bool swap_count_continued(struct swap_info_struct *si, pgoff_t offset, unsigned char count) { struct page *head; struct page *page; unsigned char *map; head = vmalloc_to_page(si->swap_map + offset); if (page_private(head) != SWP_CONTINUED) { BUG_ON(count & COUNT_CONTINUED); return false; /* need to add count continuation */ } offset &= ~PAGE_MASK; page = list_entry(head->lru.next, struct page, lru); map = kmap_atomic(page, KM_USER0) + offset; if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ goto init_map; /* jump over SWAP_CONT_MAX checks */ if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */ /* * Think of how you add 1 to 999 */ while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { kunmap_atomic(map, KM_USER0); page = list_entry(page->lru.next, struct page, lru); BUG_ON(page == head); map = kmap_atomic(page, KM_USER0) + offset; } if (*map == SWAP_CONT_MAX) { kunmap_atomic(map, KM_USER0); page = list_entry(page->lru.next, struct page, lru); if (page == head) return false; /* add count continuation */ map = kmap_atomic(page, KM_USER0) + offset; init_map: *map = 0; /* we didn't zero the page */ } *map += 1; kunmap_atomic(map, KM_USER0); page = list_entry(page->lru.prev, struct page, lru); while (page != head) { map = kmap_atomic(page, KM_USER0) + offset; *map = COUNT_CONTINUED; kunmap_atomic(map, KM_USER0); page = list_entry(page->lru.prev, struct page, lru); } return true; /* incremented */ } else { /* decrementing */ /* * Think of how you subtract 1 from 1000 */ BUG_ON(count != COUNT_CONTINUED); while (*map == COUNT_CONTINUED) { kunmap_atomic(map, KM_USER0); page = list_entry(page->lru.next, struct page, lru); BUG_ON(page == head); map = kmap_atomic(page, KM_USER0) + offset; } BUG_ON(*map == 0); *map -= 1; if (*map == 0) count = 0; kunmap_atomic(map, KM_USER0); page = list_entry(page->lru.prev, struct page, lru); while (page != head) { map = kmap_atomic(page, KM_USER0) + offset; *map = SWAP_CONT_MAX | count; count = COUNT_CONTINUED; kunmap_atomic(map, KM_USER0); page = list_entry(page->lru.prev, struct page, lru); } return count == COUNT_CONTINUED; } } /* * free_swap_count_continuations - swapoff free all the continuation pages * appended to the swap_map, after swap_map is quiesced, before vfree'ing it. */ static void free_swap_count_continuations(struct swap_info_struct *si) { pgoff_t offset; for (offset = 0; offset < si->max; offset += PAGE_SIZE) { struct page *head; head = vmalloc_to_page(si->swap_map + offset); if (page_private(head)) { struct list_head *this, *next; list_for_each_safe(this, next, &head->lru) { struct page *page; page = list_entry(this, struct page, lru); list_del(this); __free_page(page); } } } }