diff options
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 2505 |
1 files changed, 2505 insertions, 0 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c new file mode 100644 index 00000000..38186d96 --- /dev/null +++ b/mm/swapfile.c @@ -0,0 +1,2505 @@ +/* + * 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/shmem_fs.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/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 <linux/poll.h> +#include <linux/oom.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 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 DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait); +/* Activity counter to indicate that a swapon or swapoff has occurred */ +static atomic_t proc_poll_event = ATOMIC_INIT(0); + +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; +} + +/* + * 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, 0); + 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, 0); + 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, 0)) + 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 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 busy. */ + if (vm_swap_full() && 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; + 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}; +} + +/* The only caller of this function is now susupend routine */ +swp_entry_t get_swap_page_of_type(int type) +{ + struct swap_info_struct *si; + pgoff_t offset; + + spin_lock(&swap_lock); + si = swap_info[type]; + if (si && (si->flags & SWP_WRITEOK)) { + nr_swap_pages--; + /* This is called for allocating swap entry, not cache */ + offset = scan_swap_map(si, 1); + if (offset) { + spin_unlock(&swap_lock); + return swp_entry(type, offset); + } + nr_swap_pages++; + } + 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; + + /* + * Once hibernation has begun to create its image of memory, + * there's a danger that one of the calls to try_to_free_swap() + * - most probably a call from __try_to_reclaim_swap() while + * hibernation is allocating its own swap pages for the image, + * but conceivably even a call from memory reclaim - will free + * the swap from a page which has already been recorded in the + * image as a clean swapcache page, and then reuse its swap for + * another page of the image. On waking from hibernation, the + * original page might be freed under memory pressure, then + * later read back in from swap, now with the wrong data. + * + * Hibration suspends storage while it is writing the image + * to disk so check that here. + */ + if (pm_suspended_storage()) + 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 +/* + * 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 *memcg; + spinlock_t *ptl; + pte_t *pte; + int ret = 1; + + if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, + GFP_KERNEL, &memcg)) { + 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(memcg); + 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, memcg); + 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_trans_huge_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; +} + +static void enable_swap_info(struct swap_info_struct *p, int prio, + unsigned char *swap_map) +{ + int i, prev; + + spin_lock(&swap_lock); + if (prio >= 0) + p->prio = prio; + else + p->prio = --least_priority; + p->swap_map = swap_map; + p->flags |= SWP_WRITEOK; + nr_swap_pages += p->pages; + total_swap_pages += p->pages; + + /* 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 = p->type; + else + swap_info[prev]->next = p->type; + spin_unlock(&swap_lock); +} + +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 oom_score_adj; + int i, type, prev; + int err; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + BUG_ON(!current->mm); + + 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_mm(current->mm, 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); + + oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX); + err = try_to_unuse(type); + compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj); + + if (err) { + /* + * reading p->prio and p->swap_map outside the lock is + * safe here because only sys_swapon and sys_swapoff + * change them, and there can be no other sys_swapon or + * sys_swapoff for this swap_info_struct at this point. + */ + /* re-insert swap space back into swap_list */ + enable_swap_info(p, p->prio, p->swap_map); + goto out_dput; + } + + 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); + blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); + } else { + mutex_lock(&inode->i_mutex); + inode->i_flags &= ~S_SWAPFILE; + mutex_unlock(&inode->i_mutex); + } + filp_close(swap_file, NULL); + err = 0; + atomic_inc(&proc_poll_event); + wake_up_interruptible(&proc_poll_wait); + +out_dput: + filp_close(victim, NULL); +out: + return err; +} + +#ifdef CONFIG_PROC_FS +static unsigned swaps_poll(struct file *file, poll_table *wait) +{ + struct seq_file *seq = file->private_data; + + poll_wait(file, &proc_poll_wait, wait); + + if (seq->poll_event != atomic_read(&proc_poll_event)) { + seq->poll_event = atomic_read(&proc_poll_event); + return POLLIN | POLLRDNORM | POLLERR | POLLPRI; + } + + return POLLIN | POLLRDNORM; +} + +/* 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) +{ + struct seq_file *seq; + int ret; + + ret = seq_open(file, &swaps_op); + if (ret) + return ret; + + seq = file->private_data; + seq->poll_event = atomic_read(&proc_poll_event); + return 0; +} + +static const struct file_operations proc_swaps_operations = { + .open = swaps_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, + .poll = swaps_poll, +}; + +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 + +static struct swap_info_struct *alloc_swap_info(void) +{ + struct swap_info_struct *p; + unsigned int type; + + p = kzalloc(sizeof(*p), GFP_KERNEL); + if (!p) + return ERR_PTR(-ENOMEM); + + spin_lock(&swap_lock); + for (type = 0; type < nr_swapfiles; type++) { + if (!(swap_info[type]->flags & SWP_USED)) + break; + } + if (type >= MAX_SWAPFILES) { + spin_unlock(&swap_lock); + kfree(p); + return ERR_PTR(-EPERM); + } + 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); + + return p; +} + +static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) +{ + int error; + + if (S_ISBLK(inode->i_mode)) { + p->bdev = bdgrab(I_BDEV(inode)); + error = blkdev_get(p->bdev, + FMODE_READ | FMODE_WRITE | FMODE_EXCL, + sys_swapon); + if (error < 0) { + p->bdev = NULL; + return -EINVAL; + } + p->old_block_size = block_size(p->bdev); + error = set_blocksize(p->bdev, PAGE_SIZE); + if (error < 0) + return error; + p->flags |= SWP_BLKDEV; + } else if (S_ISREG(inode->i_mode)) { + p->bdev = inode->i_sb->s_bdev; + mutex_lock(&inode->i_mutex); + if (IS_SWAPFILE(inode)) + return -EBUSY; + } else + return -EINVAL; + + return 0; +} + +static unsigned long read_swap_header(struct swap_info_struct *p, + union swap_header *swap_header, + struct inode *inode) +{ + int i; + unsigned long maxpages; + unsigned long swapfilepages; + + if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { + printk(KERN_ERR "Unable to find swap-space signature\n"); + return 0; + } + + /* 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); + return 0; + } + + 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 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; + + if (!maxpages) + return 0; + swapfilepages = i_size_read(inode) >> PAGE_SHIFT; + if (swapfilepages && maxpages > swapfilepages) { + printk(KERN_WARNING + "Swap area shorter than signature indicates\n"); + return 0; + } + if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) + return 0; + if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) + return 0; + + return maxpages; +} + +static int setup_swap_map_and_extents(struct swap_info_struct *p, + union swap_header *swap_header, + unsigned char *swap_map, + unsigned long maxpages, + sector_t *span) +{ + int i; + unsigned int nr_good_pages; + int nr_extents; + + 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) + return -EINVAL; + if (page_nr < maxpages) { + swap_map[page_nr] = SWAP_MAP_BAD; + nr_good_pages--; + } + } + + 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) + return nr_extents; + nr_good_pages = p->pages; + } + if (!nr_good_pages) { + printk(KERN_WARNING "Empty swap-file\n"); + return -EINVAL; + } + + return nr_extents; +} + +SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) +{ + struct swap_info_struct *p; + char *name; + struct file *swap_file = NULL; + struct address_space *mapping; + int i; + int prio; + int error; + union swap_header *swap_header; + int nr_extents; + sector_t span; + unsigned long maxpages; + unsigned char *swap_map = NULL; + struct page *page = NULL; + struct inode *inode = NULL; + + if (swap_flags & ~SWAP_FLAGS_VALID) + return -EINVAL; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + p = alloc_swap_info(); + if (IS_ERR(p)) + return PTR_ERR(p); + + name = getname(specialfile); + if (IS_ERR(name)) { + error = PTR_ERR(name); + name = NULL; + goto bad_swap; + } + swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); + if (IS_ERR(swap_file)) { + error = PTR_ERR(swap_file); + swap_file = NULL; + goto bad_swap; + } + + p->swap_file = swap_file; + mapping = swap_file->f_mapping; + + for (i = 0; i < nr_swapfiles; i++) { + struct swap_info_struct *q = swap_info[i]; + + if (q == p || !q->swap_file) + continue; + if (mapping == q->swap_file->f_mapping) { + error = -EBUSY; + goto bad_swap; + } + } + + inode = mapping->host; + /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */ + error = claim_swapfile(p, inode); + if (unlikely(error)) + goto bad_swap; + + /* + * 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); + + maxpages = read_swap_header(p, swap_header, inode); + if (unlikely(!maxpages)) { + error = -EINVAL; + goto bad_swap; + } + + /* OK, set up the swap map and apply the bad block list */ + swap_map = vzalloc(maxpages); + if (!swap_map) { + error = -ENOMEM; + goto bad_swap; + } + + error = swap_cgroup_swapon(p->type, maxpages); + if (error) + goto bad_swap; + + nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map, + maxpages, &span); + if (unlikely(nr_extents < 0)) { + error = nr_extents; + 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 ((swap_flags & SWAP_FLAG_DISCARD) && discard_swap(p) == 0) + p->flags |= SWP_DISCARDABLE; + } + + mutex_lock(&swapon_mutex); + prio = -1; + if (swap_flags & SWAP_FLAG_PREFER) + prio = + (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; + enable_swap_info(p, prio, swap_map); + + printk(KERN_INFO "Adding %uk swap on %s. " + "Priority:%d extents:%d across:%lluk %s%s\n", + p->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" : ""); + + mutex_unlock(&swapon_mutex); + atomic_inc(&proc_poll_event); + wake_up_interruptible(&proc_poll_wait); + + if (S_ISREG(inode->i_mode)) + inode->i_flags |= S_SWAPFILE; + error = 0; + goto out; +bad_swap: + if (inode && S_ISBLK(inode->i_mode) && p->bdev) { + set_blocksize(p->bdev, p->old_block_size); + blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); + } + destroy_swap_extents(p); + swap_cgroup_swapoff(p->type); + spin_lock(&swap_lock); + p->swap_file = NULL; + p->flags = 0; + spin_unlock(&swap_lock); + vfree(swap_map); + if (swap_file) { + if (inode && S_ISREG(inode->i_mode)) { + mutex_unlock(&inode->i_mutex); + inode = NULL; + } + filp_close(swap_file, NULL); + } +out: + if (page && !IS_ERR(page)) { + kunmap(page); + page_cache_release(page); + } + if (name) + putname(name); + if (inode && S_ISREG(inode->i_mode)) + 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); +} + +/* + * 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) + offset; + count = *map; + kunmap_atomic(map); + + /* + * 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) + 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); + page = list_entry(page->lru.next, struct page, lru); + BUG_ON(page == head); + map = kmap_atomic(page) + offset; + } + if (*map == SWAP_CONT_MAX) { + kunmap_atomic(map); + page = list_entry(page->lru.next, struct page, lru); + if (page == head) + return false; /* add count continuation */ + map = kmap_atomic(page) + offset; +init_map: *map = 0; /* we didn't zero the page */ + } + *map += 1; + kunmap_atomic(map); + page = list_entry(page->lru.prev, struct page, lru); + while (page != head) { + map = kmap_atomic(page) + offset; + *map = COUNT_CONTINUED; + kunmap_atomic(map); + 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); + page = list_entry(page->lru.next, struct page, lru); + BUG_ON(page == head); + map = kmap_atomic(page) + offset; + } + BUG_ON(*map == 0); + *map -= 1; + if (*map == 0) + count = 0; + kunmap_atomic(map); + page = list_entry(page->lru.prev, struct page, lru); + while (page != head) { + map = kmap_atomic(page) + offset; + *map = SWAP_CONT_MAX | count; + count = COUNT_CONTINUED; + kunmap_atomic(map); + 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); + } + } + } +} |