/* * 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/writeback.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> #include <linux/init.h> #include <linux/module.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 <asm/pgtable.h> #include <asm/tlbflush.h> #include <linux/swapops.h> DEFINE_SPINLOCK(swap_lock); unsigned int nr_swapfiles; long total_swap_pages; static int swap_overflow; 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 "; struct swap_list_t swap_list = {-1, -1}; static struct swap_info_struct swap_info[MAX_SWAPFILES]; static DEFINE_MUTEX(swapon_mutex); /* * 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); } #define SWAPFILE_CLUSTER 256 #define LATENCY_LIMIT 256 static inline unsigned long scan_swap_map(struct swap_info_struct *si) { unsigned long offset, last_in_cluster; int latency_ration = LATENCY_LIMIT; /* * 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 */ si->flags += SWP_SCANNING; if (unlikely(!si->cluster_nr)) { si->cluster_nr = SWAPFILE_CLUSTER - 1; if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) goto lowest; spin_unlock(&swap_lock); 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); si->cluster_next = offset-SWAPFILE_CLUSTER+1; goto cluster; } if (unlikely(--latency_ration < 0)) { cond_resched(); latency_ration = LATENCY_LIMIT; } } spin_lock(&swap_lock); goto lowest; } si->cluster_nr--; cluster: offset = si->cluster_next; if (offset > si->highest_bit) lowest: offset = si->lowest_bit; checks: if (!(si->flags & SWP_WRITEOK)) goto no_page; if (!si->highest_bit) goto no_page; if (!si->swap_map[offset]) { 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] = 1; si->cluster_next = offset + 1; si->flags -= SWP_SCANNING; return offset; } spin_unlock(&swap_lock); while (++offset <= si->highest_bit) { if (!si->swap_map[offset]) { spin_lock(&swap_lock); goto checks; } if (unlikely(--latency_ration < 0)) { cond_resched(); latency_ration = LATENCY_LIMIT; } } spin_lock(&swap_lock); goto lowest; 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; offset = scan_swap_map(si); 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}; } 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->flags & SWP_WRITEOK) { nr_swap_pages--; offset = scan_swap_map(si); 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 int swap_entry_free(struct swap_info_struct *p, unsigned long offset) { int count = p->swap_map[offset]; if (count < SWAP_MAP_MAX) { count--; p->swap_map[offset] = count; if (!count) { if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit) p->highest_bit = offset; if (p->prio > swap_info[swap_list.next].prio) swap_list.next = p - swap_info; nr_swap_pages++; p->inuse_pages--; } } return count; } /* * 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, swp_offset(entry)); spin_unlock(&swap_lock); } } /* * How many references to page are currently swapped out? */ 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) { /* Subtract the 1 for the swap cache itself */ count = p->swap_map[swp_offset(entry)] - 1; spin_unlock(&swap_lock); } return count; } /* * We can use this swap cache entry directly * if there are no other references to it. */ int can_share_swap_page(struct page *page) { int count; BUG_ON(!PageLocked(page)); count = page_mapcount(page); if (count <= 1 && PageSwapCache(page)) count += page_swapcount(page); return count == 1; } /* * Work out if there are any other processes sharing this * swap cache page. Free it if you can. Return success. */ int remove_exclusive_swap_page(struct page *page) { int retval; struct swap_info_struct * p; swp_entry_t entry; BUG_ON(PagePrivate(page)); BUG_ON(!PageLocked(page)); if (!PageSwapCache(page)) return 0; if (PageWriteback(page)) return 0; if (page_count(page) != 2) /* 2: us + cache */ return 0; entry.val = page_private(page); p = swap_info_get(entry); if (!p) return 0; /* Is the only swap cache user the cache itself? */ retval = 0; if (p->swap_map[swp_offset(entry)] == 1) { /* Recheck the page count with the swapcache lock held.. */ write_lock_irq(&swapper_space.tree_lock); if ((page_count(page) == 2) && !PageWriteback(page)) { __delete_from_swap_cache(page); SetPageDirty(page); retval = 1; } write_unlock_irq(&swapper_space.tree_lock); } spin_unlock(&swap_lock); if (retval) { swap_free(entry); page_cache_release(page); } return retval; } /* * Free the swap entry like above, but also try to * free the page cache entry if it is the last user. */ void free_swap_and_cache(swp_entry_t entry) { struct swap_info_struct * p; struct page *page = NULL; if (is_migration_entry(entry)) return; p = swap_info_get(entry); if (p) { if (swap_entry_free(p, swp_offset(entry)) == 1) { page = find_get_page(&swapper_space, entry.val); if (page && unlikely(TestSetPageLocked(page))) { page_cache_release(page); page = NULL; } } spin_unlock(&swap_lock); } if (page) { int one_user; BUG_ON(PagePrivate(page)); one_user = (page_count(page) == 2); /* Only cache user (+us), or swap space full? Free it! */ /* Also recheck PageSwapCache after page is locked (above) */ if (PageSwapCache(page) && !PageWriteback(page) && (one_user || vm_swap_full())) { delete_from_swap_cache(page); SetPageDirty(page); } unlock_page(page); page_cache_release(page); } } #ifdef CONFIG_SOFTWARE_SUSPEND /* * 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 = NULL; int i; if (device) bdev = bdget(device); spin_lock(&swap_lock); for (i = 0; i < nr_swapfiles; i++) { struct swap_info_struct *sis = swap_info + i; if (!(sis->flags & SWP_WRITEOK)) continue; if (!bdev) { spin_unlock(&swap_lock); return i; } if (bdev == sis->bdev) { struct swap_extent *se; se = list_entry(sis->extent_list.next, struct swap_extent, list); if (se->start_block == offset) { spin_unlock(&swap_lock); bdput(bdev); return i; } } } spin_unlock(&swap_lock); if (bdev) bdput(bdev); return -ENODEV; } /* * 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; if (type < nr_swapfiles) { spin_lock(&swap_lock); if (swap_info[type].flags & SWP_WRITEOK) { n = swap_info[type].pages; if (free) n -= swap_info[type].inuse_pages; } spin_unlock(&swap_lock); } return n; } #endif /* * 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 void unuse_pte(struct vm_area_struct *vma, pte_t *pte, unsigned long addr, swp_entry_t entry, struct page *page) { inc_mm_counter(vma->vm_mm, anon_rss); 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); swap_free(entry); /* * Move the page to the active list so it is not * immediately swapped out again after swapon. */ activate_page(page); } 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; spinlock_t *ptl; int found = 0; pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 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))) { unuse_pte(vma, pte++, addr, entry, page); found = 1; break; } } while (pte++, addr += PAGE_SIZE, addr != end); pte_unmap_unlock(pte - 1, ptl); return found; } 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; pmd = pmd_offset(pud, addr); do { next = pmd_addr_end(addr, end); if (pmd_none_or_clear_bad(pmd)) continue; if (unuse_pte_range(vma, pmd, addr, next, entry, page)) return 1; } 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; pud = pud_offset(pgd, addr); do { next = pud_addr_end(addr, end); if (pud_none_or_clear_bad(pud)) continue; if (unuse_pmd_range(vma, pud, addr, next, entry, page)) return 1; } 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; if (page->mapping) { 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; if (unuse_pud_range(vma, pgd, addr, next, entry, page)) return 1; } 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; if (!down_read_trylock(&mm->mmap_sem)) { /* * Activate page so shrink_cache 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 && unuse_vma(vma, entry, page)) break; } up_read(&mm->mmap_sem); /* * Currently unuse_mm cannot fail, but leave error handling * at call sites for now, since we change it from time to time. */ return 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; int 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 && 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 short *swap_map; unsigned short swcount; struct page *page; swp_entry_t entry; unsigned int i = 0; int retval = 0; int reset_overflow = 0; int shmem; /* * 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. Though it's only a serious concern when an overflowed * swap count is reset from SWAP_MAP_MAX, preventing a rescan. */ 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, 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. * Whenever we reach init_mm, there's no address space * to search, but use it as a reminder to search shmem. */ shmem = 0; swcount = *swap_map; if (swcount > 1) { if (start_mm == &init_mm) shmem = shmem_unuse(entry, page); else retval = unuse_mm(start_mm, entry, page); } if (*swap_map > 1) { 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_map > 1 && !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 (swcount <= 1) ; else if (mm == &init_mm) { set_start_mm = 1; shmem = shmem_unuse(entry, page); } 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; } /* * How could swap count reach 0x7fff when the maximum * pid is 0x7fff, and there's no way to repeat a swap * page within an mm (except in shmem, where it's the * shared object which takes the reference count)? * We believe SWAP_MAP_MAX cannot occur in Linux 2.4. * * If that's wrong, then we should worry more about * exit_mmap() and do_munmap() cases described above: * we might be resetting SWAP_MAP_MAX too early here. * We know "Undead"s can happen, they're okay, so don't * report them; but do report if we reset SWAP_MAP_MAX. */ if (*swap_map == SWAP_MAP_MAX) { spin_lock(&swap_lock); *swap_map = 1; spin_unlock(&swap_lock); reset_overflow = 1; } /* * 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. * * Note shmem_unuse already deleted a swappage from * the swap cache, unless the move to filepage failed: * in which case it left swappage in cache, lowered its * swap count to pass quickly through the loops above, * and now we must reincrement count to try again later. */ if ((*swap_map > 1) && 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); } if (PageSwapCache(page)) { if (shmem) swap_duplicate(entry); else 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_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); if (reset_overflow) { printk(KERN_WARNING "swapoff: cleared swap entry overflow\n"); swap_overflow = 0; } 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 i; for (i = 0; i < nr_swapfiles; i++) if (swap_info[i].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 `offset'. */ sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset) { struct swap_extent *se = sis->curr_swap_extent; struct swap_extent *start_se = 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; if (lh == &sis->extent_list) lh = lh->next; se = list_entry(lh, struct swap_extent, list); sis->curr_swap_extent = se; BUG_ON(se == start_se); /* It *must* be present */ } } #ifdef CONFIG_SOFTWARE_SUSPEND /* * 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 swap_type, pgoff_t offset) { struct swap_info_struct *sis; if (swap_type >= nr_swapfiles) return 0; sis = swap_info + swap_type; return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0; } #endif /* CONFIG_SOFTWARE_SUSPEND */ /* * Free all of a swapdev's extent information */ static void destroy_swap_extents(struct swap_info_struct *sis) { while (!list_empty(&sis->extent_list)) { struct swap_extent *se; se = list_entry(sis->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; lh = sis->extent_list.prev; /* The highest page extent */ if (lh != &sis->extent_list) { 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->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 done; } 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; done: sis->curr_swap_extent = list_entry(sis->extent_list.prev, struct swap_extent, list); goto out; bad_bmap: printk(KERN_ERR "swapon: swapfile has holes\n"); ret = -EINVAL; out: return ret; } #if 0 /* We don't need this yet */ #include <linux/backing-dev.h> int page_queue_congested(struct page *page) { struct backing_dev_info *bdi; BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */ if (PageSwapCache(page)) { swp_entry_t entry = { .val = page_private(page) }; struct swap_info_struct *sis; sis = get_swap_info_struct(swp_type(entry)); bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info; } else bdi = page->mapping->backing_dev_info; return bdi_write_congested(bdi); } #endif asmlinkage long sys_swapoff(const char __user * specialfile) { struct swap_info_struct * p = NULL; unsigned short *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_ACTIVE) == SWP_ACTIVE) { 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; } nr_swap_pages -= p->pages; total_swap_pages -= p->pages; p->flags &= ~SWP_WRITEOK; spin_unlock(&swap_lock); current->flags |= PF_SWAPOFF; err = try_to_unuse(type); current->flags &= ~PF_SWAPOFF; if (err) { /* re-insert swap space back into swap_list */ spin_lock(&swap_lock); for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next) if (p->prio >= swap_info[i].prio) break; p->next = i; if (prev < 0) swap_list.head = swap_list.next = p - swap_info; else swap_info[prev].next = p - swap_info; 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); 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); 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 *ptr = swap_info; int i; loff_t l = *pos; mutex_lock(&swapon_mutex); if (!l) return SEQ_START_TOKEN; for (i = 0; i < nr_swapfiles; i++, ptr++) { if (!(ptr->flags & SWP_USED) || !ptr->swap_map) continue; if (!--l) return ptr; } return NULL; } static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) { struct swap_info_struct *ptr; struct swap_info_struct *endptr = swap_info + nr_swapfiles; if (v == SEQ_START_TOKEN) ptr = swap_info; else { ptr = v; ptr++; } for (; ptr < endptr; ptr++) { if (!(ptr->flags & SWP_USED) || !ptr->swap_map) continue; ++*pos; return ptr; } 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 *ptr = v; struct file *file; int len; if (ptr == SEQ_START_TOKEN) { seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); return 0; } file = ptr->swap_file; len = seq_path(swap, file->f_path.mnt, file->f_path.dentry, " \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", ptr->pages << (PAGE_SHIFT - 10), ptr->inuse_pages << (PAGE_SHIFT - 10), ptr->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) { struct proc_dir_entry *entry; entry = create_proc_entry("swaps", 0, NULL); if (entry) entry->proc_fops = &proc_swaps_operations; return 0; } __initcall(procswaps_init); #endif /* CONFIG_PROC_FS */ /* * Written 01/25/92 by Simmule Turner, heavily changed by Linus. * * The swapon system call */ asmlinkage long sys_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; static int least_priority; union swap_header *swap_header = NULL; int swap_header_version; unsigned int nr_good_pages = 0; int nr_extents = 0; sector_t span; unsigned long maxpages = 1; int swapfilesize; unsigned short *swap_map; struct page *page = NULL; struct inode *inode = NULL; int did_down = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; spin_lock(&swap_lock); p = swap_info; for (type = 0 ; type < nr_swapfiles ; type++,p++) if (!(p->flags & SWP_USED)) break; error = -EPERM; if (type >= MAX_SWAPFILES) { spin_unlock(&swap_lock); goto out; } if (type >= nr_swapfiles) nr_swapfiles = type+1; INIT_LIST_HEAD(&p->extent_list); p->flags = SWP_USED; p->swap_file = NULL; p->old_block_size = 0; p->swap_map = NULL; p->lowest_bit = 0; p->highest_bit = 0; p->cluster_nr = 0; p->inuse_pages = 0; p->next = -1; if (swap_flags & SWAP_FLAG_PREFER) { p->prio = (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT; } else { p->prio = --least_priority; } 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; } 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; } swapfilesize = 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; } wait_on_page_locked(page); if (!PageUptodate(page)) goto bad_swap; kmap(page); swap_header = page_address(page); if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10)) swap_header_version = 1; else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10)) swap_header_version = 2; else { printk(KERN_ERR "Unable to find swap-space signature\n"); error = -EINVAL; goto bad_swap; } switch (swap_header_version) { case 1: printk(KERN_ERR "version 0 swap is no longer supported. " "Use mkswap -v1 %s\n", name); error = -EINVAL; goto bad_swap; case 2: /* Check the swap header's sub-version and the size of the swap file and bad block lists */ 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; /* * 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; p->highest_bit = maxpages - 1; error = -EINVAL; if (!maxpages) goto bad_swap; if (swapfilesize && maxpages > swapfilesize) { 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 */ if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) { error = -ENOMEM; goto bad_swap; } error = 0; memset(p->swap_map, 0, maxpages * sizeof(short)); for (i = 0; i < swap_header->info.nr_badpages; i++) { int page_nr = swap_header->info.badpages[i]; if (page_nr <= 0 || page_nr >= swap_header->info.last_page) error = -EINVAL; else p->swap_map[page_nr] = SWAP_MAP_BAD; } nr_good_pages = swap_header->info.last_page - swap_header->info.nr_badpages - 1 /* header page */; if (error) goto bad_swap; } if (nr_good_pages) { p->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; } mutex_lock(&swapon_mutex); spin_lock(&swap_lock); p->flags = SWP_ACTIVE; 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\n", nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10)); /* 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 - swap_info; } else { swap_info[prev].next = p - swap_info; } 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); bad_swap_2: spin_lock(&swap_lock); swap_map = p->swap_map; p->swap_file = NULL; p->swap_map = NULL; p->flags = 0; if (!(swap_flags & SWAP_FLAG_PREFER)) ++least_priority; 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 i; unsigned long nr_to_be_unused = 0; spin_lock(&swap_lock); for (i = 0; i < nr_swapfiles; i++) { if (!(swap_info[i].flags & SWP_USED) || (swap_info[i].flags & SWP_WRITEOK)) continue; nr_to_be_unused += swap_info[i].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. * * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as * "permanent", but will be reclaimed by the next swapoff. */ int swap_duplicate(swp_entry_t entry) { struct swap_info_struct * p; unsigned long offset, type; int result = 0; if (is_migration_entry(entry)) return 1; type = swp_type(entry); if (type >= nr_swapfiles) goto bad_file; p = type + swap_info; offset = swp_offset(entry); spin_lock(&swap_lock); if (offset < p->max && p->swap_map[offset]) { if (p->swap_map[offset] < SWAP_MAP_MAX - 1) { p->swap_map[offset]++; result = 1; } else if (p->swap_map[offset] <= SWAP_MAP_MAX) { if (swap_overflow++ < 5) printk(KERN_WARNING "swap_dup: swap entry overflow\n"); p->swap_map[offset] = SWAP_MAP_MAX; result = 1; } } spin_unlock(&swap_lock); out: return result; bad_file: printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); goto out; } struct swap_info_struct * get_swap_info_struct(unsigned type) { return &swap_info[type]; } /* * 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) { int our_page_cluster = page_cluster; int ret = 0, i = 1 << our_page_cluster; unsigned long toff; struct swap_info_struct *swapdev = swp_type(entry) + swap_info; if (!our_page_cluster) /* no readahead */ return 0; toff = (swp_offset(entry) >> our_page_cluster) << our_page_cluster; if (!toff) /* first page is swap header */ toff++, i--; *offset = toff; spin_lock(&swap_lock); do { /* Don't read-ahead past the end of the swap area */ if (toff >= swapdev->max) break; /* Don't read in free or bad pages */ if (!swapdev->swap_map[toff]) break; if (swapdev->swap_map[toff] == SWAP_MAP_BAD) break; toff++; ret++; } while (--i); spin_unlock(&swap_lock); return ret; }