diff options
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 1672 |
1 files changed, 1672 insertions, 0 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c new file mode 100644 index 00000000000..a60e0075d55 --- /dev/null +++ b/mm/swapfile.c @@ -0,0 +1,1672 @@ +/* + * linux/mm/swapfile.c + * + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + * Swap reorganised 29.12.95, Stephen Tweedie + */ + +#include <linux/config.h> +#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/syscalls.h> + +#include <asm/pgtable.h> +#include <asm/tlbflush.h> +#include <linux/swapops.h> + +DEFINE_SPINLOCK(swaplock); +unsigned int nr_swapfiles; +long total_swap_pages; +static int swap_overflow; + +EXPORT_SYMBOL(total_swap_pages); + +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}; + +struct swap_info_struct swap_info[MAX_SWAPFILES]; + +static DECLARE_MUTEX(swapon_sem); + +/* + * We need this because the bdev->unplug_fn can sleep and we cannot + * hold swap_list_lock while calling the unplug_fn. And swap_list_lock + * cannot be turned into a semaphore. + */ +static DECLARE_RWSEM(swap_unplug_sem); + +#define SWAPFILE_CLUSTER 256 + +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; + 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 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; + bdi->unplug_io_fn(bdi, page); + } + up_read(&swap_unplug_sem); +} + +static inline int scan_swap_map(struct swap_info_struct *si) +{ + unsigned long offset; + /* + * 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 */ + if (si->cluster_nr) { + while (si->cluster_next <= si->highest_bit) { + offset = si->cluster_next++; + if (si->swap_map[offset]) + continue; + si->cluster_nr--; + goto got_page; + } + } + si->cluster_nr = SWAPFILE_CLUSTER; + + /* try to find an empty (even not aligned) cluster. */ + offset = si->lowest_bit; + check_next_cluster: + if (offset+SWAPFILE_CLUSTER-1 <= si->highest_bit) + { + unsigned long nr; + for (nr = offset; nr < offset+SWAPFILE_CLUSTER; nr++) + if (si->swap_map[nr]) + { + offset = nr+1; + goto check_next_cluster; + } + /* We found a completly empty cluster, so start + * using it. + */ + goto got_page; + } + /* No luck, so now go finegrined as usual. -Andrea */ + for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) { + if (si->swap_map[offset]) + continue; + si->lowest_bit = offset+1; + got_page: + if (offset == si->lowest_bit) + si->lowest_bit++; + if (offset == si->highest_bit) + si->highest_bit--; + if (si->lowest_bit > si->highest_bit) { + si->lowest_bit = si->max; + si->highest_bit = 0; + } + si->swap_map[offset] = 1; + si->inuse_pages++; + nr_swap_pages--; + si->cluster_next = offset+1; + return offset; + } + si->lowest_bit = si->max; + si->highest_bit = 0; + return 0; +} + +swp_entry_t get_swap_page(void) +{ + struct swap_info_struct * p; + unsigned long offset; + swp_entry_t entry; + int type, wrapped = 0; + + entry.val = 0; /* Out of memory */ + swap_list_lock(); + type = swap_list.next; + if (type < 0) + goto out; + if (nr_swap_pages <= 0) + goto out; + + while (1) { + p = &swap_info[type]; + if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) { + swap_device_lock(p); + offset = scan_swap_map(p); + swap_device_unlock(p); + if (offset) { + entry = swp_entry(type,offset); + type = swap_info[type].next; + if (type < 0 || + p->prio != swap_info[type].prio) { + swap_list.next = swap_list.head; + } else { + swap_list.next = type; + } + goto out; + } + } + type = p->next; + if (!wrapped) { + if (type < 0 || p->prio != swap_info[type].prio) { + type = swap_list.head; + wrapped = 1; + } + } else + if (type < 0) + goto out; /* out of swap space */ + } +out: + swap_list_unlock(); + return entry; +} + +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; + swap_list_lock(); + if (p->prio > swap_info[swap_list.next].prio) + swap_list.next = type; + swap_device_lock(p); + 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 void swap_info_put(struct swap_info_struct * p) +{ + swap_device_unlock(p); + swap_list_unlock(); +} + +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; + 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)); + swap_info_put(p); + } +} + +/* + * Check if we're the only user of a swap page, + * when the page is locked. + */ +static int exclusive_swap_page(struct page *page) +{ + int retval = 0; + struct swap_info_struct * p; + swp_entry_t entry; + + entry.val = page->private; + p = swap_info_get(entry); + if (p) { + /* Is the only swap cache user the cache itself? */ + 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) + retval = 1; + write_unlock_irq(&swapper_space.tree_lock); + } + swap_info_put(p); + } + return retval; +} + +/* + * We can use this swap cache entry directly + * if there are no other references to it. + * + * Here "exclusive_swap_page()" does the real + * work, but we opportunistically check whether + * we need to get all the locks first.. + */ +int can_share_swap_page(struct page *page) +{ + int retval = 0; + + if (!PageLocked(page)) + BUG(); + switch (page_count(page)) { + case 3: + if (!PagePrivate(page)) + break; + /* Fallthrough */ + case 2: + if (!PageSwapCache(page)) + break; + retval = exclusive_swap_page(page); + break; + case 1: + if (PageReserved(page)) + break; + retval = 1; + } + return retval; +} + +/* + * 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; + 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); + } + swap_info_put(p); + + 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; + + p = swap_info_get(entry); + if (p) { + if (swap_entry_free(p, swp_offset(entry)) == 1) + page = find_trylock_page(&swapper_space, entry.val); + swap_info_put(p); + } + if (page) { + int one_user; + + BUG_ON(PagePrivate(page)); + page_cache_get(page); + one_user = (page_count(page) == 2); + /* Only cache user (+us), or swap space full? Free it! */ + if (!PageWriteback(page) && (one_user || vm_swap_full())) { + delete_from_swap_cache(page); + SetPageDirty(page); + } + unlock_page(page); + page_cache_release(page); + } +} + +/* + * Always set the resulting pte to be nowrite (the same as COW pages + * after one process has exited). We don't know just how many PTEs will + * share this swap entry, so be cautious and let do_wp_page work out + * what to do if a write is requested later. + * + * vma->vm_mm->page_table_lock is held. + */ +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, 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 *pte; + pte_t swp_pte = swp_entry_to_pte(entry); + + 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))) { + unuse_pte(vma, pte, addr, entry, page); + pte_unmap(pte); + return 1; + } + } while (pte++, addr += PAGE_SIZE, addr != end); + pte_unmap(pte - 1); + return 0; +} + +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)) { + /* + * Our reference to the page stops try_to_unmap_one from + * unmapping its ptes, so swapoff can make progress. + */ + unlock_page(page); + down_read(&mm->mmap_sem); + lock_page(page); + } + spin_lock(&mm->page_table_lock); + for (vma = mm->mmap; vma; vma = vma->vm_next) { + if (vma->anon_vma && unuse_vma(vma, entry, page)) + break; + } + spin_unlock(&mm->page_table_lock); + 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 int find_next_to_unuse(struct swap_info_struct *si, int prev) +{ + int max = si->max; + int i = prev; + int count; + + /* + * No need for swap_device_lock(si) 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_list_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; + 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_return(&mm->mm_users) == 1) { + atomic_dec(&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) { + swap_device_lock(si); + *swap_map = 1; + swap_device_unlock(si); + 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_list_lock must be held on entry and exit. + * Note that mmlist_lock nests inside swap_list_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.prev; + if (lh == &sis->extent_list) + lh = lh->prev; + se = list_entry(lh, struct swap_extent, list); + sis->curr_swap_extent = se; + BUG_ON(se == start_se); /* It *must* be present */ + } +} + +/* + * 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); + } + sis->nr_extents = 0; +} + +/* + * Add a block range (and the corresponding page range) into this swapdev's + * extent list. The extent list is kept sorted in block order. + * + * This function rather assumes that it is called in ascending sector_t order. + * It doesn't look for extent coalescing opportunities. + */ +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.next; /* The highest-addressed block */ + while (lh != &sis->extent_list) { + se = list_entry(lh, struct swap_extent, list); + if (se->start_block + se->nr_pages == start_block && + se->start_page + se->nr_pages == start_page) { + /* Merge it */ + se->nr_pages += nr_pages; + return 0; + } + lh = lh->next; + } + + /* + * 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; + + lh = sis->extent_list.prev; /* The lowest block */ + while (lh != &sis->extent_list) { + se = list_entry(lh, struct swap_extent, list); + if (se->start_block > start_block) + break; + lh = lh->prev; + } + list_add_tail(&new_se->list, lh); + sis->nr_extents++; + return 0; +} + +/* + * 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 hold i_sem 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) +{ + struct inode *inode; + unsigned blocks_per_page; + unsigned long page_no; + unsigned blkbits; + sector_t probe_block; + sector_t last_block; + int ret; + + inode = sis->swap_file->f_mapping->host; + if (S_ISBLK(inode->i_mode)) { + ret = add_swap_extent(sis, 0, sis->max, 0); + 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; + } + } + + /* + * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks + */ + ret = add_swap_extent(sis, page_no, 1, + first_block >> (PAGE_SHIFT - blkbits)); + if (ret) + goto out; + page_no++; + probe_block += blocks_per_page; +reprobe: + continue; + } + ret = 0; + if (page_no == 0) + ret = -EINVAL; + sis->max = page_no; + 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 }; + 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; + swap_list_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; + swap_list_unlock(); + goto out_dput; + } + if (!security_vm_enough_memory(p->pages)) + vm_unacct_memory(p->pages); + else { + err = -ENOMEM; + swap_list_unlock(); + 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; + swap_list_unlock(); + current->flags |= PF_SWAPOFF; + err = try_to_unuse(type); + current->flags &= ~PF_SWAPOFF; + + /* wait for any unplug function to finish */ + down_write(&swap_unplug_sem); + up_write(&swap_unplug_sem); + + if (err) { + /* re-insert swap space back into swap_list */ + swap_list_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; + swap_list_unlock(); + goto out_dput; + } + down(&swapon_sem); + swap_list_lock(); + drain_mmlist(); + swap_device_lock(p); + swap_file = p->swap_file; + p->swap_file = NULL; + p->max = 0; + swap_map = p->swap_map; + p->swap_map = NULL; + p->flags = 0; + destroy_swap_extents(p); + swap_device_unlock(p); + swap_list_unlock(); + up(&swapon_sem); + 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 { + down(&inode->i_sem); + inode->i_flags &= ~S_SWAPFILE; + up(&inode->i_sem); + } + 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; + + down(&swapon_sem); + + 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 = v; + struct swap_info_struct *endptr = swap_info + nr_swapfiles; + + for (++ptr; 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) +{ + up(&swapon_sem); +} + +static int swap_show(struct seq_file *swap, void *v) +{ + struct swap_info_struct *ptr = v; + struct file *file; + int len; + + if (v == swap_info) + seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); + + file = ptr->swap_file; + len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\"); + seq_printf(swap, "%*s%s\t%d\t%ld\t%d\n", + len < 40 ? 40 - len : 1, " ", + S_ISBLK(file->f_dentry->d_inode->i_mode) ? + "partition" : "file\t", + ptr->pages << (PAGE_SHIFT - 10), + ptr->inuse_pages << (PAGE_SHIFT - 10), + ptr->prio); + return 0; +} + +static 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 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; + int nr_good_pages = 0; + 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; + swap_list_lock(); + p = swap_info; + for (type = 0 ; type < nr_swapfiles ; type++,p++) + if (!(p->flags & SWP_USED)) + break; + error = -EPERM; + /* + * Test if adding another swap device is possible. There are + * two limiting factors: 1) the number of bits for the swap + * type swp_entry_t definition and 2) the number of bits for + * the swap type in the swap ptes as defined by the different + * architectures. To honor both limitations a swap entry + * with swap offset 0 and swap type ~0UL is created, encoded + * to a swap pte, decoded to a swp_entry_t again and finally + * the swap type part is extracted. This will mask all bits + * from the initial ~0UL that can't be encoded in either the + * swp_entry_t or the architecture definition of a swap pte. + */ + if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) { + swap_list_unlock(); + goto out; + } + if (type >= nr_swapfiles) + nr_swapfiles = type+1; + INIT_LIST_HEAD(&p->extent_list); + p->flags = SWP_USED; + p->nr_extents = 0; + 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; + spin_lock_init(&p->sdev_lock); + 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; + } + swap_list_unlock(); + 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; + 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; + down(&inode->i_sem); + 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_cache_page(mapping, 0, + (filler_t *)mapping->a_ops->readpage, 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("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; + /* + * 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 (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 = swap_header->info.badpages[i]; + if (page <= 0 || page >= swap_header->info.last_page) + error = -EINVAL; + else + p->swap_map[page] = 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 (swapfilesize && maxpages > swapfilesize) { + printk(KERN_WARNING + "Swap area shorter than signature indicates\n"); + error = -EINVAL; + goto bad_swap; + } + if (!nr_good_pages) { + printk(KERN_WARNING "Empty swap-file\n"); + error = -EINVAL; + goto bad_swap; + } + p->swap_map[0] = SWAP_MAP_BAD; + p->max = maxpages; + p->pages = nr_good_pages; + + error = setup_swap_extents(p); + if (error) + goto bad_swap; + + down(&swapon_sem); + swap_list_lock(); + swap_device_lock(p); + p->flags = SWP_ACTIVE; + nr_swap_pages += nr_good_pages; + total_swap_pages += nr_good_pages; + printk(KERN_INFO "Adding %dk swap on %s. Priority:%d extents:%d\n", + nr_good_pages<<(PAGE_SHIFT-10), name, + p->prio, p->nr_extents); + + /* 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; + } + swap_device_unlock(p); + swap_list_unlock(); + up(&swapon_sem); + error = 0; + goto out; +bad_swap: + if (bdev) { + set_blocksize(bdev, p->old_block_size); + bd_release(bdev); + } +bad_swap_2: + swap_list_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; + swap_list_unlock(); + destroy_swap_extents(p); + 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; + up(&inode->i_sem); + } + return error; +} + +void si_swapinfo(struct sysinfo *val) +{ + unsigned int i; + unsigned long nr_to_be_unused = 0; + + swap_list_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; + swap_list_unlock(); +} + +/* + * 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; + + type = swp_type(entry); + if (type >= nr_swapfiles) + goto bad_file; + p = type + swap_info; + offset = swp_offset(entry); + + swap_device_lock(p); + 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; + } + } + swap_device_unlock(p); +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_device_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 ret = 0, i = 1 << page_cluster; + unsigned long toff; + struct swap_info_struct *swapdev = swp_type(entry) + swap_info; + + if (!page_cluster) /* no readahead */ + return 0; + toff = (swp_offset(entry) >> page_cluster) << page_cluster; + if (!toff) /* first page is swap header */ + toff++, i--; + *offset = toff; + + swap_device_lock(swapdev); + 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); + swap_device_unlock(swapdev); + return ret; +} |