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a2c16d6cb0
If swap entries are to be stored along with struct page pointers in a radix tree, they need to be distinguished as exceptional entries. Most of the handling of swap entries in radix tree will be contained in shmem.c, but a few functions in filemap.c's common code need to check for their appearance: find_get_page(), find_lock_page(), find_get_pages() and find_get_pages_contig(). So as not to slow their fast paths, tuck those checks inside the existing checks for unlikely radix_tree_deref_slot(); except for find_lock_page(), where it is an added test. And make it a BUG in find_get_pages_tag(), which is not applied to tmpfs files. A part of the reason for eliminating shmem_readpage() earlier, was to minimize the places where common code would need to allow for swap entries. The swp_entry_t known to swapfile.c must be massaged into a slightly different form when stored in the radix tree, just as it gets massaged into a pte_t when stored in page tables. In an i386 kernel this limits its information (type and page offset) to 30 bits: given 32 "types" of swapfile and 4kB pagesize, that's a maximum swapfile size of 128GB. Which is less than the 512GB we previously allowed with X86_PAE (where the swap entry can occupy the entire upper 32 bits of a pte_t), but not a new limitation on 32-bit without PAE; and there's not a new limitation on 64-bit (where swap filesize is already limited to 16TB by a 32-bit page offset). Thirty areas of 128GB is probably still enough swap for a 64GB 32-bit machine. Provide swp_to_radix_entry() and radix_to_swp_entry() conversions, and enforce filesize limit in read_swap_header(), just as for ptes. Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2559 lines
65 KiB
C
2559 lines
65 KiB
C
/*
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* linux/mm/swapfile.c
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*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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* Swap reorganised 29.12.95, Stephen Tweedie
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*/
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#include <linux/mm.h>
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#include <linux/hugetlb.h>
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#include <linux/mman.h>
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#include <linux/slab.h>
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#include <linux/kernel_stat.h>
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#include <linux/swap.h>
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#include <linux/vmalloc.h>
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#include <linux/pagemap.h>
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#include <linux/namei.h>
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#include <linux/shmem_fs.h>
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#include <linux/blkdev.h>
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#include <linux/random.h>
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#include <linux/writeback.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/ksm.h>
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#include <linux/rmap.h>
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#include <linux/security.h>
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#include <linux/backing-dev.h>
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#include <linux/mutex.h>
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#include <linux/capability.h>
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#include <linux/syscalls.h>
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#include <linux/memcontrol.h>
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#include <linux/poll.h>
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#include <linux/oom.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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#include <linux/swapops.h>
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#include <linux/page_cgroup.h>
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static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
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unsigned char);
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static void free_swap_count_continuations(struct swap_info_struct *);
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static sector_t map_swap_entry(swp_entry_t, struct block_device**);
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static DEFINE_SPINLOCK(swap_lock);
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static unsigned int nr_swapfiles;
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long nr_swap_pages;
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long total_swap_pages;
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static int least_priority;
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static const char Bad_file[] = "Bad swap file entry ";
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static const char Unused_file[] = "Unused swap file entry ";
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static const char Bad_offset[] = "Bad swap offset entry ";
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static const char Unused_offset[] = "Unused swap offset entry ";
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static struct swap_list_t swap_list = {-1, -1};
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static struct swap_info_struct *swap_info[MAX_SWAPFILES];
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static DEFINE_MUTEX(swapon_mutex);
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static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
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/* Activity counter to indicate that a swapon or swapoff has occurred */
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static atomic_t proc_poll_event = ATOMIC_INIT(0);
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static inline unsigned char swap_count(unsigned char ent)
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{
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return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
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}
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/* returns 1 if swap entry is freed */
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static int
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__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
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{
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swp_entry_t entry = swp_entry(si->type, offset);
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struct page *page;
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int ret = 0;
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page = find_get_page(&swapper_space, entry.val);
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if (!page)
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return 0;
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/*
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* This function is called from scan_swap_map() and it's called
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* by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
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* We have to use trylock for avoiding deadlock. This is a special
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* case and you should use try_to_free_swap() with explicit lock_page()
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* in usual operations.
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*/
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if (trylock_page(page)) {
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ret = try_to_free_swap(page);
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unlock_page(page);
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}
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page_cache_release(page);
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return ret;
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}
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/*
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* swapon tell device that all the old swap contents can be discarded,
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* to allow the swap device to optimize its wear-levelling.
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*/
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static int discard_swap(struct swap_info_struct *si)
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{
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struct swap_extent *se;
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sector_t start_block;
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sector_t nr_blocks;
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int err = 0;
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/* Do not discard the swap header page! */
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se = &si->first_swap_extent;
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start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
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nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
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if (nr_blocks) {
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err = blkdev_issue_discard(si->bdev, start_block,
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nr_blocks, GFP_KERNEL, 0);
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if (err)
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return err;
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cond_resched();
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}
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list_for_each_entry(se, &si->first_swap_extent.list, list) {
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start_block = se->start_block << (PAGE_SHIFT - 9);
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nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
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err = blkdev_issue_discard(si->bdev, start_block,
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nr_blocks, GFP_KERNEL, 0);
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if (err)
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break;
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cond_resched();
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}
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return err; /* That will often be -EOPNOTSUPP */
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}
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/*
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* swap allocation tell device that a cluster of swap can now be discarded,
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* to allow the swap device to optimize its wear-levelling.
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*/
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static void discard_swap_cluster(struct swap_info_struct *si,
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pgoff_t start_page, pgoff_t nr_pages)
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{
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struct swap_extent *se = si->curr_swap_extent;
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int found_extent = 0;
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while (nr_pages) {
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struct list_head *lh;
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if (se->start_page <= start_page &&
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start_page < se->start_page + se->nr_pages) {
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pgoff_t offset = start_page - se->start_page;
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sector_t start_block = se->start_block + offset;
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sector_t nr_blocks = se->nr_pages - offset;
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if (nr_blocks > nr_pages)
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nr_blocks = nr_pages;
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start_page += nr_blocks;
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nr_pages -= nr_blocks;
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if (!found_extent++)
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si->curr_swap_extent = se;
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start_block <<= PAGE_SHIFT - 9;
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nr_blocks <<= PAGE_SHIFT - 9;
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if (blkdev_issue_discard(si->bdev, start_block,
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nr_blocks, GFP_NOIO, 0))
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break;
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}
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lh = se->list.next;
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se = list_entry(lh, struct swap_extent, list);
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}
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}
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static int wait_for_discard(void *word)
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{
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schedule();
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return 0;
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}
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#define SWAPFILE_CLUSTER 256
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#define LATENCY_LIMIT 256
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static unsigned long scan_swap_map(struct swap_info_struct *si,
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unsigned char usage)
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{
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unsigned long offset;
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unsigned long scan_base;
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unsigned long last_in_cluster = 0;
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int latency_ration = LATENCY_LIMIT;
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int found_free_cluster = 0;
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/*
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* We try to cluster swap pages by allocating them sequentially
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* in swap. Once we've allocated SWAPFILE_CLUSTER pages this
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* way, however, we resort to first-free allocation, starting
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* a new cluster. This prevents us from scattering swap pages
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* all over the entire swap partition, so that we reduce
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* overall disk seek times between swap pages. -- sct
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* But we do now try to find an empty cluster. -Andrea
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* And we let swap pages go all over an SSD partition. Hugh
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*/
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si->flags += SWP_SCANNING;
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scan_base = offset = si->cluster_next;
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if (unlikely(!si->cluster_nr--)) {
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if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
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si->cluster_nr = SWAPFILE_CLUSTER - 1;
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goto checks;
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}
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if (si->flags & SWP_DISCARDABLE) {
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/*
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* Start range check on racing allocations, in case
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* they overlap the cluster we eventually decide on
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* (we scan without swap_lock to allow preemption).
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* It's hardly conceivable that cluster_nr could be
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* wrapped during our scan, but don't depend on it.
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*/
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if (si->lowest_alloc)
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goto checks;
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si->lowest_alloc = si->max;
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si->highest_alloc = 0;
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}
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spin_unlock(&swap_lock);
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/*
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* If seek is expensive, start searching for new cluster from
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* start of partition, to minimize the span of allocated swap.
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* But if seek is cheap, search from our current position, so
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* that swap is allocated from all over the partition: if the
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* Flash Translation Layer only remaps within limited zones,
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* we don't want to wear out the first zone too quickly.
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*/
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if (!(si->flags & SWP_SOLIDSTATE))
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scan_base = offset = si->lowest_bit;
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last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
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/* Locate the first empty (unaligned) cluster */
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for (; last_in_cluster <= si->highest_bit; offset++) {
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if (si->swap_map[offset])
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last_in_cluster = offset + SWAPFILE_CLUSTER;
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else if (offset == last_in_cluster) {
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spin_lock(&swap_lock);
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offset -= SWAPFILE_CLUSTER - 1;
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si->cluster_next = offset;
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si->cluster_nr = SWAPFILE_CLUSTER - 1;
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found_free_cluster = 1;
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goto checks;
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}
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if (unlikely(--latency_ration < 0)) {
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cond_resched();
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latency_ration = LATENCY_LIMIT;
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}
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}
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offset = si->lowest_bit;
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last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
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/* Locate the first empty (unaligned) cluster */
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for (; last_in_cluster < scan_base; offset++) {
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if (si->swap_map[offset])
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last_in_cluster = offset + SWAPFILE_CLUSTER;
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else if (offset == last_in_cluster) {
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spin_lock(&swap_lock);
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offset -= SWAPFILE_CLUSTER - 1;
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si->cluster_next = offset;
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si->cluster_nr = SWAPFILE_CLUSTER - 1;
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found_free_cluster = 1;
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goto checks;
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}
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if (unlikely(--latency_ration < 0)) {
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cond_resched();
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latency_ration = LATENCY_LIMIT;
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}
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}
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offset = scan_base;
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spin_lock(&swap_lock);
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si->cluster_nr = SWAPFILE_CLUSTER - 1;
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si->lowest_alloc = 0;
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}
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checks:
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if (!(si->flags & SWP_WRITEOK))
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goto no_page;
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if (!si->highest_bit)
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goto no_page;
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if (offset > si->highest_bit)
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scan_base = offset = si->lowest_bit;
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/* reuse swap entry of cache-only swap if not busy. */
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if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
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int swap_was_freed;
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spin_unlock(&swap_lock);
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swap_was_freed = __try_to_reclaim_swap(si, offset);
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spin_lock(&swap_lock);
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/* entry was freed successfully, try to use this again */
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if (swap_was_freed)
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goto checks;
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goto scan; /* check next one */
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}
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if (si->swap_map[offset])
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goto scan;
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if (offset == si->lowest_bit)
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si->lowest_bit++;
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if (offset == si->highest_bit)
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si->highest_bit--;
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si->inuse_pages++;
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if (si->inuse_pages == si->pages) {
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si->lowest_bit = si->max;
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si->highest_bit = 0;
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}
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si->swap_map[offset] = usage;
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si->cluster_next = offset + 1;
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si->flags -= SWP_SCANNING;
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if (si->lowest_alloc) {
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/*
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* Only set when SWP_DISCARDABLE, and there's a scan
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* for a free cluster in progress or just completed.
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*/
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if (found_free_cluster) {
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/*
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* To optimize wear-levelling, discard the
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* old data of the cluster, taking care not to
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* discard any of its pages that have already
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* been allocated by racing tasks (offset has
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* already stepped over any at the beginning).
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*/
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if (offset < si->highest_alloc &&
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si->lowest_alloc <= last_in_cluster)
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last_in_cluster = si->lowest_alloc - 1;
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si->flags |= SWP_DISCARDING;
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spin_unlock(&swap_lock);
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if (offset < last_in_cluster)
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discard_swap_cluster(si, offset,
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last_in_cluster - offset + 1);
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spin_lock(&swap_lock);
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si->lowest_alloc = 0;
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si->flags &= ~SWP_DISCARDING;
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smp_mb(); /* wake_up_bit advises this */
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wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
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} else if (si->flags & SWP_DISCARDING) {
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/*
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* Delay using pages allocated by racing tasks
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* until the whole discard has been issued. We
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* could defer that delay until swap_writepage,
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* but it's easier to keep this self-contained.
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*/
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spin_unlock(&swap_lock);
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wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
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wait_for_discard, TASK_UNINTERRUPTIBLE);
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spin_lock(&swap_lock);
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} else {
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/*
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* Note pages allocated by racing tasks while
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* scan for a free cluster is in progress, so
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* that its final discard can exclude them.
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*/
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if (offset < si->lowest_alloc)
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si->lowest_alloc = offset;
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if (offset > si->highest_alloc)
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si->highest_alloc = offset;
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}
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}
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return offset;
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scan:
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spin_unlock(&swap_lock);
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while (++offset <= si->highest_bit) {
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if (!si->swap_map[offset]) {
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spin_lock(&swap_lock);
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goto checks;
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}
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if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
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spin_lock(&swap_lock);
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goto checks;
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}
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if (unlikely(--latency_ration < 0)) {
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cond_resched();
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latency_ration = LATENCY_LIMIT;
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}
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}
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offset = si->lowest_bit;
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while (++offset < scan_base) {
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if (!si->swap_map[offset]) {
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spin_lock(&swap_lock);
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goto checks;
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}
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if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
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spin_lock(&swap_lock);
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goto checks;
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}
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if (unlikely(--latency_ration < 0)) {
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cond_resched();
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latency_ration = LATENCY_LIMIT;
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}
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}
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spin_lock(&swap_lock);
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no_page:
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si->flags -= SWP_SCANNING;
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return 0;
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}
|
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|
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swp_entry_t get_swap_page(void)
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{
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struct swap_info_struct *si;
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pgoff_t offset;
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int type, next;
|
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int wrapped = 0;
|
|
|
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spin_lock(&swap_lock);
|
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if (nr_swap_pages <= 0)
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goto noswap;
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nr_swap_pages--;
|
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|
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for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
|
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si = swap_info[type];
|
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next = si->next;
|
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if (next < 0 ||
|
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(!wrapped && si->prio != swap_info[next]->prio)) {
|
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next = swap_list.head;
|
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wrapped++;
|
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}
|
|
|
|
if (!si->highest_bit)
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continue;
|
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if (!(si->flags & SWP_WRITEOK))
|
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continue;
|
|
|
|
swap_list.next = next;
|
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/* This is called for allocating swap entry for cache */
|
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offset = scan_swap_map(si, SWAP_HAS_CACHE);
|
|
if (offset) {
|
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spin_unlock(&swap_lock);
|
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return swp_entry(type, offset);
|
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}
|
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next = swap_list.next;
|
|
}
|
|
|
|
nr_swap_pages++;
|
|
noswap:
|
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spin_unlock(&swap_lock);
|
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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.
|
|
*
|
|
* Hibernation clears bits from gfp_allowed_mask to prevent
|
|
* memory reclaim from writing to disk, so check that here.
|
|
*/
|
|
if (!(gfp_allowed_mask & __GFP_IO))
|
|
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 *ptr;
|
|
spinlock_t *ptl;
|
|
pte_t *pte;
|
|
int ret = 1;
|
|
|
|
if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
|
|
ret = -ENOMEM;
|
|
goto out_nolock;
|
|
}
|
|
|
|
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
|
|
if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
|
|
if (ret > 0)
|
|
mem_cgroup_cancel_charge_swapin(ptr);
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
|
|
dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
|
|
inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
|
|
get_page(page);
|
|
set_pte_at(vma->vm_mm, addr, pte,
|
|
pte_mkold(mk_pte(page, vma->vm_page_prot)));
|
|
page_add_anon_rmap(page, vma, addr);
|
|
mem_cgroup_commit_charge_swapin(page, ptr);
|
|
swap_free(entry);
|
|
/*
|
|
* Move the page to the active list so it is not
|
|
* immediately swapped out again after swapon.
|
|
*/
|
|
activate_page(page);
|
|
out:
|
|
pte_unmap_unlock(pte, ptl);
|
|
out_nolock:
|
|
return ret;
|
|
}
|
|
|
|
static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
|
|
unsigned long addr, unsigned long end,
|
|
swp_entry_t entry, struct page *page)
|
|
{
|
|
pte_t swp_pte = swp_entry_to_pte(entry);
|
|
pte_t *pte;
|
|
int ret = 0;
|
|
|
|
/*
|
|
* We don't actually need pte lock while scanning for swp_pte: since
|
|
* we hold page lock and mmap_sem, swp_pte cannot be inserted into the
|
|
* page table while we're scanning; though it could get zapped, and on
|
|
* some architectures (e.g. x86_32 with PAE) we might catch a glimpse
|
|
* of unmatched parts which look like swp_pte, so unuse_pte must
|
|
* recheck under pte lock. Scanning without pte lock lets it be
|
|
* preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
|
|
*/
|
|
pte = pte_offset_map(pmd, addr);
|
|
do {
|
|
/*
|
|
* swapoff spends a _lot_ of time in this loop!
|
|
* Test inline before going to call unuse_pte.
|
|
*/
|
|
if (unlikely(pte_same(*pte, swp_pte))) {
|
|
pte_unmap(pte);
|
|
ret = unuse_pte(vma, pmd, addr, entry, page);
|
|
if (ret)
|
|
goto out;
|
|
pte = pte_offset_map(pmd, addr);
|
|
}
|
|
} while (pte++, addr += PAGE_SIZE, addr != end);
|
|
pte_unmap(pte - 1);
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
|
|
unsigned long addr, unsigned long end,
|
|
swp_entry_t entry, struct page *page)
|
|
{
|
|
pmd_t *pmd;
|
|
unsigned long next;
|
|
int ret;
|
|
|
|
pmd = pmd_offset(pud, addr);
|
|
do {
|
|
next = pmd_addr_end(addr, end);
|
|
if (unlikely(pmd_trans_huge(*pmd)))
|
|
continue;
|
|
if (pmd_none_or_clear_bad(pmd))
|
|
continue;
|
|
ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
|
|
if (ret)
|
|
return ret;
|
|
} while (pmd++, addr = next, addr != end);
|
|
return 0;
|
|
}
|
|
|
|
static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
|
|
unsigned long addr, unsigned long end,
|
|
swp_entry_t entry, struct page *page)
|
|
{
|
|
pud_t *pud;
|
|
unsigned long next;
|
|
int ret;
|
|
|
|
pud = pud_offset(pgd, addr);
|
|
do {
|
|
next = pud_addr_end(addr, end);
|
|
if (pud_none_or_clear_bad(pud))
|
|
continue;
|
|
ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
|
|
if (ret)
|
|
return ret;
|
|
} while (pud++, addr = next, addr != end);
|
|
return 0;
|
|
}
|
|
|
|
static int unuse_vma(struct vm_area_struct *vma,
|
|
swp_entry_t entry, struct page *page)
|
|
{
|
|
pgd_t *pgd;
|
|
unsigned long addr, end, next;
|
|
int ret;
|
|
|
|
if (page_anon_vma(page)) {
|
|
addr = page_address_in_vma(page, vma);
|
|
if (addr == -EFAULT)
|
|
return 0;
|
|
else
|
|
end = addr + PAGE_SIZE;
|
|
} else {
|
|
addr = vma->vm_start;
|
|
end = vma->vm_end;
|
|
}
|
|
|
|
pgd = pgd_offset(vma->vm_mm, addr);
|
|
do {
|
|
next = pgd_addr_end(addr, end);
|
|
if (pgd_none_or_clear_bad(pgd))
|
|
continue;
|
|
ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
|
|
if (ret)
|
|
return ret;
|
|
} while (pgd++, addr = next, addr != end);
|
|
return 0;
|
|
}
|
|
|
|
static int unuse_mm(struct mm_struct *mm,
|
|
swp_entry_t entry, struct page *page)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
int ret = 0;
|
|
|
|
if (!down_read_trylock(&mm->mmap_sem)) {
|
|
/*
|
|
* Activate page so shrink_inactive_list is unlikely to unmap
|
|
* its ptes while lock is dropped, so swapoff can make progress.
|
|
*/
|
|
activate_page(page);
|
|
unlock_page(page);
|
|
down_read(&mm->mmap_sem);
|
|
lock_page(page);
|
|
}
|
|
for (vma = mm->mmap; vma; vma = vma->vm_next) {
|
|
if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
|
|
break;
|
|
}
|
|
up_read(&mm->mmap_sem);
|
|
return (ret < 0)? ret: 0;
|
|
}
|
|
|
|
/*
|
|
* Scan swap_map from current position to next entry still in use.
|
|
* Recycle to start on reaching the end, returning 0 when empty.
|
|
*/
|
|
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
|
|
unsigned int prev)
|
|
{
|
|
unsigned int max = si->max;
|
|
unsigned int i = prev;
|
|
unsigned char count;
|
|
|
|
/*
|
|
* No need for swap_lock here: we're just looking
|
|
* for whether an entry is in use, not modifying it; false
|
|
* hits are okay, and sys_swapoff() has already prevented new
|
|
* allocations from this area (while holding swap_lock).
|
|
*/
|
|
for (;;) {
|
|
if (++i >= max) {
|
|
if (!prev) {
|
|
i = 0;
|
|
break;
|
|
}
|
|
/*
|
|
* No entries in use at top of swap_map,
|
|
* loop back to start and recheck there.
|
|
*/
|
|
max = prev + 1;
|
|
prev = 0;
|
|
i = 1;
|
|
}
|
|
count = si->swap_map[i];
|
|
if (count && swap_count(count) != SWAP_MAP_BAD)
|
|
break;
|
|
}
|
|
return i;
|
|
}
|
|
|
|
/*
|
|
* We completely avoid races by reading each swap page in advance,
|
|
* and then search for the process using it. All the necessary
|
|
* page table adjustments can then be made atomically.
|
|
*/
|
|
static int try_to_unuse(unsigned int type)
|
|
{
|
|
struct swap_info_struct *si = swap_info[type];
|
|
struct mm_struct *start_mm;
|
|
unsigned char *swap_map;
|
|
unsigned char swcount;
|
|
struct page *page;
|
|
swp_entry_t entry;
|
|
unsigned int i = 0;
|
|
int retval = 0;
|
|
|
|
/*
|
|
* When searching mms for an entry, a good strategy is to
|
|
* start at the first mm we freed the previous entry from
|
|
* (though actually we don't notice whether we or coincidence
|
|
* freed the entry). Initialize this start_mm with a hold.
|
|
*
|
|
* A simpler strategy would be to start at the last mm we
|
|
* freed the previous entry from; but that would take less
|
|
* advantage of mmlist ordering, which clusters forked mms
|
|
* together, child after parent. If we race with dup_mmap(), we
|
|
* prefer to resolve parent before child, lest we miss entries
|
|
* duplicated after we scanned child: using last mm would invert
|
|
* that.
|
|
*/
|
|
start_mm = &init_mm;
|
|
atomic_inc(&init_mm.mm_users);
|
|
|
|
/*
|
|
* Keep on scanning until all entries have gone. Usually,
|
|
* one pass through swap_map is enough, but not necessarily:
|
|
* there are races when an instance of an entry might be missed.
|
|
*/
|
|
while ((i = find_next_to_unuse(si, i)) != 0) {
|
|
if (signal_pending(current)) {
|
|
retval = -EINTR;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Get a page for the entry, using the existing swap
|
|
* cache page if there is one. Otherwise, get a clean
|
|
* page and read the swap into it.
|
|
*/
|
|
swap_map = &si->swap_map[i];
|
|
entry = swp_entry(type, i);
|
|
page = read_swap_cache_async(entry,
|
|
GFP_HIGHUSER_MOVABLE, NULL, 0);
|
|
if (!page) {
|
|
/*
|
|
* Either swap_duplicate() failed because entry
|
|
* has been freed independently, and will not be
|
|
* reused since sys_swapoff() already disabled
|
|
* allocation from here, or alloc_page() failed.
|
|
*/
|
|
if (!*swap_map)
|
|
continue;
|
|
retval = -ENOMEM;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Don't hold on to start_mm if it looks like exiting.
|
|
*/
|
|
if (atomic_read(&start_mm->mm_users) == 1) {
|
|
mmput(start_mm);
|
|
start_mm = &init_mm;
|
|
atomic_inc(&init_mm.mm_users);
|
|
}
|
|
|
|
/*
|
|
* Wait for and lock page. When do_swap_page races with
|
|
* try_to_unuse, do_swap_page can handle the fault much
|
|
* faster than try_to_unuse can locate the entry. This
|
|
* apparently redundant "wait_on_page_locked" lets try_to_unuse
|
|
* defer to do_swap_page in such a case - in some tests,
|
|
* do_swap_page and try_to_unuse repeatedly compete.
|
|
*/
|
|
wait_on_page_locked(page);
|
|
wait_on_page_writeback(page);
|
|
lock_page(page);
|
|
wait_on_page_writeback(page);
|
|
|
|
/*
|
|
* Remove all references to entry.
|
|
*/
|
|
swcount = *swap_map;
|
|
if (swap_count(swcount) == SWAP_MAP_SHMEM) {
|
|
retval = shmem_unuse(entry, page);
|
|
/* page has already been unlocked and released */
|
|
if (retval < 0)
|
|
break;
|
|
continue;
|
|
}
|
|
if (swap_count(swcount) && start_mm != &init_mm)
|
|
retval = unuse_mm(start_mm, entry, page);
|
|
|
|
if (swap_count(*swap_map)) {
|
|
int set_start_mm = (*swap_map >= swcount);
|
|
struct list_head *p = &start_mm->mmlist;
|
|
struct mm_struct *new_start_mm = start_mm;
|
|
struct mm_struct *prev_mm = start_mm;
|
|
struct mm_struct *mm;
|
|
|
|
atomic_inc(&new_start_mm->mm_users);
|
|
atomic_inc(&prev_mm->mm_users);
|
|
spin_lock(&mmlist_lock);
|
|
while (swap_count(*swap_map) && !retval &&
|
|
(p = p->next) != &start_mm->mmlist) {
|
|
mm = list_entry(p, struct mm_struct, mmlist);
|
|
if (!atomic_inc_not_zero(&mm->mm_users))
|
|
continue;
|
|
spin_unlock(&mmlist_lock);
|
|
mmput(prev_mm);
|
|
prev_mm = mm;
|
|
|
|
cond_resched();
|
|
|
|
swcount = *swap_map;
|
|
if (!swap_count(swcount)) /* any usage ? */
|
|
;
|
|
else if (mm == &init_mm)
|
|
set_start_mm = 1;
|
|
else
|
|
retval = unuse_mm(mm, entry, page);
|
|
|
|
if (set_start_mm && *swap_map < swcount) {
|
|
mmput(new_start_mm);
|
|
atomic_inc(&mm->mm_users);
|
|
new_start_mm = mm;
|
|
set_start_mm = 0;
|
|
}
|
|
spin_lock(&mmlist_lock);
|
|
}
|
|
spin_unlock(&mmlist_lock);
|
|
mmput(prev_mm);
|
|
mmput(start_mm);
|
|
start_mm = new_start_mm;
|
|
}
|
|
if (retval) {
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* If a reference remains (rare), we would like to leave
|
|
* the page in the swap cache; but try_to_unmap could
|
|
* then re-duplicate the entry once we drop page lock,
|
|
* so we might loop indefinitely; also, that page could
|
|
* not be swapped out to other storage meanwhile. So:
|
|
* delete from cache even if there's another reference,
|
|
* after ensuring that the data has been saved to disk -
|
|
* since if the reference remains (rarer), it will be
|
|
* read from disk into another page. Splitting into two
|
|
* pages would be incorrect if swap supported "shared
|
|
* private" pages, but they are handled by tmpfs files.
|
|
*
|
|
* Given how unuse_vma() targets one particular offset
|
|
* in an anon_vma, once the anon_vma has been determined,
|
|
* this splitting happens to be just what is needed to
|
|
* handle where KSM pages have been swapped out: re-reading
|
|
* is unnecessarily slow, but we can fix that later on.
|
|
*/
|
|
if (swap_count(*swap_map) &&
|
|
PageDirty(page) && PageSwapCache(page)) {
|
|
struct writeback_control wbc = {
|
|
.sync_mode = WB_SYNC_NONE,
|
|
};
|
|
|
|
swap_writepage(page, &wbc);
|
|
lock_page(page);
|
|
wait_on_page_writeback(page);
|
|
}
|
|
|
|
/*
|
|
* It is conceivable that a racing task removed this page from
|
|
* swap cache just before we acquired the page lock at the top,
|
|
* or while we dropped it in unuse_mm(). The page might even
|
|
* be back in swap cache on another swap area: that we must not
|
|
* delete, since it may not have been written out to swap yet.
|
|
*/
|
|
if (PageSwapCache(page) &&
|
|
likely(page_private(page) == entry.val))
|
|
delete_from_swap_cache(page);
|
|
|
|
/*
|
|
* So we could skip searching mms once swap count went
|
|
* to 1, we did not mark any present ptes as dirty: must
|
|
* mark page dirty so shrink_page_list will preserve it.
|
|
*/
|
|
SetPageDirty(page);
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
|
|
/*
|
|
* Make sure that we aren't completely killing
|
|
* interactive performance.
|
|
*/
|
|
cond_resched();
|
|
}
|
|
|
|
mmput(start_mm);
|
|
return retval;
|
|
}
|
|
|
|
/*
|
|
* After a successful try_to_unuse, if no swap is now in use, we know
|
|
* we can empty the mmlist. swap_lock must be held on entry and exit.
|
|
* Note that mmlist_lock nests inside swap_lock, and an mm must be
|
|
* added to the mmlist just after page_duplicate - before would be racy.
|
|
*/
|
|
static void drain_mmlist(void)
|
|
{
|
|
struct list_head *p, *next;
|
|
unsigned int type;
|
|
|
|
for (type = 0; type < nr_swapfiles; type++)
|
|
if (swap_info[type]->inuse_pages)
|
|
return;
|
|
spin_lock(&mmlist_lock);
|
|
list_for_each_safe(p, next, &init_mm.mmlist)
|
|
list_del_init(p);
|
|
spin_unlock(&mmlist_lock);
|
|
}
|
|
|
|
/*
|
|
* Use this swapdev's extent info to locate the (PAGE_SIZE) block which
|
|
* corresponds to page offset for the specified swap entry.
|
|
* Note that the type of this function is sector_t, but it returns page offset
|
|
* into the bdev, not sector offset.
|
|
*/
|
|
static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
|
|
{
|
|
struct swap_info_struct *sis;
|
|
struct swap_extent *start_se;
|
|
struct swap_extent *se;
|
|
pgoff_t offset;
|
|
|
|
sis = swap_info[swp_type(entry)];
|
|
*bdev = sis->bdev;
|
|
|
|
offset = swp_offset(entry);
|
|
start_se = sis->curr_swap_extent;
|
|
se = start_se;
|
|
|
|
for ( ; ; ) {
|
|
struct list_head *lh;
|
|
|
|
if (se->start_page <= offset &&
|
|
offset < (se->start_page + se->nr_pages)) {
|
|
return se->start_block + (offset - se->start_page);
|
|
}
|
|
lh = se->list.next;
|
|
se = list_entry(lh, struct swap_extent, list);
|
|
sis->curr_swap_extent = se;
|
|
BUG_ON(se == start_se); /* It *must* be present */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Returns the page offset into bdev for the specified page's swap entry.
|
|
*/
|
|
sector_t map_swap_page(struct page *page, struct block_device **bdev)
|
|
{
|
|
swp_entry_t entry;
|
|
entry.val = page_private(page);
|
|
return map_swap_entry(entry, bdev);
|
|
}
|
|
|
|
/*
|
|
* Free all of a swapdev's extent information
|
|
*/
|
|
static void destroy_swap_extents(struct swap_info_struct *sis)
|
|
{
|
|
while (!list_empty(&sis->first_swap_extent.list)) {
|
|
struct swap_extent *se;
|
|
|
|
se = list_entry(sis->first_swap_extent.list.next,
|
|
struct swap_extent, list);
|
|
list_del(&se->list);
|
|
kfree(se);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Add a block range (and the corresponding page range) into this swapdev's
|
|
* extent list. The extent list is kept sorted in page order.
|
|
*
|
|
* This function rather assumes that it is called in ascending page order.
|
|
*/
|
|
static int
|
|
add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
|
|
unsigned long nr_pages, sector_t start_block)
|
|
{
|
|
struct swap_extent *se;
|
|
struct swap_extent *new_se;
|
|
struct list_head *lh;
|
|
|
|
if (start_page == 0) {
|
|
se = &sis->first_swap_extent;
|
|
sis->curr_swap_extent = se;
|
|
se->start_page = 0;
|
|
se->nr_pages = nr_pages;
|
|
se->start_block = start_block;
|
|
return 1;
|
|
} else {
|
|
lh = sis->first_swap_extent.list.prev; /* Highest extent */
|
|
se = list_entry(lh, struct swap_extent, list);
|
|
BUG_ON(se->start_page + se->nr_pages != start_page);
|
|
if (se->start_block + se->nr_pages == start_block) {
|
|
/* Merge it */
|
|
se->nr_pages += nr_pages;
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* No merge. Insert a new extent, preserving ordering.
|
|
*/
|
|
new_se = kmalloc(sizeof(*se), GFP_KERNEL);
|
|
if (new_se == NULL)
|
|
return -ENOMEM;
|
|
new_se->start_page = start_page;
|
|
new_se->nr_pages = nr_pages;
|
|
new_se->start_block = start_block;
|
|
|
|
list_add_tail(&new_se->list, &sis->first_swap_extent.list);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* A `swap extent' is a simple thing which maps a contiguous range of pages
|
|
* onto a contiguous range of disk blocks. An ordered list of swap extents
|
|
* is built at swapon time and is then used at swap_writepage/swap_readpage
|
|
* time for locating where on disk a page belongs.
|
|
*
|
|
* If the swapfile is an S_ISBLK block device, a single extent is installed.
|
|
* This is done so that the main operating code can treat S_ISBLK and S_ISREG
|
|
* swap files identically.
|
|
*
|
|
* Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
|
|
* extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
|
|
* swapfiles are handled *identically* after swapon time.
|
|
*
|
|
* For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
|
|
* and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
|
|
* some stray blocks are found which do not fall within the PAGE_SIZE alignment
|
|
* requirements, they are simply tossed out - we will never use those blocks
|
|
* for swapping.
|
|
*
|
|
* For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
|
|
* prevents root from shooting her foot off by ftruncating an in-use swapfile,
|
|
* which will scribble on the fs.
|
|
*
|
|
* The amount of disk space which a single swap extent represents varies.
|
|
* Typically it is in the 1-4 megabyte range. So we can have hundreds of
|
|
* extents in the list. To avoid much list walking, we cache the previous
|
|
* search location in `curr_swap_extent', and start new searches from there.
|
|
* This is extremely effective. The average number of iterations in
|
|
* map_swap_page() has been measured at about 0.3 per page. - akpm.
|
|
*/
|
|
static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
|
|
{
|
|
struct inode *inode;
|
|
unsigned blocks_per_page;
|
|
unsigned long page_no;
|
|
unsigned blkbits;
|
|
sector_t probe_block;
|
|
sector_t last_block;
|
|
sector_t lowest_block = -1;
|
|
sector_t highest_block = 0;
|
|
int nr_extents = 0;
|
|
int ret;
|
|
|
|
inode = sis->swap_file->f_mapping->host;
|
|
if (S_ISBLK(inode->i_mode)) {
|
|
ret = add_swap_extent(sis, 0, sis->max, 0);
|
|
*span = sis->pages;
|
|
goto out;
|
|
}
|
|
|
|
blkbits = inode->i_blkbits;
|
|
blocks_per_page = PAGE_SIZE >> blkbits;
|
|
|
|
/*
|
|
* Map all the blocks into the extent list. This code doesn't try
|
|
* to be very smart.
|
|
*/
|
|
probe_block = 0;
|
|
page_no = 0;
|
|
last_block = i_size_read(inode) >> blkbits;
|
|
while ((probe_block + blocks_per_page) <= last_block &&
|
|
page_no < sis->max) {
|
|
unsigned block_in_page;
|
|
sector_t first_block;
|
|
|
|
first_block = bmap(inode, probe_block);
|
|
if (first_block == 0)
|
|
goto bad_bmap;
|
|
|
|
/*
|
|
* It must be PAGE_SIZE aligned on-disk
|
|
*/
|
|
if (first_block & (blocks_per_page - 1)) {
|
|
probe_block++;
|
|
goto reprobe;
|
|
}
|
|
|
|
for (block_in_page = 1; block_in_page < blocks_per_page;
|
|
block_in_page++) {
|
|
sector_t block;
|
|
|
|
block = bmap(inode, probe_block + block_in_page);
|
|
if (block == 0)
|
|
goto bad_bmap;
|
|
if (block != first_block + block_in_page) {
|
|
/* Discontiguity */
|
|
probe_block++;
|
|
goto reprobe;
|
|
}
|
|
}
|
|
|
|
first_block >>= (PAGE_SHIFT - blkbits);
|
|
if (page_no) { /* exclude the header page */
|
|
if (first_block < lowest_block)
|
|
lowest_block = first_block;
|
|
if (first_block > highest_block)
|
|
highest_block = first_block;
|
|
}
|
|
|
|
/*
|
|
* We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
|
|
*/
|
|
ret = add_swap_extent(sis, page_no, 1, first_block);
|
|
if (ret < 0)
|
|
goto out;
|
|
nr_extents += ret;
|
|
page_no++;
|
|
probe_block += blocks_per_page;
|
|
reprobe:
|
|
continue;
|
|
}
|
|
ret = nr_extents;
|
|
*span = 1 + highest_block - lowest_block;
|
|
if (page_no == 0)
|
|
page_no = 1; /* force Empty message */
|
|
sis->max = page_no;
|
|
sis->pages = page_no - 1;
|
|
sis->highest_bit = page_no - 1;
|
|
out:
|
|
return ret;
|
|
bad_bmap:
|
|
printk(KERN_ERR "swapon: swapfile has holes\n");
|
|
ret = -EINVAL;
|
|
goto out;
|
|
}
|
|
|
|
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;
|
|
|
|
pathname = getname(specialfile);
|
|
err = PTR_ERR(pathname);
|
|
if (IS_ERR(pathname))
|
|
goto out;
|
|
|
|
victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
|
|
putname(pathname);
|
|
err = PTR_ERR(victim);
|
|
if (IS_ERR(victim))
|
|
goto out;
|
|
|
|
mapping = victim->f_mapping;
|
|
prev = -1;
|
|
spin_lock(&swap_lock);
|
|
for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
|
|
p = swap_info[type];
|
|
if (p->flags & SWP_WRITEOK) {
|
|
if (p->swap_file->f_mapping == mapping)
|
|
break;
|
|
}
|
|
prev = type;
|
|
}
|
|
if (type < 0) {
|
|
err = -EINVAL;
|
|
spin_unlock(&swap_lock);
|
|
goto out_dput;
|
|
}
|
|
if (!security_vm_enough_memory(p->pages))
|
|
vm_unacct_memory(p->pages);
|
|
else {
|
|
err = -ENOMEM;
|
|
spin_unlock(&swap_lock);
|
|
goto out_dput;
|
|
}
|
|
if (prev < 0)
|
|
swap_list.head = p->next;
|
|
else
|
|
swap_info[prev]->next = p->next;
|
|
if (type == swap_list.next) {
|
|
/* just pick something that's safe... */
|
|
swap_list.next = swap_list.head;
|
|
}
|
|
if (p->prio < 0) {
|
|
for (i = p->next; i >= 0; i = swap_info[i]->next)
|
|
swap_info[i]->prio = p->prio--;
|
|
least_priority++;
|
|
}
|
|
nr_swap_pages -= p->pages;
|
|
total_swap_pages -= p->pages;
|
|
p->flags &= ~SWP_WRITEOK;
|
|
spin_unlock(&swap_lock);
|
|
|
|
oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
|
|
err = try_to_unuse(type);
|
|
test_set_oom_score_adj(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 three 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
|
|
* the different architectures, and 3) the number of free bits
|
|
* in an exceptional radix_tree entry. 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. Then the same is done for a radix_tree entry.
|
|
*/
|
|
maxpages = swp_offset(pte_to_swp_entry(
|
|
swp_entry_to_pte(swp_entry(0, ~0UL))));
|
|
maxpages = swp_offset(radix_to_swp_entry(
|
|
swp_to_radix_entry(swp_entry(0, maxpages)))) + 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 (!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 (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* swap_lock prevents swap_map being freed. Don't grab an extra
|
|
* reference on the swaphandle, it doesn't matter if it becomes unused.
|
|
*/
|
|
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
|
|
{
|
|
struct swap_info_struct *si;
|
|
int our_page_cluster = page_cluster;
|
|
pgoff_t target, toff;
|
|
pgoff_t base, end;
|
|
int nr_pages = 0;
|
|
|
|
if (!our_page_cluster) /* no readahead */
|
|
return 0;
|
|
|
|
si = swap_info[swp_type(entry)];
|
|
target = swp_offset(entry);
|
|
base = (target >> our_page_cluster) << our_page_cluster;
|
|
end = base + (1 << our_page_cluster);
|
|
if (!base) /* first page is swap header */
|
|
base++;
|
|
|
|
spin_lock(&swap_lock);
|
|
if (end > si->max) /* don't go beyond end of map */
|
|
end = si->max;
|
|
|
|
/* Count contiguous allocated slots above our target */
|
|
for (toff = target; ++toff < end; nr_pages++) {
|
|
/* Don't read in free or bad pages */
|
|
if (!si->swap_map[toff])
|
|
break;
|
|
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
|
|
break;
|
|
}
|
|
/* Count contiguous allocated slots below our target */
|
|
for (toff = target; --toff >= base; nr_pages++) {
|
|
/* Don't read in free or bad pages */
|
|
if (!si->swap_map[toff])
|
|
break;
|
|
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
|
|
break;
|
|
}
|
|
spin_unlock(&swap_lock);
|
|
|
|
/*
|
|
* Indicate starting offset, and return number of pages to get:
|
|
* if only 1, say 0, since there's then no readahead to be done.
|
|
*/
|
|
*offset = ++toff;
|
|
return nr_pages? ++nr_pages: 0;
|
|
}
|
|
|
|
/*
|
|
* add_swap_count_continuation - called when a swap count is duplicated
|
|
* beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
|
|
* page of the original vmalloc'ed swap_map, to hold the continuation count
|
|
* (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
|
|
* again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
|
|
*
|
|
* These continuation pages are seldom referenced: the common paths all work
|
|
* on the original swap_map, only referring to a continuation page when the
|
|
* low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
|
|
*
|
|
* add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
|
|
* page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
|
|
* can be called after dropping locks.
|
|
*/
|
|
int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
|
|
{
|
|
struct swap_info_struct *si;
|
|
struct page *head;
|
|
struct page *page;
|
|
struct page *list_page;
|
|
pgoff_t offset;
|
|
unsigned char count;
|
|
|
|
/*
|
|
* When debugging, it's easier to use __GFP_ZERO here; but it's better
|
|
* for latency not to zero a page while GFP_ATOMIC and holding locks.
|
|
*/
|
|
page = alloc_page(gfp_mask | __GFP_HIGHMEM);
|
|
|
|
si = swap_info_get(entry);
|
|
if (!si) {
|
|
/*
|
|
* An acceptable race has occurred since the failing
|
|
* __swap_duplicate(): the swap entry has been freed,
|
|
* perhaps even the whole swap_map cleared for swapoff.
|
|
*/
|
|
goto outer;
|
|
}
|
|
|
|
offset = swp_offset(entry);
|
|
count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
|
|
|
|
if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
|
|
/*
|
|
* The higher the swap count, the more likely it is that tasks
|
|
* will race to add swap count continuation: we need to avoid
|
|
* over-provisioning.
|
|
*/
|
|
goto out;
|
|
}
|
|
|
|
if (!page) {
|
|
spin_unlock(&swap_lock);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
/*
|
|
* We are fortunate that although vmalloc_to_page uses pte_offset_map,
|
|
* no architecture is using highmem pages for kernel pagetables: so it
|
|
* will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
|
|
*/
|
|
head = vmalloc_to_page(si->swap_map + offset);
|
|
offset &= ~PAGE_MASK;
|
|
|
|
/*
|
|
* Page allocation does not initialize the page's lru field,
|
|
* but it does always reset its private field.
|
|
*/
|
|
if (!page_private(head)) {
|
|
BUG_ON(count & COUNT_CONTINUED);
|
|
INIT_LIST_HEAD(&head->lru);
|
|
set_page_private(head, SWP_CONTINUED);
|
|
si->flags |= SWP_CONTINUED;
|
|
}
|
|
|
|
list_for_each_entry(list_page, &head->lru, lru) {
|
|
unsigned char *map;
|
|
|
|
/*
|
|
* If the previous map said no continuation, but we've found
|
|
* a continuation page, free our allocation and use this one.
|
|
*/
|
|
if (!(count & COUNT_CONTINUED))
|
|
goto out;
|
|
|
|
map = kmap_atomic(list_page, KM_USER0) + offset;
|
|
count = *map;
|
|
kunmap_atomic(map, KM_USER0);
|
|
|
|
/*
|
|
* If this continuation count now has some space in it,
|
|
* free our allocation and use this one.
|
|
*/
|
|
if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
|
|
goto out;
|
|
}
|
|
|
|
list_add_tail(&page->lru, &head->lru);
|
|
page = NULL; /* now it's attached, don't free it */
|
|
out:
|
|
spin_unlock(&swap_lock);
|
|
outer:
|
|
if (page)
|
|
__free_page(page);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* swap_count_continued - when the original swap_map count is incremented
|
|
* from SWAP_MAP_MAX, check if there is already a continuation page to carry
|
|
* into, carry if so, or else fail until a new continuation page is allocated;
|
|
* when the original swap_map count is decremented from 0 with continuation,
|
|
* borrow from the continuation and report whether it still holds more.
|
|
* Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
|
|
*/
|
|
static bool swap_count_continued(struct swap_info_struct *si,
|
|
pgoff_t offset, unsigned char count)
|
|
{
|
|
struct page *head;
|
|
struct page *page;
|
|
unsigned char *map;
|
|
|
|
head = vmalloc_to_page(si->swap_map + offset);
|
|
if (page_private(head) != SWP_CONTINUED) {
|
|
BUG_ON(count & COUNT_CONTINUED);
|
|
return false; /* need to add count continuation */
|
|
}
|
|
|
|
offset &= ~PAGE_MASK;
|
|
page = list_entry(head->lru.next, struct page, lru);
|
|
map = kmap_atomic(page, KM_USER0) + offset;
|
|
|
|
if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
|
|
goto init_map; /* jump over SWAP_CONT_MAX checks */
|
|
|
|
if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
|
|
/*
|
|
* Think of how you add 1 to 999
|
|
*/
|
|
while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
|
|
kunmap_atomic(map, KM_USER0);
|
|
page = list_entry(page->lru.next, struct page, lru);
|
|
BUG_ON(page == head);
|
|
map = kmap_atomic(page, KM_USER0) + offset;
|
|
}
|
|
if (*map == SWAP_CONT_MAX) {
|
|
kunmap_atomic(map, KM_USER0);
|
|
page = list_entry(page->lru.next, struct page, lru);
|
|
if (page == head)
|
|
return false; /* add count continuation */
|
|
map = kmap_atomic(page, KM_USER0) + offset;
|
|
init_map: *map = 0; /* we didn't zero the page */
|
|
}
|
|
*map += 1;
|
|
kunmap_atomic(map, KM_USER0);
|
|
page = list_entry(page->lru.prev, struct page, lru);
|
|
while (page != head) {
|
|
map = kmap_atomic(page, KM_USER0) + offset;
|
|
*map = COUNT_CONTINUED;
|
|
kunmap_atomic(map, KM_USER0);
|
|
page = list_entry(page->lru.prev, struct page, lru);
|
|
}
|
|
return true; /* incremented */
|
|
|
|
} else { /* decrementing */
|
|
/*
|
|
* Think of how you subtract 1 from 1000
|
|
*/
|
|
BUG_ON(count != COUNT_CONTINUED);
|
|
while (*map == COUNT_CONTINUED) {
|
|
kunmap_atomic(map, KM_USER0);
|
|
page = list_entry(page->lru.next, struct page, lru);
|
|
BUG_ON(page == head);
|
|
map = kmap_atomic(page, KM_USER0) + offset;
|
|
}
|
|
BUG_ON(*map == 0);
|
|
*map -= 1;
|
|
if (*map == 0)
|
|
count = 0;
|
|
kunmap_atomic(map, KM_USER0);
|
|
page = list_entry(page->lru.prev, struct page, lru);
|
|
while (page != head) {
|
|
map = kmap_atomic(page, KM_USER0) + offset;
|
|
*map = SWAP_CONT_MAX | count;
|
|
count = COUNT_CONTINUED;
|
|
kunmap_atomic(map, KM_USER0);
|
|
page = list_entry(page->lru.prev, struct page, lru);
|
|
}
|
|
return count == COUNT_CONTINUED;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* free_swap_count_continuations - swapoff free all the continuation pages
|
|
* appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
|
|
*/
|
|
static void free_swap_count_continuations(struct swap_info_struct *si)
|
|
{
|
|
pgoff_t offset;
|
|
|
|
for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
|
|
struct page *head;
|
|
head = vmalloc_to_page(si->swap_map + offset);
|
|
if (page_private(head)) {
|
|
struct list_head *this, *next;
|
|
list_for_each_safe(this, next, &head->lru) {
|
|
struct page *page;
|
|
page = list_entry(this, struct page, lru);
|
|
list_del(this);
|
|
__free_page(page);
|
|
}
|
|
}
|
|
}
|
|
}
|