summaryrefslogtreecommitdiffstats
path: root/mm/swap_state.c
diff options
context:
space:
mode:
Diffstat (limited to 'mm/swap_state.c')
-rw-r--r--mm/swap_state.c372
1 files changed, 372 insertions, 0 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
new file mode 100644
index 0000000..3353c90
--- /dev/null
+++ b/mm/swap_state.c
@@ -0,0 +1,372 @@
+/*
+ * linux/mm/swap_state.c
+ *
+ * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
+ * Swap reorganised 29.12.95, Stephen Tweedie
+ *
+ * Rewritten to use page cache, (C) 1998 Stephen Tweedie
+ */
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/buffer_head.h>
+#include <linux/backing-dev.h>
+#include <linux/pagevec.h>
+#include <linux/migrate.h>
+
+#include <asm/pgtable.h>
+
+/*
+ * swapper_space is a fiction, retained to simplify the path through
+ * vmscan's shrink_page_list, to make sync_page look nicer, and to allow
+ * future use of radix_tree tags in the swap cache.
+ */
+static const struct address_space_operations swap_aops = {
+ .writepage = swap_writepage,
+ .sync_page = block_sync_page,
+ .set_page_dirty = __set_page_dirty_nobuffers,
+ .migratepage = migrate_page,
+};
+
+static struct backing_dev_info swap_backing_dev_info = {
+ .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
+ .unplug_io_fn = swap_unplug_io_fn,
+};
+
+struct address_space swapper_space = {
+ .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
+ .tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
+ .a_ops = &swap_aops,
+ .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
+ .backing_dev_info = &swap_backing_dev_info,
+};
+
+#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
+
+static struct {
+ unsigned long add_total;
+ unsigned long del_total;
+ unsigned long find_success;
+ unsigned long find_total;
+} swap_cache_info;
+
+void show_swap_cache_info(void)
+{
+ printk("%lu pages in swap cache\n", total_swapcache_pages);
+ printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
+ swap_cache_info.add_total, swap_cache_info.del_total,
+ swap_cache_info.find_success, swap_cache_info.find_total);
+ printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10));
+ printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
+}
+
+/*
+ * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
+ * but sets SwapCache flag and private instead of mapping and index.
+ */
+int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
+{
+ int error;
+
+ BUG_ON(!PageLocked(page));
+ BUG_ON(PageSwapCache(page));
+ BUG_ON(PagePrivate(page));
+ BUG_ON(!PageSwapBacked(page));
+ error = radix_tree_preload(gfp_mask);
+ if (!error) {
+ page_cache_get(page);
+ SetPageSwapCache(page);
+ set_page_private(page, entry.val);
+
+ spin_lock_irq(&swapper_space.tree_lock);
+ error = radix_tree_insert(&swapper_space.page_tree,
+ entry.val, page);
+ if (likely(!error)) {
+ total_swapcache_pages++;
+ __inc_zone_page_state(page, NR_FILE_PAGES);
+ INC_CACHE_INFO(add_total);
+ }
+ spin_unlock_irq(&swapper_space.tree_lock);
+ radix_tree_preload_end();
+
+ if (unlikely(error)) {
+ set_page_private(page, 0UL);
+ ClearPageSwapCache(page);
+ page_cache_release(page);
+ }
+ }
+ return error;
+}
+
+/*
+ * This must be called only on pages that have
+ * been verified to be in the swap cache.
+ */
+void __delete_from_swap_cache(struct page *page)
+{
+ BUG_ON(!PageLocked(page));
+ BUG_ON(!PageSwapCache(page));
+ BUG_ON(PageWriteback(page));
+ BUG_ON(PagePrivate(page));
+
+ radix_tree_delete(&swapper_space.page_tree, page_private(page));
+ set_page_private(page, 0);
+ ClearPageSwapCache(page);
+ total_swapcache_pages--;
+ __dec_zone_page_state(page, NR_FILE_PAGES);
+ INC_CACHE_INFO(del_total);
+}
+
+/**
+ * add_to_swap - allocate swap space for a page
+ * @page: page we want to move to swap
+ * @gfp_mask: memory allocation flags
+ *
+ * Allocate swap space for the page and add the page to the
+ * swap cache. Caller needs to hold the page lock.
+ */
+int add_to_swap(struct page * page, gfp_t gfp_mask)
+{
+ swp_entry_t entry;
+ int err;
+
+ BUG_ON(!PageLocked(page));
+ BUG_ON(!PageUptodate(page));
+
+ for (;;) {
+ entry = get_swap_page();
+ if (!entry.val)
+ return 0;
+
+ /*
+ * Radix-tree node allocations from PF_MEMALLOC contexts could
+ * completely exhaust the page allocator. __GFP_NOMEMALLOC
+ * stops emergency reserves from being allocated.
+ *
+ * TODO: this could cause a theoretical memory reclaim
+ * deadlock in the swap out path.
+ */
+ /*
+ * Add it to the swap cache and mark it dirty
+ */
+ err = add_to_swap_cache(page, entry,
+ gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN);
+
+ switch (err) {
+ case 0: /* Success */
+ SetPageDirty(page);
+ return 1;
+ case -EEXIST:
+ /* Raced with "speculative" read_swap_cache_async */
+ swap_free(entry);
+ continue;
+ default:
+ /* -ENOMEM radix-tree allocation failure */
+ swap_free(entry);
+ return 0;
+ }
+ }
+}
+
+/*
+ * This must be called only on pages that have
+ * been verified to be in the swap cache and locked.
+ * It will never put the page into the free list,
+ * the caller has a reference on the page.
+ */
+void delete_from_swap_cache(struct page *page)
+{
+ swp_entry_t entry;
+
+ entry.val = page_private(page);
+
+ spin_lock_irq(&swapper_space.tree_lock);
+ __delete_from_swap_cache(page);
+ spin_unlock_irq(&swapper_space.tree_lock);
+
+ swap_free(entry);
+ page_cache_release(page);
+}
+
+/*
+ * If we are the only user, then try to free up the swap cache.
+ *
+ * Its ok to check for PageSwapCache without the page lock
+ * here because we are going to recheck again inside
+ * exclusive_swap_page() _with_ the lock.
+ * - Marcelo
+ */
+static inline void free_swap_cache(struct page *page)
+{
+ if (PageSwapCache(page) && trylock_page(page)) {
+ remove_exclusive_swap_page(page);
+ unlock_page(page);
+ }
+}
+
+/*
+ * Perform a free_page(), also freeing any swap cache associated with
+ * this page if it is the last user of the page.
+ */
+void free_page_and_swap_cache(struct page *page)
+{
+ free_swap_cache(page);
+ page_cache_release(page);
+}
+
+/*
+ * Passed an array of pages, drop them all from swapcache and then release
+ * them. They are removed from the LRU and freed if this is their last use.
+ */
+void free_pages_and_swap_cache(struct page **pages, int nr)
+{
+ struct page **pagep = pages;
+
+ lru_add_drain();
+ while (nr) {
+ int todo = min(nr, PAGEVEC_SIZE);
+ int i;
+
+ for (i = 0; i < todo; i++)
+ free_swap_cache(pagep[i]);
+ release_pages(pagep, todo, 0);
+ pagep += todo;
+ nr -= todo;
+ }
+}
+
+/*
+ * Lookup a swap entry in the swap cache. A found page will be returned
+ * unlocked and with its refcount incremented - we rely on the kernel
+ * lock getting page table operations atomic even if we drop the page
+ * lock before returning.
+ */
+struct page * lookup_swap_cache(swp_entry_t entry)
+{
+ struct page *page;
+
+ page = find_get_page(&swapper_space, entry.val);
+
+ if (page)
+ INC_CACHE_INFO(find_success);
+
+ INC_CACHE_INFO(find_total);
+ return page;
+}
+
+/*
+ * Locate a page of swap in physical memory, reserving swap cache space
+ * and reading the disk if it is not already cached.
+ * A failure return means that either the page allocation failed or that
+ * the swap entry is no longer in use.
+ */
+struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_area_struct *vma, unsigned long addr)
+{
+ struct page *found_page, *new_page = NULL;
+ int err;
+
+ do {
+ /*
+ * First check the swap cache. Since this is normally
+ * called after lookup_swap_cache() failed, re-calling
+ * that would confuse statistics.
+ */
+ found_page = find_get_page(&swapper_space, entry.val);
+ if (found_page)
+ break;
+
+ /*
+ * Get a new page to read into from swap.
+ */
+ if (!new_page) {
+ new_page = alloc_page_vma(gfp_mask, vma, addr);
+ if (!new_page)
+ break; /* Out of memory */
+ }
+
+ /*
+ * Swap entry may have been freed since our caller observed it.
+ */
+ if (!swap_duplicate(entry))
+ break;
+
+ /*
+ * Associate the page with swap entry in the swap cache.
+ * May fail (-EEXIST) if there is already a page associated
+ * with this entry in the swap cache: added by a racing
+ * read_swap_cache_async, or add_to_swap or shmem_writepage
+ * re-using the just freed swap entry for an existing page.
+ * May fail (-ENOMEM) if radix-tree node allocation failed.
+ */
+ __set_page_locked(new_page);
+ SetPageSwapBacked(new_page);
+ err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
+ if (likely(!err)) {
+ /*
+ * Initiate read into locked page and return.
+ */
+ lru_cache_add_anon(new_page);
+ swap_readpage(NULL, new_page);
+ return new_page;
+ }
+ ClearPageSwapBacked(new_page);
+ __clear_page_locked(new_page);
+ swap_free(entry);
+ } while (err != -ENOMEM);
+
+ if (new_page)
+ page_cache_release(new_page);
+ return found_page;
+}
+
+/**
+ * swapin_readahead - swap in pages in hope we need them soon
+ * @entry: swap entry of this memory
+ * @gfp_mask: memory allocation flags
+ * @vma: user vma this address belongs to
+ * @addr: target address for mempolicy
+ *
+ * Returns the struct page for entry and addr, after queueing swapin.
+ *
+ * Primitive swap readahead code. We simply read an aligned block of
+ * (1 << page_cluster) entries in the swap area. This method is chosen
+ * because it doesn't cost us any seek time. We also make sure to queue
+ * the 'original' request together with the readahead ones...
+ *
+ * This has been extended to use the NUMA policies from the mm triggering
+ * the readahead.
+ *
+ * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
+ */
+struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_area_struct *vma, unsigned long addr)
+{
+ int nr_pages;
+ struct page *page;
+ unsigned long offset;
+ unsigned long end_offset;
+
+ /*
+ * Get starting offset for readaround, and number of pages to read.
+ * Adjust starting address by readbehind (for NUMA interleave case)?
+ * No, it's very unlikely that swap layout would follow vma layout,
+ * more likely that neighbouring swap pages came from the same node:
+ * so use the same "addr" to choose the same node for each swap read.
+ */
+ nr_pages = valid_swaphandles(entry, &offset);
+ for (end_offset = offset + nr_pages; offset < end_offset; offset++) {
+ /* Ok, do the async read-ahead now */
+ page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
+ gfp_mask, vma, addr);
+ if (!page)
+ break;
+ page_cache_release(page);
+ }
+ lru_add_drain(); /* Push any new pages onto the LRU now */
+ return read_swap_cache_async(entry, gfp_mask, vma, addr);
+}
OpenPOWER on IntegriCloud