1 files changed, 382 insertions, 0 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
new file mode 100644
index 000000000000..a063a902ed03
--- /dev/null
+++ b/mm/swap_state.c
@@ -0,0 +1,382 @@
+/*
+ *  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/init.h>
+#include <linux/pagemap.h>
+#include <linux/buffer_head.h>
+#include <linux/backing-dev.h>
+
+#include <asm/pgtable.h>
+
+/*
+ * swapper_space is a fiction, retained to simplify the path through
+ * vmscan's shrink_list, to make sync_page look nicer, and to allow
+ * future use of radix_tree tags in the swap cache.
+ */
+static struct address_space_operations swap_aops = {
+	.writepage	= swap_writepage,
+	.sync_page	= block_sync_page,
+	.set_page_dirty	= __set_page_dirty_nobuffers,
+};
+
+static struct backing_dev_info swap_backing_dev_info = {
+	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+	.unplug_io_fn	= swap_unplug_io_fn,
+};
+
+struct address_space swapper_space = {
+	.page_tree	= RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
+	.tree_lock	= RW_LOCK_UNLOCKED,
+	.a_ops		= &swap_aops,
+	.i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
+	.backing_dev_info = &swap_backing_dev_info,
+};
+EXPORT_SYMBOL(swapper_space);
+
+#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;
+	unsigned long noent_race;
+	unsigned long exist_race;
+} swap_cache_info;
+
+void show_swap_cache_info(void)
+{
+	printk("Swap cache: add %lu, delete %lu, find %lu/%lu, race %lu+%lu\n",
+		swap_cache_info.add_total, swap_cache_info.del_total,
+		swap_cache_info.find_success, swap_cache_info.find_total,
+		swap_cache_info.noent_race, swap_cache_info.exist_race);
+	printk("Free swap  = %lukB\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 on swapper_space,
+ * but sets SwapCache flag and private instead of mapping and index.
+ */
+static int __add_to_swap_cache(struct page *page,
+		swp_entry_t entry, int gfp_mask)
+{
+	int error;
+
+	BUG_ON(PageSwapCache(page));
+	BUG_ON(PagePrivate(page));
+	error = radix_tree_preload(gfp_mask);
+	if (!error) {
+		write_lock_irq(&swapper_space.tree_lock);
+		error = radix_tree_insert(&swapper_space.page_tree,
+						entry.val, page);
+		if (!error) {
+			page_cache_get(page);
+			SetPageLocked(page);
+			SetPageSwapCache(page);
+			page->private = entry.val;
+			total_swapcache_pages++;
+			pagecache_acct(1);
+		}
+		write_unlock_irq(&swapper_space.tree_lock);
+		radix_tree_preload_end();
+	}
+	return error;
+}
+
+static int add_to_swap_cache(struct page *page, swp_entry_t entry)
+{
+	int error;
+
+	if (!swap_duplicate(entry)) {
+		INC_CACHE_INFO(noent_race);
+		return -ENOENT;
+	}
+	error = __add_to_swap_cache(page, entry, GFP_KERNEL);
+	/*
+	 * Anon pages are already on the LRU, we don't run lru_cache_add here.
+	 */
+	if (error) {
+		swap_free(entry);
+		if (error == -EEXIST)
+			INC_CACHE_INFO(exist_race);
+		return error;
+	}
+	INC_CACHE_INFO(add_total);
+	return 0;
+}
+
+/*
+ * 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));
+
+	radix_tree_delete(&swapper_space.page_tree, page->private);
+	page->private = 0;
+	ClearPageSwapCache(page);
+	total_swapcache_pages--;
+	pagecache_acct(-1);
+	INC_CACHE_INFO(del_total);
+}
+
+/**
+ * add_to_swap - allocate swap space for a page
+ * @page: page we want to move to swap
+ *
+ * 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)
+{
+	swp_entry_t entry;
+	int pf_flags;
+	int err;
+
+	if (!PageLocked(page))
+		BUG();
+
+	for (;;) {
+		entry = get_swap_page();
+		if (!entry.val)
+			return 0;
+
+		/* Radix-tree node allocations are performing
+		 * GFP_ATOMIC allocations under PF_MEMALLOC.  
+		 * They can completely exhaust the page allocator.  
+		 *
+		 * So PF_MEMALLOC is dropped here.  This causes the slab 
+		 * allocations to fail earlier, so radix-tree nodes will 
+		 * then be allocated from the mempool reserves.
+		 *
+		 * We're still using __GFP_HIGH for radix-tree node
+		 * allocations, so some of the emergency pools are available,
+		 * just not all of them.
+		 */
+
+		pf_flags = current->flags;
+		current->flags &= ~PF_MEMALLOC;
+
+		/*
+		 * Add it to the swap cache and mark it dirty
+		 */
+		err = __add_to_swap_cache(page, entry, GFP_ATOMIC|__GFP_NOWARN);
+
+		if (pf_flags & PF_MEMALLOC)
+			current->flags |= PF_MEMALLOC;
+
+		switch (err) {
+		case 0:				/* Success */
+			SetPageUptodate(page);
+			SetPageDirty(page);
+			INC_CACHE_INFO(add_total);
+			return 1;
+		case -EEXIST:
+			/* Raced with "speculative" read_swap_cache_async */
+			INC_CACHE_INFO(exist_race);
+			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;
+
+	BUG_ON(!PageSwapCache(page));
+	BUG_ON(!PageLocked(page));
+	BUG_ON(PageWriteback(page));
+	BUG_ON(PagePrivate(page));
+  
+	entry.val = page->private;
+
+	write_lock_irq(&swapper_space.tree_lock);
+	__delete_from_swap_cache(page);
+	write_unlock_irq(&swapper_space.tree_lock);
+
+	swap_free(entry);
+	page_cache_release(page);
+}
+
+/*
+ * Strange swizzling function only for use by shmem_writepage
+ */
+int move_to_swap_cache(struct page *page, swp_entry_t entry)
+{
+	int err = __add_to_swap_cache(page, entry, GFP_ATOMIC);
+	if (!err) {
+		remove_from_page_cache(page);
+		page_cache_release(page);	/* pagecache ref */
+		if (!swap_duplicate(entry))
+			BUG();
+		SetPageDirty(page);
+		INC_CACHE_INFO(add_total);
+	} else if (err == -EEXIST)
+		INC_CACHE_INFO(exist_race);
+	return err;
+}
+
+/*
+ * Strange swizzling function for shmem_getpage (and shmem_unuse)
+ */
+int move_from_swap_cache(struct page *page, unsigned long index,
+		struct address_space *mapping)
+{
+	int err = add_to_page_cache(page, mapping, index, GFP_ATOMIC);
+	if (!err) {
+		delete_from_swap_cache(page);
+		/* shift page from clean_pages to dirty_pages list */
+		ClearPageDirty(page);
+		set_page_dirty(page);
+	}
+	return err;
+}
+
+/* 
+ * 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) && !TestSetPageLocked(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. Can not do a lock_page,
+ * as we are holding the page_table_lock spinlock.
+ */
+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)
+{
+	int chunk = 16;
+	struct page **pagep = pages;
+
+	lru_add_drain();
+	while (nr) {
+		int todo = min(chunk, nr);
+		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,
+			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_HIGHUSER, vma, addr);
+			if (!new_page)
+				break;		/* Out of memory */
+		}
+
+		/*
+		 * Associate the page with swap entry in the swap cache.
+		 * May fail (-ENOENT) if swap entry has been freed since
+		 * our caller observed it.  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 by try_to_swap_out (or shmem_writepage) re-using
+		 * the just freed swap entry for an existing page.
+		 * May fail (-ENOMEM) if radix-tree node allocation failed.
+		 */
+		err = add_to_swap_cache(new_page, entry);
+		if (!err) {
+			/*
+			 * Initiate read into locked page and return.
+			 */
+			lru_cache_add_active(new_page);
+			swap_readpage(NULL, new_page);
+			return new_page;
+		}
+	} while (err != -ENOENT && err != -ENOMEM);
+
+	if (new_page)
+		page_cache_release(new_page);
+	return found_page;
+}