1 files changed, 409 insertions, 0 deletions
diff --git a/mm/cleancache.c b/mm/cleancache.c
new file mode 100644
index 00000000000..d0eac435040
--- /dev/null
+++ b/mm/cleancache.c
@@ -0,0 +1,409 @@
+/*
+ * Cleancache frontend
+ *
+ * This code provides the generic "frontend" layer to call a matching
+ * "backend" driver implementation of cleancache.  See
+ * Documentation/vm/cleancache.txt for more information.
+ *
+ * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
+ * Author: Dan Magenheimer
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/exportfs.h>
+#include <linux/mm.h>
+#include <linux/debugfs.h>
+#include <linux/cleancache.h>
+
+/*
+ * cleancache_ops is set by cleancache_ops_register to contain the pointers
+ * to the cleancache "backend" implementation functions.
+ */
+static struct cleancache_ops *cleancache_ops __read_mostly;
+
+/*
+ * Counters available via /sys/kernel/debug/frontswap (if debugfs is
+ * properly configured.  These are for information only so are not protected
+ * against increment races.
+ */
+static u64 cleancache_succ_gets;
+static u64 cleancache_failed_gets;
+static u64 cleancache_puts;
+static u64 cleancache_invalidates;
+
+/*
+ * When no backend is registered all calls to init_fs and init_shared_fs
+ * are registered and fake poolids (FAKE_FS_POOLID_OFFSET or
+ * FAKE_SHARED_FS_POOLID_OFFSET, plus offset in the respective array
+ * [shared_|]fs_poolid_map) are given to the respective super block
+ * (sb->cleancache_poolid) and no tmem_pools are created. When a backend
+ * registers with cleancache the previous calls to init_fs and init_shared_fs
+ * are executed to create tmem_pools and set the respective poolids. While no
+ * backend is registered all "puts", "gets" and "flushes" are ignored or failed.
+ */
+#define MAX_INITIALIZABLE_FS 32
+#define FAKE_FS_POOLID_OFFSET 1000
+#define FAKE_SHARED_FS_POOLID_OFFSET 2000
+
+#define FS_NO_BACKEND (-1)
+#define FS_UNKNOWN (-2)
+static int fs_poolid_map[MAX_INITIALIZABLE_FS];
+static int shared_fs_poolid_map[MAX_INITIALIZABLE_FS];
+static char *uuids[MAX_INITIALIZABLE_FS];
+/*
+ * Mutex for the [shared_|]fs_poolid_map to guard against multiple threads
+ * invoking umount (and ending in __cleancache_invalidate_fs) and also multiple
+ * threads calling mount (and ending up in __cleancache_init_[shared|]fs).
+ */
+static DEFINE_MUTEX(poolid_mutex);
+/*
+ * When set to false (default) all calls to the cleancache functions, except
+ * the __cleancache_invalidate_fs and __cleancache_init_[shared|]fs are guarded
+ * by the if (!cleancache_ops) return. This means multiple threads (from
+ * different filesystems) will be checking cleancache_ops. The usage of a
+ * bool instead of a atomic_t or a bool guarded by a spinlock is OK - we are
+ * OK if the time between the backend's have been initialized (and
+ * cleancache_ops has been set to not NULL) and when the filesystems start
+ * actually calling the backends. The inverse (when unloading) is obviously
+ * not good - but this shim does not do that (yet).
+ */
+
+/*
+ * The backends and filesystems work all asynchronously. This is b/c the
+ * backends can be built as modules.
+ * The usual sequence of events is:
+ *	a) mount /	-> __cleancache_init_fs is called. We set the
+ *		[shared_|]fs_poolid_map and uuids for.
+ *
+ *	b). user does I/Os -> we call the rest of __cleancache_* functions
+ *		which return immediately as cleancache_ops is false.
+ *
+ *	c). modprobe zcache -> cleancache_register_ops. We init the backend
+ *		and set cleancache_ops to true, and for any fs_poolid_map
+ *		(which is set by __cleancache_init_fs) we initialize the poolid.
+ *
+ *	d). user does I/Os -> now that cleancache_ops is true all the
+ *		__cleancache_* functions can call the backend. They all check
+ *		that fs_poolid_map is valid and if so invoke the backend.
+ *
+ *	e). umount /	-> __cleancache_invalidate_fs, the fs_poolid_map is
+ *		reset (which is the second check in the __cleancache_* ops
+ *		to call the backend).
+ *
+ * The sequence of event could also be c), followed by a), and d). and e). The
+ * c) would not happen anymore. There is also the chance of c), and one thread
+ * doing a) + d), and another doing e). For that case we depend on the
+ * filesystem calling __cleancache_invalidate_fs in the proper sequence (so
+ * that it handles all I/Os before it invalidates the fs (which is last part
+ * of unmounting process).
+ *
+ * Note: The acute reader will notice that there is no "rmmod zcache" case.
+ * This is b/c the functionality for that is not yet implemented and when
+ * done, will require some extra locking not yet devised.
+ */
+
+/*
+ * Register operations for cleancache, returning previous thus allowing
+ * detection of multiple backends and possible nesting.
+ */
+struct cleancache_ops *cleancache_register_ops(struct cleancache_ops *ops)
+{
+	struct cleancache_ops *old = cleancache_ops;
+	int i;
+
+	mutex_lock(&poolid_mutex);
+	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+		if (fs_poolid_map[i] == FS_NO_BACKEND)
+			fs_poolid_map[i] = ops->init_fs(PAGE_SIZE);
+		if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
+			shared_fs_poolid_map[i] = ops->init_shared_fs
+					(uuids[i], PAGE_SIZE);
+	}
+	/*
+	 * We MUST set cleancache_ops _after_ we have called the backends
+	 * init_fs or init_shared_fs functions. Otherwise the compiler might
+	 * re-order where cleancache_ops is set in this function.
+	 */
+	barrier();
+	cleancache_ops = ops;
+	mutex_unlock(&poolid_mutex);
+	return old;
+}
+EXPORT_SYMBOL(cleancache_register_ops);
+
+/* Called by a cleancache-enabled filesystem at time of mount */
+void __cleancache_init_fs(struct super_block *sb)
+{
+	int i;
+
+	mutex_lock(&poolid_mutex);
+	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+		if (fs_poolid_map[i] == FS_UNKNOWN) {
+			sb->cleancache_poolid = i + FAKE_FS_POOLID_OFFSET;
+			if (cleancache_ops)
+				fs_poolid_map[i] = cleancache_ops->init_fs(PAGE_SIZE);
+			else
+				fs_poolid_map[i] = FS_NO_BACKEND;
+			break;
+		}
+	}
+	mutex_unlock(&poolid_mutex);
+}
+EXPORT_SYMBOL(__cleancache_init_fs);
+
+/* Called by a cleancache-enabled clustered filesystem at time of mount */
+void __cleancache_init_shared_fs(char *uuid, struct super_block *sb)
+{
+	int i;
+
+	mutex_lock(&poolid_mutex);
+	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+		if (shared_fs_poolid_map[i] == FS_UNKNOWN) {
+			sb->cleancache_poolid = i + FAKE_SHARED_FS_POOLID_OFFSET;
+			uuids[i] = uuid;
+			if (cleancache_ops)
+				shared_fs_poolid_map[i] = cleancache_ops->init_shared_fs
+						(uuid, PAGE_SIZE);
+			else
+				shared_fs_poolid_map[i] = FS_NO_BACKEND;
+			break;
+		}
+	}
+	mutex_unlock(&poolid_mutex);
+}
+EXPORT_SYMBOL(__cleancache_init_shared_fs);
+
+/*
+ * If the filesystem uses exportable filehandles, use the filehandle as
+ * the key, else use the inode number.
+ */
+static int cleancache_get_key(struct inode *inode,
+			      struct cleancache_filekey *key)
+{
+	int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
+	int len = 0, maxlen = CLEANCACHE_KEY_MAX;
+	struct super_block *sb = inode->i_sb;
+
+	key->u.ino = inode->i_ino;
+	if (sb->s_export_op != NULL) {
+		fhfn = sb->s_export_op->encode_fh;
+		if  (fhfn) {
+			len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
+			if (len <= FILEID_ROOT || len == FILEID_INVALID)
+				return -1;
+			if (maxlen > CLEANCACHE_KEY_MAX)
+				return -1;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Returns a pool_id that is associated with a given fake poolid.
+ */
+static int get_poolid_from_fake(int fake_pool_id)
+{
+	if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET)
+		return shared_fs_poolid_map[fake_pool_id -
+			FAKE_SHARED_FS_POOLID_OFFSET];
+	else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET)
+		return fs_poolid_map[fake_pool_id - FAKE_FS_POOLID_OFFSET];
+	return FS_NO_BACKEND;
+}
+
+/*
+ * "Get" data from cleancache associated with the poolid/inode/index
+ * that were specified when the data was put to cleanache and, if
+ * successful, use it to fill the specified page with data and return 0.
+ * The pageframe is unchanged and returns -1 if the get fails.
+ * Page must be locked by caller.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+int __cleancache_get_page(struct page *page)
+{
+	int ret = -1;
+	int pool_id;
+	int fake_pool_id;
+	struct cleancache_filekey key = { .u.key = { 0 } };
+
+	if (!cleancache_ops) {
+		cleancache_failed_gets++;
+		goto out;
+	}
+
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+	fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
+	if (fake_pool_id < 0)
+		goto out;
+	pool_id = get_poolid_from_fake(fake_pool_id);
+
+	if (cleancache_get_key(page->mapping->host, &key) < 0)
+		goto out;
+
+	if (pool_id >= 0)
+		ret = cleancache_ops->get_page(pool_id,
+				key, page->index, page);
+	if (ret == 0)
+		cleancache_succ_gets++;
+	else
+		cleancache_failed_gets++;
+out:
+	return ret;
+}
+EXPORT_SYMBOL(__cleancache_get_page);
+
+/*
+ * "Put" data from a page to cleancache and associate it with the
+ * (previously-obtained per-filesystem) poolid and the page's,
+ * inode and page index.  Page must be locked.  Note that a put_page
+ * always "succeeds", though a subsequent get_page may succeed or fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+void __cleancache_put_page(struct page *page)
+{
+	int pool_id;
+	int fake_pool_id;
+	struct cleancache_filekey key = { .u.key = { 0 } };
+
+	if (!cleancache_ops) {
+		cleancache_puts++;
+		return;
+	}
+
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+	fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
+	if (fake_pool_id < 0)
+		return;
+
+	pool_id = get_poolid_from_fake(fake_pool_id);
+
+	if (pool_id >= 0 &&
+		cleancache_get_key(page->mapping->host, &key) >= 0) {
+		cleancache_ops->put_page(pool_id, key, page->index, page);
+		cleancache_puts++;
+	}
+}
+EXPORT_SYMBOL(__cleancache_put_page);
+
+/*
+ * Invalidate any data from cleancache associated with the poolid and the
+ * page's inode and page index so that a subsequent "get" will fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+void __cleancache_invalidate_page(struct address_space *mapping,
+					struct page *page)
+{
+	/* careful... page->mapping is NULL sometimes when this is called */
+	int pool_id;
+	int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
+	struct cleancache_filekey key = { .u.key = { 0 } };
+
+	if (!cleancache_ops)
+		return;
+
+	if (fake_pool_id >= 0) {
+		pool_id = get_poolid_from_fake(fake_pool_id);
+		if (pool_id < 0)
+			return;
+
+		VM_BUG_ON_PAGE(!PageLocked(page), page);
+		if (cleancache_get_key(mapping->host, &key) >= 0) {
+			cleancache_ops->invalidate_page(pool_id,
+					key, page->index);
+			cleancache_invalidates++;
+		}
+	}
+}
+EXPORT_SYMBOL(__cleancache_invalidate_page);
+
+/*
+ * Invalidate all data from cleancache associated with the poolid and the
+ * mappings's inode so that all subsequent gets to this poolid/inode
+ * will fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+void __cleancache_invalidate_inode(struct address_space *mapping)
+{
+	int pool_id;
+	int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
+	struct cleancache_filekey key = { .u.key = { 0 } };
+
+	if (!cleancache_ops)
+		return;
+
+	if (fake_pool_id < 0)
+		return;
+
+	pool_id = get_poolid_from_fake(fake_pool_id);
+
+	if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
+		cleancache_ops->invalidate_inode(pool_id, key);
+}
+EXPORT_SYMBOL(__cleancache_invalidate_inode);
+
+/*
+ * Called by any cleancache-enabled filesystem at time of unmount;
+ * note that pool_id is surrendered and may be returned by a subsequent
+ * cleancache_init_fs or cleancache_init_shared_fs.
+ */
+void __cleancache_invalidate_fs(struct super_block *sb)
+{
+	int index;
+	int fake_pool_id = sb->cleancache_poolid;
+	int old_poolid = fake_pool_id;
+
+	mutex_lock(&poolid_mutex);
+	if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET) {
+		index = fake_pool_id - FAKE_SHARED_FS_POOLID_OFFSET;
+		old_poolid = shared_fs_poolid_map[index];
+		shared_fs_poolid_map[index] = FS_UNKNOWN;
+		uuids[index] = NULL;
+	} else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET) {
+		index = fake_pool_id - FAKE_FS_POOLID_OFFSET;
+		old_poolid = fs_poolid_map[index];
+		fs_poolid_map[index] = FS_UNKNOWN;
+	}
+	sb->cleancache_poolid = -1;
+	if (cleancache_ops)
+		cleancache_ops->invalidate_fs(old_poolid);
+	mutex_unlock(&poolid_mutex);
+}
+EXPORT_SYMBOL(__cleancache_invalidate_fs);
+
+static int __init init_cleancache(void)
+{
+	int i;
+
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *root = debugfs_create_dir("cleancache", NULL);
+	if (root == NULL)
+		return -ENXIO;
+	debugfs_create_u64("succ_gets", S_IRUGO, root, &cleancache_succ_gets);
+	debugfs_create_u64("failed_gets", S_IRUGO,
+				root, &cleancache_failed_gets);
+	debugfs_create_u64("puts", S_IRUGO, root, &cleancache_puts);
+	debugfs_create_u64("invalidates", S_IRUGO,
+				root, &cleancache_invalidates);
+#endif
+	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+		fs_poolid_map[i] = FS_UNKNOWN;
+		shared_fs_poolid_map[i] = FS_UNKNOWN;
+	}
+	return 0;
+}
+module_init(init_cleancache)