mm: cleancache: lazy initialization to allow tmem backends to build/run as modules (49a9ab81) · Commits · e / devices / android_kernel_teracube_2e

mm/cleancache.c

+219 −21

Original line number	Original line	Diff line number	Diff line
	@@ -45,15 +45,99 @@ static u64 cleancache_puts;
	static u64 cleancache_invalidates;		static u64 cleancache_invalidates;

	/*		/*
	* register operations for cleancache, returning previous thus allowing		* When no backend is registered all calls to init_fs and init_shared_fs
	* detection of multiple backends and possible nesting		* 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 (!backend_registered) return. This means multiple threads (from
			* different filesystems) will be checking backend_registered. 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
			* backend_registered has been set to true) 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).
			*/
			static bool backend_registered __read_mostly;

			/*
			* 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 backend_registered is false.
			*
			* c). modprobe zcache -> cleancache_register_ops. We init the backend
			* and set backend_registered 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 backend_registered 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 cleancache_register_ops(struct cleancache_ops *ops)
	{		{
	struct cleancache_ops old = cleancache_ops;		struct cleancache_ops old = cleancache_ops;
			int i;

			mutex_lock(&poolid_mutex);
	cleancache_ops = *ops;		cleancache_ops = *ops;
	cleancache_enabled = 1;
			backend_registered = true;
			for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
			if (fs_poolid_map[i] == FS_NO_BACKEND)
			fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
			if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
			shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
			(uuids[i], PAGE_SIZE);
			}
			out:
			mutex_unlock(&poolid_mutex);
	return old;		return old;
	}		}
	EXPORT_SYMBOL(cleancache_register_ops);		EXPORT_SYMBOL(cleancache_register_ops);
	@@ -61,15 +145,42 @@ EXPORT_SYMBOL(cleancache_register_ops);
	/* Called by a cleancache-enabled filesystem at time of mount */		/* Called by a cleancache-enabled filesystem at time of mount */
	void __cleancache_init_fs(struct super_block *sb)		void __cleancache_init_fs(struct super_block *sb)
	{		{
	sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);		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 (backend_registered)
			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);		EXPORT_SYMBOL(__cleancache_init_fs);

	/* Called by a cleancache-enabled clustered filesystem at time of mount */		/* Called by a cleancache-enabled clustered filesystem at time of mount */
	void __cleancache_init_shared_fs(char uuid, struct super_block sb)		void __cleancache_init_shared_fs(char uuid, struct super_block sb)
	{		{
	sb->cleancache_poolid =		int i;
	(*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
			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 (backend_registered)
			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);		EXPORT_SYMBOL(__cleancache_init_shared_fs);

	@@ -98,28 +209,54 @@ static int cleancache_get_key(struct inode *inode,
	return 0;		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		* "Get" data from cleancache associated with the poolid/inode/index
	* that were specified when the data was put to cleanache and, if		* 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.		* successful, use it to fill the specified page with data and return 0.
	* The pageframe is unchanged and returns -1 if the get fails.		* The pageframe is unchanged and returns -1 if the get fails.
	* Page must be locked by caller.		* 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 __cleancache_get_page(struct page *page)
	{		{
	int ret = -1;		int ret = -1;
	int pool_id;		int pool_id;
			int fake_pool_id;
	struct cleancache_filekey key = { .u.key = { 0 } };		struct cleancache_filekey key = { .u.key = { 0 } };

			if (!backend_registered) {
			cleancache_failed_gets++;
			goto out;
			}

	VM_BUG_ON(!PageLocked(page));		VM_BUG_ON(!PageLocked(page));
	pool_id = page->mapping->host->i_sb->cleancache_poolid;		fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
	if (pool_id < 0)		if (fake_pool_id < 0)
	goto out;		goto out;
			pool_id = get_poolid_from_fake(fake_pool_id);

	if (cleancache_get_key(page->mapping->host, &key) < 0)		if (cleancache_get_key(page->mapping->host, &key) < 0)
	goto out;		goto out;

	ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page);		if (pool_id >= 0)
			ret = (*cleancache_ops.get_page)(pool_id,
			key, page->index, page);
	if (ret == 0)		if (ret == 0)
	cleancache_succ_gets++;		cleancache_succ_gets++;
	else		else
	@@ -134,14 +271,29 @@ EXPORT_SYMBOL(__cleancache_get_page);
	* (previously-obtained per-filesystem) poolid and the page's,		* (previously-obtained per-filesystem) poolid and the page's,
	* inode and page index. Page must be locked. Note that a put_page		* inode and page index. Page must be locked. Note that a put_page
	* always "succeeds", though a subsequent get_page may succeed or fail.		* 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)		void __cleancache_put_page(struct page *page)
	{		{
	int pool_id;		int pool_id;
			int fake_pool_id;
	struct cleancache_filekey key = { .u.key = { 0 } };		struct cleancache_filekey key = { .u.key = { 0 } };

			if (!backend_registered) {
			cleancache_puts++;
			return;
			}

	VM_BUG_ON(!PageLocked(page));		VM_BUG_ON(!PageLocked(page));
	pool_id = page->mapping->host->i_sb->cleancache_poolid;		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 &&		if (pool_id >= 0 &&
	cleancache_get_key(page->mapping->host, &key) >= 0) {		cleancache_get_key(page->mapping->host, &key) >= 0) {
	(*cleancache_ops.put_page)(pool_id, key, page->index, page);		(*cleancache_ops.put_page)(pool_id, key, page->index, page);
	@@ -153,15 +305,27 @@ EXPORT_SYMBOL(__cleancache_put_page);
	/*		/*
	* Invalidate any data from cleancache associated with the poolid and the		* Invalidate any data from cleancache associated with the poolid and the
	* page's inode and page index so that a subsequent "get" will fail.		* 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,		void __cleancache_invalidate_page(struct address_space *mapping,
	struct page *page)		struct page *page)
	{		{
	/* careful... page->mapping is NULL sometimes when this is called */		/* careful... page->mapping is NULL sometimes when this is called */
	int pool_id = mapping->host->i_sb->cleancache_poolid;		int pool_id;
			int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
	struct cleancache_filekey key = { .u.key = { 0 } };		struct cleancache_filekey key = { .u.key = { 0 } };

	if (pool_id >= 0) {		if (!backend_registered)
			return;

			if (fake_pool_id >= 0) {
			pool_id = get_poolid_from_fake(fake_pool_id);
			if (pool_id < 0)
			return;

	VM_BUG_ON(!PageLocked(page));		VM_BUG_ON(!PageLocked(page));
	if (cleancache_get_key(mapping->host, &key) >= 0) {		if (cleancache_get_key(mapping->host, &key) >= 0) {
	(*cleancache_ops.invalidate_page)(pool_id,		(*cleancache_ops.invalidate_page)(pool_id,
	@@ -176,12 +340,25 @@ EXPORT_SYMBOL(__cleancache_invalidate_page);
	* Invalidate all data from cleancache associated with the poolid and the		* Invalidate all data from cleancache associated with the poolid and the
	* mappings's inode so that all subsequent gets to this poolid/inode		* mappings's inode so that all subsequent gets to this poolid/inode
	* will fail.		* 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)		void __cleancache_invalidate_inode(struct address_space *mapping)
	{		{
	int pool_id = mapping->host->i_sb->cleancache_poolid;		int pool_id;
			int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
	struct cleancache_filekey key = { .u.key = { 0 } };		struct cleancache_filekey key = { .u.key = { 0 } };

			if (!backend_registered)
			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)		if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
	(*cleancache_ops.invalidate_inode)(pool_id, key);		(*cleancache_ops.invalidate_inode)(pool_id, key);
	}		}
	@@ -189,21 +366,37 @@ EXPORT_SYMBOL(__cleancache_invalidate_inode);

	/*		/*
	* Called by any cleancache-enabled filesystem at time of unmount;		* Called by any cleancache-enabled filesystem at time of unmount;
	* note that pool_id is surrendered and may be reutrned by a subsequent		* note that pool_id is surrendered and may be returned by a subsequent
	* cleancache_init_fs or cleancache_init_shared_fs		* cleancache_init_fs or cleancache_init_shared_fs.
	*/		*/
	void __cleancache_invalidate_fs(struct super_block *sb)		void __cleancache_invalidate_fs(struct super_block *sb)
	{		{
	if (sb->cleancache_poolid >= 0) {		int index;
	int old_poolid = sb->cleancache_poolid;		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;		sb->cleancache_poolid = -1;
			if (backend_registered)
	(*cleancache_ops.invalidate_fs)(old_poolid);		(*cleancache_ops.invalidate_fs)(old_poolid);
	}		mutex_unlock(&poolid_mutex);
	}		}
	EXPORT_SYMBOL(__cleancache_invalidate_fs);		EXPORT_SYMBOL(__cleancache_invalidate_fs);

	static int __init init_cleancache(void)		static int __init init_cleancache(void)
	{		{
			int i;

	#ifdef CONFIG_DEBUG_FS		#ifdef CONFIG_DEBUG_FS
	struct dentry *root = debugfs_create_dir("cleancache", NULL);		struct dentry *root = debugfs_create_dir("cleancache", NULL);
	if (root == NULL)		if (root == NULL)
	@@ -215,6 +408,11 @@ static int __init init_cleancache(void)
	debugfs_create_u64("invalidates", S_IRUGO,		debugfs_create_u64("invalidates", S_IRUGO,
	root, &cleancache_invalidates);		root, &cleancache_invalidates);
	#endif		#endif
			for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
			fs_poolid_map[i] = FS_UNKNOWN;
			shared_fs_poolid_map[i] = FS_UNKNOWN;
			}
			cleancache_enabled = 1;
	return 0;		return 0;
	}		}
	module_init(init_cleancache)		module_init(init_cleancache)