From 49a9ab815acb8379a2f5fd43abe40038821e8f87 Mon Sep 17 00:00:00 2001 From: Dan Magenheimer Date: Tue, 30 Apr 2013 15:26:56 -0700 Subject: [PATCH] mm: cleancache: lazy initialization to allow tmem backends to build/run as modules With the goal of allowing tmem backends (zcache, ramster, Xen tmem) to be built/loaded as modules rather than built-in and enabled by a boot parameter, this patch provides "lazy initialization", allowing backends to register to cleancache even after filesystems were mounted. Calls to init_fs and init_shared_fs are remembered as fake poolids but no real tmem_pools created. On backend registration the fake poolids are mapped to real poolids and respective tmem_pools. Signed-off-by: Stefan Hengelein Signed-off-by: Florian Schmaus Signed-off-by: Andor Daam Signed-off-by: Dan Magenheimer [v1: Minor fixes: used #define for some values and bools] [v2: Removed CLEANCACHE_HAS_LAZY_INIT] [v3: Added more comments, added a lock for [shared_|]fs_poolid_map] Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Bob Liu Cc: Wanpeng Li Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/cleancache.c | 242 +++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 220 insertions(+), 22 deletions(-) diff --git a/mm/cleancache.c b/mm/cleancache.c index d76ba74be2d0..0cecdbba4bcd 100644 --- a/mm/cleancache.c +++ b/mm/cleancache.c @@ -45,15 +45,99 @@ static u64 cleancache_puts; static u64 cleancache_invalidates; /* - * register operations for cleancache, returning previous thus allowing - * detection of multiple backends and possible nesting + * 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 (!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 old = cleancache_ops; + int i; + mutex_lock(&poolid_mutex); 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; } EXPORT_SYMBOL(cleancache_register_ops); @@ -61,15 +145,42 @@ EXPORT_SYMBOL(cleancache_register_ops); /* Called by a cleancache-enabled filesystem at time of mount */ 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); /* Called by a cleancache-enabled clustered filesystem at time of mount */ void __cleancache_init_shared_fs(char *uuid, struct super_block *sb) { - sb->cleancache_poolid = - (*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE); + 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 (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); @@ -98,28 +209,54 @@ static int cleancache_get_key(struct inode *inode, 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 } }; - VM_BUG_ON(!PageLocked(page)); - pool_id = page->mapping->host->i_sb->cleancache_poolid; - if (pool_id < 0) + if (!backend_registered) { + cleancache_failed_gets++; goto out; + } + + VM_BUG_ON(!PageLocked(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; - 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) cleancache_succ_gets++; else @@ -134,16 +271,31 @@ EXPORT_SYMBOL(__cleancache_get_page); * (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 (!backend_registered) { + cleancache_puts++; + return; + } + 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 && - 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_puts++; } @@ -153,19 +305,31 @@ 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 = 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 } }; - 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)); if (cleancache_get_key(mapping->host, &key) >= 0) { (*cleancache_ops.invalidate_page)(pool_id, - key, page->index); + key, page->index); cleancache_invalidates++; } } @@ -176,12 +340,25 @@ 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 = 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 } }; + 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) (*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; - * note that pool_id is surrendered and may be reutrned by a subsequent - * cleancache_init_fs or cleancache_init_shared_fs + * 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) { - if (sb->cleancache_poolid >= 0) { - int old_poolid = sb->cleancache_poolid; - sb->cleancache_poolid = -1; - (*cleancache_ops.invalidate_fs)(old_poolid); + 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 (backend_registered) + (*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) @@ -215,6 +408,11 @@ static int __init init_cleancache(void) 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; + } + cleancache_enabled = 1; return 0; } module_init(init_cleancache)