diff options
Diffstat (limited to 'mm/cleancache.c')
| -rw-r--r-- | mm/cleancache.c | 265 |
1 files changed, 227 insertions, 38 deletions
diff --git a/mm/cleancache.c b/mm/cleancache.c index d76ba74be2d..5875f48ce27 100644 --- a/mm/cleancache.c +++ b/mm/cleancache.c @@ -19,20 +19,10 @@ #include <linux/cleancache.h> /* - * This global enablement flag may be read thousands of times per second - * by cleancache_get/put/invalidate even on systems where cleancache_ops - * is not claimed (e.g. cleancache is config'ed on but remains - * disabled), so is preferred to the slower alternative: a function - * call that checks a non-global. - */ -int cleancache_enabled __read_mostly; -EXPORT_SYMBOL(cleancache_enabled); - -/* * 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; +static struct cleancache_ops *cleancache_ops __read_mostly; /* * Counters available via /sys/kernel/debug/frontswap (if debugfs is @@ -45,15 +35,101 @@ 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 (!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 *cleancache_register_ops(struct cleancache_ops *ops) { - struct cleancache_ops old = cleancache_ops; + struct cleancache_ops *old = cleancache_ops; + int i; - cleancache_ops = *ops; - cleancache_enabled = 1; + 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); @@ -61,15 +137,42 @@ 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 (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) { - 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 (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); @@ -99,27 +202,53 @@ static int cleancache_get_key(struct inode *inode, } /* + * 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(!PageLocked(page)); - pool_id = page->mapping->host->i_sb->cleancache_poolid; - if (pool_id < 0) + 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 @@ -134,17 +263,32 @@ 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 (!cleancache_ops) { + 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_ops.put_page)(pool_id, key, page->index, page); + cleancache_get_key(page->mapping->host, &key) >= 0) { + cleancache_ops->put_page(pool_id, key, page->index, page); cleancache_puts++; } } @@ -153,19 +297,31 @@ 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 (!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(!PageLocked(page)); if (cleancache_get_key(mapping->host, &key) >= 0) { - (*cleancache_ops.invalidate_page)(pool_id, - key, page->index); + cleancache_ops->invalidate_page(pool_id, + key, page->index); cleancache_invalidates++; } } @@ -176,34 +332,63 @@ 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 (!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); + 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 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 (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) @@ -215,6 +400,10 @@ 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; + } return 0; } module_init(init_cleancache) |