diff options
| -rw-r--r-- | fs/super.c | 2 | ||||
| -rw-r--r-- | include/linux/cleancache.h | 4 | ||||
| -rw-r--r-- | mm/cleancache.c | 270 |
3 files changed, 94 insertions, 182 deletions
@@ -224,7 +224,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags) s->s_maxbytes = MAX_NON_LFS; s->s_op = &default_op; s->s_time_gran = 1000000000; - s->cleancache_poolid = -1; + s->cleancache_poolid = CLEANCACHE_NO_POOL; s->s_shrink.seeks = DEFAULT_SEEKS; s->s_shrink.scan_objects = super_cache_scan; diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h index b23611f..bda5ec0b4 100644 --- a/include/linux/cleancache.h +++ b/include/linux/cleancache.h @@ -5,6 +5,10 @@ #include <linux/exportfs.h> #include <linux/mm.h> +#define CLEANCACHE_NO_POOL -1 +#define CLEANCACHE_NO_BACKEND -2 +#define CLEANCACHE_NO_BACKEND_SHARED -3 + #define CLEANCACHE_KEY_MAX 6 /* diff --git a/mm/cleancache.c b/mm/cleancache.c index aa10f9a..8fc5081 100644 --- a/mm/cleancache.c +++ b/mm/cleancache.c @@ -19,7 +19,7 @@ #include <linux/cleancache.h> /* - * cleancache_ops is set by cleancache_ops_register to contain the pointers + * cleancache_ops is set by cleancache_register_ops to contain the pointers * to the cleancache "backend" implementation functions. */ static struct cleancache_ops *cleancache_ops __read_mostly; @@ -34,104 +34,78 @@ 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. - */ +static void cleancache_register_ops_sb(struct super_block *sb, void *unused) +{ + switch (sb->cleancache_poolid) { + case CLEANCACHE_NO_BACKEND: + __cleancache_init_fs(sb); + break; + case CLEANCACHE_NO_BACKEND_SHARED: + __cleancache_init_shared_fs(sb); + break; + } +} /* * Register operations for cleancache. Returns 0 on success. */ int cleancache_register_ops(struct cleancache_ops *ops) { - int i; - - mutex_lock(&poolid_mutex); - if (cleancache_ops) { - mutex_unlock(&poolid_mutex); + if (cmpxchg(&cleancache_ops, NULL, ops)) return -EBUSY; - } - 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. + * A cleancache backend can be built as a module and hence loaded after + * a cleancache enabled filesystem has called cleancache_init_fs. To + * handle such a scenario, here we call ->init_fs or ->init_shared_fs + * for each active super block. To differentiate between local and + * shared filesystems, we temporarily initialize sb->cleancache_poolid + * to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED + * respectively in case there is no backend registered at the time + * cleancache_init_fs or cleancache_init_shared_fs is called. + * + * Since filesystems can be mounted concurrently with cleancache + * backend registration, we have to be careful to guarantee that all + * cleancache enabled filesystems that has been mounted by the time + * cleancache_register_ops is called has got and all mounted later will + * get cleancache_poolid. This is assured by the following statements + * tied together: + * + * a) iterate_supers skips only those super blocks that has started + * ->kill_sb + * + * b) if iterate_supers encounters a super block that has not finished + * ->mount yet, it waits until it is finished + * + * c) cleancache_init_fs is called from ->mount and + * cleancache_invalidate_fs is called from ->kill_sb + * + * d) we call iterate_supers after cleancache_ops has been set + * + * From a) it follows that if iterate_supers skips a super block, then + * either the super block is already dead, in which case we do not need + * to bother initializing cleancache for it, or it was mounted after we + * initiated iterate_supers. In the latter case, it must have seen + * cleancache_ops set according to d) and initialized cleancache from + * ->mount by itself according to c). This proves that we call + * ->init_fs at least once for each active super block. + * + * From b) and c) it follows that if iterate_supers encounters a super + * block that has already started ->init_fs, it will wait until ->mount + * and hence ->init_fs has finished, then check cleancache_poolid, see + * that it has already been set and therefore do nothing. This proves + * that we call ->init_fs no more than once for each super block. + * + * Combined together, the last two paragraphs prove the function + * correctness. + * + * Note that various cleancache callbacks may proceed before this + * function is called or even concurrently with it, but since + * CLEANCACHE_NO_BACKEND is negative, they will all result in a noop + * until the corresponding ->init_fs has been actually called and + * cleancache_ops has been set. */ - barrier(); - cleancache_ops = ops; - mutex_unlock(&poolid_mutex); + iterate_supers(cleancache_register_ops_sb, NULL); return 0; } EXPORT_SYMBOL(cleancache_register_ops); @@ -139,42 +113,28 @@ 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; + int pool_id = CLEANCACHE_NO_BACKEND; - 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; - } + if (cleancache_ops) { + pool_id = cleancache_ops->init_fs(PAGE_SIZE); + if (pool_id < 0) + pool_id = CLEANCACHE_NO_POOL; } - mutex_unlock(&poolid_mutex); + sb->cleancache_poolid = pool_id; } EXPORT_SYMBOL(__cleancache_init_fs); /* Called by a cleancache-enabled clustered filesystem at time of mount */ void __cleancache_init_shared_fs(struct super_block *sb) { - int i; + int pool_id = CLEANCACHE_NO_BACKEND_SHARED; - 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] = sb->s_uuid; - if (cleancache_ops) - shared_fs_poolid_map[i] = cleancache_ops->init_shared_fs - (sb->s_uuid, PAGE_SIZE); - else - shared_fs_poolid_map[i] = FS_NO_BACKEND; - break; - } + if (cleancache_ops) { + pool_id = cleancache_ops->init_shared_fs(sb->s_uuid, PAGE_SIZE); + if (pool_id < 0) + pool_id = CLEANCACHE_NO_POOL; } - mutex_unlock(&poolid_mutex); + sb->cleancache_poolid = pool_id; } EXPORT_SYMBOL(__cleancache_init_shared_fs); @@ -204,19 +164,6 @@ 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. @@ -231,7 +178,6 @@ 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) { @@ -240,17 +186,14 @@ int __cleancache_get_page(struct page *page) } VM_BUG_ON_PAGE(!PageLocked(page), page); - fake_pool_id = page->mapping->host->i_sb->cleancache_poolid; - if (fake_pool_id < 0) + pool_id = page->mapping->host->i_sb->cleancache_poolid; + if (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); + ret = cleancache_ops->get_page(pool_id, key, page->index, page); if (ret == 0) cleancache_succ_gets++; else @@ -273,7 +216,6 @@ EXPORT_SYMBOL(__cleancache_get_page); void __cleancache_put_page(struct page *page) { int pool_id; - int fake_pool_id; struct cleancache_filekey key = { .u.key = { 0 } }; if (!cleancache_ops) { @@ -282,12 +224,7 @@ void __cleancache_put_page(struct page *page) } 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); - + pool_id = page->mapping->host->i_sb->cleancache_poolid; if (pool_id >= 0 && cleancache_get_key(page->mapping->host, &key) >= 0) { cleancache_ops->put_page(pool_id, key, page->index, page); @@ -308,18 +245,13 @@ 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; + int 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; - + if (pool_id >= 0) { VM_BUG_ON_PAGE(!PageLocked(page), page); if (cleancache_get_key(mapping->host, &key) >= 0) { cleancache_ops->invalidate_page(pool_id, @@ -341,18 +273,12 @@ EXPORT_SYMBOL(__cleancache_invalidate_page); */ void __cleancache_invalidate_inode(struct address_space *mapping) { - int pool_id; - int fake_pool_id = mapping->host->i_sb->cleancache_poolid; + int 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); } @@ -365,32 +291,18 @@ EXPORT_SYMBOL(__cleancache_invalidate_inode); */ void __cleancache_invalidate_fs(struct super_block *sb) { - int index; - int fake_pool_id = sb->cleancache_poolid; - int old_poolid = fake_pool_id; + int 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); + pool_id = sb->cleancache_poolid; + sb->cleancache_poolid = CLEANCACHE_NO_POOL; + + if (cleancache_ops && pool_id >= 0) + cleancache_ops->invalidate_fs(pool_id); } 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) @@ -402,10 +314,6 @@ 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) |
