From 833f8662af9659508afc3cb80f09138eade378e2 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Tue, 30 Apr 2013 15:26:57 -0700 Subject: cleancache: Make cleancache_init use a pointer for the ops Instead of using a backend_registered to determine whether a backend is enabled. This allows us to remove the backend_register check and just do 'if (cleancache_ops)' [v1: Rebase on top of b97c4b430b0a (ramster->zcache move] Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Bob Liu Cc: Wanpeng Li Cc: Andor Daam Cc: Dan Magenheimer Cc: Florian Schmaus Cc: Minchan Kim Cc: Stefan Hengelein Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/cleancache.c | 62 +++++++++++++++++++++++++++++---------------------------- 1 file changed, 32 insertions(+), 30 deletions(-) (limited to 'mm') diff --git a/mm/cleancache.c b/mm/cleancache.c index 0cecdbba4bcd..b3ae19b72035 100644 --- a/mm/cleancache.c +++ b/mm/cleancache.c @@ -32,7 +32,7 @@ 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 @@ -72,15 +72,14 @@ 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 + * 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 - * backend_registered has been set to true) and when the filesystems start + * 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). */ -static bool backend_registered __read_mostly; /* * The backends and filesystems work all asynchronously. This is b/c the @@ -90,13 +89,13 @@ static bool backend_registered __read_mostly; * [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. + * which return immediately as cleancache_ops is false. * * c). modprobe zcache -> cleancache_register_ops. We init the backend - * and set backend_registered to true, and for any fs_poolid_map + * 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 backend_registered is true all the + * 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. * @@ -120,23 +119,26 @@ static bool backend_registered __read_mostly; * 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; - - 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); + fs_poolid_map[i] = ops->init_fs(PAGE_SIZE); if (shared_fs_poolid_map[i] == FS_NO_BACKEND) - shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs) + shared_fs_poolid_map[i] = ops->init_shared_fs (uuids[i], PAGE_SIZE); } -out: + /* + * 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; } @@ -151,8 +153,8 @@ void __cleancache_init_fs(struct super_block *sb) 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); + if (cleancache_ops) + fs_poolid_map[i] = cleancache_ops->init_fs(PAGE_SIZE); else fs_poolid_map[i] = FS_NO_BACKEND; break; @@ -172,8 +174,8 @@ void __cleancache_init_shared_fs(char *uuid, struct super_block *sb) 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) + 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; @@ -240,7 +242,7 @@ int __cleancache_get_page(struct page *page) int fake_pool_id; struct cleancache_filekey key = { .u.key = { 0 } }; - if (!backend_registered) { + if (!cleancache_ops) { cleancache_failed_gets++; goto out; } @@ -255,7 +257,7 @@ int __cleancache_get_page(struct page *page) goto out; if (pool_id >= 0) - ret = (*cleancache_ops.get_page)(pool_id, + ret = cleancache_ops->get_page(pool_id, key, page->index, page); if (ret == 0) cleancache_succ_gets++; @@ -282,7 +284,7 @@ void __cleancache_put_page(struct page *page) int fake_pool_id; struct cleancache_filekey key = { .u.key = { 0 } }; - if (!backend_registered) { + if (!cleancache_ops) { cleancache_puts++; return; } @@ -296,7 +298,7 @@ void __cleancache_put_page(struct page *page) if (pool_id >= 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); cleancache_puts++; } } @@ -318,7 +320,7 @@ void __cleancache_invalidate_page(struct address_space *mapping, int fake_pool_id = mapping->host->i_sb->cleancache_poolid; struct cleancache_filekey key = { .u.key = { 0 } }; - if (!backend_registered) + if (!cleancache_ops) return; if (fake_pool_id >= 0) { @@ -328,7 +330,7 @@ void __cleancache_invalidate_page(struct address_space *mapping, VM_BUG_ON(!PageLocked(page)); if (cleancache_get_key(mapping->host, &key) >= 0) { - (*cleancache_ops.invalidate_page)(pool_id, + cleancache_ops->invalidate_page(pool_id, key, page->index); cleancache_invalidates++; } @@ -351,7 +353,7 @@ void __cleancache_invalidate_inode(struct address_space *mapping) int fake_pool_id = mapping->host->i_sb->cleancache_poolid; struct cleancache_filekey key = { .u.key = { 0 } }; - if (!backend_registered) + if (!cleancache_ops) return; if (fake_pool_id < 0) @@ -360,7 +362,7 @@ void __cleancache_invalidate_inode(struct address_space *mapping) 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); @@ -387,8 +389,8 @@ void __cleancache_invalidate_fs(struct super_block *sb) fs_poolid_map[index] = FS_UNKNOWN; } sb->cleancache_poolid = -1; - if (backend_registered) - (*cleancache_ops.invalidate_fs)(old_poolid); + if (cleancache_ops) + cleancache_ops->invalidate_fs(old_poolid); mutex_unlock(&poolid_mutex); } EXPORT_SYMBOL(__cleancache_invalidate_fs); -- cgit