diff options
| -rw-r--r-- | Documentation/vm/cleancache.txt | 4 | ||||
| -rw-r--r-- | drivers/xen/tmem.c | 16 | ||||
| -rw-r--r-- | include/linux/cleancache.h | 3 | ||||
| -rw-r--r-- | mm/cleancache.c | 12 |
4 files changed, 18 insertions, 17 deletions
diff --git a/Documentation/vm/cleancache.txt b/Documentation/vm/cleancache.txt index 01d76282444e..e4b49df7a048 100644 --- a/Documentation/vm/cleancache.txt +++ b/Documentation/vm/cleancache.txt @@ -28,9 +28,7 @@ IMPLEMENTATION OVERVIEW A cleancache "backend" that provides transcendent memory registers itself to the kernel's cleancache "frontend" by calling cleancache_register_ops, passing a pointer to a cleancache_ops structure with funcs set appropriately. -Note that cleancache_register_ops returns the previous settings so that -chaining can be performed if desired. The functions provided must conform to -certain semantics as follows: +The functions provided must conform to certain semantics as follows: Most important, cleancache is "ephemeral". Pages which are copied into cleancache have an indefinite lifetime which is completely unknowable diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c index 8a65423bc696..c4211a31612d 100644 --- a/drivers/xen/tmem.c +++ b/drivers/xen/tmem.c @@ -397,13 +397,15 @@ static int __init xen_tmem_init(void) #ifdef CONFIG_CLEANCACHE BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid)); if (tmem_enabled && cleancache) { - char *s = ""; - struct cleancache_ops *old_ops = - cleancache_register_ops(&tmem_cleancache_ops); - if (old_ops) - s = " (WARNING: cleancache_ops overridden)"; - pr_info("cleancache enabled, RAM provided by Xen Transcendent Memory%s\n", - s); + int err; + + err = cleancache_register_ops(&tmem_cleancache_ops); + if (err) + pr_warn("xen-tmem: failed to enable cleancache: %d\n", + err); + else + pr_info("cleancache enabled, RAM provided by " + "Xen Transcendent Memory\n"); } #endif #ifdef CONFIG_XEN_SELFBALLOONING diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h index 29657d1c83fb..b23611f43cfb 100644 --- a/include/linux/cleancache.h +++ b/include/linux/cleancache.h @@ -33,8 +33,7 @@ struct cleancache_ops { void (*invalidate_fs)(int); }; -extern struct cleancache_ops * - cleancache_register_ops(struct cleancache_ops *ops); +extern int cleancache_register_ops(struct cleancache_ops *ops); extern void __cleancache_init_fs(struct super_block *); extern void __cleancache_init_shared_fs(struct super_block *); extern int __cleancache_get_page(struct page *); diff --git a/mm/cleancache.c b/mm/cleancache.c index 532495f2e4f4..aa10f9a3bc88 100644 --- a/mm/cleancache.c +++ b/mm/cleancache.c @@ -106,15 +106,17 @@ static DEFINE_MUTEX(poolid_mutex); */ /* - * Register operations for cleancache, returning previous thus allowing - * detection of multiple backends and possible nesting. + * Register operations for cleancache. Returns 0 on success. */ -struct cleancache_ops *cleancache_register_ops(struct cleancache_ops *ops) +int cleancache_register_ops(struct cleancache_ops *ops) { - struct cleancache_ops *old = cleancache_ops; int i; mutex_lock(&poolid_mutex); + if (cleancache_ops) { + mutex_unlock(&poolid_mutex); + 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); @@ -130,7 +132,7 @@ struct cleancache_ops *cleancache_register_ops(struct cleancache_ops *ops) barrier(); cleancache_ops = ops; mutex_unlock(&poolid_mutex); - return old; + return 0; } EXPORT_SYMBOL(cleancache_register_ops); |