kernfs_pin_sb() tries to get a refcnt of the superblock, while kernfs_drop_sb() drops this refcnt. This will be used by cgroupfs. Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx> --- fs/kernfs/mount.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ include/linux/kernfs.h | 3 +++ 2 files changed, 48 insertions(+) diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index f25a7c0..4f924e0 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -210,6 +210,51 @@ void kernfs_kill_sb(struct super_block *sb) kernfs_put(root_kn); } +/** + * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root + * @kernfs_root: the kernfs_root in question + * @ns: the namespace tag + * + * Pin the superblock so the superblock won't be destroyed in subsequent + * operations. + */ +bool kernfs_pin_sb(struct kernfs_root *root, const void *ns) +{ + struct kernfs_super_info *info; + int ret = false; + + mutex_lock(&kernfs_mutex); + list_for_each_entry(info, &root->supers, node) { + if (info->ns == ns) { + ret = atomic_inc_not_zero(&info->sb->s_active); + break; + } + } + mutex_unlock(&kernfs_mutex); + return ret; +} + +/** + * kernfs_drop_sb: drop the refcnt that we got by kernfs_pin_sb() + * @root: the kernfs_root in question + * @ns: the namespace tag + * + * This must be paired with kernfs_pin_sb(). It will require sb->u_mount + * if the refcnt reaches zero. + */ +void kernfs_drop_sb(struct kernfs_root *root, const void *ns) +{ + struct kernfs_super_info *info; + + mutex_lock(&kernfs_mutex); + list_for_each_entry(info, &root->supers, node) { + if (info->ns == ns) + break; + } + mutex_unlock(&kernfs_mutex); + deactivate_super(info->sb); +} + void __init kernfs_init(void) { kernfs_node_cache = kmem_cache_create("kernfs_node_cache", diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 589318b..1958017 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -288,6 +288,9 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, const void *ns); void kernfs_kill_sb(struct super_block *sb); +bool kernfs_pin_sb(struct kernfs_root *root, const void *ns); +void kernfs_drop_sb(struct kernfs_root *root, const void *ns); + void kernfs_init(void); #else /* CONFIG_KERNFS */ -- 1.8.0.2 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html