diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index f8fe6bf2036d..17b8418358ed 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -303,6 +303,41 @@ static const struct inode_operations ovl_symlink_inode_operations = { .update_time = ovl_update_time, }; +/* + * It is possible to stack overlayfs instance on top of another + * overlayfs instance as lower layer. We need to annonate the + * stackable i_mutex locks according to stack level of the super + * block instance. An overlayfs instance can never be in stack + * depth 0 (there is always a real fs below it). An overlayfs + * inode lock will use the lockdep annotaion ovl_i_mutex_key[depth]. + * + * For example, here is a snip from /proc/lockdep_chains after + * dir_iterate of nested overlayfs: + * + * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2) + * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1) + * [...] &type->i_mutex_dir_key (stack_depth=0) + */ +#define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH + +static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode) +{ +#ifdef CONFIG_LOCKDEP + static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING]; + static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING]; + + int depth = inode->i_sb->s_stack_depth - 1; + + if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING)) + depth = 0; + + if (S_ISDIR(inode->i_mode)) + lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]); + else + lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]); +#endif +} + static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev) { inode->i_ino = get_next_ino(); @@ -312,6 +347,8 @@ static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev) inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE; #endif + ovl_lockdep_annotate_inode_mutex_key(inode); + switch (mode & S_IFMT) { case S_IFREG: inode->i_op = &ovl_file_inode_operations;