+/**
+ * check_acl - perform ACL permission checking
+ * @mnt_userns: user namespace of the mount the inode was found from
+ * @inode: inode to check permissions on
+ * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
+ *
+ * This function performs the ACL permission checking. Since this function
+ * retrieve POSIX acls it needs to know whether it is called from a blocking or
+ * non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
+ *
+ * If the inode has been found through an idmapped mount the user namespace of
+ * the vfsmount must be passed through @mnt_userns. This function will then take
+ * care to map the inode according to @mnt_userns before checking permissions.
+ * On non-idmapped mounts or if permission checking is to be performed on the
+ * raw inode simply passs init_user_ns.
+ */
+static int check_acl(struct user_namespace *mnt_userns,
+ struct inode *inode, int mask)