sysfs: make __sysfs_add_one() fail if the parent isn't a directory

Currently the kobject based interface guarantees that a parent
sysfs_dirent is always a directory; however, the planned kernfs
interface will be directly based on sysfs_dirents and the caller may
specify non-directory node as the parent. Add an explicit check in
__sysfs_add_one() so that such attempts fail with -EINVAL.

Signed-off-by: Tejun Heo <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

fs/sysfs/dir.c

···
 		return -EINVAL;
 	}
 
+	if (sysfs_type(parent_sd) != SYSFS_DIR)
+		return -EINVAL;
+
 	sd->s_hash = sysfs_name_hash(sd->s_name, sd->s_ns);
 	sd->s_parent = sysfs_get(parent_sd);