blkio: Fix return code for mkdir calls

If the cgroup hierarchy for blkio control groups is deeper than two
levels, kernel should not allow the creation of further levels. mkdir
system call does not except EINVAL as a return value. This patch
replaces EINVAL with more appropriate EPERM

Signed-off-by: Ciju Rajan K <ciju@linux.vnet.ibm.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

block/blk-cgroup.c

@@ -966,7 +966,7 @@ blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 
 	/* Currently we do not support hierarchy deeper than two level (0,1) */
 	if (parent != cgroup->top_cgroup)
-		return ERR_PTR(-EINVAL);
+		return ERR_PTR(-EPERM);
 
 	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 	if (!blkcg)