[PATCH cgroup/for-4.13-fixes] cgroup: fix error return value from cgroup_subtree_control()

[Tejun Heo <tj@kernel.org>]

While refactoring, f7b2814bb9b6 ("cgroup: factor out
cgroup_{apply|finalize}_control() from
cgroup_subtree_control_write()") broke error return value from the
function.  The return value from the last operation is always
overridden to zero.  Fix it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v4.6+
---
 kernel/cgroup/cgroup.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3119,11 +3119,11 @@ static ssize_t cgroup_subtree_control_wr
 	cgrp->subtree_control &= ~disable;
 
 	ret = cgroup_apply_control(cgrp);
-
 	cgroup_finalize_control(cgrp, ret);
+	if (ret)
+		goto out_unlock;
 
 	kernfs_activate(cgrp->kn);
-	ret = 0;
 out_unlock:
 	cgroup_kn_unlock(of->kn);
 	return ret ?: nbytes;