From bd53d617b34c781dac8e22dbc75e8f182d918ecf Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 23 Apr 2014 11:13:16 -0400
Subject: [PATCH] cgroup: allow cgroup creation and suppress automatic css
 creation in the unified hierarchy

Now that effective css handling has been added and iterators updated
accordingly, it's safe to allow cgroup creation in the default
hierarchy.  Unblock cgroup creation in the default hierarchy.

As the default hierarchy will implement explicit enabling and
disabling of controllers on each cgroup, suppress automatic css
enabling on cgroup creation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
---
 kernel/cgroup.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 83a8fff43d68..2a4f88db3205 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1115,8 +1115,10 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
 		src_root->subsys_mask &= ~(1 << ssid);
 		src_root->cgrp.child_subsys_mask &= ~(1 << ssid);
 
+		/* default hierarchy doesn't enable controllers by default */
 		dst_root->subsys_mask |= 1 << ssid;
-		dst_root->cgrp.child_subsys_mask |= 1 << ssid;
+		if (dst_root != &cgrp_dfl_root)
+			dst_root->cgrp.child_subsys_mask |= 1 << ssid;
 
 		if (ss->bind)
 			ss->bind(css);
@@ -3786,13 +3788,6 @@ static long cgroup_create(struct cgroup *parent, const char *name,
 	struct cgroup_subsys *ss;
 	struct kernfs_node *kn;
 
-	/*
-	 * XXX: The default hierarchy isn't fully implemented yet.  Block
-	 * !root cgroup creation on it for now.
-	 */
-	if (root == &cgrp_dfl_root)
-		return -EINVAL;
-
 	/* allocate the cgroup and its ID, 0 is reserved for the root */
 	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
 	if (!cgrp)
@@ -3878,7 +3873,12 @@ static long cgroup_create(struct cgroup *parent, const char *name,
 		}
 	}
 
-	cgrp->child_subsys_mask = parent->child_subsys_mask;
+	/*
+	 * On the default hierarchy, a child doesn't automatically inherit
+	 * child_subsys_mask from the parent.  Each is configured manually.
+	 */
+	if (!cgroup_on_dfl(cgrp))
+		cgrp->child_subsys_mask = parent->child_subsys_mask;
 
 	kernfs_activate(kn);
 
-- 
2.20.1