cgroup: fix default notify_on_release setting

The documentation says the default value of notify_on_release of a child
cgroup is inherited from its parent, which is reasonable, but the
implementation just sets the flag disabled.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/cgroup.c

@@ -2232,7 +2232,6 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 
 	mutex_lock(&cgroup_mutex);
 
-	cgrp->flags = 0;
 	INIT_LIST_HEAD(&cgrp->sibling);
 	INIT_LIST_HEAD(&cgrp->children);
 	INIT_LIST_HEAD(&cgrp->css_sets);
@@ -2242,6 +2241,9 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	cgrp->root = parent->root;
 	cgrp->top_cgroup = parent->top_cgroup;
 
+	if (notify_on_release(parent))
+		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
+
 	for_each_subsys(root, ss) {
 		struct cgroup_subsys_state *css = ss->create(ss, cgrp);
 		if (IS_ERR(css)) {