cgroup: allow cgroup creation and suppress automatic css creation in the unified...

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>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 83a8fff43d68ebb0e2c7c676d707cfecc6ae24c1..2a4f88db3205ad114a3eabccd05033285d7848b7 100644 (file)
--- 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);