Merge branch 'for-3.7-hierarchy' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup hierarchy update from Tejun Heo:
 "Currently, different cgroup subsystems handle nested cgroups
  completely differently.  There's no consistency among subsystems and
  the behaviors often are outright broken.

  People at least seem to agree that the broken hierarhcy behaviors need
  to be weeded out if any progress is gonna be made on this front and
  that the fallouts from deprecating the broken behaviors should be
  acceptable especially given that the current behaviors don't make much
  sense when nested.

  This patch makes cgroup emit warning messages if cgroups for
  subsystems with broken hierarchy behavior are nested to prepare for
  fixing them in the future.  This was put in a separate branch because
  more related changes were expected (didn't make it this round) and the
  memory cgroup wanted to pull in this and make changes on top."

* 'for-3.7-hierarchy' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them

1 files changed, 11 insertions, 1 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 485cc1487ea2..13774b3b39aa 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4076,8 +4076,9 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
                 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
 
         for_each_subsys(root, ss) {
-                struct cgroup_subsys_state *css = ss->create(cgrp);
+                struct cgroup_subsys_state *css;
 
+                css = ss->create(cgrp);
                 if (IS_ERR(css)) {
                         err = PTR_ERR(css);
                         goto err_destroy;
@@ -4091,6 +4092,15 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
                 /* At error, ->destroy() callback has to free assigned ID. */
                 if (clone_children(parent) && ss->post_clone)
                         ss->post_clone(cgrp);
+
+                if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
+                    parent->parent) {
+                        pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
+                                   current->comm, current->pid, ss->name);
+                        if (!strcmp(ss->name, "memory"))
+                                pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
+                        ss->warned_broken_hierarchy = true;
+                }
         }
 
         list_add(&cgrp->sibling, &cgrp->parent->children);