memcg: keep root group unchanged if creation fails

If the request is to create non-root group and we fail to meet it, we
should leave the root unchanged.

Signed-off-by: Hillf Danton <dhillf@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d77dce0b4e62fc786f99b5b02dcd87fa654c010b..31f2d6c224f4ceeb77cae0487490534ec5cbbda6 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5118,9 +5118,9 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
                int cpu;
                enable_swap_cgroup();
                parent = NULL;
-               root_mem_cgroup = memcg;
                if (mem_cgroup_soft_limit_tree_init())
                        goto free_out;
+               root_mem_cgroup = memcg;
                for_each_possible_cpu(cpu) {
                        struct memcg_stock_pcp *stock =
                                                &per_cpu(memcg_stock, cpu);
@@ -5161,7 +5161,6 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
        return &memcg->css;
 free_out:
        __mem_cgroup_free(memcg);
-       root_mem_cgroup = NULL;
        return ERR_PTR(error);
 }