memcg: don't initialize kmem-cache destroying work for root caches

struct memcg_cache_params has a union.  Different parts of this union
are used for root and non-root caches.  A part with destroying work is
used only for non-root caches.

I fixed the same problem in another place v3.9-rc1-16204-gf101a94, but
didn't notice this one.

This patch fixes the kernel panic:

[   46.848187] BUG: unable to handle kernel paging request at 000000fffffffeb8
[   46.849026] IP: [<ffffffff811a484c>] kmem_cache_destroy_memcg_children+0x6c/0xc0
[   46.849092] PGD 0
[   46.849092] Oops: 0000 [#1] SMP
...

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: <stable@vger.kernel.org>    [3.9.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c290a1cf38624adf8372d67ccf60d9ec01ff1357..c5792a5d87cede8cf2c5474156c1596f51f5ba61 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3195,11 +3195,11 @@ int memcg_register_cache(struct mem_cgroup *memcg, struct kmem_cache *s,
        if (!s->memcg_params)
                return -ENOMEM;
 
-       INIT_WORK(&s->memcg_params->destroy,
-                       kmem_cache_destroy_work_func);
        if (memcg) {
                s->memcg_params->memcg = memcg;
                s->memcg_params->root_cache = root_cache;
+               INIT_WORK(&s->memcg_params->destroy,
+                               kmem_cache_destroy_work_func);
        } else
                s->memcg_params->is_root_cache = true;