memcg: fix oops in mem_cgroup_shrink_usage
Got an oops in mem_cgroup_shrink_usage() when testing loop over tmpfs:
yes, of course, loop0 has no mm: other entry points check but this didn't.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
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 7056c3b..0f1f7a7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -796,6 +796,8 @@
if (mem_cgroup_subsys.disabled)
return 0;
+ if (!mm)
+ return 0;
rcu_read_lock();
mem = mem_cgroup_from_task(rcu_dereference(mm->owner));