From 3a981f482cc29f7d0aeab509e51ea15519a6e961 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Wed, 20 Jun 2012 12:52:58 -0700 Subject: memcg: fix use_hierarchy css_is_ancestor oops regression If use_hierarchy is set, reclaim testing soon oopses in css_is_ancestor() called from __mem_cgroup_same_or_subtree() called from page_referenced(): when processes are exiting, it's easy for mm_match_cgroup() to pass along a NULL memcg coming from a NULL mm->owner. Check for that in __mem_cgroup_same_or_subtree(). Return true or false? False because we cannot know if it was in the hierarchy, but also false because it's better not to count a reference from an exiting process. Signed-off-by: Hugh Dickins Acked-by: Johannes Weiner Acked-by: Konstantin Khlebnikov Acked-by: KAMEZAWA Hiroyuki Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ac35bccadb7b..f8517cd28feb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1148,7 +1148,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, { if (root_memcg == memcg) return true; - if (!root_memcg->use_hierarchy) + if (!root_memcg->use_hierarchy || !memcg) return false; return css_is_ancestor(&memcg->css, &root_memcg->css); } -- cgit v1.2.3-59-g8ed1b