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authorHugh Dickins <hughd@google.com>2012-06-20 12:52:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-06-20 14:39:35 -0700
commit3a981f482cc29f7d0aeab509e51ea15519a6e961 (patch)
treeeb7f1f553ffbb99776fdd55216e679d4915f3b18 /mm
parentmm, oom: fix and cleanup oom score calculations (diff)
downloadlinux-dev-3a981f482cc29f7d0aeab509e51ea15519a6e961.tar.xz
linux-dev-3a981f482cc29f7d0aeab509e51ea15519a6e961.zip
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 <hughd@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c2
1 files changed, 1 insertions, 1 deletions
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);
}