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| author | Hugh Dickins <hughd@google.com> | 2012-06-20 12:52:58 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-06-20 14:39:35 -0700 |
| commit | 3a981f482cc29f7d0aeab509e51ea15519a6e961 (patch) | |
| tree | eb7f1f553ffbb99776fdd55216e679d4915f3b18 /mm/memcontrol.c | |
| parent | 61eafb00d55dfbccdfce543c6b60e369ff4f8f18 (diff) | |
| download | lwn-3a981f482cc29f7d0aeab509e51ea15519a6e961.tar.gz lwn-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/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 2 |
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); } |