From 413918bb61b4fa027baa3e79546c47f15e4b9ea8 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Wed, 10 Dec 2014 15:44:30 -0800 Subject: [PATCH] mm: memcontrol: pull the NULL check from __mem_cgroup_same_or_subtree() The NULL in mm_match_cgroup() comes from a possibly exiting mm->owner. It makes a lot more sense to check where it's looked up, rather than check for it in __mem_cgroup_same_or_subtree() where it's unexpected. No other callsite passes NULL to __mem_cgroup_same_or_subtree(). Signed-off-by: Johannes Weiner Reviewed-by: Vladimir Davydov Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 5 +++-- mm/memcontrol.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index ea007615e8f9..e32ab948f589 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -83,11 +83,12 @@ static inline bool mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *memcg) { struct mem_cgroup *task_memcg; - bool match; + bool match = false; rcu_read_lock(); task_memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); - match = __mem_cgroup_same_or_subtree(memcg, task_memcg); + if (task_memcg) + match = __mem_cgroup_same_or_subtree(memcg, task_memcg); rcu_read_unlock(); return match; } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 367cc57df362..e5dcebd71dfb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1337,7 +1337,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, { if (root_memcg == memcg) return true; - if (!root_memcg->use_hierarchy || !memcg) + if (!root_memcg->use_hierarchy) return false; return cgroup_is_descendant(memcg->css.cgroup, root_memcg->css.cgroup); }