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mm: memcontrol: pull the NULL check from __mem_cgroup_same_or_subtree()

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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 <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.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>
This commit is contained in:
Johannes Weiner 2014-12-10 15:44:30 -08:00 committed by Linus Torvalds
parent c01f46c7c7
commit 413918bb61
2 changed files with 4 additions and 3 deletions
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5
include/linux/memcontrol.h
View file

@ -83,11 +83,12 @@ static inline
bool mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *memcg) bool mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *memcg)
{ {
struct mem_cgroup *task_memcg; struct mem_cgroup *task_memcg;
bool match; bool match = false;
rcu_read_lock(); rcu_read_lock();
task_memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); 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(); rcu_read_unlock();
return match; return match;
} }

2
mm/memcontrol.c
View file

@ -1337,7 +1337,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
{ {
if (root_memcg == memcg) if (root_memcg == memcg)
return true; return true;
if (!root_memcg->use_hierarchy || !memcg) if (!root_memcg->use_hierarchy)
return false; return false;
return cgroup_is_descendant(memcg->css.cgroup, root_memcg->css.cgroup); return cgroup_is_descendant(memcg->css.cgroup, root_memcg->css.cgroup);
} }