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Commit 413918bb authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
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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: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c01f46c7

include/linux/memcontrol.h

+3 −2
Original line number Diff line number Diff line
@@ -83,10 +83,11 @@ 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));

	if (task_memcg)

		match = __mem_cgroup_same_or_subtree(memcg, task_memcg);

	rcu_read_unlock();

	return match;

mm/memcontrol.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}