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Message-Id: <20201028035013.99711-1-songmuchun@bytedance.com>
Date: Wed, 28 Oct 2020 11:50:10 +0800
From: Muchun Song <songmuchun@...edance.com>
To: hannes@...xchg.org, mhocko@...nel.org, vdavydov.dev@...il.com,
akpm@...ux-foundation.org, shakeelb@...gle.com, guro@...com,
iamjoonsoo.kim@....com, laoar.shao@...il.com, chris@...isdown.name,
christian.brauner@...ntu.com, peterz@...radead.org,
mingo@...nel.org, keescook@...omium.org, tglx@...utronix.de,
esyr@...hat.com, surenb@...gle.com, areber@...hat.com,
elver@...gle.com
Cc: linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
linux-mm@...ck.org, Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v2] mm: memcg/slab: Fix return child memcg objcg for root memcg
Consider the following memcg hierarchy.
root
/ \
A B
If we get the objcg of memcg A failed, the get_obj_cgroup_from_current
can return the wrong objcg for the root memcg.
Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
changelog in v2:
1. Do not use a comparison with the root_mem_cgroup
mm/memcontrol.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1337775b04f3..8c8b4c3ed5a0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2961,6 +2961,7 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
objcg = rcu_dereference(memcg->objcg);
if (objcg && obj_cgroup_tryget(objcg))
break;
+ objcg = NULL;
}
rcu_read_unlock();
--
2.20.1
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