Potentially, here can be last css refcnt, so we should
have stable memory to access parent pointer.

Signed-off-by: Kirill Tkhai <[email protected]>
---
 mm/memcontrol.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 797cb8e6df6d..d83908598ad1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3518,6 +3518,7 @@ void memcg_uncharge_kmem(struct mem_cgroup *memcg,
        if (kmem)
                return;
 
+       rcu_read_lock();
        /*
         * Releases a reference taken in memcg_deactivate_kmem in case
         * this last uncharge is racing with the offlining code or it is
@@ -3541,6 +3542,7 @@ void memcg_uncharge_kmem(struct mem_cgroup *memcg,
                else
                        break;
        }
+       rcu_read_unlock();
 }
 
 int __memcg_charge_slab(struct kmem_cache *s, gfp_t gfp, unsigned int nr_pages)


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