[Devel] [PATCH rh7] mm: Add RCU read brackets into memcg_uncharge_kmem()

[Kirill Tkhai]

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

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 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)