[v2] mm: Add RCU read brackets into memcg_uncharge_kmem()

Submitted by Kirill Tkhai on May 7, 2020, 9:25 a.m.

Details

Message ID 158884352254.24727.8270147075576946590.stgit@localhost.localdomain
State New
Series "mm: Move memcg_uncharge_kmem() to bottom of __memcg_uncharge_slab()"
Headers show

Commit Message

Kirill Tkhai May 7, 2020, 9:25 a.m.
Potentially, here can be last css refcnt, so we should
have stable memory to access parent pointer.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 mm/memcontrol.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

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diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 797cb8e6df6d..2fcfe7abaafc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3508,6 +3508,7 @@  void memcg_uncharge_kmem(struct mem_cgroup *memcg,
 {
 	u64 kmem;
 
+	rcu_read_lock();
 	kmem = page_counter_uncharge(&memcg->kmem, nr_pages);
 
 	page_counter_uncharge(&memcg->memory, nr_pages);
@@ -3516,7 +3517,7 @@  void memcg_uncharge_kmem(struct mem_cgroup *memcg,
 
 	/* Not down to 0 */
 	if (kmem)
-		return;
+		goto unlock;
 
 	/*
 	 * Releases a reference taken in memcg_deactivate_kmem in case
@@ -3541,6 +3542,8 @@  void memcg_uncharge_kmem(struct mem_cgroup *memcg,
 		else
 			break;
 	}
+unlock:
+	rcu_read_unlock();
 }
 
 int __memcg_charge_slab(struct kmem_cache *s, gfp_t gfp, unsigned int nr_pages)