[RFC][PATCH 6/7] memcg: don't need to get a reference to the parent

Li Zefan
2013-04-03T09:13:21Z

The cgroup core guarantees it's always safe to access the parent.

Signed-off-by: Li Zefan <lizefan@huawei.com>
---
mm/memcontrol.c | 14 +-------------
1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ad576e8..45129cd 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6124,12 +6124,8 @@ static void mem_cgroup_get(struct mem_cgroup *memcg)

static void __mem_cgroup_put(struct mem_cgroup *memcg, int count)
{
- if (atomic_sub_and_test(count, &memcg->refcnt)) {
- struct mem_cgroup *parent = parent_mem_cgroup(memcg);
+ if (atomic_sub_and_test(count, &memcg->refcnt))
call_rcu(&memcg->rcu_freeing, free_rcu);
- if (parent)
- mem_cgroup_put(parent);
- }
}

static void mem_cgroup_put(struct mem_cgroup *memcg)
@@ -6229,14 +6225,6 @@ mem_cgroup_css_online(struct cgroup *cont)
res_counter_init(&memcg->res, &parent->res);
res_counter_init(&memcg->memsw, &parent->memsw);
res_counter_init(&memcg->kmem, &parent->kmem);
-
- /*
- * We increment refcnt of the parent to ensure that we can
- * safely access it on res_counter_charge/uncharge.
- * This refcnt will be decremented when freeing this
- * mem_cgroup(see mem_cgroup_put).
- */
- mem_cgroup_get(parent);
} else {
res_counter_init(&memcg->res, NULL);
res_counter_init(&memcg->memsw, NULL);
--
1.8.0.2

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