[RFC][PATCH 1/7] memcg: use css_get in sock_update_memcg()

[Li Zefan]

Use css_get/css_put instead of mem_cgroup_get/put.

Note, if at the same time someone is moving @current to a different
cgroup and removing the old cgroup, css_tryget() may return false,
and sock->sk_cgrp won't be initialized.

Signed-off-by: Li Zefan <lize...@huawei.com>
---
 mm/memcontrol.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 23d0f6e..43ca91d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -536,15 +536,15 @@ void sock_update_memcg(struct sock *sk)
                 */
                if (sk->sk_cgrp) {
                        BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg));
-                       mem_cgroup_get(sk->sk_cgrp->memcg);
+                       css_get(&sk->sk_cgrp->memcg->css);
                        return;
                }
 
                rcu_read_lock();
                memcg = mem_cgroup_from_task(current);
                cg_proto = sk->sk_prot->proto_cgroup(memcg);
-               if (!mem_cgroup_is_root(memcg) && memcg_proto_active(cg_proto)) 
{
-                       mem_cgroup_get(memcg);
+               if (!mem_cgroup_is_root(memcg) &&
+                   memcg_proto_active(cg_proto) && css_tryget(&memcg->css)) {
                        sk->sk_cgrp = cg_proto;
                }
                rcu_read_unlock();
@@ -558,7 +558,7 @@ void sock_release_memcg(struct sock *sk)
                struct mem_cgroup *memcg;
                WARN_ON(!sk->sk_cgrp->memcg);
                memcg = sk->sk_cgrp->memcg;
-               mem_cgroup_put(memcg);
+               css_put(&sk->sk_cgrp->memcg->css);
        }
 }
 
-- 
1.8.0.2
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