Messages in this thread | | | Date | Wed, 3 Apr 2013 16:58:48 +0400 | From | Glauber Costa <> | Subject | Re: [RFC][PATCH 1/7] memcg: use css_get in sock_update_memcg() |
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On 04/03/2013 01:11 PM, Li Zefan wrote: > 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 <lizefan@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; > }
What happens if this tryget fails ? Won't we leak a reference here? We will put regardless when the socket is released, and this may go negative. No?
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