Messages in this thread | | | Date | Fri, 2 Feb 2018 18:06:32 +0000 | From | Roman Gushchin <> | Subject | Re: [PATCH net] Revert "defer call to mem_cgroup_sk_alloc()" |
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On Fri, Feb 02, 2018 at 09:59:27AM -0800, Eric Dumazet wrote: > On Fri, 2018-02-02 at 16:57 +0000, Roman Gushchin wrote: > > This patch effectively reverts commit 9f1c2674b328 ("net: memcontrol: > > defer call to mem_cgroup_sk_alloc()"). > > > > Moving mem_cgroup_sk_alloc() to the inet_csk_accept() completely breaks > > memcg socket memory accounting, as packets received before memcg > > pointer initialization are not accounted and are causing refcounting > > underflow on socket release. > > > > Actually the free-after-use problem was fixed by > > commit c0576e397508 ("net: call cgroup_sk_alloc() earlier in > > sk_clone_lock()") for the cgroup pointer. > > > > So, let's revert it and call mem_cgroup_sk_alloc() just before > > cgroup_sk_alloc(). This is safe, as we hold a reference to the socket > > we're cloning, and it holds a reference to the memcg. > > > > Signed-off-by: Roman Gushchin <guro@fb.com> > > Cc: Eric Dumazet <edumazet@google.com> > > Cc: David S. Miller <davem@davemloft.net> > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > Cc: Tejun Heo <tj@kernel.org> > > --- > > mm/memcontrol.c | 14 ++++++++++++++ > > net/core/sock.c | 5 +---- > > net/ipv4/inet_connection_sock.c | 1 - > > 3 files changed, 15 insertions(+), 5 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 0ae2dc3a1748..0937f2c52c7d 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -5747,6 +5747,20 @@ void mem_cgroup_sk_alloc(struct sock *sk) > > if (!mem_cgroup_sockets_enabled) > > return; > > > > + /* > > + * Socket cloning can throw us here with sk_memcg already > > + * filled. It won't however, necessarily happen from > > + * process context. So the test for root memcg given > > + * the current task's memcg won't help us in this case. > > + * > > + * Respecting the original socket's memcg is a better > > + * decision in this case. > > + */ > > + if (sk->sk_memcg) { > > Original commit had a BUG_ON(mem_cgroup_is_root(sk->sk_memcg)); > > I presume it is no longer useful ?
Idk, how even we can hit it? And if so, what scary will happen?
If you prefer to have it there, I definitely can return it, but I see no profit so far.
Thanks!
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