From: Jakub Sitnicki <jakub@cloudflare.com>
To: sdf@google.com
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
kernel-team@cloudflare.com, Petar Penkov <ppenkov@google.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>
Subject: Re: [PATCH bpf] flow_dissector: Drop BPF flow dissector prog ref on netns cleanup
Date: Thu, 21 May 2020 10:42:14 +0200 [thread overview]
Message-ID: <20200521104214.6a1a4f9c@toad> (raw)
In-Reply-To: <20200520174000.GA49942@google.com>
On Wed, 20 May 2020 10:40:00 -0700
sdf@google.com wrote:
> > +static void __net_exit flow_dissector_pernet_pre_exit(struct net *net)
> > +{
> > + struct bpf_prog *attached;
> > +
> > + /* We don't lock the update-side because there are no
> > + * references left to this netns when we get called. Hence
> > + * there can be no attach/detach in progress.
> > + */
> > + rcu_read_lock();
> > + attached = rcu_dereference(net->flow_dissector_prog);
> > + if (attached) {
> > + RCU_INIT_POINTER(net->flow_dissector_prog, NULL);
> > + bpf_prog_put(attached);
> > + }
> > + rcu_read_unlock();
> > +}
> I wonder, should we instead refactor existing
> skb_flow_dissector_bpf_prog_detach to accept netns (instead of attr)
> can call that here? Instead of reimplementing it (I don't think we
> care about mutex lock/unlock efficiency here?). Thoughts?
I wanted to be nice to container-heavy workloads where network
namespaces get torn down frequently and in parallel and avoid
locking a global mutex. OTOH we already do it today, for instance in
devlink pre_exit callback.
In our case I think there is a way to have the cake and it eat too:
https://lore.kernel.org/bpf/20200521083435.560256-1-jakub@cloudflare.com/
Thanks for reviewing it,
-jkbs
next prev parent reply other threads:[~2020-05-21 8:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 17:22 [PATCH bpf] flow_dissector: Drop BPF flow dissector prog ref on netns cleanup Jakub Sitnicki
2020-05-20 17:40 ` sdf
2020-05-21 0:56 ` Alexei Starovoitov
2020-05-21 8:42 ` Jakub Sitnicki [this message]
2020-05-21 19:08 ` Andrii Nakryiko
2020-05-22 0:53 ` Alexei Starovoitov
2020-05-22 8:22 ` Jakub Sitnicki
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