linux-kernel - Re: [PATCH for-next v4] cgroup/bpf: fast path skb BPF filtering

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Date:   Wed, 26 Jan 2022 21:08:24 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Pavel Begunkov <asml.silence@...il.com>
Cc:     Martin KaFai Lau <kafai@...com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Song Liu <songliubraving@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stanislav Fomichev <sdf@...gle.com>
Subject: Re: [PATCH for-next v4] cgroup/bpf: fast path skb BPF filtering

On Wed, Jan 26, 2022 at 1:29 PM Pavel Begunkov <asml.silence@...il.com> wrote:
>
> On 1/26/22 20:30, Martin KaFai Lau wrote:
> > On Wed, Jan 26, 2022 at 12:22:13AM +0000, Pavel Begunkov wrote:
> >>   #define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb)                        \
> >>   ({                                                                       \
> >>      int __ret = 0;                                                        \
> >> -    if (cgroup_bpf_enabled(CGROUP_INET_INGRESS))                  \
> >> +    if (cgroup_bpf_enabled(CGROUP_INET_INGRESS) && sk &&                  \
> >  From reading sk_filter_trim_cap() where this will be called, sk cannot be NULL.
> > If yes, the new sk test is not needed.
>
> Well, there is no sane way to verify how it's used considering
>
> EXPORT_SYMBOL(__cgroup_bpf_run_filter_skb);

BPF_CGROUP_RUN_PROG_INET_INGRESS() is used in one place.
Are you folks saying that you want to remove !sk check
from __cgroup_bpf_run_filter_skb()?
Seems like micro optimization, but sure why not.

EXPORT_SYMBOL() is there because of "ipv6 as a module" mess.
So it's not a concern.

Pls tag the subj of the patch with [PATCH bpf-next]
instead of "for-next".