linux-kernel - Re: [PATCH net-next 2/2] bpf: avoid unused variable warning in tcp_bpf

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Message-ID: <CACSApvYkWwjzOhu+rvv1LOkcFYbU8Jgw=Q1f+HrCReEeKBLuuA@mail.gmail.com>
Date:   Mon, 8 Jul 2019 09:55:11 -0400
From:   Soheil Hassas Yeganeh <soheil@...gle.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Priyaranjan Jha <priyarjha@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Jason Baron <jbaron@...mai.com>,
        Yafang Shao <laoar.shao@...il.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, bpf@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] bpf: avoid unused variable warning in tcp_bpf_rtt()

On Mon, Jul 8, 2019 at 8:57 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> When CONFIG_BPF is disabled, we get a warning for an unused
> variable:
>
> In file included from drivers/target/target_core_device.c:26:
> include/net/tcp.h:2226:19: error: unused variable 'tp' [-Werror,-Wunused-variable]
>         struct tcp_sock *tp = tcp_sk(sk);
>
> The variable is only used in one place, so it can be
> replaced with its value there to avoid the warning.
>
> Fixes: 23729ff23186 ("bpf: add BPF_CGROUP_SOCK_OPS callback that is executed on every RTT")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>

> ---
>  include/net/tcp.h | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index e16d8a3fd3b4..cca3c59b98bf 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -2223,9 +2223,7 @@ static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
>
>  static inline void tcp_bpf_rtt(struct sock *sk)
>  {
> -       struct tcp_sock *tp = tcp_sk(sk);
> -
> -       if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTT_CB_FLAG))
> +       if (BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), BPF_SOCK_OPS_RTT_CB_FLAG))
>                 tcp_call_bpf(sk, BPF_SOCK_OPS_RTT_CB, 0, NULL);
>  }
>
> --
> 2.20.0
>