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References: <20210821155327.251284-1-yan2228598786@gmail.com>
In-Reply-To: <20210821155327.251284-1-yan2228598786@gmail.com>
From:   Cong Wang <xiyou.wangcong@gmail.com>
Date:   Mon, 23 Aug 2021 12:06:59 -0700
Message-ID: <CAM_iQpWY4Mmf2EUPQDp0v5dj2Ch2KVRirgJXRwLea3pRnkSJVg@mail.gmail.com>
Subject: Re: [PATCH] net/mlx4: tcp_drop replace of tcp_drop_new
To:     jony-one <yan2228598786@gmail.com>
Cc:     Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        David Miller <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        dsahern@kernel.org,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, hengqi.chen@gmail.com,
        Yonghong Song <yhs@fb.com>
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Precedence: bulk

On Sat, Aug 21, 2021 at 8:55 AM jony-one <yan2228598786@gmail.com> wrote:
> @@ -4676,7 +4683,7 @@ static void tcp_ofo_queue(struct sock *sk)
>                 rb_erase(&skb->rbnode, &tp->out_of_order_queue);
>
>                 if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) {
> -                       tcp_drop(sk, skb);
> +                       tcp_drop_new(sk, skb, __func__);

This is very similar to race_kfree_skb():

void kfree_skb(struct sk_buff *skb)
{
        if (!skb_unref(skb))
                return;

        trace_kfree_skb(skb, __builtin_return_address(0));
        __kfree_skb(skb);
}

So... why not something like this?

iff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3f7bd7ae7d7a..cc840e4552c9 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4678,6 +4678,7 @@ static bool tcp_ooo_try_coalesce(struct sock *sk,
 static void tcp_drop(struct sock *sk, struct sk_buff *skb)
 {
        sk_drops_add(sk, skb);
+       trace_kfree_skb(skb, __builtin_return_address(0));
        __kfree_skb(skb);
 }

Thanks.