netdev - Re: [PATCH] net/mlx4: tcp_drop replace of tcp_drop

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Date:   Mon, 23 Aug 2021 12:06:59 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     jony-one <yan2228598786@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        David Miller <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        dsahern@...nel.org,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, hengqi.chen@...il.com,
        Yonghong Song <yhs@...com>
Subject: Re: [PATCH] net/mlx4: tcp_drop replace of tcp_drop_new

On Sat, Aug 21, 2021 at 8:55 AM jony-one <yan2228598786@...il.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.