netdev - Re: [PATCH net-next] net/sched: act_mirred: avoid printout in the traffic path

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Message-ID: <Yt2CIl7iCoahCPoU@pop-os.localdomain>
Date:   Sun, 24 Jul 2022 10:32:18 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net/sched: act_mirred: avoid printout in the
 traffic path

On Thu, Jul 21, 2022 at 06:19:22PM +0200, Davide Caratti wrote:
> @@ -251,16 +258,8 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,
>  	m_eaction = READ_ONCE(m->tcfm_eaction);
>  	retval = READ_ONCE(m->tcf_action);
>  	dev = rcu_dereference_bh(m->tcfm_dev);
> -	if (unlikely(!dev)) {
> -		pr_notice_once("tc mirred: target device is gone\n");
> +	if (unlikely(!dev || !(dev->flags & IFF_UP)))
>  		goto out;
> -	}
> -
> -	if (unlikely(!(dev->flags & IFF_UP))) {
> -		net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
> -				       dev->name);
> -		goto out;
> -	}

I have no objection, just want to point it out users could still figure
out this drop by tracing kfree_skb(). _Maybe_ we could pass a reason to
kfree_skb_reason() too but it is definitely harder.

Thanks!