linux-kernel - Re: [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL in napi_gro

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Date:   Wed, 24 Jun 2020 15:06:06 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Alexander Lobakin <alobakin@...nk.ru>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Edward Cree <ecree@...arflare.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Petr Machata <petrm@...lanox.com>,
        Sabrina Dubroca <sd@...asysnail.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL
 in napi_gro_receive()

Hi Alexander,

This patch introduced a behavior change around GRO_DROP:

napi_skb_finish used to sometimes return GRO_DROP:

> -static gro_result_t napi_skb_finish(gro_result_t ret, struct sk_buff *skb)
> +static gro_result_t napi_skb_finish(struct napi_struct *napi,
> +				    struct sk_buff *skb,
> +				    gro_result_t ret)
>  {
>  	switch (ret) {
>  	case GRO_NORMAL:
> -		if (netif_receive_skb_internal(skb))
> -			ret = GRO_DROP;
> +		gro_normal_one(napi, skb);
>

But under your change, gro_normal_one and the various calls that makes
never propagates its return value, and so GRO_DROP is never returned to
the caller, even if something drops it.

Was this intentional? Or should I start looking into how to restore it?

Thanks,
Jason