netdev - Re: [RFC PATCH net] net-gro: restore check for NULL skb in napi_gro

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Date: Fri, 4 Aug 2023 16:45:13 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Tyler Stachecki <stachecki.tyler@...il.com>
Cc: edward.cree@....com, davem@...emloft.net, kuba@...nel.org, 
	pabeni@...hat.com, Edward Cree <ecree.xilinx@...il.com>, netdev@...r.kernel.org, 
	Martin Habets <habetsm.xilinx@...il.com>
Subject: Re: [RFC PATCH net] net-gro: restore check for NULL skb in napi_gro_frags

On Fri, Aug 4, 2023 at 4:36 PM Tyler Stachecki
<stachecki.tyler@...il.com> wrote:
>
> Given that this case is rarely hit, and given that there are some performance
> concerns raised wrt this change, it may be beneficial to hint that this
> branch is unlikely.

This is already done, a compiler should already infer this from this code:

if (unlikely(skb_gro_header_hard(skb, hlen))) {
    eth = skb_gro_header_slow(skb, hlen, 0);
    if (unlikely(!eth)) {
        net_warn_ratelimited("%s: dropping impossible skb from %s\n",
                                           __func__, napi->dev->name);
        napi_reuse_skb(napi, skb);
        return NULL;
    }