netdev - Re: [PATCH net-next] net: minor __alloc

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Message-ID: <CANn89iKDrx0DP56AynzMuKv4so7DFEFpFE2yHg6gCGugzd4ivQ@mail.gmail.com>
Date: Wed, 14 Jan 2026 02:54:10 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "David S . Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, 
	Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] net: minor __alloc_skb() optimization

On Wed, Jan 14, 2026 at 2:44 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 13 Jan 2026 13:10:17 +0000 Eric Dumazet wrote:
> > We can directly call __finalize_skb_around()
> > instead of __build_skb_around() because @size is not zero.
>
> FWIW I've been tempted to delete the zero check from
> __build_skb_around() completely recently..
> It's been a few years since we added slab_build_skb()
> surely any buggy driver that's actually used would have
> already hit that WARN_ONCE() and gotten reported?

We could keep it for a while, WDYT of

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 77508cf7c41e829a11a988d8de3d2673ff1ff121..ccd287ff46e91c2548483c51fa32fc6167867940
100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -458,7 +458,8 @@ static void __build_skb_around(struct sk_buff
*skb, void *data,
        /* frag_size == 0 is considered deprecated now. Callers
         * using slab buffer should use slab_build_skb() instead.
         */
-       if (WARN_ONCE(size == 0, "Use slab_build_skb() instead"))
+       if (IS_ENABLED(CONFIG_DEBUG_NET) &&
+           WARN_ONCE(size == 0, "Use slab_build_skb() instead"))
                data = __slab_build_skb(data, &size);

        __finalize_skb_around(skb, data, size);