linux-kernel - Re: [PATCH] virtio_net: Use BUG_ON instead of if condition followed by BUG

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Date:   Mon, 17 May 2021 16:35:20 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Xianting Tian <xianting.tian@...ux.alibaba.com>
Cc:     mst@...hat.com, jasowang@...hat.com, davem@...emloft.net,
        kuba@...nel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_net: Use BUG_ON instead of if condition followed
 by BUG

On Mon, May 17, 2021 at 09:31:19PM +0800, Xianting Tian wrote:
> BUG_ON() uses unlikely in if(), which can be optimized at compile time.
> 
> Signed-off-by: Xianting Tian <xianting.tian@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c921ebf3ae82..212d52204884 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1646,10 +1646,9 @@ static int xmit_skb(struct send_queue *sq, struct
> sk_buff *skb)
>  	else
>  		hdr = skb_vnet_hdr(skb);
> 
> -	if (virtio_net_hdr_from_skb(skb, &hdr->hdr,

How fatal is it not being able to get the header from the skb? There
has been push back on the use of BUG() or its variants, since it kills
the machine dead. Would it be possible to turn this into a WARN_ON and
return -EPROTO or something?

       Andrew