linux-kernel - Re: [PATCH] net: ag71xx: remove dead code path

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Message-ID: <196dc563-85ec-491d-8e2e-8749f3b07ff4@lunn.ch>
Date: Tue, 10 Sep 2024 17:58:22 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Qianqiang Liu <qianqiang.liu@....com>
Cc: chris.snook@...il.com, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Oleksij Rempel <o.rempel@...gutronix.de>
Subject: Re: [PATCH] net: ag71xx: remove dead code path

On Tue, Sep 10, 2024 at 11:22:54PM +0800, Qianqiang Liu wrote:
> The 'err' is always zero, so the following branch can never be executed:
> if (err) {
> 	ndev->stats.rx_dropped++;
> 	kfree_skb(skb);
> }
> Therefore, the 'if' statement can be removed.

This code was added by Oleksij Rempel <o.rempel@...gutronix.de>. It is
good to Cc: him, he might have useful comments.

Your changed does look correct, but maybe ret was actually supposed to
be set somewhere? Is there an actual bug hiding here somewhere?

     Andrew

> 
> Signed-off-by: Qianqiang Liu <qianqiang.liu@....com>
> ---
>  drivers/net/ethernet/atheros/ag71xx.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/ethernet/atheros/ag71xx.c b/drivers/net/ethernet/atheros/ag71xx.c
> index 96a6189cc31e..5477f3f87e10 100644
> --- a/drivers/net/ethernet/atheros/ag71xx.c
> +++ b/drivers/net/ethernet/atheros/ag71xx.c
> @@ -1616,7 +1616,6 @@ static int ag71xx_rx_packets(struct ag71xx *ag, int limit)
>  		unsigned int i = ring->curr & ring_mask;
>  		struct ag71xx_desc *desc = ag71xx_ring_desc(ring, i);
>  		int pktlen;
> -		int err = 0;
>  
>  		if (ag71xx_desc_empty(desc))
>  			break;
> @@ -1646,14 +1645,9 @@ static int ag71xx_rx_packets(struct ag71xx *ag, int limit)
>  		skb_reserve(skb, offset);
>  		skb_put(skb, pktlen);
>  
> -		if (err) {
> -			ndev->stats.rx_dropped++;
> -			kfree_skb(skb);
> -		} else {
> -			skb->dev = ndev;
> -			skb->ip_summed = CHECKSUM_NONE;
> -			list_add_tail(&skb->list, &rx_list);
> -		}
> +		skb->dev = ndev;
> +		skb->ip_summed = CHECKSUM_NONE;
> +		list_add_tail(&skb->list, &rx_list);
>  
>  next:
>  		ring->buf[i].rx.rx_buf = NULL;
> -- 
> 2.39.2
> 
>