linux-kernel - Re: [PATCH net-next v6 1/5] net: hdlc_fr: Simpify fr_rx by using "goto rx

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Date:   Sat, 31 Oct 2020 10:32:53 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Xie He <xie.he.0141@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Krzysztof Halasa <khc@...waw.pl>
Subject: Re: [PATCH net-next v6 1/5] net: hdlc_fr: Simpify fr_rx by using
 "goto rx_drop" to drop frames

On Fri, Oct 30, 2020 at 8:50 PM Xie He <xie.he.0141@...il.com> wrote:
>
> When the fr_rx function drops a received frame (because the protocol type
> is not supported, or because the PVC virtual device that corresponds to
> the DLCI number and the protocol type doesn't exist), the function frees
> the skb and returns.
>
> The code for freeing the skb and returning is repeated several times, this
> patch uses "goto rx_drop" to replace them so that the code looks cleaner.
>
> Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> Cc: Krzysztof Halasa <khc@...waw.pl>
> Signed-off-by: Xie He <xie.he.0141@...il.com>
> ---
>  drivers/net/wan/hdlc_fr.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/wan/hdlc_fr.c b/drivers/net/wan/hdlc_fr.c
> index 409e5a7ad8e2..4db0e01b96a9 100644
> --- a/drivers/net/wan/hdlc_fr.c
> +++ b/drivers/net/wan/hdlc_fr.c
> @@ -904,8 +904,7 @@ static int fr_rx(struct sk_buff *skb)
>                 netdev_info(frad, "No PVC for received frame's DLCI %d\n",
>                             dlci);
>  #endif
> -               dev_kfree_skb_any(skb);
> -               return NET_RX_DROP;
> +               goto rx_drop;
>         }
>
>         if (pvc->state.fecn != fh->fecn) {
> @@ -963,14 +962,12 @@ static int fr_rx(struct sk_buff *skb)
>                 default:
>                         netdev_info(frad, "Unsupported protocol, OUI=%x PID=%x\n",
>                                     oui, pid);
> -                       dev_kfree_skb_any(skb);
> -                       return NET_RX_DROP;
> +                       goto rx_drop;
>                 }
>         } else {
>                 netdev_info(frad, "Unsupported protocol, NLPID=%x length=%i\n",
>                             data[3], skb->len);
> -               dev_kfree_skb_any(skb);
> -               return NET_RX_DROP;
> +               goto rx_drop;
>         }
>
>         if (dev) {
> @@ -982,12 +979,12 @@ static int fr_rx(struct sk_buff *skb)
>                 netif_rx(skb);
>                 return NET_RX_SUCCESS;
>         } else {
> -               dev_kfree_skb_any(skb);
> -               return NET_RX_DROP;
> +               goto rx_drop;
>         }
>
> - rx_error:
> +rx_error:
>         frad->stats.rx_errors++; /* Mark error */
> +rx_drop:
>         dev_kfree_skb_any(skb);
>         return NET_RX_DROP;

I meant that I don't think errors should be double counted in rx_error
and rx_drop. It is fine to count drops as either.

Especially without that, I'm not sure this and the follow-on patch add
much value. Minor code cleanups complicate backports of fixes.