Re: [PATCH] xen/netback: fix build warning

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.12.2022 08:23, Juergen Gross wrote:
> Commit ad7f402ae4f4 ("xen/netback: Ensure protocol headers don't fall in
> the non-linear area") introduced a (valid) build warning.
> 
> Fix it.
> 
> Fixes: ad7f402ae4f4 ("xen/netback: Ensure protocol headers don't fall in the 
> non-linear area")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -530,7 +530,7 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
>       const bool sharedslot = nr_frags &&
>                               frag_get_pending_idx(&shinfo->frags[0]) ==
>                                   copy_pending_idx(skb, copy_count(skb) - 1);
> -     int i, err;
> +     int i, err = 0;
>  
>       for (i = 0; i < copy_count(skb); i++) {
>               int newerr;

I'm afraid other logic (below here) is now slightly wrong as well, in
particular 

                                /* If the mapping of the first frag was OK, but
                                 * the header's copy failed, and they are
                                 * sharing a slot, send an error
                                 */
                                if (i == 0 && !first_shinfo && sharedslot)
                                        xenvif_idx_release(queue, pending_idx,
                                                           XEN_NETIF_RSP_ERROR);
                                else
                                        xenvif_idx_release(queue, pending_idx,
                                                           XEN_NETIF_RSP_OKAY);

which looks to be intended to deal with _only_ failure of the one shared
part of the header, whereas "err" now can indicate an error on any earlier
part as well.

Jan