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

[Juergen Gross <jgross@xxxxxxxx>]

On 07.12.22 10:25, Jan Beulich wrote:
> 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.
The comment at the end of that loop seems to imply this is the desired
behavior:

                /* Remember the error: invalidate all subsequent fragments. */
                err = newerr;
        }


Juergen

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