netdev - Re: [PATCH] xen-netback: correct success/error reporting for the SKB-with-fraglist case

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Message-ID: <67bc0728-761b-c3dd-bdd5-1a850ff79fbb@xen.org>
Date:   Wed, 24 Feb 2021 16:39:14 +0000
From:   Paul Durrant <xadimgnik@...il.com>
To:     Jan Beulich <jbeulich@...e.com>, Wei Liu <wl@....org>
Cc:     "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] xen-netback: correct success/error reporting for the
 SKB-with-fraglist case

On 23/02/2021 16:29, Jan Beulich wrote:
> When re-entering the main loop of xenvif_tx_check_gop() a 2nd time, the
> special considerations for the head of the SKB no longer apply. Don't
> mistakenly report ERROR to the frontend for the first entry in the list,
> even if - from all I can tell - this shouldn't matter much as the overall
> transmit will need to be considered failed anyway.
> 
> Signed-off-by: Jan Beulich <jbeulich@...e.com>
> 
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -499,7 +499,7 @@ check_frags:
>   				 * the header's copy failed, and they are
>   				 * sharing a slot, send an error
>   				 */
> -				if (i == 0 && sharedslot)
> +				if (i == 0 && !first_shinfo && sharedslot)
>   					xenvif_idx_release(queue, pending_idx,
>   							   XEN_NETIF_RSP_ERROR);
>   				else
> 

I think this will DTRT, but to my mind it would make more sense to clear 
'sharedslot' before the 'goto check_frags' at the bottom of the function.

   Paul