netdev - Re: [PATCH v2 3/3] xen/netback: use same error messages for same errors

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Date:   Tue, 28 Mar 2023 15:32:41 +0200
From:   Jan Beulich <jbeulich@...e.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     Wei Liu <wei.liu@...nel.org>, Paul Durrant <paul@....org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 3/3] xen/netback: use same error messages for same
 errors

On 28.03.2023 15:12, Juergen Gross wrote:
> Issue the same error message in case an illegal page boundary crossing
> has been detected in both cases where this is tested.
> 
> Suggested-by: Jan Beulich <jbeulich@...e.com>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
> V2:
> - new patch
> ---
>  drivers/net/xen-netback/netback.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 9ca4b69d3b39..5dfdec44354a 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -996,10 +996,8 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue,
>  
>  		/* No crossing a page as the payload mustn't fragment. */
>  		if (unlikely((txreq.offset + txreq.size) > XEN_PAGE_SIZE)) {
> -			netdev_err(queue->vif->dev,
> -				   "txreq.offset: %u, size: %u, end: %lu\n",
> -				   txreq.offset, txreq.size,
> -				   (unsigned long)(txreq.offset&~XEN_PAGE_MASK) + txreq.size);
> +			netdev_err(queue->vif->dev, "Cross page boundary, txp->offset: %u, size: %u\n",
> +				   txreq.offset, txreq.size);
>  			xenvif_fatal_tx_err(queue->vif);
>  			break;
>  		}

To be honest I'm of the opinion that this goes slightly too far:
Making the two messages more similar is certainly helpful. But in
case of problems I think it wouldn't hurt if they're still
distinguishable - when the one here triggers it may e.g also mean
that the calculation of the residual size is causing an issue. So
maybe stick to txreq.offset in the message text, with everything
else left as you have it?

Jan