Re: netback Oops then xenwatch stuck in D state

[David Vrabel <dvrabel@cantab.net>]

On 13/02/13 18:37, Wei Liu wrote:
> A slightly upgraded version of the *UNTESTED* patch.
> 
> 
> Wei.
> 
> ----8<----
> commit df4c929d034cec7043fbd96ba89833eb639c336e
> Author: Wei Liu <wei.liu2@citrix.com>
> Date:   Wed Feb 13 18:17:01 2013 +0000
> 
>     netback: fix netbk_count_requests
>     
>     There are two paths in the original code, a) test against work_to_do, b) test
>     against first->size, could return 0 even when error happens.
>     
>     Simply return -1 in error paths should work. Modify all error paths to return
>     -1 to be consistent.

You also need to remove the netbk_tx_err() after checking the result of
netbk_count_requests().  Otherwise you will have a double xenvif_put(),
which will screw up ref counting.

I would also suggest returning -EINVAL from netbk_count_requests().

It not clear to me how this will fix the original oops though.

David

>     
>     Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> 
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 103294d..0e0162e 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -913,13 +913,13 @@ static int netbk_count_requests(struct xenvif *vif,
>  		if (frags >= work_to_do) {
>  			netdev_err(vif->dev, "Need more frags\n");
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -1;
>  		}
>  
>  		if (unlikely(frags >= MAX_SKB_FRAGS)) {
>  			netdev_err(vif->dev, "Too many frags\n");
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -1;
>  		}
>  
>  		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
> @@ -927,7 +927,7 @@ static int netbk_count_requests(struct xenvif *vif,
>  		if (txp->size > first->size) {
>  			netdev_err(vif->dev, "Frag is bigger than frame.\n");
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -1;
>  		}
>  
>  		first->size -= txp->size;
> @@ -937,7 +937,7 @@ static int netbk_count_requests(struct xenvif *vif,
>  			netdev_err(vif->dev, "txp->offset: %x, size: %u\n",
>  				 txp->offset, txp->size);
>  			netbk_fatal_tx_err(vif);
> -			return -frags;
> +			return -1;
>  		}
>  	} while ((txp++)->flags & XEN_NETTXF_more_data);
>  	return frags;
> 
> 
> 
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