netdev - Re: [PATCH v2 1/2] net: macb: Check DMA mappings for error

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Date:	Fri, 28 Feb 2014 16:24:20 -0800
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Ben Hutchings <ben@...adent.org.uk>
CC:	Nicolas Ferre <nicolas.ferre@...el.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Michal Simek <michal.simek@...inx.com>
Subject: Re: [PATCH v2 1/2] net: macb: Check DMA mappings for error

Hi Ben,

On Thu, 2014-02-27 at 11:57PM +0000, Ben Hutchings wrote:
> On Thu, 2014-02-27 at 13:58 -0800, Soren Brinkmann wrote:
> [...]
> > diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
> > index 3190d38e16fb..a9c2ccfc1740 100644
> > --- a/drivers/net/ethernet/cadence/macb.c
> > +++ b/drivers/net/ethernet/cadence/macb.c
> > @@ -632,11 +632,16 @@ static void gem_rx_refill(struct macb *bp)
> >  					   "Unable to allocate sk_buff\n");
> >  				break;
> >  			}
> > -			bp->rx_skbuff[entry] = skb;
> >  
> >  			/* now fill corresponding descriptor entry */
> >  			paddr = dma_map_single(&bp->pdev->dev, skb->data,
> >  					       bp->rx_buffer_size, DMA_FROM_DEVICE);
> > +			if (dma_mapping_error(&bp->pdev->dev, paddr)) {
> > +				dev_kfree_skb(skb);
> > +				break;
> > +			}
> > +
> > +			bp->rx_skbuff[entry] = skb;
> >  
> >  			if (entry == RX_RING_SIZE - 1)
> >  				paddr |= MACB_BIT(RX_WRAP);
> > @@ -1040,6 +1045,10 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
> 
> A bit more context:
> 
> 	entry = macb_tx_ring_wrap(bp->tx_head);
> 	bp->tx_head++;
> 
> >  	netdev_vdbg(bp->dev, "Allocated ring entry %u\n", entry);
> >  	mapping = dma_map_single(&bp->pdev->dev, skb->data,
> >  				 len, DMA_TO_DEVICE);
> > +	if (dma_mapping_error(&bp->pdev->dev, mapping)) {
> > +		kfree_skb(skb);
> > +		goto unlock;
> > +	}
> 
> You need to move the bp->tx_head increment below this error check.
> Sorry I didn't spot this the first time.

No problem. I'll wait till next week with a re-spin, in case somebody
else has comments.

	Sören


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