netdev - Re: [PATCH 2/2] virtio-net: make all RX paths handle erors consistently

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Message-ID: <5296DD69.4080201@redhat.com>
Date:	Thu, 28 Nov 2013 14:06:33 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	Michael Dalton <mwdalton@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH 2/2] virtio-net: make all RX paths handle erors consistently

On 11/28/2013 12:31 AM, Michael S. Tsirkin wrote:
> receive mergeable now handles errors internally.
> Do same for big and small packet paths, otherwise
> the logic is too hard to follow.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>
> While I can't point at a bug this fixes, I'm not sure
> there's no bug in the existing logic.
> So not exactly a bug fix bug I think it's justified for net.
>
>  drivers/net/virtio_net.c | 53 +++++++++++++++++++++++++++++++++---------------
>  1 file changed, 37 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 0e6ea69..97c6212 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -299,6 +299,35 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
>  	return skb;
>  }
>  
> +static struct sk_buff *receive_small(void *buf, unsigned int len)
> +{
> +	struct sk_buff * skb = buf;
> +
> +	len -= sizeof(struct virtio_net_hdr);
> +	skb_trim(skb, len);
> +
> +	return skb;
> +}
> +
> +static struct sk_buff *receive_big(struct net_device *dev,
> +				   struct receive_queue *rq,
> +				   void *buf,
> +				   unsigned int len)
> +{
> +	struct page *page = buf;
> +	struct sk_buff *skb = page_to_skb(rq, page, 0, len, PAGE_SIZE);
> +
> +	if (unlikely(!skb))
> +		goto err;
> +
> +	return skb;
> +
> +err:
> +	dev->stats.rx_dropped++;
> +	give_pages(rq, page);
> +	return NULL;
> +}
> +
>  static struct sk_buff *receive_mergeable(struct net_device *dev,
>  					 struct receive_queue *rq,
>  					 void *buf,
> @@ -407,23 +436,15 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
>  		return;
>  	}
>  
> -	if (!vi->mergeable_rx_bufs && !vi->big_packets) {
> -		skb = buf;
> -		len -= sizeof(struct virtio_net_hdr);
> -		skb_trim(skb, len);
> -	} else if (vi->mergeable_rx_bufs) {
> +	if (vi->mergeable_rx_bufs)
>  		skb = receive_mergeable(dev, rq, buf, len);
> -		if (unlikely(!skb))
> -			return;
> -	} else {
> -		page = buf;
> -		skb = page_to_skb(rq, page, 0, len, PAGE_SIZE);
> -		if (unlikely(!skb)) {
> -			dev->stats.rx_dropped++;
> -			give_pages(rq, page);
> -			return;
> -		}
> -	}
> +	else if (vi->big_packets)
> +		skb = receive_big(dev, rq, buf, len);
> +	else
> +		skb = receive_small(buf, len);
> +
> +	if (unlikely(!skb))
> +		return;
>  
>  	hdr = skb_vnet_hdr(skb);
>  

Acked-by: Jason Wang <jasowang@...hat.com>
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