Linux Virtualization - Dec 2013 - [PATCH stable v2 2/3] virtio-net: make all RX paths handle errors consistently

receive mergeable now handles errors internally.
Do same for big and small packet paths, otherwise
the logic is too hard to follow.

Cc: Jason Wang <jasowang at redhat.com>
Cc: David S. Miller <davem at davemloft.net>
Acked-by: Michael Dalton <mwdalton at google.com>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>

(cherry picked from commit f121159d72091f25afb22007c833e60a6845e912)
---
 drivers/net/virtio_net.c | 56 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 36 insertions(+), 20 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 435076f..c0ed6d5 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -297,6 +297,34 @@ 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)
+{
+	struct page *page = buf;
+	struct sk_buff *skb = page_to_skb(rq, page, 0);
+
+	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,
@@ -360,7 +388,6 @@ static void receive_buf(struct receive_queue *rq, void *buf,
unsigned int len)
 	struct net_device *dev = vi->dev;
 	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
 	struct sk_buff *skb;
-	struct page *page;
 	struct skb_vnet_hdr *hdr;
 
 	if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
@@ -372,26 +399,15 @@ static void receive_buf(struct receive_queue *rq, void
*buf, unsigned int len)
 			dev_kfree_skb(buf);
 		return;
 	}
+	if (vi->mergeable_rx_bufs)
+		skb = receive_mergeable(dev, rq, buf, len);
+	else if (vi->big_packets)
+		skb = receive_big(dev, rq, buf);
+	else
+		skb = receive_small(buf, len);
 
-	if (!vi->mergeable_rx_bufs && !vi->big_packets) {
-		skb = buf;
-		len -= sizeof(struct virtio_net_hdr);
-		skb_trim(skb, len);
-	} else {
-		page = buf;
-		if (vi->mergeable_rx_bufs) {
-			skb = receive_mergeable(dev, rq, page, len);
-			if (unlikely(!skb))
-				return;
-		} else {
-			skb = page_to_skb(rq, page, len);
-			if (unlikely(!skb)) {
-				dev->stats.rx_dropped++;
-				give_pages(rq, page);
-				return;
-			}
-		}
-	}
+	if (unlikely(!skb))
+		return;
 
 	hdr = skb_vnet_hdr(skb);
 
-- 
MST

On 12/26/2013 09:32 PM, 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.
>
> Cc: Jason Wang <jasowang at redhat.com>
> Cc: David S. Miller <davem at davemloft.net>
> Acked-by: Michael Dalton <mwdalton at google.com>
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
>
> (cherry picked from commit f121159d72091f25afb22007c833e60a6845e912)
> ---
>  drivers/net/virtio_net.c | 56
+++++++++++++++++++++++++++++++-----------------
>  1 file changed, 36 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 435076f..c0ed6d5 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -297,6 +297,34 @@ 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)
> +{
> +	struct page *page = buf;
> +	struct sk_buff *skb = page_to_skb(rq, page, 0);
> +
> +	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,
> @@ -360,7 +388,6 @@ static void receive_buf(struct receive_queue *rq, void
*buf, unsigned int len)
>  	struct net_device *dev = vi->dev;
>  	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>  	struct sk_buff *skb;
> -	struct page *page;
>  	struct skb_vnet_hdr *hdr;
>  
>  	if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
> @@ -372,26 +399,15 @@ static void receive_buf(struct receive_queue *rq,
void *buf, unsigned int len)
>  			dev_kfree_skb(buf);
>  		return;
>  	}
> +	if (vi->mergeable_rx_bufs)
> +		skb = receive_mergeable(dev, rq, buf, len);
> +	else if (vi->big_packets)
> +		skb = receive_big(dev, rq, buf);
> +	else
> +		skb = receive_small(buf, len);
>  
> -	if (!vi->mergeable_rx_bufs && !vi->big_packets) {
> -		skb = buf;
> -		len -= sizeof(struct virtio_net_hdr);
> -		skb_trim(skb, len);
> -	} else {
> -		page = buf;
> -		if (vi->mergeable_rx_bufs) {
> -			skb = receive_mergeable(dev, rq, page, len);
> -			if (unlikely(!skb))
> -				return;
> -		} else {
> -			skb = page_to_skb(rq, page, len);
> -			if (unlikely(!skb)) {
> -				dev->stats.rx_dropped++;
> -				give_pages(rq, page);
> -				return;
> -			}
> -		}
> -	}
> +	if (unlikely(!skb))
> +		return;
>  
>  	hdr = skb_vnet_hdr(skb);
>  
Acked-by: Jason Wang <jasowang at redhat.com>