[3.8.y.z extended stable] Patch "virtio-net: make all RX paths handle errors consistently" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    virtio-net: make all RX paths handle errors consistently

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.16.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 01d2550ae19cb00149bcd9283de2eedf1c1d7de5 Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst at redhat.com>
Date: Thu, 26 Dec 2013 15:32:51 +0200
Subject: virtio-net: make all RX paths handle errors consistently

commit f121159d72091f25afb22007c833e60a6845e912 upstream.

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)
Acked-by: Jason Wang <jasowang at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 184c59c..840cf2f 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -294,6 +294,34 @@ 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,
@@ -357,7 +385,6 @@ 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)) {
@@ -369,26 +396,15 @@ 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);

--
1.8.3.2