[1/3] virtio_net: Recycle some more rx buffer pages

From: Mark McLoughlin <markmc@redhat.com>

Each time we re-fill the recv queue with buffers, we allocate
one too many skbs and free it again when adding fails. We should
recycle the pages allocated in this case.

A previous version of this patch made trim_pages() trim trailing
unused pages from skbs with some paged data, but this actually
caused a barely measurable slowdown.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (use netdev_priv)
---
 drivers/net/virtio_net.c |   21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

 	struct page *p = vi->pages;
@@ -121,14 +131,8 @@ static void receive_skb(struct net_device *dev, struct 
sk_buff *skb,
 	}
 	len -= sizeof(struct virtio_net_hdr);
 
-	if (len <= MAX_PACKET_LEN) {
-		unsigned int i;
-
-		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
-			give_a_page(dev->priv, skb_shinfo(skb)->frags[i].page);
-		skb->data_len = 0;
-		skb_shinfo(skb)->nr_frags = 0;
-	}
+	if (len <= MAX_PACKET_LEN)
+		trim_pages(netdev_priv(dev), skb);
 
 	err = pskb_trim(skb, len);
 	if (err) {
@@ -232,6 +236,7 @@ static void try_fill_recv(struct virtnet_info *vi)
 		err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb);
 		if (err) {
 			skb_unlink(skb, &vi->recv);
+			trim_pages(vi, skb);
 			kfree_skb(skb);
 			break;
 		}

From: Rusty Russell <rusty@rustcorp.com.au>
Date: Mon, 17 Nov 2008 13:44:57 +1030

> @@ -82,6 +82,16 @@ static void give_a_page(struct virtnet_info *vi, struct 
> page *page)

-E_EMAIL_CLIENT_NEWLINES
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From: David Miller <davem@davemloft.net>
Date: Sun, 16 Nov 2008 19:45:05 -0800 (PST)

> From: Rusty Russell <rusty@rustcorp.com.au>
> Date: Mon, 17 Nov 2008 13:44:57 +1030
> 
> > @@ -82,6 +82,16 @@ static void give_a_page(struct virtnet_info *vi, struct 
> > page *page)
> 
> -E_EMAIL_CLIENT_NEWLINES

I got tired of sitting on my thumbs and waiting for the fixed version
of the patch, so I cleared it all out myself and added it to net-next-2.6

Even with the mail client corruption fix this thing didn't even apply
to net-next-2.6 :-(
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On Monday 17 November 2008 17:10:07 David Miller wrote:
> Even with the mail client corruption fix this thing didn't even apply
> to net-next-2.6 :-(

Assume this is the netdev_priv changes.  I'll drop my versions from linux-next 
to avoid screwing Stephen over.

Thanks,
Rusty.

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From: Rusty Russell <rusty@rustcorp.com.au>
Date: Mon, 17 Nov 2008 17:38:54 +1030

> On Monday 17 November 2008 17:10:07 David Miller wrote:
> > Even with the mail client corruption fix this thing didn't even apply
> > to net-next-2.6 :-(
> 
> Assume this is the netdev_priv changes.  I'll drop my versions from linux-next 
> to avoid screwing Stephen over.

That's, that was the main point of this :-)
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