vhost-net: initialize zcopy packet counters

These packet counters are used to drive the zercopy selection heuristic so nothing too bad happens if they are off a bit - and they are also reset once in a while.
But it's cleaner to clear them when backend is set so that we start in a known state.

---
 drivers/vhost/net.c | 3 +++
 1 file changed, 3 insertions(+)

index 67898fa..ff6c9199 100644
@@ -823,6 +823,9 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 		r = vhost_init_used(vq);
 		if (r)
 			goto err_vq;
+
+		n->tx_packets = 0;
+		n->tx_zcopy_err = 0;
 	}
 
 	mutex_unlock(&vq->mutex);

MST

From: "Michael S. Tsirkin" <[email protected]>
Date: Mon, 3 Dec 2012 19:31:51 +0200

Applied to net-next, thanks.