virtio: flush buffers on open

Fix bug found by Christian Borntraeger: if the other side fills all
the registered network buffers before we enable NAPI, we will never
get an interrupt.  The simplest fix is to process the input queue once
on open.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index be5688f5e9310d30376e5fb98c6221dd1b33bc4c..bd4d26a36eadcb1a95bac0ba5226cf3254b400d2 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -283,6 +283,13 @@ static int virtnet_open(struct net_device *dev)
        struct virtnet_info *vi = netdev_priv(dev);
 
        napi_enable(&vi->napi);
+
+       /* If all buffers were filled by other side before we napi_enabled, we
+        * won't get another interrupt, so process any outstanding packets
+        * now.  virtnet_poll wants re-enable the queue, so we disable here. */
+       vi->rvq->vq_ops->disable_cb(vi->rvq);
+       netif_rx_schedule(vi->dev, &vi->napi);
+
        return 0;
 }