virtio: free transmit skbs when notified, not on next xmit.

This fixes a potential dangling xmit problem.

We also suppress refill interrupts until we need them.

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

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index bd4d26a36eadcb1a95bac0ba5226cf3254b400d2..a61c176607f4585b53a7514c90b89a9de0ce30ef 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -56,11 +56,13 @@ static inline void vnet_hdr_to_sg(struct scatterlist *sg, struct sk_buff *skb)
        sg_init_one(sg, skb_vnet_hdr(skb), sizeof(struct virtio_net_hdr));
 }
 
-static void skb_xmit_done(struct virtqueue *rvq)
+static void skb_xmit_done(struct virtqueue *svq)
 {
-       struct virtnet_info *vi = rvq->vdev->priv;
+       struct virtnet_info *vi = svq->vdev->priv;
 
-       /* In case we were waiting for output buffers. */
+       /* Suppress further interrupts. */
+       svq->vq_ops->disable_cb(svq);
+       /* We were waiting for more output buffers. */
        netif_wake_queue(vi->dev);
 }
 
@@ -232,8 +234,6 @@ static int start_xmit(struct sk_buff *skb, struct net_device *dev)
 
        pr_debug("%s: xmit %p %s\n", dev->name, skb, print_mac(mac, dest));
 
-       free_old_xmit_skbs(vi);
-
        /* Encode metadata header at front. */
        hdr = skb_vnet_hdr(skb);
        if (skb->ip_summed == CHECKSUM_PARTIAL) {
@@ -266,11 +266,24 @@ static int start_xmit(struct sk_buff *skb, struct net_device *dev)
        vnet_hdr_to_sg(sg, skb);
        num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
        __skb_queue_head(&vi->send, skb);
+
+again:
+       /* Free up any pending old buffers before queueing new ones. */
+       free_old_xmit_skbs(vi);
        err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
        if (err) {
                pr_debug("%s: virtio not prepared to send\n", dev->name);
-               skb_unlink(skb, &vi->send);
                netif_stop_queue(dev);
+
+               /* Activate callback for using skbs: if this fails it
+                * means some were used in the meantime. */
+               if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
+                       printk("Unlikely: restart svq failed\n");
+                       netif_start_queue(dev);
+                       goto again;
+               }
+               __skb_unlink(skb, &vi->send);
+
                return NETDEV_TX_BUSY;
        }
        vi->svq->vq_ops->kick(vi->svq);