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>

1 files changed, 19 insertions, 6 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index bd4d26a36ead..a61c176607f4 100644
--- 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);