1 files changed, 40 insertions, 24 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 420388a4c5e8..effe8c685f77 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1,4 +1,4 @@
-/* A simple network driver using virtio.
+/* A network driver using virtio.
  *
  * Copyright 2007 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
  *
@@ -73,6 +73,7 @@ struct skb_vnet_hdr {
                 struct virtio_net_hdr hdr;
                 struct virtio_net_hdr_mrg_rxbuf mhdr;
         };
+        unsigned int num_sg;
 };
 
 static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
@@ -442,23 +443,24 @@ again:
         return received;
 }
 
-static void free_old_xmit_skbs(struct virtnet_info *vi)
+static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
 {
         struct sk_buff *skb;
-        unsigned int len;
+        unsigned int len, tot_sgs = 0;
 
         while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
                 pr_debug("Sent skb %p\n", skb);
                 __skb_unlink(skb, &vi->send);
                 vi->dev->stats.tx_bytes += skb->len;
                 vi->dev->stats.tx_packets++;
+                tot_sgs += skb_vnet_hdr(skb)->num_sg;
                 kfree_skb(skb);
         }
+        return tot_sgs;
 }
 
 static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 {
-        int num;
         struct scatterlist sg[2+MAX_SKB_FRAGS];
         struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
         const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
@@ -502,13 +504,14 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
         else
                 sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr));
 
-        num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
-        return vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
+        hdr->num_sg = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
+        return vi->svq->vq_ops->add_buf(vi->svq, sg, hdr->num_sg, 0, skb);
 }
 
 static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
         struct virtnet_info *vi = netdev_priv(dev);
+        int capacity;
 
 again:
         /* Free up any pending old buffers before queueing new ones. */
@@ -516,27 +519,40 @@ again:
 
         /* Put new one in send queue and do transmit */
         __skb_queue_head(&vi->send, skb);
-        if (likely(xmit_skb(vi, skb) >= 0)) {
-                vi->svq->vq_ops->kick(vi->svq);
-                /* Don't wait up for transmitted skbs to be freed. */
-                skb_orphan(skb);
-                nf_reset(skb);
-                return NETDEV_TX_OK;
+        capacity = xmit_skb(vi, skb);
+
+        /* This can happen with OOM and indirect buffers. */
+        if (unlikely(capacity < 0)) {
+                netif_stop_queue(dev);
+                dev_warn(&dev->dev, "Unexpected full queue\n");
+                if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
+                        vi->svq->vq_ops->disable_cb(vi->svq);
+                        netif_start_queue(dev);
+                        goto again;
+                }
+                return NETDEV_TX_BUSY;
         }
 
-        /* Ring too full for this packet, remove it from queue again. */
-        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 returns false it
-         * means some were used in the meantime. */
-        if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
-                vi->svq->vq_ops->disable_cb(vi->svq);
-                netif_start_queue(dev);
-                goto again;
+        vi->svq->vq_ops->kick(vi->svq);
+        /* Don't wait up for transmitted skbs to be freed. */
+        skb_orphan(skb);
+        nf_reset(skb);
+
+        /* Apparently nice girls don't return TX_BUSY; stop the queue
+         * before it gets out of hand.  Naturally, this wastes entries. */
+        if (capacity < 2+MAX_SKB_FRAGS) {
+                netif_stop_queue(dev);
+                if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
+                        /* More just got used, free them then recheck. */
+                        capacity += free_old_xmit_skbs(vi);
+                        if (capacity >= 2+MAX_SKB_FRAGS) {
+                                netif_start_queue(dev);
+                                vi->svq->vq_ops->disable_cb(vi->svq);
+                        }
+                }
         }
-        return NETDEV_TX_BUSY;
+
+        return NETDEV_TX_OK;
 }
 
 static int virtnet_set_mac_address(struct net_device *dev, void *p)