virtio_net: Check for room in the vq before adding buffer

Saves us one cycle of alloc-add-free if the queue was full.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (modified)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index effe8c6..d445845 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -280,7 +280,7 @@ static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp)
        bool oom = false;
 
        sg_init_table(sg, 2+MAX_SKB_FRAGS);
-       for (;;) {
+       do {
                struct skb_vnet_hdr *hdr;
 
                skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN + NET_IP_ALIGN);
@@ -323,7 +323,7 @@ static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp)
                        break;
                }
                vi->num++;
-       }
+       } while (err >= num);
        if (unlikely(vi->num > vi->max))
                vi->max = vi->num;
        vi->rvq->vq_ops->kick(vi->rvq);
@@ -341,7 +341,7 @@ static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
        if (!vi->mergeable_rx_bufs)
                return try_fill_recv_maxbufs(vi, gfp);
 
-       for (;;) {
+       do {
                skb_frag_t *f;
 
                skb = netdev_alloc_skb(vi->dev, GOOD_COPY_LEN + NET_IP_ALIGN);
@@ -375,7 +375,7 @@ static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
                        break;
                }
                vi->num++;
-       }
+       } while (err > 0);
        if (unlikely(vi->num > vi->max))
                vi->max = vi->num;
        vi->rvq->vq_ops->kick(vi->rvq);