hyperv: Enable sendbuf mechanism on the send path

We send packets using a copy-free mechanism (this is the Guest to Host transport
via VMBUS). While this is obviously optimal for large packets,
it may not be optimal for small packets. Hyper-V host supports
a second mechanism for sending packets that is "copy based". We implement that
mechanism in this patch.

In this version of the patch I have addressed a comment from David Miller.

With this patch (and all of the other offload and VRSS patches), we are now able
to almost saturate a 10G interface between Linux VMs on Hyper-V
on different hosts - close to  9 Gbps as measured via iperf.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index c76b66515e92..939e3af60ec4 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -236,10 +236,11 @@ static void netvsc_xmit_completion(void *context)
         struct hv_netvsc_packet *packet = (struct hv_netvsc_packet *)context;
         struct sk_buff *skb = (struct sk_buff *)
                 (unsigned long)packet->send_completion_tid;
+        u32 index = packet->send_buf_index;
 
         kfree(packet);
 
-        if (skb)
+        if (skb && (index == NETVSC_INVALID_INDEX))
                 dev_kfree_skb_any(skb);
 }