netvsc: Use the new in-place consumption APIs in the rx path

BugLink: http://bugs.launchpad.net/bugs/1616677

Use the new APIs for eliminating a copy on the receive path. These new APIs also
help in minimizing the number of memory barriers we end up issuing (in the
ringbuffer code) since we can better control when we want to expose the ring
state to the host.

The patch is being resent to address earlier email issues.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 99a50bb1)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/hyperv/netvsc.c

@@ -1128,6 +1128,39 @@ static inline void netvsc_receive_inband(struct hv_device *hdev,
 	}
 }
 
+static void netvsc_process_raw_pkt(struct hv_device *device,
+				   struct vmbus_channel *channel,
+				   struct netvsc_device *net_device,
+				   struct net_device *ndev,
+				   u64 request_id,
+				   struct vmpacket_descriptor *desc)
+{
+	struct nvsp_message *nvmsg;
+
+	nvmsg = (struct nvsp_message *)((unsigned long)
+		desc + (desc->offset8 << 3));
+
+	switch (desc->type) {
+	case VM_PKT_COMP:
+		netvsc_send_completion(net_device, channel, device, desc);
+		break;
+
+	case VM_PKT_DATA_USING_XFER_PAGES:
+		netvsc_receive(net_device, channel, device, desc);
+		break;
+
+	case VM_PKT_DATA_INBAND:
+		netvsc_receive_inband(device, net_device, nvmsg);
+		break;
+
+	default:
+		netdev_err(ndev, "unhandled packet type %d, tid %llx\n",
+			   desc->type, request_id);
+		break;
+	}
+}
+
+
 void netvsc_channel_cb(void *context)
 {
 	int ret;
@@ -1140,7 +1173,7 @@ void netvsc_channel_cb(void *context)
 	unsigned char *buffer;
 	int bufferlen = NETVSC_PACKET_SIZE;
 	struct net_device *ndev;
-	struct nvsp_message *nvmsg;
+	bool need_to_commit = false;
 
 	if (channel->primary_channel != NULL)
 		device = channel->primary_channel->device_obj;
@@ -1154,39 +1187,36 @@ void netvsc_channel_cb(void *context)
 	buffer = get_per_channel_state(channel);
 
 	do {
+		desc = get_next_pkt_raw(channel);
+		if (desc != NULL) {
+			netvsc_process_raw_pkt(device,
+					       channel,
+					       net_device,
+					       ndev,
+					       desc->trans_id,
+					       desc);
+
+			put_pkt_raw(channel, desc);
+			need_to_commit = true;
+			continue;
+		}
+		if (need_to_commit) {
+			need_to_commit = false;
+			commit_rd_index(channel);
+		}
+
 		ret = vmbus_recvpacket_raw(channel, buffer, bufferlen,
 					   &bytes_recvd, &request_id);
 		if (ret == 0) {
 			if (bytes_recvd > 0) {
 				desc = (struct vmpacket_descriptor *)buffer;
-				nvmsg = (struct nvsp_message *)((unsigned long)
-					 desc + (desc->offset8 << 3));
-				switch (desc->type) {
-				case VM_PKT_COMP:
-					netvsc_send_completion(net_device,
-								channel,
-								device, desc);
-					break;
-
-				case VM_PKT_DATA_USING_XFER_PAGES:
-					netvsc_receive(net_device, channel,
-						       device, desc);
-					break;
-
-				case VM_PKT_DATA_INBAND:
-					netvsc_receive_inband(device,
-							      net_device,
-							      nvmsg);
-					break;
-
-				default:
-					netdev_err(ndev,
-						   "unhandled packet type %d, "
-						   "tid %llx len %d\n",
-						   desc->type, request_id,
-						   bytes_recvd);
-					break;
-				}
+				netvsc_process_raw_pkt(device,
+						       channel,
+						       net_device,
+						       ndev,
+						       request_id,
+						       desc);
+
 
 			} else {
 				/*