hv_netvsc: remove VF in flight counters

BugLink: http://bugs.launchpad.net/bugs/1650059

Since VF reference is now protected by RCU, no longer need the VF usage
counter and can use device flags to see whether to inject or not.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 9cbcc428)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/net/hyperv/hyperv_net.h

@@ -696,8 +696,7 @@ struct net_device_context {
 
 	/* State to manage the associated VF interface. */
 	struct net_device __rcu *vf_netdev;
-	bool vf_inject;
-	atomic_t vf_use_cnt;
+
 	/* 1: allocated, serial number is valid. 0: not allocated */
 	u32 vf_alloc;
 	/* Serial number of the VF to team with */

drivers/net/hyperv/netvsc_drv.c

@@ -676,50 +676,20 @@ int netvsc_recv_callback(struct hv_device *device_obj,
 	struct net_device *vf_netdev;
 	struct sk_buff *skb;
 	struct netvsc_stats *rx_stats;
-	u32 bytes_recvd = packet->total_data_buflen;
-	int ret = 0;
 
-	if (!net || net->reg_state != NETREG_REGISTERED)
+	if (net->reg_state != NETREG_REGISTERED)
 		return NVSP_STAT_FAIL;
 
-	vf_netdev = rcu_dereference(net_device_ctx->vf_netdev);
-	if (vf_netdev) {
-		struct sk_buff *vf_skb;
-
-		atomic_inc(&net_device_ctx->vf_use_cnt);
-		if (!net_device_ctx->vf_inject) {
-			/*
-			 * We raced; just move on.
-			 */
-			atomic_dec(&net_device_ctx->vf_use_cnt);
-			goto vf_injection_done;
-		}
-
 	/*
-		 * Inject this packet into the VF inerface.
-		 * On Hyper-V, multicast and brodcast packets
-		 * are only delivered on the synthetic interface
-		 * (after subjecting these to policy filters on
-		 * the host). Deliver these via the VF interface
-		 * in the guest.
+	 * If necessary, inject this packet into the VF interface.
+	 * On Hyper-V, multicast and brodcast packets are only delivered
+	 * to the synthetic interface (after subjecting these to
+	 * policy filters on the host). Deliver these via the VF
+	 * interface in the guest.
 	 */
-		vf_skb = netvsc_alloc_recv_skb(vf_netdev,
-					       packet, csum_info, *data,
-					       vlan_tci);
-		if (vf_skb != NULL) {
-			++vf_netdev->stats.rx_packets;
-			vf_netdev->stats.rx_bytes += bytes_recvd;
-			netif_receive_skb(vf_skb);
-		} else {
-			++net->stats.rx_dropped;
-			ret = NVSP_STAT_FAIL;
-		}
-		atomic_dec(&net_device_ctx->vf_use_cnt);
-		return ret;
-	}
-
-vf_injection_done:
-	rx_stats = this_cpu_ptr(net_device_ctx->rx_stats);
+	vf_netdev = rcu_dereference(net_device_ctx->vf_netdev);
+	if (vf_netdev && (vf_netdev->flags & IFF_UP))
+		net = vf_netdev;
 
 	/* Allocate a skb - TODO direct I/O to pages? */
 	skb = netvsc_alloc_recv_skb(net, packet, csum_info, *data, vlan_tci);
@@ -727,9 +697,17 @@ int netvsc_recv_callback(struct hv_device *device_obj,
 		++net->stats.rx_dropped;
 		return NVSP_STAT_FAIL;
 	}
-	skb_record_rx_queue(skb, channel->
-			    offermsg.offer.sub_channel_index);
 
+	if (net != vf_netdev)
+		skb_record_rx_queue(skb,
+				    channel->offermsg.offer.sub_channel_index);
+
+	/*
+	 * Even if injecting the packet, record the statistics
+	 * on the synthetic device because modifying the VF device
+	 * statistics will not work correctly.
+	 */
+	rx_stats = this_cpu_ptr(net_device_ctx->rx_stats);
 	u64_stats_update_begin(&rx_stats->syncp);
 	rx_stats->packets++;
 	rx_stats->bytes += packet->total_data_buflen;
@@ -1298,20 +1276,6 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
 	return NOTIFY_OK;
 }
 
-static void netvsc_inject_enable(struct net_device_context *net_device_ctx)
-{
-	net_device_ctx->vf_inject = true;
-}
-
-static void netvsc_inject_disable(struct net_device_context *net_device_ctx)
-{
-	net_device_ctx->vf_inject = false;
-
-	/* Wait for currently active users to drain out. */
-	while (atomic_read(&net_device_ctx->vf_use_cnt) != 0)
-		udelay(50);
-}
-
 static int netvsc_vf_up(struct net_device *vf_netdev)
 {
 	struct net_device *ndev;
@@ -1326,7 +1290,6 @@ static int netvsc_vf_up(struct net_device *vf_netdev)
 	netvsc_dev = net_device_ctx->nvdev;
 
 	netdev_info(ndev, "VF up: %s\n", vf_netdev->name);
-	netvsc_inject_enable(net_device_ctx);
 
 	/*
 	 * Open the device before switching data path.
@@ -1361,7 +1324,6 @@ static int netvsc_vf_down(struct net_device *vf_netdev)
 	netvsc_dev = net_device_ctx->nvdev;
 
 	netdev_info(ndev, "VF down: %s\n", vf_netdev->name);
-	netvsc_inject_disable(net_device_ctx);
 	netvsc_switch_datapath(ndev, false);
 	netdev_info(ndev, "Data path switched from VF: %s\n", vf_netdev->name);
 	rndis_filter_close(netvsc_dev);
@@ -1387,7 +1349,6 @@ static int netvsc_unregister_vf(struct net_device *vf_netdev)
 	netvsc_dev = net_device_ctx->nvdev;
 
 	netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name);
-	netvsc_inject_disable(net_device_ctx);
 
 	RCU_INIT_POINTER(net_device_ctx->vf_netdev, NULL);
 	dev_put(vf_netdev);
@@ -1442,8 +1403,6 @@ static int netvsc_probe(struct hv_device *dev,
 	spin_lock_init(&net_device_ctx->lock);
 	INIT_LIST_HEAD(&net_device_ctx->reconfig_events);
 
-	atomic_set(&net_device_ctx->vf_use_cnt, 0);
-
 	net->netdev_ops = &device_ops;
 
 	net->hw_features = NETVSC_HW_FEATURES;