[PATCH net-next] hv_netvsc: Add error handling while switching data path

@@ -269,7 +269,7 @@ int rndis_filter_receive(struct net_device *ndev,
 int rndis_filter_set_device_mac(struct netvsc_device *ndev,
 				const char *mac);
 
-void netvsc_switch_datapath(struct net_device *nv_dev, bool vf);
+int netvsc_switch_datapath(struct net_device *nv_dev, bool vf);
 
 #define NVSP_INVALID_PROTOCOL_VERSION	((u32)0xFFFFFFFF)
 

@@ -1718,4 +1718,8 @@ struct rndis_message {
 #define TRANSPORT_INFO_IPV6_TCP 0x10
 #define TRANSPORT_INFO_IPV6_UDP 0x20
 
+#define RETRY_US_LO	5000
+#define RETRY_US_HI	10000
+#define RETRY_MAX	2000	/* >10 sec */
+
 #endif /* _HYPERV_NET_H */

@@ -31,12 +31,13 @@
  * Switch the data path from the synthetic interface to the VF
  * interface.
  */
-void netvsc_switch_datapath(struct net_device *ndev, bool vf)
+int netvsc_switch_datapath(struct net_device *ndev, bool vf)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(ndev);
 	struct hv_device *dev = net_device_ctx->device_ctx;
 	struct netvsc_device *nv_dev = rtnl_dereference(net_device_ctx->nvdev);
 	struct nvsp_message *init_pkt = &nv_dev->channel_init_pkt;
+	int ret, retry = 0;
 
 	/* Block sending traffic to VF if it's about to be gone */
 	if (!vf)

@@ -51,15 +52,41 @@ void netvsc_switch_datapath(struct net_device *ndev, bool vf)
 		init_pkt->msg.v4_msg.active_dp.active_datapath =
 			NVSP_DATAPATH_SYNTHETIC;
 
+again:
 	trace_nvsp_send(ndev, init_pkt);
 
-	vmbus_sendpacket(dev->channel, init_pkt,
+	ret = vmbus_sendpacket(dev->channel, init_pkt,
 			       sizeof(struct nvsp_message),
-			       (unsigned long)init_pkt,
-			       VM_PKT_DATA_INBAND,
+			       (unsigned long)init_pkt, VM_PKT_DATA_INBAND,
 			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+
+	/* If failed to switch to/from VF, let data_path_is_vf stay false,
+	 * so we use synthetic path to send data.
+	 */
+	if (ret) {
+		if (ret != -EAGAIN) {
+			netdev_err(ndev,
+				   "Unable to send sw datapath msg, err: %d\n",
+				   ret);
+			return ret;
+		}
+
+		if (retry++ < RETRY_MAX) {
+			usleep_range(RETRY_US_LO, RETRY_US_HI);
+			goto again;
+		} else {
+			netdev_err(
+				ndev,
+				"Retry failed to send sw datapath msg, err: %d\n",
+				ret);
+			return ret;
+		}
+	}
+
 	wait_for_completion(&nv_dev->channel_init_wait);
 	net_device_ctx->data_path_is_vf = vf;
+
+	return 0;
 }
 
 /* Worker to setup sub channels on initial setup

@@ -38,9 +38,6 @@
 #include "hyperv_net.h"
 
 #define RING_SIZE_MIN	64
-#define RETRY_US_LO	5000
-#define RETRY_US_HI	10000
-#define RETRY_MAX	2000	/* >10 sec */
 
 #define LINKCHANGE_INT (2 * HZ)
 #define VF_TAKEOVER_INT (HZ / 10)

@@ -2402,6 +2399,7 @@ static int netvsc_vf_changed(struct net_device *vf_netdev, unsigned long event)
 	struct netvsc_device *netvsc_dev;
 	struct net_device *ndev;
 	bool vf_is_up = false;
+	int ret;
 
 	if (event != NETDEV_GOING_DOWN)
 		vf_is_up = netif_running(vf_netdev);

@@ -2418,9 +2416,17 @@ static int netvsc_vf_changed(struct net_device *vf_netdev, unsigned long event)
 	if (net_device_ctx->data_path_is_vf == vf_is_up)
 		return NOTIFY_OK;
 
-	netvsc_switch_datapath(ndev, vf_is_up);
-	netdev_info(ndev, "Data path switched %s VF: %s\n",
-		    vf_is_up ? "to" : "from", vf_netdev->name);
+	ret = netvsc_switch_datapath(ndev, vf_is_up);
+
+	if (ret) {
+		netdev_err(ndev,
+			   "Data path failed to switch %s VF: %s, err: %d\n",
+			   vf_is_up ? "to" : "from", vf_netdev->name, ret);
+		return NOTIFY_DONE;
+	} else {
+		netdev_info(ndev, "Data path switched %s VF: %s\n",
+			    vf_is_up ? "to" : "from", vf_netdev->name);
+	}
 
 	return NOTIFY_OK;
 }