hv_netvsc: rework link status change handling

There are several issues in hv_netvsc driver with regards to link status
change handling:
- RNDIS_STATUS_NETWORK_CHANGE results in calling userspace helper doing
  '/etc/init.d/network restart' and this is inappropriate and broken for
  many reasons.
- link_watch infrastructure only sends one notification per second and
  in case of e.g. paired disconnect/connect events we get only one
  notification with last status. This makes it impossible to handle such
  situations in userspace.

Redo link status changes handling in the following way:
- Create a list of reconfig events in network device context.
- On a reconfig event add it to the list of events and schedule
  netvsc_link_change().
- In netvsc_link_change() ensure 2-second delay between link status
  changes.
- Handle RNDIS_STATUS_NETWORK_CHANGE as a paired disconnect/connect event.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -177,7 +177,6 @@ struct rndis_device {
 
 	enum rndis_device_state state;
 	bool link_state;
-	bool link_change;
 	atomic_t new_req_id;
 
 	spinlock_t request_lock;
@@ -644,11 +643,24 @@ struct netvsc_stats {
 	struct u64_stats_sync syncp;
 };
 
+struct netvsc_reconfig {
+	struct list_head list;
+	u32 event;
+};
+
 /* The context of the netvsc device  */
 struct net_device_context {
 	/* point back to our device context */
 	struct hv_device *device_ctx;
+	/* reconfigure work */
 	struct delayed_work dwork;
+	/* last reconfig time */
+	unsigned long last_reconfig;
+	/* reconfig events */
+	struct list_head reconfig_events;
+	/* list protection */
+	spinlock_t lock;
+
 	struct work_struct work;
 	u32 msg_enable; /* debug level */
 

drivers/net/hyperv/netvsc_drv.c

@@ -42,6 +42,7 @@
 
 
 #define RING_SIZE_MIN 64
+#define LINKCHANGE_INT (2 * HZ)
 static int ring_size = 128;
 module_param(ring_size, int, S_IRUGO);
 MODULE_PARM_DESC(ring_size, "Ring buffer size (# of pages)");
@@ -647,37 +648,33 @@ void netvsc_linkstatus_callback(struct hv_device *device_obj,
 	struct net_device *net;
 	struct net_device_context *ndev_ctx;
 	struct netvsc_device *net_device;
-	struct rndis_device *rdev;
-
-	net_device = hv_get_drvdata(device_obj);
-	rdev = net_device->extension;
+	struct netvsc_reconfig *event;
+	unsigned long flags;
 
-	switch (indicate->status) {
-	case RNDIS_STATUS_MEDIA_CONNECT:
-		rdev->link_state = false;
-		break;
-	case RNDIS_STATUS_MEDIA_DISCONNECT:
-		rdev->link_state = true;
-		break;
-	case RNDIS_STATUS_NETWORK_CHANGE:
-		rdev->link_change = true;
-		break;
-	default:
+	/* Handle link change statuses only */
+	if (indicate->status != RNDIS_STATUS_NETWORK_CHANGE &&
+	    indicate->status != RNDIS_STATUS_MEDIA_CONNECT &&
+	    indicate->status != RNDIS_STATUS_MEDIA_DISCONNECT)
 		return;
-	}
 
+	net_device = hv_get_drvdata(device_obj);
 	net = net_device->ndev;
 
 	if (!net || net->reg_state != NETREG_REGISTERED)
 		return;
 
 	ndev_ctx = netdev_priv(net);
-	if (!rdev->link_state) {
-		schedule_delayed_work(&ndev_ctx->dwork, 0);
-		schedule_delayed_work(&ndev_ctx->dwork, msecs_to_jiffies(20));
-	} else {
-		schedule_delayed_work(&ndev_ctx->dwork, 0);
-	}
+
+	event = kzalloc(sizeof(*event), GFP_ATOMIC);
+	if (!event)
+		return;
+	event->event = indicate->status;
+
+	spin_lock_irqsave(&ndev_ctx->lock, flags);
+	list_add_tail(&event->list, &ndev_ctx->reconfig_events);
+	spin_unlock_irqrestore(&ndev_ctx->lock, flags);
+
+	schedule_delayed_work(&ndev_ctx->dwork, 0);
 }
 
 /*
@@ -1009,12 +1006,9 @@ static const struct net_device_ops device_ops = {
 };
 
 /*
- * Send GARP packet to network peers after migrations.
- * After Quick Migration, the network is not immediately operational in the
- * current context when receiving RNDIS_STATUS_MEDIA_CONNECT event. So, add
- * another netif_notify_peers() into a delayed work, otherwise GARP packet
- * will not be sent after quick migration, and cause network disconnection.
- * Also, we update the carrier status here.
+ * Handle link status changes. For RNDIS_STATUS_NETWORK_CHANGE emulate link
+ * down/up sequence. In case of RNDIS_STATUS_MEDIA_CONNECT when carrier is
+ * present send GARP packet to network peers with netif_notify_peers().
  */
 static void netvsc_link_change(struct work_struct *w)
 {
@@ -1022,36 +1016,89 @@ static void netvsc_link_change(struct work_struct *w)
 	struct net_device *net;
 	struct netvsc_device *net_device;
 	struct rndis_device *rdev;
-	bool notify, refresh = false;
-	char *argv[] = { "/etc/init.d/network", "restart", NULL };
-	char *envp[] = { "HOME=/", "PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL };
-
-	rtnl_lock();
+	struct netvsc_reconfig *event = NULL;
+	bool notify = false, reschedule = false;
+	unsigned long flags, next_reconfig, delay;
 
 	ndev_ctx = container_of(w, struct net_device_context, dwork.work);
 	net_device = hv_get_drvdata(ndev_ctx->device_ctx);
 	rdev = net_device->extension;
 	net = net_device->ndev;
 
-	if (rdev->link_state) {
-		netif_carrier_off(net);
-		notify = false;
-	} else {
-		netif_carrier_on(net);
-		notify = true;
-		if (rdev->link_change) {
-			rdev->link_change = false;
-			refresh = true;
+	next_reconfig = ndev_ctx->last_reconfig + LINKCHANGE_INT;
+	if (time_is_after_jiffies(next_reconfig)) {
+		/* link_watch only sends one notification with current state
+		 * per second, avoid doing reconfig more frequently. Handle
+		 * wrap around.
+		 */
+		delay = next_reconfig - jiffies;
+		delay = delay < LINKCHANGE_INT ? delay : LINKCHANGE_INT;
+		schedule_delayed_work(&ndev_ctx->dwork, delay);
+		return;
+	}
+	ndev_ctx->last_reconfig = jiffies;
+
+	spin_lock_irqsave(&ndev_ctx->lock, flags);
+	if (!list_empty(&ndev_ctx->reconfig_events)) {
+		event = list_first_entry(&ndev_ctx->reconfig_events,
+					 struct netvsc_reconfig, list);
+		list_del(&event->list);
+		reschedule = !list_empty(&ndev_ctx->reconfig_events);
+	}
+	spin_unlock_irqrestore(&ndev_ctx->lock, flags);
+
+	if (!event)
+		return;
+
+	rtnl_lock();
+
+	switch (event->event) {
+		/* Only the following events are possible due to the check in
+		 * netvsc_linkstatus_callback()
+		 */
+	case RNDIS_STATUS_MEDIA_CONNECT:
+		if (rdev->link_state) {
+			rdev->link_state = false;
+			netif_carrier_on(net);
+			netif_tx_wake_all_queues(net);
+		} else {
+			notify = true;
+		}
+		kfree(event);
+		break;
+	case RNDIS_STATUS_MEDIA_DISCONNECT:
+		if (!rdev->link_state) {
+			rdev->link_state = true;
+			netif_carrier_off(net);
+			netif_tx_stop_all_queues(net);
+		}
+		kfree(event);
+		break;
+	case RNDIS_STATUS_NETWORK_CHANGE:
+		/* Only makes sense if carrier is present */
+		if (!rdev->link_state) {
+			rdev->link_state = true;
+			netif_carrier_off(net);
+			netif_tx_stop_all_queues(net);
+			event->event = RNDIS_STATUS_MEDIA_CONNECT;
+			spin_lock_irqsave(&ndev_ctx->lock, flags);
+			list_add_tail(&event->list, &ndev_ctx->reconfig_events);
+			spin_unlock_irqrestore(&ndev_ctx->lock, flags);
+			reschedule = true;
 		}
+		break;
 	}
 
 	rtnl_unlock();
 
-	if (refresh)
-		call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
-
 	if (notify)
 		netdev_notify_peers(net);
+
+	/* link_watch only sends one notification with current state per
+	 * second, handle next reconfig event in 2 seconds.
+	 */
+	if (reschedule)
+		schedule_delayed_work(&ndev_ctx->dwork, LINKCHANGE_INT);
 }
 
 static void netvsc_free_netdev(struct net_device *netdev)
@@ -1106,6 +1153,9 @@ static int netvsc_probe(struct hv_device *dev,
 	INIT_DELAYED_WORK(&net_device_ctx->dwork, netvsc_link_change);
 	INIT_WORK(&net_device_ctx->work, do_set_multicast);
 
+	spin_lock_init(&net_device_ctx->lock);
+	INIT_LIST_HEAD(&net_device_ctx->reconfig_events);
+
 	net->netdev_ops = &device_ops;
 
 	net->hw_features = NETIF_F_RXCSUM | NETIF_F_SG | NETIF_F_IP_CSUM |
@@ -1145,8 +1195,6 @@ static int netvsc_probe(struct hv_device *dev,
 		pr_err("Unable to register netdev.\n");
 		rndis_filter_device_remove(dev);
 		netvsc_free_netdev(net);
-	} else {
-		schedule_delayed_work(&net_device_ctx->dwork, 0);
 	}
 
 	return ret;