net: linkwatch: add net device refcount tracker

Add a netdevice_tracker inside struct net_device, to track
the self reference when a device is in lweventlist.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdevice.h

@@ -1950,6 +1950,7 @@ enum netdev_ml_priv_type {
  *			keep a list of interfaces to be deleted.
  *
  *	@dev_addr_shadow:	Copy of @dev_addr to catch direct writes.
+ *	@linkwatch_dev_tracker:	refcount tracker used by linkwatch.
  *
  *	FIXME: cleanup struct net_device such that network protocol info
  *	moves out.
@@ -2280,6 +2281,7 @@ struct net_device {
 	struct bpf_xdp_entity	xdp_state[__MAX_XDP_MODE];
 
 	u8 dev_addr_shadow[MAX_ADDR_LEN];
+	netdevice_tracker	linkwatch_dev_tracker;
 };
 #define to_net_dev(d) container_of(d, struct net_device, dev)
 

net/core/link_watch.c

@@ -109,7 +109,7 @@ static void linkwatch_add_event(struct net_device *dev)
 	spin_lock_irqsave(&lweventlist_lock, flags);
 	if (list_empty(&dev->link_watch_list)) {
 		list_add_tail(&dev->link_watch_list, &lweventlist);
-		dev_hold(dev);
+		dev_hold_track(dev, &dev->linkwatch_dev_tracker, GFP_ATOMIC);
 	}
 	spin_unlock_irqrestore(&lweventlist_lock, flags);
 }
@@ -166,7 +166,7 @@ static void linkwatch_do_dev(struct net_device *dev)
 
 		netdev_state_change(dev);
 	}
-	dev_put(dev);
+	dev_put_track(dev, &dev->linkwatch_dev_tracker);
 }
 
 static void __linkwatch_run_queue(int urgent_only)