net: dev: Improve debug statements for adjacency tracking

Adjacency code only has debugs for the insert case. Add debugs for
the remove path and make both consistently worded to make it easier
to follow the insert and removal with reference counts.

In addition, change the BUG to a WARN_ON. A missing adjacency at
removal time is not cause for a panic.
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -5561,6 +5561,9 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,
 
 	if (adj) {
 		adj->ref_nr += 1;
+		pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d\n",
+			 dev->name, adj_dev->name, adj->ref_nr);
+
 		return 0;
 	}
 
@@ -5574,8 +5577,8 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,
 	adj->private = private;
 	dev_hold(adj_dev);
 
-	pr_debug("dev_hold for %s, because of link added from %s to %s\n",
-		 adj_dev->name, dev->name, adj_dev->name);
+	pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d; dev_hold on %s\n",
+		 dev->name, adj_dev->name, adj->ref_nr, adj_dev->name);
 
 	if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list)) {
 		ret = netdev_adjacent_sysfs_add(dev, adj_dev, dev_list);
@@ -5614,17 +5617,22 @@ static void __netdev_adjacent_dev_remove(struct net_device *dev,
 {
 	struct netdev_adjacent *adj;
 
+	pr_debug("Remove adjacency: dev %s adj_dev %s ref_nr %d\n",
+		 dev->name, adj_dev->name, ref_nr);
+
 	adj = __netdev_find_adj(adj_dev, dev_list);
 
 	if (!adj) {
-		pr_err("tried to remove device %s from %s\n",
+		pr_err("Adjacency does not exist for device %s from %s\n",
 		       dev->name, adj_dev->name);
-		BUG();
+		WARN_ON(1);
+		return;
 	}
 
 	if (adj->ref_nr > ref_nr) {
-		pr_debug("%s to %s ref_nr-%d = %d\n", dev->name, adj_dev->name,
-			 ref_nr, adj->ref_nr-ref_nr);
+		pr_debug("adjacency: %s to %s ref_nr - %d = %d\n",
+			 dev->name, adj_dev->name, ref_nr,
+			 adj->ref_nr - ref_nr);
 		adj->ref_nr -= ref_nr;
 		return;
 	}
@@ -5636,7 +5644,7 @@ static void __netdev_adjacent_dev_remove(struct net_device *dev,
 		netdev_adjacent_sysfs_del(dev, adj_dev->name, dev_list);
 
 	list_del_rcu(&adj->list);
-	pr_debug("dev_put for %s, because link removed from %s to %s\n",
+	pr_debug("adjacency: dev_put for %s, because link removed from %s to %s\n",
 		 adj_dev->name, dev->name, adj_dev->name);
 	dev_put(adj_dev);
 	kfree_rcu(adj, rcu);