drop_monitor: add net device refcount tracker

We want to track all dev_hold()/dev_put() to ease leak hunting.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/devlink.h

@@ -664,13 +664,17 @@ struct devlink_health_reporter_ops {
  * @trap_name: Trap name.
  * @trap_group_name: Trap group name.
  * @input_dev: Input netdevice.
+ * @dev_tracker: refcount tracker for @input_dev.
  * @fa_cookie: Flow action user cookie.
  * @trap_type: Trap type.
  */
 struct devlink_trap_metadata {
 	const char *trap_name;
 	const char *trap_group_name;
+
 	struct net_device *input_dev;
+	netdevice_tracker dev_tracker;
+
 	const struct flow_action_cookie *fa_cookie;
 	enum devlink_trap_type trap_type;
 };

net/core/drop_monitor.c

@@ -850,7 +850,7 @@ net_dm_hw_metadata_copy(const struct devlink_trap_metadata *metadata)
 	}
 
 	hw_metadata->input_dev = metadata->input_dev;
-	dev_hold(hw_metadata->input_dev);
+	dev_hold_track(hw_metadata->input_dev, &hw_metadata->dev_tracker, GFP_ATOMIC);
 
 	return hw_metadata;
 
@@ -864,9 +864,9 @@ net_dm_hw_metadata_copy(const struct devlink_trap_metadata *metadata)
 }
 
 static void
-net_dm_hw_metadata_free(const struct devlink_trap_metadata *hw_metadata)
+net_dm_hw_metadata_free(struct devlink_trap_metadata *hw_metadata)
 {
-	dev_put(hw_metadata->input_dev);
+	dev_put_track(hw_metadata->input_dev, &hw_metadata->dev_tracker);
 	kfree(hw_metadata->fa_cookie);
 	kfree(hw_metadata->trap_name);
 	kfree(hw_metadata->trap_group_name);