batman-adv: create hardif only for netdevs that are part of a mesh

batman-adv is using netdev notifiers to create a hard_iface struct for
every Ethernet-like netdev in the system. These hardifs are tracked in a
global linked list, which results in a few performance issues:

Lookups in this list are O(n) in the total number of netdevs. As a
hardif is looked up when a netdev is removed, this also takes O(n) in
the number of netdevs, and removing n netdevs may take O(n^2). This
slowdown will always happen when the batman-adv module is loaded, no
mesh needs to be active.

With the hardif being referenced as iflink private data, the global list
is only needed for hardifs that are *not* part of a mesh (that is, the
hardif is unused). To prepare for removing the global list, only create
a hardif struct when an interface is added to a mesh and destroy it on
removal.

As adding/removing and enabling/disabling a hardif become one and the
same, batadv_hardif_add_interface() is merged into
batadv_hardif_enable_interface(), and batadv_hardif_remove_interface()
can be dropped altogether.

Signed-off-by: Nora Schiffer <neocturne@universe-factory.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

3 files changed, 44 insertions, 91 deletions

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 03d01c20a954..9c9a892d22c6 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -723,33 +723,58 @@ batadv_hardif_deactivate_interface(struct batadv_hard_iface *hard_iface)
 }
 
 /**
- * batadv_hardif_enable_interface() - Enslave hard interface to mesh interface
- * @hard_iface: hard interface to add to mesh interface
+ * batadv_hardif_enable_interface() - Enslave interface to mesh interface
+ * @net_dev: netdev struct of the interface to add to mesh interface
  * @mesh_iface: netdev struct of the mesh interface
  *
  * Return: 0 on success or negative error number in case of failure
  */
-int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
+int batadv_hardif_enable_interface(struct net_device *net_dev,
 				   struct net_device *mesh_iface)
 {
 	struct batadv_priv *bat_priv;
 	__be16 ethertype = htons(ETH_P_BATMAN);
 	int max_header_len = batadv_max_header_len();
+	struct batadv_hard_iface *hard_iface;
 	unsigned int required_mtu;
 	unsigned int hardif_mtu;
 	bool fragmentation;
 	int ret;
 
-	hardif_mtu = READ_ONCE(hard_iface->net_dev->mtu);
+	ASSERT_RTNL();
+
+	if (!batadv_is_valid_iface(net_dev))
+		return -EINVAL;
+
+	hardif_mtu = READ_ONCE(net_dev->mtu);
 	required_mtu = READ_ONCE(mesh_iface->mtu) + max_header_len;
 
 	if (hardif_mtu < ETH_MIN_MTU + max_header_len)
 		return -EINVAL;
 
-	if (hard_iface->if_status != BATADV_IF_NOT_IN_USE)
-		goto out;
+	hard_iface = kzalloc_obj(*hard_iface, GFP_ATOMIC);
+	if (!hard_iface)
+		return -ENOMEM;
+
+	netdev_hold(net_dev, &hard_iface->dev_tracker, GFP_ATOMIC);
+	hard_iface->net_dev = net_dev;
+
+	hard_iface->if_status = BATADV_IF_INACTIVE;
+
+	INIT_LIST_HEAD(&hard_iface->list);
+	INIT_HLIST_HEAD(&hard_iface->neigh_list);
 
-	kref_get(&hard_iface->refcount);
+	mutex_init(&hard_iface->bat_iv.ogm_buff_mutex);
+	spin_lock_init(&hard_iface->neigh_list_lock);
+	kref_init(&hard_iface->refcount);
+
+	hard_iface->num_bcasts = BATADV_NUM_BCASTS_DEFAULT;
+	if (batadv_is_wifi_hardif(hard_iface))
+		hard_iface->num_bcasts = BATADV_NUM_BCASTS_WIRELESS;
+
+	WRITE_ONCE(hard_iface->hop_penalty, 0);
+
+	batadv_v_hardif_init(hard_iface);
 
 	netdev_hold(mesh_iface, &hard_iface->meshif_dev_tracker, GFP_ATOMIC);
 	hard_iface->mesh_iface = mesh_iface;
@@ -764,9 +789,6 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
 	if (ret < 0)
 		goto err_upper;
 
-	hard_iface->if_status = BATADV_IF_INACTIVE;
-
-	kref_get(&hard_iface->refcount);
 	hard_iface->batman_adv_ptype.type = ethertype;
 	hard_iface->batman_adv_ptype.func = batadv_batman_skb_recv;
 	hard_iface->batman_adv_ptype.dev = hard_iface->net_dev;
@@ -802,7 +824,9 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
 	if (bat_priv->algo_ops->iface.enabled)
 		bat_priv->algo_ops->iface.enabled(hard_iface);
 
-out:
+	list_add_tail_rcu(&hard_iface->list, &batadv_hardif_list);
+	batadv_hardif_generation++;
+
 	return 0;
 
 err_upper:
@@ -823,15 +847,19 @@ void batadv_hardif_disable_interface(struct batadv_hard_iface *hard_iface)
 	struct batadv_priv *bat_priv = netdev_priv(hard_iface->mesh_iface);
 	struct batadv_hard_iface *primary_if = NULL;
 
+	ASSERT_RTNL();
+
 	batadv_hardif_deactivate_interface(hard_iface);
 
 	if (hard_iface->if_status != BATADV_IF_INACTIVE)
 		goto out;
 
+	list_del_rcu(&hard_iface->list);
+	batadv_hardif_generation++;
+
 	batadv_info(hard_iface->mesh_iface, "Removing interface: %s\n",
 		    hard_iface->net_dev->name);
 	dev_remove_pack(&hard_iface->batman_adv_ptype);
-	batadv_hardif_put(hard_iface);
 
 	primary_if = batadv_primary_if_get_selected(bat_priv);
 	if (hard_iface == primary_if) {
@@ -844,7 +872,7 @@ void batadv_hardif_disable_interface(struct batadv_hard_iface *hard_iface)
 	}
 
 	bat_priv->algo_ops->iface.disable(hard_iface);
-	hard_iface->if_status = BATADV_IF_NOT_IN_USE;
+	hard_iface->if_status = BATADV_IF_TO_BE_REMOVED;
 
 	/* delete all references to this hard_iface */
 	batadv_purge_orig_ref(bat_priv);
@@ -865,63 +893,6 @@ out:
 	batadv_hardif_put(primary_if);
 }
 
-static struct batadv_hard_iface *
-batadv_hardif_add_interface(struct net_device *net_dev)
-{
-	struct batadv_hard_iface *hard_iface;
-
-	ASSERT_RTNL();
-
-	if (!batadv_is_valid_iface(net_dev))
-		return NULL;
-
-	hard_iface = kzalloc_obj(*hard_iface, GFP_ATOMIC);
-	if (!hard_iface)
-		return NULL;
-
-	netdev_hold(net_dev, &hard_iface->dev_tracker, GFP_ATOMIC);
-	hard_iface->net_dev = net_dev;
-
-	hard_iface->mesh_iface = NULL;
-	hard_iface->if_status = BATADV_IF_NOT_IN_USE;
-
-	INIT_LIST_HEAD(&hard_iface->list);
-	INIT_HLIST_HEAD(&hard_iface->neigh_list);
-
-	mutex_init(&hard_iface->bat_iv.ogm_buff_mutex);
-	spin_lock_init(&hard_iface->neigh_list_lock);
-	kref_init(&hard_iface->refcount);
-
-	hard_iface->num_bcasts = BATADV_NUM_BCASTS_DEFAULT;
-	if (batadv_is_wifi_hardif(hard_iface))
-		hard_iface->num_bcasts = BATADV_NUM_BCASTS_WIRELESS;
-
-	WRITE_ONCE(hard_iface->hop_penalty, 0);
-
-	batadv_v_hardif_init(hard_iface);
-
-	kref_get(&hard_iface->refcount);
-	list_add_tail_rcu(&hard_iface->list, &batadv_hardif_list);
-	batadv_hardif_generation++;
-
-	return hard_iface;
-}
-
-static void batadv_hardif_remove_interface(struct batadv_hard_iface *hard_iface)
-{
-	ASSERT_RTNL();
-
-	/* first deactivate interface */
-	if (hard_iface->if_status != BATADV_IF_NOT_IN_USE)
-		batadv_hardif_disable_interface(hard_iface);
-
-	if (hard_iface->if_status != BATADV_IF_NOT_IN_USE)
-		return;
-
-	hard_iface->if_status = BATADV_IF_TO_BE_REMOVED;
-	batadv_hardif_put(hard_iface);
-}
-
 /**
  * batadv_hard_if_event_meshif() - Handle events for mesh interfaces
  * @event: NETDEV_* event to handle
@@ -1082,10 +1053,6 @@ static int batadv_hard_if_event(struct notifier_block *this,
 	batadv_wifi_net_device_event(event, net_dev);
 
 	hard_iface = batadv_hardif_get_by_netdev(net_dev);
-	if (!hard_iface && (event == NETDEV_REGISTER ||
-			    event == NETDEV_POST_TYPE_CHANGE))
-		hard_iface = batadv_hardif_add_interface(net_dev);
-
 	if (!hard_iface)
 		goto out;
 
@@ -1099,10 +1066,7 @@ static int batadv_hard_if_event(struct notifier_block *this,
 		break;
 	case NETDEV_UNREGISTER:
 	case NETDEV_PRE_TYPE_CHANGE:
-		list_del_rcu(&hard_iface->list);
-		batadv_hardif_generation++;
-
-		batadv_hardif_remove_interface(hard_iface);
+		batadv_hardif_disable_interface(hard_iface);
 		break;
 	case NETDEV_CHANGEMTU:
 		if (hard_iface->mesh_iface)
diff --git a/net/batman-adv/hard-interface.h b/net/batman-adv/hard-interface.h
index af31696c3978..6d72dbdd5c20 100644
--- a/net/batman-adv/hard-interface.h
+++ b/net/batman-adv/hard-interface.h
@@ -75,7 +75,7 @@ u32 batadv_hardif_get_wifi_flags(struct batadv_hard_iface *hard_iface);
 bool batadv_is_wifi_hardif(struct batadv_hard_iface *hard_iface);
 struct batadv_hard_iface*
 batadv_hardif_get_by_netdev(const struct net_device *net_dev);
-int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
+int batadv_hardif_enable_interface(struct net_device *net_dev,
 				   struct net_device *mesh_iface);
 void batadv_hardif_disable_interface(struct batadv_hard_iface *hard_iface);
 int batadv_hardif_min_mtu(struct net_device *mesh_iface);
diff --git a/net/batman-adv/mesh-interface.c b/net/batman-adv/mesh-interface.c
index 44026810b99c..a37368c1f5b5 100644
--- a/net/batman-adv/mesh-interface.c
+++ b/net/batman-adv/mesh-interface.c
@@ -836,18 +836,7 @@ static int batadv_meshif_slave_add(struct net_device *dev,
 				   struct net_device *slave_dev,
 				   struct netlink_ext_ack *extack)
 {
-	struct batadv_hard_iface *hard_iface;
-	int ret = -EINVAL;
-
-	hard_iface = batadv_hardif_get_by_netdev(slave_dev);
-	if (!hard_iface || hard_iface->mesh_iface)
-		goto out;
-
-	ret = batadv_hardif_enable_interface(hard_iface, dev);
-
-out:
-	batadv_hardif_put(hard_iface);
-	return ret;
+	return batadv_hardif_enable_interface(slave_dev, dev);
 }
 
 /**