net: bridge: Add support for calling FDB external learning under rcu

This is done as a preparation to moving the switchdev notifier chain
to be atomic. The FDB external learning should be called under rtnl
or rcu.

Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br.c

@@ -121,7 +121,7 @@ static struct notifier_block br_device_notifier = {
 	.notifier_call = br_device_event
 };
 
-/* called with RTNL */
+/* called with RTNL or RCU */
 static int br_switchdev_event(struct notifier_block *unused,
 			      unsigned long event, void *ptr)
 {
@@ -131,7 +131,7 @@ static int br_switchdev_event(struct notifier_block *unused,
 	struct switchdev_notifier_fdb_info *fdb_info;
 	int err = NOTIFY_DONE;
 
-	p = br_port_get_rtnl(dev);
+	p = br_port_get_rtnl_rcu(dev);
 	if (!p)
 		goto out;
 

net/bridge/br_fdb.c

@@ -1075,7 +1075,6 @@ int br_fdb_external_learn_add(struct net_bridge *br, struct net_bridge_port *p,
 	struct net_bridge_fdb_entry *fdb;
 	int err = 0;
 
-	ASSERT_RTNL();
 	spin_lock_bh(&br->hash_lock);
 
 	head = &br->hash[br_mac_hash(addr, vid)];
@@ -1110,7 +1109,6 @@ int br_fdb_external_learn_del(struct net_bridge *br, struct net_bridge_port *p,
 	struct net_bridge_fdb_entry *fdb;
 	int err = 0;
 
-	ASSERT_RTNL();
 	spin_lock_bh(&br->hash_lock);
 
 	fdb = br_fdb_find(br, addr, vid);

net/bridge/br_private.h

@@ -284,6 +284,12 @@ static inline struct net_bridge_port *br_port_get_rtnl(const struct net_device *
 		rtnl_dereference(dev->rx_handler_data) : NULL;
 }
 
+static inline struct net_bridge_port *br_port_get_rtnl_rcu(const struct net_device *dev)
+{
+	return br_port_exists(dev) ?
+		rcu_dereference_rtnl(dev->rx_handler_data) : NULL;
+}
+
 struct net_bridge {
 	spinlock_t			lock;
 	spinlock_t			hash_lock;