mlxsw: spectrum: Relax sanity checks during enslavement

Since commit 25cc72a3 ("mlxsw: spectrum: Forbid linking to devices that
have uppers") the driver forbids enslavement to netdevs that already
have uppers of their own, as this can result in various ordering
problems.

This requirement proved to be too strict for some users who need to be
able to enslave ports to a bridge that already has uppers. In this case,
we can allow the enslavement if the bridge is already known to us, as
any configuration performed on top of the bridge was already reflected
to the device.

Fixes: 25cc72a3 ("mlxsw: spectrum: Forbid linking to devices that have uppers")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Alexander Petrovskiy <alexpe@mellanox.com>
Tested-by: Alexander Petrovskiy <alexpe@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -4376,7 +4376,10 @@ static int mlxsw_sp_netdevice_port_upper_event(struct net_device *lower_dev,
 		}
 		if (!info->linking)
 			break;
-		if (netdev_has_any_upper_dev(upper_dev)) {
+		if (netdev_has_any_upper_dev(upper_dev) &&
+		    (!netif_is_bridge_master(upper_dev) ||
+		     !mlxsw_sp_bridge_device_is_offloaded(mlxsw_sp,
+							  upper_dev))) {
 			NL_SET_ERR_MSG(extack,
 				       "spectrum: Enslaving a port to a device that already has an upper device is not supported");
 			return -EINVAL;
@@ -4504,6 +4507,7 @@ static int mlxsw_sp_netdevice_port_vlan_event(struct net_device *vlan_dev,
 					      u16 vid)
 {
 	struct mlxsw_sp_port *mlxsw_sp_port = netdev_priv(dev);
+	struct mlxsw_sp *mlxsw_sp = mlxsw_sp_port->mlxsw_sp;
 	struct netdev_notifier_changeupper_info *info = ptr;
 	struct netlink_ext_ack *extack;
 	struct net_device *upper_dev;
@@ -4520,7 +4524,10 @@ static int mlxsw_sp_netdevice_port_vlan_event(struct net_device *vlan_dev,
 		}
 		if (!info->linking)
 			break;
-		if (netdev_has_any_upper_dev(upper_dev)) {
+		if (netdev_has_any_upper_dev(upper_dev) &&
+		    (!netif_is_bridge_master(upper_dev) ||
+		     !mlxsw_sp_bridge_device_is_offloaded(mlxsw_sp,
+							  upper_dev))) {
 			NL_SET_ERR_MSG(extack, "spectrum: Enslaving a port to a device that already has an upper device is not supported");
 			return -EINVAL;
 		}

drivers/net/ethernet/mellanox/mlxsw/spectrum.h

@@ -365,6 +365,8 @@ int mlxsw_sp_port_bridge_join(struct mlxsw_sp_port *mlxsw_sp_port,
 void mlxsw_sp_port_bridge_leave(struct mlxsw_sp_port *mlxsw_sp_port,
 				struct net_device *brport_dev,
 				struct net_device *br_dev);
+bool mlxsw_sp_bridge_device_is_offloaded(const struct mlxsw_sp *mlxsw_sp,
+					 const struct net_device *br_dev);
 
 /* spectrum.c */
 int mlxsw_sp_port_ets_set(struct mlxsw_sp_port *mlxsw_sp_port,

drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c

@@ -152,6 +152,12 @@ mlxsw_sp_bridge_device_find(const struct mlxsw_sp_bridge *bridge,
 	return NULL;
 }
 
+bool mlxsw_sp_bridge_device_is_offloaded(const struct mlxsw_sp *mlxsw_sp,
+					 const struct net_device *br_dev)
+{
+	return !!mlxsw_sp_bridge_device_find(mlxsw_sp->bridge, br_dev);
+}
+
 static struct mlxsw_sp_bridge_device *
 mlxsw_sp_bridge_device_create(struct mlxsw_sp_bridge *bridge,
 			      struct net_device *br_dev)