mlxsw: spectrum_router: Do not assume RTNL is taken during nexthop init

RTNL is going to be removed from route insertion path, so use
__in_dev_get_rcu() from an RCU read-side critical section instead of
__in_dev_get_rtnl() which assumes RTNL is taken.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -3840,10 +3840,14 @@ static int mlxsw_sp_nexthop4_init(struct mlxsw_sp *mlxsw_sp,
 	if (!dev)
 		return 0;
 
-	in_dev = __in_dev_get_rtnl(dev);
+	rcu_read_lock();
+	in_dev = __in_dev_get_rcu(dev);
 	if (in_dev && IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
-	    fib_nh->fib_nh_flags & RTNH_F_LINKDOWN)
+	    fib_nh->fib_nh_flags & RTNH_F_LINKDOWN) {
+		rcu_read_unlock();
 		return 0;
+	}
+	rcu_read_unlock();
 
 	err = mlxsw_sp_nexthop4_type_init(mlxsw_sp, nh, fib_nh);
 	if (err)