mlxsw: spectrum_router: Use the nodes list as indication for empty FIB

Currently, each FIB (IPv4 / IPv6) in a virtual router holds a prefix
usage that is used to choose a matching LPM tree, but also to check if
the FIB is empty, so that the LPM tree could be unbound.

Next patches will remove the reliance on the per-FIB prefix usage for
LPM tree matching. Keeping it only to check if the FIB is empty is a
waste, since we can use the nodes ({Prefix, Length}) list instead.
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -349,14 +349,6 @@ mlxsw_sp_prefix_usage_eq(struct mlxsw_sp_prefix_usage *prefix_usage1,
 	return !memcmp(prefix_usage1, prefix_usage2, sizeof(*prefix_usage1));
 }
 
-static bool
-mlxsw_sp_prefix_usage_none(struct mlxsw_sp_prefix_usage *prefix_usage)
-{
-	struct mlxsw_sp_prefix_usage prefix_usage_none = {{ 0 } };
-
-	return mlxsw_sp_prefix_usage_eq(prefix_usage, &prefix_usage_none);
-}
-
 static void
 mlxsw_sp_prefix_usage_cpy(struct mlxsw_sp_prefix_usage *prefix_usage1,
 			  struct mlxsw_sp_prefix_usage *prefix_usage2)
@@ -4240,8 +4232,11 @@ static int mlxsw_sp_fib_lpm_tree_link(struct mlxsw_sp *mlxsw_sp,
 static void mlxsw_sp_fib_lpm_tree_unlink(struct mlxsw_sp *mlxsw_sp,
 					 struct mlxsw_sp_fib *fib)
 {
-	if (!mlxsw_sp_prefix_usage_none(&fib->prefix_usage))
+	if (!list_is_singular(&fib->node_list))
 		return;
+	/* Last node is being unlinked from the FIB. Unbind the
+	 * tree and drop the reference.
+	 */
 	mlxsw_sp_vr_lpm_tree_unbind(mlxsw_sp, fib);
 	mlxsw_sp_lpm_tree_put(mlxsw_sp, fib->lpm_tree);
 	fib->lpm_tree = NULL;