mlxsw: spectrum_router: Allocate discard adjacency entry when needed

Commit 0c3cbbf96d ("mlxsw: Add specific trap for packets routed via
invalid nexthops") allocated an adjacency entry during driver
initialization whose purpose is to discard packets hitting the route
pointing to it.

These adjacency entries are allocated from a resource called KVD linear
(KVDL). There are situations in which the user can decide to set the
size of this resource (via devlink-resource) to 0, in which case the
driver will not be able to load.

Therefore, instead of pre-allocating this adjacency entry, simply
allocate it only when needed. A variable indicating the validity of the
entry is added and is used to ensure it is only allocated and written
once and that it is freed after all the routes were flushed.

Fixes: 0c3cbbf96d ("mlxsw: Add specific trap for packets routed via invalid nexthops")
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

@@ -78,6 +78,7 @@ struct mlxsw_sp_router {
 	const struct mlxsw_sp_rif_ops **rif_ops_arr;
 	const struct mlxsw_sp_ipip_ops **ipip_ops_arr;
 	u32 adj_discard_index;
+	bool adj_discard_index_valid;
 };
 
 struct mlxsw_sp_rif {
@@ -4203,13 +4204,33 @@ static int mlxsw_sp_adj_discard_write(struct mlxsw_sp *mlxsw_sp, u16 rif_index)
 	u32 adj_discard_index = mlxsw_sp->router->adj_discard_index;
 	enum mlxsw_reg_ratr_trap_action trap_action;
 	char ratr_pl[MLXSW_REG_RATR_LEN];
+	int err;
+
+	if (mlxsw_sp->router->adj_discard_index_valid)
+		return 0;
+
+	err = mlxsw_sp_kvdl_alloc(mlxsw_sp, MLXSW_SP_KVDL_ENTRY_TYPE_ADJ, 1,
+				  &mlxsw_sp->router->adj_discard_index);
+	if (err)
+		return err;
 
 	trap_action = MLXSW_REG_RATR_TRAP_ACTION_DISCARD_ERRORS;
 	mlxsw_reg_ratr_pack(ratr_pl, MLXSW_REG_RATR_OP_WRITE_WRITE_ENTRY, true,
 			    MLXSW_REG_RATR_TYPE_ETHERNET, adj_discard_index,
 			    rif_index);
 	mlxsw_reg_ratr_trap_action_set(ratr_pl, trap_action);
-	return mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(ratr), ratr_pl);
+	err = mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(ratr), ratr_pl);
+	if (err)
+		goto err_ratr_write;
+
+	mlxsw_sp->router->adj_discard_index_valid = true;
+
+	return 0;
+
+err_ratr_write:
+	mlxsw_sp_kvdl_free(mlxsw_sp, MLXSW_SP_KVDL_ENTRY_TYPE_ADJ, 1,
+			   mlxsw_sp->router->adj_discard_index);
+	return err;
 }
 
 static int mlxsw_sp_fib_entry_op_remote(struct mlxsw_sp *mlxsw_sp,
@@ -5956,6 +5977,16 @@ static void mlxsw_sp_router_fib_flush(struct mlxsw_sp *mlxsw_sp)
 			continue;
 		mlxsw_sp_vr_fib_flush(mlxsw_sp, vr, MLXSW_SP_L3_PROTO_IPV6);
 	}
+
+	/* After flushing all the routes, it is not possible anyone is still
+	 * using the adjacency index that is discarding packets, so free it in
+	 * case it was allocated.
+	 */
+	if (!mlxsw_sp->router->adj_discard_index_valid)
+		return;
+	mlxsw_sp_kvdl_free(mlxsw_sp, MLXSW_SP_KVDL_ENTRY_TYPE_ADJ, 1,
+			   mlxsw_sp->router->adj_discard_index);
+	mlxsw_sp->router->adj_discard_index_valid = false;
 }
 
 static void mlxsw_sp_router_fib_abort(struct mlxsw_sp *mlxsw_sp)
@@ -8170,11 +8201,6 @@ int mlxsw_sp_router_init(struct mlxsw_sp *mlxsw_sp,
 	if (err)
 		goto err_neigh_init;
 
-	err = mlxsw_sp_kvdl_alloc(mlxsw_sp, MLXSW_SP_KVDL_ENTRY_TYPE_ADJ, 1,
-				  &router->adj_discard_index);
-	if (err)
-		goto err_adj_discard_index_alloc;
-
 	mlxsw_sp->router->netevent_nb.notifier_call =
 		mlxsw_sp_router_netevent_event;
 	err = register_netevent_notifier(&mlxsw_sp->router->netevent_nb);
@@ -8203,9 +8229,6 @@ err_dscp_init:
 err_mp_hash_init:
 	unregister_netevent_notifier(&mlxsw_sp->router->netevent_nb);
 err_register_netevent_notifier:
-	mlxsw_sp_kvdl_free(mlxsw_sp, MLXSW_SP_KVDL_ENTRY_TYPE_ADJ, 1,
-			   router->adj_discard_index);
-err_adj_discard_index_alloc:
 	mlxsw_sp_neigh_fini(mlxsw_sp);
 err_neigh_init:
 	mlxsw_sp_vrs_fini(mlxsw_sp);
@@ -8237,8 +8260,6 @@ void mlxsw_sp_router_fini(struct mlxsw_sp *mlxsw_sp)
 	unregister_fib_notifier(mlxsw_sp_net(mlxsw_sp),
 				&mlxsw_sp->router->fib_nb);
 	unregister_netevent_notifier(&mlxsw_sp->router->netevent_nb);
-	mlxsw_sp_kvdl_free(mlxsw_sp, MLXSW_SP_KVDL_ENTRY_TYPE_ADJ, 1,
-			   mlxsw_sp->router->adj_discard_index);
 	mlxsw_sp_neigh_fini(mlxsw_sp);
 	mlxsw_sp_vrs_fini(mlxsw_sp);
 	mlxsw_sp_mr_fini(mlxsw_sp);