From: Ido Schimmel <idosch@mellanox.com>
Date: Fri, 21 Feb 2020 19:54:04 +0200
Subject: mlxsw: spectrum_mr: Publish multicast route after writing it to the
 device
Patch-mainline: v5.7-rc1
Git-commit: 3e3c8dafc05f28bfa8065c957620c02bbadf0042
References: bsc#1176774

The driver periodically traverses the linked list of multicast routes
and updates the kernel about packets and bytes statistics from each
multicast route. These statistics are read from a counter associated
with the route when it is written to the device.

Currently, multicast routes are published via this linked list before
they are associated with a counter. Despite that, it is not possible for
the driver to access an invalid counter because the delayed work that
reads the statistics and multicast route addition / deletion are
mutually exclusive using RTNL.

In order to be able to remove RTNL, the list needs to be protected by a
dedicated lock, but any route published via the list must have an
associated counter, otherwise the driver will access an invalid counter.

Solve this by re-ordering the operations during multicast route addition
so that the route is only added to the linked list after it was written
to the device. Similarly, during deletion the route is first removed
from the linked list before its deletion from the device.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c |   17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c
@@ -371,10 +371,10 @@ static void __mlxsw_sp_mr_route_del(stru
 				    struct mlxsw_sp_mr_route *mr_route)
 {
 	mlxsw_sp_mr_mfc_offload_set(mr_route, false);
-	mlxsw_sp_mr_route_erase(mr_table, mr_route);
 	rhashtable_remove_fast(&mr_table->route_ht, &mr_route->ht_node,
 			       mlxsw_sp_mr_route_ht_params);
 	list_del(&mr_route->node);
+	mlxsw_sp_mr_route_erase(mr_table, mr_route);
 	mlxsw_sp_mr_route_destroy(mr_table, mr_route);
 }
 
@@ -415,6 +415,11 @@ int mlxsw_sp_mr_route_add(struct mlxsw_s
 		goto err_duplicate_route;
 	}
 
+	/* Write the route to the hardware */
+	err = mlxsw_sp_mr_route_write(mr_table, mr_route, replace);
+	if (err)
+		goto err_mr_route_write;
+
 	/* Put it in the table data-structures */
 	list_add_tail(&mr_route->node, &mr_table->route_list);
 	err = rhashtable_insert_fast(&mr_table->route_ht,
@@ -423,11 +428,6 @@ int mlxsw_sp_mr_route_add(struct mlxsw_s
 	if (err)
 		goto err_rhashtable_insert;
 
-	/* Write the route to the hardware */
-	err = mlxsw_sp_mr_route_write(mr_table, mr_route, replace);
-	if (err)
-		goto err_mr_route_write;
-
 	/* Destroy the original route */
 	if (replace) {
 		rhashtable_remove_fast(&mr_table->route_ht,
@@ -440,11 +440,10 @@ int mlxsw_sp_mr_route_add(struct mlxsw_s
 	mlxsw_sp_mr_mfc_offload_update(mr_route);
 	return 0;
 
-err_mr_route_write:
-	rhashtable_remove_fast(&mr_table->route_ht, &mr_route->ht_node,
-			       mlxsw_sp_mr_route_ht_params);
 err_rhashtable_insert:
 	list_del(&mr_route->node);
+	mlxsw_sp_mr_route_erase(mr_table, mr_route);
+err_mr_route_write:
 err_no_orig_route:
 err_duplicate_route:
 	mlxsw_sp_mr_route_destroy(mr_table, mr_route);