linux-kernel - [PATCH v2 net-next 4/6] net: dsa: exit early in dsa_slave_switchdev

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Date:   Sun, 13 Dec 2020 04:40:16 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     DENG Qingfang <dqfext@...il.com>,
        Tobias Waldekranz <tobias@...dekranz.com>,
        Marek Behun <marek.behun@....cz>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Alexandra Winter <wintera@...ux.ibm.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ido Schimmel <idosch@...sch.org>,
        Claudiu Manoil <claudiu.manoil@....com>
Subject: [PATCH v2 net-next 4/6] net: dsa: exit early in dsa_slave_switchdev_event if we can't program the FDB

Right now, the following would happen for a switch driver that does not
implement .port_fdb_add or .port_fdb_del.

dsa_slave_switchdev_event returns NOTIFY_OK and schedules:
-> dsa_slave_switchdev_event_work
   -> dsa_port_fdb_add
      -> dsa_port_notify(DSA_NOTIFIER_FDB_ADD)
         -> dsa_switch_fdb_add
            -> if (!ds->ops->port_fdb_add) return -EOPNOTSUPP;
   -> an error is printed with dev_dbg, and
      dsa_fdb_offload_notify(switchdev_work) is not called.

We can avoid scheduling the worker for nothing and say NOTIFY_OK.
Because we don't call dsa_fdb_offload_notify, the static FDB entry will
remain just in the software bridge.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
Changes in v2:
Patch is new.

 net/dsa/slave.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 99907e76770b..53d9d2ea9369 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -2129,6 +2129,9 @@ static int dsa_slave_switchdev_event(struct notifier_block *unused,
 
 		dp = dsa_slave_to_port(dev);
 
+		if (!dp->ds->ops->port_fdb_add || !dp->ds->ops->port_fdb_del)
+			return NOTIFY_DONE;
+
 		switchdev_work = kzalloc(sizeof(*switchdev_work), GFP_ATOMIC);
 		if (!switchdev_work)
 			return NOTIFY_BAD;
-- 
2.25.1