[PATCH v3 net-next 6/7] net: switchdev: don't assume RCU context in switchdev_handle_fdb_{add,del}_to_device

From: Vladimir Oltean <vladimir.oltean@nxp.com>
To: netdev@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
	"David S. Miller" <davem@davemloft.net>
Cc: Roopa Prabhu <roopa@nvidia.com>,
	Nikolay Aleksandrov <nikolay@nvidia.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Vladimir Oltean <olteanv@gmail.com>,
	Vadym Kochan <vkochan@marvell.com>,
	Taras Chornyi <tchornyi@marvell.com>,
	Jiri Pirko <jiri@nvidia.com>, Ido Schimmel <idosch@nvidia.com>,
	UNGLinuxDriver@microchip.com,
	Grygorii Strashko <grygorii.strashko@ti.com>,
	Marek Behun <kabel@blackhole.sk>,
	DENG Qingfang <dqfext@gmail.com>,
	Kurt Kanzenbach <kurt@linutronix.de>,
	Hauke Mehrtens <hauke@hauke-m.de>,
	Woojung Huh <woojung.huh@microchip.com>,
	Sean Wang <sean.wang@mediatek.com>,
	Landen Chao <Landen.Chao@mediatek.com>,
	Claudiu Manoil <claudiu.manoil@nxp.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	George McCollister <george.mccollister@gmail.com>,
	Ioana Ciornei <ioana.ciornei@nxp.com>,
	Saeed Mahameed <saeedm@nvidia.com>,
	Leon Romanovsky <leon@kernel.org>,
	Lars Povlsen <lars.povlsen@microchip.com>,
	Steen Hegelund <Steen.Hegelund@microchip.com>,
	Julian Wiedmann <jwi@linux.ibm.com>,
	Alexandra Winter <wintera@linux.ibm.com>,
	Karsten Graul <kgraul@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Ivan Vecera <ivecera@redhat.com>, Vlad Buslov <vladbu@nvidia.com>,
	Jianbo Liu <jianbol@nvidia.com>, Mark Bloch <mbloch@nvidia.com>,
	Roi Dayan <roid@nvidia.com>,
	Tobias Waldekranz <tobias@waldekranz.com>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	linux-s390@vger.kernel.org
Subject: [PATCH v3 net-next 6/7] net: switchdev: don't assume RCU context in switchdev_handle_fdb_{add,del}_to_device
Date: Fri, 20 Aug 2021 14:57:45 +0300	[thread overview]
Message-ID: <20210820115746.3701811-7-vladimir.oltean@nxp.com> (raw)
In-Reply-To: <20210820115746.3701811-1-vladimir.oltean@nxp.com>

Now that the SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE events are blocking, it
would be nice if callers of the fan-out helper functions (i.e. DSA)
could benefit from that blocking context.

But at the moment, switchdev_handle_fdb_{add,del}_to_device use some
netdev adjacency list checking functions that assume RCU protection.
Switch over to their rtnl_mutex equivalents, since we are also running
with that taken, and drop the surrounding rcu_read_lock from the callers.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
v2->v3: none

 net/dsa/slave.c           |  4 ----
 net/switchdev/switchdev.c | 10 +++++++---
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 6601224f6a5a..196a0e1f4294 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -2484,22 +2484,18 @@ static int dsa_slave_switchdev_blocking_event(struct notifier_block *unused,
 						     dsa_slave_port_attr_set);
 		return notifier_from_errno(err);
 	case SWITCHDEV_FDB_ADD_TO_DEVICE:
-		rcu_read_lock();
 		err = switchdev_handle_fdb_add_to_device(dev, ptr,
 							 dsa_slave_dev_check,
 							 dsa_foreign_dev_check,
 							 dsa_slave_fdb_add_to_device,
 							 NULL);
-		rcu_read_unlock();
 		return notifier_from_errno(err);
 	case SWITCHDEV_FDB_DEL_TO_DEVICE:
-		rcu_read_lock();
 		err = switchdev_handle_fdb_del_to_device(dev, ptr,
 							 dsa_slave_dev_check,
 							 dsa_foreign_dev_check,
 							 dsa_slave_fdb_del_to_device,
 							 NULL);
-		rcu_read_unlock();
 		return notifier_from_errno(err);
 	}
 
diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index d09e8e9df5b6..fdbb73439f37 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -470,7 +470,7 @@ switchdev_lower_dev_find(struct net_device *dev,
 		.data = &switchdev_priv,
 	};
 
-	netdev_walk_all_lower_dev_rcu(dev, switchdev_lower_dev_walk, &priv);
+	netdev_walk_all_lower_dev(dev, switchdev_lower_dev_walk, &priv);
 
 	return switchdev_priv.lower_dev;
 }
@@ -543,7 +543,7 @@ static int __switchdev_handle_fdb_add_to_device(struct net_device *dev,
 	/* Event is neither on a bridge nor a LAG. Check whether it is on an
 	 * interface that is in a bridge with us.
 	 */
-	br = netdev_master_upper_dev_get_rcu(dev);
+	br = netdev_master_upper_dev_get(dev);
 	if (!br || !netif_is_bridge_master(br))
 		return 0;
 
@@ -569,6 +569,8 @@ int switchdev_handle_fdb_add_to_device(struct net_device *dev,
 {
 	int err;
 
+	ASSERT_RTNL();
+
 	err = __switchdev_handle_fdb_add_to_device(dev, dev, fdb_info,
 						   check_cb,
 						   foreign_dev_check_cb,
@@ -648,7 +650,7 @@ static int __switchdev_handle_fdb_del_to_device(struct net_device *dev,
 	/* Event is neither on a bridge nor a LAG. Check whether it is on an
 	 * interface that is in a bridge with us.
 	 */
-	br = netdev_master_upper_dev_get_rcu(dev);
+	br = netdev_master_upper_dev_get(dev);
 	if (!br || !netif_is_bridge_master(br))
 		return 0;
 
@@ -674,6 +676,8 @@ int switchdev_handle_fdb_del_to_device(struct net_device *dev,
 {
 	int err;
 
+	ASSERT_RTNL();
+
 	err = __switchdev_handle_fdb_del_to_device(dev, dev, fdb_info,
 						   check_cb,
 						   foreign_dev_check_cb,
-- 
2.25.1

