netdev - [PATCH v2 net-next 4/5] net: switchdev: don't assume RCU context in switchdev_handle_fdb_{add,del}_to

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Date:   Thu, 19 Aug 2021 19:07:22 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Vadym Kochan <vkochan@...vell.com>,
        Taras Chornyi <tchornyi@...vell.com>,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        UNGLinuxDriver@...rochip.com,
        Grygorii Strashko <grygorii.strashko@...com>,
        Marek Behun <kabel@...ckhole.sk>,
        DENG Qingfang <dqfext@...il.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        George McCollister <george.mccollister@...il.com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        Julian Wiedmann <jwi@...ux.ibm.com>,
        Karsten Graul <kgraul@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Ivan Vecera <ivecera@...hat.com>,
        Vlad Buslov <vladbu@...dia.com>,
        Jianbo Liu <jianbol@...dia.com>,
        Mark Bloch <mbloch@...dia.com>, Roi Dayan <roid@...dia.com>,
        Tobias Waldekranz <tobias@...dekranz.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: [PATCH v2 net-next 4/5] net: switchdev: don't assume RCU context in switchdev_handle_fdb_{add,del}_to_device

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@....com>
---
 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 249303ac3c3c..b6a94861cddd 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