Merge branch 'net-depend-on-instance-lock-for-queue-related-netlink-ops'

Jakub Kicinski says:

====================
net: depend on instance lock for queue related netlink ops

netdev-genl used to be protected by rtnl_lock. In previous release
we already switched the queue management ops (for Rx zero-copy) to
the instance lock. This series converts other ops to depend on the
instance lock when possible.

Unfortunately queue related state is hard to lock (unlike NAPI)
as the process of switching the number of queues usually involves
a large reconfiguration of the driver. The reconfig process has
historically been under rtnl_lock, but for drivers which opt into
ops locking it is also under the instance lock. Leverage that
and conditionally take rtnl_lock or instance lock depending
on the device capabilities.

v1: https://lore.kernel.org/20250407190117.16528-1-kuba@kernel.org
====================

Link: https://patch.msgid.link/20250408195956.412733-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 69 insertions, 7 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 4ccc6dc5303e..b52efa4cec56 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -828,7 +828,7 @@ netdev_napi_by_id_lock(struct net *net, unsigned int napi_id)
 	dev_hold(dev);
 	rcu_read_unlock();
 
-	dev = __netdev_put_lock(dev);
+	dev = __netdev_put_lock(dev, net);
 	if (!dev)
 		return NULL;
 
@@ -1039,10 +1039,11 @@ struct net_device *dev_get_by_napi_id(unsigned int napi_id)
  * This helper is intended for locking net_device after it has been looked up
  * using a lockless lookup helper. Lock prevents the instance from going away.
  */
-struct net_device *__netdev_put_lock(struct net_device *dev)
+struct net_device *__netdev_put_lock(struct net_device *dev, struct net *net)
 {
 	netdev_lock(dev);
-	if (dev->reg_state > NETREG_REGISTERED) {
+	if (dev->reg_state > NETREG_REGISTERED ||
+	    dev->moving_ns || !net_eq(dev_net(dev), net)) {
 		netdev_unlock(dev);
 		dev_put(dev);
 		return NULL;
@@ -1051,6 +1052,20 @@ struct net_device *__netdev_put_lock(struct net_device *dev)
 	return dev;
 }
 
+static struct net_device *
+__netdev_put_lock_ops_compat(struct net_device *dev, struct net *net)
+{
+	netdev_lock_ops_compat(dev);
+	if (dev->reg_state > NETREG_REGISTERED ||
+	    dev->moving_ns || !net_eq(dev_net(dev), net)) {
+		netdev_unlock_ops_compat(dev);
+		dev_put(dev);
+		return NULL;
+	}
+	dev_put(dev);
+	return dev;
+}
+
 /**
  *	netdev_get_by_index_lock() - find a device by its ifindex
  *	@net: the applicable net namespace
@@ -1070,7 +1085,19 @@ struct net_device *netdev_get_by_index_lock(struct net *net, int ifindex)
 	if (!dev)
 		return NULL;
 
-	return __netdev_put_lock(dev);
+	return __netdev_put_lock(dev, net);
+}
+
+struct net_device *
+netdev_get_by_index_lock_ops_compat(struct net *net, int ifindex)
+{
+	struct net_device *dev;
+
+	dev = dev_get_by_index(net, ifindex);
+	if (!dev)
+		return NULL;
+
+	return __netdev_put_lock_ops_compat(dev, net);
 }
 
 struct net_device *
@@ -1090,7 +1117,32 @@ netdev_xa_find_lock(struct net *net, struct net_device *dev,
 		dev_hold(dev);
 		rcu_read_unlock();
 
-		dev = __netdev_put_lock(dev);
+		dev = __netdev_put_lock(dev, net);
+		if (dev)
+			return dev;
+
+		(*index)++;
+	} while (true);
+}
+
+struct net_device *
+netdev_xa_find_lock_ops_compat(struct net *net, struct net_device *dev,
+			       unsigned long *index)
+{
+	if (dev)
+		netdev_unlock_ops_compat(dev);
+
+	do {
+		rcu_read_lock();
+		dev = xa_find(&net->dev_by_index, index, ULONG_MAX, XA_PRESENT);
+		if (!dev) {
+			rcu_read_unlock();
+			return NULL;
+		}
+		dev_hold(dev);
+		rcu_read_unlock();
+
+		dev = __netdev_put_lock_ops_compat(dev, net);
 		if (dev)
 			return dev;
 
@@ -12157,7 +12209,11 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	netif_close(dev);
 	/* And unlink it from device chain */
 	unlist_netdevice(dev);
-	netdev_unlock_ops(dev);
+
+	if (!netdev_need_ops_lock(dev))
+		netdev_lock(dev);
+	dev->moving_ns = true;
+	netdev_unlock(dev);
 
 	synchronize_net();
 
@@ -12193,7 +12249,9 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	move_netdevice_notifiers_dev_net(dev, net);
 
 	/* Actually switch the network namespace */
+	netdev_lock(dev);
 	dev_net_set(dev, net);
+	netdev_unlock(dev);
 	dev->ifindex = new_ifindex;
 
 	if (new_name[0]) {
@@ -12219,7 +12277,11 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	err = netdev_change_owner(dev, net_old, net);
 	WARN_ON(err);
 
-	netdev_lock_ops(dev);
+	netdev_lock(dev);
+	dev->moving_ns = false;
+	if (!netdev_need_ops_lock(dev))
+		netdev_unlock(dev);
+
 	/* Add the device back in the hashes */
 	list_netdevice(dev);
 	/* Notify protocols, that a new device appeared. */