netdev - Re: [patch net] devlink: change port event netdev notifier from per-net to global

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Date:   Tue, 14 Feb 2023 10:41:36 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com, edumazet@...gle.com, jacob.e.keller@...el.com
Subject: Re: [patch net] devlink: change port event netdev notifier from
 per-net to global

On Mon, Feb 06, 2023 at 10:41:51AM +0100, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@...dia.com>
> 
> Currently only the network namespace of devlink instance is monitored
> for port events. If netdev is moved to a different namespace and then
> unregistered, NETDEV_PRE_UNINIT is missed which leads to trigger
> following WARN_ON in devl_port_unregister().
> WARN_ON(devlink_port->type != DEVLINK_PORT_TYPE_NOTSET);
> 
> Fix this by changing the netdev notifier from per-net to global so no
> event is missed.
> 
> Fixes: 02a68a47eade ("net: devlink: track netdev with devlink_port assigned")
> Signed-off-by: Jiri Pirko <jiri@...dia.com>
> ---
>  net/core/devlink.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/net/core/devlink.c b/net/core/devlink.c
> index 032d6d0a5ce6..909a10e4b0dd 100644
> --- a/net/core/devlink.c
> +++ b/net/core/devlink.c
> @@ -9979,7 +9979,7 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
>  		goto err_xa_alloc;
>  
>  	devlink->netdevice_nb.notifier_call = devlink_netdevice_event;
> -	ret = register_netdevice_notifier_net(net, &devlink->netdevice_nb);
> +	ret = register_netdevice_notifier(&devlink->netdevice_nb);
>  	if (ret)
>  		goto err_register_netdevice_notifier;
>  
> @@ -10171,8 +10171,7 @@ void devlink_free(struct devlink *devlink)
>  	xa_destroy(&devlink->snapshot_ids);
>  	xa_destroy(&devlink->ports);
>  
> -	WARN_ON_ONCE(unregister_netdevice_notifier_net(devlink_net(devlink),
> -						       &devlink->netdevice_nb));
> +	WARN_ON_ONCE(unregister_netdevice_notifier(&devlink->netdevice_nb));
>  
>  	xa_erase(&devlinks, devlink->index);
>  
> @@ -10503,6 +10502,8 @@ static int devlink_netdevice_event(struct notifier_block *nb,
>  		break;
>  	case NETDEV_REGISTER:
>  	case NETDEV_CHANGENAME:
> +		if (devlink_net(devlink) != dev_net(netdev))
> +			return NOTIFY_OK;
>  		/* Set the netdev on top of previously set type. Note this
>  		 * event happens also during net namespace change so here
>  		 * we take into account netdev pointer appearing in this
> @@ -10512,6 +10513,8 @@ static int devlink_netdevice_event(struct notifier_block *nb,
>  					netdev);
>  		break;
>  	case NETDEV_UNREGISTER:
> +		if (devlink_net(devlink) != dev_net(netdev))
> +			return NOTIFY_OK;
>  		/* Clear netdev pointer, but not the type. This event happens
>  		 * also during net namespace change so we need to clear
>  		 * pointer to netdev that is going to another net namespace.

Since the notifier block is no longer registered per-netns it shouldn't
be moved to a different netns on reload. I'm testing the following diff
[1] against net-next (although it should be eventually submitted to
net).

[1]
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d9cdbc047b49..efbee940bb03 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2858,8 +2858,6 @@ int unregister_netdevice_notifier(struct notifier_block *nb);
 int register_netdevice_notifier_net(struct net *net, struct notifier_block *nb);
 int unregister_netdevice_notifier_net(struct net *net,
 				      struct notifier_block *nb);
-void move_netdevice_notifier_net(struct net *src_net, struct net *dst_net,
-				 struct notifier_block *nb);
 int register_netdevice_notifier_dev_net(struct net_device *dev,
 					struct notifier_block *nb,
 					struct netdev_net_notifier *nn);
diff --git a/net/core/dev.c b/net/core/dev.c
index 7307a0c15c9f..709b1a02820b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1870,14 +1870,6 @@ static void __move_netdevice_notifier_net(struct net *src_net,
 	__register_netdevice_notifier_net(dst_net, nb, true);
 }
 
-void move_netdevice_notifier_net(struct net *src_net, struct net *dst_net,
-				 struct notifier_block *nb)
-{
-	rtnl_lock();
-	__move_netdevice_notifier_net(src_net, dst_net, nb);
-	rtnl_unlock();
-}
-
 int register_netdevice_notifier_dev_net(struct net_device *dev,
 					struct notifier_block *nb,
 					struct netdev_net_notifier *nn)
diff --git a/net/devlink/dev.c b/net/devlink/dev.c
index ab4e0f3c4e3d..c879c3c78e18 100644
--- a/net/devlink/dev.c
+++ b/net/devlink/dev.c
@@ -343,8 +343,6 @@ static void devlink_reload_netns_change(struct devlink *devlink,
 	 * reload process so the notifications are generated separatelly.
 	 */
 	devlink_notify_unregister(devlink);
-	move_netdevice_notifier_net(curr_net, dest_net,
-				    &devlink->netdevice_nb);
 	write_pnet(&devlink->_net, dest_net);
 	devlink_notify_register(devlink);
 }