netdev - Re: [PATCH net] net: team: do not use dynamic lockdep key

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Message-ID: <20230907103124.6adb7256@kernel.org>
Date: Thu, 7 Sep 2023 10:31:24 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Taehee Yoo <ap420073@...il.com>
Cc: davem@...emloft.net, pabeni@...hat.com, edumazet@...gle.com,
 jiri@...nulli.us, netdev@...r.kernel.org,
 syzbot+9bbbacfbf1e04d5221f7@...kaller.appspotmail.com
Subject: Re: [PATCH net] net: team: do not use dynamic lockdep key

On Tue,  5 Sep 2023 08:46:10 +0000 Taehee Yoo wrote:
> @@ -1203,18 +1203,31 @@ static int team_port_add(struct team *team, struct net_device *port_dev,
>  
>  	memcpy(port->orig.dev_addr, port_dev->dev_addr, port_dev->addr_len);
>  
> -	err = team_port_enter(team, port);
> +	err = dev_open(port_dev, extack);
>  	if (err) {
> -		netdev_err(dev, "Device %s failed to enter team mode\n",
> +		netdev_dbg(dev, "Device %s opening failed\n",
>  			   portname);
> -		goto err_port_enter;
> +		goto err_dev_open;
>  	}
>  
> -	err = dev_open(port_dev, extack);
> +	err = team_upper_dev_link(team, port, extack);

I'm guessing the syzbot complaint:

https://lore.kernel.org/all/000000000000e44e4a0604c66b67@google.com/

is related to this reordering of team_upper_dev_link() before things
are initialized. I'll revert this version in net, let's target v2 at
net-next, next week? "lockdep runs out of keys" isn't a real bug,
or at least I don't think the benefit is high enough for pushing
functional code changes into current release. Sounds reasonable?

>  	if (err) {
> -		netdev_dbg(dev, "Device %s opening failed\n",
> +		netdev_err(dev, "Device %s failed to set upper link\n",
>  			   portname);
> -		goto err_dev_open;
> +		goto err_set_upper_link;
> +	}
> +
> +	/* lockdep subclass variable(dev->nested_level) was updated by
> +	 * team_upper_dev_link().
> +	 */
> +	team_unlock(team);
> +	team_lock(team);
> +
> +	err = team_port_enter(team, port);
> +	if (err) {
> +		netdev_err(dev, "Device %s failed to enter team mode\n",
> +			   portname);
> +		goto err_port_enter;
>  	}
>  
>  	err = vlan_vids_add_by_dev(port_dev, dev);
> @@ -1242,13 +1255,6 @@ static int team_port_add(struct team *team, struct net_device *port_dev,
>  		goto err_handler_register;
>  	}
>  
> -	err = team_upper_dev_link(team, port, extack);
> -	if (err) {
> -		netdev_err(dev, "Device %s failed to set upper link\n",
> -			   portname);
> -		goto err_set_upper_link;
> -	}