netdev - Re: [patch net-next-2.6] net: allow notifier subscribers to forbid device from closing

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Date:	Wed, 31 Aug 2011 16:25:51 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Jiri Pirko <jpirko@...hat.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	eric.dumazet@...il.com, shemminger@...tta.com
Subject: Re: [patch net-next-2.6] net: allow notifier subscribers to forbid
 device from closing

On Wed, 2011-08-31 at 17:15 +0200, Jiri Pirko wrote:
> In some situations, like when the device is used as slave device in
> bond/br/etc it is not nice if someone closes the device. This allows
> it's masters to forbid this closure.

No it doesn't.

[...]
> @@ -1269,9 +1282,12 @@ static int dev_close_many(struct list_head *head)
>  	struct net_device *dev, *tmp;
>  	LIST_HEAD(tmp_list);
>  
> -	list_for_each_entry_safe(dev, tmp, head, unreg_list)
> +	list_for_each_entry_safe(dev, tmp, head, unreg_list) {
>  		if (!(dev->flags & IFF_UP))
>  			list_move(&dev->unreg_list, &tmp_list);
> +		else
> +			__dev_pre_close(dev);
> +	}
>  
>  	__dev_close_many(head);

The return value is ignored here.

And this is called from dev_close(), where you are adding the
notification as well.  So the notifier will usually be called twice.

[...]
> @@ -1397,6 +1418,7 @@ rollback:
>  				break;
>  
>  			if (dev->flags & IFF_UP) {
> +				nb->notifier_call(nb, NETDEV_PRE_DOWN, dev);
>  				nb->notifier_call(nb, NETDEV_GOING_DOWN, dev);
>  				nb->notifier_call(nb, NETDEV_DOWN, dev);
>  			}
[...]

The return value has to be ignored here.  Not sure it makes any sense to
call the notifier at all.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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