netdev - Re: [PATCH net-next] macvlan: fix failure during registration

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Date:	Mon, 18 Apr 2016 16:33:07 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Francesco Ruggeri <fruggeri@...sta.com>
Cc:	netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Mahesh Bandewar <maheshb@...gle.com>
Subject: Re: [PATCH net-next] macvlan: fix failure during registration

Francesco Ruggeri <fruggeri@...sta.com> writes:

> On Mon, Apr 18, 2016 at 11:48 AM, Eric W. Biederman
> <ebiederm@...ssion.com> wrote:
>>
>> These interactions all seem a little bit funny.  At a quick skim it
>> would make more sense to increment the port count in macvlan_init,
>> and completely remove the need to mess with port counts anywhere except
>> macvlan_init and macvlan_uninit.
>
> Thanks Eric, let me try that.
>
>>
>> If for some reason that can't be done the code can easily look at
>> dev->reg_state.  If dev->reg_state == NETREG_UNITIALIZED it should
>> be exactly the same as your new flag being set.
>>
>
> I am not sure that in macvlan_uninit one can tell whether it is being
> invoked in the context of a failed register_netdevice (if that is what
> you meant).
>
> In case of register_netdevice failing in
> call_netdevice_notifiers(NETDEV_REGISTER) the call sequence is:
>
> macvlan_common_newlink
>   register_netdevice
>     call_netdevice_notifiers(NETDEV_REGISTER, dev) (<== fail here)
>       rollback_registered(dev);
>         rollback_registered_many
>           dev->reg_state = NETREG_UNREGISTERING
>           dev->netdev_ops->ndo_uninit(dev)
>       dev->reg_state = NETREG_UNREGISTERED;
>

The code I have looks a little different.  But that is a good point.

But please see if you can get macvlan_init to do the necessary work.
That should simplify everything, and make clever games unnecessary.

Eric