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

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Date:	Mon, 18 Apr 2016 13:10:51 -0700
From:	Francesco Ruggeri <fruggeri@...sta.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.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

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;


Francesco