netdev - Re: [PATCH] hv_netvsc: update VF after name has changed.

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Message-Id: <20171226.171119.1016371414270103500.davem@davemloft.net>
Date:   Tue, 26 Dec 2017 17:11:19 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     stephen@...workplumber.org
Cc:     netdev@...r.kernel.org, sthemmin@...rosoft.com
Subject: Re: [PATCH] hv_netvsc: update VF after name has changed.

From: Stephen Hemminger <stephen@...workplumber.org>
Date: Tue, 26 Dec 2017 13:51:43 -0800

> On Tue, 26 Dec 2017 12:25:12 -0500 (EST)
> David Miller <davem@...emloft.net> wrote:
> 
>> From: Stephen Hemminger <stephen@...workplumber.org>
>> Date: Wed, 20 Dec 2017 14:33:23 -0800
>> 
>> > Since commit 6123c66854c1 ("netvsc: delay setup of VF device")
>> > the automatic bring up of the VF is delayed to allow userspace (udev)
>> > a chance to rename the device. This delay is problematic because
>> > it delays boot and may not be long enough for some cases.
>> > 
>> > Instead, use the rename can be used to trigger the next step
>> > in setup to happen immediately.
>> > 
>> > The VF initialization sequence now looks like:
>> >    * hotplug causes VF network device probe to create network device
>> >    * netvsc notifier joins VF with netvsc and schedules VF to be
>> >      setup after timer expires
>> >    * udev in userspace renames device
>> >    * if netvsc notifier detects rename, it can cancel timer
>> >      and do immediate setup
>> > 
>> > The delay can also be increased to allow for slower rules.
>> > Still need the delayed work to handle the case where rename is
>> > not done.
>> > 
>> > Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>  
>> 
>> I'm still seriously perplexed by this whole situation.
> 
> See state diagram below
>  
>> Why can't you bring up a VF interface simply because of a text string
>> used to reffered to it?
> 
> VF network device can not have its name changed if up.
> The network device kernel API does not allow name change of network
> device that is up.  There was a patch from Vitaly to allow this, but it
> was deemed to be too risky.
> 
>    https://patchwork.ozlabs.org/patch/799646/

Thank you for the state diagram.

I still, unfortunately, don't see the problem.

If userland changes the name of the VF device, then they will change
it before bringing the VF device up.

Thanks for your patience with me.