netdev - Re: BUG: jumbo frames broken after commit xen-netfront: Fix race between device setup and open

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Message-ID: <62f5027c-d196-32a4-a3ae-89c2fd2d8d06@citrix.com>
Date:   Thu, 21 Jun 2018 14:02:56 +0100
From:   Ross Lagerwall <ross.lagerwall@...rix.com>
To:     Juergen Gross <jgross@...e.com>
CC:     Javier Martinez Canillas <javier@...hile0.org>,
        Andrew Jeddeloh <andrew.jeddeloh@...hat.com>,
        Laura Abbott <labbott@...hat.com>, <dustymabe@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>, <stable@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Liam Shepherd <liam@...cer.es>
Subject: Re: BUG: jumbo frames broken after commit xen-netfront: Fix race
 between device setup and open

On 06/21/2018 10:05 AM, Juergen Gross wrote:
> On 14/06/18 17:43, Javier Martinez Canillas wrote:
>> Hi Andrew,
>>
>> On Wed, Jun 6, 2018 at 6:29 PM, Andrew Jeddeloh
>> <andrew.jeddeloh@...hat.com> wrote:
>>> Hi all,
>>>
>>> The patch "xen-netfront: Fix race between device setup and open" seems
>>> to have introduced a regression preventing setting MTU's larger than
>>> 1500. We experienced this downstream with Container Linux and
>>> confirmed with Fedora 28 as well.
>>>
>>> It's commit f599c64fdf7d9c108e8717fb04bc41c680120da4 in the linux-stable tree.
>>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=f599c64fdf7d9c108e8717fb04bc41c680120da4
>>>
>>> Downstream bugs:
>>> https://github.com/coreos/bugs/issues/2443
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1584216
>>>
>>> We've confirmed that reverting that commit fixes the bug. It be
>>> reliably can be reproduced on AWS with t2.micro instances (and
>>> presumably other systems using the same driver). Both using
>>> systemd-networkd to set the mtu and manual ip link commands cause the
>>> link to repsond with "Invalid argument" when trying to set the MTU >
>>> 1500.
>>>
>>> I'm not sure why that commit introduced the regression.
>>>
>>> Please let me know if there's any more information that would be helpful.
>>>
>>> - Andrew
>>
>> I'm adding some relevant people to the CC list to bring more attention
>> on this regression.
>>
>> The get_maintainer.pl script is very useful to get some hints on who
>> should be copied, i.e:
>>
>> $ ./scripts/get_maintainer.pl -f drivers/net/xen-netfront.c
> 
> Ross, have you made any progress here? If not I'm thinking of reverting
> your patch as I think the current problem is more severe than the one
> your patch did address.
> 
> 

I've sent a patch today which I believe fixes the issue. Sorry for the 
slow response.

Regards,
-- 
Ross Lagerwall