[ovs-dev] datapath/linux/compat question

[Kyle Mestery]

On Wed, Apr 2, 2014 at 7:05 PM, Jesse Gross <jesse at nicira.com> wrote:
> On Wed, Apr 2, 2014 at 9:56 AM, Zoltan Kiss <zoltan.kiss at citrix.com> wrote:
>> On 01/04/14 20:26, Jesse Gross wrote:
>>>
>>> On Tue, Apr 1, 2014 at 11:41 AM, Kyle Mestery <mestery at noironetworks.com>
>>> wrote:
>>>>
>>>> On Tue, Apr 1, 2014 at 1:27 PM, Zoltan Kiss <zoltan.kiss at citrix.com>
>>>> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> I have a recent patch on net-next which affects OVS as well:
>>>>>
>>>>>
>>>>> http://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=36d5fe6a000790f56039afe26834265db0a3ad4c
>>>>>
>>>>> I guess the changes for datapatch.c will turn up automagically sometime
>>>>> during a merge, is that correct?
>>>>> But there is a change in the core skbuff API which need to be included
>>>>> in
>>>>> datapath/linux/compat/skbuff-openvswitch.c, otherwise upstream OVS won't
>>>>> build on older kernels. How does this process works? Is there any
>>>>> guarantee
>>>>> that even if it's forgotten during the merge, a build system somewhere
>>>>> will
>>>>> try to compile upstream OVS with older kernel, and sends a message when
>>>>> it
>>>>> fails?
>>>>
>>>>
>>>> Hi Zoltan:
>>>>
>>>> I just proposed a patch to support Linux 3.13 and 3.14, and this
>>>> includes your patch
>>>> folded in. The mailing lists server appears to be down now, otherwise
>>>> I would have
>>>> included a link. But I've taken care of the skbuff API change as well.
>>>> Feedback on
>>>> this patch is appreciated!
>>>
>>>
>>> To answer the more general question, there's unfortunately nothing
>>> automatic about it. In many cases, changes will cause compilation to
>>> fail on older kernels if an upstream patch is missed when adding
>>> support for a newer kernel but that's not always the case (including
>>> this one I believe). The best thing is if authors submit their changes
>>> to both repositories (with backports if necessary), otherwise it falls
>>> to somebody to do it like Kyle has done here.
>>
>>
>> My understanding is that things from the main OVS repo's datapath directory
>> merge to git://git.kernel.org/pub/scm/linux/kernel/git/jesse/openvswitch
>> after a while, and then to net(-next), is that correct?
>> I think the merge from OVS repo to Jesse's kernel.org repo are made
>> manually, shouldn't you add a step to compare net(-next) with your repo as
>> well? I mean the history for the net/openvswitch directory. That way you can
>> see if something changed OVS in the mainline kernel tree and take action to
>> merge it backwards to the main OVS repo.
>
> Right, this is essentially what Kyle has done with his patch.

+1