[Xen-devel] Re: netback commit history

Jan Beulich
Tue, 20 Sep 2011 13:03:36 -0000

>>> On 20.09.11 at 14:40, Ian Campbell
<Ian.Campbell@eu.citrix.com> wrote:
> On Tue, 2011-09-20 at 12:46 +0100, Jan Beulich wrote:
>> >>> On 20.09.11 at 13:26, Ian Campbell
<Ian.Campbell@eu.citrix.com> wrote:
>> > On Tue, 2011-09-20 at 12:04 +0100, Jan Beulich wrote:
>> >> with the upstream netback introduction consisting of a single
big commit
>> >> I wonder whether you could point me to where the full history
of it is.
>> >
>> > Yeah, that was a bit annoying, luckily I had the foresight to post
where
>> > the history was.
http://www.gossamer-threads.com/lists/xen/devel/202139
>> > says it is:
>> >         git://xenbits.xen.org/people/ianc/linux-2.6.git
>> > upstream/dom0/backend/netback-history
>>
>> Does this have a http:// representation somewhere (it doesn''t
show up
>> under http://xenbits.xen.org/people/ianc/)?
>
> http://xenbits.xen.org/gitweb/?p=people/ianc/linux-2.6.git;a=summary
>
>>
>> >> I''m asking particularly in the context of us being
asked to add a safety
>> >> check similar to the vif->netbk != NULL one at the
beginning of
>> >> xenvif_start_xmit() (also in xenvif_interrupt(), but there we
have a
>> >> similar check in place), which hadn''t been in the
legacy tree (obviously)
>> >> nor in the original multiple-tasklets patch that I retained a
copy of.
>> >
>> > Seems to have come from bc05ada1283eb583c9789c27429af36b034c4a74
in that
>> > history tree and was a conversion from a check for group == -1.
That
>> > commit changes from storing a group index to a group pointer so I
think
>> > it''s roughly equivalent from a validity point of view.
>> >
>> > The original group == -1 check appears to be in the 2.6.32.x pvops
>> > kernels at least, I expect it is also in the multiple tasklet
patch
>> > which you have as well?
>>
>> That''s the point - we don''t.
>
> Wierd, it is in 020ba9067e121b720a3335521698ea9cf31f6166 in
Jeremy''s
> xen/2.6.32-stable branch which is the original "xen/netback: Multiple
> tasklets support." commit. Did you pick up an earlier posting?
>
> I found the original postings
> v2:
http://lists.xensource.com/archives/html/xen-devel/2010-04/msg01578.html
> v3: http://www.gossamer-threads.com/lists/xen/devel/170582
> v4:
http://lists.xensource.com/archives/html/xen-devel/2010-05/msg00140.html
>
> From the looks things the check arrived in v3 but there is no comment on
> the patch saying why, nor does any review I found of v2 give a hint. I
> had a bit of a trawl through various list archives of the other postings
> of the series but didn''t spot anything.

Seems like my original is actually v1, and I may not have picked up
that later change precisely because it wasn''t mentioned in the
description and I didn''t look closely enough at the changes plus I
had done quite a bit of other cleanup on v1 already and hence
didn''t want to start over. v3 is also where the similar check in
netif_be_int() appears, and I know for sure we had to add this
due to another bug report, not due to the change there.

In any case, thanks a lot for helping with this!