Re: [GIT PULL] Followup single fix for block IO core pull

[Jens Axboe]

On 04/17/2015 09:45 AM, Jens Axboe wrote:
> On 04/17/2015 09:41 AM, Dave Jones wrote:
> > On Fri, Apr 17, 2015 at 09:12:01AM -0600, Jens Axboe wrote:
> >   > Hi Linus,
> >   >
> >   > A commit in the previous pull request introduce a regression. So far
> >   > only observed on qemu-sparc64, but it's a general bug. Please pull
> > this
> >   > single fix to rectify that, thanks.
> >
> > I hit the same bug on two x86 boxes, bare-metal.
> > Reverting the commit Guenter pointed out made them boot again,
> > so definitely not sparc/qemu specific in any way.
> >
> > I suspect the only reason more people didn't see it is that not
> > everyone is running with the mq-by-default config option yet ?
>
> It is puzzling. I ran it on several boxes, both multi queue and not, and
> both single mq queues and multiple. But the code is clearly wrong. So
> yeah, it's not sparc64 specific in any way. My initial thought was that
> this was another issue related to sparse CPU ids, but that's not the
> case. It's a plain bug, unfortunately.

It's the pre morning coffee issue, looks like. All my test boxes end up 
having >= map->bits_per_word CPUs, so the test cases never ran into the 
round down issue.

--
Jens Axboe

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