Re: [dm-devel] [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm

[Tejun Heo <tj kernel org>]

Hello,

On 09/02/2010 05:22 AM, Mike Snitzer wrote:
>> But we can meet in the middle.  I've reordered the DM FLUSH+FUA patches
>> so that the more intrusive bio-based relaxed ordering patch is at the
>> very end.
>>
>> My hope was that the request-based deadlock I'm seeing would disappear
>> if that relaxed ordering patch wasn't applied.  Unfortunately, I still
>> see the hang.

I don't think it would make any difference.  AFAICS, the patch doesn't
touch anything requested based dm uses.

> Turns out I can reproduce the hang on a stock 2.6.36-rc3 (without _any_
> FLUSH+FUA patches)!

Hmmm... that's interesting.

> I'll try to pin-point the root cause but I think my test is somehow
> exposing a bug in my virt setup.
> 
> So this hang is definitely starting to look like a red herring.
> 
> Tejun,
> 
> This news should clear the way for you to re-post your patches.  I think
> it would be best if you reordered the DM patches like I did here in this
> series: http://people.redhat.com/msnitzer/patches/flush-fua/series
> 
> In particular, the dm-relax-ordering-of-bio-based-flush-implementation
> patch should go at the end.  I think it makes for a more logical
> evolution of the DM code.

Sure, I'll.  I still think having the queue kicking mechanism is a
good idea tho.  I'll integrate that into series, reorder and repost
it.

Thanks.

-- 
tejun