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

[Mike Snitzer <snitzer redhat com>]

On Wed, Sep 01 2010 at  2:59pm -0400,
Mike Snitzer <snitzer redhat com> 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.

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

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.

Thanks,
Mike