From: Ed Cashin <ecashin@coraid.com>
Date: Wed, 9 Sep 2009 17:23:49 -0400
To: jens.axboe@oracle.com, ecashin@coraid.com, alan@lxorguk.ukuu.org.uk,
       akpm@linux-foundation.org, apw@canonical.com, bonbons@linux-vserver.org,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] aoe: end barrier bios with EOPNOTSUPP
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On Wed Sep  9 16:59:30 EDT 2009, jens.axboe@oracle.com wrote:
> On Wed, Sep 09 2009, Ed Cashin wrote:
...
> > To implement the barrier, [aoe] would stop generating new AoE write
> > commands, wait for AoE write responses for all the outstanding write
> > commands, issue the ATA cache flush command, wait for the response to
> > the flush, and then resume normal activity.
> 
> That's how barriers work with sata to begin with, so I'd very much
> recommend that you do the same in aoe instead of just not supporting it.

This patch with EOPNOTSUPP just fixes the regression in 2.6.31-rc9.

A patch adding support for barriers would be nice.  Since I have
limited time I tried to motivate that work by using the torture tests
that Chris Mason (I believe it was) posted a while ago, but I could
not get any problems to manifest using that torture test.

If I had a reproducable problem case that the barrier implementation
could fix, it would be very helpful.

-- 
  Ed
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