linux-ext4 - Re: [Gluster-devel] regressions due to 64-bit ext4 directory cookies

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Message-ID: <51549D74.1060703@redhat.com>
Date:	Thu, 28 Mar 2013 15:43:48 -0400
From:	Jeff Darcy <jdarcy@...hat.com>
To:	Anand Avati <anand.avati@...il.com>
CC:	"J. Bruce Fields" <bfields@...ldses.org>,
	Eric Sandeen <sandeen@...hat.com>, linux-nfs@...r.kernel.org,
	"Theodore Ts'o" <tytso@....edu>, Zach Brown <zab@...hat.com>,
	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>,
	linux-ext4@...r.kernel.org, gluster-devel@...gnu.org
Subject: Re: [Gluster-devel] regressions due to 64-bit ext4 directory cookies

On 03/28/2013 02:49 PM, Anand Avati wrote:
> Yes, it should, based on the theory of how ext4 was generating the
> 63bits. But Jeff's test finds that the experiment is not matching the
> theory.

FWIW, I was able to re-run my test in between stuff related to That
Other Problem.  What seems to be happening is that we read correctly
until just after d_off 0x4000000000000000, then we suddenly wrap around
- not to the very first d_off we saw, but to a pretty early one (e.g.
0x0041b6340689a32e).  This is all on a single brick, BTW, so it's pretty
easy to line up the back-end and front-end d_off values which match
perfectly up to this point.

I haven't had a chance to ponder what this all means and debug it
further.  Hopefully I'll be able to do so soon, but I figured I'd
mention it in case something about those numbers rang a bell.


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