From: Kevin Corry <kevcorry@us.ibm.com>
To: linux-kernel@vger.kernel.org
Subject: Re: device-mapper: fix TB stripe data corruption
Date: Fri, 21 Jan 2005 15:12:45 -0600
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Cc: Benjamin LaHaise <bcrl@kvack.org>, Alasdair G Kergon <agk@redhat.com>,
       Andrew Morton <akpm@osdl.org>
References: <20050121181203.GI10195@agk.surrey.redhat.com> <20050121203354.GC2265@kvack.org>
In-Reply-To: <20050121203354.GC2265@kvack.org>
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On Friday 21 January 2005 2:33 pm, Benjamin LaHaise wrote:
> On Fri, Jan 21, 2005 at 06:12:03PM +0000, Alasdair G Kergon wrote:
> > Missing cast thought to cause data corruption on devices with stripes >
> > ~1TB.
>
> Why not make chunk a sector_t?

We have to take a mod of the chunk value and the number of stripes (which can 
be a non-power-of-2, so a shift won't work). It's been my understanding that 
you couldn't mod a 64-bit value with a 32-bit value in the kernel. Just to be 
sure, I've changed "chunk" to a sector_t and recompiled, and get the 
following error:

  MODPOST
*** Warning: "__udivdi3" [drivers/md/dm-mod.ko] undefined!
*** Warning: "__umoddi3" [drivers/md/dm-mod.ko] undefined!

-- 
Kevin Corry
kevcorry@us.ibm.com
http://evms.sourceforge.net/
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