linux-kernel - Re: [PATCH] Make div64_u64() precise on 32bit platforms

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Message-Id: <20101021122232.10d2d573.akpm@linux-foundation.org>
Date:	Thu, 21 Oct 2010 12:22:32 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Brian Behlendorf <behlendorf1@...l.gov>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Make div64_u64() precise on 32bit platforms

On Thu, 21 Oct 2010 20:12:20 +0200
Oleg Nesterov <oleg@...hat.com> wrote:

> Andrew, please drop
> 
> 	lib-div64c-document-that-div64_u64-is-not-precise-on-32bit-platforms.patch
> 
> On 10/21, Brian Behlendorf wrote:
> >
> > I think we should use your simpler version.  There's no good reason to
> > make this more complicated than it needs to be.  I haven't been able to
> > find a test case where your changes get the wrong result.
> 
> Great!
> 
> > From: Brian Behlendorf <behlendorf1@...l.gov>
> > Date: Thu, 5 Aug 2010 14:59:11 -0700
> > Subject: [PATCH] Fix div64_u64 for 32bit platforms
> >
> > The current implementation of div64_u64 for 32bit systems returns
> > an approximately correct result when the divisor exceeds 32bits.
> > Since doing 64bit division using 32bit hardware is a long since
> > solved problem we just use one of the existing proven methods.
> 
> Brian, you forgot to add your sob. Hopefully Andrew can add
> 
> 	Signed-off-by: Brian Behlendorf <behlendorf1@...l.gov>
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

OK..

Just to tie all this off, you originally said "We have a bug report
which blames div64_u64() on 32bit platforms.".  Where is that bug report?

Thanks.
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