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From: Benjamin LaHaise <bcrl@redhat.com>
To: Joel Becker <Joel.Becker@oracle.com>
Cc: Rob van Nieuwkerk <robn@verdi.et.tudelft.nl>,
	linux-kernel@vger.kernel.org
Subject: Re: O_DIRECT alignment requirements ?
Date: Wed, 9 Apr 2003 14:08:32 -0400	[thread overview]
Message-ID: <20030409140832.A4621@redhat.com> (raw)
In-Reply-To: <20030409154836.GA31739@ca-server1.us.oracle.com>; from Joel.Becker@oracle.com on Wed, Apr 09, 2003 at 08:48:36AM -0700

On Wed, Apr 09, 2003 at 08:48:36AM -0700, Joel Becker wrote:
> 	In 2.5, the alignment restrictions have been relaxed.  Your
> offset, buffer, and transfer size must all be aligned on the hardware
> sector size.  That is the output of BLKSSZGET against the block device,
> and is also what get_hardsect_size() returns in the kernel.  For almost
> all disks this number is 512b, so you can do O_DIRECT on 512b alignment
> for a raw disk or for an ext3 filesystem.  About the only thing that
> may not have a 512b hardware sector size is a CD-ROM.

Well, and SCSI devices configured to use 528 byte sectors and such...

		-ben
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      parent reply	other threads:[~2003-04-09 17:56 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-04-09 12:16 O_DIRECT alignment requirements ? Rob van Nieuwkerk
2003-04-09 15:48 ` Joel Becker
2003-04-09 16:53   ` Rob van Nieuwkerk
2003-04-09 17:59     ` Joel Becker
2003-04-09 19:15     ` Andrew Morton
2003-04-09 21:09       ` Rob van Nieuwkerk
2003-04-09 23:27         ` Joel Becker
2003-04-10 16:33           ` Rob van Nieuwkerk
2003-04-09 18:08   ` Benjamin LaHaise [this message]

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