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From: Dave Chinner <david@fromorbit.com>
To: "Linda A. Walsh" <lkml@tlinx.org>
Cc: PXXdraig Brady <P@draigBrady.com>,
	LKML <linux-kernel@vger.kernel.org>, xfs-oss <xfs@oss.sgi.com>
Subject: Re: write 'O_DIRECT' file w/odd amount of data: desirable result?
Date: Thu, 24 Feb 2011 20:26:25 +1100	[thread overview]
Message-ID: <20110224092625.GA3087@dastard> (raw)
In-Reply-To: <4D654C2E.2000703@tlinx.org>

On Wed, Feb 23, 2011 at 10:04:30AM -0800, Linda A. Walsh wrote:
> 
> 
> FWIW -- xfs-oss, included as 'last line' was of minor interest; known bug on
> this kernel?:
> Linux Ishtar 2.6.35.7-T610-Vanilla-1 #2 SMP PREEMPT Mon Oct 11
> 17:19:41 PDT 2010 x86_64 x86_64 x86_64 GNU/Linux
....
> Of *SIGNIFICANT* note.  In trying to create an empty file of the size
> used, from scratch, using 'xfs_mkfile', I got an error:
> 
> > xfs_mkfile 5776419696 testfile
> pwrite64: Invalid argument

xfs_mkfile does not create an "empty" file. It creates a file that
is full of zeros.

iAnd you're getting that erro because:

5776419696 / 512 = 11,282,069.7188

the last write is not a multiple of the sector size and xfs_mkfile
uses direct IO. It has always failed when you try to do this. If you
want to create allocated, zeroed files of abitrary size, then use:

xfs_io -f -c "truncate $size" -c "resvsp 0 $size" $filename

to preallocate it. it'll be much, much faster than xfs_mkfile.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: "Linda A. Walsh" <lkml@tlinx.org>
Cc: PXXdraig Brady <P@draigBrady.com>,
	LKML <linux-kernel@vger.kernel.org>, xfs-oss <xfs@oss.sgi.com>
Subject: Re: write 'O_DIRECT' file w/odd amount of data: desirable result?
Date: Thu, 24 Feb 2011 20:26:25 +1100	[thread overview]
Message-ID: <20110224092625.GA3087@dastard> (raw)
In-Reply-To: <4D654C2E.2000703@tlinx.org>

On Wed, Feb 23, 2011 at 10:04:30AM -0800, Linda A. Walsh wrote:
> 
> 
> FWIW -- xfs-oss, included as 'last line' was of minor interest; known bug on
> this kernel?:
> Linux Ishtar 2.6.35.7-T610-Vanilla-1 #2 SMP PREEMPT Mon Oct 11
> 17:19:41 PDT 2010 x86_64 x86_64 x86_64 GNU/Linux
....
> Of *SIGNIFICANT* note.  In trying to create an empty file of the size
> used, from scratch, using 'xfs_mkfile', I got an error:
> 
> > xfs_mkfile 5776419696 testfile
> pwrite64: Invalid argument

xfs_mkfile does not create an "empty" file. It creates a file that
is full of zeros.

iAnd you're getting that erro because:

5776419696 / 512 = 11,282,069.7188

the last write is not a multiple of the sector size and xfs_mkfile
uses direct IO. It has always failed when you try to do this. If you
want to create allocated, zeroed files of abitrary size, then use:

xfs_io -f -c "truncate $size" -c "resvsp 0 $size" $filename

to preallocate it. it'll be much, much faster than xfs_mkfile.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  parent reply	other threads:[~2011-02-24  9:23 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-23  4:30 write 'O_DIRECT' file w/odd amount of data: desirable result? Linda Walsh
2011-02-23 10:34 ` Pádraig Brady
2011-02-23 18:04   ` Linda A. Walsh
2011-02-24  1:18     ` Pádraig Brady
2011-02-24  1:18       ` Pádraig Brady
2011-02-24  9:26     ` Dave Chinner [this message]
2011-02-24  9:26       ` Dave Chinner
2011-03-02  2:27       ` RFE kernel option to do the desirable thing, w/regards to 'O_DIRECT' and mis-aligned data Linda Walsh
2011-03-02  2:27         ` Linda Walsh

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