linux-ext4 - Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO

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Date:	Wed, 16 Apr 2014 12:43:09 +0200 (CEST)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
cc:	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-man@...r.kernel.org, linux-ext4@...r.kernel.org,
	tytso@....edu, linux-fsdevel@...r.kernel.org, xfs@....sgi.com
Subject: Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO_RANGE flag for
 fallocate

On Tue, 15 Apr 2014, Christoph Hellwig wrote:

> Date: Tue, 15 Apr 2014 23:36:18 -0700
> From: Christoph Hellwig <hch@...radead.org>
> To: Lukas Czerner <lczerner@...hat.com>
> Cc: Michael Kerrisk <mtk.manpages@...il.com>, linux-man@...r.kernel.org,
>     linux-ext4@...r.kernel.org, tytso@....edu, linux-fsdevel@...r.kernel.org,
>     xfs@....sgi.com
> Subject: Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO_RANGE flag for
>     fallocate
> 
> On Mon, Feb 17, 2014 at 04:08:17PM +0100, Lukas Czerner wrote:
> > Introduce new FALLOC_FL_ZERO_RANGE flag for fallocate. This has the same
> > functionality as xfs ioctl XFS_IOC_ZERO_RANGE.
> 
> Lukas, can you please also send a man page update for
> FALLOC_FL_ZERO_RANGE now that is has been merged?

Right, I'll do that.

Thanks!
-Lukas

> 
> > 
> > It can be used to convert a range of file to zeros preferably without
> > issuing data IO. Blocks should be preallocated for the regions that span
> > holes in the file, and the entire range is preferable converted to
> > unwritten extents - even though file system may choose to zero out the
> > extent or do whatever which will result in reading zeros from the range
> > while the range remains allocated for the file.
> > 
> > This can be also used to preallocate blocks past EOF in the same way as
> > with fallocate. Flag FALLOC_FL_KEEP_SIZE which should cause the inode
> > size to remain the same.
> > 
> > You can test this feature yourself using xfstests, of fallocate(1) however
> > you'll need patches for util_linux, xfsprogs and xfstests which you
> > can find here:
> > 
> > http://people.redhat.com/lczerner/zero_range/
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