From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO_RANGE flag for fallocate
Date: Tue, 15 Apr 2014 23:36:18 -0700
Message-ID: <20140416063618.GA12498@infradead.org>
References: <1392649703-10772-1-git-send-email-lczerner@redhat.com>
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Cc: linux-man@vger.kernel.org, tytso@mit.edu, xfs@oss.sgi.com,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
To: Lukas Czerner <lczerner@redhat.com>
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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?

> 
> 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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