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Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO_RANGE flag for fallocate

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO_RANGE flag for fallocate
From: Lukáš Czerner <lczerner@xxxxxxxxxx>
Date: Wed, 16 Apr 2014 12:43:09 +0200 (CEST)
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>, linux-man@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, tytso@xxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140416063618.GA12498@xxxxxxxxxxxxx>
References: <1392649703-10772-1-git-send-email-lczerner@xxxxxxxxxx> <20140416063618.GA12498@xxxxxxxxxxxxx>
User-agent: Alpine 2.00 (LFD 1167 2008-08-23)
On Tue, 15 Apr 2014, Christoph Hellwig wrote:

> Date: Tue, 15 Apr 2014 23:36:18 -0700
> From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> To: Lukas Czerner <lczerner@xxxxxxxxxx>
> Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>, linux-man@xxxxxxxxxxxxxxx,
>     linux-ext4@xxxxxxxxxxxxxxx, tytso@xxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx,
>     xfs@xxxxxxxxxxx
> 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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