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Re: XFS status update for January 2011

To: Tao Ma <tm@xxxxxx>
Subject: Re: XFS status update for January 2011
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 14 Feb 2011 23:02:37 +1100
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <4D5890B6.2090105@xxxxxx>
References: <20110213184219.GA22792@xxxxxxxxxxxxx> <4D5890B6.2090105@xxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Mon, Feb 14, 2011 at 10:17:26AM +0800, Tao Ma wrote:
> Hi Christoph,
> On 02/14/2011 02:42 AM, Christoph Hellwig wrote:
> >On the 4th of January we saw the release of Linux 2.6.37, which contains a
> >large XFS update:
> >
> >     67 files changed, 1424 insertions(+), 1524 deletions(-)
> >
> >User visible changes are the new XFS_IOC_ZERO_RANGE ioctl which allows
> >to convert already allocated space into unwritten extents that return
> >zeros on a read,
> would you mind describing some scenario that this ioctl can be used. I am
> just wondering whether ocfs2 can implement it as well.

Zeroing a file without doing IO or having to punch out the blocks
already allocated to the file.

In this case, we had a couple of different people in cloud storage
land asking for such functionality to optimise record deletion
be avoiding disruption of their preallocated file layouts as a
punch-then-preallocate operation does.

If you you have some kind of use for it in ocfs2, then implementing
the XFS ioctl is not the correct thing to do - using the fallocate
patch I've had sitting around (since about 15min after creating the
XFS ioctl) is most likely the right way to proceed....


Dave Chinner

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