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Date: Wed, 13 Jul 2016 19:47:16 -0700
From: Christoph Hellwig <hch@infradead.org>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Omar Sandoval <osandov@osandov.com>, linux-btrfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: FIDEDUPERANGE with src_length == 0
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 <20160713052643.GD13625@birch.djwong.org>
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On Tue, Jul 12, 2016 at 10:26:43PM -0700, Darrick J. Wong wrote:
> It's a shortcut that we're introducing in the upcoming XFS implementation,
> since it shares the same back end as clone/clonerange, which both have
> this behavior.

We will have to preserve the existing btrfs semantics when reusing the
ioctl number.