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Date: Thu, 29 Sep 2016 10:05:37 -0700
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 43/63] xfs: teach get_bmapx about shared extents and the
 CoW fork
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To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: david@fromorbit.com, linux-xfs@vger.kernel.org

On Tue, Sep 27, 2016 at 07:58:13PM -0700, Darrick J. Wong wrote:
> +#define BMV_IF_COWFORK		0x20	/* return CoW fork rather than data */

I think exposing an implementation detail like the COW fork that has
no on-disk equivalent is a bad idea and would feel much better if this
part of the patch was dropped.