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Date:   Fri, 26 Apr 2019 07:47:02 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     "Darrick J. Wong" <darrick.wong@oracle.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Dave Chinner <david@fromorbit.com>,
        Jerome Glisse <jglisse@redhat.com>,
        lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [LSF/MM TOPIC] Direct block mapping through fs for device
Message-ID: <20190426144702.GA31264@infradead.org>
References: <20190426013814.GB3350@redhat.com>
 <20190426062816.GG1454@dread.disaster.area>
 <20190426124553.GB12339@infradead.org>
 <20190426144507.GB178347@magnolia>
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On Fri, Apr 26, 2019 at 07:45:07AM -0700, Darrick J. Wong wrote:
> Hmmm, this lease interface still doesn't support COW, right?
> 
> (Right, xfs_pnfs.c bails out with -ENXIO for reflink files)

Yes, but that is because no one bothered to do the work.
pNFS/block and pNFS/scsi explicitly support a compatbile COW
scheme, it is just that no implemented it yet (at all I think,
not just for Linux..).