linux-kernel - Re: [LSF/MM TOPIC] Direct block mapping through fs for device

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Message-ID: <20190426144702.GA31264@infradead.org>
Date:   Fri, 26 Apr 2019 07:47:02 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Dave Chinner <david@...morbit.com>,
        Jerome Glisse <jglisse@...hat.com>,
        lsf-pc@...ts.linux-foundation.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [LSF/MM TOPIC] Direct block mapping through fs for device

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..).