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Wong" Cc: Christoph Hellwig , Dave Chinner , Jerome Glisse , 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190426144507.GB178347@magnolia> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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..).