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Shutemov" To: Larry Bassel Cc: mike.kravetz@oracle.com, willy@infradead.org, dan.j.williams@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org Subject: Re: [PATCH, RFC 2/2] Implement sharing/unsharing of PMDs for FS/DAX Message-ID: <20190612020749.sjpuquzxrprkalfy@box> References: <1557417933-15701-1-git-send-email-larry.bassel@oracle.com> <1557417933-15701-3-git-send-email-larry.bassel@oracle.com> <20190514130147.2pk2xx32aiomm57b@box> <20190524160711.GF19025@ubuette> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190524160711.GF19025@ubuette> User-Agent: NeoMutt/20180716 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, May 24, 2019 at 09:07:11AM -0700, Larry Bassel wrote: > Again, I don't think this can happen in DAX. The only sharing allowed > is for FS/DAX/2MiB pagesize. Hm. I still don't follow. How do you guarantee that DAX actually allocated continues space for the file on backing storage and you can map it with PMD page? I believe you don't have such guarantee. -- Kirill A. Shutemov