From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de ([213.95.11.211]:50634 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753598AbdHXQj1 (ORCPT ); Thu, 24 Aug 2017 12:39:27 -0400 Date: Thu, 24 Aug 2017 18:39:25 +0200 From: Christoph Hellwig Subject: Re: [PATCH v6 4/5] fs, xfs: introduce MAP_DIRECT for creating block-map-atomic file ranges Message-ID: <20170824163925.GA28503@lst.de> References: <150353211413.5039.5228914877418362329.stgit@dwillia2-desk3.amr.corp.intel.com> <150353213655.5039.7662200155640827407.stgit@dwillia2-desk3.amr.corp.intel.com> <20170824161152.GB27591@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Dan Williams Cc: Christoph Hellwig , Andrew Morton , Jan Kara , "Darrick J. Wong" , Linux API , "linux-nvdimm@lists.01.org" , Dave Chinner , "linux-kernel@vger.kernel.org" , linux-xfs@vger.kernel.org, Linux MM , Jeff Moyer , Alexander Viro , Andy Lutomirski , linux-fsdevel , Ross Zwisler , xen-devel@lists.xen.org On Thu, Aug 24, 2017 at 09:31:17AM -0700, Dan Williams wrote: > External agent is a DMA device, or a hypervisor like Xen. In the DMA > case perhaps we can use the fcntl lease mechanism, I'll investigate. > In the Xen case it actually would need to use fiemap() to discover the > physical addresses that back the file to setup their M2P tables. > Here's the discussion where we discovered that physical address > dependency: > > https://lists.xen.org/archives/html/xen-devel/2017-04/msg00419.html fiemap does not work to discover physical addresses. If they want to do anything involving physical address they will need a kernel driver.