From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de ([213.95.11.211]:47791 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752057AbeADIQb (ORCPT ); Thu, 4 Jan 2018 03:16:31 -0500 Date: Thu, 4 Jan 2018 09:16:29 +0100 From: Christoph Hellwig Subject: Re: [PATCH v4 01/18] mm, dax: introduce pfn_t_special() Message-ID: <20180104081629.GB2548@lst.de> References: <151407695916.38751.2866053440557472361.stgit@dwillia2-desk3.amr.corp.intel.com> <151407696622.38751.4716967585354728059.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <151407696622.38751.4716967585354728059.stgit@dwillia2-desk3.amr.corp.intel.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Dan Williams Cc: akpm@linux-foundation.org, jack@suse.cz, linux-nvdimm@lists.01.org, Benjamin Herrenschmidt , Heiko Carstens , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Paul Mackerras , Michael Ellerman , Martin Schwidefsky , ross.zwisler@linux.intel.com, hch@lst.de On Sat, Dec 23, 2017 at 04:56:06PM -0800, Dan Williams wrote: > In support of removing the VM_MIXEDMAP indication from DAX VMAs, > introduce pfn_t_special() for drivers to indicate that _PAGE_SPECIAL > should be used for DAX ptes. This also helps identify drivers like > dccssblk that only want to use DAX in a read-only fashion without > get_user_pages() support. > > Ideally we could delete axonram and dcssblk DAX support, but if we need > to keep it better make it explicit that axonram and dcssblk only support > a sub-set of DAX due to missing _PAGE_DEVMAP support. I'd suggest to just delete it for now. If the powerpc and S/390 people have an interest in it they should resurrect it properly and fully.