Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754884AbbG0X0H (ORCPT ); Mon, 27 Jul 2015 19:26:07 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:36512 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754132AbbG0X0F (ORCPT ); Mon, 27 Jul 2015 19:26:05 -0400 MIME-Version: 1.0 In-Reply-To: <20150727051258.GB15836@lst.de> References: <20150725023649.8664.59145.stgit@dwillia2-desk3.amr.corp.intel.com> <20150725023842.8664.97620.stgit@dwillia2-desk3.amr.corp.intel.com> <20150726172527.GA29513@lst.de> <20150727051258.GB15836@lst.de> Date: Mon, 27 Jul 2015 16:26:03 -0700 Message-ID: Subject: Re: [PATCH v2 08/25] arch: introduce memremap() From: Dan Williams To: Christoph Hellwig Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-arch@vger.kernel.org, "Kani, Toshimitsu" , Arnd Bergmann , "linux-nvdimm@lists.01.org" , "linux-kernel@vger.kernel.org" , Russell King , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1366 Lines: 29 On Sun, Jul 26, 2015 at 10:12 PM, Christoph Hellwig wrote: > On Sun, Jul 26, 2015 at 10:49:39AM -0700, Dan Williams wrote: >> On Sun, Jul 26, 2015 at 10:25 AM, Christoph Hellwig wrote: >> > On Fri, Jul 24, 2015 at 10:38:42PM -0400, Dan Williams wrote: >> >> The behavior change to return NULL on an unsupported request is reserved >> >> for a later patch. >> > >> > Why? >> >> This is for drivers like pmem that care about the mapping type. For >> example, if pmem can't get a cache-enabled mapping it is potentially >> putting the write durability of the persistent media at risk. > > I understand that part, but the question is why the old behavior > is retained for now and only changed later. Oh, because all we have at this point is ioremap_cache() which silently falls back. It's not until the introduction of arch_memremp() where we update the arch code to break that behavior. That said, I think it may be beneficial to allow a fallback if the user cares. So maybe memremap() can call plain ioremap() if MEMREMAP_STRICT is not set and none of the other mapping types are satisfied. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/