Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754481AbbHMXky (ORCPT ); Thu, 13 Aug 2015 19:40:54 -0400 Received: from mail-ig0-f177.google.com ([209.85.213.177]:36891 "EHLO mail-ig0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752212AbbHMXkv (ORCPT ); Thu, 13 Aug 2015 19:40:51 -0400 MIME-Version: 1.0 In-Reply-To: <20150813143528.GC17183@lst.de> References: <1439363150-8661-1-git-send-email-hch@lst.de> <55CB3F47.3000902@plexistor.com> <20150813143528.GC17183@lst.de> From: Julian Calaby Date: Fri, 14 Aug 2015 09:40:30 +1000 Message-ID: Subject: Re: RFC: prepare for struct scatterlist entries without page backing To: Christoph Hellwig Cc: Boaz Harrosh , Linus Torvalds , axboe@kernel.dk, linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-nvdimm@ml01.01.org, David Howells , sparclinux , Hans-Christian Egtvedt , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, x86@kernel.org, David Woodhouse , =?UTF-8?Q?H=C3=A5vard_Skinnemoen?= , linux-xtensa@linux-xtensa.org, grundler@parisc-linux.org, Miao Steven , alex.williamson@redhat.com, linux-metag@vger.kernel.org, Michal Simek , linux-parisc@vger.kernel.org, vgupta@synopsys.com, "linux-kernel@vger.kernel.org" , linux-alpha@vger.kernel.org, Linux Media Mailing List , linuxppc-dev@lists.ozlabs.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: 1869 Lines: 46 Hi Christoph, On Fri, Aug 14, 2015 at 12:35 AM, Christoph Hellwig wrote: > On Thu, Aug 13, 2015 at 09:37:37AM +1000, Julian Calaby wrote: >> I.e. ~90% of this patch set seems to be just mechanically dropping >> BUG_ON()s and converting open coded stuff to use accessor functions >> (which should be macros or get inlined, right?) - and the remaining >> bit is not flushing if we don't have a physical page somewhere. > > Which is was 90%. By lines changed most actually is the diffs for > the cache flushing. I was talking in terms of changes made, not lines changed: by my recollection, about a third of the patches didn't touch flush calls and most of the lines changed looked like refactoring so that making the flush call conditional would be easier. I guess it smelled like you were doing lots of distinct changes in a single patch and I got my numbers wrong. >> Would it make sense to split this patch set into a few bits: one to >> drop all the useless BUG_ON()s, one to convert all the open coded >> stuff to accessor functions, then another to do the actual page-less >> sg stuff? > > Without the ifs the BUG_ON() actually are useful to assert we > never feed the sort of physical addresses we can't otherwise support, > so I don't think that part is doable. My point is that there's a couple of patches that only remove BUG_ON()s, which implies that for that particular driver it doesn't matter if there's a physical page or not, so therefore that code is purely "documentation". Thanks, -- Julian Calaby Email: julian.calaby@gmail.com Profile: http://www.google.com/profiles/julian.calaby/ -- 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/