From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-x236.google.com (mail-ig0-x236.google.com [IPv6:2607:f8b0:4001:c05::236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id DD99F1A1A79 for ; Fri, 14 Aug 2015 09:40:52 +1000 (AEST) Received: by igbjg10 with SMTP id jg10so1776797igb.0 for ; Thu, 13 Aug 2015 16:40:50 -0700 (PDT) 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 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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/