From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) by kanga.kvack.org (Postfix) with ESMTP id 93EFF8E0002 for ; Tue, 15 Jan 2019 10:53:20 -0500 (EST) Received: by mail-qt1-f198.google.com with SMTP id 41so2688294qto.17 for ; Tue, 15 Jan 2019 07:53:20 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id j25si6516431qtn.303.2019.01.15.07.53.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Jan 2019 07:53:19 -0800 (PST) Subject: Re: [PATCH v2 0/9] mm: PG_reserved cleanups and documentation References: <20190114125903.24845-1-david@redhat.com> <20190115153839.GE26443@infradead.org> From: David Hildenbrand Message-ID: <447946ff-403a-6ca3-2958-688d28a82fce@redhat.com> Date: Tue, 15 Jan 2019 16:53:00 +0100 MIME-Version: 1.0 In-Reply-To: <20190115153839.GE26443@infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: linux-mm@kvack.org, Mark Rutland , Michal Hocko , CHANDAN VN , David Airlie , Benjamin Herrenschmidt , Bhupesh Sharma , Palmer Dabbelt , Heiko Carstens , Tony Luck , Stefan Agner , Michal Hocko , David Howells , Paul Mackerras , Michael Ellerman , linux-riscv@lists.infradead.org, Alexander Duyck , linux-s390@vger.kernel.org, Florian Fainelli , Vasily Gorbik , Logan Gunthorpe , Pavel Tatashin , Matthew Wilcox , AKASHI Takahiro , Geert Uytterhoeven , Catalin Marinas , Anthony Yznaga , Tobias Klauser , Laura Abbott , Fenghua Yu , Albert Ou , Kees Cook , Arnd Bergmann , Stephen Rothwell , Marc Zyngier , Will Deacon , Kristina Martsenko , linux-m68k@lists.linux-m68k.org, Dave Kleikamp , linux-mediatek@lists.infradead.org, Oleg Nesterov , Dan Williams , linux-arm-kernel@lists.infradead.org, Christophe Leroy , Matthias Brugger , Greg Kroah-Hartman , Randy Dunlap , linux-kernel@vger.kernel.org, Miles Chen , Mike Rapoport , James Morse , Souptick Joarder , Johannes Weiner , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Greg Hackmann On 15.01.19 16:38, Christoph Hellwig wrote: > On Mon, Jan 14, 2019 at 01:58:54PM +0100, David Hildenbrand wrote: >> Nothing major changed since the last version. I would be happy about >> additional ACKs. If there are no further comments, can this go via the >> mm-tree in one chunk? >> >> I was recently going over all users of PG_reserved. Short story: it is >> difficult and sometimes not really clear if setting/checking for >> PG_reserved is only a relict from the past. Easy to break things. I >> guess I now have a pretty good idea wh things are like that >> nowadays and how they evolved. > > Any reason you skipped > > drivers/gpu/drm/drm_pci.c:drm_pci_alloc() > > and > > drivers/gpu/drm/drm_scatter.c:drm_legacy_sg_alloc() > > which both look completely bogus as-is? > > In fact we should probably just try to kill them off as they have > very few users left. > I actually have patches lying around for these, however excluded them for now as I was not 100% sure about the implications ("Easy to break things"). Are you sure nobody in the system (especially somebody who does a PageReserved()) relies on this to identify e.g. MMIO pages? (e.g. ioremap on some archs, KVM code) (I am by far no DRM expert, but when I hear DMA, I tend to be careful) -- Thanks, David / dhildenb