From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0961C43141 for ; Wed, 13 Nov 2019 22:59:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87AD4206E3 for ; Wed, 13 Nov 2019 22:59:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="mYe+MJkx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727031AbfKMW7t (ORCPT ); Wed, 13 Nov 2019 17:59:49 -0500 Received: from hqemgate15.nvidia.com ([216.228.121.64]:13052 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726755AbfKMW7o (ORCPT ); Wed, 13 Nov 2019 17:59:44 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 13 Nov 2019 14:59:43 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 13 Nov 2019 14:59:43 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 13 Nov 2019 14:59:43 -0800 Received: from [10.2.160.107] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 13 Nov 2019 22:59:43 +0000 Subject: Re: [PATCH v4 04/23] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages To: Dan Williams CC: Andrew Morton , Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Christoph Hellwig , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Magnus Karlsson , "Mauro Carvalho Chehab" , Michael Ellerman , Michal Hocko , Mike Kravetz , "Paul Mackerras" , Shuah Khan , Vlastimil Babka , , Maling list - DRI developers , KVM list , , Linux Doc Mailing List , linux-fsdevel , , "Linux-media@vger.kernel.org" , linux-rdma , linuxppc-dev , Netdev , Linux MM , LKML , Ralph Campbell References: <20191113042710.3997854-1-jhubbard@nvidia.com> <20191113042710.3997854-5-jhubbard@nvidia.com>

<00148078-1795-da3e-916e-3ae2dcdd553d@nvidia.com> From: John Hubbard X-Nvconfidentiality: public Message-ID: <8b887222-a1b4-c5ce-527a-5a6f2a73f943@nvidia.com> Date: Wed, 13 Nov 2019 14:56:58 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1573685983; bh=+Rmtc3S/dpjDCjZWKcpDoRZBPDTDBQ2pKKlWpjZisAo=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=mYe+MJkxrgNR137Q2ejzje6pRuep2M18oTZCivJor/Aq8akkqynarSLzze5gBAR6e Qbgg3D7fCX2h5Zp1bm8UCD5jTXu5RgNW/1wytp5sIWhpcH1/XVit7/Hqo1FuECTgjG jaeg32K4uRKA3UWevFbdUUXyjiUNrk/AfZUXltrSNK7fGabRHXeRaGFfre96i3rq7X ouT4NLlcMG8uUv2YW1+St8ZRhZhMfIq0xvEzPkblzu397MrZASgjNbz6jsR8uW1MwV 7mOV3InoZ3RXAMS6XnUTdXbtUPhzTvW8KfaZYgbYIJ5ILNS37evrPk9qlwTKM1SE3y Yu1anxljvu1OQ== Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 11/13/19 2:55 PM, Dan Williams wrote: > On Wed, Nov 13, 2019 at 2:49 PM John Hubbard wrote: >> >> On 11/13/19 2:00 PM, Dan Williams wrote: >> ... >>>> Ugh, when did all this HMM specific manipulation sneak into the >>>> generic ZONE_DEVICE path? It used to be gated by pgmap type with its >>>> own put_zone_device_private_page(). For example it's certainly >>>> unnecessary and might be broken (would need to check) to call >>>> mem_cgroup_uncharge() on a DAX page. ZONE_DEVICE users are not a >>>> monolith and the HMM use case leaks pages into code paths that DAX >>>> explicitly avoids. >>> >>> It's been this way for a while and I did not react previously, >>> apologies for that. I think __ClearPageActive, __ClearPageWaiters, and >>> mem_cgroup_uncharge, belong behind a device-private conditional. The >>> history here is: >>> >>> Move some, but not all HMM specifics to hmm_devmem_free(): >>> 2fa147bdbf67 mm, dev_pagemap: Do not clear ->mapping on final put >>> >>> Remove the clearing of mapping since no upstream consumers needed it: >>> b7a523109fb5 mm: don't clear ->mapping in hmm_devmem_free >>> >>> Add it back in once an upstream consumer arrived: >>> 7ab0ad0e74f8 mm/hmm: fix ZONE_DEVICE anon page mapping reuse >>> >>> We're now almost entirely free of ->page_free callbacks except for >>> that weird nouveau case, can that FIXME in nouveau_dmem_page_free() >>> also result in killing the ->page_free() callback altogether? In the >>> meantime I'm proposing a cleanup like this: >> >> >> OK, assuming this is acceptable (no obvious problems jump out at me, >> and we can also test it with HMM), then how would you like to proceed, as >> far as patches go: add such a patch as part of this series here, or as a >> stand-alone patch either before or after this series? Or something else? >> And did you plan on sending it out as such? > > I think it makes sense to include it in your series since you're > looking to refactor the implementation. I can send you one based on > current linux-next as a lead-in cleanup before the refactor. Does that > work for you? > That would be perfect! >> >> Also, the diffs didn't quite make it through intact to my "git apply", so >> I'm re-posting the diff in hopes that this time it survives: > > Apologies for that. For quick "how about this" patch examples, I just > copy and paste into gmail and it sometimes clobbers it. > No problem at all, I do the same thing and *usually* it works. ha. And as you say, it's good enough for discussions. thanks, -- John Hubbard NVIDIA