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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 482B6C33CB1 for ; Thu, 16 Jan 2020 09:38:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E5EC20748 for ; Thu, 16 Jan 2020 09:38:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DExRcwvR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731217AbgAPJiS (ORCPT ); Thu, 16 Jan 2020 04:38:18 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:47780 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726864AbgAPJiR (ORCPT ); Thu, 16 Jan 2020 04:38:17 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=/fZtSw8YSFU2Bly7v5Q7x01aJLXfW/w2Sao1/9HMkcI=; b=DExRcwvRtFXUvspwe2EK1pvbk toOxyW/Rr7rvJL9Uo35exr8Cq2wCUokVKVlfAtn576Uwh6C0dDY+T/FqZ4x+sYv+8BDucArp3y1Zx NC96wmTc5QNReYms4V9DkpZ9WP5G7mGeRlC5SUBjQZBvlUl97PM9jLHyv9Mn7tevIOXaJa4Q5iXde bXS+39JbBJRccdS9LFTo+FwnQG+xGELB+IzFC6BcqMnYvzn4K0YbBX5iL1zc87io0r9xxv4FP2Te6 65YEWF3mg8LdQoUzSr2qBy1recVwExQ2okF4Q/NYnSTv1qsmEBA+XVmZNwmYaFEgRtYH8E7r4VJTs MW9dAK1TQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1is1aS-00035V-O1; Thu, 16 Jan 2020 09:37:12 +0000 Date: Thu, 16 Jan 2020 01:37:12 -0800 From: Christoph Hellwig To: John Hubbard Cc: Christoph Hellwig , Andrew Morton , Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?iso-8859-1?B?Suly9G1l?= Glisse , "Kirill A . Shutemov" , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , bpf@vger.kernel.org, dri-devel@lists.freedesktop.org, kvm@vger.kernel.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-mm@kvack.org, LKML , Christoph Hellwig Subject: Re: [PATCH v12 04/22] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages Message-ID: <20200116093712.GA11011@infradead.org> References: <20200107224558.2362728-1-jhubbard@nvidia.com> <20200107224558.2362728-5-jhubbard@nvidia.com> <20200115152306.GA19546@infradead.org> <4707f191-86f8-db4a-c3de-0a84b415b658@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4707f191-86f8-db4a-c3de-0a84b415b658@nvidia.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Jan 15, 2020 at 01:19:41PM -0800, John Hubbard wrote: > On 1/15/20 7:23 AM, Christoph Hellwig wrote: > ... > > > > I'm really not sold on this scheme. Note that I think it is > > particularly bad, but it also doesn't seem any better than what > > we had before, and it introduced quite a bit more code. > > > > Hi Christoph, > > All by itself, yes. But the very next patch (which needs a little > rework for other reasons, so not included here) needs to reuse some of > these functions within __unpin_devmap_managed_user_page(): Well, then combine it with the series that actually does the change. Also my vaguely recollection is that we had some idea on how to get rid of the off by one refcounting for the zone device pages, which would be a much better outcome. 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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 893BDC33CB1 for ; Thu, 16 Jan 2020 09:40:21 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3A0F420748 for ; Thu, 16 Jan 2020 09:40:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DExRcwvR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A0F420748 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47yzh30PcgzDqc6 for ; Thu, 16 Jan 2020 20:40:19 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=bombadil.srs.infradead.org (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org; envelope-from=batv+e120a4276ddc5f5fb55f+5989+infradead.org+hch@bombadil.srs.infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20170209 header.b=DExRcwvR; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47yzdl4mYszDqS5 for ; Thu, 16 Jan 2020 20:38:19 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=/fZtSw8YSFU2Bly7v5Q7x01aJLXfW/w2Sao1/9HMkcI=; b=DExRcwvRtFXUvspwe2EK1pvbk toOxyW/Rr7rvJL9Uo35exr8Cq2wCUokVKVlfAtn576Uwh6C0dDY+T/FqZ4x+sYv+8BDucArp3y1Zx NC96wmTc5QNReYms4V9DkpZ9WP5G7mGeRlC5SUBjQZBvlUl97PM9jLHyv9Mn7tevIOXaJa4Q5iXde bXS+39JbBJRccdS9LFTo+FwnQG+xGELB+IzFC6BcqMnYvzn4K0YbBX5iL1zc87io0r9xxv4FP2Te6 65YEWF3mg8LdQoUzSr2qBy1recVwExQ2okF4Q/NYnSTv1qsmEBA+XVmZNwmYaFEgRtYH8E7r4VJTs MW9dAK1TQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1is1aS-00035V-O1; Thu, 16 Jan 2020 09:37:12 +0000 Date: Thu, 16 Jan 2020 01:37:12 -0800 From: Christoph Hellwig To: John Hubbard Subject: Re: [PATCH v12 04/22] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages Message-ID: <20200116093712.GA11011@infradead.org> References: <20200107224558.2362728-1-jhubbard@nvidia.com> <20200107224558.2362728-5-jhubbard@nvidia.com> <20200115152306.GA19546@infradead.org> <4707f191-86f8-db4a-c3de-0a84b415b658@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4707f191-86f8-db4a-c3de-0a84b415b658@nvidia.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , Jan Kara , kvm@vger.kernel.org, linux-doc@vger.kernel.org, David Airlie , Dave Chinner , dri-devel@lists.freedesktop.org, LKML , linux-mm@kvack.org, Paul Mackerras , linux-kselftest@vger.kernel.org, Ira Weiny , Christoph Hellwig , Jonathan Corbet , linux-rdma@vger.kernel.org, Christoph Hellwig , Jason Gunthorpe , Vlastimil Babka , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , linux-media@vger.kernel.org, Shuah Khan , linux-block@vger.kernel.org, =?iso-8859-1?B?Suly9G1l?= Glisse , Al Viro , "Kirill A . Shutemov" , Dan Williams , Mauro Carvalho Chehab , bpf@vger.kernel.org, Magnus Karlsson , Jens Axboe , netdev@vger.kernel.org, Alex Williamson , Daniel Vetter , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S . Miller" , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Jan 15, 2020 at 01:19:41PM -0800, John Hubbard wrote: > On 1/15/20 7:23 AM, Christoph Hellwig wrote: > ... > > > > I'm really not sold on this scheme. Note that I think it is > > particularly bad, but it also doesn't seem any better than what > > we had before, and it introduced quite a bit more code. > > > > Hi Christoph, > > All by itself, yes. But the very next patch (which needs a little > rework for other reasons, so not included here) needs to reuse some of > these functions within __unpin_devmap_managed_user_page(): Well, then combine it with the series that actually does the change. Also my vaguely recollection is that we had some idea on how to get rid of the off by one refcounting for the zone device pages, which would be a much better outcome.