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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 E00ACC433E0 for ; Fri, 12 Mar 2021 04:43:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD79964F94 for ; Fri, 12 Mar 2021 04:43:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232227AbhCLEnW (ORCPT ); Thu, 11 Mar 2021 23:43:22 -0500 Received: from mail-dm6nam12on2071.outbound.protection.outlook.com ([40.107.243.71]:37548 "EHLO NAM12-DM6-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S231844AbhCLEmy (ORCPT ); Thu, 11 Mar 2021 23:42:54 -0500 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Ba9YDpVj0NoLxL1uiSod4GaSKUxgfGwxYEO7VhsAQzbVsDEZQ4eV3uUOPwU/zQE0Abg47D6PS1gKAe8sOjQeIoJVoYpkC0Br9jDckGXkUcxoDQOuSR7Ium5WuVyAwFgd5rRjgPdiAHMHSWngL2YD53Xsgm+por79SeCihLKGG9Witl0H186tzB8+3WDw713PQFBkXzuyk5GUU5Sm9eMUrq2S2uJ+H4wjGqtdWrtGd8TblyrsLlIRNmD89w6Fd1gRmJT9u/xMO0fKOdGQqBuTM6zMmaS3T+Dks4VC2OIaCkLG3sL4hKFa33mV99PdffMXWAiGcn89pICbAWfmlUOn+g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=dTK0VPwwkhLyGgUfm/5MUrWbjzo2X8rxMBnm7Z0Pbns=; b=GRUnR8juX0PDp2MEUVjoXO+YNqykY9SQj7EZ30KKBcfDCkXA0ktItYJEqiyQpfbFMNtaLUyUYExYE7hVdGE6iiV0FIRx856ybbUptGe6MbpDQyUNCgNmkUtbUAZhmNMb9u+PAfO1/r89KLPyBgEf11/z03VFEoXNcYU8F2eZDXEo1hlvxGEeKKM2O1wTTwIp6jPHCVLbR24xXX0km8+AzC2N3DABCsDnbxmtQx5oYXDP86Bf04Q1Xn9lI1/Q47Sob1dH1JK9Js9oN8iSRLpOXYopnccw9BaXMSy3E8mjOSPvHJ9m7GxKix5qhu8MeXyVkwkjrBo36eM9MA8FhqOktQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 216.228.112.34) smtp.rcpttodomain=vger.kernel.org smtp.mailfrom=nvidia.com; dmarc=pass (p=none sp=none pct=100) action=none header.from=nvidia.com; dkim=none (message not signed); arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=dTK0VPwwkhLyGgUfm/5MUrWbjzo2X8rxMBnm7Z0Pbns=; b=JKNqqEqntWbJrQKaF+3BthDC8FnakQrPeZc0k+EXqPVTb7BH4i7DGGDpS27iq1P6WCCyco4nnddyPsQ5MQh5M/3RPFo/Iy/KcwyZ884qNeSxbH1ZPgLG0i4nQM8UP8tnFe1mYDMCp+dN+BoIH5nOSBv+UTbwc4AIFg9TOrA3i0ydKgSBoKWrTpXM25eJWIcMadEOQ3w8Zd9STZNwKQ17P3ZRSadphgYhGZx66mO6z39d1hzXoW+1BMhPfpRGsDd2wzeLeYsYs22f30BPj4cduFblhgbijzG+QdfQCVPzNT6css9kWoZ7zz3j684RqPfbPMNUSV0IiTFTafAYktx2dA== Received: from BN6PR13CA0011.namprd13.prod.outlook.com (2603:10b6:404:10a::21) by BYAPR12MB3173.namprd12.prod.outlook.com (2603:10b6:a03:13d::26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3912.30; Fri, 12 Mar 2021 04:42:50 +0000 Received: from BN8NAM11FT043.eop-nam11.prod.protection.outlook.com (2603:10b6:404:10a:cafe::28) by BN6PR13CA0011.outlook.office365.com (2603:10b6:404:10a::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3955.11 via Frontend Transport; Fri, 12 Mar 2021 04:42:50 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 216.228.112.34) smtp.mailfrom=nvidia.com; vger.kernel.org; dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 216.228.112.34 as permitted sender) receiver=protection.outlook.com; client-ip=216.228.112.34; helo=mail.nvidia.com; Received: from mail.nvidia.com (216.228.112.34) by BN8NAM11FT043.mail.protection.outlook.com (10.13.177.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.3933.31 via Frontend Transport; Fri, 12 Mar 2021 04:42:49 +0000 Received: from nvdebian.localnet (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 12 Mar 2021 04:42:46 +0000 From: Alistair Popple To: Matthew Wilcox CC: , , , , , , , , , , Subject: Re: [PATCH v5 1/8] mm: Remove special swap entry functions Date: Fri, 12 Mar 2021 15:42:44 +1100 Message-ID: <2167899.OcvonqYCbN@nvdebian> In-Reply-To: <20210309124949.GJ3479805@casper.infradead.org> References: <20210309121505.23608-1-apopple@nvidia.com> <20210309121505.23608-2-apopple@nvidia.com> <20210309124949.GJ3479805@casper.infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: fd51258b-0988-4bfa-b5ae-08d8e5114a7e X-MS-TrafficTypeDiagnostic: BYAPR12MB3173: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:7219; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.34;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid03.nvidia.com;CAT:NONE;SFS:(4636009)(346002)(376002)(39860400002)(136003)(396003)(46966006)(36840700001)(36906005)(54906003)(7416002)(426003)(82310400003)(5660300002)(316002)(356005)(36860700001)(6916009)(7636003)(83380400001)(86362001)(47076005)(82740400003)(33716001)(336012)(186003)(478600001)(34020700004)(70206006)(26005)(70586007)(8936002)(2906002)(9576002)(4326008)(9686003)(8676002)(16526019);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Mar 2021 04:42:49.8408 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fd51258b-0988-4bfa-b5ae-08d8e5114a7e X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT043.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB3173 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, 9 March 2021 11:49:49 PM AEDT Matthew Wilcox wrote: > On Tue, Mar 09, 2021 at 11:14:58PM +1100, Alistair Popple wrote: > > -static inline struct page *migration_entry_to_page(swp_entry_t entry) > > -{ > > - struct page *p = pfn_to_page(swp_offset(entry)); > > - /* > > - * Any use of migration entries may only occur while the > > - * corresponding page is locked > > - */ > > - BUG_ON(!PageLocked(compound_head(p))); > > - return p; > > -} > > > +static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry) > > +{ > > + struct page *p = pfn_to_page(swp_offset(entry)); > > + > > + /* > > + * Any use of migration entries may only occur while the > > + * corresponding page is locked > > + */ > > + BUG_ON(is_migration_entry(entry) && !PageLocked(compound_head(p))); > > + > > + return p; > > +} > > I appreciate you're only moving this code, but PageLocked includes an > implicit compound_head(): I am happy to clean this up at the same time. It did seem a odd when I added it and I had meant to follow up on it some more. > 1. __PAGEFLAG(Locked, locked, PF_NO_TAIL) > > 2. #define __PAGEFLAG(uname, lname, policy) \ > TESTPAGEFLAG(uname, lname, policy) \ > > 3. #define TESTPAGEFLAG(uname, lname, policy) \ > static __always_inline int Page##uname(struct page *page) \ > { return test_bit(PG_##lname, &policy(page, 0)->flags); } > > 4. #define PF_NO_TAIL(page, enforce) ({ \ > VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ > PF_POISONED_CHECK(compound_head(page)); }) > > 5. #define PF_POISONED_CHECK(page) ({ \ > VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \ > page; }) > > > This macrology isn't easy to understand the first time you read it (nor, > indeed, the tenth time), so let me decode it: > > Substitute 5 into 4 and remove irrelevancies: > > 6. #define PF_NO_TAIL(page, enforce) compound_head(page) > > Expand 1 in 2: > > 7. TESTPAGEFLAG(Locked, locked, PF_NO_TAIL) > > Expand 7 in 3: > > 8. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &PF_NO_TAIL(page, 0)->flags); } > > Expand 6 in 8: > > 9. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &compound_head(page)->flags); } Thanks for expanding that out, makes sense and matches my reading as well. Will remove the redundant compound_head() call in PageLocked() for the next revision. > (in case it's not clear, compound_head() is idempotent. that is: > f(f(a)) == f(a)) 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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 76104C433DB for ; Fri, 12 Mar 2021 04:42:56 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 2387964F94 for ; Fri, 12 Mar 2021 04:42:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2387964F94 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=nouveau-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id BE8076E110; Fri, 12 Mar 2021 04:42:55 +0000 (UTC) Received: from NAM12-DM6-obe.outbound.protection.outlook.com (mail-dm6nam12on2041.outbound.protection.outlook.com [40.107.243.41]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3B43D6E110; Fri, 12 Mar 2021 04:42:54 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Ba9YDpVj0NoLxL1uiSod4GaSKUxgfGwxYEO7VhsAQzbVsDEZQ4eV3uUOPwU/zQE0Abg47D6PS1gKAe8sOjQeIoJVoYpkC0Br9jDckGXkUcxoDQOuSR7Ium5WuVyAwFgd5rRjgPdiAHMHSWngL2YD53Xsgm+por79SeCihLKGG9Witl0H186tzB8+3WDw713PQFBkXzuyk5GUU5Sm9eMUrq2S2uJ+H4wjGqtdWrtGd8TblyrsLlIRNmD89w6Fd1gRmJT9u/xMO0fKOdGQqBuTM6zMmaS3T+Dks4VC2OIaCkLG3sL4hKFa33mV99PdffMXWAiGcn89pICbAWfmlUOn+g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=dTK0VPwwkhLyGgUfm/5MUrWbjzo2X8rxMBnm7Z0Pbns=; b=GRUnR8juX0PDp2MEUVjoXO+YNqykY9SQj7EZ30KKBcfDCkXA0ktItYJEqiyQpfbFMNtaLUyUYExYE7hVdGE6iiV0FIRx856ybbUptGe6MbpDQyUNCgNmkUtbUAZhmNMb9u+PAfO1/r89KLPyBgEf11/z03VFEoXNcYU8F2eZDXEo1hlvxGEeKKM2O1wTTwIp6jPHCVLbR24xXX0km8+AzC2N3DABCsDnbxmtQx5oYXDP86Bf04Q1Xn9lI1/Q47Sob1dH1JK9Js9oN8iSRLpOXYopnccw9BaXMSy3E8mjOSPvHJ9m7GxKix5qhu8MeXyVkwkjrBo36eM9MA8FhqOktQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 216.228.112.34) smtp.rcpttodomain=vger.kernel.org smtp.mailfrom=nvidia.com; dmarc=pass (p=none sp=none pct=100) action=none header.from=nvidia.com; dkim=none (message not signed); arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=dTK0VPwwkhLyGgUfm/5MUrWbjzo2X8rxMBnm7Z0Pbns=; b=JKNqqEqntWbJrQKaF+3BthDC8FnakQrPeZc0k+EXqPVTb7BH4i7DGGDpS27iq1P6WCCyco4nnddyPsQ5MQh5M/3RPFo/Iy/KcwyZ884qNeSxbH1ZPgLG0i4nQM8UP8tnFe1mYDMCp+dN+BoIH5nOSBv+UTbwc4AIFg9TOrA3i0ydKgSBoKWrTpXM25eJWIcMadEOQ3w8Zd9STZNwKQ17P3ZRSadphgYhGZx66mO6z39d1hzXoW+1BMhPfpRGsDd2wzeLeYsYs22f30BPj4cduFblhgbijzG+QdfQCVPzNT6css9kWoZ7zz3j684RqPfbPMNUSV0IiTFTafAYktx2dA== Received: from BN6PR13CA0011.namprd13.prod.outlook.com (2603:10b6:404:10a::21) by BYAPR12MB3173.namprd12.prod.outlook.com (2603:10b6:a03:13d::26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3912.30; Fri, 12 Mar 2021 04:42:50 +0000 Received: from BN8NAM11FT043.eop-nam11.prod.protection.outlook.com (2603:10b6:404:10a:cafe::28) by BN6PR13CA0011.outlook.office365.com (2603:10b6:404:10a::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3955.11 via Frontend Transport; Fri, 12 Mar 2021 04:42:50 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 216.228.112.34) smtp.mailfrom=nvidia.com; vger.kernel.org; dkim=none (message not signed) header.d=none; vger.kernel.org; dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 216.228.112.34 as permitted sender) receiver=protection.outlook.com; client-ip=216.228.112.34; helo=mail.nvidia.com; Received: from mail.nvidia.com (216.228.112.34) by BN8NAM11FT043.mail.protection.outlook.com (10.13.177.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.3933.31 via Frontend Transport; Fri, 12 Mar 2021 04:42:49 +0000 Received: from nvdebian.localnet (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 12 Mar 2021 04:42:46 +0000 From: Alistair Popple To: Matthew Wilcox Date: Fri, 12 Mar 2021 15:42:44 +1100 Message-ID: <2167899.OcvonqYCbN@nvdebian> In-Reply-To: <20210309124949.GJ3479805@casper.infradead.org> References: <20210309121505.23608-1-apopple@nvidia.com> <20210309121505.23608-2-apopple@nvidia.com> <20210309124949.GJ3479805@casper.infradead.org> MIME-Version: 1.0 X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: fd51258b-0988-4bfa-b5ae-08d8e5114a7e X-MS-TrafficTypeDiagnostic: BYAPR12MB3173: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:7219; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: WFlhR2qpeQYMK2jDBMXa3uHStYOSv/TSPUvby5N/pt+Rr07nrhSZZ3QnxyHQ8gj+sNTh4sI92wBaI8KT5om9/AfwUdNAHJnwOA92H9AAmlf65crh4EJBkIdbwCzZDZWfP+IhHNavU9F4gExlbJG8jECEQTwQxjRTwqOCEGKXK01zd95wcJLnEy/009lGRBCazaQj7B/TlV9pnc4GthnDFW7g+WjEKjxIaPHubrdlTuCSDlVuS8NJHssD4ybMHHSbPQEw5mK0egYjE95oRg5f38OwYVeBfe9gjs1aKAY1WwE3MzN7G0RyvXujAsAz4JHF9jKUGpL0vaPRP7IYO8KqXXwzRADbXNf8Ld0SnbZnAHf368UbIA2hVHZ5H1OIGu+gh7DiLBT2O0iGsyFT6OIOwd42Vh7d/0JZrm15eRKBvviWT1FbHu72VMqEh1t2Sye6mUe/UcILeIaITjz8XmKAKWRVnSmxZWMYaBegXGOG/udLmOobVMnB/sfvbVxxnnJaELIn76mZmS87lzhuFdoHo/bYRF0tAf2dj/D7YnG1tZbxXx1+yDQh3wp6VEaj76D5RHpjQHvvDJpBIUQfqc3YejcSTIi+5L0g2VkR8xCUeprcMek9zLkTuZzIZJnagszzW3Ekvoco1J4jfpcYbZsdD6XDiZuc/juUoYVoA12POo+tmqkwZm4e04mmm0XlieXq X-Forefront-Antispam-Report: CIP:216.228.112.34; CTRY:US; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:mail.nvidia.com; PTR:schybrid03.nvidia.com; CAT:NONE; SFS:(4636009)(346002)(376002)(39860400002)(136003)(396003)(46966006)(36840700001)(36906005)(54906003)(7416002)(426003)(82310400003)(5660300002)(316002)(356005)(36860700001)(6916009)(7636003)(83380400001)(86362001)(47076005)(82740400003)(33716001)(336012)(186003)(478600001)(34020700004)(70206006)(26005)(70586007)(8936002)(2906002)(9576002)(4326008)(9686003)(8676002)(16526019); DIR:OUT; SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Mar 2021 04:42:49.8408 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fd51258b-0988-4bfa-b5ae-08d8e5114a7e X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a; Ip=[216.228.112.34]; Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT043.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB3173 Subject: Re: [Nouveau] [PATCH v5 1/8] mm: Remove special swap entry functions X-BeenThere: nouveau@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Nouveau development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: rcampbell@nvidia.com, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-mm@kvack.org, bskeggs@redhat.com, akpm@linux-foundation.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: nouveau-bounces@lists.freedesktop.org Sender: "Nouveau" On Tuesday, 9 March 2021 11:49:49 PM AEDT Matthew Wilcox wrote: > On Tue, Mar 09, 2021 at 11:14:58PM +1100, Alistair Popple wrote: > > -static inline struct page *migration_entry_to_page(swp_entry_t entry) > > -{ > > - struct page *p = pfn_to_page(swp_offset(entry)); > > - /* > > - * Any use of migration entries may only occur while the > > - * corresponding page is locked > > - */ > > - BUG_ON(!PageLocked(compound_head(p))); > > - return p; > > -} > > > +static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry) > > +{ > > + struct page *p = pfn_to_page(swp_offset(entry)); > > + > > + /* > > + * Any use of migration entries may only occur while the > > + * corresponding page is locked > > + */ > > + BUG_ON(is_migration_entry(entry) && !PageLocked(compound_head(p))); > > + > > + return p; > > +} > > I appreciate you're only moving this code, but PageLocked includes an > implicit compound_head(): I am happy to clean this up at the same time. It did seem a odd when I added it and I had meant to follow up on it some more. > 1. __PAGEFLAG(Locked, locked, PF_NO_TAIL) > > 2. #define __PAGEFLAG(uname, lname, policy) \ > TESTPAGEFLAG(uname, lname, policy) \ > > 3. #define TESTPAGEFLAG(uname, lname, policy) \ > static __always_inline int Page##uname(struct page *page) \ > { return test_bit(PG_##lname, &policy(page, 0)->flags); } > > 4. #define PF_NO_TAIL(page, enforce) ({ \ > VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ > PF_POISONED_CHECK(compound_head(page)); }) > > 5. #define PF_POISONED_CHECK(page) ({ \ > VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \ > page; }) > > > This macrology isn't easy to understand the first time you read it (nor, > indeed, the tenth time), so let me decode it: > > Substitute 5 into 4 and remove irrelevancies: > > 6. #define PF_NO_TAIL(page, enforce) compound_head(page) > > Expand 1 in 2: > > 7. TESTPAGEFLAG(Locked, locked, PF_NO_TAIL) > > Expand 7 in 3: > > 8. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &PF_NO_TAIL(page, 0)->flags); } > > Expand 6 in 8: > > 9. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &compound_head(page)->flags); } Thanks for expanding that out, makes sense and matches my reading as well. Will remove the redundant compound_head() call in PageLocked() for the next revision. > (in case it's not clear, compound_head() is idempotent. that is: > f(f(a)) == f(a)) _______________________________________________ Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau 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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 8F4EAC433E6 for ; Fri, 12 Mar 2021 04:42:58 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 5AE5464EBB for ; Fri, 12 Mar 2021 04:42:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5AE5464EBB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 29F296F417; Fri, 12 Mar 2021 04:42:56 +0000 (UTC) Received: from NAM12-DM6-obe.outbound.protection.outlook.com (mail-dm6nam12on2041.outbound.protection.outlook.com [40.107.243.41]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3B43D6E110; Fri, 12 Mar 2021 04:42:54 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Ba9YDpVj0NoLxL1uiSod4GaSKUxgfGwxYEO7VhsAQzbVsDEZQ4eV3uUOPwU/zQE0Abg47D6PS1gKAe8sOjQeIoJVoYpkC0Br9jDckGXkUcxoDQOuSR7Ium5WuVyAwFgd5rRjgPdiAHMHSWngL2YD53Xsgm+por79SeCihLKGG9Witl0H186tzB8+3WDw713PQFBkXzuyk5GUU5Sm9eMUrq2S2uJ+H4wjGqtdWrtGd8TblyrsLlIRNmD89w6Fd1gRmJT9u/xMO0fKOdGQqBuTM6zMmaS3T+Dks4VC2OIaCkLG3sL4hKFa33mV99PdffMXWAiGcn89pICbAWfmlUOn+g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=dTK0VPwwkhLyGgUfm/5MUrWbjzo2X8rxMBnm7Z0Pbns=; b=GRUnR8juX0PDp2MEUVjoXO+YNqykY9SQj7EZ30KKBcfDCkXA0ktItYJEqiyQpfbFMNtaLUyUYExYE7hVdGE6iiV0FIRx856ybbUptGe6MbpDQyUNCgNmkUtbUAZhmNMb9u+PAfO1/r89KLPyBgEf11/z03VFEoXNcYU8F2eZDXEo1hlvxGEeKKM2O1wTTwIp6jPHCVLbR24xXX0km8+AzC2N3DABCsDnbxmtQx5oYXDP86Bf04Q1Xn9lI1/Q47Sob1dH1JK9Js9oN8iSRLpOXYopnccw9BaXMSy3E8mjOSPvHJ9m7GxKix5qhu8MeXyVkwkjrBo36eM9MA8FhqOktQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 216.228.112.34) smtp.rcpttodomain=vger.kernel.org smtp.mailfrom=nvidia.com; dmarc=pass (p=none sp=none pct=100) action=none header.from=nvidia.com; dkim=none (message not signed); arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=dTK0VPwwkhLyGgUfm/5MUrWbjzo2X8rxMBnm7Z0Pbns=; b=JKNqqEqntWbJrQKaF+3BthDC8FnakQrPeZc0k+EXqPVTb7BH4i7DGGDpS27iq1P6WCCyco4nnddyPsQ5MQh5M/3RPFo/Iy/KcwyZ884qNeSxbH1ZPgLG0i4nQM8UP8tnFe1mYDMCp+dN+BoIH5nOSBv+UTbwc4AIFg9TOrA3i0ydKgSBoKWrTpXM25eJWIcMadEOQ3w8Zd9STZNwKQ17P3ZRSadphgYhGZx66mO6z39d1hzXoW+1BMhPfpRGsDd2wzeLeYsYs22f30BPj4cduFblhgbijzG+QdfQCVPzNT6css9kWoZ7zz3j684RqPfbPMNUSV0IiTFTafAYktx2dA== Received: from BN6PR13CA0011.namprd13.prod.outlook.com (2603:10b6:404:10a::21) by BYAPR12MB3173.namprd12.prod.outlook.com (2603:10b6:a03:13d::26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3912.30; Fri, 12 Mar 2021 04:42:50 +0000 Received: from BN8NAM11FT043.eop-nam11.prod.protection.outlook.com (2603:10b6:404:10a:cafe::28) by BN6PR13CA0011.outlook.office365.com (2603:10b6:404:10a::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3955.11 via Frontend Transport; Fri, 12 Mar 2021 04:42:50 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 216.228.112.34) smtp.mailfrom=nvidia.com; vger.kernel.org; dkim=none (message not signed) header.d=none; vger.kernel.org; dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 216.228.112.34 as permitted sender) receiver=protection.outlook.com; client-ip=216.228.112.34; helo=mail.nvidia.com; Received: from mail.nvidia.com (216.228.112.34) by BN8NAM11FT043.mail.protection.outlook.com (10.13.177.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.3933.31 via Frontend Transport; Fri, 12 Mar 2021 04:42:49 +0000 Received: from nvdebian.localnet (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 12 Mar 2021 04:42:46 +0000 From: Alistair Popple To: Matthew Wilcox Subject: Re: [PATCH v5 1/8] mm: Remove special swap entry functions Date: Fri, 12 Mar 2021 15:42:44 +1100 Message-ID: <2167899.OcvonqYCbN@nvdebian> In-Reply-To: <20210309124949.GJ3479805@casper.infradead.org> References: <20210309121505.23608-1-apopple@nvidia.com> <20210309121505.23608-2-apopple@nvidia.com> <20210309124949.GJ3479805@casper.infradead.org> MIME-Version: 1.0 X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: fd51258b-0988-4bfa-b5ae-08d8e5114a7e X-MS-TrafficTypeDiagnostic: BYAPR12MB3173: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:7219; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.34; CTRY:US; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:mail.nvidia.com; PTR:schybrid03.nvidia.com; CAT:NONE; SFS:(4636009)(346002)(376002)(39860400002)(136003)(396003)(46966006)(36840700001)(36906005)(54906003)(7416002)(426003)(82310400003)(5660300002)(316002)(356005)(36860700001)(6916009)(7636003)(83380400001)(86362001)(47076005)(82740400003)(33716001)(336012)(186003)(478600001)(34020700004)(70206006)(26005)(70586007)(8936002)(2906002)(9576002)(4326008)(9686003)(8676002)(16526019); DIR:OUT; SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Mar 2021 04:42:49.8408 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fd51258b-0988-4bfa-b5ae-08d8e5114a7e X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a; Ip=[216.228.112.34]; Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT043.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB3173 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: rcampbell@nvidia.com, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com, bskeggs@redhat.com, jhubbard@nvidia.com, akpm@linux-foundation.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tuesday, 9 March 2021 11:49:49 PM AEDT Matthew Wilcox wrote: > On Tue, Mar 09, 2021 at 11:14:58PM +1100, Alistair Popple wrote: > > -static inline struct page *migration_entry_to_page(swp_entry_t entry) > > -{ > > - struct page *p = pfn_to_page(swp_offset(entry)); > > - /* > > - * Any use of migration entries may only occur while the > > - * corresponding page is locked > > - */ > > - BUG_ON(!PageLocked(compound_head(p))); > > - return p; > > -} > > > +static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry) > > +{ > > + struct page *p = pfn_to_page(swp_offset(entry)); > > + > > + /* > > + * Any use of migration entries may only occur while the > > + * corresponding page is locked > > + */ > > + BUG_ON(is_migration_entry(entry) && !PageLocked(compound_head(p))); > > + > > + return p; > > +} > > I appreciate you're only moving this code, but PageLocked includes an > implicit compound_head(): I am happy to clean this up at the same time. It did seem a odd when I added it and I had meant to follow up on it some more. > 1. __PAGEFLAG(Locked, locked, PF_NO_TAIL) > > 2. #define __PAGEFLAG(uname, lname, policy) \ > TESTPAGEFLAG(uname, lname, policy) \ > > 3. #define TESTPAGEFLAG(uname, lname, policy) \ > static __always_inline int Page##uname(struct page *page) \ > { return test_bit(PG_##lname, &policy(page, 0)->flags); } > > 4. #define PF_NO_TAIL(page, enforce) ({ \ > VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ > PF_POISONED_CHECK(compound_head(page)); }) > > 5. #define PF_POISONED_CHECK(page) ({ \ > VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \ > page; }) > > > This macrology isn't easy to understand the first time you read it (nor, > indeed, the tenth time), so let me decode it: > > Substitute 5 into 4 and remove irrelevancies: > > 6. #define PF_NO_TAIL(page, enforce) compound_head(page) > > Expand 1 in 2: > > 7. TESTPAGEFLAG(Locked, locked, PF_NO_TAIL) > > Expand 7 in 3: > > 8. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &PF_NO_TAIL(page, 0)->flags); } > > Expand 6 in 8: > > 9. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &compound_head(page)->flags); } Thanks for expanding that out, makes sense and matches my reading as well. Will remove the redundant compound_head() call in PageLocked() for the next revision. > (in case it's not clear, compound_head() is idempotent. that is: > f(f(a)) == f(a)) _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alistair Popple Date: Fri, 12 Mar 2021 04:42:44 +0000 Subject: Re: [PATCH v5 1/8] mm: Remove special swap entry functions Message-Id: <2167899.OcvonqYCbN@nvdebian> List-Id: References: <20210309121505.23608-1-apopple@nvidia.com> <20210309121505.23608-2-apopple@nvidia.com> <20210309124949.GJ3479805@casper.infradead.org> In-Reply-To: <20210309124949.GJ3479805@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Matthew Wilcox Cc: linux-mm@kvack.org, nouveau@lists.freedesktop.org, bskeggs@redhat.com, akpm@linux-foundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, dri-devel@lists.freedesktop.org, jhubbard@nvidia.com, rcampbell@nvidia.com, jglisse@redhat.com On Tuesday, 9 March 2021 11:49:49 PM AEDT Matthew Wilcox wrote: > On Tue, Mar 09, 2021 at 11:14:58PM +1100, Alistair Popple wrote: > > -static inline struct page *migration_entry_to_page(swp_entry_t entry) > > -{ > > - struct page *p = pfn_to_page(swp_offset(entry)); > > - /* > > - * Any use of migration entries may only occur while the > > - * corresponding page is locked > > - */ > > - BUG_ON(!PageLocked(compound_head(p))); > > - return p; > > -} > > > +static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry) > > +{ > > + struct page *p = pfn_to_page(swp_offset(entry)); > > + > > + /* > > + * Any use of migration entries may only occur while the > > + * corresponding page is locked > > + */ > > + BUG_ON(is_migration_entry(entry) && !PageLocked(compound_head(p))); > > + > > + return p; > > +} > > I appreciate you're only moving this code, but PageLocked includes an > implicit compound_head(): I am happy to clean this up at the same time. It did seem a odd when I added it and I had meant to follow up on it some more. > 1. __PAGEFLAG(Locked, locked, PF_NO_TAIL) > > 2. #define __PAGEFLAG(uname, lname, policy) \ > TESTPAGEFLAG(uname, lname, policy) \ > > 3. #define TESTPAGEFLAG(uname, lname, policy) \ > static __always_inline int Page##uname(struct page *page) \ > { return test_bit(PG_##lname, &policy(page, 0)->flags); } > > 4. #define PF_NO_TAIL(page, enforce) ({ \ > VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ > PF_POISONED_CHECK(compound_head(page)); }) > > 5. #define PF_POISONED_CHECK(page) ({ \ > VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \ > page; }) > > > This macrology isn't easy to understand the first time you read it (nor, > indeed, the tenth time), so let me decode it: > > Substitute 5 into 4 and remove irrelevancies: > > 6. #define PF_NO_TAIL(page, enforce) compound_head(page) > > Expand 1 in 2: > > 7. TESTPAGEFLAG(Locked, locked, PF_NO_TAIL) > > Expand 7 in 3: > > 8. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &PF_NO_TAIL(page, 0)->flags); } > > Expand 6 in 8: > > 9. static __always_inline int PageLocked(struct page *page) > { return test_bit(PG_locked, &compound_head(page)->flags); } Thanks for expanding that out, makes sense and matches my reading as well. Will remove the redundant compound_head() call in PageLocked() for the next revision. > (in case it's not clear, compound_head() is idempotent. that is: > f(f(a)) = f(a))