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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07206C433F5 for ; Fri, 18 Mar 2022 23:48:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6A0616B0071; Fri, 18 Mar 2022 19:48:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6766F8D0002; Fri, 18 Mar 2022 19:48:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4A2BE8D0001; Fri, 18 Mar 2022 19:48:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0129.hostedemail.com [216.40.44.129]) by kanga.kvack.org (Postfix) with ESMTP id 3B8D76B0071 for ; Fri, 18 Mar 2022 19:48:57 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id E364718222A01 for ; Fri, 18 Mar 2022 23:48:56 +0000 (UTC) X-FDA: 79259149872.27.AF11187 Received: from NAM11-CO1-obe.outbound.protection.outlook.com (mail-co1nam11on2055.outbound.protection.outlook.com [40.107.220.55]) by imf14.hostedemail.com (Postfix) with ESMTP id 364C910000F for ; Fri, 18 Mar 2022 23:48:56 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=oSTDWUEmHduuMJlB5yurUEk2x8pTZ15CDfiIuFrMXkoePXiwtr6NJQ6gx1rNzrfrOW9kl7sPP//tFSrHXXLRVwnGiz2tjZSSH7KR43z9w4xLd5R2XgGA/MN/ILukNd65uebxOEcGJCF5leLTfTkcBXvOqXa6tmM7toa7i1nv0ivmrYyJMQETmK9yJN4lQ/ZIV9MqucC1Jnw9SjWb7PFb+p4hpDhKD824CUhFO5LXpkj+SwaEnsqYWmFzmq1QZUji2cd++rP974jDpw5MyxInq7BCzJgURPCvL6yEOVwoiGd45g5weZLnUGstH4Zu7rQCKKALT3/y2Rcx3uPVP4sgXg== 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-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=cJEROmUPUvsvhDSxwqNd2B9U+F5kopWhN2vLJ8cddAw=; b=RWkh421rjtj80vSigq1ZQwekNoVlm4S0UH4BWhg4zkvZ6xFHaeJiKDINEaMUqCltLyQ+lpDDO16u8vzS6mgrxwTgTpsfetLHxSBZFG7RHDsqGKKUbZNt7WERn2fpivexxIReWTRRg2+8f6fkvzwsDnkL10QsHZaVM3N5zGbH5zLKvoxHT3peZdR6nkIDLqCJKgvGOiEcBp3I+T6UWV0VSDTFL8SYMU1d4m3P7s9nV6fwPIrItAR1+JR+5AXDEu4McRxTzVs/OOcVo5WgTka3hY4iHkbQ3OL2PgG9VUmBx1kv3twg6sZivLtap3/+GVHjatRKictmXIHImEnC+5hiYQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; 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=cJEROmUPUvsvhDSxwqNd2B9U+F5kopWhN2vLJ8cddAw=; b=AlNIV3cirsgoLNdk3cBhn7LcNAI8fgBjOF/tG3B0YqyysRxzBD3blzWmT2IER/fAoSqOU+LDeU5xZpj5ocdg3sahteW9XzJqHUGkWW6LrpBoe1QugbxmX+QJyZ3Tl1e3FuffTn27GsAPSp5JLCbFEefgH6FX0r3QrUtvA4ltIzvybk0514365ev0yZkiAkz2hduqDQr3JTaqkWH/KxjXywfCwQgN4kqxb/RC6skXHi9TM8aLRPxSl+60bYx1QE0W0icehAJ8Fzw9L0aIABFVQldyIKznxmx8MJmjRQ8RoEAcFE1+t6ztLE9vDbY1CuVjvRheUBeuWVc6qfgUR1ULDQ== Received: from SN6PR12MB2607.namprd12.prod.outlook.com (2603:10b6:805:6d::30) by BYAPR12MB3511.namprd12.prod.outlook.com (2603:10b6:a03:132::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5081.18; Fri, 18 Mar 2022 23:48:54 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by SN6PR12MB2607.namprd12.prod.outlook.com (2603:10b6:805:6d::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5081.15; Fri, 18 Mar 2022 23:48:51 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::11a0:970a:4c24:c70c]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::11a0:970a:4c24:c70c%5]) with mapi id 15.20.5081.018; Fri, 18 Mar 2022 23:48:51 +0000 Date: Fri, 18 Mar 2022 20:48:50 -0300 From: Jason Gunthorpe To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Andrew Morton , Hugh Dickins , Linus Torvalds , David Rientjes , Shakeel Butt , John Hubbard , Mike Kravetz , Mike Rapoport , Yang Shi , "Kirill A . Shutemov" , Matthew Wilcox , Vlastimil Babka , Jann Horn , Michal Hocko , Nadav Amit , Rik van Riel , Roman Gushchin , Andrea Arcangeli , Peter Xu , Donald Dutile , Christoph Hellwig , Oleg Nesterov , Jan Kara , Liang Zhang , Pedro Gomes , Oded Gabbay , Catalin Marinas , Will Deacon , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , linux-mm@kvack.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org Subject: Re: [PATCH v1 0/7] mm: COW fixes part 3: reliable GUP R/W FOLL_GET of anonymous pages Message-ID: <20220318234850.GD11336@nvidia.com> References: <20220315141837.137118-1-david@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220315141837.137118-1-david@redhat.com> X-ClientProxiedBy: BL0PR01CA0035.prod.exchangelabs.com (2603:10b6:208:71::48) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: edaf932c-7fe5-4aa3-62a0-08da0939da98 X-MS-TrafficTypeDiagnostic: SN6PR12MB2607:EE_|BYAPR12MB3511:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:SN6PR12MB2607.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(4636009)(366004)(33656002)(8936002)(2906002)(7416002)(6506007)(5660300002)(83380400001)(508600001)(6512007)(7406005)(6486002)(4744005)(38100700002)(4326008)(86362001)(8676002)(6916009)(54906003)(66946007)(66556008)(316002)(66476007)(26005)(186003)(2616005)(36756003)(1076003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?0svhnVVmeSO7srKs6+JxRk/rBoZxOrfZzib6M0qnAT4RxFLB5748GmZQvEXk?= =?us-ascii?Q?zhQ4AY6Bw1VL9tEroMP6P/BXOfM5RnP40oBz8BEzfUAp6uzh3zTzrP8mqb/I?= =?us-ascii?Q?bheO6iGolZixsiukRByxZ+cFjxaAr1vOK7cI4qH8cRK8O10ph2deWIYc6oaG?= =?us-ascii?Q?QmdZZaXRwdroXgxv8b54v/xzs9N9W4/rWwAbNJivPnikprUnjodefWkb9ImU?= =?us-ascii?Q?cDuLqbw3LedtWRvIa4N6DcxhwsT4AXMBaPT1oMRrfEh5h3EHVh5UqZngTr3X?= =?us-ascii?Q?gJU9qcmYBXLHj4qZH8PxGFD+5aINETHQUb25cWF1wt2+e2aNm53TIJpmBy/3?= =?us-ascii?Q?g2EVLUeCiFAPgdUM8qvIOUhOYvg9u3mIAB05T+YpcXgFxPzizp/WlbRKTrwT?= =?us-ascii?Q?hv7mi2hu3rZAX7h7KEBys2GJWuceUuHPrLtEPPs+agmfDCV652KLR7gVqZSv?= =?us-ascii?Q?Nz2WW9jL0ko25lPNkhE9P7f8fP8eEIZwXJaSz2H0b42L+oX6jfARA5nogf+L?= =?us-ascii?Q?P9ekYZDgRWdv5Oswv9zwDUN/BDGtL6sDz4Qwu7q2Sw6ai8fcXq/KiPMlDt7P?= =?us-ascii?Q?7xiJUrJAaE9UNFCzFkM8FPoo6lZDBS7MYqaBoe++uqh/1NM8iIofEOnReKYq?= =?us-ascii?Q?U5kEwmBIp/YSLO2Xcngc6RzzyOj/MYBJR+qxFdfhaBTkj0TIe/9sFfmv+7j4?= =?us-ascii?Q?PtVkIJD5aSSrnYQERrYE/WLbHzDvH9Yjv0JgNSduBPZykZnHTDO5VGNvDYY+?= =?us-ascii?Q?5f2VOqJ9F/NBijs5wJZRSoXMNKAWxNZxUNY20XEEeWOOp+bt8q8Hdlr/epEF?= =?us-ascii?Q?K2slnRNq5nAZin8kX0n0z7L1CY+ajqFhBOVlfmsBdhoM1MwuVpPnIfYXlT2/?= =?us-ascii?Q?nmnQ5UMRoOPPSfYpLWIyXI1DCKG73dFZlmBmf9Gyv0jlfoZ99tTKAY8ixbOd?= =?us-ascii?Q?C2lKp1ydgpGQnkbAIHYUnsSmDLDkWpS4iVLhTkNAyI0kHoU2fTj0m8b70bLV?= =?us-ascii?Q?r1irgy2VASXBs7voss+OQ+z1K5Y3zO/tym6AsxnL1nzr+Xtn8I3x/ioXyLT7?= =?us-ascii?Q?zphrvgabrse9e1KRtGBh0xuoL3AOegvy9iuHQeg2NOJeriNuwkdtTC0aj1xq?= =?us-ascii?Q?r+9DwbSgKARKhsm54ccc5wFC8Uz6qTyIaRgtmKGUrpGit+6afvtYaxuJvMUg?= =?us-ascii?Q?WooZoHqx6FeRPh4elETA52HMJovyjq+/lHGSi9dVd2arZvazrMX2VXiFdPMy?= =?us-ascii?Q?5Qh68PtuQD5tNm1BUny0Z9U1O8yBCdOXWpHjcFCKM6V98huOvSfuWnATrzMC?= =?us-ascii?Q?+hS8B75ZSeo++IuTOww6lufbuFe2CnDlr9surcG8Nohqu90R8PdQ8k19K7Tx?= =?us-ascii?Q?ebzoNqGpWkdp4q4wFXlZ2EQ+17pAcRwA+IPRdl6yUbTdFv9z0MlHvx8oO2AV?= =?us-ascii?Q?ritXUNnLjcnGc1qH//+bS3mz/I2oIjfS?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: edaf932c-7fe5-4aa3-62a0-08da0939da98 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Mar 2022 23:48:51.4207 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: n7VkHIwGEJaP6dqrcGbKSTIkuf01Dx8luXYetrH0Mkjf2+tg6rbvEcbP8SV8viXU X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB3511 X-Rspamd-Queue-Id: 364C910000F X-Rspam-User: Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=AlNIV3ci; dmarc=pass (policy=reject) header.from=nvidia.com; spf=none (imf14.hostedemail.com: domain of jgg@nvidia.com has no SPF policy when checking 40.107.220.55) smtp.mailfrom=jgg@nvidia.com X-Stat-Signature: m1yur663uurmtiyx17jttuskh1ir7dxg X-Rspamd-Server: rspam04 X-HE-Tag: 1647647336-884190 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 15, 2022 at 03:18:30PM +0100, David Hildenbrand wrote: > This is just the natural follow-up of part 2, that will also further > reduce "wrong COW" on the swapin path, for example, when we cannot remove > a page from the swapcache due to concurrent writeback, or if we have two > threads faulting on the same swapped-out page. Fixing O_DIRECT is just a > nice side-product :) I know I would benefit alot from a description of the swap specific issue a bit more. Most of this message talks about clear_refs which I do understand a bit better. Is this talking about what happens after a page gets swapped back in? eg the exclusive bit is missing when the page is recreated? Otherwise nothing stood out to me here, but I know almost nothing about swap. Thanks, Jason