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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH] mm: Take a page reference when removing device exclusive entries Content-Language: en-US To: Matthew Wilcox , Alistair Popple CC: , Andrew Morton , "Ralph Campbell" , , References: <20230328021434.292971-1-apopple@nvidia.com> From: John Hubbard In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.126.231.37] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1NAM11FT009:EE_|CH3PR12MB7594:EE_ X-MS-Office365-Filtering-Correlation-Id: d8fe3ff9-8830-489a-f7d9-08db30080857 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:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230028)(4636009)(39860400002)(346002)(396003)(136003)(376002)(451199021)(40470700004)(46966006)(36840700001)(8936002)(31686004)(2906002)(47076005)(336012)(83380400001)(426003)(2616005)(34020700004)(36860700001)(41300700001)(31696002)(86362001)(36756003)(40460700003)(7636003)(5660300002)(82740400003)(356005)(6636002)(478600001)(40480700001)(54906003)(8676002)(70586007)(70206006)(4326008)(4744005)(16526019)(82310400005)(186003)(53546011)(110136005)(316002)(26005)(16576012)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Mar 2023 03:45:25.9974 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d8fe3ff9-8830-489a-f7d9-08db30080857 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT009.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB7594 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 3/28/23 20:16, Matthew Wilcox wrote: ... >> + if (!get_page_unless_zero(vmf->page)) >> + return 0; > > From a folio point of view: what the hell are you doing here? Tail > pages don't have individual refcounts; all the refcounts are actually ohh, and I really should have caught that too. I plead spending too much time recently in a somewhat more driver-centric mindset, and failing to mentally shift gears properly for this case. Sorry for missing that! thanks, -- John Hubbard NVIDIA 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A2462C6FD18 for ; Wed, 29 Mar 2023 03:45:30 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id ECAB810E4CF; Wed, 29 Mar 2023 03:45:29 +0000 (UTC) Received: from NAM11-DM6-obe.outbound.protection.outlook.com (mail-dm6nam11on2055.outbound.protection.outlook.com [40.107.223.55]) by gabe.freedesktop.org (Postfix) with ESMTPS id 630D510E4B3 for ; Wed, 29 Mar 2023 03:45:28 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=PYpJPLuQPx92VGW1DY/E2VfJCq8SXPRQ1gpPNXxmRVeh5Ce72LCt4qpo0tpduLB8HU0lhN8qwOgn+xUzR/Y2AdNsADi2uIfAqgkFYVpiAbuBXUrmNl3kE7PChLTQkTx66eDCLiTN5jbx/XtP65GclNw+gs65vSyLF8TqxhCe+6+NmUb835dVM/AwlcQ/FiwRG8hSBWYo1nM5POLkFaCdoiIq5RU+Yp9E6YyUlJyXiKAPZmJGqTPApHqrl8cDJAUI3HX+hAYspF8SEk/ahAKSqhmmmdEki1xD34tqMT8JkV+9iiKcch+SFqdv2fBCEXmQ1l0hWQ4AM16rLzAE0va1sg== ARC-Message-Signature: i=1; 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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Content-Language: en-US To: Matthew Wilcox , Alistair Popple References: <20230328021434.292971-1-apopple@nvidia.com> From: John Hubbard In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.126.231.37] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1NAM11FT009:EE_|CH3PR12MB7594:EE_ X-MS-Office365-Filtering-Correlation-Id: d8fe3ff9-8830-489a-f7d9-08db30080857 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:216.228.117.160; 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Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT009.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB7594 Subject: Re: [Nouveau] [PATCH] mm: Take a page reference when removing device exclusive entries 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: linux-mm@kvack.org, Andrew Morton , Ralph Campbell , stable@vger.kernel.org, nouveau@lists.freedesktop.org Errors-To: nouveau-bounces@lists.freedesktop.org Sender: "Nouveau" On 3/28/23 20:16, Matthew Wilcox wrote: ... >> + if (!get_page_unless_zero(vmf->page)) >> + return 0; > > From a folio point of view: what the hell are you doing here? Tail > pages don't have individual refcounts; all the refcounts are actually ohh, and I really should have caught that too. I plead spending too much time recently in a somewhat more driver-centric mindset, and failing to mentally shift gears properly for this case. Sorry for missing that! thanks, -- John Hubbard NVIDIA