From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from DM5PR21CU001.outbound.protection.outlook.com (mail-centralusazon11011007.outbound.protection.outlook.com [52.101.62.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6249B2874FE; Mon, 23 Feb 2026 15:22:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.62.7 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771860163; cv=fail; b=GM2KPLQ0paqonc1uQcS7NmRWHUpaKzUyyGnakNCA2tLoTPIEmHChGWxpyTNDAjSXluKnn9knc0KdI/SSjVfC36zfXRIennXFrBM1ZSBAO+nuElfNirnzO8zz8h+sL/xnoP3T2ICwmLpwLqRr8mQI2rPA1kHqvLAGvQB3ZRw0S3U= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771860163; c=relaxed/simple; bh=jKWwpiA4tn4S0F/L0gHj8WRjp0yCIkCm2d2dhJ8IEr8=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=Kh4+D2o6NclacW1Wy/tljPTzjB5DHTiKu/2rFLuTtlcTyxTF3vgfMh5YJI6sqWtNP1WIem10dgDLVQQfAWexObjoeCOFd0Ixnok9WCiRokcQKDA1mEDJqtygqWmJhWO0LMBc+0n5rnzqwXCMqmQLP+PUb5urpSkRpNC6rCcDAuk= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=1R8fHFBg; arc=fail smtp.client-ip=52.101.62.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="1R8fHFBg" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=gGsWoYQEn5BteuaHUdwewRBKmYId9br1Xf6oKr6/Zl7DWDjPheceNAH/A9GQtJN6sZ9ev0wVoAvBrSxJ1Yzz6kJIo4c/fDMqbm+OT3SxGkXhcCBZKJHgh1dPXXH8t30Otp5Poq5wVD+xj70R0PAFusrJi/vCRhZrMCE+f5BXYkNjpJ/iGqbSb1Z63MeTVeJem80sID8XT2VdGLhHpUxkXNbCh4I9ngrgTV5NWy0sJqXAFdu8cLZlsdxdYQMa15iOQb48gYJVG2/qXDUwqAM3Rlmcoh/kLgMBf01EJNZiOdARyYm5fGutnubM68UhwktWGUAWQcHVq19AXPcHnopfNQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; 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=1a8DOf85OXZZ9cRZWI2U5OsHQxBvst5ogD53MlLBsMc=; b=JSoLMdD4Az83v3RXlDrRqYALtLtGtQWY0Qi6ZNNn0jClzZh+tpcJb9Ymqw6eAF0+1DcRmMi3G9eJjkZMLr3iOdDa0VhW0HwYUwMm/Ld0y0EV8PhJdjGVVq5MRoycTj4ziqCyqL+EOTIEzhl9yK1FFpMgLSMIZesZh1fyw3othDVtgo/qI6EBmBdHViSU0mAoMKLbZ4F9rrq4dcPAKYNL262AwNUn8oAilgAK0zblPMp8pTWw3xqGQqv/ETQMvPiUDJ0AZqDiWly/qIWuHKBbr3A+7kT5+pdmQbhfMMEZasMc4PNtZqJ1+TQjKe3+RHlmWLWTxce+RlkWTLsL/4jXKw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1a8DOf85OXZZ9cRZWI2U5OsHQxBvst5ogD53MlLBsMc=; b=1R8fHFBgUVgxvXX/8n38SAQySgwHRMVByiGxuhLHkUcWANG+m5bqzIFlDRcX1vlm1yqVaC2efQZi/O9F//d12ZvHwscIAwdb9oCEvLEZ+BnIHvreo9BfmwtCa2cQEW3oe5zVdkXnXQmFm42uiKzxe2IbwIr57p/t6qLfjOHzST8= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) by PH0PR12MB7096.namprd12.prod.outlook.com (2603:10b6:510:21d::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9632.21; Mon, 23 Feb 2026 15:22:31 +0000 Received: from PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c]) by PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c%5]) with mapi id 15.20.9632.017; Mon, 23 Feb 2026 15:22:31 +0000 Message-ID: Date: Mon, 23 Feb 2026 16:22:17 +0100 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 00/11] Zero page->private when freeing pages To: "David Hildenbrand (Arm)" , Christoph Hellwig , Zi Yan Cc: linux-mm@kvack.org, Andrew Morton , linux-erofs@lists.ozlabs.org, linux-block@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Jason Xing , Yushan Zhou , "Masami Hiramatsu (Google)" , Vlastimil Babka , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Huang Rui , Matthew Auld , Matthew Brost , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jens Axboe , Christian Brauner , K Prateek Nayak , Davidlohr Bueso , Eric Sandeen , Greg Kroah-Hartman , =?UTF-8?Q?Arve_Hj=C3=B8nnev=C3=A5g?= , Todd Kjos , Carlos Llamas , Alice Ryhl , Damien Le Moal , Johannes Thumshirn , Dennis Zhou , Tejun Heo , Gao Xiang , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo References: <20260223032641.1859381-1-ziy@nvidia.com> <5105764a-8313-45bd-8b91-8c0ea8cdf077@kernel.org> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <5105764a-8313-45bd-8b91-8c0ea8cdf077@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR2P281CA0010.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:a::20) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|PH0PR12MB7096:EE_ X-MS-Office365-Filtering-Correlation-Id: 3364a66c-0ac8-4d55-5507-08de72ef5c87 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?UG9uNWhBRUZOUXJvUHNQNjhhTjFDenRMeGpUdlNnR1BUY1U3SnJrbFRoWmxM?= =?utf-8?B?RTNMZ3dRb0RjVXJIYVA5RWtxQ0lGZlhjWW1pMDZIOWRxaSsyVDBrcUZIOWZa?= =?utf-8?B?MlFjZ2MvRDI1M3pTc0ZrYVlDdnhvRDhrbUZrOTBVU1hWcXZwOFMzV1EzWXpj?= =?utf-8?B?TzZqeFhaR3F5T0p2eXNUT0Exa0h6N2xCQ1Vub29zcCtkakVxRmkzcWJUK2lu?= =?utf-8?B?VnJjM0FSL3lLS1dROGtwZU9EaitWUmZzQmduL09ZNWJYY3JIdVhOdUFrU2dG?= =?utf-8?B?N2VtMXZ4MWJtWGxRWnN3VWhEWWc5eU1ObVpiNEF2ZnVKendib25WdmNKZkNX?= =?utf-8?B?eXpCN3diUVc5LzBYYVUrYlM3THJUcS8wZUJUZG00QktJdldHdGR3eFJhZE9h?= =?utf-8?B?c0JlWWFwWG5qRWpramppZXV0TTJtZ1o5VHRBdlVGYkZJNWlRQ0pMaVdhQmVY?= =?utf-8?B?dk9ZUXAwYlZHa2FWREpuM3FFUUxFODBCSFBvZ2lsbTdLbGtJY0c2dFFBNEFr?= =?utf-8?B?WTE2RXNkWWVZWlBZN01leEtTUVl4aFVxQTZuS0FsWUVQbHZFVDVqakI0cHdm?= =?utf-8?B?eGtQU1hVZjRYS0dlSVdaNDFSV2ROSUpCa1pzSmdXeGxYUGdjK1RYczd1UDFi?= =?utf-8?B?NU0vL0w3MEcvaTR1d2FmK0tsUWVWUmJzdkhheWVDVHpLVXlWdCtDVFBPT2sz?= =?utf-8?B?Z3ZuMnV1VjVKcFdpdkVrMy9rSWVBYUpTTk8yeDFQNVB2MXRqL2Z5Zm5EWDJ5?= =?utf-8?B?cStOZmdOTXRYWmZpSS9FOEJYTW1CN3NZL1Zwc0FGOXU2OWd4eXJOQXQ2QWJX?= =?utf-8?B?MW14UjNydlVPWVhubkZzanYyTk5TUk9ZWW9yM0MycGVwbVd0STd4M2xxUVJk?= =?utf-8?B?eC9VVkQ0UlBKVmFqSnpLZFdlNlRhZm8vM3phL3JXa2Z6NzgvZnk3VVNrY3pv?= =?utf-8?B?RzRqQ25BUmVEbjVsSG5TWm9sVU9rc2syTXo0TnBIN211TUpjWngwT09vNzRy?= =?utf-8?B?cWxMVEQ5YTdoL2dQVy9iZUpZQ2dJK0gxSWxIMFJPbDJuUGVkbTBOWFJXSU1y?= =?utf-8?B?UzhZTDMvWUpVK004TGJLNU16bzVWaXpoZTh5R1JqRG9tbEtGTCsyMmZreG43?= =?utf-8?B?NzBUNXJqOEU5TTFTWEFNOTVrZks2S3MvUG0rU0Q2amo0anhhdWFqTTBPbitw?= =?utf-8?B?dHFkMzJPbkJxRllHd3RhZGJub1dtbEpYdGM4Y2FWYWtDdm1hUDY2QUtOdGNa?= =?utf-8?B?ZDl5M0g5aFkwRUJ4dStVTWNkdnk4UTlrb3ZzdE9WQVoxSldzdGtvS3JkSHFj?= =?utf-8?B?ZmpRZHhLQm9TQ0FTdnFPZWN6YkpvdTB2Rk1lTjJYQmZta2hUMDVIM3Fma0dt?= =?utf-8?B?WGlUNGxUWGVXUUJpaUJpK0ZEK1hCVld1NG9ta3F5RFI1OW0zOXZQQnlDZlIv?= =?utf-8?B?V1NLRkZDZHM5clY4bjNPRkdBWWwvTTVuRG1WcklTVFdGZ2RrQlY5c2JjWDJC?= =?utf-8?B?QWo1clRzWi8wUW9yVTBrOEhCZHljaEdqKytkUzNhRnZTM2hWZitlQ3Y2eHly?= =?utf-8?B?QWdVRWZCSUt6d2tSYjQyVDFicGFDaXpuQXBpajVPNVQ0NDFaTFp1NzlhM3NM?= =?utf-8?B?ZkZBM0VrWi9vcEdVME1ZMkhjdy9zOFYybkJJNFIzVmVBUEx5MWh2TUFIZmZ1?= =?utf-8?B?ZytoZ2RjUnBJdjYydXo0YnFPRUNUZjRXT244aDlpTThRSUhsQkoyaS95WG43?= =?utf-8?B?dkpnako2L3NhRjRTRzNPemtkb1lwSFlGTGpMWHJnNTJUOTFFZTR4alNUQnJR?= =?utf-8?B?bnN3d0dINU5EUzNVRlpnKzl3VmtCZHREdGYzbHljQzZRWlI2UTdHMVdHeUQy?= =?utf-8?B?MFNPQmwyQVR1aGdSdXFVNjdJRlFTczBsUFJYc0t3dFhpTWJEMnVRSjJXWHVi?= =?utf-8?B?aWVCaEVDdkFrN0x0VnRmUWxPcXV6eG1XRGhVeEQ4VzZpb2R5SFhmaHR5Z1F0?= =?utf-8?B?YkMwV1VRbFBQSkxvTGZscWlXMzhvYUhvcjhaaW5tSFpUS3JnUDg3L2tiWmdH?= =?utf-8?B?cFlKRFpsOTY5amNWUE81U1QyVDM0RXZwNTA4bWRtd2VjSGJuQVo3SGI0ekk2?= =?utf-8?Q?ghgQ=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PH7PR12MB5685.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(376014)(7416014)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?OEtrTmdLSHRMditnMmtZVWsvQmY4ZlZ5VU1BeVdQa2RvS0tGY0R5aVY1Rysx?= =?utf-8?B?TmlXS1g0SzRXMktqMVdZQzRoTTNaY21lOHhFL3lrZ0thUkJ3Rm5wemNZUmpG?= =?utf-8?B?WVprT3pZajBxTkNMcy95Ynh5ck1rQ0FwZWpuRksrelpQYjVxWFZkUWtQSWV2?= =?utf-8?B?bTVJSXRIU0U5WkZ5Szd5NnEzNDIvbnBnMHhnTzZGVlE3TkZFRWtXb3JBeVA2?= =?utf-8?B?TG1FK016Y2dxaVN3cURWOTNURExHbERyTDBTbHBNL0l2Ny9DUkNiR3ZPeVRP?= =?utf-8?B?RjRySTR0QjRjb28yYWpJeHJzd2M0NE44OHlaTE1MVHQrdnpSZkxSdFBKUDZW?= =?utf-8?B?RXhUU0lwZEl2S2lCVDdhYUI0TVl2ZFV4Zm96d3VTK09kSnl3MDEwZ2dYSVJn?= =?utf-8?B?VnRwWkpsdjNwd1BzTmxmUmtPZDFzTFNZYk9UNG92TU9QT2ZuamdNRTl1eWtN?= =?utf-8?B?RjNBL1lnc2cxVHNCbkNXUnJKcEU4QWtpQkNXeDNVenV4Ly9paTNoMXl2emFK?= =?utf-8?B?N0N3ZHB1RzRjblFZajJKN2pTTTBDQzJXZ3JENm1teGs0QmlvOUdabXZrOXpQ?= =?utf-8?B?ZGowcmhDVUJxVDV3a2VNRXZnL3hvOVUvMWh5MWVtcHp0WVF2WmhmNmtYK0ps?= =?utf-8?B?dU1GZExEajVBQ2hVbHNsWnUvc3pTNnNVeG5RNExVK1VoUmhTUjdGM0ZWWHN2?= =?utf-8?B?b0hQL2lhc1ZkMmtyOTYrU05qRkd1S3pQUzdWTDhvWGxWMzdIb3VOVC9tWnZ3?= =?utf-8?B?SEpvb2ZRTmJRbTNlMmZiOTlmdTMzZDZ1MGg4U3JVTTQyVUZ1VGZMakRKMmp2?= =?utf-8?B?eTlkSjUzZzVVOVBHOWp1WmgyRDVxTkRBK2RPMEdYdkNGdkZwU0pGdUNHMUlO?= =?utf-8?B?MnNVRVhTRThPMERLcnY5VVdEM2V0NFVnRkducmFRWG1qZ0FHTVZFRXdhbmpB?= =?utf-8?B?cXpnSDI5QWdaUFlzWmQxOWc3NlR3VHAwTFpZc1JmQ2h2NjRCZWEwL3N2cnBK?= =?utf-8?B?WDF6SFJQcWtzYlBaZm5sdHlmNnN0SlJSSHF0cTRzdk9hSEk2ZjRIZnU2UHZ4?= =?utf-8?B?Wm9ycDF2UU1qcnJsMGVFaU1nclh4QW5pSm51ek92L3QvbWc2S3lhcGUyZ1Fs?= =?utf-8?B?dnM2cGZaVUp6ZHd0eUNuWGlmRTRQdFZRdlBKZlE0TlJobGFGYWJHRER3ZHBG?= =?utf-8?B?SXdFTVY4M21IQ3ZOQ1YxdTg4Q3lReWJVanVZdmx1U0RxbXdWbkt4Qjh4NkNX?= =?utf-8?B?QnhhK0dsQjRpb3p5amJ6R1MzclRiY200VFAyZ1FDYnNwSHlVZnQxbVE4MHdZ?= =?utf-8?B?Q2pnRGh1azc2RUF2TElLNmdzNnpHNU9LWEpqSkFLMG1XRGlQMU0zbldIK3V3?= =?utf-8?B?MGlKWXVUOW9LTHMyMlhYeXJleDBQSVAzSElFT0dON2g4VUpFVHlMeENodDY2?= =?utf-8?B?K3JZL3RJOHRDSlBrVENxY1hNck1JRVRWWkFJQ0ViTGkwTFJrM3dpTFhXTVlB?= =?utf-8?B?R0RPK0Z3SUpCd2ZlVitIZGxzSy9xUHd1bDR3RXNmMUhwSG9EeWl3OXZmeEpP?= =?utf-8?B?Yk5hOHd6S2RqeElNajNIUDY2bUl3VExzUFBYU1hPWGNYcUtuQUVyZlZuSjJK?= =?utf-8?B?bzNsRHhuc0dTR0ZORWltcEF3VE1EQnJubVU1VFFiRGkxWDM0MmQwZFZXQTQy?= =?utf-8?B?Z0FjemVSRUJhRkhMRFVWYitFY1pyc0UrbSt2ZXREN0xvV3d6RVBwbzg0dDcx?= =?utf-8?B?Y0xQYmx6VGh1aWxqTTQ1RXpPYTcvU3ZYRXRENzJMVkZYZUtrVmttcVNqNjZk?= =?utf-8?B?YmZidFk0amp5enRqYUFRM2JlbVVSckF5ZmZWeFpPVk5Pc1ZmdjFTUUtaMEVP?= =?utf-8?B?UHg0NlFzL2lncHJMN1BVSnpBNXBDSXBGb0tGdDluOFZHWXpnTEZOVFhOclVx?= =?utf-8?B?d2F4Uk9xNzZpbE9ING00VW5vRnJqa3Z6d21MTWlOUzdJZVM2Q2V5eDUwSk1T?= =?utf-8?B?cHBENitMNEhrTE1xUjk5QStsSHc2L1BZSDl4ZzFrVHFTVENZQnJBS0pFY1k1?= =?utf-8?B?OEVqbFpDMzFZbGNQVk1CQnd1OEtGcFZYeERjUWNEbHFWTm9aRUYrUEF4MzBq?= =?utf-8?B?bnUzdTBwT2QzWlNpSnpjMmFTSWhoZ2toRzYrZ3haMW1KUTJ6QXJMeDI0b1pv?= =?utf-8?B?SU52clpaVXNsYnZkeDFIaTNma3ZPdTF3ajhIWGQ3TjVWNGd3dUFHYSsxbDV6?= =?utf-8?B?WDZMeVQwNzdqM2x0VXZqeG5SNEdPRWxNRGxIM04xMUNCd1JzZlIxbFV3eUp6?= =?utf-8?Q?oNt/DRR6nbShYklv1Q?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3364a66c-0ac8-4d55-5507-08de72ef5c87 X-MS-Exchange-CrossTenant-AuthSource: PH7PR12MB5685.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Feb 2026 15:22:31.2876 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: ObwsaqhfVgEujivvym37aVRlFcjn2SUWXLOtHZw8Y5i7PdnDsTHnhcYGobYklASG X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB7096 On 2/23/26 15:14, David Hildenbrand (Arm) wrote: > On 2/23/26 15:06, Christian König wrote: >> On 2/23/26 14:46, Christoph Hellwig wrote: >>> On Sun, Feb 22, 2026 at 10:26:30PM -0500, Zi Yan wrote: >>>> Hi all, >>>> >>>> Based on a recent discussion with David Hildenbrand on page->private >>>> is not zero when a page is freed[1], this patchset is trying to fix all >>>> users do not zero ->private when freeing a page and add checks to make >>>> sure all freed pages have ->private set to zero. For compound pages, >>>> both head page and tail pages need to have ->private set to zero. >>> >>> Requiring the user to clear a field before freeing is just a way to >>> awkward interface.  Don't do that. >> >> Completely agree. This is just asking for trouble. >> >> The cache line(s) backing this struct page are most likely accessed anyway on free/alloc. So I don't see much extra overhead. > > I think the question is more around handling non-head pages when freeing larger orders. But maybe the overhead of zeroing page->private it there as well in __free_pages_prepare() is tolerable. Good point, sounds like that is a bit more than I thought it would be. > I'll note, though, that we already require page->mapping and page->memcg_data of pages to be zeroed by the caller, so it's not completely crazy. (see page_expected_state) Well that's not defensive at all, basically everybody which forgets to do that can cause hard to debug trouble. Maybe that practice should be reconsidered. Regards, Christian.