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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F042AC43458 for ; Tue, 7 Jul 2026 02:17:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AC1396B009F; Mon, 6 Jul 2026 22:17:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A70AF6B00A0; Mon, 6 Jul 2026 22:17:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 939216B00A1; Mon, 6 Jul 2026 22:17:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 620386B009F for ; Mon, 6 Jul 2026 22:17:07 -0400 (EDT) Received: from smtpin17.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id DFB271A02B4 for ; Tue, 7 Jul 2026 02:17:06 +0000 (UTC) X-FDA: 84960368052.17.47A7D8F Received: from PH0PR06CU001.outbound.protection.outlook.com (mail-westus3azon11011016.outbound.protection.outlook.com [40.107.208.16]) by imf05.hostedemail.com (Postfix) with ESMTP id 47767100004 for ; Tue, 7 Jul 2026 02:17:04 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=RTBQ+bi+; dmarc=pass (policy=reject) header.from=nvidia.com; spf=pass (imf05.hostedemail.com: domain of apopple@nvidia.com designates 40.107.208.16 as permitted sender) smtp.mailfrom=apopple@nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1783390624; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ez3fE9/tS6Itlks/AFDPNZBYXHc7sG383zFBhvlKEu4=; b=tnvrqyCSy1Ga/GZStnJBJkYbm9Z0OHwLNwD03+/X+4SBpq6eRbuo+ppND3exp8x6htdXMC dmbJKBgpEPwc+H1BCJBeL81gqMmmyh4LY9CI1BY8v3M6rXCOE8LH7SqTKAFhaN/gSz62mC cBzLyZrLQOqQtvoM63MvsJeL3VayJx0= ARC-Authentication-Results: i=2; imf05.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=RTBQ+bi+; dmarc=pass (policy=reject) header.from=nvidia.com; spf=pass (imf05.hostedemail.com: domain of apopple@nvidia.com designates 40.107.208.16 as permitted sender) smtp.mailfrom=apopple@nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Seal: i=2; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=pass; t=1783390624; b=ZqFqkbEbrHf28qoUOzKdjS/r37ktI0dhj6vKJrtNIG5fVmFBEJDX2ZdcqrkrwqzzZU4Paf N1yxEHimd1Ve/dKV9gjgo/DR9gSuTK4RwnY+b0uiEN6FmB59AjsdCHJWRhiZvJSEBrRPrV YG/QIzoaDXLOQQAzGTb4RnHqRmiH1r4= ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=KbVE/NoICa3ggM3gBx4BuIb4dQgr4u9MjlqRdReyI6CqMrivyQgxQPa44QORKVqG0N9x2aSb0mfyMqH7P6sxlHwnH63H98kCZNPtk6LY7XF/Xfy4s74N1VMsyYYqLvcC+B54FN75jfzTt+NuH+C+8ebWiy2euOl6nnSeBlk363/eGB6hndZWstxB5g51/P6eVx6DE+H66X60+m+KcwkBJOpzSs9HrMt62PkZ2s9b9syCrGGkgEpR661Gv70dcpoNlkUYZmyAT2R1ylehDngFBBvoKnKOvqxnq5AsbxeSOM2dVSz4MhXH1EH2PO0ABfda/trJPoeOAhFJRO1EoYGIZg== 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=ez3fE9/tS6Itlks/AFDPNZBYXHc7sG383zFBhvlKEu4=; b=Uc+mYbj35Uhj4tUpUBHy/niy3Mozu2FP9OkWLTymxCNOTgwqe3fOtn/xi6QKwAh+qxXlprT0EjiEuUtOwK0wY5/VAmDZH93TN1iQ/IipGIvBSPJBUBeMb9dD7UymEsBPauZ8yX345NM0sAZ0aGLaE34SdD1CbMGOg2mQDYziRvqFEo88VFSKpt0K4W0gXzvM+s/SWcihzwgCGkrzDLZbeZdoP4I+2+uvZ7R9XJ5Coj2DEqO8zFWKTr4mTzLTDwAcDeUG1bB2HV95KMGjGDIkuRvtnI96JppM8MHisjNBCPabAhnsnnwaGA6gP8Lj0RHICWsi5ATcNozy2kE5IUZ0/Q== 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=ez3fE9/tS6Itlks/AFDPNZBYXHc7sG383zFBhvlKEu4=; b=RTBQ+bi+/ruUd8CSs9pOxguGAN+8k39lvO3A58qXENIGw121tDPUWgCYBuMA9Y6992OZGQDUX49sBfT3tkR02JXQggyzBrSQSPSrKaYc5nF4C0VhImQevREwlmgYUn8Oc4MYyqa0BcclvdEkSBUXbbjQFpRlMCLgzVdiosHoyfo7yA8ykleVuwL/Ak0L6/Z/1xUY+F46X/pijr+VQC1yG1cvrRX8aV8XLWgycTJELjavPS65BwICXYIGeE+SHxEy3Wch/SffdxAgSUJ9Lt+CHPcrQQr4wY5jbbKABKY/LoBCNNe+Wtf8R/bEAUkkU3M3LoRZuzIwqawjzWatq4LA9A== Received: from DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) by PH7PR12MB6444.namprd12.prod.outlook.com (2603:10b6:510:1f8::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.181.10; Tue, 7 Jul 2026 02:17:00 +0000 Received: from DS0PR12MB7726.namprd12.prod.outlook.com ([fe80::5807:8e24:69b0:f6c0]) by DS0PR12MB7726.namprd12.prod.outlook.com ([fe80::5807:8e24:69b0:f6c0%4]) with mapi id 15.21.0181.008; Tue, 7 Jul 2026 02:17:00 +0000 Date: Tue, 7 Jul 2026 12:16:53 +1000 From: Alistair Popple To: Li Zhe Cc: akpm@linux-foundation.org, arnd@arndb.de, bp@alien8.de, dave.hansen@linux.intel.com, david@kernel.org, kees@kernel.org, mingo@redhat.com, rppt@kernel.org, tglx@kernel.org, linux-arch@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [PATCH v4 1/8] mm: fix stale ZONE_DEVICE refcount comment Message-ID: References: <20260603080152.64728-1-lizhe.67@bytedance.com> <20260603080152.64728-2-lizhe.67@bytedance.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260603080152.64728-2-lizhe.67@bytedance.com> X-ClientProxiedBy: SY5P300CA0088.AUSP300.PROD.OUTLOOK.COM (2603:10c6:10:248::17) To DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB7726:EE_|PH7PR12MB6444:EE_ X-MS-Office365-Filtering-Correlation-Id: cfb93e9f-24f1-4e6e-7d79-08dedbcdd3bf X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|1800799024|366016|376014|7416014|22082099003|18002099003|11063799006|56012099006|4143699003; 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:DS0PR12MB7726.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(23010399003)(1800799024)(366016)(376014)(7416014)(22082099003)(18002099003)(11063799006)(56012099006)(4143699003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?U6XkhKMN+XbjUJv16e/PIOwLqC7ENCZ3dPAhmyzPk2fNoJqrelZCryy3QnwJ?= =?us-ascii?Q?kwotsdFBafodMemdpw99MiUya8+ksS3w3bIdO4ca6jQYiqh1+RzJF6QTHJOm?= =?us-ascii?Q?DHxA2Sqyfc8OuF83icbnDNIuZ2K4XsP+xoODJjedfSL0GE/wF5rOtshZUVCp?= =?us-ascii?Q?Hlo8mMO5IBGc0ShYtqhj2+Ma5hsx4vSqHYmSxIkXgE8C+4AtyBUSSyrUbybM?= =?us-ascii?Q?9pf+1N6cxCjHueXWwLq316pjqtt89CqaX/iEM/4jLCgLvGPCIT7eQz0wAX5e?= =?us-ascii?Q?w95WTOfvFAY1HW1NSLOssyF+fqiDpm3C/NL73JjjWpwE2waZCWq2sZlZD82O?= =?us-ascii?Q?qOd6XcKwFGO+N12K5l1rWQXq6MZizNLD03rAeicfUReNk4lAAnmtfUlvNw/E?= =?us-ascii?Q?sGTWb4CKf7ggA0yw+jWOSxNXMSKiafpDw6kOJTM10PM30aPNShTElahkp6Dx?= =?us-ascii?Q?IOMXD7GN0ljV7S6drZWFlOM/UzB7jFCiWCi4GAi02vwDo3TK6j9YPgMOKX+t?= =?us-ascii?Q?V68tR4+wYMU9DzjC8ZWaT28iAeQZ+RpJat3G/D7buhjB54o74TDWKV7alroJ?= =?us-ascii?Q?tzT/i455uVwSN+j9I3sCPTsb9oFGipbrqc0Ymr7Bixh0K6Lmc4fhF/wKywdk?= =?us-ascii?Q?0mHHTrO0SxizBlWhXPyLgoQLxys8jizMAKFE7Hk9Z0mkrhzX3+AN8npbFU6q?= =?us-ascii?Q?EphLQ9LsDfDXsske1D8kSdLE0bh7RPHKPDiXvwncv+eKPoDkI1Cj8/XdO1N6?= =?us-ascii?Q?zQdOH/rPerUF6F7CA2kbZZfEY89B3WPzMXG6695WM7Q3PjcGZhu+3gRXVpSF?= =?us-ascii?Q?LO4InErnrnx1ddXvGPvY3k4NrAFW5CEmXGCZ5jokL4hLVuMclOK8KCHKXRzz?= =?us-ascii?Q?wGi9hpxr680lPaZeGMBe1WbDVB9HMQtHbW8geMrPnY/XER8HnzvWIYUGvjZQ?= =?us-ascii?Q?cw17e/OTyLtrttlc+GLB34IK63m67smw+QJ4JJw0qFkwLD1e1I8OGYO2idS3?= =?us-ascii?Q?OQU3yk8fWCnP16VEU9wCjJUVlqDnlAC7rOrZEtxQIYPlmFADZeuwHb/IQvZM?= =?us-ascii?Q?82YELYUGfLfWPg3q7/8KtnzORDRtcF0aipzHbbek0qy+CNTRB3G++xj9J8gI?= =?us-ascii?Q?fPyzOSNnF67gLdDnEcGlD01AibubKPUyo47avHaItsPiib1D0XHiRHj/xXc7?= =?us-ascii?Q?/OoP7yF4gjlJ3FWg8PJ4RxR2bOrZ9zvNN2hetAekgHgkGH3l8Rp1up9/M1qw?= =?us-ascii?Q?32qji39TBieYtrF0noJZlSc2+H7oFzz8tLomdrW+cVrYeIbuuxQINRd2SHyY?= =?us-ascii?Q?XeT7redQh9KKPty5nAn5qH4FJXgzbFgMr68kiKDkxJ1/PJx5gu++UOiiCp8Q?= =?us-ascii?Q?PUyn3zIiKkyueefzRvb/v+TLOMX8mSBT37RAxTKFiFMEC5YACQamiJ9MjTK8?= =?us-ascii?Q?6svbgWIgsb++i8vkgbbPc8M+navkLV41ei/eYetiJ1kFlAd1aSCWcpsrLKgx?= =?us-ascii?Q?iUdGKOpXkZy5Mcr3HfzMnAMmUCBN5O4+DTcvjNUt/5z4mdidNTcvmhCppnme?= =?us-ascii?Q?qH3zLpfaHVisRm3uAj4h+KDlvcY9S+Tw2GVqoR6QZFEwCYBXEHU7y3yBaEbG?= =?us-ascii?Q?07aRzR6G2nWxgvPbH0GnrIhvC8J0UHDpMpQofzC4M5QDpxNBIwdvU20Cbz+m?= =?us-ascii?Q?C5C+NR5rebZUYWWeYt347YbvDDzBlIyNYlNOw/4ZK78nF42lZwCBUP7p7qql?= =?us-ascii?Q?UYfry/mM8Q=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: cfb93e9f-24f1-4e6e-7d79-08dedbcdd3bf X-MS-Exchange-CrossTenant-AuthSource: DS0PR12MB7726.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jul 2026 02:17:00.2245 (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: 5Kp6J0pe396ATkUWyk29KiCzeyjWc48RfuRg91Xqwx6UIhqqhD1N4oU4/2lxCMpXqGKP6EucToXZ0zBW3558zg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6444 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 47767100004 X-Stat-Signature: gi3ddbnk1y9qys5ey7zif4n71nbhyemn X-HE-Tag: 1783390624-799394 X-HE-Meta: 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 7Qfa8RD7 yz/nJuH5GU2Paf4vGsAj+tMckVXWzOnodyus+plWRSdMGIbWmvOrJwmv9V4W1Rx4fVVkYlsTT0S+72k6nNcKfL83qKA3wIIkD/PnBCI3CGih1A+0mKkQ9AXsQeI9m481p65C8WPt6h022MJzTdl7tu1ArFuiQCUGWLVWLdCgtTJs7e98KH7facz7uwl+6gnv3pxNUdX8j8Fu6bNfUfEW7kwK4TW10znNi0NTyto5G5Hifzg8YDHKMpgHsT4ysuEoFuwZM3n6VYAbFz8sDCE+ZPnQZotTuaM+sNfHEPq+OY4QfVwMhF6ydDLSdgFbGmwmkckS3sytHh7pdLQ9GjYymnq2zlOgUDaTKsuRHci/lw/2dMa3GtfUNjXrqpnnhge0BZCm9XEZgX9Da6yWybX4LF0r+BVi8n69gInIM4o0Sto5VhPQ8C3PeamAMIJzGQC6avRsGe+uyjP1x5IjE3y81MJjgBQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-06-03 at 18:01 +1000, Li Zhe wrote... > The comment in __init_zone_device_page() still uses the old > MEMORY_TYPE_* names and implies that FS_DAX pages regain a > refcount of 1 in the free path. That no longer matches the code. Correct, obviously I missed this comment when updating the code. > Update the comment to describe the current policy correctly: > MEMORY_DEVICE_GENERIC pages regain a refcount of 1 in the free path, > while the remaining ZONE_DEVICE types start from 0 here and raise the > count again when the allocator or driver hands the page out. It would be nice to make MEMORY_DEVICE_GENERIC the same one day too. But this change looks accurate to me: Reviewed-by: Alistair Popple > No functional change intended. > > Signed-off-by: Li Zhe > --- > mm/mm_init.c | 10 +++------- > 1 file changed, 3 insertions(+), 7 deletions(-) > > diff --git a/mm/mm_init.c b/mm/mm_init.c > index f9f8e1af921c..35de3b6a186d 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -1027,13 +1027,9 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn, > } > > /* > - * ZONE_DEVICE pages other than MEMORY_TYPE_GENERIC are released > - * directly to the driver page allocator which will set the page count > - * to 1 when allocating the page. > - * > - * MEMORY_TYPE_GENERIC and MEMORY_TYPE_FS_DAX pages automatically have > - * their refcount reset to one whenever they are freed (ie. after > - * their refcount drops to 0). > + * MEMORY_DEVICE_GENERIC pages regain a refcount of 1 in the free > + * path. The remaining ZONE_DEVICE types start from 0 here and raise > + * the count again when the allocator or driver hands the page out. > */ > switch (pgmap->type) { > case MEMORY_DEVICE_FS_DAX: > -- > 2.20.1