From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CH5PR02CU005.outbound.protection.outlook.com (mail-northcentralusazon11012052.outbound.protection.outlook.com [40.107.200.52]) (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 1412414F70 for ; Wed, 4 Feb 2026 17:34:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.200.52 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770226483; cv=fail; b=hCXkT+RPrdGYHeU/4ZbRIRrOanwj9BIu2qodHgL2BCXPLt8uHKaYAh6rHOOYP4IiuNXGoR7dJRRlb89fru3n349cbIWDG0sC1tdv5avBK1LXoRYP53SXFfzkgbumvn+x2LPGmYD9qrxbk64Mf+ygioYxG8rITwgnfrIS5K6+xTM= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770226483; c=relaxed/simple; bh=8WdDCOH3ZM4e3S+7RHEiQuTbM0WeXx3fvtDdWwVZ5kw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=tdx5DAkh/iSj9g9U+gyrLFWm4gR7IzrTv0DjstmdM16Lo65sdEglwUzv2a5NnrRCmKpvq5WgzjJk4DvtwwjcvyVIrizZoZzGTmD8mTpWEp8gcVRX4bK6H0/smnB5nn1F8AQ9zT/Xz8IYSXuc/Y9BlEx6UDGZfCl6JkQ8Hg7WWJ4= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=iNdR39yv; arc=fail smtp.client-ip=40.107.200.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="iNdR39yv" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=inWYelevfFMmkzGiHqYKyuwT27rwaFqJGyDoU1zl/WQoIuGoXtnLKDcuwUN9RYmRKHzIUQR6uXjYVf0O+E/aiU316mxVM3AmbTqJljlanq16MMMNTCjWtA5L188sRuJmsF7UScJaEhm0SRP8Uxqm9hCyPz0L1n42kZrra4DsUdbkJhRUrGZtUaglNs6FUkjKBbtU4g8uKpgstTu679aMmbtDGN9KNuHCgE+eUTkOIZ+8M2HmpFC/nOBscI4WnJDOVvfo3XyqDNB+4T/JWNjfOXVbDfQB7HPpejKQc/ocFGoBILYwDTS9nnj6CydJVYwU56o4nv5oBkUhgMyY6qNxow== 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=8WdDCOH3ZM4e3S+7RHEiQuTbM0WeXx3fvtDdWwVZ5kw=; b=IcviB4LEsKnCgZMWN2KssdRgKY1S6/Sg5OW/S8DC1hf0c5d6qmbrakeDupfBcFsAslZxgtorMh/S4daBuWjV6o3cy6vP5pNOWLu3m2SeYNUIHKb+RVIlcJeXMOLszrs+8CQ3C5awM03KMjvV6DAM3ytQOaaK5rAGT5o6kwon4Yz/ETnPbA9znbe8i9n5Gqyd7y6fSpQmIEanh+5RrrnKT1wEZKVky/fUgE7eJoSgxt5ATZXBCFu6jasQpdk6F9Or4Jn3kID6luS9hLVIavt2BeUJBE8kamFmeQfveuKxhlOCAD6iJODtB3zyVcStODCOFK+brkV7B38kQNt6L/YZjA== 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=8WdDCOH3ZM4e3S+7RHEiQuTbM0WeXx3fvtDdWwVZ5kw=; b=iNdR39yvzsaHK04ncmhVRbxH4049XmmbOXUN+Mw9ReEm0Bxgqhp3Od2rqkuIdplqKnm1NVkk/oB3QR5ZbQhGt1oUjqzexqJyKDikno4kaJM5eMpScmTJRX7v0Ay5ru22mpqnkQRkozdB8uNVHdmuA/7Co60LqNSR7kyE7hwvdb6nQ383rLfI5nPcx7YVggJaa5fkniSjUMbAKgKO210FYuId1SvRavzGuTzvsTK1S08USu1dXan7ojUGLdpqa7ptvlCIt3rBqKjJaHCE8fAMIdajhB0i5t1M9b8DU9gxtECv+eBmZp+1FeFsf29JAY5AX5N8Zb9AoUW0OLk2c6iHQA== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) by SA1PR12MB9002.namprd12.prod.outlook.com (2603:10b6:806:38b::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9587.12; Wed, 4 Feb 2026 17:34:37 +0000 Received: from DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::f01d:73d2:2dda:c7b2]) by DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::f01d:73d2:2dda:c7b2%4]) with mapi id 15.20.9587.013; Wed, 4 Feb 2026 17:34:37 +0000 From: Zi Yan To: "David Hildenbrand (arm)" Cc: =?utf-8?b?5piv5Y+C5beu?= , , , , , Matthew Wilcox Subject: Re: WARNING in memory_failure() at include/linux/huge_mm.h:635 triggered Date: Wed, 04 Feb 2026 12:34:35 -0500 X-Mailer: MailMate (2.0r6290) Message-ID: <25CA4D90-A24E-49C6-92D2-08080EC81466@nvidia.com> In-Reply-To: <48978612-6933-4897-85DD-6740B6C8570B@nvidia.com> References: <1db245a8-f9ab-42e4-8cc6-cc7562961921@kernel.org> <48978612-6933-4897-85DD-6740B6C8570B@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: MN2PR03CA0008.namprd03.prod.outlook.com (2603:10b6:208:23a::13) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) 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: DS7PR12MB9473:EE_|SA1PR12MB9002:EE_ X-MS-Office365-Filtering-Correlation-Id: 8e4b5080-e77b-415e-83d9-08de6413ab3e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?ZFlXL0N2TWpBeHVwTEo4cW9ScWF5NER4ckRMZ2RKaWtad215RU9LTDI3aGcr?= =?utf-8?B?YWg0MDU4N1NmT29ZUUFCLzZoRjVxbnFhd2pRZGRBRTF5M1hsbTJldXE2TExT?= =?utf-8?B?enhQaC9kKzNCbnZVdVkwOFRzZUlvWWowQXYwSkhOS2IzTUd6UlFyS1EycFdG?= =?utf-8?B?QUJONi9OQ2IrRWIzMTVVTWdYWFdCRDRIVkJOMC9rays1allhaVZ5Y3g5WTA3?= =?utf-8?B?MXdMbmRVUHZJcEZIdkJXSkdzaUhjMDBhRm14SEQzMGY5LzcxR1pKY3B1OVlE?= =?utf-8?B?aER0VGpQS3ZwQXdJOEpoNmJQYUpqSWNwOGd4Q0tnbVg5VUVRWVlhSXkzTXJN?= =?utf-8?B?YXFxVVJjeW5FNjdKR0lVY1gyWjM4V2VIWnpOcWxBRUY3R0J3Z2lJU0hJREJa?= =?utf-8?B?aHVaWTVNanhOUFZXaHlNa2JKU25VaEoyTUxiTjlZUlZsVnlwT1drbkhpWXdx?= =?utf-8?B?ckFIMUlTTXlLcDQ3Z29jL2YyTkw3dCtQU1VZSUVEWHZkc21VU3VTYUJTaFdG?= =?utf-8?B?RVBUY1RIN0prK2NzaE1JUnJ5VXhYQTIrSHBGNGNQM0lScHB3VVRQQlZlUTRY?= =?utf-8?B?NHQ4Yy8zTjcwTVkvOTgyTkN2Z2M2cERMUG5WYUdWdUFubjlJZ21YVlFKOFVv?= =?utf-8?B?QXdJWHp3dDR6SnhBL2dSL0plb3pzMjV2dS9pY2Q1TDc2cXVvZEtoaDN4WGwv?= =?utf-8?B?SlNUNzNBSUcydzNaY2wxM1pEclllYmxiVGtscXpVRDV2TFRGdFRmam1JSlBP?= =?utf-8?B?M24zb1ZPZ2pCa0FaOXgzWUU1eHBPbU9icTVESzFCY1Y2R0pNZWt0cGpvdncz?= =?utf-8?B?OW5SWVM2WjhLRnJ2bG9BWEh0OUxodzdwZkh3TGZBK20vUFQ1eW1ENmwzUm5V?= =?utf-8?B?bS9kMzdjWWt5T3Q1b0tJTmQ3ZXp4UDFHVnNKbENuYmZFbTB1eHBPcUFKRmh6?= =?utf-8?B?YlRzb0tOM0kxNzFwRGlvQmgvSUhjNzhJR25jWngxVjBkamFxSVpWQWJWamd5?= =?utf-8?B?SmNtQXRZN1E1aEwrSUcyVVp4UnZPbUd5VlltWVpFc0dIMWdjNEsyQzhYWXpl?= =?utf-8?B?amo5aEp4S00xMUkzY0ZhRTVqOEVoaWpZN2UzOTQzM1JJbktwSEFxNTVvem4r?= =?utf-8?B?KzJVL0IwM21jTlEydFR2Tms2ZUhSQ0NhWU1TU0Z2K0JqamcwUytTU0x4L2VM?= =?utf-8?B?UlU4eFhZTFUxd1JhNnVMWUZJTHVCV3hBdjVPVi9FVTk5Ykczc01iUy80RVRN?= =?utf-8?B?dDVzSzJZZEd1QWJVdVJwLzgzQkNpSWd4Z0lGQ1lYZDd0YW9wODZDbng3QlIv?= =?utf-8?B?eG85dHlzd2w0K3NTRnprazh2OG9jaC81VVVkNUFFNVR1T2l3OVUyYUJCZE1E?= =?utf-8?B?MytvVk5WL3lPR0lnMEdvcmI4Qk9FTXJMeThobTI3aWR2UDMzcm1NeUduNUh0?= =?utf-8?B?ZkZha0hCd2RCQnpTNEtIMHd3RHpnak5NRXpNeHdqQTRMSWltUWhSSDZMNTRP?= =?utf-8?B?b0ZrM3ovNE9TMXVHMFowa3RWb3ZZOUlDRmYwSFFDMFk0a0pKbDBZOVVLK09w?= =?utf-8?B?SnNMNk0rSFhpZ2hKdkwwcEFCUXNzdVpZSE51Ky8rYVhYTFFobWp3K0swRGxo?= =?utf-8?B?UkRvTEhRSHA5TU9wR1VnNzlHS0ZGYWxVUjRmNWJBSG5WSmp3TUZMQnBzZjlz?= =?utf-8?B?WjM1QVgrcWE3a2JHaWQ0TFNiVmZ2RGxyazBUV2JaOCtxejFMaFJxb3hBczcr?= =?utf-8?B?ZlZ1cWVyR09wQ013WllhN1FSZVIxSlVPdEZOaTgxOFdRc0hYNU1Vd0xVZ29Y?= =?utf-8?B?MThzN0t5OUNMTjVid3lYVnFhQVRiM2V5N0Zzcm1zRHpZT2xmQWo2ZUFYSFhI?= =?utf-8?B?Uk9zUGxmTnhRaGtRUncwaFpFMTRLZ3NrOXFpU0xCdUNFaGVDSEU0NUkzNXZR?= =?utf-8?B?Nk1XYTc4Q3ZXcWxSV1RIMURWeG5sSTlDQ2ZpakJpak0zZm9QMmRIenQ0aXE5?= =?utf-8?B?RE1obSsrQ0hhME1LM3dsS1lYS3RwMFVDTHgreE9iMmZZTDBPZDUrem0yZ3ZJ?= =?utf-8?B?NUN4SFlQbXRCSm0vTWhmQzhkZnU3VUhyVWlBUGpJdmZuNThTVnRjaVdJaVBq?= =?utf-8?Q?UCAg=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR12MB9473.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(376014)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?S1ZkcFNiWHp6Q1ZYNzZxN2lwaTBIT0xNeDF2eVBxOEVRQUt1bEFSME9yY2dR?= =?utf-8?B?eWNRdSsyTVVVQ0hWSWJUSGtNK25RZ2duN0tPdkxwZWQxMTVFYzRBNE9zQ1BS?= =?utf-8?B?SjZiMUdSRFRjdGJ4SkJVbi9uRk95NE1Ya3BMT0V4Z3I2bW1zVDFOODdWMHU2?= =?utf-8?B?ektiN1F6aHQzTVgvNGNQRnNSTFJDb09XdHNtejBCZTNrRWYxZWhaVHF0aWps?= =?utf-8?B?QzhiVVp6N1VLL0RKWDYzM2dxQ3ZWdW5mVC9ZNGtURWtSQ2pzbDZmdmIxNlZr?= =?utf-8?B?SU9zMkIvWWIzSUlmeDArcVh0TG56bmdOQS9RaGlsSUhtQmt3TVpoS1BRcVpu?= =?utf-8?B?eVpISGhWZ2plTlVCZmM2anZldUZjSXo0cHExVnNVWmUydnNnUld4aERzdkwv?= =?utf-8?B?bWk5WFNDcnZJaDJBc0hIVFp5eTFsQWZmZW8vRkdwWjF6YmtwRUQwNXJqWkpE?= =?utf-8?B?VDVzRTVjZ2hQWUEwemVZL2ZWVEhSM1FtT2FmOW9oenE5UkhtWFh0MXI1T0tq?= =?utf-8?B?WmFDd1dxOFhqbnJaZ2lnUy92d2pjNTMreWwvcjdITHM1dTNrOTV1SEdINzJB?= =?utf-8?B?dmg4TCtUa2J1bGdGS3RCdy9IUThJbHBNUGNzdHBFaEpUdWcxUDJ4UGhIYWRx?= =?utf-8?B?UmZBUE1rVnZLMEdkUzN1aXhBZ0Qyb1JIQjRpYmVuY2hGaGEwem1Candrak1p?= =?utf-8?B?MVo0aDhiSHVqMy93TExqcmJzN2VubVRPellmQTFMWUQ5VkxidlZSUHc1bHkr?= =?utf-8?B?b2FqVHBCODlVZmVoZzY3MkNhSDhmRDdhaUVuWmRtRC9VVkJoZmtySUJjQ0Nn?= =?utf-8?B?aTdqc1JacmZjZWJCWFNQVE1ETU5vU0I5dG9SREo4OTRyREZiNHVHSkp6cENk?= =?utf-8?B?MmExd29VMzdmZFMvT1o1NWt2NVVBeDNENmhacjlFVlR5TmZPM3liK21MblBY?= =?utf-8?B?eXRXdFl5RUdwUW9LRHZIbENQWDVCQmxIdFBBbVR0SnU3UEg5Nk05NDllcnU1?= =?utf-8?B?elRxTm91UzJyZG9KQVJYZnVoUnFhREYra0F4enAxY0cyZ0NxK0FiMVgvaytM?= =?utf-8?B?dVV4amE5b0FtSkR1U09wVTVWblpXa0IwcC92blljd2xzVFBpakFFeHNtaTRi?= =?utf-8?B?aldSVzFNWE14TVFQVVBoT3FqWHdsdzMxeXFqdEVHZXE0TkZ5NWgzTmhBNXVG?= =?utf-8?B?RkRXR1FxbVo2U0lhT3F6YW9Zd1pMMFp2TzRucHVndDRQeGFEWHBvelJBR3dq?= =?utf-8?B?R05CcDZnSEs3Nm5jdGlvUjQ1U2JkS1F0Witjd3BIdWptUFpuT3Q4djRLV0ZV?= =?utf-8?B?M0Y0V0ZIRkRja0IxT2QrOU9YY2FpdlFidWxzTm9wN1MzRDRzM1NHemU3WUVo?= =?utf-8?B?dHV0emkvTXNUMHBCdkY0dzVpRjJOYnY1czJwNlIyQ2huRENYMkR1M3BCcHhk?= =?utf-8?B?bGhKd0Nsdjh1b1l2RXVzRWY5cDRLTm5VV2tiTGV4OVBLZ1FJN0tCcGxodTd5?= =?utf-8?B?dXJZRFNYRW12emZienpYcGFwWGJ5VUJpMGljQ1NiaDM1eE5ydmo0bkFPMDJR?= =?utf-8?B?NXo2VmZPSlB2VmZ3MDk1ZmV6b0FjNGZOQlE2L01RWURFdm11d3V6djg4SzBx?= =?utf-8?B?V1hzNi9UOGJ0NituV21xUjQ0QVcxZ2RFSUtKem5qQ3AvWEI2d05GNnZrbUJ6?= =?utf-8?B?R0xFSndjczR3djFuRFR0SlB5K2pxeU03eU1QQ3NXOE1JMGxTMWJLNGNmU3E1?= =?utf-8?B?Ui9ZYS9WTGRRR2tSak5JdWhwZTJFZVhzMGVzVVdFWFU1WGlQdER0YTFZN09H?= =?utf-8?B?cGd2ZWMxa3ZtWXFwT1BPTzdxb1l2MDl3bVY0L2VIaUJPdWJYZlo1cGxRRFBY?= =?utf-8?B?QVlpdzFLQ29iSi9zSEZvUWJja3crcGg3dUh2Si9rOEF1Tkxxc1NCR2hQL2lQ?= =?utf-8?B?L2gwV2dud05RSC8xVXlkdEJkSmx4R0gwb0dwb0NnTmxUTTdzNGd3UmVmUDBx?= =?utf-8?B?Rk1IeGpCZXVKU3RWRTM4OHNDUStCU1JwTVlHcGg1K0VwWktWQUgwazRzdXk1?= =?utf-8?B?REUwOGVSVUMyUitIUFlGSUhTZmo0VXY2TWxpaVZVbWovWVNnUitpV2hrbFBM?= =?utf-8?B?UWpFZXFCU3I1a0pTNldBZ3JsYXkwRmNRQ3lBdVY3QklkMkVoaU9MN1BsMG9s?= =?utf-8?B?Y1JjS1BRWmhCZmNHaVFkaW9WWTcyWkI3d2phRmVnL1AzM0djZGN3VHdudUQw?= =?utf-8?B?M0UyQWJzNEN0bGZoZ1h3SWRrNFV3TkcwQXljdmprK1htbGVhRlRtbll5bzhR?= =?utf-8?Q?5YmocmvO2rwhEJubEj?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8e4b5080-e77b-415e-83d9-08de6413ab3e X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Feb 2026 17:34:37.4857 (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: dQaq8Yjbf2sQhKrlkSJE5faUCuAxFHidhOtoEdfU/ExR2E95fslQbfgJScUPmqSi X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB9002 On 4 Feb 2026, at 12:23, Zi Yan wrote: > On 4 Feb 2026, at 12:15, David Hildenbrand (arm) wrote: > >> On 2/4/26 18:12, David Hildenbrand (arm) wrote: >>> On 2/4/26 13:49, =E6=98=AF=E5=8F=82=E5=B7=AE wrote: >>>> Hi, >>>> I=E2=80=99m reporting a reproducible WARNING triggered in the hwpoison= / memory_failure path when injecting a hardware-poison event via madvise(M= ADV_HWPOISON). >>>> >>>> The warning is triggered by a syzkaller C reproducer that: >>>> maps a file-backed region with MAP_FIXED, touches related VMAs, and th= en >>>> calls madvise()=C2=A0with MADV_HWPOISON=C2=A0over a large range. >>>> The kernel reports a VM_WARN_ON_ONCE_FOLIO(1)=C2=A0from memory_failure= ()=C2=A0and points to include/linux/huge_mm.h:635, suggesting an unexpected= folio/page state encountered while handling a poisoned compound/huge folio= . >>>> >>>> The target page appears to be a compound head page (order:3) already m= arked hwpoison. memory_failure() seems to reach a branch that unconditional= ly warns (VM_WARN_ON_ONCE_FOLIO(1) at include/linux/ huge_mm.h:635), which = usually indicates an =E2=80=9Cunreachable=E2=80=9D/unexpected folio type or= state transition in the huge/compound folio handling logic during hwpoison= processing. >>>> >>>> This looks like a kernel-side invariant violation rather than a pure u= serspace misuse, since the warning is emitted from an unconditional VM_WARN= _ON_ONCE_FOLIO(1) site. >>>> >>>> Reproducer: >>>> C reproducer: https://pastebin.com/raw/UxennX2B >>>> console output: https://pastebin.com/raw/wrhKRwZY >>>> kernel config: https://pastebin.com/raw/dP93yBLn >>>> >>>> Kernel: >>>> >>>> HEAD commit: 63804fed149a6750ffd28610c5c1c98cce6bd377 >>>> >>>> =C2=A0=C2=A0git tree: torvalds/linux >>>> >>>> kernel version: 6.19.0-rc7 =C2=A0(QEMU Ubuntu 24.10) >>> >>> @Zi Yan, this is weird. >>> >>> We run into the VM_WARN_ON_ONCE_FOLIO(1, folio); in min_order_for_split= (), >>> which is only active with !CONFIG_TRANSPARENT_HUGEPAGE. >>> >>> But how do we get a large folio in that case? folio_test_large(folio) s= ucceeded. >>> >>> I think we rules out hugetlb before in that function. >>> >>> >>> Looking into the full console output, this is an order-3 folio (fully m= apped). >>> >>> How do we end up with a large folio here? I am only aware of that happe= ning when something would >>> allocate an order-3 compound page (not a folio) and map it into the pag= e tables. Yes, that >>> is nasty and can still happen, not sure yet though whether that is real= ly what the reproducer >>> triggers. >> >> Looking again, >> >> mapping:0000000000000000 index:0xffff88800fe2e600 >> >> At least mapping=3D=3D0 could indicate a non-folio thing. > > From the C repro above, syzbot opened a dev "/dev/sg#" and did mmap on it= . > Is it a device driver issue? OK, it is CONFIG_CHR_DEV_SG. And the driver allocates a compound page at[1]= . Since we initialize folio fields in prep_compound_page(), it becomes a foli= o when it is inserted into a VMA. It seems that my compound page and folio code separation patchset comes rig= ht on time[2]. Basically, compound page should not be a folio. With !CONFIG_TRANSPARENT_HUGEPAGE, __GFP_COMP for allocating a compound pag= e that is used as a folio should be rejected. [1] https://elixir.bootlin.com/linux/v6.18.6/source/drivers/scsi/sg.c#L1868 [2] https://lore.kernel.org/all/20260130034818.472804-1-ziy@nvidia.com/ -- Best Regards, Yan, Zi