From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from NAM10-BN7-obe.outbound.protection.outlook.com (mail-bn7nam10on2069.outbound.protection.outlook.com [40.107.92.69]) (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 0460B2063FD; Fri, 1 Aug 2025 16:29:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.92.69 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754065778; cv=fail; b=dTDHJ4lzBV+HQ0tSanVAG5GErps5snX+fqmaqRc8moq2dYfEuXrf7IOcQQf+Q/EtKu+bKLZVlzqQ4IF++Dh0t0aoVCQCJcdNR7sL6qdZj+PyGcZ1rMOw0HVVwuhE0oQ53FbWa9kR+qoPmsdPfVhR1+9uuWGEbVioJsPxPZFXhdQ= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754065778; c=relaxed/simple; bh=yLcBcgg1fYMuGCl7zYc2TSahI6fel/u3GS0DAiTRaGU=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=H6RsUYzjR9TbtRFTUR7u5bZhXQ0WzQ24ug5FoJQiZHQ8YVapdqvbvAiBhAztaueCM63Ej5oDJ+H1MwXAc2ztYi3x4o0KFU02ptBLsIklWzvEhNI1xGGowBOafd0GEKDcxP33kJQbGDiyrXNRTbjU3Bmjn0gC0AtZ/Gjhxr0w61c= 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=NrLkKbpC; arc=fail smtp.client-ip=40.107.92.69 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="NrLkKbpC" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=D2H3oXkqvw3iZWVinRSowcrxvH6CvkGeTL/+ZUdvL8bW0/37RMuDV4t18Xuz+LcXWX/QRijRUMJ7OLqavw9P7I58dw1yC0HYdoxlUSYNHhPmcDE9qV7hpZiOheJsymqh96VEZC6oCgnWt15AOOhJSrqgZX7GvlsTf3p3CYy+fgUCHngtPyXNe1bCte9eWhYK3mB6q4jz6GYtElAI5kuBSJ4j0xso7m2cStVCytxCriGKqEq2PksqdjncLFuqgPaskFxnA152lq6d5vwTIa+dRQ/kdB1CohreROPIhfr8a+Qi0np+0HOnmMMVihC2ukbno14OUKy31WcFqGPVfZ9T3A== 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=pJJM4EZKVnt3t+yNadjWzDSo/q5ptRkPqEfLmtp2Vek=; b=ILXeVPJliQCoIk2rr5VAfMswza94TrBs/pPuj5fWCEEJeo2oovTaGGPBWYNR8Nd43KFMl8PFudR9JT8hwUMd7NDgJbMStELQnqXktDH/F5ETtZahuTnTbQ7QH14EsZk2tV+/z0XDq4DpGsqXR8TV4E/cIG0LXjP52VTNj1z3Jj6dRB/RVsk7s0jnG9hdgoYQkS2k3nIowByQDn2Fi8AtVivopQZ3gQRAib1esjYJN5fdOKj/byR3ziF8VV/WNZnjTL8+TOjdTVKaT0QXTREyY4tJEzuzYkMLAnL6F3Eyo/7hWjCUaY55L2v+KXmyDW7606yYxnRSJ9nczIcvr6MuwQ== 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=pJJM4EZKVnt3t+yNadjWzDSo/q5ptRkPqEfLmtp2Vek=; b=NrLkKbpCsA0Fhbs1RpvCKdnnNKewsB12s0tHrlta3u2r3eW1+5fTMLp6SazG8aaK3jgobNjtZEXMpzCFlSFWOVjwRzyx7AaBtbvuc/LqOA8i2QVD+fVwqqiJ7jbvnU9O0/GCv3P3FPCXbKwEYUZdujH50MRv8rKv8ihVc5YOGYGL5/5CLAtMSw1Kz6vRCcnUcNFemsSxwr3puRshb/4cppkjWPSSn6gmL+1XXBoZMLtOb3QQwZ9FhaquZjGfHaFSj+oObiOI4rWPL1p5gTHP1X6aH81ynLoI1ydzlcyo80jXZ2hrTHZZkwzLk2K4NeJ8pDUH8GuMi1FPUBc7NuIpow== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from CH3PR12MB8659.namprd12.prod.outlook.com (2603:10b6:610:17c::13) by PH7PR12MB7281.namprd12.prod.outlook.com (2603:10b6:510:208::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8989.17; Fri, 1 Aug 2025 16:29:31 +0000 Received: from CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732]) by CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732%7]) with mapi id 15.20.8989.011; Fri, 1 Aug 2025 16:29:31 +0000 Date: Fri, 1 Aug 2025 13:29:30 -0300 From: Jason Gunthorpe To: Lorenzo Stoakes Cc: Andrew Morton , "Liam R . Howlett" , Jens Axboe , Christian Brauner , Jan Kara , Amir Goldstein , Kees Cook , Josef Bacik , Matthew Wilcox , Vlastimil Babka , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand Subject: Re: [PATCH 00/10] convert the majority of file systems to mmap_prepare Message-ID: <20250801162930.GB184255@nvidia.com> References: <20250801140057.GA245321@nvidia.com> <3cf76128-390a-4ef2-85a7-e3ee21ba04b5@lucifer.local> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3cf76128-390a-4ef2-85a7-e3ee21ba04b5@lucifer.local> X-ClientProxiedBy: YT4PR01CA0157.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:ac::29) To CH3PR12MB8659.namprd12.prod.outlook.com (2603:10b6:610:17c::13) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR12MB8659:EE_|PH7PR12MB7281:EE_ X-MS-Office365-Filtering-Correlation-Id: 88bb2e3d-65e7-4277-8328-08ddd11897c2 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?6bXujqj7XFkkwTg7yoVHCuHF8Nps+EKlGQpwW8mdbUqIvef0BJ8fYwakmBZD?= =?us-ascii?Q?v0GOtVYLkHpPuY+5EdM6/IojMBBtfmqDUopiVRtQ5p8N1OapSl0GCXfPA6eA?= =?us-ascii?Q?lSSn2GPqJTDNRFafqPn3UpXU1br4ihDNzdYNujF4TySO/KC3059Dr1BislNN?= =?us-ascii?Q?qR0rNu8356CT2DheqSHsxWRRj/CFJ868tTaiM/aW1ps3yWbfviRfs8m1rwzc?= =?us-ascii?Q?Lm6ErqBWVlUAWMDcL+1ucvouGb7nn0fZm8BeTQc8j/WcgMS1fgexAT58sVxL?= =?us-ascii?Q?DWGDQFtghr44ishsDP22wUYoM5Q8ngqjd6jc49dqHyxbM9NddO9H2wVd0HT1?= =?us-ascii?Q?OaOUdTQUwwBj2MiyKpT8fmbclVN11QdETWNWpvbP76q+1Qz+Ni0EYJJmGfq3?= =?us-ascii?Q?4jVu9bCn9BFUpLkOzw1tO2lOcrSARgLOPFJmoSI664e3soPvCJnz7wVbgf1v?= =?us-ascii?Q?N+KDasTr2q10RCLKxQAvV5T6PNWdxbqc72rHe8cYfdYj4tSR98TvBjFQQno+?= =?us-ascii?Q?qMPJqzskfIsGFHPcX8CNLvmdTSLlzuw3Sif6ttMs9rEb/7JV7/sv8ZyIOJuv?= =?us-ascii?Q?8aGNoxMsKfbjkFAjJmxfbTSAnLxbkCwlVw8KhwGoOTrGwVofVrQELggwfX3A?= =?us-ascii?Q?9ufQV7wesutA4YyPDBTnbRJD98oRLYpExU8lzloQ535OMcrtMJf0uy6ys5ca?= =?us-ascii?Q?itjYPYjg+nTkLkYl0HSEkcSGoWn65CY4XQewO/f3mm4w6u9on1s4rsxmvHJh?= =?us-ascii?Q?C4dnLOjS5XZPfZnWNB2YEpzagE5bEelMYM+PT/DlHrxnqvObM7qL4CBTWYxu?= =?us-ascii?Q?1BFlhR7eKW6M+yicQQgmoA8C0olSF8wNry0E1OMZaycbDx0J5inujQPgKvp+?= =?us-ascii?Q?yaH1eTXk44Vu5rLJLytQ9HhkWL4X7fVtkFPgn4zuuVkvKnzsvoarzTuKxw9+?= =?us-ascii?Q?3Puk/+7W1v9EL7+7veImaYqjI4lKzawmy66CcKT5yVKtRtOsOWxdZa4Kxtvj?= =?us-ascii?Q?L03ikyjDG2/qQaNYwEN30yGgivqDl4o+BNR98DmHCjdam1wPD7yn8St0+s0M?= =?us-ascii?Q?eP3zFfUGPc/M55utLQTW4yl7xztbzld26vAMQxBw7Kd0TH/2noV3rIWP9nbw?= =?us-ascii?Q?nWO6d7HAlF4+4y2xokdOMdXBt1QmdtHwmVP8481QH6oqomd4Lutq7XmTvxsf?= =?us-ascii?Q?fS3zRP4wNNN8if6NGfiaNJ+SZK7Q1OKMZBZRa9mhvbe0gFByS2vLbaVxbhgE?= =?us-ascii?Q?6CllMgL9/yqjZkohpKx1WdfH7WDi+jgOq6wy2iIQ3GUZmnYci5HVJFbA5/Sx?= =?us-ascii?Q?IZDrRqwOt8WaUEQj1lL5tpGwU113a41MIfGcxQbb1HzMttD+9E6wvHmkLiof?= =?us-ascii?Q?KhD/2WqJBl0gZGPCoXVSPY+/tkkEnxGbx98qtUXu9jzb3jewfw=3D=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH3PR12MB8659.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(7416014)(376014)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?/eCvRK1UlY1d6/9xJaFu5mW7W/n6j/XZnxDxlI56LkBAXpds/JRuqfponf+/?= =?us-ascii?Q?OGgBAb8789of5qfqu30SCpIvC8/4m4C0uR/C11vBHBxCHlpM1KAJNUTiqe8X?= =?us-ascii?Q?eKR/1t6lHgAZIuB/V8TsdnAMn3HPwbaLVourho32nuLb9ho172GQbURu0WF6?= =?us-ascii?Q?lc2Xeowz5XXLCXYqXhTJVL+XM6PKjchUTyMX0wb9ASp90se4IY9L0waHvWqS?= =?us-ascii?Q?L2geEJBSRN439jOYJqXplZuPFmYelMYxQHI7ngvpiNCvXwKBH1Yiv85ExJjl?= =?us-ascii?Q?pJaVzHhJZqh/4tCBNUzAT6LrvGmoNa7/X6u4qE9AV+B2UgQXcwei/Zvo2pP5?= =?us-ascii?Q?gqTzNAsGxYvR7XAASYd0TPdweK6h8DAyEjZgmyus3XNdXiccFCp7VcW7NFck?= =?us-ascii?Q?higm5i8fKMSJ4N7nfvGbdJG7VAAAhK7VEDS9i0uzksvPSiJ/GUDV8E/a7GVB?= =?us-ascii?Q?dhJ4kwezOoE7YAf4AJvCwpvPdbnpHm48L3zHmQwRLXyyea/wn2Cg5bu/kQFw?= =?us-ascii?Q?mYR7/VDqx3H+WWoI3pJIu7Wow/bPxxkEgvBptf9VJB6TCZR3Q51HZ3VxF6SZ?= =?us-ascii?Q?v0C6G56EP7IRtra9wJBTH76rPG1KHRJ8Tco9CMVdxVS0/e+ny41sgoBaMUz8?= =?us-ascii?Q?1X+9G2uiyDgy7fmHYaaVencFXIm/hbC4RiR1/ranlgChYGwrygV9hehAD7fW?= =?us-ascii?Q?tOi56yTdC7DBhCcWoytgQCC9SwahzJaa21lHOlSqWHX7DXk6ydQRjCyCYBKk?= =?us-ascii?Q?4hI2IJ7X5EGUxw1YIbd5qTdD3uZC7rBTsiaFiObn9Tr8D8w6OdVi1CcynEP7?= =?us-ascii?Q?eFdOL+6D7WlVNbi9EbPiBETQLvQOU95wZzsaNfYgHU5lJ5lFPpzw1QrbJHeD?= =?us-ascii?Q?THbuY64qNV5Elfvaxy/P+w/l6/q0TKwERE9u355vyeSWXKOmHMqBZceozNnb?= =?us-ascii?Q?pRG0icZHhMSQOjuY9NYW4z+GPo2ka3QlOr45T8T1bF+JTKUkhxpZgEeGvPHI?= =?us-ascii?Q?BDMXy4WZVbhqV2hrOcd2OwIyq+7CeiGLKUyIHNX3w9TwyeuLld7Xqu6QOJwX?= =?us-ascii?Q?pLdRlL23t/g1JzsqCaud5rUw5dTADYZOpQE/lPACEYgZEnEhFyaXumqmDmMr?= =?us-ascii?Q?zWp7KL+EVdje+uLexocE69V97Vfkv7lBSqYovcVoT9BRihn9vBlDrkB28Lsu?= =?us-ascii?Q?mmUIi0ZN77zSbw/aYBo0Kwmlbkx0z7vVkPwvVWTV3ToI8kgAoNkTZeeLhfSq?= =?us-ascii?Q?0sem4ksVT3ZnFTeEo/pbU5xhbZXquFbf7Qby/4eisN6VBSumOoC/jWxX/IJI?= =?us-ascii?Q?fp38SMGcCFth0idJa/7gSs4zMgVBuup3sksjdqmGkE8zQURWm2zEYA7OV6Zh?= =?us-ascii?Q?MSx7Um+XAXDUeH7VE25LMFU2s5ECoIx34Hed7fy9Pf3lk4tXrdrAVtTqtSaF?= =?us-ascii?Q?ZQ3YEa40Nhe6Rjb3jkuMwDYE0Aa52sx9E7F8VC5H61rJBpc8kVgFTiy1lcCS?= =?us-ascii?Q?w11LpmbV0a5JenZGeU5W/YRmEx+6669zXGSROiEDzXOJrquRlNPAUdafk4AF?= =?us-ascii?Q?JnPTkA+uKWhtrbyHuRI=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 88bb2e3d-65e7-4277-8328-08ddd11897c2 X-MS-Exchange-CrossTenant-AuthSource: CH3PR12MB8659.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Aug 2025 16:29:31.3585 (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: F6pt/ZToG53hF2HArccnZg2upkh5UNLJe4eGTZmksj4NCMoklVLXZUEaEM01Z2EQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7281 On Fri, Aug 01, 2025 at 03:12:48PM +0100, Lorenzo Stoakes wrote: > > I would like to suggest we add a vma->prepopulate() callback which is > > where the remap_pfn should go. Once the VMA is finalized and fully > > operational the vma_ops have the opportunity to prepopulate any PTEs. > > I assume you mean vma->vm_ops->prepopulate ? Yes > We also have to think about other places where we prepopulate also, for > instance the perf mmap call now prepopulates (ahem that was me). Yes, vfio would also like to do this but can't due to the below issue. > > This could then actually be locked properly so it is safe with > > concurrent unmap_mapping_range() (current mmap callback is not safe) > > Which lock in particular is problematic? You'd want to hold an rmap write > lock to avoid racing zap? I have forgotten, but there was a race with how the current mmap op was called relative to when the VMA was tracked. ie we should be able to do CPU0 CPU1 vm_ops_prepopulate() mutex_lock() if (!is_mapping_valid) return -EINVAL; mutex_unlock() mutex_lock() is_mapping_valid = false unmap_mapping_range() mutex_unlock() And be sure there are no races. Use the lock of your choice for the mutex. The above is not true today under mmap, IIRC the VMA is not added to the lists that unmap_mapping_range walks until after mmap() returns. Jason