From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from NAM02-DM3-obe.outbound.protection.outlook.com (mail-dm3nam07on2051.outbound.protection.outlook.com [40.107.95.51]) (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 2ADAF2C83 for ; Thu, 14 Oct 2021 23:04:44 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=oR3LLr/ku7WnG40FcOGo8N7SjYA2neNgXdfWFubg+rYTqQw/BFiAMjRoiOMWJEQBBdqMz6DY4FSlJuUUrDca49fCpTOa1lAkjeK0i8b8El3FF/diDVkVCj6yjOajuOLoHvySk0NlgFqbMVLTAs4BPhd50dh18KZtXhZ/1cO04428SBYlJemgyDawXzb0+kDriK04b18Oa8rgVKp9/9ziozAJb45sAhYJhHfq9r35w3r5afG2s3MujzOxOtw2J3sa31BtcdV+eFmc93Sh1kNfCwh42dr40eRvxZwQWU/yqFMgo81N+RKcCYT2ULnO2+qh+5CyOtSfJ74SMXJLNv+mpA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; 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=PsRiEWe/d6d2z7ZLk193dD9GuSjtElrsts+h68rBERA=; b=BeIivjx+u60nMmWYZl8S9VMJcnazdPYEIvOqtWSzaFikcWCg1mG4pmRM5iiPf/L7jl5Zy3QOSkvwG7asJMl0eDS6z1eWNbs6N0Vo5bcPoUnzN49K9+nTfB8Oum1al55KF94fobSIoo4+AaBEnMQw00HII1eXOkZnpZNoDlSislpm0m1sRiAXSXUxE3Wk3nCoOwEF3+hS4ymh7fgFm+lgOsiBSTwprFjdyIygD5OGZFhMh6DlQ8TTVQIQDlPhcDQjCyKskETnPZ8hEOK/aoZQNe1gjXYaaAk295NbpVcPJ5SZAZi7aipVnL8ltt0RQ/wYSROZHMGD+A25aSSMJp8ESg== 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=PsRiEWe/d6d2z7ZLk193dD9GuSjtElrsts+h68rBERA=; b=dScJviROFP4hUwdwXoozoRV/Az9J3rs5iQdOKeM/umv8sjv7Uoplfjg25H0a43QSIquoFmK66vFcuxHQ8oO/06ddj0io5S5HphFDbZkNcK2RafbdlzcLYkgW2W/9FpxCZki5QvWpHNgNqTDHfp72HVaV2BkFhdNLj2KOAbq9CECukt/dgfJFliA67LxuWTZWYyIdEp7ffJ9sJudbUhcfNAhx9ZVjwgva/yf1K7K2CKNGaS3jUduXlY16RvaCitUfxwiP/Petk+7CVqIMXieTC/IzFMM+T04mVLGrY6U3mby86RXYgdIlCbSMCZQzBk+Uu7MXiIZGAFi7r8mLhV39uQ== Authentication-Results: intel.com; dkim=none (message not signed) header.d=none;intel.com; dmarc=none action=none header.from=nvidia.com; Received: from BL0PR12MB5506.namprd12.prod.outlook.com (2603:10b6:208:1cb::22) by BL1PR12MB5318.namprd12.prod.outlook.com (2603:10b6:208:31d::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4608.15; Thu, 14 Oct 2021 23:04:42 +0000 Received: from BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::e8af:232:915e:2f95]) by BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::e8af:232:915e:2f95%6]) with mapi id 15.20.4608.017; Thu, 14 Oct 2021 23:04:41 +0000 Date: Thu, 14 Oct 2021 20:04:39 -0300 From: Jason Gunthorpe To: Dan Williams Cc: Gerald Schaefer , Joao Martins , Christoph Hellwig , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Linux NVDIMM , linux-s390 , Matthew Wilcox , Alex Sierra , "Kuehling, Felix" , Linux MM , Ralph Campbell , Alistair Popple , Vishal Verma , Dave Jiang Subject: Re: can we finally kill off CONFIG_FS_DAX_LIMITED Message-ID: <20211014230439.GA3592864@nvidia.com> References: <20210820054340.GA28560@lst.de> <20210823160546.0bf243bf@thinkpad> <20210823214708.77979b3f@thinkpad> <20210824202449.19d524b5@thinkpad> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MN2PR17CA0033.namprd17.prod.outlook.com (2603:10b6:208:15e::46) To BL0PR12MB5506.namprd12.prod.outlook.com (2603:10b6:208:1cb::22) Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Received: from mlx.ziepe.ca (142.162.113.129) by MN2PR17CA0033.namprd17.prod.outlook.com (2603:10b6:208:15e::46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4608.15 via Frontend Transport; Thu, 14 Oct 2021 23:04:41 +0000 Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1mb9mB-00F5Lu-Sg; Thu, 14 Oct 2021 20:04:39 -0300 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 16b44d7c-f93e-4a1d-7e63-08d98f67010c X-MS-TrafficTypeDiagnostic: BL1PR12MB5318: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: rLBJbqwqwMh8wdtXzr+l85qjfzagUZajUGl5Pf9mkmRMmojzB3Gw8pD0KWmgRGPnJ/+HcjZyzAttiI+PVqstnnybt539lWdNh5n2KKOxe+IdgG+CpXgQPXqwbkH4RcFFjW8iC/OuzPK9SbzsSO/g4MfO9ss+oPg5gSpE70FCaZu2ycu8fgtJ177NNc36rMZDsLaczIs6Wp2A6j7RWwoJi+9vaTGQSlSM1PyhMbOFtxeHk80Tk7Cyd93DYtnMGG+rCm5Skn/F0jo5d67HdK66DV2nVVkSZg1MhFegVLMtGaIANfxjeUqmqsCPab5E4M2LyHvy+rS7WpQzwylYDn27Q/mmaa22hRWoxAeNpjfN0lVsv1Y4wKaFa0JFP+on5ylbEK7m6piAeOiVEa2sSZj4Ik9J6dxr5X27Ljeljxq2EVs0MHhEaRUkI0rufFcYh2LWfiAgYjjXvUFEa4H08X3dt+xEboxFGdjAyTrErZaYzcRcUXfMw9mOz9fbCew0wGQ0U+QEue28U3+j2s1gz4qZ+tbtVPbAe1lSnkemDeo3RifbmlWDHofpShjfzKacDnMzr7dRQz7lCCWxqvcVSKJh+wnk9XVj1Dc7V+HWpmgLxgtkhPfIcrKcw6zreEeCGawfgdQ6p8cCuHRhmH9mKG1E5CLwr8TsR92P+0IFJOIyXwazLN00G6O3UuRwbBxj1Uc9+pMlwwDoBP7vTEHSKCqqnanE/u9ftmCnisCKFFUOFXo= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BL0PR12MB5506.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(366004)(7416002)(966005)(54906003)(316002)(26005)(66946007)(38100700002)(6916009)(9786002)(5660300002)(4326008)(2906002)(9746002)(508600001)(83380400001)(33656002)(186003)(8676002)(2616005)(426003)(66556008)(8936002)(1076003)(86362001)(36756003)(66476007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?R/n3IeQxGS1+8lwtwU7sCfzx1txbBkvrxv0ONyDukGdhQwSluI/EisEDNYtJ?= =?us-ascii?Q?uQTOy4N4oBtF5EZvkIYNl/HICFxzEaixjIq3AQ9vJgg3N1CKx6Ki0SOBpNUG?= =?us-ascii?Q?ScyQFdBFecqS1NEe3ifRW5H+KwkqaYx9gx520lcNpIKb0KEjUlyUEUEgGPXY?= =?us-ascii?Q?nsAUXgP3FEzCcPZmFTRUdHGG92+ymZeo0OsGkqEO120Q4nMzh/SjbkNkLKUH?= =?us-ascii?Q?Tut1JbcqXsyPhL2BIOdw7e1yysiES0/Ngg6h/gNB12YYKjqH4Yk9cbaF6hMF?= =?us-ascii?Q?W+CPmFlvkCfR4UPNsNavxow12aLtGgejROMKoPcR77sKj/9gLPUIjd7pPNim?= =?us-ascii?Q?p1trtKEpFwXMBuW8gTRknYLPXujGQrT+3s8HkR9fDpgI3MuvGv0rcv2XbN+n?= =?us-ascii?Q?pk4MZT6xfVuGs2FsiGQqOco+Gw4kjvOjRpCm4pUdyY9KcgELEMIZjNhoCvQJ?= =?us-ascii?Q?SuEpom4ZygeA1LZIzwYPYwntpKkQYnMU0LmAe5rZr1OOcqba3rwquohm/dYM?= =?us-ascii?Q?aAQqpbJle4APeHJXW/S4AgUH9+LGiQjQAMqulY+P3/SsDGUtcPxKF7pkDhsV?= =?us-ascii?Q?aUtxD6cYWNnQeIh1x0bJA6xsDOORkpuMxHxrXOLT2xPXIZmLcDJS2h9bcIMZ?= =?us-ascii?Q?5+zVOpvgGuSRuBpV4uhuJpOpozPDzpqCoVZ0ZBDTULT9PNJTTAfzlh/IJ4ZY?= =?us-ascii?Q?pMpxYS4DMOfq2no22NpU9To3dKBe4Ocqzi2Typv6t8eo3h43+V+QVNMVzuxR?= =?us-ascii?Q?/ON1uOt9FZ4hzGSYCV3pTVPq3hOxHscLZ8LJ3jfmOpuhN0meUlw/CDcaEZPC?= =?us-ascii?Q?R+hOSylZBWB6+yEwo5TMQeZxpvigYZjBFNOjELy0wluOZuuQzypHNKlumG1N?= =?us-ascii?Q?FswBOVdMKVK80Zc3qgGe8ZC9qwjMlnUeaQCC2cp8WIm27utksbfpFI54WUDh?= =?us-ascii?Q?8oMLYWTZdXbggaT7skTdkt2uNF3VBtZRxptl32s28KPlAWi6Psz9Z02EHsPK?= =?us-ascii?Q?jRVNGsTaRJAS1GmGv8vr/B1y9Tve5NTHndXpy17PfhXXQZvrwpiIpXTqfzGB?= =?us-ascii?Q?0ADZRdjjivfqaJyuc2y68EeL0XG1h63I3vj5kEnNNDOeYp3WXxuM5zmaRVJD?= =?us-ascii?Q?Z9jZ+66JjkrSR/ux+74hqSP83LDiA0RMfWwGxgGamMzHPjvPqdnbp71yFUgx?= =?us-ascii?Q?w1Vhclk6teX36a/CEjVA34v5XPAQ+XDcSReLbgf2d8nwWdtrhyDUC8TCloVx?= =?us-ascii?Q?Q8VeYp5ndbr/Afpc14psU2wuV39J21mTSFRlT4F8tNHjcflYByATkdqkGGgR?= =?us-ascii?Q?txVl71PbaGqTs5voZr/sNN+x?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 16b44d7c-f93e-4a1d-7e63-08d98f67010c X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Oct 2021 23:04:41.8933 (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: lT6up6BjNsGLpIZKlPowb2S/Ky9PF3QrcElGOpniQPF/1WD/jooOTbICH/MOTDXT X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5318 On Tue, Aug 24, 2021 at 11:44:20AM -0700, Dan Williams wrote: > Yes, that's along the lines of what I'm thinking. I.e don't expect > pte_devmap() to be there in the slow path, and use the vma to check > for DAX. I think we should delete pte_devmap completely from gup.c. It is doing a few things that are better done in more general ways: 1) Doing the get_dev_pagemap() stuff which should be entirely deleted from gup.c in favour of proper use of struct page references. 2) Denying FOLL_LONGTERM Once GUP has grabbed the page we can call is_zone_device_page() on the struct page. If true we can check page->pgmap and read some DENY_FOLL_LONGTERM flag from there 3) Different refcounts for pud/pmd pages Ideally DAX cases would not do this (ie Joao is fixing device-dax) but in the interm we can just loop over the PUD/PMD in all cases. Looping is safe for THP AFAIK. I described how this can work here: https://lore.kernel.org/all/20211013174140.GJ2744544@nvidia.com/ After that there are only two remaining uses: 4) The pud/pmd_devmap() in vm_normal_page() should just go away. ZONE_DEVICE memory with struct pages SHOULD be a normal page. This also means dropping pte_special too. 5) dev_pagemap_mapping_shift() - I don't know what this does but why not use the is_zone_device_page() approach from 2? In this way ZONE_DEVICE pages can be fully normal pages with no requirements on PTE flags. Where have I gone wrong? :) pud/pmd_devmap() looks a little more involved to remove, but I wonder if we can change logic like this: if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) { Into if (pmd_is_page(*pmd)) ? And rely on struct page based stuff as above to discern THP vs devmap? Thanks, Jason