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b=No4ehdGc74tkhPesz0WG8j+03OUgrdaLCpdJtbi3UeXD5Bu3k81AsI/QRjmQ8RAPLAptmnl769wu5ZFhIF86G67MI3aV3dqh04ZC081/boFdSTsF04bolYu+begF9+jzET8W/JqTEX7LwxlnLlfM2xPac1GWqT9ZuFFhq6GU+7MNF1W8PUiL5senZxv8rEtWXOQYUcmMpwJ3nc1tUU7E9C2fpdz+cWht0vrmiVGne20fpjRIaDjvYu9V0nSIbvdSIdmshYToq/sXSVgxGe3y7bnkKp0ewdIMAmqv0P3j8yJN8gR6XsLGQSW/e4YEWuj5IjL8Si7zEYL0ewX0ci+ZWA== Received: from DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) by DM4PR12MB6326.namprd12.prod.outlook.com (2603:10b6:8:a3::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7719.29; Mon, 1 Jul 2024 23:53:21 +0000 Received: from DS0PR12MB7726.namprd12.prod.outlook.com ([fe80::953f:2f80:90c5:67fe]) by DS0PR12MB7726.namprd12.prod.outlook.com ([fe80::953f:2f80:90c5:67fe%6]) with mapi id 15.20.7719.028; Mon, 1 Jul 2024 23:53:21 +0000 References: <74a9fc9e018e54d7afbeae166479e2358e0a1225.1719386613.git-series.apopple@nvidia.com> User-agent: mu4e 1.10.8; emacs 29.1 From: Alistair Popple To: David Hildenbrand Cc: dan.j.williams@intel.com, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com Subject: Re: [PATCH 09/13] gup: Don't allow FOLL_LONGTERM pinning of FS DAX pages Date: Tue, 02 Jul 2024 09:47:03 +1000 In-reply-to: Message-ID: <87le2klleb.fsf@nvdebian.thelocal> Content-Type: text/plain X-ClientProxiedBy: SY5P282CA0115.AUSP282.PROD.OUTLOOK.COM (2603:10c6:10:20b::20) To DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB7726:EE_|DM4PR12MB6326:EE_ X-MS-Office365-Filtering-Correlation-Id: af2a5d09-3cd5-4c37-1ec5-08dc9a28fcee X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016; 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However a future change will cause these >> checks to be invalid for FS DAX pages so make >> folio_is_longterm_pinnable() return false for FS DAX pages. >> Signed-off-by: Alistair Popple >> --- >> include/linux/memremap.h | 11 +++++++++++ >> include/linux/mm.h | 4 ++++ >> 2 files changed, 15 insertions(+) >> diff --git a/include/linux/memremap.h b/include/linux/memremap.h >> index 6505713..19a448e 100644 >> --- a/include/linux/memremap.h >> +++ b/include/linux/memremap.h >> @@ -193,6 +193,17 @@ static inline bool folio_is_device_coherent(const struct folio *folio) >> return is_device_coherent_page(&folio->page); >> } >> +static inline bool is_device_dax_page(const struct page *page) >> +{ >> + return is_zone_device_page(page) && >> + page_dev_pagemap(page)->type == MEMORY_DEVICE_FS_DAX; >> +} >> + >> +static inline bool folio_is_device_dax(const struct folio *folio) >> +{ >> + return is_device_dax_page(&folio->page); >> +} >> + >> #ifdef CONFIG_ZONE_DEVICE >> void zone_device_page_init(struct page *page); >> void *memremap_pages(struct dev_pagemap *pgmap, int nid); >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index b84368b..4d1cdea 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -2032,6 +2032,10 @@ static inline bool folio_is_longterm_pinnable(struct folio *folio) >> if (folio_is_device_coherent(folio)) >> return false; >> + /* DAX must also always allow eviction. */ >> + if (folio_is_device_dax(folio)) >> + return false; >> + >> /* Otherwise, non-movable zone folios can be pinned. */ >> return !folio_is_zone_movable(folio); >> > > Why is the check in check_vma_flags() insufficient? GUP-fast maybe? Right. This came up when I was changing the code for GUP-fast, but also they shouldn't be longterm pinnable and adding the case to folio_is_longterm_pinnable() is an excellent way of documenting that.