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Wong" , Christoph Hellwig , John Hubbard , linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org Subject: Re: [PATCH v2 05/18] xfs: Add xfs_break_layouts() to the inode eviction path Message-ID: References: <166329930818.2786261.6086109734008025807.stgit@dwillia2-xfh.jf.intel.com> <166329933874.2786261.18236541386474985669.stgit@dwillia2-xfh.jf.intel.com> <20220918225731.GG3600936@dread.disaster.area> <632894c4738d8_2a6ded294a@dwillia2-xfh.jf.intel.com.notmuch> <20220919212959.GL3600936@dread.disaster.area> <6329ee04c9272_2a6ded294bf@dwillia2-xfh.jf.intel.com.notmuch> <20220921221416.GT3600936@dread.disaster.area> <632ba61d7666a_34962942a@dwillia2-xfh.jf.intel.com.notmuch> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <632ba61d7666a_34962942a@dwillia2-xfh.jf.intel.com.notmuch> X-ClientProxiedBy: BLAPR03CA0084.namprd03.prod.outlook.com (2603:10b6:208:329::29) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN2PR12MB4192:EE_|BL1PR12MB5731:EE_ X-MS-Office365-Filtering-Correlation-Id: 29c44de1-b3ac-465d-220b-08da9c2eee12 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=XYct6Qob; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); spf=pass (imf04.hostedemail.com: domain of jgg@nvidia.com designates 40.107.243.42 as permitted sender) smtp.mailfrom=jgg@nvidia.com X-Rspam-User: X-HE-Tag: 1663805462-996224 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 21, 2022 at 05:02:37PM -0700, Dan Williams wrote: > The scenario I cannot convince myself is impossible is a driver that > goes into interruptible sleep while operating on a page it got from > get_user_pages(). Where the eventual driver completion path will clean > up the pinned page, but the process that launched the I/O has already > exited and dropped all the inode references it was holding. That's not > buggy on its face since the driver still cleans up everything it was > handed, but if this type of disconnect happens (closing mappings and > files while I/O is in-flight) then iput_final() needs to check. I don't think you can make this argument. The inode you are talking about is held in the vma of the mm_struct, it is not just a process exit or interrupted sleep that could cause the vma to drop the inode reference, but any concurrent thread doing memunmap/close can destroy the VMA, close the FD and release the inode. So userspace can certainly create races where something has safely done GUP/PUP !FOLL_LONGTERM but the VMA that sourced the page is destroyed while the thread is still processing the post-GUP work. Jason