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Thu, 21 Mar 2024 06:03:29 +0000 Date: Wed, 20 Mar 2024 23:03:27 -0700 From: Dan Williams To: Alistair Popple CC: Dan Williams , , , , , , , , , , , , Subject: Re: ZONE_DEVICE refcounting Message-ID: <65fbcdaf2042f_aa222948c@dwillia2-mobl3.amr.corp.intel.com.notmuch> References: <87ttlhmj9p.fsf@nvdebian.thelocal> <65f148866bc56_a9b42947@dwillia2-mobl3.amr.corp.intel.com.notmuch> <87y1ad776c.fsf@nvdebian.thelocal> <878r2c6t99.fsf@nvdebian.thelocal> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <878r2c6t99.fsf@nvdebian.thelocal> X-ClientProxiedBy: MW4P222CA0021.NAMP222.PROD.OUTLOOK.COM (2603:10b6:303:114::26) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) 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: PH8PR11MB8107:EE_|IA0PR11MB8397:EE_ X-MS-Office365-Filtering-Correlation-Id: 9e73de79-96ed-414c-16f9-08dc496ca1ac X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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AFAICT the > page->mapping and page->index fields can't actually be used outside of > fs/dax because they are overloaded for the shared case. Therefore > setting/clearing them could be skipped and the only reason for doing so > is so dax_associate_entry()/dax_disassociate_entry() can generate > warnings which should never occur anyway. So all that code is > functionally unnecessary. What do you mean outside of fs/dax, do you literally mean outside of fs/dax.c, or the devdax case (i.e. dax without fs-entanglements)? Memory failure needs ->mapping and ->index to rmap dax pages. See mm/memory-failure.c::__add_to_kill() and mm/memory-failure.c::__add_to_kill_fsdax() where that latter one is for cases where the fs needs has signed up to react to dax page failure.