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Wed, 25 Mar 2026 04:44:49 +0000 Date: Tue, 24 Mar 2026 23:48:33 -0500 From: Ira Weiny To: John Groves , John Groves , "Miklos Szeredi" , Dan Williams , "Bernd Schubert" , Alison Schofield CC: John Groves , Jonathan Corbet , "Shuah Khan" , Vishal Verma , Dave Jiang , Matthew Wilcox , "Jan Kara" , Alexander Viro , "David Hildenbrand" , Christian Brauner , "Darrick J . Wong" , Randy Dunlap , Jeff Layton , Amir Goldstein , Jonathan Cameron , Stefan Hajnoczi , Joanne Koong , Josef Bacik , Bagas Sanjaya , Chen Linxuan , James Morse , Fuad Tabba , Sean Christopherson , Shivank Garg , Ackerley Tng , Gregory Price , Aravind Ramesh , Ajay Joshi , "venkataravis@micron.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "nvdimm@lists.linux.dev" , "linux-cxl@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , John Groves Subject: Re: [PATCH V9 3/8] dax: add fsdev.c driver for fs-dax on character dax Message-ID: <69c36921255b6_e9d8d1009b@iweiny-mobl.notmuch> References: <0100019d1d463523-617e8165-a084-4d91-aa5e-13778264d5d4-000000@email.amazonses.com> <20260324003818.5009-1-john@jagalactic.com> <0100019d1d476420-6b0bf60e-3b3a-4868-8f5f-484cd55d4709-000000@email.amazonses.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <0100019d1d476420-6b0bf60e-3b3a-4868-8f5f-484cd55d4709-000000@email.amazonses.com> X-ClientProxiedBy: MW4PR04CA0044.namprd04.prod.outlook.com (2603:10b6:303:6a::19) To PH3PPF9E162731D.namprd11.prod.outlook.com (2603:10b6:518:1::d3c) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH3PPF9E162731D:EE_|IA4PR11MB8961:EE_ X-MS-Office365-Filtering-Correlation-Id: 07873dea-cda2-4841-18fd-08de8a293efc X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014|56012099003|22082099003|18002099003; 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Fsdev uses fsdev_clear_folio_state() to switch the > folios into a fsdax-compatible state. > > A side effect of this is that raw mmap doesn't (can't?) work on an fsdev > dax instance. Accordingly, The fsdev driver does not provide raw mmap - > devices must be put in 'devdax' mode (drivers/dax/device.c) to get raw > mmap capability. > > In this commit is just the framework, which remaps pages/folios compatibly > with fsdax. > > Enabling dax changes: > > - bus.h: add DAXDRV_FSDEV_TYPE driver type > - bus.c: allow DAXDRV_FSDEV_TYPE drivers to bind to daxdevs > - dax.h: prototype inode_dax(), which fsdev needs > > Suggested-by: Dan Williams > Suggested-by: Gregory Price > Signed-off-by: John Groves > --- [snip] > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index e4bd5c9f006c..562e2b06f61a 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -81,6 +81,10 @@ static int dax_match_type(const struct dax_device_driver *dax_drv, struct device > !IS_ENABLED(CONFIG_DEV_DAX_KMEM)) > return 1; > > + /* fsdev driver can also bind to device-type dax devices */ > + if (dax_drv->type == DAXDRV_FSDEV_TYPE && type == DAXDRV_DEVICE_TYPE) > + return 1; > + In building up a topic branch for this I notice that this breaks the device-dax test. 1/1 ndctl:dax / device-dax FAIL 0.19s (exit status 250 or signal 122 SIGinvalid) ... Ok: 0 Expected Fail: 0 Fail: 1 Unexpected Pass: 0 Skipped: 0 Timeout: 0 Have you run this series with all the ndctl cxl selftests? How exactly is this supposed to ensure the fsdev driver does not bind to a regular dax device? This can be fixed by reloading the fsdev module thus pushing that driver later in the driver list... So we need to come up with a more reliable method here. I'm holding off pushing a topic branch for the time being. Ira > return 0; > } > [snip]