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Thu, 12 Mar 2026 00:27:42 +0000 From: Dan Williams Date: Wed, 11 Mar 2026 17:27:40 -0700 To: Smita Koralahalli , , , , , CC: Ard Biesheuvel , Alison Schofield , Vishal Verma , "Ira Weiny" , Dan Williams , Jonathan Cameron , Yazen Ghannam , Dave Jiang , Davidlohr Bueso , Matthew Wilcox , Jan Kara , "Rafael J . Wysocki" , Len Brown , Pavel Machek , Li Ming , Jeff Johnson , "Ying Huang" , Yao Xingtao , Peter Zijlstra , Greg Kroah-Hartman , Nathan Fontenot , Terry Bowman , Robert Richter , Benjamin Cheatham , Zhijian Li , Borislav Petkov , Smita Koralahalli , Tomasz Wolski Message-ID: <69b2087cb0cb7_2132100c2@dwillia2-mobl4.notmuch> In-Reply-To: <20260210064501.157591-6-Smita.KoralahalliChannabasappa@amd.com> References: <20260210064501.157591-1-Smita.KoralahalliChannabasappa@amd.com> <20260210064501.157591-6-Smita.KoralahalliChannabasappa@amd.com> Subject: Re: [PATCH v6 5/9] dax: Track all dax_region allocations under a global resource tree Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR21CA0020.namprd21.prod.outlook.com (2603:10b6:a03:114::30) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR11MB8107:EE_|DS7PR11MB6175:EE_ X-MS-Office365-Filtering-Correlation-Id: 5240b581-8a0e-4209-01e8-08de7fce2c73 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|7416014|366016|7053199007|22082099003|18002099003|56012099003; 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Release the resource on > dax_region teardown. > > By enforcing a single global namespace for dax_region allocations, this > ensures only one of dax_hmem or dax_cxl can successfully register a > dax_region for a given range. > > Co-developed-by: Dan Williams Did I send any code for this? If I suggested the locking below, apologies, otherwise Suggested-by is expected unless code is adopted from another patch. > Signed-off-by: Dan Williams > Signed-off-by: Smita Koralahalli > --- > drivers/dax/bus.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index fde29e0ad68b..5f387feb95f0 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -10,6 +10,7 @@ > #include "dax-private.h" > #include "bus.h" > > +static struct resource dax_regions = DEFINE_RES_MEM_NAMED(0, -1, "DAX Regions"); > static DEFINE_MUTEX(dax_bus_lock); > > /* > @@ -625,6 +626,8 @@ static void dax_region_unregister(void *region) > { > struct dax_region *dax_region = region; > > + scoped_guard(rwsem_write, &dax_region_rwsem) > + release_resource(&dax_region->res); I continue to dislike what scoped_guard() does to indentation. Often scoped_guard() usage can just be replaced by "helper that uses guard()" However, dax_region_rwsem protects subdivision of a dax_region, not coordination across regions. Also, release_resource() and request_resource() are already protected by the resource_lock, why is a new lock needed?