Received-SPF: pass (google.com: domain of linux-kernel+bounces-58726-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Date: Thu, 8 Feb 2024 13:34:34 -0800
From: Dan Williams <dan.j.williams@intel.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, Dan Williams
	<dan.j.williams@intel.com>, Arnd Bergmann <arnd@arndb.de>, Dave Chinner
	<david@fromorbit.com>
CC: <linux-kernel@vger.kernel.org>, Mathieu Desnoyers
	<mathieu.desnoyers@efficios.com>, Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>, Vishal Verma
	<vishal.l.verma@intel.com>, Dave Jiang <dave.jiang@intel.com>, Matthew Wilcox
	<willy@infradead.org>, Russell King <linux@armlinux.org.uk>,
	<linux-arch@vger.kernel.org>, <linux-cxl@vger.kernel.org>,
	<linux-fsdevel@vger.kernel.org>, <linux-mm@kvack.org>,
	<linux-xfs@vger.kernel.org>, <dm-devel@lists.linux.dev>,
	<nvdimm@lists.linux.dev>, <linux-s390@vger.kernel.org>, Alasdair Kergon
	<agk@redhat.com>, Mike Snitzer <snitzer@kernel.org>, Mikulas Patocka
	<mpatocka@redhat.com>
Subject: RE: [PATCH v4 03/12] dm: Treat alloc_dax() -EOPNOTSUPP failure as
 non-fatal
Message-ID: <65c548ea54127_afa429463@dwillia2-xfh.jf.intel.com.notmuch>
References: <20240208184913.484340-1-mathieu.desnoyers@efficios.com>
 <20240208184913.484340-4-mathieu.desnoyers@efficios.com>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20240208184913.484340-4-mathieu.desnoyers@efficios.com>
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?/IGLDEBbUqiRFg5sojodJg6kcpIWtN+jc+Jbbn44hd7DbsLBNqgvPs672zDJ?=
 =?us-ascii?Q?LpauYE6hOltKRlpGgkQLVbK9dZXGvjbB5ACx2GAJ4uiBQMX/CvTt4aXfrzST?=
 =?us-ascii?Q?MWlf9FDLxnj6b7PiiZeUf3qYcR8u0sBezVDqfNVuldkoVcvN7uCl5UBk4N7b?=
 =?us-ascii?Q?2M/754zBaX/2YPQNQxxPo6z0mXS3ij9FZUjxuoZubj7xzmQjPJQiD6ZgHGRC?=
 =?us-ascii?Q?569Tq8hNKN03//ATOU0WCeXKnQ3hY+bpm4QzK5tUEECoUocH0LdcftjQ/rkw?=
 =?us-ascii?Q?6nUU/ohVjVtTwTTRSGyshEs1bJQd87KiTJQNWhKNHCadUUu9WcJj89Kf5N6R?=
 =?us-ascii?Q?kdeDsKW8poh9HIiYuW1BPkegIyxUsJHM8ZLyRkO3DQrdjfLX1s1v6M8T3B2f?=
 =?us-ascii?Q?Khamgzsb23Wf6U7TjthF/5UG/0lxXwYsoXv/FdYiFcG2jdCGbXXNJA4cxfmB?=
 =?us-ascii?Q?RaeAC475xi0sLomc62OM3H4B7BrFk2EAi4H4J48zT8ueKDPwC+tCo4aoja/Z?=
 =?us-ascii?Q?tkpld/Bf6jX3+4+3emsKgsAkTXcSarcOpKy+IV1bgPwZlLHh1nj5iYrZ2yKQ?=
 =?us-ascii?Q?1hSv06JUfu4J+fKMaCVMj2Y+HoNcR52klgLWtVudRa9Dd0dBMaKwxDd4Ej2U?=
 =?us-ascii?Q?amrle7clPgxY8QlcIUqoT8k7zxELEky+WTSXul4ZJ3yac8pKFBEOy2eJtBUd?=
 =?us-ascii?Q?Qj8B2qw4fE86D+CbZP80UoOpIpVJo2vFW4FVucKcSCMU3831fPhVfC00JElC?=
 =?us-ascii?Q?asTzm47HCHHlkW3czZuDAaoKySeng07QOxQW7cDCVwuWQwY9H0vgHCd3N3ZG?=
 =?us-ascii?Q?mhkcl+BKdfowP65g3Ek8Kgj0QeTOKtfhPRtrHGtoj/Q99CUQits1awsZZVsp?=
 =?us-ascii?Q?IRZ9bDWy4qVxE4rvb7Lwc3gcDSNIvKmtsTl/gRqxUfOGGjuQSapa7BDh+wNU?=
 =?us-ascii?Q?NemKbWUStXjgFZpUxCi8H47fATYzvG1cothVMTvh+xO9KuTT9VR/VFw9rNZT?=
 =?us-ascii?Q?WOVI3z/59+3qH4sKYb8TzNHxEqGF2wgLeXwyfYfkfIjNbM3OwK43DH0YSaB5?=
 =?us-ascii?Q?V/qoXZj9TWP/dO/ihwsdqidredFh8n2Le8sSt6/xBzhUhl9CWdMQ8BMoqP8i?=
 =?us-ascii?Q?70abZkCE0wA1oBUVo0aLbEIujDqkIzM7RFhmEFtSkUdcmDug+BF/mnx3zdgz?=
 =?us-ascii?Q?6jZLju1UnKJJbCzjS3esfBKJQewFJcoQvVXLJh9alEyei5LusV8fpO2HFoUs?=
 =?us-ascii?Q?iSHCWtdH6lzlxxsSw+QUEZ+4RTDzGeWaBHeAAcBxF7WpaVCuhV4RCHTmBRdz?=
 =?us-ascii?Q?fpbnGizGGOlR8OCUz0rdxJbBXkBNf2OVnwPdO8SKhMsj1iwgy6sd2TRFV1wU?=
 =?us-ascii?Q?qo/Bf2Xawd2rL+XqV79C8vnPAxC5yBZiIXTlBhizJBUT3DRIPi8Av/u69zOa?=
 =?us-ascii?Q?J5xav9GBbWsGmqs7Ub8Hj/2OQVULsu7lTvglUoGViNj7HYqsADyahgAMXgBC?=
 =?us-ascii?Q?kBS2DjGyaZ8ddvB/u/lMjbK3nUmVeVBm+WeUcKnC1LlNcZmXnU1WiLLII+KY?=
 =?us-ascii?Q?JQPLSJ5hPTTGvXeRkqJu8h+8E/2zdcjE0p7JZq33+D2lqLLNS0IZePhkfAJZ?=
 =?us-ascii?Q?aA=3D=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: d6d273cd-7dbd-4d16-ad30-08dc28edc00d
X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Feb 2024 21:34:37.5198
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: wYXHX08hjFVII3EKOEySlTQXyLvfCnphNr5FXwUu9M2TiyyoEasLMWqJ+Sui9nYEYR9+NhSjOw/EHf9sYz0eQkRhtTpnzZ+hUoAdqD+/Pic=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR11MB7271
X-OriginatorOrg: intel.com

Mathieu Desnoyers wrote:
> In preparation for checking whether the architecture has data cache
> aliasing within alloc_dax(), modify the error handling of dm alloc_dev()
> to treat alloc_dax() -EOPNOTSUPP failure as non-fatal.
> 
> For the transition, consider that alloc_dax() returning NULL is the
> same as returning -EOPNOTSUPP.
> 
> Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Alasdair Kergon <agk@redhat.com>
> Cc: Mike Snitzer <snitzer@kernel.org>
> Cc: Mikulas Patocka <mpatocka@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: linux-arch@vger.kernel.org
> Cc: linux-cxl@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-xfs@vger.kernel.org
> Cc: dm-devel@lists.linux.dev
> Cc: nvdimm@lists.linux.dev
> ---
>  drivers/md/dm.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 23c32cd1f1d8..2fc22cae9089 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -2054,6 +2054,7 @@ static void cleanup_mapped_device(struct mapped_device *md)
>  static struct mapped_device *alloc_dev(int minor)
>  {
>  	int r, numa_node_id = dm_get_numa_node();
> +	struct dax_device *dax_dev;
>  	struct mapped_device *md;
>  	void *old_md;
>  
> @@ -2122,15 +2123,15 @@ static struct mapped_device *alloc_dev(int minor)
>  	md->disk->private_data = md;
>  	sprintf(md->disk->disk_name, "dm-%d", minor);
>  
> -	if (IS_ENABLED(CONFIG_FS_DAX)) {
> -		md->dax_dev = alloc_dax(md, &dm_dax_ops);
> -		if (IS_ERR(md->dax_dev)) {
> -			md->dax_dev = NULL;
> +	dax_dev = alloc_dax(md, &dm_dax_ops);
> +	if (IS_ERR_OR_NULL(dax_dev)) {

Similar feedback as the pmem change, lets not propagate the mistake that
alloc_dax() could return NULL, none of the callers of alloc_dax()
properly handled NULL and it was just luck that none of the use cases
tried to use alloc_dax() in the CONFIG_DAX=n case.