[RFC PATCH v3 1/4] dm: Treat alloc_dax failure as non-fatal

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

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() failure as non-fatal.

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: dm-devel@lists.linux.dev
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-arch@vger.kernel.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: nvdimm@lists.linux.dev
Cc: linux-cxl@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
---
 drivers/md/dm.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 23c32cd1f1d8..f90743a94da9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2126,12 +2126,12 @@ static struct mapped_device *alloc_dev(int minor)
 		md->dax_dev = alloc_dax(md, &dm_dax_ops);
 		if (IS_ERR(md->dax_dev)) {
 			md->dax_dev = NULL;
-			goto bad;
+		} else {
+			set_dax_nocache(md->dax_dev);
+			set_dax_nomc(md->dax_dev);
+			if (dax_add_host(md->dax_dev, md->disk))
+				goto bad;
 		}
-		set_dax_nocache(md->dax_dev);
-		set_dax_nomc(md->dax_dev);
-		if (dax_add_host(md->dax_dev, md->disk))
-			goto bad;
 	}
 
 	format_dev_t(md->name, MKDEV(_major, minor));
-- 
2.39.2