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.

Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing 
caches")
Suggested-by: Dan Williams <[email protected]>
Signed-off-by: Mathieu Desnoyers <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Cc: Alasdair Kergon <[email protected]>
Cc: Mike Snitzer <[email protected]>
Cc: Mikulas Patocka <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Vishal Verma <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Russell King <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
 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..acdc00bc05be 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(dax_dev)) {
+               if (PTR_ERR(dax_dev) != -EOPNOTSUPP)
                        goto bad;
-               }
-               set_dax_nocache(md->dax_dev);
-               set_dax_nomc(md->dax_dev);
-               if (dax_add_host(md->dax_dev, md->disk))
+       } else {
+               set_dax_nocache(dax_dev);
+               set_dax_nomc(dax_dev);
+               md->dax_dev = dax_dev;
+               if (dax_add_host(dax_dev, md->disk))
                        goto bad;
        }
 
-- 
2.39.2


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