In preparation for checking whether the architecture has data cache
aliasing within alloc_dax(), modify the error handling of nvdimm/pmem
pmem_attach_disk() to treat alloc_dax() -EOPNOTSUPP failure as non-fatal.

[ Based on commit "nvdimm/pmem: Fix leak on dax_add_host() failure". ]

Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing 
caches")
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/nvdimm/pmem.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 9fe358090720..e9898457a7bd 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -560,17 +560,19 @@ static int pmem_attach_disk(struct device *dev,
        dax_dev = alloc_dax(pmem, &pmem_dax_ops);
        if (IS_ERR(dax_dev)) {
                rc = PTR_ERR(dax_dev);
-               goto out;
+               if (rc != -EOPNOTSUPP)
+                       goto out;
+       } else {
+               set_dax_nocache(dax_dev);
+               set_dax_nomc(dax_dev);
+               if (is_nvdimm_sync(nd_region))
+                       set_dax_synchronous(dax_dev);
+               pmem->dax_dev = dax_dev;
+               rc = dax_add_host(dax_dev, disk);
+               if (rc)
+                       goto out_cleanup_dax;
+               dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
        }
-       set_dax_nocache(dax_dev);
-       set_dax_nomc(dax_dev);
-       if (is_nvdimm_sync(nd_region))
-               set_dax_synchronous(dax_dev);
-       pmem->dax_dev = dax_dev;
-       rc = dax_add_host(dax_dev, disk);
-       if (rc)
-               goto out_cleanup_dax;
-       dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
        rc = device_add_disk(dev, disk, pmem_attribute_groups);
        if (rc)
                goto out_remove_host;
-- 
2.39.2


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