dm writecache: reject asynchronous pmem devices

DM writecache does not handle asynchronous pmem. Reject it when
supplied as cache.

Link: https://lore.kernel.org/linux-nvdimm/87lfk5hahc.fsf@linux.ibm.com/
Fixes: 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org # 5.3+
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 30505d7..5358894 100644 (file)
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -2266,6 +2266,12 @@ invalid_optional:
        }
 
        if (WC_MODE_PMEM(wc)) {
+               if (!dax_synchronous(wc->ssd_dev->dax_dev)) {
+                       r = -EOPNOTSUPP;
+                       ti->error = "Asynchronous persistent memory not supported as pmem cache";
+                       goto bad;
+               }
+
                r = persistent_memory_claim(wc);
                if (r) {
                        ti->error = "Unable to map persistent memory for cache";