[PATCH 5.7 161/166] dm writecache: reject asynchronous pmem devices

[Greg Kroah-Hartman]

From: Michal Suchanek <msuchanek@xxxxxxx>

commit a46624580376a3a0beb218d94cbc7f258696e29f upstream.

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

Link: https://lore.kernel.org/linux-nvdimm/87lfk5hahc.fsf@xxxxxxxxxxxxx/
Fixes: 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
Acked-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 5.3+
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/dm-writecache.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -2232,6 +2232,12 @@ 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";