[PATCH v2] dm writecache: reject asynchronous pmem.

[Michal Suchanek <msuchanek@suse.de>]

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

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 30505d70f423..1e4f37249e28 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -2271,6 +2271,12 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv)
 			ti->error = "Unable to map persistent memory for cache";
 			goto bad;
 		}
+
+		if (!dax_synchronous(wc->ssd_dev->dax_dev)) {
+			r = -EOPNOTSUPP;
+			ti->error = "Asynchronous persistent memory not supported as pmem cache";
+			goto bad;
+		}
 	} else {
 		size_t n_blocks, n_metadata_blocks;
 		uint64_t n_bitmap_bits;
-- 
2.26.2
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