[PATCH] dm writecache: reject asynchronous pmem.

[Michal Suchanek]

The writecache driver 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>
---
 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..57b0a972f6fd 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -2277,6 +2277,12 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv)
 
 		wc->memory_map_size -= (uint64_t)wc->start_sector << SECTOR_SHIFT;
 
+		if (!dax_synchronous(wc->ssd_dev->dax_dev)) {
+			r = -EOPNOTSUPP;
+			ti->error = "Asynchronous persistent memory not supported as pmem cache";
+			goto bad;
+		}
+
 		bio_list_init(&wc->flush_list);
 		wc->flush_thread = kthread_create(writecache_flush_thread, wc, "dm_writecache_flush");
 		if (IS_ERR(wc->flush_thread)) {
-- 
2.26.2