diff --git a/fs/dax.c b/fs/dax.c
index 7ecad1a28a89..8b1c371d6b28 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1247,8 +1247,9 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
 	if (ret < 0)
 		goto out_unlock;
 
-	ret = copy_mc_to_kernel(daddr, saddr, length);
-	if (ret)
+	if (copy_mc_to_kernel(daddr, saddr, length) == 0)
+		ret = length;
+	else
 		ret = -EIO;
 
 out_unlock: