+typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
+ struct bio_vec *biovec, int max_size);
+
+/*
+ * Returns:
+ * 0: The target can handle the next I/O immediately.
+ * 1: The target can't handle the next I/O immediately.
+ */
+typedef int (*dm_busy_fn) (struct dm_target *ti);
+