dm table: allow upgrade from bio-based to specialized bio-based variant

In practice this is really only meaningful in the context of the DM
multipath target (which uses dm_table_set_type() to set the type of
device DM should create via its "queue_mode" option).

So this change allows a DM multipath device with "queue_mode bio" to be
upgraded from DM_TYPE_BIO_BASED to DM_TYPE_NVME_BIO_BASED -- iff the
underlying device(s) are NVMe.

DM_TYPE_NVME_BIO_BASED is just a DM core implementation detail that
allows for NVMe-specific optimizations (e.g. use direct_make_request
instead of generic_make_request).  If in the future there is no benefit
or need to distinguish NVMe vs not: then it will be removed.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

drivers/md/dm-table.c

@@ -942,17 +942,12 @@ static int dm_table_determine_type(struct dm_table *t)
 
 	if (t->type != DM_TYPE_NONE) {
 		/* target already set the table's type */
-		if (t->type == DM_TYPE_BIO_BASED)
-			return 0;
-		else if (t->type == DM_TYPE_NVME_BIO_BASED) {
-			if (!dm_table_does_not_support_partial_completion(t)) {
-				DMERR("nvme bio-based is only possible with devices"
-				      " that don't support partial completion");
-				return -EINVAL;
-			}
-			/* Fallthru, also verify all devices are blk-mq */
+		if (t->type == DM_TYPE_BIO_BASED) {
+			/* possibly upgrade to a variant of bio-based */
+			goto verify_bio_based;
 		}
 		BUG_ON(t->type == DM_TYPE_DAX_BIO_BASED);
+		BUG_ON(t->type == DM_TYPE_NVME_BIO_BASED);
 		goto verify_rq_based;
 	}
 
@@ -985,6 +980,7 @@ static int dm_table_determine_type(struct dm_table *t)
 	}
 
 	if (bio_based) {
+verify_bio_based:
 		/* We must use this table as bio-based */
 		t->type = DM_TYPE_BIO_BASED;
 		if (dm_table_supports_dax(t) ||