On Sat, Jan 25, 2020 at 09:41:37PM -0700, Andrzej Jakowski wrote:

 	if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q))
-		goto not_supported;
+		if (!(bio->bi_opf & REQ_HIPRI))
+			goto not_supported;

Can you explain this check?  This looks weird to me  I think we need
a generalized check if a make_request based driver supports REQ_NOWAIT
instead (and as a separate patch / patchset).

+	if (q->bio_poll_fn != NULL) {
+		state = current->state;
+		do {
+			int ret;
+
+			ret = q->bio_poll_fn(q, cookie);
+			if (ret > 0) {
+				__set_current_state(TASK_RUNNING);
+				return ret;
+			}
+
+			if (signal_pending_state(state, current))
+				__set_current_state(TASK_RUNNING);
+
+			if (current->state == TASK_RUNNING)
+				return 1;
+			if (ret < 0 || !spin)
+				break;
+			cpu_relax();
+		} while (!need_resched());
+
+		__set_current_state(TASK_RUNNING);
+
+		return 0;
+	}

This needs to be factored out into a helper at least.