From a quick look the code seems reasonably sensible here,
but any chance we could have this in common code?

+static bool nvme_fail_queue_request(struct request *req, void *data, bool reserved)
+{
+	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
+	struct nvme_queue *nvmeq = iod->nvmeq;
+
+	if (!test_bit(NVMEQ_ENABLED, &nvmeq->flags))
+		blk_mq_end_request(req, BLK_STS_IOERR);
+	return true;
+}

The only thing not purely block layer here is the enabled flag.
So if we had a per-hctx enabled flag we could lift this out of nvme,
and hopefully start reusing it in other drivers.