nvme-pci: only allow polling with separate poll queues

This will allow us to simplify both the regular NVMe interrupt handler
and the upcoming aio poll code.  In addition to that the separate
queues are generally a good idea for performance reasons.
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/pci.c

@@ -1089,13 +1089,6 @@ static int __nvme_poll(struct nvme_queue *nvmeq, unsigned int tag)
 }
 
 static int nvme_poll(struct blk_mq_hw_ctx *hctx)
-{
-	struct nvme_queue *nvmeq = hctx->driver_data;
-
-	return __nvme_poll(nvmeq, -1);
-}
-
-static int nvme_poll_noirq(struct blk_mq_hw_ctx *hctx)
 {
 	struct nvme_queue *nvmeq = hctx->driver_data;
 	u16 start, end;
@@ -1605,12 +1598,11 @@ static const struct blk_mq_ops nvme_mq_admin_ops = {
 
 static const struct blk_mq_ops nvme_mq_ops = {
 	NVME_SHARED_MQ_OPS,
-	.poll			= nvme_poll,
 };
 
-static const struct blk_mq_ops nvme_mq_poll_noirq_ops = {
+static const struct blk_mq_ops nvme_mq_poll_ops = {
 	NVME_SHARED_MQ_OPS,
-	.poll			= nvme_poll_noirq,
+	.poll			= nvme_poll,
 };
 
 static void nvme_dev_remove_admin(struct nvme_dev *dev)
@@ -2298,10 +2290,10 @@ static int nvme_dev_add(struct nvme_dev *dev)
 	int ret;
 
 	if (!dev->ctrl.tagset) {
-		if (!dev->io_queues[HCTX_TYPE_POLL])
-			dev->tagset.ops = &nvme_mq_ops;
+		if (dev->io_queues[HCTX_TYPE_POLL])
+			dev->tagset.ops = &nvme_mq_poll_ops;
 		else
-			dev->tagset.ops = &nvme_mq_poll_noirq_ops;
+			dev->tagset.ops = &nvme_mq_ops;
 
 		dev->tagset.nr_hw_queues = dev->online_queues - 1;
 		dev->tagset.nr_maps = HCTX_MAX_TYPES;