[PATCH 16/16] nvme-multipath: enable polled I/O

[Christoph Hellwig]

Set the poll queue flag to enable polling, given that the multipath
node just dispatches the bios to a lower queue.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich at intel.com>
---
 drivers/nvme/host/multipath.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index f77b774699de..48ea649d6c24 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -450,6 +450,15 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
 
 	blk_queue_flag_set(QUEUE_FLAG_NONROT, head->disk->queue);
 	blk_queue_flag_set(QUEUE_FLAG_NOWAIT, head->disk->queue);
+	/*
+	 * This assumes all controllers that refer to a namespace either
+	 * support poll queues or not.  That is not a strict guarantee,
+	 * but if the assumption is wrong the effect is only suboptimal
+	 * performance but not correctness problem.
+	 */
+	if (ctrl->tagset->nr_maps > HCTX_TYPE_POLL &&
+	    ctrl->tagset->map[HCTX_TYPE_POLL].nr_queues)
+		blk_queue_flag_set(QUEUE_FLAG_POLL, head->disk->queue);
 
 	/* set to a default value of 512 until the disk is validated */
 	blk_queue_logical_block_size(head->disk->queue, 512);
-- 
2.30.2