[PATCH 2/2] nvme-pci: use blk_mq_max_nr_hw_queues() to calculate io queues

[Ming Lei]

Take blk-mq's knowledge into account for calculating io queues.

Fix wrong queue mapping in case of kdump kernel.

On arm and ppc64, 'maxcpus=1' is passed to kdump command line, see
`Documentation/admin-guide/kdump/kdump.rst`, so num_possible_cpus()
still returns all CPUs.

But blk-mq can only support single queue for kdump kernel, this way
causes wrong queue mapping taken for handling IO, and IO timeout
is triggered.

Meantime, single queue makes much less resource utilization, and reduce
risk of kernel failure.

Reported-by: Wen Xiong <wenxiong at linux.ibm.com>
Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 drivers/nvme/host/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 72725729cb6c..cb13ba203956 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2247,7 +2247,7 @@ static unsigned int nvme_max_io_queues(struct nvme_dev *dev)
 	 */
 	if (dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS)
 		return 1;
-	return num_possible_cpus() + dev->nr_write_queues + dev->nr_poll_queues;
+	return blk_mq_max_nr_hw_queues() + dev->nr_write_queues + dev->nr_poll_queues;
 }
 
 static int nvme_setup_io_queues(struct nvme_dev *dev)
-- 
2.40.1