diff mbox series

[V3,08/14] scsi: megaraid: take blk_mq_max_nr_hw_queues() into account for calculating io vectors

Message ID 20230808104239.146085-9-ming.lei@redhat.com (mailing list archive)
State New, archived
Headers show
Series blk-mq: fix wrong queue mapping for kdump kernel | expand

Commit Message

Ming Lei Aug. 8, 2023, 10:42 a.m. UTC
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 kernel command line,
see `Documentation/admin-guide/kdump/kdump.rst`, so num_possible_cpus()
still returns all CPUs because 'maxcpus=1' just bring up one single
cpu core during booting.

blk-mq sees single queue in kdump kernel, and in driver's viewpoint
there are still multiple queues, this inconsistency causes driver to apply
wrong queue mapping for handling IO, and IO timeout is triggered.

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

Cc: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Cc: Sathya Prakash Veerichetty <sathya.prakash@broadcom.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/megaraid/megaraid_sas_base.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
index 050eed8e2684..587ccbc1ec92 100644
--- a/drivers/scsi/megaraid/megaraid_sas_base.c
+++ b/drivers/scsi/megaraid/megaraid_sas_base.c
@@ -5921,6 +5921,10 @@  __megasas_alloc_irq_vectors(struct megasas_instance *instance)
 	int i, irq_flags;
 	struct irq_affinity desc = { .pre_vectors = instance->low_latency_index_start };
 	struct irq_affinity *descp = &desc;
+	unsigned max_vecs = instance->msix_vectors - instance->iopoll_q_count;
+
+	if (max_vecs > scsi_max_nr_hw_queues())
+		max_vecs = scsi_max_nr_hw_queues();
 
 	irq_flags = PCI_IRQ_MSIX;
 
@@ -5934,7 +5938,7 @@  __megasas_alloc_irq_vectors(struct megasas_instance *instance)
 	 */
 	i = pci_alloc_irq_vectors_affinity(instance->pdev,
 		instance->low_latency_index_start,
-		instance->msix_vectors - instance->iopoll_q_count, irq_flags, descp);
+		max_vecs, irq_flags, descp);
 
 	return i;
 }