scsi: add support for multiple hardware queues
Allow a SCSI LLD to declare how many hardware queues it supports
by setting Scsi_Host.nr_hw_queues before calling scsi_add_host().
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index fc0a8a0..38f8c85 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2106,7 +2106,7 @@
memset(&shost->tag_set, 0, sizeof(shost->tag_set));
shost->tag_set.ops = &scsi_mq_ops;
- shost->tag_set.nr_hw_queues = 1;
+ shost->tag_set.nr_hw_queues = shost->nr_hw_queues ? : 1;
shost->tag_set.queue_depth = shost->can_queue;
shost->tag_set.cmd_size = cmd_size;
shost->tag_set.numa_node = NUMA_NO_NODE;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 5e36248..bb9e278 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -638,6 +638,14 @@
short unsigned int sg_prot_tablesize;
unsigned int max_sectors;
unsigned long dma_boundary;
+ /*
+ * In scsi-mq mode, the number of hardware queues supported by the LLD.
+ *
+ * Note: it is assumed that each hardware queue has a queue depth of
+ * can_queue. In other words, the total queue depth per host
+ * is nr_hw_queues * can_queue.
+ */
+ unsigned nr_hw_queues;
/*
* Used to assign serial numbers to the cmds.
* Protected by the host lock.
