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 <[email protected]> Reviewed-by: Sagi Grimberg <[email protected]> Reviewed-by: Martin K. Petersen <[email protected]> Signed-off-by: Christoph Hellwig <[email protected]>
tadfisher · Nov 12, 2014 · efec4b9 · efec4b9
1 parent 205fb5f
commit efec4b9
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diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
@@ -2106,7 +2106,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 
 	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
@@ -638,6 +638,14 @@ struct Scsi_Host {
 	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.