scsi: allow LLDDs to expose the queue mapping to blk-mq

Just hand through the blk-mq map_queues method in the host template.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -1990,6 +1990,15 @@ static void scsi_exit_request(void *data, struct request *rq,
 	kfree(cmd->sense_buffer);
 }
 
+static int scsi_map_queues(struct blk_mq_tag_set *set)
+{
+	struct Scsi_Host *shost = container_of(set, struct Scsi_Host, tag_set);
+
+	if (shost->hostt->map_queues)
+		return shost->hostt->map_queues(shost);
+	return blk_mq_map_queues(set);
+}
+
 static u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
 {
 	struct device *host_dev;
@@ -2082,6 +2091,7 @@ static struct blk_mq_ops scsi_mq_ops = {
 	.timeout	= scsi_timeout,
 	.init_request	= scsi_init_request,
 	.exit_request	= scsi_exit_request,
+	.map_queues	= scsi_map_queues,
 };
 
 struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)

include/scsi/scsi_host.h

@@ -277,6 +277,14 @@ struct scsi_host_template {
 	 */
 	int (* change_queue_depth)(struct scsi_device *, int);
 
+	/*
+	 * This functions lets the driver expose the queue mapping
+	 * to the block layer.
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (* map_queues)(struct Scsi_Host *shost);
+
 	/*
 	 * This function determines the BIOS parameters for a given
 	 * harddisk.  These tend to be numbers that are made up by