scsi: remove the disable_blk_mq host flag

We've had scsi-mq for 2.5 years now, so we can remove the unused flag to
disable the code on a per-host basis that was put in for unexpected
emergencies during bringup.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hosts.c

@@ -486,8 +486,6 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	else
 		shost->dma_boundary = 0xffffffff;
 
-	shost->use_blk_mq = scsi_use_blk_mq && !shost->hostt->disable_blk_mq;
-
 	device_initialize(&shost->shost_gendev);
 	dev_set_name(&shost->shost_gendev, "host%d", shost->host_no);
 	shost->shost_gendev.bus = &scsi_bus_type;

drivers/scsi/scsi.c

@@ -1160,6 +1160,7 @@ bool scsi_use_blk_mq = true;
 bool scsi_use_blk_mq = false;
 #endif
 module_param_named(use_blk_mq, scsi_use_blk_mq, bool, S_IWUSR | S_IRUGO);
+EXPORT_SYMBOL_GPL(scsi_use_blk_mq);
 
 static int __init init_scsi(void)
 {

include/scsi/scsi_host.h

@@ -495,9 +495,6 @@ struct scsi_host_template {
 	 */
 	unsigned int cmd_size;
 	struct scsi_host_cmd_pool *cmd_pool;
-
-	/* temporary flag to disable blk-mq I/O path */
-	bool disable_blk_mq;
 };
 
 /*
@@ -778,7 +775,8 @@ extern bool scsi_use_blk_mq;
 
 static inline bool shost_use_blk_mq(struct Scsi_Host *shost)
 {
-	return shost->use_blk_mq;
+	return scsi_use_blk_mq;
+
 }
 
 extern int scsi_queue_work(struct Scsi_Host *, struct work_struct *);