scsi: kill off the legacy IO path

This removes the legacy (non-mq) IO path for SCSI.

Cc: linux-scsi@vger.kernel.org
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

Documentation/scsi/scsi-parameters.txt

@@ -97,11 +97,6 @@ parameters may be changed at runtime by the command
 			allowing boot to proceed.  none ignores them, expecting
 			user space to do the scan.
 
-	scsi_mod.use_blk_mq=
-			[SCSI] use blk-mq I/O path by default
-			See SCSI_MQ_DEFAULT in drivers/scsi/Kconfig.
-			Format: <y/n>
-
 	sim710=		[SCSI,HW]
 			See header of drivers/scsi/sim710.c.
 

drivers/scsi/Kconfig

@@ -50,18 +50,6 @@ config SCSI_NETLINK
 	default	n
 	depends on NET
 
-config SCSI_MQ_DEFAULT
-	bool "SCSI: use blk-mq I/O path by default"
-	default y
-	depends on SCSI
-	---help---
-	  This option enables the blk-mq based I/O path for SCSI devices by
-	  default.  With this option the scsi_mod.use_blk_mq module/boot
-	  option defaults to Y, without it to N, but it can still be
-	  overridden either way.
-
-	  If unsure say Y.
-
 config SCSI_PROC_FS
 	bool "legacy /proc/scsi/ support"
 	depends on SCSI && PROC_FS

drivers/scsi/cxlflash/main.c

@@ -3088,12 +3088,6 @@ static ssize_t hwq_mode_store(struct device *dev,
 		return -EINVAL;
 	}
 
-	if ((mode == HWQ_MODE_TAG) && !shost_use_blk_mq(shost)) {
-		dev_info(cfgdev, "SCSI-MQ is not enabled, use a different "
-			 "HWQ steering mode.\n");
-		return -EINVAL;
-	}
-
 	afu->hwq_mode = mode;
 
 	return count;

drivers/scsi/hosts.c

@@ -222,18 +222,9 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	if (error)
 		goto fail;
 
-	if (shost_use_blk_mq(shost)) {
-		error = scsi_mq_setup_tags(shost);
-		if (error)
-			goto fail;
-	} else {
-		shost->bqt = blk_init_tags(shost->can_queue,
-				shost->hostt->tag_alloc_policy);
-		if (!shost->bqt) {
-			error = -ENOMEM;
-			goto fail;
-		}
-	}
+	error = scsi_mq_setup_tags(shost);
+	if (error)
+		goto fail;
 
 	if (!shost->shost_gendev.parent)
 		shost->shost_gendev.parent = dev ? dev : &platform_bus;
@@ -309,8 +300,7 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	pm_runtime_disable(&shost->shost_gendev);
 	pm_runtime_set_suspended(&shost->shost_gendev);
 	pm_runtime_put_noidle(&shost->shost_gendev);
-	if (shost_use_blk_mq(shost))
-		scsi_mq_destroy_tags(shost);
+	scsi_mq_destroy_tags(shost);
  fail:
 	return error;
 }
@@ -344,13 +334,8 @@ static void scsi_host_dev_release(struct device *dev)
 		kfree(dev_name(&shost->shost_dev));
 	}
 
-	if (shost_use_blk_mq(shost)) {
-		if (shost->tag_set.tags)
-			scsi_mq_destroy_tags(shost);
-	} else {
-		if (shost->bqt)
-			blk_free_tags(shost->bqt);
-	}
+	if (shost->tag_set.tags)
+		scsi_mq_destroy_tags(shost);
 
 	kfree(shost->shost_data);
 
@@ -472,8 +457,6 @@ 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->force_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/lpfc/lpfc_scsi.c

@@ -3914,7 +3914,7 @@ int lpfc_sli4_scmd_to_wqidx_distr(struct lpfc_hba *phba,
 	uint32_t tag;
 	uint16_t hwq;
 
-	if (cmnd && shost_use_blk_mq(cmnd->device->host)) {
+	if (cmnd) {
 		tag = blk_mq_unique_tag(cmnd->request);
 		hwq = blk_mq_unique_tag_to_hwq(tag);
 

drivers/scsi/qedi/qedi_main.c

@@ -644,8 +644,7 @@ static struct qedi_ctx *qedi_host_alloc(struct pci_dev *pdev)
 	qedi->max_active_conns = ISCSI_MAX_SESS_PER_HBA;
 	qedi->max_sqes = QEDI_SQ_SIZE;
 
-	if (shost_use_blk_mq(shost))
-		shost->nr_hw_queues = MIN_NUM_CPUS_MSIX(qedi);
+	shost->nr_hw_queues = MIN_NUM_CPUS_MSIX(qedi);
 
 	pci_set_drvdata(pdev, qedi);
 

drivers/scsi/qla2xxx/qla_os.c

@@ -857,13 +857,9 @@ qla2xxx_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 	}
 
 	if (ha->mqenable) {
-		if (shost_use_blk_mq(vha->host)) {
-			tag = blk_mq_unique_tag(cmd->request);
-			hwq = blk_mq_unique_tag_to_hwq(tag);
-			qpair = ha->queue_pair_map[hwq];
-		} else if (vha->vp_idx && vha->qpair) {
-			qpair = vha->qpair;
-		}
+		tag = blk_mq_unique_tag(cmd->request);
+		hwq = blk_mq_unique_tag_to_hwq(tag);
+		qpair = ha->queue_pair_map[hwq];
 
 		if (qpair)
 			return qla2xxx_mqueuecommand(host, cmd, qpair);
@@ -3153,7 +3149,7 @@ qla2x00_probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
 		goto probe_failed;
 	}
 
-	if (ha->mqenable && shost_use_blk_mq(host)) {
+	if (ha->mqenable) {
 		/* number of hardware queues supported by blk/scsi-mq*/
 		host->nr_hw_queues = ha->max_qpairs;
 
@@ -3265,25 +3261,17 @@ qla2x00_probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
 	    base_vha->mgmt_svr_loop_id, host->sg_tablesize);
 
 	if (ha->mqenable) {
-		bool mq = false;
 		bool startit = false;
 
-		if (QLA_TGT_MODE_ENABLED()) {
-			mq = true;
+		if (QLA_TGT_MODE_ENABLED())
 			startit = false;
-		}
 
-		if ((ql2x_ini_mode == QLA2XXX_INI_MODE_ENABLED) &&
-		    shost_use_blk_mq(host)) {
-			mq = true;
+		if (ql2x_ini_mode == QLA2XXX_INI_MODE_ENABLED)
 			startit = true;
-		}
 
-		if (mq) {
-			/* Create start of day qpairs for Block MQ */
-			for (i = 0; i < ha->max_qpairs; i++)
-				qla2xxx_create_qpair(base_vha, 5, 0, startit);
-		}
+		/* Create start of day qpairs for Block MQ */
+		for (i = 0; i < ha->max_qpairs; i++)
+			qla2xxx_create_qpair(base_vha, 5, 0, startit);
 	}
 
 	if (ha->flags.running_gold_fw)

drivers/scsi/scsi.c

@@ -780,11 +780,8 @@ MODULE_LICENSE("GPL");
 module_param(scsi_logging_level, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(scsi_logging_level, "a bit mask of logging levels");
 
-#ifdef CONFIG_SCSI_MQ_DEFAULT
+/* This should go away in the future, it doesn't do anything anymore */
 bool scsi_use_blk_mq = true;
-#else
-bool scsi_use_blk_mq = false;
-#endif
 module_param_named(use_blk_mq, scsi_use_blk_mq, bool, S_IWUSR | S_IRUGO);
 
 static int __init init_scsi(void)

drivers/scsi/scsi_debug.c

@@ -5881,8 +5881,7 @@ static int sdebug_driver_probe(struct device *dev)
 	}
 	/* Decide whether to tell scsi subsystem that we want mq */
 	/* Following should give the same answer for each host */
-	if (shost_use_blk_mq(hpnt))
-		hpnt->nr_hw_queues = submit_queues;
+	hpnt->nr_hw_queues = submit_queues;
 
 	sdbg_host->shost = hpnt;
 	*((struct sdebug_host_info **)hpnt->hostdata) = sdbg_host;

drivers/scsi/scsi_error.c

@@ -308,7 +308,7 @@ enum blk_eh_timer_return scsi_times_out(struct request *req)
 		 * error handler. In that case we can return immediately as no
 		 * further action is required.
 		 */
-		if (req->q->mq_ops && !blk_mq_mark_complete(req))
+		if (!blk_mq_mark_complete(req))
 			return rtn;
 		if (scsi_abort_command(scmd) != SUCCESS) {
 			set_host_byte(scmd, DID_TIME_OUT);