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>

17 files changed, 77 insertions, 680 deletions

diff --git a/Documentation/scsi/scsi-parameters.txt b/Documentation/scsi/scsi-parameters.txt
index 92999d4e0cb8..25a4b4cf04a6 100644
--- a/Documentation/scsi/scsi-parameters.txt
+++ b/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.
 
diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index f07444d30b21..dfdc6940de2f 100644
--- a/drivers/scsi/Kconfig
+++ b/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
diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c
index 6637116529aa..abdc9eac4173 100644
--- a/drivers/scsi/cxlflash/main.c
+++ b/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;
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index ea4b0bb0c1cd..cc71136ba300 100644
--- a/drivers/scsi/hosts.c
+++ b/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;
diff --git a/drivers/scsi/lpfc/lpfc_scsi.c b/drivers/scsi/lpfc/lpfc_scsi.c
index 4fa6703a9ec9..baed2b891efb 100644
--- a/drivers/scsi/lpfc/lpfc_scsi.c
+++ b/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);
 
diff --git a/drivers/scsi/qedi/qedi_main.c b/drivers/scsi/qedi/qedi_main.c
index 105b0e4d7818..311eb22068e1 100644
--- a/drivers/scsi/qedi/qedi_main.c
+++ b/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);
 
diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
index 518f15141170..4ea9f2b4e04f 100644
--- a/drivers/scsi/qla2xxx/qla_os.c
+++ b/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)
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index fc1356d101b0..7675ff0ca2ea 100644
--- a/drivers/scsi/scsi.c
+++ b/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)
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 60bcc6df97a9..4740f1e9dd17 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/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;
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index c736d61b1648..fff128aa9ec2 100644
--- a/drivers/scsi/scsi_error.c
+++ b/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);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8b0345924a92..651be30ba96a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -168,8 +168,6 @@ static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd)
 static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
 {
         struct scsi_device *device = cmd->device;
-        struct request_queue *q = device->request_queue;
-        unsigned long flags;
 
         SCSI_LOG_MLQUEUE(1, scmd_printk(KERN_INFO, cmd,
                 "Inserting command %p into mlqueue\n", cmd));
@@ -190,26 +188,20 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
          * before blk_cleanup_queue() finishes.
          */
         cmd->result = 0;
-        if (q->mq_ops) {
-                /*
-                 * Before a SCSI command is dispatched,
-                 * get_device(&sdev->sdev_gendev) is called and the host,
-                 * target and device busy counters are increased. Since
-                 * requeuing a request causes these actions to be repeated and
-                 * since scsi_device_unbusy() has already been called,
-                 * put_device(&device->sdev_gendev) must still be called. Call
-                 * put_device() after blk_mq_requeue_request() to avoid that
-                 * removal of the SCSI device can start before requeueing has
-                 * happened.
-                 */
-                blk_mq_requeue_request(cmd->request, true);
-                put_device(&device->sdev_gendev);
-                return;
-        }
-        spin_lock_irqsave(q->queue_lock, flags);
-        blk_requeue_request(q, cmd->request);
-        kblockd_schedule_work(&device->requeue_work);
-        spin_unlock_irqrestore(q->queue_lock, flags);
+
+        /*
+         * Before a SCSI command is dispatched,
+         * get_device(&sdev->sdev_gendev) is called and the host,
+         * target and device busy counters are increased. Since
+         * requeuing a request causes these actions to be repeated and
+         * since scsi_device_unbusy() has already been called,
+         * put_device(&device->sdev_gendev) must still be called. Call
+         * put_device() after blk_mq_requeue_request() to avoid that
+         * removal of the SCSI device can start before requeueing has
+         * happened.
+         */
+        blk_mq_requeue_request(cmd->request, true);
+        put_device(&device->sdev_gendev);
 }
 
 /*
@@ -370,10 +362,7 @@ void scsi_device_unbusy(struct scsi_device *sdev)
 
 static void scsi_kick_queue(struct request_queue *q)
 {
-        if (q->mq_ops)
-                blk_mq_run_hw_queues(q, false);
-        else
-                blk_run_queue(q);
+        blk_mq_run_hw_queues(q, false);
 }
 
 /*
@@ -534,10 +523,7 @@ static void scsi_run_queue(struct request_queue *q)
         if (!list_empty(&sdev->host->starved_list))
                 scsi_starved_list_run(sdev->host);
 
-        if (q->mq_ops)
-                blk_mq_run_hw_queues(q, false);
-        else
-                blk_run_queue(q);
+        blk_mq_run_hw_queues(q, false);
 }
 
 void scsi_requeue_run_queue(struct work_struct *work)
@@ -550,42 +536,6 @@ void scsi_requeue_run_queue(struct work_struct *work)
         scsi_run_queue(q);
 }
 
-/*
- * Function:    scsi_requeue_command()
- *
- * Purpose:     Handle post-processing of completed commands.
- *
- * Arguments:   q       - queue to operate on
- *              cmd     - command that may need to be requeued.
- *
- * Returns:     Nothing
- *
- * Notes:       After command completion, there may be blocks left
- *              over which weren't finished by the previous command
- *              this can be for a number of reasons - the main one is
- *              I/O errors in the middle of the request, in which case
- *              we need to request the blocks that come after the bad
- *              sector.
- * Notes:       Upon return, cmd is a stale pointer.
- */
-static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
-{
-        struct scsi_device *sdev = cmd->device;
-        struct request *req = cmd->request;
-        unsigned long flags;
-
-        spin_lock_irqsave(q->queue_lock, flags);
-        blk_unprep_request(req);
-        req->special = NULL;
-        scsi_put_command(cmd);
-        blk_requeue_request(q, req);
-        spin_unlock_irqrestore(q->queue_lock, flags);
-
-        scsi_run_queue(q);
-
-        put_device(&sdev->sdev_gendev);
-}
-
 void scsi_run_host_queues(struct Scsi_Host *shost)
 {
         struct scsi_device *sdev;
@@ -626,42 +576,6 @@ static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
         scsi_del_cmd_from_list(cmd);
 }
 
-/*
- * Function:    scsi_release_buffers()
- *
- * Purpose:     Free resources allocate for a scsi_command.
- *
- * Arguments:   cmd     - command that we are bailing.
- *
- * Lock status: Assumed that no lock is held upon entry.
- *
- * Returns:     Nothing
- *
- * Notes:       In the event that an upper level driver rejects a
- *              command, we must release resources allocated during
- *              the __init_io() function.  Primarily this would involve
- *              the scatter-gather table.
- */
-static void scsi_release_buffers(struct scsi_cmnd *cmd)
-{
-        if (cmd->sdb.table.nents)
-                sg_free_table_chained(&cmd->sdb.table, false);
-
-        memset(&cmd->sdb, 0, sizeof(cmd->sdb));
-
-        if (scsi_prot_sg_count(cmd))
-                sg_free_table_chained(&cmd->prot_sdb->table, false);
-}
-
-static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
-{
-        struct scsi_data_buffer *bidi_sdb = cmd->request->next_rq->special;
-
-        sg_free_table_chained(&bidi_sdb->table, false);
-        kmem_cache_free(scsi_sdb_cache, bidi_sdb);
-        cmd->request->next_rq->special = NULL;
-}
-
 /* Returns false when no more bytes to process, true if there are more */
 static bool scsi_end_request(struct request *req, blk_status_t error,
                 unsigned int bytes, unsigned int bidi_bytes)
@@ -687,37 +601,22 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
                 destroy_rcu_head(&cmd->rcu);
         }
 
-        if (req->mq_ctx) {
-                /*
-                 * In the MQ case the command gets freed by __blk_mq_end_request,
-                 * so we have to do all cleanup that depends on it earlier.
-                 *
-                 * We also can't kick the queues from irq context, so we
-                 * will have to defer it to a workqueue.
-                 */
-                scsi_mq_uninit_cmd(cmd);
-
-                __blk_mq_end_request(req, error);
-
-                if (scsi_target(sdev)->single_lun ||
-                    !list_empty(&sdev->host->starved_list))
-                        kblockd_schedule_work(&sdev->requeue_work);
-                else
-                        blk_mq_run_hw_queues(q, true);
-        } else {
-                unsigned long flags;
-
-                if (bidi_bytes)
-                        scsi_release_bidi_buffers(cmd);
-                scsi_release_buffers(cmd);
-                scsi_put_command(cmd);
+        /*
+         * In the MQ case the command gets freed by __blk_mq_end_request,
+         * so we have to do all cleanup that depends on it earlier.
+         *
+         * We also can't kick the queues from irq context, so we
+         * will have to defer it to a workqueue.
+         */
+        scsi_mq_uninit_cmd(cmd);
 
-                spin_lock_irqsave(q->queue_lock, flags);
-                blk_finish_request(req, error);
-                spin_unlock_irqrestore(q->queue_lock, flags);
+        __blk_mq_end_request(req, error);
 
-                scsi_run_queue(q);
-        }
+        if (scsi_target(sdev)->single_lun ||
+            !list_empty(&sdev->host->starved_list))
+                kblockd_schedule_work(&sdev->requeue_work);
+        else
+                blk_mq_run_hw_queues(q, true);
 
         put_device(&sdev->sdev_gendev);
         return false;
@@ -766,13 +665,7 @@ static void scsi_io_completion_reprep(struct scsi_cmnd *cmd,
                                       struct request_queue *q)
 {
         /* A new command will be prepared and issued. */
-        if (q->mq_ops) {
-                scsi_mq_requeue_cmd(cmd);
-        } else {
-                /* Unprep request and put it back at head of the queue. */
-                scsi_release_buffers(cmd);
-                scsi_requeue_command(q, cmd);
-        }
+        scsi_mq_requeue_cmd(cmd);
 }
 
 /* Helper for scsi_io_completion() when special action required. */
@@ -1147,9 +1040,7 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb)
  */
 int scsi_init_io(struct scsi_cmnd *cmd)
 {
-        struct scsi_device *sdev = cmd->device;
         struct request *rq = cmd->request;
-        bool is_mq = (rq->mq_ctx != NULL);
         int error = BLKPREP_KILL;
 
         if (WARN_ON_ONCE(!blk_rq_nr_phys_segments(rq)))
@@ -1160,17 +1051,6 @@ int scsi_init_io(struct scsi_cmnd *cmd)
                 goto err_exit;
 
         if (blk_bidi_rq(rq)) {
-                if (!rq->q->mq_ops) {
-                        struct scsi_data_buffer *bidi_sdb =
-                                kmem_cache_zalloc(scsi_sdb_cache, GFP_ATOMIC);
-                        if (!bidi_sdb) {
-                                error = BLKPREP_DEFER;
-                                goto err_exit;
-                        }
-
-                        rq->next_rq->special = bidi_sdb;
-                }
-
                 error = scsi_init_sgtable(rq->next_rq, rq->next_rq->special);
                 if (error)
                         goto err_exit;
@@ -1210,14 +1090,7 @@ int scsi_init_io(struct scsi_cmnd *cmd)
 
         return BLKPREP_OK;
 err_exit:
-        if (is_mq) {
-                scsi_mq_free_sgtables(cmd);
-        } else {
-                scsi_release_buffers(cmd);
-                cmd->request->special = NULL;
-                scsi_put_command(cmd);
-                put_device(&sdev->sdev_gendev);
-        }
+        scsi_mq_free_sgtables(cmd);
         return error;
 }
 EXPORT_SYMBOL(scsi_init_io);
@@ -1423,75 +1296,6 @@ scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
         return ret;
 }
 
-static int
-scsi_prep_return(struct request_queue *q, struct request *req, int ret)
-{
-        struct scsi_device *sdev = q->queuedata;
-
-        switch (ret) {
-        case BLKPREP_KILL:
-        case BLKPREP_INVALID:
-                scsi_req(req)->result = DID_NO_CONNECT << 16;
-                /* release the command and kill it */
-                if (req->special) {
-                        struct scsi_cmnd *cmd = req->special;
-                        scsi_release_buffers(cmd);
-                        scsi_put_command(cmd);
-                        put_device(&sdev->sdev_gendev);
-                        req->special = NULL;
-                }
-                break;
-        case BLKPREP_DEFER:
-                /*
-                 * If we defer, the blk_peek_request() returns NULL, but the
-                 * queue must be restarted, so we schedule a callback to happen
-                 * shortly.
-                 */
-                if (atomic_read(&sdev->device_busy) == 0)
-                        blk_delay_queue(q, SCSI_QUEUE_DELAY);
-                break;
-        default:
-                req->rq_flags |= RQF_DONTPREP;
-        }
-
-        return ret;
-}
-
-static int scsi_prep_fn(struct request_queue *q, struct request *req)
-{
-        struct scsi_device *sdev = q->queuedata;
-        struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
-        int ret;
-
-        ret = scsi_prep_state_check(sdev, req);
-        if (ret != BLKPREP_OK)
-                goto out;
-
-        if (!req->special) {
-                /* Bail if we can't get a reference to the device */
-                if (unlikely(!get_device(&sdev->sdev_gendev))) {
-                        ret = BLKPREP_DEFER;
-                        goto out;
-                }
-
-                scsi_init_command(sdev, cmd);
-                req->special = cmd;
-        }
-
-        cmd->tag = req->tag;
-        cmd->request = req;
-        cmd->prot_op = SCSI_PROT_NORMAL;
-
-        ret = scsi_setup_cmnd(sdev, req);
-out:
-        return scsi_prep_return(q, req, ret);
-}
-
-static void scsi_unprep_fn(struct request_queue *q, struct request *req)
-{
-        scsi_uninit_cmd(blk_mq_rq_to_pdu(req));
-}
-
 /*
  * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
  * return 0.
@@ -1511,14 +1315,8 @@ static inline int scsi_dev_queue_ready(struct request_queue *q,
                 /*
                  * unblock after device_blocked iterates to zero
                  */
-                if (atomic_dec_return(&sdev->device_blocked) > 0) {
-                        /*
-                         * For the MQ case we take care of this in the caller.
-                         */
-                        if (!q->mq_ops)
-                                blk_delay_queue(q, SCSI_QUEUE_DELAY);
+                if (atomic_dec_return(&sdev->device_blocked) > 0)
                         goto out_dec;
-                }
                 SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
                                    "unblocking device at zero depth\n"));
         }
@@ -1653,13 +1451,13 @@ out_dec:
  * needs to return 'not busy'. Otherwise, request stacking drivers
  * may hold requests forever.
  */
-static int scsi_lld_busy(struct request_queue *q)
+static bool scsi_mq_lld_busy(struct request_queue *q)
 {
         struct scsi_device *sdev = q->queuedata;
         struct Scsi_Host *shost;
 
         if (blk_queue_dying(q))
-                return 0;
+                return false;
 
         shost = sdev->host;
 
@@ -1670,48 +1468,9 @@ static int scsi_lld_busy(struct request_queue *q)
          * in SCSI layer.
          */
         if (scsi_host_in_recovery(shost) || scsi_device_is_busy(sdev))
-                return 1;
-
-        return 0;
-}
-
-static bool scsi_mq_lld_busy(struct request_queue *q)
-{
-        return scsi_lld_busy(q);
-}
-
-/*
- * Kill a request for a dead device
- */
-static void scsi_kill_request(struct request *req, struct request_queue *q)
-{
-        struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
-        struct scsi_device *sdev;
-        struct scsi_target *starget;
-        struct Scsi_Host *shost;
-
-        blk_start_request(req);
-
-        scmd_printk(KERN_INFO, cmd, "killing request\n");
-
-        sdev = cmd->device;
-        starget = scsi_target(sdev);
-        shost = sdev->host;
-        scsi_init_cmd_errh(cmd);
-        cmd->result = DID_NO_CONNECT << 16;
-        atomic_inc(&cmd->device->iorequest_cnt);
-
-        /*
-         * SCSI request completion path will do scsi_device_unbusy(),
-         * bump busy counts.  To bump the counters, we need to dance
-         * with the locks as normal issue path does.
-         */
-        atomic_inc(&sdev->device_busy);
-        atomic_inc(&shost->host_busy);
-        if (starget->can_queue > 0)
-                atomic_inc(&starget->target_busy);
+                return true;
 
-        blk_complete_request(req);
+        return false;
 }
 
 static void scsi_softirq_done(struct request *rq)
@@ -1834,158 +1593,6 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
         return 0;
 }
 
-/**
- * scsi_done - Invoke completion on finished SCSI command.
- * @cmd: The SCSI Command for which a low-level device driver (LLDD) gives
- * ownership back to SCSI Core -- i.e. the LLDD has finished with it.
- *
- * Description: This function is the mid-level's (SCSI Core) interrupt routine,
- * which regains ownership of the SCSI command (de facto) from a LLDD, and
- * calls blk_complete_request() for further processing.
- *
- * This function is interrupt context safe.
- */
-static void scsi_done(struct scsi_cmnd *cmd)
-{
-        trace_scsi_dispatch_cmd_done(cmd);
-        blk_complete_request(cmd->request);
-}
-
-/*
- * Function:    scsi_request_fn()
- *
- * Purpose:     Main strategy routine for SCSI.
- *
- * Arguments:   q       - Pointer to actual queue.
- *
- * Returns:     Nothing
- *
- * Lock status: request queue lock assumed to be held when called.
- *
- * Note: See sd_zbc.c sd_zbc_write_lock_zone() for write order
- * protection for ZBC disks.
- */
-static void scsi_request_fn(struct request_queue *q)
-        __releases(q->queue_lock)
-        __acquires(q->queue_lock)
-{
-        struct scsi_device *sdev = q->queuedata;
-        struct Scsi_Host *shost;
-        struct scsi_cmnd *cmd;
-        struct request *req;
-
-        /*
-         * To start with, we keep looping until the queue is empty, or until
-         * the host is no longer able to accept any more requests.
-         */
-        shost = sdev->host;
-        for (;;) {
-                int rtn;
-                /*
-                 * get next queueable request.  We do this early to make sure
-                 * that the request is fully prepared even if we cannot
-                 * accept it.
-                 */
-                req = blk_peek_request(q);
-                if (!req)
-                        break;
-
-                if (unlikely(!scsi_device_online(sdev))) {
-                        sdev_printk(KERN_ERR, sdev,
-                                    "rejecting I/O to offline device\n");
-                        scsi_kill_request(req, q);
-                        continue;
-                }
-
-                if (!scsi_dev_queue_ready(q, sdev))
-                        break;
-
-                /*
-                 * Remove the request from the request list.
-                 */
-                if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
-                        blk_start_request(req);
-
-                spin_unlock_irq(q->queue_lock);
-                cmd = blk_mq_rq_to_pdu(req);
-                if (cmd != req->special) {
-                        printk(KERN_CRIT "impossible request in %s.\n"
-                                         "please mail a stack trace to "
-                                         "linux-scsi@vger.kernel.org\n",
-                                         __func__);
-                        blk_dump_rq_flags(req, "foo");
-                        BUG();
-                }
-
-                /*
-                 * We hit this when the driver is using a host wide
-                 * tag map. For device level tag maps the queue_depth check
-                 * in the device ready fn would prevent us from trying
-                 * to allocate a tag. Since the map is a shared host resource
-                 * we add the dev to the starved list so it eventually gets
-                 * a run when a tag is freed.
-                 */
-                if (blk_queue_tagged(q) && !(req->rq_flags & RQF_QUEUED)) {
-                        spin_lock_irq(shost->host_lock);
-                        if (list_empty(&sdev->starved_entry))
-                                list_add_tail(&sdev->starved_entry,
-                                              &shost->starved_list);
-                        spin_unlock_irq(shost->host_lock);
-                        goto not_ready;
-                }
-
-                if (!scsi_target_queue_ready(shost, sdev))
-                        goto not_ready;
-
-                if (!scsi_host_queue_ready(q, shost, sdev))
-                        goto host_not_ready;
-        
-                if (sdev->simple_tags)
-                        cmd->flags |= SCMD_TAGGED;
-                else
-                        cmd->flags &= ~SCMD_TAGGED;
-
-                /*
-                 * Finally, initialize any error handling parameters, and set up
-                 * the timers for timeouts.
-                 */
-                scsi_init_cmd_errh(cmd);
-
-                /*
-                 * Dispatch the command to the low-level driver.
-                 */
-                cmd->scsi_done = scsi_done;
-                rtn = scsi_dispatch_cmd(cmd);
-                if (rtn) {
-                        scsi_queue_insert(cmd, rtn);
-                        spin_lock_irq(q->queue_lock);
-                        goto out_delay;
-                }
-                spin_lock_irq(q->queue_lock);
-        }
-
-        return;
-
- host_not_ready:
-        if (scsi_target(sdev)->can_queue > 0)
-                atomic_dec(&scsi_target(sdev)->target_busy);
- not_ready:
-        /*
-         * lock q, handle tag, requeue req, and decrement device_busy. We
-         * must return with queue_lock held.
-         *
-         * Decrementing device_busy without checking it is OK, as all such
-         * cases (host limits or settings) should run the queue at some
-         * later time.
-         */
-        spin_lock_irq(q->queue_lock);
-        blk_requeue_request(q, req);
-        atomic_dec(&sdev->device_busy);
-out_delay:
-        if (!atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
-                blk_delay_queue(q, SCSI_QUEUE_DELAY);
-}
-
 static inline blk_status_t prep_to_mq(int ret)
 {
         switch (ret) {
@@ -2248,77 +1855,6 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(__scsi_init_queue);
 
-static int scsi_old_init_rq(struct request_queue *q, struct request *rq,
-                            gfp_t gfp)
-{
-        struct Scsi_Host *shost = q->rq_alloc_data;
-        const bool unchecked_isa_dma = shost->unchecked_isa_dma;
-        struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
-
-        memset(cmd, 0, sizeof(*cmd));
-
-        if (unchecked_isa_dma)
-                cmd->flags |= SCMD_UNCHECKED_ISA_DMA;
-        cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma, gfp,
-                                                    NUMA_NO_NODE);
-        if (!cmd->sense_buffer)
-                goto fail;
-        cmd->req.sense = cmd->sense_buffer;
-
-        if (scsi_host_get_prot(shost) >= SHOST_DIX_TYPE0_PROTECTION) {
-                cmd->prot_sdb = kmem_cache_zalloc(scsi_sdb_cache, gfp);
-                if (!cmd->prot_sdb)
-                        goto fail_free_sense;
-        }
-
-        return 0;
-
-fail_free_sense:
-        scsi_free_sense_buffer(unchecked_isa_dma, cmd->sense_buffer);
-fail:
-        return -ENOMEM;
-}
-
-static void scsi_old_exit_rq(struct request_queue *q, struct request *rq)
-{
-        struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
-
-        if (cmd->prot_sdb)
-                kmem_cache_free(scsi_sdb_cache, cmd->prot_sdb);
-        scsi_free_sense_buffer(cmd->flags & SCMD_UNCHECKED_ISA_DMA,
-                               cmd->sense_buffer);
-}
-
-struct request_queue *scsi_old_alloc_queue(struct scsi_device *sdev)
-{
-        struct Scsi_Host *shost = sdev->host;
-        struct request_queue *q;
-
-        q = blk_alloc_queue_node(GFP_KERNEL, NUMA_NO_NODE, NULL);
-        if (!q)
-                return NULL;
-        q->cmd_size = sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
-        q->rq_alloc_data = shost;
-        q->request_fn = scsi_request_fn;
-        q->init_rq_fn = scsi_old_init_rq;
-        q->exit_rq_fn = scsi_old_exit_rq;
-        q->initialize_rq_fn = scsi_initialize_rq;
-
-        if (blk_init_allocated_queue(q) < 0) {
-                blk_cleanup_queue(q);
-                return NULL;
-        }
-
-        __scsi_init_queue(shost, q);
-        blk_queue_flag_set(QUEUE_FLAG_SCSI_PASSTHROUGH, q);
-        blk_queue_prep_rq(q, scsi_prep_fn);
-        blk_queue_unprep_rq(q, scsi_unprep_fn);
-        blk_queue_softirq_done(q, scsi_softirq_done);
-        blk_queue_rq_timed_out(q, scsi_times_out);
-        blk_queue_lld_busy(q, scsi_lld_busy);
-        return q;
-}
-
 static const struct blk_mq_ops scsi_mq_ops = {
         .get_budget     = scsi_mq_get_budget,
         .put_budget     = scsi_mq_put_budget,
@@ -2386,10 +1922,7 @@ struct scsi_device *scsi_device_from_queue(struct request_queue *q)
 {
         struct scsi_device *sdev = NULL;
 
-        if (q->mq_ops) {
-                if (q->mq_ops == &scsi_mq_ops)
-                        sdev = q->queuedata;
-        } else if (q->request_fn == scsi_request_fn)
+        if (q->mq_ops == &scsi_mq_ops)
                 sdev = q->queuedata;
         if (!sdev || !get_device(&sdev->sdev_gendev))
                 sdev = NULL;
@@ -2993,39 +2526,6 @@ void sdev_evt_send_simple(struct scsi_device *sdev,
 EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
 
 /**
- * scsi_request_fn_active() - number of kernel threads inside scsi_request_fn()
- * @sdev: SCSI device to count the number of scsi_request_fn() callers for.
- */
-static int scsi_request_fn_active(struct scsi_device *sdev)
-{
-        struct request_queue *q = sdev->request_queue;
-        int request_fn_active;
-
-        WARN_ON_ONCE(sdev->host->use_blk_mq);
-
-        spin_lock_irq(q->queue_lock);
-        request_fn_active = q->request_fn_active;
-        spin_unlock_irq(q->queue_lock);
-
-        return request_fn_active;
-}
-
-/**
- * scsi_wait_for_queuecommand() - wait for ongoing queuecommand() calls
- * @sdev: SCSI device pointer.
- *
- * Wait until the ongoing shost->hostt->queuecommand() calls that are
- * invoked from scsi_request_fn() have finished.
- */
-static void scsi_wait_for_queuecommand(struct scsi_device *sdev)
-{
-        WARN_ON_ONCE(sdev->host->use_blk_mq);
-
-        while (scsi_request_fn_active(sdev))
-                msleep(20);
-}
-
-/**
  *      scsi_device_quiesce - Block user issued commands.
  *      @sdev:  scsi device to quiesce.
  *
@@ -3148,7 +2648,6 @@ EXPORT_SYMBOL(scsi_target_resume);
 int scsi_internal_device_block_nowait(struct scsi_device *sdev)
 {
         struct request_queue *q = sdev->request_queue;
-        unsigned long flags;
         int err = 0;
 
         err = scsi_device_set_state(sdev, SDEV_BLOCK);
@@ -3164,14 +2663,7 @@ int scsi_internal_device_block_nowait(struct scsi_device *sdev)
          * block layer from calling the midlayer with this device's
          * request queue. 
          */
-        if (q->mq_ops) {
-                blk_mq_quiesce_queue_nowait(q);
-        } else {
-                spin_lock_irqsave(q->queue_lock, flags);
-                blk_stop_queue(q);
-                spin_unlock_irqrestore(q->queue_lock, flags);
-        }
-
+        blk_mq_quiesce_queue_nowait(q);
         return 0;
 }
 EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
@@ -3202,12 +2694,8 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
 
         mutex_lock(&sdev->state_mutex);
         err = scsi_internal_device_block_nowait(sdev);
-        if (err == 0) {
-                if (q->mq_ops)
-                        blk_mq_quiesce_queue(q);
-                else
-                        scsi_wait_for_queuecommand(sdev);
-        }
+        if (err == 0)
+                blk_mq_quiesce_queue(q);
         mutex_unlock(&sdev->state_mutex);
 
         return err;
@@ -3216,15 +2704,8 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
 void scsi_start_queue(struct scsi_device *sdev)
 {
         struct request_queue *q = sdev->request_queue;
-        unsigned long flags;
 
-        if (q->mq_ops) {
-                blk_mq_unquiesce_queue(q);
-        } else {
-                spin_lock_irqsave(q->queue_lock, flags);
-                blk_start_queue(q);
-                spin_unlock_irqrestore(q->queue_lock, flags);
-        }
+        blk_mq_unquiesce_queue(q);
 }
 
 /**
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 99f1db5e467e..5f21547b2ad2 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -92,7 +92,6 @@ extern void scsi_queue_insert(struct scsi_cmnd *cmd, int reason);
 extern void scsi_io_completion(struct scsi_cmnd *, unsigned int);
 extern void scsi_run_host_queues(struct Scsi_Host *shost);
 extern void scsi_requeue_run_queue(struct work_struct *work);
-extern struct request_queue *scsi_old_alloc_queue(struct scsi_device *sdev);
 extern struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev);
 extern void scsi_start_queue(struct scsi_device *sdev);
 extern int scsi_mq_setup_tags(struct Scsi_Host *shost);
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 78ca63dfba4a..dd0d516f65e2 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -266,10 +266,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
          */
         sdev->borken = 1;
 
-        if (shost_use_blk_mq(shost))
-                sdev->request_queue = scsi_mq_alloc_queue(sdev);
-        else
-                sdev->request_queue = scsi_old_alloc_queue(sdev);
+        sdev->request_queue = scsi_mq_alloc_queue(sdev);
         if (!sdev->request_queue) {
                 /* release fn is set up in scsi_sysfs_device_initialise, so
                  * have to free and put manually here */
@@ -280,11 +277,6 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
         WARN_ON_ONCE(!blk_get_queue(sdev->request_queue));
         sdev->request_queue->queuedata = sdev;
 
-        if (!shost_use_blk_mq(sdev->host)) {
-                blk_queue_init_tags(sdev->request_queue,
-                                    sdev->host->cmd_per_lun, shost->bqt,
-                                    shost->hostt->tag_alloc_policy);
-        }
         scsi_change_queue_depth(sdev, sdev->host->cmd_per_lun ?
                                         sdev->host->cmd_per_lun : 1);
 
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 3aee9464a7bf..6a9040faed00 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -367,7 +367,6 @@ store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline);
 
-shost_rd_attr(use_blk_mq, "%d\n");
 shost_rd_attr(unique_id, "%u\n");
 shost_rd_attr(cmd_per_lun, "%hd\n");
 shost_rd_attr(can_queue, "%hd\n");
@@ -386,6 +385,13 @@ show_host_busy(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR(host_busy, S_IRUGO, show_host_busy, NULL);
 
+static ssize_t
+show_use_blk_mq(struct device *dev, struct device_attribute *attr, char *buf)
+{
+        return sprintf(buf, "1\n");
+}
+static DEVICE_ATTR(use_blk_mq, S_IRUGO, show_use_blk_mq, NULL);
+
 static struct attribute *scsi_sysfs_shost_attrs[] = {
         &dev_attr_use_blk_mq.attr,
         &dev_attr_unique_id.attr,
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 23d7cca36ff0..fb308ea8e9a5 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -8100,12 +8100,6 @@ int ufshcd_alloc_host(struct device *dev, struct ufs_hba **hba_handle)
                 goto out_error;
         }
 
-        /*
-         * Do not use blk-mq at this time because blk-mq does not support
-         * runtime pm.
-         */
-        host->use_blk_mq = false;
-
         hba = shost_priv(host);
         hba->host = host;
         hba->dev = dev;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 5ea06d310a25..aa760df8c6b3 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -11,7 +11,6 @@
 #include <linux/blk-mq.h>
 #include <scsi/scsi.h>
 
-struct request_queue;
 struct block_device;
 struct completion;
 struct module;
@@ -22,7 +21,6 @@ struct scsi_target;
 struct Scsi_Host;
 struct scsi_host_cmd_pool;
 struct scsi_transport_template;
-struct blk_queue_tags;
 
 
 /*
@@ -547,14 +545,8 @@ struct Scsi_Host {
         struct scsi_host_template *hostt;
         struct scsi_transport_template *transportt;
 
-        /*
-         * Area to keep a shared tag map (if needed, will be
-         * NULL if not).
-         */
-        union {
-                struct blk_queue_tag    *bqt;
-                struct blk_mq_tag_set   tag_set;
-        };
+        /* Area to keep a shared tag map */
+        struct blk_mq_tag_set   tag_set;
 
         atomic_t host_busy;                /* commands actually active on low-level */
         atomic_t host_blocked;
@@ -648,7 +640,6 @@ struct Scsi_Host {
         /* The controller does not support WRITE SAME */
         unsigned no_write_same:1;
 
-        unsigned use_blk_mq:1;
         unsigned use_cmd_list:1;
 
         /* Host responded with short (<36 bytes) INQUIRY result */
@@ -742,11 +733,6 @@ static inline int scsi_host_in_recovery(struct Scsi_Host *shost)
                 shost->tmf_in_progress;
 }
 
-static inline bool shost_use_blk_mq(struct Scsi_Host *shost)
-{
-        return shost->use_blk_mq;
-}
-
 extern int scsi_queue_work(struct Scsi_Host *, struct work_struct *);
 extern void scsi_flush_work(struct Scsi_Host *);
 
diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index e192a0caa850..6053d46e794e 100644
--- a/include/scsi/scsi_tcq.h
+++ b/include/scsi/scsi_tcq.h
@@ -23,19 +23,15 @@ static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host *shost,
                 int tag)
 {
         struct request *req = NULL;
+        u16 hwq;
 
         if (tag == SCSI_NO_TAG)
                 return NULL;
 
-        if (shost_use_blk_mq(shost)) {
-                u16 hwq = blk_mq_unique_tag_to_hwq(tag);
-
-                if (hwq < shost->tag_set.nr_hw_queues) {
-                        req = blk_mq_tag_to_rq(shost->tag_set.tags[hwq],
-                                blk_mq_unique_tag_to_tag(tag));
-                }
-        } else {
-                req = blk_map_queue_find_tag(shost->bqt, tag);
+        hwq = blk_mq_unique_tag_to_hwq(tag);
+        if (hwq < shost->tag_set.nr_hw_queues) {
+                req = blk_mq_tag_to_rq(shost->tag_set.tags[hwq],
+                                        blk_mq_unique_tag_to_tag(tag));
         }
 
         if (!req)