diff --git a/scst/src/dev_handlers/scst_vdisk.c b/scst/src/dev_handlers/scst_vdisk.c
index d09b55ce1..e280cea16 100644
--- a/scst/src/dev_handlers/scst_vdisk.c
+++ b/scst/src/dev_handlers/scst_vdisk.c
@@ -1308,13 +1308,17 @@ next:
 
 	res = scst_pr_set_cluster_mode(dev, dev->cluster_mode,
 				       virt_dev->t10_dev_id);
+	if (res)
+		goto out;
+
+	percpu_ref_get(&dev->refcnt);
 
 out:
 	TRACE_EXIT();
 	return res;
 }
 
-/* scst_mutex supposed to be held */
+/* Detach a virtual device from a device. scst_mutex is supposed to be held. */
 static void vdisk_detach(struct scst_device *dev)
 {
 	struct scst_vdisk_dev *virt_dev = dev->dh_priv;
@@ -1332,6 +1336,8 @@ static void vdisk_detach(struct scst_device *dev)
 
 	/* virt_dev will be freed by the caller */
 	dev->dh_priv = NULL;
+	virt_dev->dev = NULL;
+	percpu_ref_put(&dev->refcnt);
 
 	TRACE_EXIT();
 	return;
diff --git a/scst/src/scst_copy_mgr.c b/scst/src/scst_copy_mgr.c
index 90eb25a7a..44a750126 100644
--- a/scst/src/scst_copy_mgr.c
+++ b/scst/src/scst_copy_mgr.c
@@ -2441,6 +2441,7 @@ out_put:
 	scst_put_buf_full(cmd, buf);
 
 out:
+	percpu_ref_put(&dev->refcnt);
 	TRACE_EXIT();
 	return;
 }
@@ -2464,6 +2465,7 @@ static int scst_cm_send_init_inquiry(struct scst_device *dev,
 		}
 		priv->cm_init_inq_finish_fn = scst_cm_init_inq_finish;
 		priv->dev = dev;
+		percpu_ref_get(&dev->refcnt);
 	}
 
 	lun = scst_pack_lun(unpacked_lun, scst_cm_sess->acg->addr_method);
diff --git a/scst/src/scst_lib.c b/scst/src/scst_lib.c
index 28d1967e7..612946eb6 100644
--- a/scst/src/scst_lib.c
+++ b/scst/src/scst_lib.c
@@ -4344,6 +4344,8 @@ static struct scst_acg_dev *scst_alloc_acg_dev(struct scst_acg *acg,
 	res->acg = acg;
 	res->lun = lun;
 
+	percpu_ref_get(&dev->refcnt);
+
 out:
 	TRACE_EXIT_HRES(res);
 	return res;
@@ -4374,6 +4376,7 @@ static void scst_del_acg_dev(struct scst_acg_dev *acg_dev,
  */
 static void scst_free_acg_dev(struct scst_acg_dev *acg_dev)
 {
+	percpu_ref_put(&acg_dev->dev->refcnt);
 	kmem_cache_free(scst_acgd_cachep, acg_dev);
 }
 
@@ -5467,6 +5470,8 @@ static int scst_alloc_add_tgt_dev(struct scst_session *sess,
 
 	*out_tgt_dev = tgt_dev;
 
+	percpu_ref_get(&dev->refcnt);
+
 out:
 	TRACE_EXIT_RES(res);
 	return res;
@@ -5569,6 +5574,8 @@ static void scst_free_tgt_dev(struct scst_tgt_dev *tgt_dev)
 
 	kmem_cache_free(scst_tgtd_cachep, tgt_dev);
 
+	percpu_ref_put(&dev->refcnt);
+
 	TRACE_EXIT();
 	return;
 }
@@ -5770,8 +5777,7 @@ struct scst_cmd *__scst_create_prepare_internal_cmd(const uint8_t *cdb,
 	}
 
 	scst_sess_get(res->sess);
-	if (res->tgt_dev != NULL)
-		res->cpu_cmd_counter = scst_get();
+	res->cpu_cmd_counter = scst_get();
 
 	TRACE(TRACE_SCSI, "New internal cmd %p (op %s)", res,
 		scst_get_opcode_name(res));
diff --git a/scst/src/scst_targ.c b/scst/src/scst_targ.c
index 5ca787b74..282e56724 100644
--- a/scst/src/scst_targ.c
+++ b/scst/src/scst_targ.c
@@ -558,6 +558,8 @@ static void __scst_rx_cmd(struct scst_cmd *cmd, struct scst_session *sess,
 {
 	TRACE_ENTRY();
 
+	WARN_ON_ONCE(cmd->cpu_cmd_counter);
+
 	cmd->sess = sess;
 	scst_sess_get(sess);