diff --git a/block/genhd.c b/block/genhd.c
index b26a5ea115d0..d06ba7e731a4 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -662,6 +662,7 @@ void del_gendisk(struct gendisk *disk)
 	struct disk_part_iter piter;
 	struct hd_struct *part;
 
+	WARN_ON(!(disk->flags & GENHD_FL_UP));
 	blk_integrity_del(disk);
 	disk_del_events(disk);
 
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 6f7128f49c30..7d987dcb8fee 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1073,6 +1073,7 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget,
 	 */
 	sdev = scsi_device_lookup_by_target(starget, lun);
 	if (sdev) {
+		printk("Reusing sdev %p\n", sdev);
 		if (rescan != SCSI_SCAN_INITIAL || !scsi_device_created(sdev)) {
 			SCSI_LOG_SCAN_BUS(3, sdev_printk(KERN_INFO, sdev,
 				"scsi scan: device exists on %s\n",
@@ -1089,8 +1090,10 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget,
 			return SCSI_SCAN_LUN_PRESENT;
 		}
 		scsi_device_put(sdev);
-	} else
+	} else {
 		sdev = scsi_alloc_sdev(starget, lun, hostdata);
+		printk("Created sdev %p\n", sdev);
+	}
 	if (!sdev)
 		goto out;
 
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 6d861d090e9f..6c172099aa23 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -496,6 +496,7 @@ static void cgwb_release_workfn(struct work_struct *work)
 	wb_exit(wb);
 	kfree_rcu(wb, rcu);
 
+	printk("CGWB release! %p\n", bdi);
 	if (atomic_dec_and_test(&bdi->usage_cnt))
 		wake_up_all(&cgwb_release_wait);
 }
@@ -668,6 +669,7 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
 {
 	int ret;
 
+	printk("CGWB init %p\n", bdi);
 	INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
 	bdi->cgwb_congested_tree = RB_ROOT;
 	atomic_set(&bdi->usage_cnt, 1);
@@ -709,6 +711,7 @@ static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
 	 * all cgwb's and cgwb_congested's ever created on @bdi.
 	 */
 	atomic_dec(&bdi->usage_cnt);
+	printk("CGWB %p usage_cnt: %u\n", bdi, atomic_read(&bdi->usage_cnt));
 	wait_event(cgwb_release_wait, !atomic_read(&bdi->usage_cnt));
 }
 
@@ -877,10 +880,15 @@ static void bdi_remove_from_list(struct backing_dev_info *bdi)
 
 void bdi_unregister(struct backing_dev_info *bdi)
 {
+	WARN_ON(!test_bit(WB_registered, &bdi->wb.state));
 	/* make sure nobody finds us on the bdi_list anymore */
+	printk("Unreg1\n");
 	bdi_remove_from_list(bdi);
+	printk("Unreg2\n");
 	wb_shutdown(&bdi->wb);
+	printk("Unreg3\n");
 	cgwb_bdi_destroy(bdi);
+	printk("Unreg4\n");
 
 	if (bdi->dev) {
 		bdi_debug_unregister(bdi);