diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 838f07e2b64a..8d5aa55309e4 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -37,9 +37,13 @@ static const u64 cfq_target_latency = (u64)NSEC_PER_SEC * 3/10; /* 300 ms */
 static const int cfq_hist_divisor = 4;
 
 /*
- * offset from end of service tree
+ * offset from end of queue service tree for idle class
  */
 #define CFQ_IDLE_DELAY		(NSEC_PER_SEC / 5)
+/* offset from end of group service tree under time slice mode */
+#define CFQ_SLICE_MODE_GROUP_DELAY (NSEC_PER_SEC / 5)
+/* offset from end of group service under IOPS mode */
+#define CFQ_IOPS_MODE_GROUP_DELAY (HZ / 5)
 
 /*
  * below this threshold, we consider thinktime immediate
@@ -1361,6 +1365,14 @@ cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
 	cfqg->vfraction = max_t(unsigned, vfr, 1);
 }
 
+static inline u64 cfq_get_cfqg_vdisktime_delay(struct cfq_data *cfqd)
+{
+	if (!iops_mode(cfqd))
+		return CFQ_SLICE_MODE_GROUP_DELAY;
+	else
+		return CFQ_IOPS_MODE_GROUP_DELAY;
+}
+
 static void
 cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
@@ -1380,7 +1392,8 @@ cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
 	n = rb_last(&st->rb);
 	if (n) {
 		__cfqg = rb_entry_cfqg(n);
-		cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
+		cfqg->vdisktime = __cfqg->vdisktime +
+			cfq_get_cfqg_vdisktime_delay(cfqd);
 	} else
 		cfqg->vdisktime = st->min_vdisktime;
 	cfq_group_service_tree_add(st, cfqg);
@@ -3758,16 +3771,14 @@ static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 }
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
-static bool check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
+static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
 {
 	struct cfq_data *cfqd = cic_to_cfqd(cic);
 	struct cfq_queue *cfqq;
 	uint64_t serial_nr;
-	bool nonroot_cg;
 
 	rcu_read_lock();
 	serial_nr = bio_blkcg(bio)->css.serial_nr;
-	nonroot_cg = bio_blkcg(bio) != &blkcg_root;
 	rcu_read_unlock();
 
 	/*
@@ -3775,7 +3786,7 @@ static bool check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
 	 * spuriously on a newly created cic but there's no harm.
 	 */
 	if (unlikely(!cfqd) || likely(cic->blkcg_serial_nr == serial_nr))
-		return nonroot_cg;
+		return;
 
 	/*
 	 * Drop reference to queues.  New queues will be assigned in new
@@ -3796,12 +3807,10 @@ static bool check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
 	}
 
 	cic->blkcg_serial_nr = serial_nr;
-	return nonroot_cg;
 }
 #else
-static inline bool check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
+static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
 {
-	return false;
 }
 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
 
@@ -3860,6 +3869,8 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
 		goto out;
 	}
 
+	/* cfq_init_cfqq() assumes cfqq->ioprio_class is initialized. */
+	cfqq->ioprio_class = IOPRIO_CLASS_NONE;
 	cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
 	cfq_init_prio_data(cfqq, cic);
 	cfq_link_cfqq_cfqg(cfqq, cfqg);
@@ -4444,12 +4455,11 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
 	const int rw = rq_data_dir(rq);
 	const bool is_sync = rq_is_sync(rq);
 	struct cfq_queue *cfqq;
-	bool disable_wbt;
 
 	spin_lock_irq(q->queue_lock);
 
 	check_ioprio_changed(cic, bio);
-	disable_wbt = check_blkcg_changed(cic, bio);
+	check_blkcg_changed(cic, bio);
 new_queue:
 	cfqq = cic_to_cfqq(cic, is_sync);
 	if (!cfqq || cfqq == &cfqd->oom_cfqq) {
@@ -4486,9 +4496,6 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
 	rq->elv.priv[1] = cfqq->cfqg;
 	spin_unlock_irq(q->queue_lock);
 
-	if (disable_wbt)
-		wbt_disable_default(q);
-
 	return 0;
 }
 
@@ -4701,6 +4708,7 @@ static void cfq_registered_queue(struct request_queue *q)
 	 */
 	if (blk_queue_nonrot(q))
 		cfqd->cfq_slice_idle = 0;
+	wbt_disable_default(q);
 }
 
 /*
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 99d4e1af5502..3a1a64c87be1 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -195,6 +195,25 @@ static void blkdev_bio_end_io_simple(struct bio *bio)
 	wake_up_process(waiter);
 }
 
+noinline static void debug_schedule(struct bio *bio)
+{
+	u64 t0 = local_clock();
+	u64 t1, t2;
+	if (io_schedule_timeout(HZ * 60) <= 0) {
+		t1 = local_clock();
+		//printk(KERN_WARNING "__blkdev_direct_IO_simple wait timeout %p\n", bio);
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (READ_ONCE(bio->bi_private)) {
+			io_schedule();
+		}
+		t2 = local_clock();
+		__set_current_state(TASK_RUNNING);
+		printk(KERN_WARNING "__blkdev_direct_IO_simple wait recovered "
+			"%p %p %08x %llu %llu %llu\n",
+			bio, bio->bi_bdev, bio->bi_opf, t0, t1, t2);
+	}
+}
+
 static ssize_t
 __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 		int nr_pages)
@@ -248,7 +267,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 			break;
 		if (!(iocb->ki_flags & IOCB_HIPRI) ||
 		    !blk_mq_poll(bdev_get_queue(bdev), qc))
-			io_schedule();
+			debug_schedule(&bio);
 	}
 	__set_current_state(TASK_RUNNING);