diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 9d6f04103f01ae965959bb8b791373ffb633b020..4838c2b16f2c4759fb0aa0f7375b2b0d1b07074e 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -26,7 +26,16 @@ static int cfq_slice_async = HZ / 25;
 static const int cfq_slice_async_rq = 2;
 static int cfq_slice_idle = HZ / 125;
 
+/*
+ * grace period before allowing idle class to get disk access
+ */
 #define CFQ_IDLE_GRACE		(HZ / 10)
+
+/*
+ * below this threshold, we consider thinktime immediate
+ */
+#define CFQ_MIN_TT		(2)
+
 #define CFQ_SLICE_SCALE		(5)
 
 #define CFQ_KEY_ASYNC		(0)
@@ -69,10 +78,9 @@ struct cfq_data {
 	/*
 	 * rr list of queues with requests and the count of them
 	 */
-	struct list_head rr_list[CFQ_PRIO_LISTS];
+	struct rb_root service_tree;
 	struct list_head cur_rr;
 	struct list_head idle_rr;
-	unsigned long cur_rr_tick;
 	unsigned int busy_queues;
 
 	/*
@@ -91,8 +99,6 @@ struct cfq_data {
 
 	struct cfq_queue *active_queue;
 	struct cfq_io_context *active_cic;
-	int cur_prio, cur_end_prio;
-	unsigned long prio_time;
 	unsigned int dispatch_slice;
 
 	struct timer_list idle_class_timer;
@@ -131,8 +137,10 @@ struct cfq_queue {
 	unsigned int key;
 	/* member of the rr/busy/cur/idle cfqd list */
 	struct list_head cfq_list;
-	/* in what tick we were last serviced */
-	unsigned long rr_tick;
+	/* service_tree member */
+	struct rb_node rb_node;
+	/* service_tree key */
+	unsigned long rb_key;
 	/* sorted list of pending requests */
 	struct rb_root sort_list;
 	/* if fifo isn't expired, next request to serve */
@@ -147,8 +155,6 @@ struct cfq_queue {
 	struct list_head fifo;
 
 	unsigned long slice_end;
-	unsigned long service_last;
-	unsigned long slice_start;
 	long slice_resid;
 
 	/* number of requests that are on the dispatch list or inside driver */
@@ -240,30 +246,26 @@ static inline pid_t cfq_queue_pid(struct task_struct *task, int rw, int is_sync)
  * if a queue is marked sync and has sync io queued. A sync queue with async
  * io only, should not get full sync slice length.
  */
-static inline int
-cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
+				 unsigned short prio)
 {
-	const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
+	const int base_slice = cfqd->cfq_slice[sync];
 
-	WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
+	WARN_ON(prio >= IOPRIO_BE_NR);
+
+	return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
+}
 
-	return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
+static inline int
+cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
 }
 
 static inline void
 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
 	cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
-	cfqq->slice_end += cfqq->slice_resid;
-
-	/*
-	 * Don't carry over residual for more than one slice, we only want
-	 * to slightly correct the fairness. Carrying over forever would
-	 * easily introduce oscillations.
-	 */
-	cfqq->slice_resid = 0;
-
-	cfqq->slice_start = jiffies;
 }
 
 /*
@@ -403,33 +405,50 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 	return cfq_choose_req(cfqd, next, prev);
 }
 
-/*
- * This function finds out where to insert a BE queue in the service hierarchy
- */
-static void cfq_resort_be_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-				int preempted)
+static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
+				      struct cfq_queue *cfqq)
 {
-	if (!cfq_cfqq_sync(cfqq))
-		list_add_tail(&cfqq->cfq_list, &cfqd->rr_list[cfqq->ioprio]);
-	else {
-		struct list_head *n = &cfqd->rr_list[cfqq->ioprio];
+	/*
+	 * just an approximation, should be ok.
+	 */
+	return ((cfqd->busy_queues - 1) * cfq_prio_slice(cfqd, 1, 0));
+}
+
+static void cfq_service_tree_add(struct cfq_data *cfqd,
+				    struct cfq_queue *cfqq)
+{
+	struct rb_node **p = &cfqd->service_tree.rb_node;
+	struct rb_node *parent = NULL;
+	struct cfq_queue *__cfqq;
+	unsigned long rb_key;
+
+	rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
+	rb_key += cfqq->slice_resid;
+	cfqq->slice_resid = 0;
 
+	if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
 		/*
-		 * sort by last service, but don't cross a new or async
-		 * queue. we don't cross a new queue because it hasn't
-		 * been service before, and we don't cross an async
-		 * queue because it gets added to the end on expire.
+		 * same position, nothing more to do
 		 */
-		while ((n = n->prev) != &cfqd->rr_list[cfqq->ioprio]) {
-			struct cfq_queue *__c = list_entry_cfqq(n);
+		if (rb_key == cfqq->rb_key)
+			return;
 
-			if (!cfq_cfqq_sync(__c) || !__c->service_last)
-				break;
-			if (time_before(__c->service_last, cfqq->service_last))
-				break;
-		}
-		list_add(&cfqq->cfq_list, n);
+		rb_erase(&cfqq->rb_node, &cfqd->service_tree);
 	}
+
+	while (*p) {
+		parent = *p;
+		__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
+
+		if (rb_key < __cfqq->rb_key)
+			p = &(*p)->rb_left;
+		else
+			p = &(*p)->rb_right;
+	}
+
+	cfqq->rb_key = rb_key;
+	rb_link_node(&cfqq->rb_node, parent, p);
+	rb_insert_color(&cfqq->rb_node, &cfqd->service_tree);
 }
 
 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
@@ -443,7 +462,7 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 	if (!cfq_cfqq_on_rr(cfqq))
 		return;
 
-	list_del(&cfqq->cfq_list);
+	list_del_init(&cfqq->cfq_list);
 
 	if (cfq_class_rt(cfqq)) {
 		/*
@@ -465,7 +484,7 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 		/*
 		 * So we get here, ergo the queue is a regular best-effort queue
 		 */
-		cfq_resort_be_queue(cfqd, cfqq, preempted);
+		cfq_service_tree_add(cfqd, cfqq);
 	}
 }
 
@@ -490,6 +509,11 @@ cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	cfq_clear_cfqq_on_rr(cfqq);
 	list_del_init(&cfqq->cfq_list);
 
+	if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
+		rb_erase(&cfqq->rb_node, &cfqd->service_tree);
+		RB_CLEAR_NODE(&cfqq->rb_node);
+	}
+
 	BUG_ON(!cfqd->busy_queues);
 	cfqd->busy_queues--;
 }
@@ -684,7 +708,6 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 		cfq_clear_cfqq_fifo_expire(cfqq);
 		cfq_mark_cfqq_slice_new(cfqq);
 		cfq_clear_cfqq_queue_new(cfqq);
-		cfqq->rr_tick = cfqd->cur_rr_tick;
 	}
 
 	cfqd->active_queue = cfqq;
@@ -732,114 +755,19 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted,
 		__cfq_slice_expired(cfqd, cfqq, preempted, timed_out);
 }
 
-/*
- * 0
- * 0,1
- * 0,1,2
- * 0,1,2,3
- * 0,1,2,3,4
- * 0,1,2,3,4,5
- * 0,1,2,3,4,5,6
- * 0,1,2,3,4,5,6,7
- */
-static int cfq_get_next_prio_level(struct cfq_data *cfqd)
-{
-	int prio, wrap;
-
-	prio = -1;
-	wrap = 0;
-	do {
-		int p;
-
-		for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
-			if (!list_empty(&cfqd->rr_list[p])) {
-				prio = p;
-				break;
-			}
-		}
-
-		if (prio != -1)
-			break;
-		cfqd->cur_prio = 0;
-		if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
-			cfqd->cur_end_prio = 0;
-			if (wrap)
-				break;
-			wrap = 1;
-		}
-	} while (1);
-
-	if (unlikely(prio == -1))
-		return -1;
-
-	BUG_ON(prio >= CFQ_PRIO_LISTS);
-
-	list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
-
-	cfqd->cur_prio = prio + 1;
-	if (cfqd->cur_prio > cfqd->cur_end_prio) {
-		cfqd->cur_end_prio = cfqd->cur_prio;
-		cfqd->cur_prio = 0;
-	}
-	if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
-		cfqd->cur_prio = 0;
-		cfqd->cur_end_prio = 0;
-	}
-
-	cfqd->cur_rr_tick++;
-	cfqd->prio_time = jiffies;
-	return prio;
-}
-
-static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
-					  struct request *rq)
-{
-	if (rq->sector >= cfqd->last_position)
-		return rq->sector - cfqd->last_position;
-	else
-		return cfqd->last_position - rq->sector;
-}
-
-static struct cfq_queue *cfq_get_best_queue(struct cfq_data *cfqd)
-{
-	struct cfq_queue *cfqq = NULL, *__cfqq;
-	sector_t best = -1, first = -1, dist;
-
-	list_for_each_entry(__cfqq, &cfqd->cur_rr, cfq_list) {
-		if (!__cfqq->next_rq || !cfq_cfqq_sync(__cfqq))
-			continue;
-
-		dist = cfq_dist_from_last(cfqd, __cfqq->next_rq);
-		if (first == -1)
-			first = dist;
-		if (dist < best) {
-			best = dist;
-			cfqq = __cfqq;
-		}
-	}
-
-	/*
-	 * Only async queue(s) available, grab first entry. Do the same
-	 * if the difference between the first and best isn't more than
-	 * twice, to obey fairness.
-	 */
-	if (!cfqq || (best && first != best && ((first / best) < 4)))
-		cfqq = list_entry_cfqq(cfqd->cur_rr.next);
-
-	return cfqq;
-}
-
 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 {
 	struct cfq_queue *cfqq = NULL;
 
-	if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) {
+	if (!list_empty(&cfqd->cur_rr)) {
 		/*
-		 * if current list is non-empty, grab first entry. if it is
-		 * empty, get next prio level and grab first entry then if any
-		 * are spliced
+		 * if current list is non-empty, grab first entry.
 		 */
-		cfqq = cfq_get_best_queue(cfqd);
+		cfqq = list_entry_cfqq(cfqd->cur_rr.next);
+	} else if (!RB_EMPTY_ROOT(&cfqd->service_tree)) {
+		struct rb_node *n = rb_first(&cfqd->service_tree);
+
+		cfqq = rb_entry(n, struct cfq_queue, rb_node);
 	} else if (!list_empty(&cfqd->idle_rr)) {
 		/*
 		 * if we have idle queues and no rt or be queues had pending
@@ -861,27 +789,20 @@ static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
 {
 	struct cfq_queue *cfqq;
 
-	do {
-		long prio;
-
-		cfqq = cfq_get_next_queue(cfqd);
-		if (!cfqq)
-			break;
-
-		prio = cfq_prio_to_slice(cfqd, cfqq);
-		if (cfqq->slice_resid > -prio)
-			break;
-
-		cfqq->slice_resid += prio;
-		list_del_init(&cfqq->cfq_list);
-		list_add_tail(&cfqq->cfq_list, &cfqd->rr_list[cfqq->ioprio]);
-		cfqq = NULL;
-	} while (1);
-
+	cfqq = cfq_get_next_queue(cfqd);
 	__cfq_set_active_queue(cfqd, cfqq);
 	return cfqq;
 }
 
+static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
+					  struct request *rq)
+{
+	if (rq->sector >= cfqd->last_position)
+		return rq->sector - cfqd->last_position;
+	else
+		return cfqd->last_position - rq->sector;
+}
+
 static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
 {
 	struct cfq_io_context *cic = cfqd->active_cic;
@@ -892,45 +813,15 @@ static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
 	return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
 }
 
-static struct cfq_queue *__cfq_close_cooperator(struct cfq_data *cfqd,
-						struct cfq_queue *cur_cfqq,
-						struct list_head *list)
-{
-	struct cfq_queue *cfqq;
-
-	list_for_each_entry(cfqq, list, cfq_list) {
-		if (cfqq == cur_cfqq || !cfq_cfqq_sync(cfqq))
-			continue;
-
-		BUG_ON(!cfqq->next_rq);
-
-		if (cfq_rq_close(cfqd, cfqq->next_rq))
-			return cfqq;
-	}
-
-	return NULL;
-}
-
-static int cfq_close_cooperator(struct cfq_data *cfqd,
-				struct cfq_queue *cur_cfqq)
+static int cfq_close_cooperator(struct cfq_data *cfq_data,
+				struct cfq_queue *cfqq)
 {
-	struct cfq_queue *cfqq;
-
-	if (!cfqd->busy_queues)
-		return 0;
-
 	/*
-	 * check cur_rr and same-prio rr_list for candidates
+	 * We should notice if some of the queues are cooperating, eg
+	 * working closely on the same area of the disk. In that case,
+	 * we can group them together and don't waste time idling.
 	 */
-	cfqq = __cfq_close_cooperator(cfqd, cur_cfqq, &cfqd->cur_rr);
-	if (cfqq)
-		return 1;
-
-	cfqq = __cfq_close_cooperator(cfqd, cur_cfqq, &cfqd->rr_list[cur_cfqq->ioprio]);
-	if (cfqq && (cfqq->rr_tick == cfqd->cur_rr_tick))
-		cfqq = NULL;
-
-	return cfqq != NULL;
+	return 0;
 }
 
 #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
@@ -974,7 +865,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 	 */
 	sl = cfqd->cfq_slice_idle;
 	if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
-		sl = min(sl, msecs_to_jiffies(2));
+		sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
 
 	mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
 }
@@ -1115,31 +1006,41 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 	return dispatched;
 }
 
-static int
-cfq_forced_dispatch_cfqqs(struct list_head *list)
+static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
+{
+	int dispatched = 0;
+
+	while (cfqq->next_rq) {
+		cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
+		dispatched++;
+	}
+
+	BUG_ON(!list_empty(&cfqq->fifo));
+	return dispatched;
+}
+
+static int cfq_forced_dispatch_cfqqs(struct list_head *list)
 {
 	struct cfq_queue *cfqq, *next;
 	int dispatched;
 
 	dispatched = 0;
-	list_for_each_entry_safe(cfqq, next, list, cfq_list) {
-		while (cfqq->next_rq) {
-			cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
-			dispatched++;
-		}
-		BUG_ON(!list_empty(&cfqq->fifo));
-	}
+	list_for_each_entry_safe(cfqq, next, list, cfq_list)
+		dispatched += __cfq_forced_dispatch_cfqq(cfqq);
 
 	return dispatched;
 }
 
-static int
-cfq_forced_dispatch(struct cfq_data *cfqd)
+static int cfq_forced_dispatch(struct cfq_data *cfqd)
 {
-	int i, dispatched = 0;
+	int dispatched = 0;
+	struct rb_node *n;
+
+	while ((n = rb_first(&cfqd->service_tree)) != NULL) {
+		struct cfq_queue *cfqq = rb_entry(n, struct cfq_queue, rb_node);
 
-	for (i = 0; i < CFQ_PRIO_LISTS; i++)
-		dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
+		dispatched += __cfq_forced_dispatch_cfqq(cfqq);
+	}
 
 	dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
 	dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
@@ -1151,8 +1052,7 @@ cfq_forced_dispatch(struct cfq_data *cfqd)
 	return dispatched;
 }
 
-static int
-cfq_dispatch_requests(request_queue_t *q, int force)
+static int cfq_dispatch_requests(request_queue_t *q, int force)
 {
 	struct cfq_data *cfqd = q->elevator->elevator_data;
 	struct cfq_queue *cfqq;
@@ -1222,7 +1122,6 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
 	/*
 	 * it's on the empty list and still hashed
 	 */
-	list_del(&cfqq->cfq_list);
 	hlist_del(&cfqq->cfq_hash);
 	kmem_cache_free(cfq_pool, cfqq);
 }
@@ -1391,8 +1290,6 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
 	 */
 	cfqq->org_ioprio = cfqq->ioprio;
 	cfqq->org_ioprio_class = cfqq->ioprio_class;
-
-	cfq_resort_rr_list(cfqq, 0);
 	cfq_clear_cfqq_prio_changed(cfqq);
 }
 
@@ -1478,6 +1375,7 @@ cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
 
 		INIT_HLIST_NODE(&cfqq->cfq_hash);
 		INIT_LIST_HEAD(&cfqq->cfq_list);
+		RB_CLEAR_NODE(&cfqq->rb_node);
 		INIT_LIST_HEAD(&cfqq->fifo);
 
 		cfqq->key = key;
@@ -1752,7 +1650,8 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	 * so we know that it will be selected next.
 	 */
 	BUG_ON(!cfq_cfqq_on_rr(cfqq));
-	list_move(&cfqq->cfq_list, &cfqd->cur_rr);
+	list_del_init(&cfqq->cfq_list);
+	list_add(&cfqq->cfq_list, &cfqd->cur_rr);
 
 	cfqq->slice_end = 0;
 	cfq_mark_cfqq_slice_new(cfqq);
@@ -1828,13 +1727,10 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
 	WARN_ON(!cfqq->dispatched);
 	cfqd->rq_in_driver--;
 	cfqq->dispatched--;
-	cfqq->service_last = now;
 
 	if (!cfq_class_idle(cfqq))
 		cfqd->last_end_request = now;
 
-	cfq_resort_rr_list(cfqq, 0);
-
 	if (sync)
 		RQ_CIC(rq)->last_end_request = now;
 
@@ -1863,9 +1759,6 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
  */
 static void cfq_prio_boost(struct cfq_queue *cfqq)
 {
-	const int ioprio_class = cfqq->ioprio_class;
-	const int ioprio = cfqq->ioprio;
-
 	if (has_fs_excl()) {
 		/*
 		 * boost idle prio on transactions that would lock out other
@@ -1884,12 +1777,6 @@ static void cfq_prio_boost(struct cfq_queue *cfqq)
 		if (cfqq->ioprio != cfqq->org_ioprio)
 			cfqq->ioprio = cfqq->org_ioprio;
 	}
-
-	/*
-	 * refile between round-robin lists if we moved the priority class
-	 */
-	if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio))
-		cfq_resort_rr_list(cfqq, 0);
 }
 
 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
@@ -2127,9 +2014,7 @@ static void *cfq_init_queue(request_queue_t *q)
 
 	memset(cfqd, 0, sizeof(*cfqd));
 
-	for (i = 0; i < CFQ_PRIO_LISTS; i++)
-		INIT_LIST_HEAD(&cfqd->rr_list[i]);
-
+	cfqd->service_tree = RB_ROOT;
 	INIT_LIST_HEAD(&cfqd->cur_rr);
 	INIT_LIST_HEAD(&cfqd->idle_rr);
 	INIT_LIST_HEAD(&cfqd->cic_list);