From 8fbb5a31f47828d00860ec205af69fde41722836 Mon Sep 17 00:00:00 2001
From: Tad <tad@spotco.us>
Date: Mon, 23 Mar 2015 09:58:02 -0400
Subject: [PATCH] Implement More I/O Schedulers

Pulled from the
following

https://github.com/AK-Kernel/AK-OnePone/commit/612b72e20419eb62f23d2b72e3d22ec210fe9e89

https://github.com/AK-Kernel/AK-OnePone/commit/b380a7e08b7f421783612be03cb7218b60e42c55

https://github.com/AK-Kernel/AK-OnePone/commit/ca19cf43a37392cac55e01c6294b41702ae215d1

https://github.com/AK-Kernel/AK-OnePone/commit/33111b2e5439936920e62dd7f4ca8473950196d3

https://github.com/AK-Kernel/AK-OnePone/commit/2c1d9b063a3bd0d51b0ead2edaa45aae64a8bfc9

https://github.com/AK-Kernel/AK-OnePone/commit/9cadd735cd466123824628c4dd8b973173c7eae2

https://github.com/AK-Kernel/AK-OnePone/commit/4c3b582977e41f0169f1d258d9064865e5a7c673

https://github.com/AK-Kernel/AK-OnePone/commit/4ce78414011bb8cba1d971623475c6a0b8fec897

https://github.com/AK-Kernel/AK-OnePone/commit/fadba4ee48e127a027b78a56f7cdbca8dc21e076
---
 arch/arm/configs/cyanogenmod_bacon_defconfig |   14 +-
 block/Kconfig.iosched                        |   98 +
 block/Makefile                               |    7 +
 block/bfq-cgroup.c                           |  908 ++++++
 block/bfq-ioc.c                              |   36 +
 block/bfq-iosched.c                          | 4208 ++++++++++++++++++++++++++
 block/bfq-sched.c                            | 1186 ++++++++
 block/bfq.h                                  |  809 +++++
 block/fiops-iosched.c                        |  753 +++++
 block/sio-iosched.c                          |  403 +++
 block/sioplus-iosched.c                      |  405 +++
 block/tripndroid-iosched.c                   |  261 ++
 block/vr-iosched.c                           |  432 +++
 block/zen-iosched.c                          |  277 ++
 include/linux/cgroup_subsys.h                |    6 +
 include/linux/elevator.h                     |    2 +
 16 files changed, 9800 insertions(+), 5 deletions(-)
 create mode 100644 block/bfq-cgroup.c
 create mode 100644 block/bfq-ioc.c
 create mode 100644 block/bfq-iosched.c
 create mode 100644 block/bfq-sched.c
 create mode 100644 block/bfq.h
 create mode 100644 block/fiops-iosched.c
 create mode 100644 block/sio-iosched.c
 create mode 100644 block/sioplus-iosched.c
 create mode 100644 block/tripndroid-iosched.c
 create mode 100644 block/vr-iosched.c
 create mode 100644 block/zen-iosched.c

diff --git a/arch/arm/configs/cyanogenmod_bacon_defconfig b/arch/arm/configs/cyanogenmod_bacon_defconfig
index 432364c..9c3ca28 100644
--- a/arch/arm/configs/cyanogenmod_bacon_defconfig
+++ b/arch/arm/configs/cyanogenmod_bacon_defconfig
@@ -223,11 +223,15 @@ CONFIG_IOSCHED_TEST=y
 CONFIG_IOSCHED_DEADLINE=y
 CONFIG_IOSCHED_ROW=y
 CONFIG_IOSCHED_CFQ=y
-# CONFIG_DEFAULT_DEADLINE is not set
-# CONFIG_DEFAULT_ROW is not set
-# CONFIG_DEFAULT_CFQ is not set
-CONFIG_DEFAULT_NOOP=y
-CONFIG_DEFAULT_IOSCHED="noop"
+CONFIG_IOSCHED_FIOPS=y
+CONFIG_IOSCHED_SIO=y
+CONFIG_IOSCHED_SIOPLUS=y
+CONFIG_IOSCHED_BFQ=y
+CONFIG_IOSCHED_ZEN=y
+CONFIG_IOSCHED_VR=y
+CONFIG_IOSCHED_TRIPNDROID=y
+CONFIG_DEFAULT_SIOPLUS=y
+CONFIG_DEFAULT_IOSCHED="SIOPLUS"
 # CONFIG_INLINE_SPIN_TRYLOCK is not set
 # CONFIG_INLINE_SPIN_TRYLOCK_BH is not set
 # CONFIG_INLINE_SPIN_LOCK is not set
diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 5fd98ea..20ab48f 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -65,6 +65,76 @@ config CFQ_GROUP_IOSCHED
 	---help---
 	  Enable group IO scheduling in CFQ.
 
+config IOSCHED_BFQ
+	tristate "BFQ I/O scheduler"
+	depends on EXPERIMENTAL
+	default n
+	---help---
+	  The BFQ I/O scheduler tries to distribute bandwidth among
+	  all processes according to their weights.
+	  It aims at distributing the bandwidth as desired, independently of
+	  the disk parameters and with any workload. It also tries to
+	  guarantee low latency to interactive and soft real-time
+	  applications.  If compiled built-in (saying Y here), BFQ can
+	  be configured to support hierarchical scheduling.
+
+config CGROUP_BFQIO
+	bool "BFQ hierarchical scheduling support"
+	depends on CGROUPS && IOSCHED_BFQ=y
+	default n
+	---help---
+	  Enable hierarchical scheduling in BFQ, using the cgroups
+	  filesystem interface.  The name of the subsystem will be
+	  bfqio.
+
+config IOSCHED_FIOPS
+	tristate "IOPS based I/O scheduler"
+	default y
+	---help---
+	  This is an IOPS based I/O scheduler. It will try to distribute
+          IOPS equally among all processes in the system. It's mainly for
+          Flash based storage.
+
+config IOSCHED_SIO
+	tristate "Simple I/O scheduler"
+	default y
+	---help---
+	  The Simple I/O scheduler is an extremely simple scheduler,
+	  based on noop and deadline, that relies on deadlines to
+	  ensure fairness. The algorithm does not do any sorting but
+	  basic merging, trying to keep a minimum overhead. It is aimed
+	  mainly for aleatory access devices (eg: flash devices).
+
+config IOSCHED_SIOPLUS
+	tristate "Simple I/O scheduler plus"
+	default y
+	---help---
+	  The Simple I/O scheduler is an extremely simple scheduler,
+	  based on noop and deadline, that relies on deadlines to
+	  ensure fairness. The algorithm does not do any sorting but
+	  basic merging, trying to keep a minimum overhead. It is aimed
+	  mainly for aleatory access devices (eg: flash devices).
+
+config IOSCHED_ZEN
+	tristate "Zen I/O scheduler"
+	default y
+	---help---
+	  FCFS, dispatches are back-inserted, deadlines ensure fairness.
+	  Should work best with devices where there is no travel delay.
+
+config IOSCHED_VR
+	tristate "V(R) I/O scheduler"
+	default y
+	---help---
+	  Requests are chosen according to SSTF with a penalty of rev_penalty
+	  for switching head direction.
+
+config IOSCHED_TRIPNDROID
+	tristate "Tripndroid"
+	default y
+	---help---
+	  The Trip N Droid scheduler
+
 choice
 	prompt "Default I/O scheduler"
 	default DEFAULT_CFQ
@@ -88,9 +158,30 @@ choice
 	config DEFAULT_CFQ
 		bool "CFQ" if IOSCHED_CFQ=y
 
+	config DEFAULT_BFQ
+		bool "BFQ" if IOSCHED_BFQ=y
+
+	config DEFAULT_FIOPS
+		bool "FIOPS" if IOSCHED_FIOPS=y
+
+	config DEFAULT_SIO
+		bool "SIO" if IOSCHED_SIO=y
+
+	config DEFAULT_SIOPLUS
+		bool "SIOPLUS" if IOSCHED_SIOPLUS=y
+
 	config DEFAULT_NOOP
 		bool "No-op"
 
+	config DEFAULT_ZEN
+		bool "ZEN" if IOSCHED_ZEN=y
+
+	config DEFAULT_VR
+		bool "VR" if IOSCHED_VR=y
+
+	config DEFAULT_TRIPNDROID
+		bool "TRIPNDROID" if IOSCHED_TRIPNDROID=y
+
 endchoice
 
 config DEFAULT_IOSCHED
@@ -98,7 +189,14 @@ config DEFAULT_IOSCHED
 	default "deadline" if DEFAULT_DEADLINE
 	default "row" if DEFAULT_ROW
 	default "cfq" if DEFAULT_CFQ
+	default "fiops" if DEFAULT_FIOPS
+	default "sio" if DEFAULT_SIO
+	default "sioplus" if DEFAULT_SIOPLUS
 	default "noop" if DEFAULT_NOOP
+	default "bfq" if DEFAULT_BFQ
+	default "zen" if DEFAULT_ZEN
+	default "vr" if DEFAULT_VR
+	default "tripndroid" if DEFAULT_TRIPNDROID
 
 endmenu
 
diff --git a/block/Makefile b/block/Makefile
index b5e6637..9e525b2 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -17,6 +17,13 @@ obj-$(CONFIG_IOSCHED_DEADLINE)	+= deadline-iosched.o
 obj-$(CONFIG_IOSCHED_ROW)	+= row-iosched.o
 obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
 obj-$(CONFIG_IOSCHED_TEST)	+= test-iosched.o
+obj-$(CONFIG_IOSCHED_FIOPS)	+= fiops-iosched.o
+obj-$(CONFIG_IOSCHED_SIO)       += sio-iosched.o
+obj-$(CONFIG_IOSCHED_SIOPLUS)   += sioplus-iosched.o
+obj-$(CONFIG_IOSCHED_BFQ)	+= bfq-iosched.o
+obj-$(CONFIG_IOSCHED_ZEN)       += zen-iosched.o
+obj-$(CONFIG_IOSCHED_VR)        += vr-iosched.o
+obj-$(CONFIG_IOSCHED_TRIPNDROID)	+= tripndroid-iosched.o
 
 obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
 obj-$(CONFIG_BLK_DEV_INTEGRITY)	+= blk-integrity.o
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
new file mode 100644
index 0000000..8399c92
--- /dev/null
+++ b/block/bfq-cgroup.c
@@ -0,0 +1,908 @@
+/*
+ * BFQ: CGROUPS support.
+ *
+ * Based on ideas and code from CFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
+ *		      Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Licensed under the GPL-2 as detailed in the accompanying COPYING.BFQ
+ * file.
+ */
+
+#ifdef CONFIG_CGROUP_BFQIO
+static struct bfqio_cgroup bfqio_root_cgroup = {
+	.weight = BFQ_DEFAULT_GRP_WEIGHT,
+	.ioprio = BFQ_DEFAULT_GRP_IOPRIO,
+	.ioprio_class = BFQ_DEFAULT_GRP_CLASS,
+};
+
+static inline void bfq_init_entity(struct bfq_entity *entity,
+				   struct bfq_group *bfqg)
+{
+	entity->weight = entity->new_weight;
+	entity->orig_weight = entity->new_weight;
+	entity->ioprio = entity->new_ioprio;
+	entity->ioprio_class = entity->new_ioprio_class;
+	entity->parent = bfqg->my_entity;
+	entity->sched_data = &bfqg->sched_data;
+}
+
+static struct bfqio_cgroup *cgroup_to_bfqio(struct cgroup *cgroup)
+{
+	return container_of(cgroup_subsys_state(cgroup, bfqio_subsys_id),
+			    struct bfqio_cgroup, css);
+}
+
+/*
+ * Search the bfq_group for bfqd into the hash table (by now only a list)
+ * of bgrp.  Must be called under rcu_read_lock().
+ */
+static struct bfq_group *bfqio_lookup_group(struct bfqio_cgroup *bgrp,
+					    struct bfq_data *bfqd)
+{
+	struct bfq_group *bfqg;
+	struct hlist_node *n;
+	void *key;
+
+	hlist_for_each_entry_rcu(bfqg, n, &bgrp->group_data, group_node) {
+		key = rcu_dereference(bfqg->bfqd);
+		if (key == bfqd)
+			return bfqg;
+	}
+
+	return NULL;
+}
+
+static inline void bfq_group_init_entity(struct bfqio_cgroup *bgrp,
+					 struct bfq_group *bfqg)
+{
+	struct bfq_entity *entity = &bfqg->entity;
+
+	/*
+	 * If the weight of the entity has never been set via the sysfs
+	 * interface, then bgrp->weight == 0. In this case we initialize
+	 * the weight from the current ioprio value. Otherwise, the group
+	 * weight, if set, has priority over the ioprio value.
+	 */
+	if (bgrp->weight == 0) {
+		entity->new_weight = bfq_ioprio_to_weight(bgrp->ioprio);
+		entity->new_ioprio = bgrp->ioprio;
+	} else {
+		if (bgrp->weight < BFQ_MIN_WEIGHT ||
+		    bgrp->weight > BFQ_MAX_WEIGHT) {
+			printk(KERN_CRIT "bfq_group_init_entity: "
+					 "bgrp->weight %d\n", bgrp->weight);
+			BUG();
+		}
+		entity->new_weight = bgrp->weight;
+		entity->new_ioprio = bfq_weight_to_ioprio(bgrp->weight);
+	}
+	entity->orig_weight = entity->weight = entity->new_weight;
+	entity->ioprio = entity->new_ioprio;
+	entity->ioprio_class = entity->new_ioprio_class = bgrp->ioprio_class;
+	entity->my_sched_data = &bfqg->sched_data;
+	bfqg->active_entities = 0;
+}
+
+static inline void bfq_group_set_parent(struct bfq_group *bfqg,
+					struct bfq_group *parent)
+{
+	struct bfq_entity *entity;
+
+	BUG_ON(parent == NULL);
+	BUG_ON(bfqg == NULL);
+
+	entity = &bfqg->entity;
+	entity->parent = parent->my_entity;
+	entity->sched_data = &parent->sched_data;
+}
+
+/**
+ * bfq_group_chain_alloc - allocate a chain of groups.
+ * @bfqd: queue descriptor.
+ * @cgroup: the leaf cgroup this chain starts from.
+ *
+ * Allocate a chain of groups starting from the one belonging to
+ * @cgroup up to the root cgroup.  Stop if a cgroup on the chain
+ * to the root has already an allocated group on @bfqd.
+ */
+static struct bfq_group *bfq_group_chain_alloc(struct bfq_data *bfqd,
+					       struct cgroup *cgroup)
+{
+	struct bfqio_cgroup *bgrp;
+	struct bfq_group *bfqg, *prev = NULL, *leaf = NULL;
+
+	for (; cgroup != NULL; cgroup = cgroup->parent) {
+		bgrp = cgroup_to_bfqio(cgroup);
+
+		bfqg = bfqio_lookup_group(bgrp, bfqd);
+		if (bfqg != NULL) {
+			/*
+			 * All the cgroups in the path from there to the
+			 * root must have a bfq_group for bfqd, so we don't
+			 * need any more allocations.
+			 */
+			break;
+		}
+
+		bfqg = kzalloc(sizeof(*bfqg), GFP_ATOMIC);
+		if (bfqg == NULL)
+			goto cleanup;
+
+		bfq_group_init_entity(bgrp, bfqg);
+		bfqg->my_entity = &bfqg->entity;
+
+		if (leaf == NULL) {
+			leaf = bfqg;
+			prev = leaf;
+		} else {
+			bfq_group_set_parent(prev, bfqg);
+			/*
+			 * Build a list of allocated nodes using the bfqd
+			 * filed, that is still unused and will be
+			 * initialized only after the node will be
+			 * connected.
+			 */
+			prev->bfqd = bfqg;
+			prev = bfqg;
+		}
+	}
+
+	return leaf;
+
+cleanup:
+	while (leaf != NULL) {
+		prev = leaf;
+		leaf = leaf->bfqd;
+		kfree(prev);
+	}
+
+	return NULL;
+}
+
+/**
+ * bfq_group_chain_link - link an allocated group chain to a cgroup
+ *                        hierarchy.
+ * @bfqd: the queue descriptor.
+ * @cgroup: the leaf cgroup to start from.
+ * @leaf: the leaf group (to be associated to @cgroup).
+ *
+ * Try to link a chain of groups to a cgroup hierarchy, connecting the
+ * nodes bottom-up, so we can be sure that when we find a cgroup in the
+ * hierarchy that already as a group associated to @bfqd all the nodes
+ * in the path to the root cgroup have one too.
+ *
+ * On locking: the queue lock protects the hierarchy (there is a hierarchy
+ * per device) while the bfqio_cgroup lock protects the list of groups
+ * belonging to the same cgroup.
+ */
+static void bfq_group_chain_link(struct bfq_data *bfqd, struct cgroup *cgroup,
+				 struct bfq_group *leaf)
+{
+	struct bfqio_cgroup *bgrp;
+	struct bfq_group *bfqg, *next, *prev = NULL;
+	unsigned long flags;
+
+	assert_spin_locked(bfqd->queue->queue_lock);
+
+	for (; cgroup != NULL && leaf != NULL; cgroup = cgroup->parent) {
+		bgrp = cgroup_to_bfqio(cgroup);
+		next = leaf->bfqd;
+
+		bfqg = bfqio_lookup_group(bgrp, bfqd);
+		BUG_ON(bfqg != NULL);
+
+		spin_lock_irqsave(&bgrp->lock, flags);
+
+		rcu_assign_pointer(leaf->bfqd, bfqd);
+		hlist_add_head_rcu(&leaf->group_node, &bgrp->group_data);
+		hlist_add_head(&leaf->bfqd_node, &bfqd->group_list);
+
+		spin_unlock_irqrestore(&bgrp->lock, flags);
+
+		prev = leaf;
+		leaf = next;
+	}
+
+	BUG_ON(cgroup == NULL && leaf != NULL);
+	if (cgroup != NULL && prev != NULL) {
+		bgrp = cgroup_to_bfqio(cgroup);
+		bfqg = bfqio_lookup_group(bgrp, bfqd);
+		bfq_group_set_parent(prev, bfqg);
+	}
+}
+
+/**
+ * bfq_find_alloc_group - return the group associated to @bfqd in @cgroup.
+ * @bfqd: queue descriptor.
+ * @cgroup: cgroup being searched for.
+ *
+ * Return a group associated to @bfqd in @cgroup, allocating one if
+ * necessary.  When a group is returned all the cgroups in the path
+ * to the root have a group associated to @bfqd.
+ *
+ * If the allocation fails, return the root group: this breaks guarantees
+ * but is a safe fallback.  If this loss becomes a problem it can be
+ * mitigated using the equivalent weight (given by the product of the
+ * weights of the groups in the path from @group to the root) in the
+ * root scheduler.
+ *
+ * We allocate all the missing nodes in the path from the leaf cgroup
+ * to the root and we connect the nodes only after all the allocations
+ * have been successful.
+ */
+static struct bfq_group *bfq_find_alloc_group(struct bfq_data *bfqd,
+					      struct cgroup *cgroup)
+{
+	struct bfqio_cgroup *bgrp = cgroup_to_bfqio(cgroup);
+	struct bfq_group *bfqg;
+
+	bfqg = bfqio_lookup_group(bgrp, bfqd);
+	if (bfqg != NULL)
+		return bfqg;
+
+	bfqg = bfq_group_chain_alloc(bfqd, cgroup);
+	if (bfqg != NULL)
+		bfq_group_chain_link(bfqd, cgroup, bfqg);
+	else
+		bfqg = bfqd->root_group;
+
+	return bfqg;
+}
+
+/**
+ * bfq_bfqq_move - migrate @bfqq to @bfqg.
+ * @bfqd: queue descriptor.
+ * @bfqq: the queue to move.
+ * @entity: @bfqq's entity.
+ * @bfqg: the group to move to.
+ *
+ * Move @bfqq to @bfqg, deactivating it from its old group and reactivating
+ * it on the new one.  Avoid putting the entity on the old group idle tree.
+ *
+ * Must be called under the queue lock; the cgroup owning @bfqg must
+ * not disappear (by now this just means that we are called under
+ * rcu_read_lock()).
+ */
+static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+			  struct bfq_entity *entity, struct bfq_group *bfqg)
+{
+	int busy, resume;
+
+	busy = bfq_bfqq_busy(bfqq);
+	resume = !RB_EMPTY_ROOT(&bfqq->sort_list);
+
+	BUG_ON(resume && !entity->on_st);
+	BUG_ON(busy && !resume && entity->on_st &&
+	       bfqq != bfqd->in_service_queue);
+
+	if (busy) {
+		BUG_ON(atomic_read(&bfqq->ref) < 2);
+
+		if (!resume)
+			bfq_del_bfqq_busy(bfqd, bfqq, 0);
+		else
+			bfq_deactivate_bfqq(bfqd, bfqq, 0);
+	} else if (entity->on_st)
+		bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
+
+	/*
+	 * Here we use a reference to bfqg.  We don't need a refcounter
+	 * as the cgroup reference will not be dropped, so that its
+	 * destroy() callback will not be invoked.
+	 */
+	entity->parent = bfqg->my_entity;
+	entity->sched_data = &bfqg->sched_data;
+
+	if (busy && resume)
+		bfq_activate_bfqq(bfqd, bfqq);
+
+	if (bfqd->in_service_queue == NULL && !bfqd->rq_in_driver)
+		bfq_schedule_dispatch(bfqd);
+}
+
+/**
+ * __bfq_bic_change_cgroup - move @bic to @cgroup.
+ * @bfqd: the queue descriptor.
+ * @bic: the bic to move.
+ * @cgroup: the cgroup to move to.
+ *
+ * Move bic to cgroup, assuming that bfqd->queue is locked; the caller
+ * has to make sure that the reference to cgroup is valid across the call.
+ *
+ * NOTE: an alternative approach might have been to store the current
+ * cgroup in bfqq and getting a reference to it, reducing the lookup
+ * time here, at the price of slightly more complex code.
+ */
+static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
+						 struct bfq_io_cq *bic,
+						 struct cgroup *cgroup)
+{
+	struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
+	struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
+	struct bfq_entity *entity;
+	struct bfq_group *bfqg;
+	struct bfqio_cgroup *bgrp;
+
+	bgrp = cgroup_to_bfqio(cgroup);
+
+	bfqg = bfq_find_alloc_group(bfqd, cgroup);
+	if (async_bfqq != NULL) {
+		entity = &async_bfqq->entity;
+
+		if (entity->sched_data != &bfqg->sched_data) {
+			bic_set_bfqq(bic, NULL, 0);
+			bfq_log_bfqq(bfqd, async_bfqq,
+				     "bic_change_group: %p %d",
+				     async_bfqq, atomic_read(&async_bfqq->ref));
+			bfq_put_queue(async_bfqq);
+		}
+	}
+
+	if (sync_bfqq != NULL) {
+		entity = &sync_bfqq->entity;
+		if (entity->sched_data != &bfqg->sched_data)
+			bfq_bfqq_move(bfqd, sync_bfqq, entity, bfqg);
+	}
+
+	return bfqg;
+}
+
+/**
+ * bfq_bic_change_cgroup - move @bic to @cgroup.
+ * @bic: the bic being migrated.
+ * @cgroup: the destination cgroup.
+ *
+ * When the task owning @bic is moved to @cgroup, @bic is immediately
+ * moved into its new parent group.
+ */
+static void bfq_bic_change_cgroup(struct bfq_io_cq *bic,
+				  struct cgroup *cgroup)
+{
+	struct bfq_data *bfqd;
+	unsigned long uninitialized_var(flags);
+
+	bfqd = bfq_get_bfqd_locked(&(bic->icq.q->elevator->elevator_data),
+				   &flags);
+	if (bfqd != NULL) {
+		__bfq_bic_change_cgroup(bfqd, bic, cgroup);
+		bfq_put_bfqd_unlock(bfqd, &flags);
+	}
+}
+
+/**
+ * bfq_bic_update_cgroup - update the cgroup of @bic.
+ * @bic: the @bic to update.
+ *
+ * Make sure that @bic is enqueued in the cgroup of the current task.
+ * We need this in addition to moving bics during the cgroup attach
+ * phase because the task owning @bic could be at its first disk
+ * access or we may end up in the root cgroup as the result of a
+ * memory allocation failure and here we try to move to the right
+ * group.
+ *
+ * Must be called under the queue lock.  It is safe to use the returned
+ * value even after the rcu_read_unlock() as the migration/destruction
+ * paths act under the queue lock too.  IOW it is impossible to race with
+ * group migration/destruction and end up with an invalid group as:
+ *   a) here cgroup has not yet been destroyed, nor its destroy callback
+ *      has started execution, as current holds a reference to it,
+ *   b) if it is destroyed after rcu_read_unlock() [after current is
+ *      migrated to a different cgroup] its attach() callback will have
+ *      taken care of remove all the references to the old cgroup data.
+ */
+static struct bfq_group *bfq_bic_update_cgroup(struct bfq_io_cq *bic)
+{
+	struct bfq_data *bfqd = bic_to_bfqd(bic);
+	struct bfq_group *bfqg;
+	struct cgroup *cgroup;
+
+	BUG_ON(bfqd == NULL);
+
+	rcu_read_lock();
+	cgroup = task_cgroup(current, bfqio_subsys_id);
+	bfqg = __bfq_bic_change_cgroup(bfqd, bic, cgroup);
+	rcu_read_unlock();
+
+	return bfqg;
+}
+
+/**
+ * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
+ * @st: the service tree being flushed.
+ */
+static inline void bfq_flush_idle_tree(struct bfq_service_tree *st)
+{
+	struct bfq_entity *entity = st->first_idle;
+
+	for (; entity != NULL; entity = st->first_idle)
+		__bfq_deactivate_entity(entity, 0);
+}
+
+/**
+ * bfq_reparent_leaf_entity - move leaf entity to the root_group.
+ * @bfqd: the device data structure with the root group.
+ * @entity: the entity to move.
+ */
+static inline void bfq_reparent_leaf_entity(struct bfq_data *bfqd,
+					    struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+
+	BUG_ON(bfqq == NULL);
+	bfq_bfqq_move(bfqd, bfqq, entity, bfqd->root_group);
+	return;
+}
+
+/**
+ * bfq_reparent_active_entities - move to the root group all active
+ *                                entities.
+ * @bfqd: the device data structure with the root group.
+ * @bfqg: the group to move from.
+ * @st: the service tree with the entities.
+ *
+ * Needs queue_lock to be taken and reference to be valid over the call.
+ */
+static inline void bfq_reparent_active_entities(struct bfq_data *bfqd,
+						struct bfq_group *bfqg,
+						struct bfq_service_tree *st)
+{
+	struct rb_root *active = &st->active;
+	struct bfq_entity *entity = NULL;
+
+	if (!RB_EMPTY_ROOT(&st->active))
+		entity = bfq_entity_of(rb_first(active));
+
+	for (; entity != NULL; entity = bfq_entity_of(rb_first(active)))
+		bfq_reparent_leaf_entity(bfqd, entity);
+
+	if (bfqg->sched_data.in_service_entity != NULL)
+		bfq_reparent_leaf_entity(bfqd,
+			bfqg->sched_data.in_service_entity);
+
+	return;
+}
+
+/**
+ * bfq_destroy_group - destroy @bfqg.
+ * @bgrp: the bfqio_cgroup containing @bfqg.
+ * @bfqg: the group being destroyed.
+ *
+ * Destroy @bfqg, making sure that it is not referenced from its parent.
+ */
+static void bfq_destroy_group(struct bfqio_cgroup *bgrp, struct bfq_group *bfqg)
+{
+	struct bfq_data *bfqd;
+	struct bfq_service_tree *st;
+	struct bfq_entity *entity = bfqg->my_entity;
+	unsigned long uninitialized_var(flags);
+	int i;
+
+	hlist_del(&bfqg->group_node);
+
+	/*
+	 * Empty all service_trees belonging to this group before
+	 * deactivating the group itself.
+	 */
+	for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
+		st = bfqg->sched_data.service_tree + i;
+
+		/*
+		 * The idle tree may still contain bfq_queues belonging
+		 * to exited task because they never migrated to a different
+		 * cgroup from the one being destroyed now.  No one else
+		 * can access them so it's safe to act without any lock.
+		 */
+		bfq_flush_idle_tree(st);
+
+		/*
+		 * It may happen that some queues are still active
+		 * (busy) upon group destruction (if the corresponding
+		 * processes have been forced to terminate). We move
+		 * all the leaf entities corresponding to these queues
+		 * to the root_group.
+		 * Also, it may happen that the group has an entity
+		 * in service, which is disconnected from the active
+		 * tree: it must be moved, too.
+		 * There is no need to put the sync queues, as the
+		 * scheduler has taken no reference.
+		 */
+		bfqd = bfq_get_bfqd_locked(&bfqg->bfqd, &flags);
+		if (bfqd != NULL) {
+			bfq_reparent_active_entities(bfqd, bfqg, st);
+			bfq_put_bfqd_unlock(bfqd, &flags);
+		}
+		BUG_ON(!RB_EMPTY_ROOT(&st->active));
+		BUG_ON(!RB_EMPTY_ROOT(&st->idle));
+	}
+	BUG_ON(bfqg->sched_data.next_in_service != NULL);
+	BUG_ON(bfqg->sched_data.in_service_entity != NULL);
+
+	/*
+	 * We may race with device destruction, take extra care when
+	 * dereferencing bfqg->bfqd.
+	 */
+	bfqd = bfq_get_bfqd_locked(&bfqg->bfqd, &flags);
+	if (bfqd != NULL) {
+		hlist_del(&bfqg->bfqd_node);
+		__bfq_deactivate_entity(entity, 0);
+		bfq_put_async_queues(bfqd, bfqg);
+		bfq_put_bfqd_unlock(bfqd, &flags);
+	}
+	BUG_ON(entity->tree != NULL);
+
+	/*
+	 * No need to defer the kfree() to the end of the RCU grace
+	 * period: we are called from the destroy() callback of our
+	 * cgroup, so we can be sure that no one is a) still using
+	 * this cgroup or b) doing lookups in it.
+	 */
+	kfree(bfqg);
+}
+
+static void bfq_end_wr_async(struct bfq_data *bfqd)
+{
+	struct hlist_node *pos, *n;
+	struct bfq_group *bfqg;
+
+	hlist_for_each_entry_safe(bfqg, pos, n, &bfqd->group_list, bfqd_node)
+		bfq_end_wr_async_queues(bfqd, bfqg);
+	bfq_end_wr_async_queues(bfqd, bfqd->root_group);
+}
+
+/**
+ * bfq_disconnect_groups - disconnect @bfqd from all its groups.
+ * @bfqd: the device descriptor being exited.
+ *
+ * When the device exits we just make sure that no lookup can return
+ * the now unused group structures.  They will be deallocated on cgroup
+ * destruction.
+ */
+static void bfq_disconnect_groups(struct bfq_data *bfqd)
+{
+	struct hlist_node *pos, *n;
+	struct bfq_group *bfqg;
+
+	bfq_log(bfqd, "disconnect_groups beginning");
+	hlist_for_each_entry_safe(bfqg, pos, n, &bfqd->group_list, bfqd_node) {
+		hlist_del(&bfqg->bfqd_node);
+
+		__bfq_deactivate_entity(bfqg->my_entity, 0);
+
+		/*
+		 * Don't remove from the group hash, just set an
+		 * invalid key.  No lookups can race with the
+		 * assignment as bfqd is being destroyed; this
+		 * implies also that new elements cannot be added
+		 * to the list.
+		 */
+		rcu_assign_pointer(bfqg->bfqd, NULL);
+
+		bfq_log(bfqd, "disconnect_groups: put async for group %p",
+			bfqg);
+		bfq_put_async_queues(bfqd, bfqg);
+	}
+}
+
+static inline void bfq_free_root_group(struct bfq_data *bfqd)
+{
+	struct bfqio_cgroup *bgrp = &bfqio_root_cgroup;
+	struct bfq_group *bfqg = bfqd->root_group;
+
+	bfq_put_async_queues(bfqd, bfqg);
+
+	spin_lock_irq(&bgrp->lock);
+	hlist_del_rcu(&bfqg->group_node);
+	spin_unlock_irq(&bgrp->lock);
+
+	/*
+	 * No need to synchronize_rcu() here: since the device is gone
+	 * there cannot be any read-side access to its root_group.
+	 */
+	kfree(bfqg);
+}
+
+static struct bfq_group *bfq_alloc_root_group(struct bfq_data *bfqd, int node)
+{
+	struct bfq_group *bfqg;
+	struct bfqio_cgroup *bgrp;
+	int i;
+
+	bfqg = kzalloc_node(sizeof(*bfqg), GFP_KERNEL, node);
+	if (bfqg == NULL)
+		return NULL;
+
+	bfqg->entity.parent = NULL;
+	for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
+		bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
+
+	bgrp = &bfqio_root_cgroup;
+	spin_lock_irq(&bgrp->lock);
+	rcu_assign_pointer(bfqg->bfqd, bfqd);
+	hlist_add_head_rcu(&bfqg->group_node, &bgrp->group_data);
+	spin_unlock_irq(&bgrp->lock);
+
+	return bfqg;
+}
+
+#define SHOW_FUNCTION(__VAR)						\
+static u64 bfqio_cgroup_##__VAR##_read(struct cgroup *cgroup,		\
+				       struct cftype *cftype)		\
+{									\
+	struct bfqio_cgroup *bgrp;					\
+	u64 ret;							\
+									\
+	if (!cgroup_lock_live_group(cgroup))				\
+		return -ENODEV;						\
+									\
+	bgrp = cgroup_to_bfqio(cgroup);					\
+	spin_lock_irq(&bgrp->lock);					\
+	ret = bgrp->__VAR;						\
+	spin_unlock_irq(&bgrp->lock);					\
+									\
+	cgroup_unlock();						\
+									\
+	return ret;							\
+}
+
+SHOW_FUNCTION(weight);
+SHOW_FUNCTION(ioprio);
+SHOW_FUNCTION(ioprio_class);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__VAR, __MIN, __MAX)				\
+static int bfqio_cgroup_##__VAR##_write(struct cgroup *cgroup,		\
+					struct cftype *cftype,		\
+					u64 val)			\
+{									\
+	struct bfqio_cgroup *bgrp;					\
+	struct bfq_group *bfqg;						\
+	struct hlist_node *n;						\
+									\
+	if (val < (__MIN) || val > (__MAX))				\
+		return -EINVAL;						\
+									\
+	if (!cgroup_lock_live_group(cgroup))				\
+		return -ENODEV;						\
+									\
+	bgrp = cgroup_to_bfqio(cgroup);					\
+									\
+	spin_lock_irq(&bgrp->lock);					\
+	bgrp->__VAR = (unsigned short)val;				\
+	hlist_for_each_entry(bfqg, n, &bgrp->group_data, group_node) {	\
+		/*                                                      \
+		 * Setting the ioprio_changed flag of the entity        \
+		 * to 1 with new_##__VAR == ##__VAR would re-set        \
+		 * the value of the weight to its ioprio mapping.       \
+		 * Set the flag only if necessary.			\
+		 */							\
+		if ((unsigned short)val != bfqg->entity.new_##__VAR) {  \
+			bfqg->entity.new_##__VAR = (unsigned short)val; \
+			/*						\
+			 * Make sure that the above new value has been	\
+			 * stored in bfqg->entity.new_##__VAR before	\
+			 * setting the ioprio_changed flag. In fact,	\
+			 * this flag may be read asynchronously (in	\
+			 * critical sections protected by a different	\
+			 * lock than that held here), and finding this	\
+			 * flag set may cause the execution of the code	\
+			 * for updating parameters whose value may	\
+			 * depend also on bfqg->entity.new_##__VAR (in	\
+			 * __bfq_entity_update_weight_prio).		\
+			 * This barrier makes sure that the new value	\
+			 * of bfqg->entity.new_##__VAR is correctly	\
+			 * seen in that code.				\
+			 */						\
+			smp_wmb();                                      \
+			bfqg->entity.ioprio_changed = 1;                \
+		}                                                       \
+	}								\
+	spin_unlock_irq(&bgrp->lock);					\
+									\
+	cgroup_unlock();						\
+									\
+	return 0;							\
+}
+
+STORE_FUNCTION(weight, BFQ_MIN_WEIGHT, BFQ_MAX_WEIGHT);
+STORE_FUNCTION(ioprio, 0, IOPRIO_BE_NR - 1);
+STORE_FUNCTION(ioprio_class, IOPRIO_CLASS_RT, IOPRIO_CLASS_IDLE);
+#undef STORE_FUNCTION
+
+static struct cftype bfqio_files[] = {
+	{
+		.name = "weight",
+		.read_u64 = bfqio_cgroup_weight_read,
+		.write_u64 = bfqio_cgroup_weight_write,
+	},
+	{
+		.name = "ioprio",
+		.read_u64 = bfqio_cgroup_ioprio_read,
+		.write_u64 = bfqio_cgroup_ioprio_write,
+	},
+	{
+		.name = "ioprio_class",
+		.read_u64 = bfqio_cgroup_ioprio_class_read,
+		.write_u64 = bfqio_cgroup_ioprio_class_write,
+	},
+};
+
+static int bfqio_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
+{
+	return cgroup_add_files(cgroup, subsys, bfqio_files,
+				ARRAY_SIZE(bfqio_files));
+}
+
+static struct cgroup_subsys_state *bfqio_create(struct cgroup *cgroup)
+{
+	struct bfqio_cgroup *bgrp;
+
+	if (cgroup->parent != NULL) {
+		bgrp = kzalloc(sizeof(*bgrp), GFP_KERNEL);
+		if (bgrp == NULL)
+			return ERR_PTR(-ENOMEM);
+	} else
+		bgrp = &bfqio_root_cgroup;
+
+	spin_lock_init(&bgrp->lock);
+	INIT_HLIST_HEAD(&bgrp->group_data);
+	bgrp->ioprio = BFQ_DEFAULT_GRP_IOPRIO;
+	bgrp->ioprio_class = BFQ_DEFAULT_GRP_CLASS;
+
+	return &bgrp->css;
+}
+
+/*
+ * We cannot support shared io contexts, as we have no means to support
+ * two tasks with the same ioc in two different groups without major rework
+ * of the main bic/bfqq data structures.  By now we allow a task to change
+ * its cgroup only if it's the only owner of its ioc; the drawback of this
+ * behavior is that a group containing a task that forked using CLONE_IO
+ * will not be destroyed until the tasks sharing the ioc die.
+ */
+static int bfqio_can_attach(struct cgroup *cgroup, struct cgroup_taskset *tset)
+{
+	struct task_struct *task;
+	struct io_context *ioc;
+	int ret = 0;
+
+	cgroup_taskset_for_each(task, cgroup, tset) {
+		/* task_lock() is needed to avoid races with exit_io_context() */
+		task_lock(task);
+		ioc = task->io_context;
+		if (ioc != NULL && atomic_read(&ioc->nr_tasks) > 1)
+			/*
+			 * ioc == NULL means that the task is either too
+			 * young or exiting: if it has still no ioc the
+			 * ioc can't be shared, if the task is exiting the
+			 * attach will fail anyway, no matter what we
+			 * return here.
+			 */
+			ret = -EINVAL;
+		task_unlock(task);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+static void bfqio_attach(struct cgroup *cgroup, struct cgroup_taskset *tset)
+{
+	struct task_struct *task;
+	struct io_context *ioc;
+	struct io_cq *icq;
+	struct hlist_node *n;
+
+	/*
+	 * IMPORTANT NOTE: The move of more than one process at a time to a
+	 * new group has not yet been tested.
+	 */
+	cgroup_taskset_for_each(task, cgroup, tset) {
+		ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
+		if (ioc) {
+			/*
+			 * Handle cgroup change here.
+			 */
+			rcu_read_lock();
+			hlist_for_each_entry_rcu(icq, n, &ioc->icq_list, ioc_node)
+				if (!strncmp(
+					icq->q->elevator->type->elevator_name,
+					"bfq", ELV_NAME_MAX))
+					bfq_bic_change_cgroup(icq_to_bic(icq),
+							      cgroup);
+			rcu_read_unlock();
+			put_io_context(ioc);
+		}
+	}
+}
+
+static void bfqio_destroy(struct cgroup *cgroup)
+{
+	struct bfqio_cgroup *bgrp = cgroup_to_bfqio(cgroup);
+	struct hlist_node *n, *tmp;
+	struct bfq_group *bfqg;
+
+	/*
+	 * Since we are destroying the cgroup, there are no more tasks
+	 * referencing it, and all the RCU grace periods that may have
+	 * referenced it are ended (as the destruction of the parent
+	 * cgroup is RCU-safe); bgrp->group_data will not be accessed by
+	 * anything else and we don't need any synchronization.
+	 */
+	hlist_for_each_entry_safe(bfqg, n, tmp, &bgrp->group_data, group_node)
+		bfq_destroy_group(bgrp, bfqg);
+
+	BUG_ON(!hlist_empty(&bgrp->group_data));
+
+	kfree(bgrp);
+}
+
+struct cgroup_subsys bfqio_subsys = {
+	.name = "bfqio",
+	.create = bfqio_create,
+	.can_attach = bfqio_can_attach,
+	.attach = bfqio_attach,
+	.destroy = bfqio_destroy,
+	.populate = bfqio_populate,
+	.subsys_id = bfqio_subsys_id,
+};
+#else
+static inline void bfq_init_entity(struct bfq_entity *entity,
+				   struct bfq_group *bfqg)
+{
+	entity->weight = entity->new_weight;
+	entity->orig_weight = entity->new_weight;
+	entity->ioprio = entity->new_ioprio;
+	entity->ioprio_class = entity->new_ioprio_class;
+	entity->sched_data = &bfqg->sched_data;
+}
+
+static inline struct bfq_group *
+bfq_bic_update_cgroup(struct bfq_io_cq *bic)
+{
+	struct bfq_data *bfqd = bic_to_bfqd(bic);
+	return bfqd->root_group;
+}
+
+static inline void bfq_bfqq_move(struct bfq_data *bfqd,
+				 struct bfq_queue *bfqq,
+				 struct bfq_entity *entity,
+				 struct bfq_group *bfqg)
+{
+}
+
+static void bfq_end_wr_async(struct bfq_data *bfqd)
+{
+	bfq_end_wr_async_queues(bfqd, bfqd->root_group);
+}
+
+static inline void bfq_disconnect_groups(struct bfq_data *bfqd)
+{
+	bfq_put_async_queues(bfqd, bfqd->root_group);
+}
+
+static inline void bfq_free_root_group(struct bfq_data *bfqd)
+{
+	kfree(bfqd->root_group);
+}
+
+static struct bfq_group *bfq_alloc_root_group(struct bfq_data *bfqd, int node)
+{
+	struct bfq_group *bfqg;
+	int i;
+
+	bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node);
+	if (bfqg == NULL)
+		return NULL;
+
+	for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
+		bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
+
+	return bfqg;
+}
+#endif
diff --git a/block/bfq-ioc.c b/block/bfq-ioc.c
new file mode 100644
index 0000000..7f6b000
--- /dev/null
+++ b/block/bfq-ioc.c
@@ -0,0 +1,36 @@
+/*
+ * BFQ: I/O context handling.
+ *
+ * Based on ideas and code from CFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
+ *		      Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
+ */
+
+/**
+ * icq_to_bic - convert iocontext queue structure to bfq_io_cq.
+ * @icq: the iocontext queue.
+ */
+static inline struct bfq_io_cq *icq_to_bic(struct io_cq *icq)
+{
+	/* bic->icq is the first member, %NULL will convert to %NULL */
+	return container_of(icq, struct bfq_io_cq, icq);
+}
+
+/**
+ * bfq_bic_lookup - search into @ioc a bic associated to @bfqd.
+ * @bfqd: the lookup key.
+ * @ioc: the io_context of the process doing I/O.
+ *
+ * Queue lock must be held.
+ */
+static inline struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd,
+					       struct io_context *ioc)
+{
+	if (ioc)
+		return icq_to_bic(ioc_lookup_icq(ioc, bfqd->queue));
+	return NULL;
+}
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
new file mode 100644
index 0000000..152992b
--- /dev/null
+++ b/block/bfq-iosched.c
@@ -0,0 +1,4208 @@
+/*
+ * Budget Fair Queueing (BFQ) disk scheduler.
+ *
+ * Based on ideas and code from CFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
+ *		      Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Licensed under the GPL-2 as detailed in the accompanying COPYING.BFQ
+ * file.
+ *
+ * BFQ is a proportional-share storage-I/O scheduling algorithm based on
+ * the slice-by-slice service scheme of CFQ. But BFQ assigns budgets,
+ * measured in number of sectors, to processes instead of time slices. The
+ * device is not granted to the in-service process for a given time slice,
+ * but until it has exhausted its assigned budget. This change from the time
+ * to the service domain allows BFQ to distribute the device throughput
+ * among processes as desired, without any distortion due to ZBR, workload
+ * fluctuations or other factors. BFQ uses an ad hoc internal scheduler,
+ * called B-WF2Q+, to schedule processes according to their budgets. More
+ * precisely, BFQ schedules queues associated to processes. Thanks to the
+ * accurate policy of B-WF2Q+, BFQ can afford to assign high budgets to
+ * I/O-bound processes issuing sequential requests (to boost the
+ * throughput), and yet guarantee a low latency to interactive and soft
+ * real-time applications.
+ *
+ * BFQ is described in [1], where also a reference to the initial, more
+ * theoretical paper on BFQ can be found. The interested reader can find
+ * in the latter paper full details on the main algorithm, as well as
+ * formulas of the guarantees and formal proofs of all the properties.
+ * With respect to the version of BFQ presented in these papers, this
+ * implementation adds a few more heuristics, such as the one that
+ * guarantees a low latency to soft real-time applications, and a
+ * hierarchical extension based on H-WF2Q+.
+ *
+ * B-WF2Q+ is based on WF2Q+, that is described in [2], together with
+ * H-WF2Q+, while the augmented tree used to implement B-WF2Q+ with O(log N)
+ * complexity derives from the one introduced with EEVDF in [3].
+ *
+ * [1] P. Valente and M. Andreolini, ``Improving Application Responsiveness
+ *     with the BFQ Disk I/O Scheduler'',
+ *     Proceedings of the 5th Annual International Systems and Storage
+ *     Conference (SYSTOR '12), June 2012.
+ *
+ * http://algogroup.unimo.it/people/paolo/disk_sched/bf1-v1-suite-results.pdf
+ *
+ * [2] Jon C.R. Bennett and H. Zhang, ``Hierarchical Packet Fair Queueing
+ *     Algorithms,'' IEEE/ACM Transactions on Networking, 5(5):675-689,
+ *     Oct 1997.
+ *
+ * http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz
+ *
+ * [3] I. Stoica and H. Abdel-Wahab, ``Earliest Eligible Virtual Deadline
+ *     First: A Flexible and Accurate Mechanism for Proportional Share
+ *     Resource Allocation,'' technical report.
+ *
+ * http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf
+ */
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/cgroup.h>
+#include <linux/elevator.h>
+#include <linux/jiffies.h>
+#include <linux/rbtree.h>
+#include <linux/ioprio.h>
+#include "bfq.h"
+#include "blk.h"
+
+/* Max number of dispatches in one round of service. */
+static const int bfq_quantum = 4;
+
+/* Expiration time of sync (0) and async (1) requests, in jiffies. */
+static const int bfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
+
+/* Maximum backwards seek, in KiB. */
+static const int bfq_back_max = 16 * 1024;
+
+/* Penalty of a backwards seek, in number of sectors. */
+static const int bfq_back_penalty = 2;
+
+/* Idling period duration, in jiffies. */
+static int bfq_slice_idle = HZ / 125;
+
+/* Default maximum budget values, in sectors and number of requests. */
+static const int bfq_default_max_budget = 16 * 1024;
+static const int bfq_max_budget_async_rq = 4;
+
+/*
+ * Async to sync throughput distribution is controlled as follows:
+ * when an async request is served, the entity is charged the number
+ * of sectors of the request, multiplied by the factor below
+ */
+static const int bfq_async_charge_factor = 10;
+
+/* Default timeout values, in jiffies, approximating CFQ defaults. */
+static const int bfq_timeout_sync = HZ / 8;
+static int bfq_timeout_async = HZ / 25;
+
+struct kmem_cache *bfq_pool;
+
+/* Below this threshold (in ms), we consider thinktime immediate. */
+#define BFQ_MIN_TT		2
+
+/* hw_tag detection: parallel requests threshold and min samples needed. */
+#define BFQ_HW_QUEUE_THRESHOLD	4
+#define BFQ_HW_QUEUE_SAMPLES	32
+
+#define BFQQ_SEEK_THR	 (sector_t)(8 * 1024)
+#define BFQQ_SEEKY(bfqq) ((bfqq)->seek_mean > BFQQ_SEEK_THR)
+
+/* Min samples used for peak rate estimation (for autotuning). */
+#define BFQ_PEAK_RATE_SAMPLES	32
+
+/* Shift used for peak rate fixed precision calculations. */
+#define BFQ_RATE_SHIFT		16
+
+/*
+ * By default, BFQ computes the duration of the weight raising for
+ * interactive applications automatically, using the following formula:
+ * duration = (R / r) * T, where r is the peak rate of the device, and
+ * R and T are two reference parameters.
+ * In particular, R is the peak rate of the reference device (see below),
+ * and T is a reference time: given the systems that are likely to be
+ * installed on the reference device according to its speed class, T is
+ * about the maximum time needed, under BFQ and while reading two files in
+ * parallel, to load typical large applications on these systems.
+ * In practice, the slower/faster the device at hand is, the more/less it
+ * takes to load applications with respect to the reference device.
+ * Accordingly, the longer/shorter BFQ grants weight raising to interactive
+ * applications.
+ *
+ * BFQ uses four different reference pairs (R, T), depending on:
+ * . whether the device is rotational or non-rotational;
+ * . whether the device is slow, such as old or portable HDDs, as well as
+ *   SD cards, or fast, such as newer HDDs and SSDs.
+ *
+ * The device's speed class is dynamically (re)detected in
+ * bfq_update_peak_rate() every time the estimated peak rate is updated.
+ *
+ * In the following definitions, R_slow[0]/R_fast[0] and T_slow[0]/T_fast[0]
+ * are the reference values for a slow/fast rotational device, whereas
+ * R_slow[1]/R_fast[1] and T_slow[1]/T_fast[1] are the reference values for
+ * a slow/fast non-rotational device. Finally, device_speed_thresh are the
+ * thresholds used to switch between speed classes.
+ * Both the reference peak rates and the thresholds are measured in
+ * sectors/usec, left-shifted by BFQ_RATE_SHIFT.
+ */
+static int R_slow[2] = {1536, 10752};
+static int R_fast[2] = {17415, 34791};
+/*
+ * To improve readability, a conversion function is used to initialize the
+ * following arrays, which entails that they can be initialized only in a
+ * function.
+ */
+static int T_slow[2];
+static int T_fast[2];
+static int device_speed_thresh[2];
+
+#define BFQ_SERVICE_TREE_INIT	((struct bfq_service_tree)		\
+				{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
+
+#define RQ_BIC(rq)		((struct bfq_io_cq *) (rq)->elv.priv[0])
+#define RQ_BFQQ(rq)		((rq)->elv.priv[1])
+
+static inline void bfq_schedule_dispatch(struct bfq_data *bfqd);
+
+#include "bfq-ioc.c"
+#include "bfq-sched.c"
+#include "bfq-cgroup.c"
+
+#define bfq_class_idle(bfqq)	((bfqq)->entity.ioprio_class ==\
+				 IOPRIO_CLASS_IDLE)
+#define bfq_class_rt(bfqq)	((bfqq)->entity.ioprio_class ==\
+				 IOPRIO_CLASS_RT)
+
+#define bfq_sample_valid(samples)	((samples) > 80)
+
+/*
+ * We regard a request as SYNC, if either it's a read or has the SYNC bit
+ * set (in which case it could also be a direct WRITE).
+ */
+static inline int bfq_bio_sync(struct bio *bio)
+{
+	if (bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC))
+		return 1;
+
+	return 0;
+}
+
+/*
+ * Scheduler run of queue, if there are requests pending and no one in the
+ * driver that will restart queueing.
+ */
+static inline void bfq_schedule_dispatch(struct bfq_data *bfqd)
+{
+	if (bfqd->queued != 0) {
+		bfq_log(bfqd, "schedule dispatch");
+		kblockd_schedule_work(bfqd->queue, &bfqd->unplug_work);
+	}
+}
+
+/*
+ * Lifted from AS - choose which of rq1 and rq2 that is best served now.
+ * We choose the request that is closesr to the head right now.  Distance
+ * behind the head is penalized and only allowed to a certain extent.
+ */
+static struct request *bfq_choose_req(struct bfq_data *bfqd,
+				      struct request *rq1,
+				      struct request *rq2,
+				      sector_t last)
+{
+	sector_t s1, s2, d1 = 0, d2 = 0;
+	unsigned long back_max;
+#define BFQ_RQ1_WRAP	0x01 /* request 1 wraps */
+#define BFQ_RQ2_WRAP	0x02 /* request 2 wraps */
+	unsigned wrap = 0; /* bit mask: requests behind the disk head? */
+
+	if (rq1 == NULL || rq1 == rq2)
+		return rq2;
+	if (rq2 == NULL)
+		return rq1;
+
+	if (rq_is_sync(rq1) && !rq_is_sync(rq2))
+		return rq1;
+	else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
+		return rq2;
+	if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
+		return rq1;
+	else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META))
+		return rq2;
+
+	s1 = blk_rq_pos(rq1);
+	s2 = blk_rq_pos(rq2);
+
+	/*
+	 * By definition, 1KiB is 2 sectors.
+	 */
+	back_max = bfqd->bfq_back_max * 2;
+
+	/*
+	 * Strict one way elevator _except_ in the case where we allow
+	 * short backward seeks which are biased as twice the cost of a
+	 * similar forward seek.
+	 */
+	if (s1 >= last)
+		d1 = s1 - last;
+	else if (s1 + back_max >= last)
+		d1 = (last - s1) * bfqd->bfq_back_penalty;
+	else
+		wrap |= BFQ_RQ1_WRAP;
+
+	if (s2 >= last)
+		d2 = s2 - last;
+	else if (s2 + back_max >= last)
+		d2 = (last - s2) * bfqd->bfq_back_penalty;
+	else
+		wrap |= BFQ_RQ2_WRAP;
+
+	/* Found required data */
+
+	/*
+	 * By doing switch() on the bit mask "wrap" we avoid having to
+	 * check two variables for all permutations: --> faster!
+	 */
+	switch (wrap) {
+	case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
+		if (d1 < d2)
+			return rq1;
+		else if (d2 < d1)
+			return rq2;
+		else {
+			if (s1 >= s2)
+				return rq1;
+			else
+				return rq2;
+		}
+
+	case BFQ_RQ2_WRAP:
+		return rq1;
+	case BFQ_RQ1_WRAP:
+		return rq2;
+	case (BFQ_RQ1_WRAP|BFQ_RQ2_WRAP): /* both rqs wrapped */
+	default:
+		/*
+		 * Since both rqs are wrapped,
+		 * start with the one that's further behind head
+		 * (--> only *one* back seek required),
+		 * since back seek takes more time than forward.
+		 */
+		if (s1 <= s2)
+			return rq1;
+		else
+			return rq2;
+	}
+}
+
+static struct bfq_queue *
+bfq_rq_pos_tree_lookup(struct bfq_data *bfqd, struct rb_root *root,
+		     sector_t sector, struct rb_node **ret_parent,
+		     struct rb_node ***rb_link)
+{
+	struct rb_node **p, *parent;
+	struct bfq_queue *bfqq = NULL;
+
+	parent = NULL;
+	p = &root->rb_node;
+	while (*p) {
+		struct rb_node **n;
+
+		parent = *p;
+		bfqq = rb_entry(parent, struct bfq_queue, pos_node);
+
+		/*
+		 * Sort strictly based on sector. Smallest to the left,
+		 * largest to the right.
+		 */
+		if (sector > blk_rq_pos(bfqq->next_rq))
+			n = &(*p)->rb_right;
+		else if (sector < blk_rq_pos(bfqq->next_rq))
+			n = &(*p)->rb_left;
+		else
+			break;
+		p = n;
+		bfqq = NULL;
+	}
+
+	*ret_parent = parent;
+	if (rb_link)
+		*rb_link = p;
+
+	bfq_log(bfqd, "rq_pos_tree_lookup %llu: returning %d",
+		(long long unsigned)sector,
+		bfqq != NULL ? bfqq->pid : 0);
+
+	return bfqq;
+}
+
+static void bfq_rq_pos_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+{
+	struct rb_node **p, *parent;
+	struct bfq_queue *__bfqq;
+
+	if (bfqq->pos_root != NULL) {
+		rb_erase(&bfqq->pos_node, bfqq->pos_root);
+		bfqq->pos_root = NULL;
+	}
+
+	if (bfq_class_idle(bfqq))
+		return;
+	if (!bfqq->next_rq)
+		return;
+
+	bfqq->pos_root = &bfqd->rq_pos_tree;
+	__bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root,
+			blk_rq_pos(bfqq->next_rq), &parent, &p);
+	if (__bfqq == NULL) {
+		rb_link_node(&bfqq->pos_node, parent, p);
+		rb_insert_color(&bfqq->pos_node, bfqq->pos_root);
+	} else
+		bfqq->pos_root = NULL;
+}
+
+/*
+ * Tell whether there are active queues or groups with differentiated weights.
+ */
+static inline bool bfq_differentiated_weights(struct bfq_data *bfqd)
+{
+	BUG_ON(!bfqd->hw_tag);
+	/*
+	 * For weights to differ, at least one of the trees must contain
+	 * at least two nodes.
+	 */
+	return (!RB_EMPTY_ROOT(&bfqd->queue_weights_tree) &&
+		(bfqd->queue_weights_tree.rb_node->rb_left ||
+		 bfqd->queue_weights_tree.rb_node->rb_right)
+#ifdef CONFIG_CGROUP_BFQIO
+	       ) ||
+	       (!RB_EMPTY_ROOT(&bfqd->group_weights_tree) &&
+		(bfqd->group_weights_tree.rb_node->rb_left ||
+		 bfqd->group_weights_tree.rb_node->rb_right)
+#endif
+	       );
+}
+
+/*
+ * If the weight-counter tree passed as input contains no counter for
+ * the weight of the input entity, then add that counter; otherwise just
+ * increment the existing counter.
+ *
+ * Note that weight-counter trees contain few nodes in mostly symmetric
+ * scenarios. For example, if all queues have the same weight, then the
+ * weight-counter tree for the queues may contain at most one node.
+ * This holds even if low_latency is on, because weight-raised queues
+ * are not inserted in the tree.
+ * In most scenarios, the rate at which nodes are created/destroyed
+ * should be low too.
+ */
+static void bfq_weights_tree_add(struct bfq_data *bfqd,
+				 struct bfq_entity *entity,
+				 struct rb_root *root)
+{
+	struct rb_node **new = &(root->rb_node), *parent = NULL;
+
+	/*
+	 * Do not insert if:
+	 * - the device does not support queueing;
+	 * - the entity is already associated with a counter, which happens if:
+	 *   1) the entity is associated with a queue, 2) a request arrival
+	 *   has caused the queue to become both non-weight-raised, and hence
+	 *   change its weight, and backlogged; in this respect, each
+	 *   of the two events causes an invocation of this function,
+	 *   3) this is the invocation of this function caused by the second
+	 *   event. This second invocation is actually useless, and we handle
+	 *   this fact by exiting immediately. More efficient or clearer
+	 *   solutions might possibly be adopted.
+	 */
+	if (!bfqd->hw_tag || entity->weight_counter)
+		return;
+
+	while (*new) {
+		struct bfq_weight_counter *__counter = container_of(*new,
+						struct bfq_weight_counter,
+						weights_node);
+		parent = *new;
+
+		if (entity->weight == __counter->weight) {
+			entity->weight_counter = __counter;
+			goto inc_counter;
+		}
+		if (entity->weight < __counter->weight)
+			new = &((*new)->rb_left);
+		else
+			new = &((*new)->rb_right);
+	}
+
+	entity->weight_counter = kzalloc(sizeof(struct bfq_weight_counter),
+					 GFP_ATOMIC);
+	entity->weight_counter->weight = entity->weight;
+	rb_link_node(&entity->weight_counter->weights_node, parent, new);
+	rb_insert_color(&entity->weight_counter->weights_node, root);
+
+inc_counter:
+	entity->weight_counter->num_active++;
+}
+
+/*
+ * Decrement the weight counter associated with the entity, and, if the
+ * counter reaches 0, remove the counter from the tree.
+ * See the comments to the function bfq_weights_tree_add() for considerations
+ * about overhead.
+ */
+static void bfq_weights_tree_remove(struct bfq_data *bfqd,
+				    struct bfq_entity *entity,
+				    struct rb_root *root)
+{
+	/*
+	 * Check whether the entity is actually associated with a counter.
+	 * In fact, the device may not be considered NCQ-capable for a while,
+	 * which implies that no insertion in the weight trees is performed,
+	 * after which the device may start to be deemed NCQ-capable, and hence
+	 * this function may start to be invoked. This may cause the function
+	 * to be invoked for entities that are not associated with any counter.
+	 */
+	if (!entity->weight_counter)
+		return;
+
+	BUG_ON(RB_EMPTY_ROOT(root));
+	BUG_ON(entity->weight_counter->weight != entity->weight);
+
+	BUG_ON(!entity->weight_counter->num_active);
+	entity->weight_counter->num_active--;
+	if (entity->weight_counter->num_active > 0)
+		goto reset_entity_pointer;
+
+	rb_erase(&entity->weight_counter->weights_node, root);
+	kfree(entity->weight_counter);
+
+reset_entity_pointer:
+	entity->weight_counter = NULL;
+}
+
+static struct request *bfq_find_next_rq(struct bfq_data *bfqd,
+					struct bfq_queue *bfqq,
+					struct request *last)
+{
+	struct rb_node *rbnext = rb_next(&last->rb_node);
+	struct rb_node *rbprev = rb_prev(&last->rb_node);
+	struct request *next = NULL, *prev = NULL;
+
+	BUG_ON(RB_EMPTY_NODE(&last->rb_node));
+
+	if (rbprev != NULL)
+		prev = rb_entry_rq(rbprev);
+
+	if (rbnext != NULL)
+		next = rb_entry_rq(rbnext);
+	else {
+		rbnext = rb_first(&bfqq->sort_list);
+		if (rbnext && rbnext != &last->rb_node)
+			next = rb_entry_rq(rbnext);
+	}
+
+	return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last));
+}
+
+/* see the definition of bfq_async_charge_factor for details */
+static inline unsigned long bfq_serv_to_charge(struct request *rq,
+					       struct bfq_queue *bfqq)
+{
+	return blk_rq_sectors(rq) *
+		(1 + ((!bfq_bfqq_sync(bfqq)) * (bfqq->wr_coeff == 1) *
+		bfq_async_charge_factor));
+}
+
+/**
+ * bfq_updated_next_req - update the queue after a new next_rq selection.
+ * @bfqd: the device data the queue belongs to.
+ * @bfqq: the queue to update.
+ *
+ * If the first request of a queue changes we make sure that the queue
+ * has enough budget to serve at least its first request (if the
+ * request has grown).  We do this because if the queue has not enough
+ * budget for its first request, it has to go through two dispatch
+ * rounds to actually get it dispatched.
+ */
+static void bfq_updated_next_req(struct bfq_data *bfqd,
+				 struct bfq_queue *bfqq)
+{
+	struct bfq_entity *entity = &bfqq->entity;
+	struct bfq_service_tree *st = bfq_entity_service_tree(entity);
+	struct request *next_rq = bfqq->next_rq;
+	unsigned long new_budget;
+
+	if (next_rq == NULL)
+		return;
+
+	if (bfqq == bfqd->in_service_queue)
+		/*
+		 * In order not to break guarantees, budgets cannot be
+		 * changed after an entity has been selected.
+		 */
+		return;
+
+	BUG_ON(entity->tree != &st->active);
+	BUG_ON(entity == entity->sched_data->in_service_entity);
+
+	new_budget = max_t(unsigned long, bfqq->max_budget,
+			   bfq_serv_to_charge(next_rq, bfqq));
+	if (entity->budget != new_budget) {
+		entity->budget = new_budget;
+		bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu",
+					 new_budget);
+		bfq_activate_bfqq(bfqd, bfqq);
+	}
+}
+
+static inline unsigned int bfq_wr_duration(struct bfq_data *bfqd)
+{
+	u64 dur;
+
+	if (bfqd->bfq_wr_max_time > 0)
+		return bfqd->bfq_wr_max_time;
+
+	dur = bfqd->RT_prod;
+	do_div(dur, bfqd->peak_rate);
+
+	return dur;
+}
+
+static inline unsigned
+bfq_bfqq_cooperations(struct bfq_queue *bfqq)
+{
+	return bfqq->bic ? bfqq->bic->cooperations : 0;
+}
+
+static inline void
+bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
+{
+	if (bic->saved_idle_window)
+		bfq_mark_bfqq_idle_window(bfqq);
+	else
+		bfq_clear_bfqq_idle_window(bfqq);
+	if (bic->saved_IO_bound)
+		bfq_mark_bfqq_IO_bound(bfqq);
+	else
+		bfq_clear_bfqq_IO_bound(bfqq);
+	/* Assuming that the flag in_large_burst is already correctly set */
+	if (bic->wr_time_left && bfqq->bfqd->low_latency &&
+	    !bfq_bfqq_in_large_burst(bfqq) &&
+	    bic->cooperations < bfqq->bfqd->bfq_coop_thresh) {
+		/*
+		 * Start a weight raising period with the duration given by
+		 * the raising_time_left snapshot.
+		 */
+		if (bfq_bfqq_busy(bfqq))
+			bfqq->bfqd->wr_busy_queues++;
+		bfqq->wr_coeff = bfqq->bfqd->bfq_wr_coeff;
+		bfqq->wr_cur_max_time = bic->wr_time_left;
+		bfqq->last_wr_start_finish = jiffies;
+		bfqq->entity.ioprio_changed = 1;
+	}
+	/*
+	 * Clear wr_time_left to prevent bfq_bfqq_save_state() from
+	 * getting confused about the queue's need of a weight-raising
+	 * period.
+	 */
+	bic->wr_time_left = 0;
+}
+
+/* Must be called with the queue_lock held. */
+static int bfqq_process_refs(struct bfq_queue *bfqq)
+{
+	int process_refs, io_refs;
+
+	io_refs = bfqq->allocated[READ] + bfqq->allocated[WRITE];
+	process_refs = atomic_read(&bfqq->ref) - io_refs - bfqq->entity.on_st;
+	BUG_ON(process_refs < 0);
+	return process_refs;
+}
+
+/* Empty burst list and add just bfqq (see comments to bfq_handle_burst) */
+static inline void bfq_reset_burst_list(struct bfq_data *bfqd,
+					struct bfq_queue *bfqq)
+{
+	struct bfq_queue *item;
+	struct hlist_node *pos, *n;
+
+	hlist_for_each_entry_safe(item, pos, n,
+				  &bfqd->burst_list, burst_list_node)
+		hlist_del_init(&item->burst_list_node);
+	hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
+	bfqd->burst_size = 1;
+}
+
+/* Add bfqq to the list of queues in current burst (see bfq_handle_burst) */
+static void bfq_add_to_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+{
+	/* Increment burst size to take into account also bfqq */
+	bfqd->burst_size++;
+
+	if (bfqd->burst_size == bfqd->bfq_large_burst_thresh) {
+		struct bfq_queue *pos, *bfqq_item;
+		struct hlist_node *p, *n;
+
+		/*
+		 * Enough queues have been activated shortly after each
+		 * other to consider this burst as large.
+		 */
+		bfqd->large_burst = true;
+
+		/*
+		 * We can now mark all queues in the burst list as
+		 * belonging to a large burst.
+		 */
+		hlist_for_each_entry(bfqq_item, n, &bfqd->burst_list,
+				     burst_list_node)
+		        bfq_mark_bfqq_in_large_burst(bfqq_item);
+		bfq_mark_bfqq_in_large_burst(bfqq);
+
+		/*
+		 * From now on, and until the current burst finishes, any
+		 * new queue being activated shortly after the last queue
+		 * was inserted in the burst can be immediately marked as
+		 * belonging to a large burst. So the burst list is not
+		 * needed any more. Remove it.
+		 */
+		hlist_for_each_entry_safe(pos, p, n, &bfqd->burst_list,
+					  burst_list_node)
+			hlist_del_init(&pos->burst_list_node);
+	} else /* burst not yet large: add bfqq to the burst list */
+		hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
+}
+
+/*
+ * If many queues happen to become active shortly after each other, then,
+ * to help the processes associated to these queues get their job done as
+ * soon as possible, it is usually better to not grant either weight-raising
+ * or device idling to these queues. In this comment we describe, firstly,
+ * the reasons why this fact holds, and, secondly, the next function, which
+ * implements the main steps needed to properly mark these queues so that
+ * they can then be treated in a different way.
+ *
+ * As for the terminology, we say that a queue becomes active, i.e.,
+ * switches from idle to backlogged, either when it is created (as a
+ * consequence of the arrival of an I/O request), or, if already existing,
+ * when a new request for the queue arrives while the queue is idle.
+ * Bursts of activations, i.e., activations of different queues occurring
+ * shortly after each other, are typically caused by services or applications
+ * that spawn or reactivate many parallel threads/processes. Examples are
+ * systemd during boot or git grep.
+ *
+ * These services or applications benefit mostly from a high throughput:
+ * the quicker the requests of the activated queues are cumulatively served,
+ * the sooner the target job of these queues gets completed. As a consequence,
+ * weight-raising any of these queues, which also implies idling the device
+ * for it, is almost always counterproductive: in most cases it just lowers
+ * throughput.
+ *
+ * On the other hand, a burst of activations may be also caused by the start
+ * of an application that does not consist in a lot of parallel I/O-bound
+ * threads. In fact, with a complex application, the burst may be just a
+ * consequence of the fact that several processes need to be executed to
+ * start-up the application. To start an application as quickly as possible,
+ * the best thing to do is to privilege the I/O related to the application
+ * with respect to all other I/O. Therefore, the best strategy to start as
+ * quickly as possible an application that causes a burst of activations is
+ * to weight-raise all the queues activated during the burst. This is the
+ * exact opposite of the best strategy for the other type of bursts.
+ *
+ * In the end, to take the best action for each of the two cases, the two
+ * types of bursts need to be distinguished. Fortunately, this seems
+ * relatively easy to do, by looking at the sizes of the bursts. In
+ * particular, we found a threshold such that bursts with a larger size
+ * than that threshold are apparently caused only by services or commands
+ * such as systemd or git grep. For brevity, hereafter we call just 'large'
+ * these bursts. BFQ *does not* weight-raise queues whose activations occur
+ * in a large burst. In addition, for each of these queues BFQ performs or
+ * does not perform idling depending on which choice boosts the throughput
+ * most. The exact choice depends on the device and request pattern at
+ * hand.
+ *
+ * Turning back to the next function, it implements all the steps needed
+ * to detect the occurrence of a large burst and to properly mark all the
+ * queues belonging to it (so that they can then be treated in a different
+ * way). This goal is achieved by maintaining a special "burst list" that
+ * holds, temporarily, the queues that belong to the burst in progress. The
+ * list is then used to mark these queues as belonging to a large burst if
+ * the burst does become large. The main steps are the following.
+ *
+ * . when the very first queue is activated, the queue is inserted into the
+ *   list (as it could be the first queue in a possible burst)
+ *
+ * . if the current burst has not yet become large, and a queue Q that does
+ *   not yet belong to the burst is activated shortly after the last time
+ *   at which a new queue entered the burst list, then the function appends
+ *   Q to the burst list
+ *
+ * . if, as a consequence of the previous step, the burst size reaches
+ *   the large-burst threshold, then
+ *
+ *     . all the queues in the burst list are marked as belonging to a
+ *       large burst
+ *
+ *     . the burst list is deleted; in fact, the burst list already served
+ *       its purpose (keeping temporarily track of the queues in a burst,
+ *       so as to be able to mark them as belonging to a large burst in the
+ *       previous sub-step), and now is not needed any more
+ *
+ *     . the device enters a large-burst mode
+ *
+ * . if a queue Q that does not belong to the burst is activated while
+ *   the device is in large-burst mode and shortly after the last time
+ *   at which a queue either entered the burst list or was marked as
+ *   belonging to the current large burst, then Q is immediately marked
+ *   as belonging to a large burst.
+ *
+ * . if a queue Q that does not belong to the burst is activated a while
+ *   later, i.e., not shortly after, than the last time at which a queue
+ *   either entered the burst list or was marked as belonging to the
+ *   current large burst, then the current burst is deemed as finished and:
+ *
+ *        . the large-burst mode is reset if set
+ *
+ *        . the burst list is emptied
+ *
+ *        . Q is inserted in the burst list, as Q may be the first queue
+ *          in a possible new burst (then the burst list contains just Q
+ *          after this step).
+ */
+static void bfq_handle_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+			     bool idle_for_long_time)
+{
+	/*
+	 * If bfqq happened to be activated in a burst, but has been idle
+	 * for at least as long as an interactive queue, then we assume
+	 * that, in the overall I/O initiated in the burst, the I/O
+	 * associated to bfqq is finished. So bfqq does not need to be
+	 * treated as a queue belonging to a burst anymore. Accordingly,
+	 * we reset bfqq's in_large_burst flag if set, and remove bfqq
+	 * from the burst list if it's there. We do not decrement instead
+	 * burst_size, because the fact that bfqq does not need to belong
+	 * to the burst list any more does not invalidate the fact that
+	 * bfqq may have been activated during the current burst.
+	 */
+	if (idle_for_long_time) {
+		hlist_del_init(&bfqq->burst_list_node);
+		bfq_clear_bfqq_in_large_burst(bfqq);
+	}
+
+	/*
+	 * If bfqq is already in the burst list or is part of a large
+	 * burst, then there is nothing else to do.
+	 */
+	if (!hlist_unhashed(&bfqq->burst_list_node) ||
+	    bfq_bfqq_in_large_burst(bfqq))
+		return;
+
+	/*
+	 * If bfqq's activation happens late enough, then the current
+	 * burst is finished, and related data structures must be reset.
+	 *
+	 * In this respect, consider the special case where bfqq is the very
+	 * first queue being activated. In this case, last_ins_in_burst is
+	 * not yet significant when we get here. But it is easy to verify
+	 * that, whether or not the following condition is true, bfqq will
+	 * end up being inserted into the burst list. In particular the
+	 * list will happen to contain only bfqq. And this is exactly what
+	 * has to happen, as bfqq may be the first queue in a possible
+	 * burst.
+	 */
+	if (time_is_before_jiffies(bfqd->last_ins_in_burst +
+	    bfqd->bfq_burst_interval)) {
+		bfqd->large_burst = false;
+		bfq_reset_burst_list(bfqd, bfqq);
+		return;
+	}
+
+	/*
+	 * If we get here, then bfqq is being activated shortly after the
+	 * last queue. So, if the current burst is also large, we can mark
+	 * bfqq as belonging to this large burst immediately.
+	 */
+	if (bfqd->large_burst) {
+		bfq_mark_bfqq_in_large_burst(bfqq);
+		return;
+	}
+
+	/*
+	 * If we get here, then a large-burst state has not yet been
+	 * reached, but bfqq is being activated shortly after the last
+	 * queue. Then we add bfqq to the burst.
+	 */
+	bfq_add_to_burst(bfqd, bfqq);
+}
+
+static void bfq_add_request(struct request *rq)
+{
+	struct bfq_queue *bfqq = RQ_BFQQ(rq);
+	struct bfq_entity *entity = &bfqq->entity;
+	struct bfq_data *bfqd = bfqq->bfqd;
+	struct request *next_rq, *prev;
+	unsigned long old_wr_coeff = bfqq->wr_coeff;
+	bool interactive = false;
+
+	bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq));
+	bfqq->queued[rq_is_sync(rq)]++;
+	bfqd->queued++;
+
+	elv_rb_add(&bfqq->sort_list, rq);
+
+	/*
+	 * Check if this request is a better next-serve candidate.
+	 */
+	prev = bfqq->next_rq;
+	next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position);
+	BUG_ON(next_rq == NULL);
+	bfqq->next_rq = next_rq;
+
+	/*
+	 * Adjust priority tree position, if next_rq changes.
+	 */
+	if (prev != bfqq->next_rq)
+		bfq_rq_pos_tree_add(bfqd, bfqq);
+
+	if (!bfq_bfqq_busy(bfqq)) {
+		bool soft_rt, coop_or_in_burst,
+		     idle_for_long_time = time_is_before_jiffies(
+						bfqq->budget_timeout +
+						bfqd->bfq_wr_min_idle_time);
+
+		if (bfq_bfqq_sync(bfqq)) {
+			bool already_in_burst =
+			   !hlist_unhashed(&bfqq->burst_list_node) ||
+			   bfq_bfqq_in_large_burst(bfqq);
+			bfq_handle_burst(bfqd, bfqq, idle_for_long_time);
+			/*
+			 * If bfqq was not already in the current burst,
+			 * then, at this point, bfqq either has been
+			 * added to the current burst or has caused the
+			 * current burst to terminate. In particular, in
+			 * the second case, bfqq has become the first
+			 * queue in a possible new burst.
+			 * In both cases last_ins_in_burst needs to be
+			 * moved forward.
+			 */
+			if (!already_in_burst)
+				bfqd->last_ins_in_burst = jiffies;
+		}
+
+		coop_or_in_burst = bfq_bfqq_in_large_burst(bfqq) ||
+			bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh;
+		soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 &&
+			!coop_or_in_burst &&
+			time_is_before_jiffies(bfqq->soft_rt_next_start);
+		interactive = !coop_or_in_burst && idle_for_long_time;
+		entity->budget = max_t(unsigned long, bfqq->max_budget,
+				       bfq_serv_to_charge(next_rq, bfqq));
+
+		if (!bfq_bfqq_IO_bound(bfqq)) {
+			if (time_before(jiffies,
+					RQ_BIC(rq)->ttime.last_end_request +
+					bfqd->bfq_slice_idle)) {
+				bfqq->requests_within_timer++;
+				if (bfqq->requests_within_timer >=
+				    bfqd->bfq_requests_within_timer)
+					bfq_mark_bfqq_IO_bound(bfqq);
+			} else
+				bfqq->requests_within_timer = 0;
+		}
+
+		if (!bfqd->low_latency)
+			goto add_bfqq_busy;
+
+		if (bfq_bfqq_just_split(bfqq))
+			goto set_ioprio_changed;
+
+		/*
+		 * If the queue:
+		 * - is not being boosted,
+		 * - has been idle for enough time,
+		 * - is not a sync queue or is linked to a bfq_io_cq (it is
+		 *   shared "for its nature" or it is not shared and its
+		 *   requests have not been redirected to a shared queue)
+		 * start a weight-raising period.
+		 */
+		if (old_wr_coeff == 1 && (interactive || soft_rt) &&
+		    (!bfq_bfqq_sync(bfqq) || bfqq->bic != NULL)) {
+			bfqq->wr_coeff = bfqd->bfq_wr_coeff;
+			if (interactive)
+				bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
+			else
+				bfqq->wr_cur_max_time =
+					bfqd->bfq_wr_rt_max_time;
+			bfq_log_bfqq(bfqd, bfqq,
+				     "wrais starting at %lu, rais_max_time %u",
+				     jiffies,
+				     jiffies_to_msecs(bfqq->wr_cur_max_time));
+		} else if (old_wr_coeff > 1) {
+			if (interactive)
+				bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
+			else if (coop_or_in_burst ||
+				 (bfqq->wr_cur_max_time ==
+				  bfqd->bfq_wr_rt_max_time &&
+				  !soft_rt)) {
+				bfqq->wr_coeff = 1;
+				bfq_log_bfqq(bfqd, bfqq,
+					"wrais ending at %lu, rais_max_time %u",
+					jiffies,
+					jiffies_to_msecs(bfqq->
+						wr_cur_max_time));
+			} else if (time_before(
+					bfqq->last_wr_start_finish +
+					bfqq->wr_cur_max_time,
+					jiffies +
+					bfqd->bfq_wr_rt_max_time) &&
+				   soft_rt) {
+				/*
+				 *
+				 * The remaining weight-raising time is lower
+				 * than bfqd->bfq_wr_rt_max_time, which means
+				 * that the application is enjoying weight
+				 * raising either because deemed soft-rt in
+				 * the near past, or because deemed interactive
+				 * a long ago.
+				 * In both cases, resetting now the current
+				 * remaining weight-raising time for the
+				 * application to the weight-raising duration
+				 * for soft rt applications would not cause any
+				 * latency increase for the application (as the
+				 * new duration would be higher than the
+				 * remaining time).
+				 *
+				 * In addition, the application is now meeting
+				 * the requirements for being deemed soft rt.
+				 * In the end we can correctly and safely
+				 * (re)charge the weight-raising duration for
+				 * the application with the weight-raising
+				 * duration for soft rt applications.
+				 *
+				 * In particular, doing this recharge now, i.e.,
+				 * before the weight-raising period for the
+				 * application finishes, reduces the probability
+				 * of the following negative scenario:
+				 * 1) the weight of a soft rt application is
+				 *    raised at startup (as for any newly
+				 *    created application),
+				 * 2) since the application is not interactive,
+				 *    at a certain time weight-raising is
+				 *    stopped for the application,
+				 * 3) at that time the application happens to
+				 *    still have pending requests, and hence
+				 *    is destined to not have a chance to be
+				 *    deemed soft rt before these requests are
+				 *    completed (see the comments to the
+				 *    function bfq_bfqq_softrt_next_start()
+				 *    for details on soft rt detection),
+				 * 4) these pending requests experience a high
+				 *    latency because the application is not
+				 *    weight-raised while they are pending.
+				 */
+				bfqq->last_wr_start_finish = jiffies;
+				bfqq->wr_cur_max_time =
+					bfqd->bfq_wr_rt_max_time;
+			}
+		}
+set_ioprio_changed:
+		if (old_wr_coeff != bfqq->wr_coeff)
+			entity->ioprio_changed = 1;
+add_bfqq_busy:
+		bfqq->last_idle_bklogged = jiffies;
+		bfqq->service_from_backlogged = 0;
+		bfq_clear_bfqq_softrt_update(bfqq);
+		bfq_add_bfqq_busy(bfqd, bfqq);
+	} else {
+		if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) &&
+		    time_is_before_jiffies(
+				bfqq->last_wr_start_finish +
+				bfqd->bfq_wr_min_inter_arr_async)) {
+			bfqq->wr_coeff = bfqd->bfq_wr_coeff;
+			bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
+
+			bfqd->wr_busy_queues++;
+			entity->ioprio_changed = 1;
+			bfq_log_bfqq(bfqd, bfqq,
+			    "non-idle wrais starting at %lu, rais_max_time %u",
+			    jiffies,
+			    jiffies_to_msecs(bfqq->wr_cur_max_time));
+		}
+		if (prev != bfqq->next_rq)
+			bfq_updated_next_req(bfqd, bfqq);
+	}
+
+	if (bfqd->low_latency &&
+		(old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive))
+		bfqq->last_wr_start_finish = jiffies;
+}
+
+static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd,
+					  struct bio *bio)
+{
+	struct task_struct *tsk = current;
+	struct bfq_io_cq *bic;
+	struct bfq_queue *bfqq;
+
+	bic = bfq_bic_lookup(bfqd, tsk->io_context);
+	if (bic == NULL)
+		return NULL;
+
+	bfqq = bic_to_bfqq(bic, bfq_bio_sync(bio));
+	if (bfqq != NULL) {
+		sector_t sector = bio->bi_sector + bio_sectors(bio);
+
+		return elv_rb_find(&bfqq->sort_list, sector);
+	}
+
+	return NULL;
+}
+
+static void bfq_activate_request(struct request_queue *q, struct request *rq)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+
+	bfqd->rq_in_driver++;
+	bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
+	bfq_log(bfqd, "activate_request: new bfqd->last_position %llu",
+		(long long unsigned)bfqd->last_position);
+}
+
+static inline void bfq_deactivate_request(struct request_queue *q,
+					  struct request *rq)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+
+	BUG_ON(bfqd->rq_in_driver == 0);
+	bfqd->rq_in_driver--;
+}
+
+static void bfq_remove_request(struct request *rq)
+{
+	struct bfq_queue *bfqq = RQ_BFQQ(rq);
+	struct bfq_data *bfqd = bfqq->bfqd;
+	const int sync = rq_is_sync(rq);
+
+	if (bfqq->next_rq == rq) {
+		bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq);
+		bfq_updated_next_req(bfqd, bfqq);
+	}
+
+	list_del_init(&rq->queuelist);
+	BUG_ON(bfqq->queued[sync] == 0);
+	bfqq->queued[sync]--;
+	bfqd->queued--;
+	elv_rb_del(&bfqq->sort_list, rq);
+
+	if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
+		if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue)
+			bfq_del_bfqq_busy(bfqd, bfqq, 1);
+		/*
+		 * Remove queue from request-position tree as it is empty.
+		 */
+		if (bfqq->pos_root != NULL) {
+			rb_erase(&bfqq->pos_node, bfqq->pos_root);
+			bfqq->pos_root = NULL;
+		}
+	}
+
+	if (rq->cmd_flags & REQ_META) {
+		BUG_ON(bfqq->meta_pending == 0);
+		bfqq->meta_pending--;
+	}
+}
+
+static int bfq_merge(struct request_queue *q, struct request **req,
+		     struct bio *bio)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+	struct request *__rq;
+
+	__rq = bfq_find_rq_fmerge(bfqd, bio);
+	if (__rq != NULL && elv_rq_merge_ok(__rq, bio)) {
+		*req = __rq;
+		return ELEVATOR_FRONT_MERGE;
+	}
+
+	return ELEVATOR_NO_MERGE;
+}
+
+static void bfq_merged_request(struct request_queue *q, struct request *req,
+			       int type)
+{
+	if (type == ELEVATOR_FRONT_MERGE &&
+	    rb_prev(&req->rb_node) &&
+	    blk_rq_pos(req) <
+	    blk_rq_pos(container_of(rb_prev(&req->rb_node),
+				    struct request, rb_node))) {
+		struct bfq_queue *bfqq = RQ_BFQQ(req);
+		struct bfq_data *bfqd = bfqq->bfqd;
+		struct request *prev, *next_rq;
+
+		/* Reposition request in its sort_list */
+		elv_rb_del(&bfqq->sort_list, req);
+		elv_rb_add(&bfqq->sort_list, req);
+		/* Choose next request to be served for bfqq */
+		prev = bfqq->next_rq;
+		next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req,
+					 bfqd->last_position);
+		BUG_ON(next_rq == NULL);
+		bfqq->next_rq = next_rq;
+		/*
+		 * If next_rq changes, update both the queue's budget to
+		 * fit the new request and the queue's position in its
+		 * rq_pos_tree.
+		 */
+		if (prev != bfqq->next_rq) {
+			bfq_updated_next_req(bfqd, bfqq);
+			bfq_rq_pos_tree_add(bfqd, bfqq);
+		}
+	}
+}
+
+static void bfq_merged_requests(struct request_queue *q, struct request *rq,
+				struct request *next)
+{
+	struct bfq_queue *bfqq = RQ_BFQQ(rq);
+
+	/*
+	 * Reposition in fifo if next is older than rq.
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
+	    time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
+		list_move(&rq->queuelist, &next->queuelist);
+		rq_set_fifo_time(rq, rq_fifo_time(next));
+	}
+
+	if (bfqq->next_rq == next)
+		bfqq->next_rq = rq;
+
+	bfq_remove_request(next);
+}
+
+/* Must be called with bfqq != NULL */
+static inline void bfq_bfqq_end_wr(struct bfq_queue *bfqq)
+{
+	BUG_ON(bfqq == NULL);
+	if (bfq_bfqq_busy(bfqq))
+		bfqq->bfqd->wr_busy_queues--;
+	bfqq->wr_coeff = 1;
+	bfqq->wr_cur_max_time = 0;
+	/* Trigger a weight change on the next activation of the queue */
+	bfqq->entity.ioprio_changed = 1;
+}
+
+static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
+				    struct bfq_group *bfqg)
+{
+	int i, j;
+
+	for (i = 0; i < 2; i++)
+		for (j = 0; j < IOPRIO_BE_NR; j++)
+			if (bfqg->async_bfqq[i][j] != NULL)
+				bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
+	if (bfqg->async_idle_bfqq != NULL)
+		bfq_bfqq_end_wr(bfqg->async_idle_bfqq);
+}
+
+static void bfq_end_wr(struct bfq_data *bfqd)
+{
+	struct bfq_queue *bfqq;
+
+	spin_lock_irq(bfqd->queue->queue_lock);
+
+	list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list)
+		bfq_bfqq_end_wr(bfqq);
+	list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list)
+		bfq_bfqq_end_wr(bfqq);
+	bfq_end_wr_async(bfqd);
+
+	spin_unlock_irq(bfqd->queue->queue_lock);
+}
+
+static inline sector_t bfq_io_struct_pos(void *io_struct, bool request)
+{
+	if (request)
+		return blk_rq_pos(io_struct);
+	else
+		return ((struct bio *)io_struct)->bi_sector;
+}
+
+static inline sector_t bfq_dist_from(sector_t pos1,
+				     sector_t pos2)
+{
+	if (pos1 >= pos2)
+		return pos1 - pos2;
+	else
+		return pos2 - pos1;
+}
+
+static inline int bfq_rq_close_to_sector(void *io_struct, bool request,
+					 sector_t sector)
+{
+	return bfq_dist_from(bfq_io_struct_pos(io_struct, request), sector) <=
+	       BFQQ_SEEK_THR;
+}
+
+static struct bfq_queue *bfqq_close(struct bfq_data *bfqd, sector_t sector)
+{
+	struct rb_root *root = &bfqd->rq_pos_tree;
+	struct rb_node *parent, *node;
+	struct bfq_queue *__bfqq;
+
+	if (RB_EMPTY_ROOT(root))
+		return NULL;
+
+	/*
+	 * First, if we find a request starting at the end of the last
+	 * request, choose it.
+	 */
+	__bfqq = bfq_rq_pos_tree_lookup(bfqd, root, sector, &parent, NULL);
+	if (__bfqq != NULL)
+		return __bfqq;
+
+	/*
+	 * If the exact sector wasn't found, the parent of the NULL leaf
+	 * will contain the closest sector (rq_pos_tree sorted by
+	 * next_request position).
+	 */
+	__bfqq = rb_entry(parent, struct bfq_queue, pos_node);
+	if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
+		return __bfqq;
+
+	if (blk_rq_pos(__bfqq->next_rq) < sector)
+		node = rb_next(&__bfqq->pos_node);
+	else
+		node = rb_prev(&__bfqq->pos_node);
+	if (node == NULL)
+		return NULL;
+
+	__bfqq = rb_entry(node, struct bfq_queue, pos_node);
+	if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
+		return __bfqq;
+
+	return NULL;
+}
+
+/*
+ * bfqd - obvious
+ * cur_bfqq - passed in so that we don't decide that the current queue
+ *            is closely cooperating with itself
+ * sector - used as a reference point to search for a close queue
+ */
+static struct bfq_queue *bfq_close_cooperator(struct bfq_data *bfqd,
+					      struct bfq_queue *cur_bfqq,
+					      sector_t sector)
+{
+	struct bfq_queue *bfqq;
+
+	if (bfq_class_idle(cur_bfqq))
+		return NULL;
+	if (!bfq_bfqq_sync(cur_bfqq))
+		return NULL;
+	if (BFQQ_SEEKY(cur_bfqq))
+		return NULL;
+
+	/* If device has only one backlogged bfq_queue, don't search. */
+	if (bfqd->busy_queues == 1)
+		return NULL;
+
+	/*
+	 * We should notice if some of the queues are cooperating, e.g.
+	 * working closely on the same area of the disk. In that case,
+	 * we can group them together and don't waste time idling.
+	 */
+	bfqq = bfqq_close(bfqd, sector);
+	if (bfqq == NULL || bfqq == cur_bfqq)
+		return NULL;
+
+	/*
+	 * Do not merge queues from different bfq_groups.
+	*/
+	if (bfqq->entity.parent != cur_bfqq->entity.parent)
+		return NULL;
+
+	/*
+	 * It only makes sense to merge sync queues.
+	 */
+	if (!bfq_bfqq_sync(bfqq))
+		return NULL;
+	if (BFQQ_SEEKY(bfqq))
+		return NULL;
+
+	/*
+	 * Do not merge queues of different priority classes.
+	 */
+	if (bfq_class_rt(bfqq) != bfq_class_rt(cur_bfqq))
+		return NULL;
+
+	return bfqq;
+}
+
+static struct bfq_queue *
+bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
+{
+	int process_refs, new_process_refs;
+	struct bfq_queue *__bfqq;
+
+	/*
+	 * If there are no process references on the new_bfqq, then it is
+	 * unsafe to follow the ->new_bfqq chain as other bfqq's in the chain
+	 * may have dropped their last reference (not just their last process
+	 * reference).
+	 */
+	if (!bfqq_process_refs(new_bfqq))
+		return NULL;
+
+	/* Avoid a circular list and skip interim queue merges. */
+	while ((__bfqq = new_bfqq->new_bfqq)) {
+		if (__bfqq == bfqq)
+			return NULL;
+		new_bfqq = __bfqq;
+	}
+
+	process_refs = bfqq_process_refs(bfqq);
+	new_process_refs = bfqq_process_refs(new_bfqq);
+	/*
+	 * If the process for the bfqq has gone away, there is no
+	 * sense in merging the queues.
+	 */
+	if (process_refs == 0 || new_process_refs == 0)
+		return NULL;
+
+	bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d",
+		new_bfqq->pid);
+
+	/*
+	 * Merging is just a redirection: the requests of the process
+	 * owning one of the two queues are redirected to the other queue.
+	 * The latter queue, in its turn, is set as shared if this is the
+	 * first time that the requests of some process are redirected to
+	 * it.
+	 *
+	 * We redirect bfqq to new_bfqq and not the opposite, because we
+	 * are in the context of the process owning bfqq, hence we have
+	 * the io_cq of this process. So we can immediately configure this
+	 * io_cq to redirect the requests of the process to new_bfqq.
+	 *
+	 * NOTE, even if new_bfqq coincides with the in-service queue, the
+	 * io_cq of new_bfqq is not available, because, if the in-service
+	 * queue is shared, bfqd->in_service_bic may not point to the
+	 * io_cq of the in-service queue.
+	 * Redirecting the requests of the process owning bfqq to the
+	 * currently in-service queue is in any case the best option, as
+	 * we feed the in-service queue with new requests close to the
+	 * last request served and, by doing so, hopefully increase the
+	 * throughput.
+	 */
+	bfqq->new_bfqq = new_bfqq;
+	atomic_add(process_refs, &new_bfqq->ref);
+	return new_bfqq;
+}
+
+/*
+ * Attempt to schedule a merge of bfqq with the currently in-service queue
+ * or with a close queue among the scheduled queues.
+ * Return NULL if no merge was scheduled, a pointer to the shared bfq_queue
+ * structure otherwise.
+ *
+ * The OOM queue is not allowed to participate to cooperation: in fact, since
+ * the requests temporarily redirected to the OOM queue could be redirected
+ * again to dedicated queues at any time, the state needed to correctly
+ * handle merging with the OOM queue would be quite complex and expensive
+ * to maintain. Besides, in such a critical condition as an out of memory,
+ * the benefits of queue merging may be little relevant, or even negligible.
+ */
+static struct bfq_queue *
+bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+		     void *io_struct, bool request)
+{
+	struct bfq_queue *in_service_bfqq, *new_bfqq;
+
+	if (bfqq->new_bfqq)
+		return bfqq->new_bfqq;
+
+	if (!io_struct || unlikely(bfqq == &bfqd->oom_bfqq))
+		return NULL;
+
+	in_service_bfqq = bfqd->in_service_queue;
+
+	if (in_service_bfqq == NULL || in_service_bfqq == bfqq ||
+	    !bfqd->in_service_bic ||
+	    unlikely(in_service_bfqq == &bfqd->oom_bfqq))
+		goto check_scheduled;
+
+	if (bfq_class_idle(in_service_bfqq) || bfq_class_idle(bfqq))
+		goto check_scheduled;
+
+	if (bfq_class_rt(in_service_bfqq) != bfq_class_rt(bfqq))
+		goto check_scheduled;
+
+	if (in_service_bfqq->entity.parent != bfqq->entity.parent)
+		goto check_scheduled;
+
+	if (bfq_rq_close_to_sector(io_struct, request, bfqd->last_position) &&
+	    bfq_bfqq_sync(in_service_bfqq) && bfq_bfqq_sync(bfqq)) {
+		new_bfqq = bfq_setup_merge(bfqq, in_service_bfqq);
+		if (new_bfqq != NULL)
+			return new_bfqq; /* Merge with in-service queue */
+	}
+
+	/*
+	 * Check whether there is a cooperator among currently scheduled
+	 * queues. The only thing we need is that the bio/request is not
+	 * NULL, as we need it to establish whether a cooperator exists.
+	 */
+check_scheduled:
+	new_bfqq = bfq_close_cooperator(bfqd, bfqq,
+					bfq_io_struct_pos(io_struct, request));
+	if (new_bfqq && likely(new_bfqq != &bfqd->oom_bfqq))
+		return bfq_setup_merge(bfqq, new_bfqq);
+
+	return NULL;
+}
+
+static inline void
+bfq_bfqq_save_state(struct bfq_queue *bfqq)
+{
+	/*
+	 * If bfqq->bic == NULL, the queue is already shared or its requests
+	 * have already been redirected to a shared queue; both idle window
+	 * and weight raising state have already been saved. Do nothing.
+	 */
+	if (bfqq->bic == NULL)
+		return;
+	if (bfqq->bic->wr_time_left)
+		/*
+		 * This is the queue of a just-started process, and would
+		 * deserve weight raising: we set wr_time_left to the full
+		 * weight-raising duration to trigger weight-raising when
+		 * and if the queue is split and the first request of the
+		 * queue is enqueued.
+		 */
+		bfqq->bic->wr_time_left = bfq_wr_duration(bfqq->bfqd);
+	else if (bfqq->wr_coeff > 1) {
+		unsigned long wr_duration =
+			jiffies - bfqq->last_wr_start_finish;
+		/*
+		 * It may happen that a queue's weight raising period lasts
+		 * longer than its wr_cur_max_time, as weight raising is
+		 * handled only when a request is enqueued or dispatched (it
+		 * does not use any timer). If the weight raising period is
+		 * about to end, don't save it.
+		 */
+		if (bfqq->wr_cur_max_time <= wr_duration)
+			bfqq->bic->wr_time_left = 0;
+		else
+			bfqq->bic->wr_time_left =
+				bfqq->wr_cur_max_time - wr_duration;
+		/*
+		 * The bfq_queue is becoming shared or the requests of the
+		 * process owning the queue are being redirected to a shared
+		 * queue. Stop the weight raising period of the queue, as in
+		 * both cases it should not be owned by an interactive or
+		 * soft real-time application.
+		 */
+		bfq_bfqq_end_wr(bfqq);
+	} else
+		bfqq->bic->wr_time_left = 0;
+	bfqq->bic->saved_idle_window = bfq_bfqq_idle_window(bfqq);
+	bfqq->bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
+	bfqq->bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq);
+	bfqq->bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node);
+	bfqq->bic->cooperations++;
+	bfqq->bic->failed_cooperations = 0;
+}
+
+static inline void
+bfq_get_bic_reference(struct bfq_queue *bfqq)
+{
+	/*
+	 * If bfqq->bic has a non-NULL value, the bic to which it belongs
+	 * is about to begin using a shared bfq_queue.
+	 */
+	if (bfqq->bic)
+		atomic_long_inc(&bfqq->bic->icq.ioc->refcount);
+}
+
+static void
+bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
+		struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
+{
+	bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu",
+		(long unsigned)new_bfqq->pid);
+	/* Save weight raising and idle window of the merged queues */
+	bfq_bfqq_save_state(bfqq);
+	bfq_bfqq_save_state(new_bfqq);
+	if (bfq_bfqq_IO_bound(bfqq))
+		bfq_mark_bfqq_IO_bound(new_bfqq);
+	bfq_clear_bfqq_IO_bound(bfqq);
+	/*
+	 * Grab a reference to the bic, to prevent it from being destroyed
+	 * before being possibly touched by a bfq_split_bfqq().
+	 */
+	bfq_get_bic_reference(bfqq);
+	bfq_get_bic_reference(new_bfqq);
+	/*
+	 * Merge queues (that is, let bic redirect its requests to new_bfqq)
+	 */
+	bic_set_bfqq(bic, new_bfqq, 1);
+	bfq_mark_bfqq_coop(new_bfqq);
+	/*
+	 * new_bfqq now belongs to at least two bics (it is a shared queue):
+	 * set new_bfqq->bic to NULL. bfqq either:
+	 * - does not belong to any bic any more, and hence bfqq->bic must
+	 *   be set to NULL, or
+	 * - is a queue whose owning bics have already been redirected to a
+	 *   different queue, hence the queue is destined to not belong to
+	 *   any bic soon and bfqq->bic is already NULL (therefore the next
+	 *   assignment causes no harm).
+	 */
+	new_bfqq->bic = NULL;
+	bfqq->bic = NULL;
+	bfq_put_queue(bfqq);
+}
+
+static inline void bfq_bfqq_increase_failed_cooperations(struct bfq_queue *bfqq)
+{
+	struct bfq_io_cq *bic = bfqq->bic;
+	struct bfq_data *bfqd = bfqq->bfqd;
+
+	if (bic && bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh) {
+		bic->failed_cooperations++;
+		if (bic->failed_cooperations >= bfqd->bfq_failed_cooperations)
+			bic->cooperations = 0;
+	}
+}
+
+static int bfq_allow_merge(struct request_queue *q, struct request *rq,
+			   struct bio *bio)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+	struct bfq_io_cq *bic;
+	struct bfq_queue *bfqq, *new_bfqq;
+
+	/*
+	 * Disallow merge of a sync bio into an async request.
+	 */
+	if (bfq_bio_sync(bio) && !rq_is_sync(rq))
+		return 0;
+
+	/*
+	 * Lookup the bfqq that this bio will be queued with. Allow
+	 * merge only if rq is queued there.
+	 * Queue lock is held here.
+	 */
+	bic = bfq_bic_lookup(bfqd, current->io_context);
+	if (bic == NULL)
+		return 0;
+
+	bfqq = bic_to_bfqq(bic, bfq_bio_sync(bio));
+	/*
+	 * We take advantage of this function to perform an early merge
+	 * of the queues of possible cooperating processes.
+	 */
+	if (bfqq != NULL) {
+		new_bfqq = bfq_setup_cooperator(bfqd, bfqq, bio, false);
+		if (new_bfqq != NULL) {
+			bfq_merge_bfqqs(bfqd, bic, bfqq, new_bfqq);
+			/*
+			 * If we get here, the bio will be queued in the
+			 * shared queue, i.e., new_bfqq, so use new_bfqq
+			 * to decide whether bio and rq can be merged.
+			 */
+			bfqq = new_bfqq;
+		} else
+			bfq_bfqq_increase_failed_cooperations(bfqq);
+	}
+
+	return bfqq == RQ_BFQQ(rq);
+}
+
+static void __bfq_set_in_service_queue(struct bfq_data *bfqd,
+				       struct bfq_queue *bfqq)
+{
+	if (bfqq != NULL) {
+		bfq_mark_bfqq_must_alloc(bfqq);
+		bfq_mark_bfqq_budget_new(bfqq);
+		bfq_clear_bfqq_fifo_expire(bfqq);
+
+		bfqd->budgets_assigned = (bfqd->budgets_assigned*7 + 256) / 8;
+
+		bfq_log_bfqq(bfqd, bfqq,
+			     "set_in_service_queue, cur-budget = %lu",
+			     bfqq->entity.budget);
+	}
+
+	bfqd->in_service_queue = bfqq;
+}
+
+/*
+ * Get and set a new queue for service.
+ */
+static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd)
+{
+	struct bfq_queue *bfqq = bfq_get_next_queue(bfqd);
+
+	__bfq_set_in_service_queue(bfqd, bfqq);
+	return bfqq;
+}
+
+/*
+ * If enough samples have been computed, return the current max budget
+ * stored in bfqd, which is dynamically updated according to the
+ * estimated disk peak rate; otherwise return the default max budget
+ */
+static inline unsigned long bfq_max_budget(struct bfq_data *bfqd)
+{
+	if (bfqd->budgets_assigned < 194)
+		return bfq_default_max_budget;
+	else
+		return bfqd->bfq_max_budget;
+}
+
+/*
+ * Return min budget, which is a fraction of the current or default
+ * max budget (trying with 1/32)
+ */
+static inline unsigned long bfq_min_budget(struct bfq_data *bfqd)
+{
+	if (bfqd->budgets_assigned < 194)
+		return bfq_default_max_budget / 32;
+	else
+		return bfqd->bfq_max_budget / 32;
+}
+
+static void bfq_arm_slice_timer(struct bfq_data *bfqd)
+{
+	struct bfq_queue *bfqq = bfqd->in_service_queue;
+	struct bfq_io_cq *bic;
+	unsigned long sl;
+
+	BUG_ON(!RB_EMPTY_ROOT(&bfqq->sort_list));
+
+	/* Processes have exited, don't wait. */
+	bic = bfqd->in_service_bic;
+	if (bic == NULL || atomic_read(&bic->icq.ioc->nr_tasks) == 0)
+		return;
+
+	bfq_mark_bfqq_wait_request(bfqq);
+
+	/*
+	 * We don't want to idle for seeks, but we do want to allow
+	 * fair distribution of slice time for a process doing back-to-back
+	 * seeks. So allow a little bit of time for him to submit a new rq.
+	 *
+	 * To prevent processes with (partly) seeky workloads from
+	 * being too ill-treated, grant them a small fraction of the
+	 * assigned budget before reducing the waiting time to
+	 * BFQ_MIN_TT. This happened to help reduce latency.
+	 */
+	sl = bfqd->bfq_slice_idle;
+	/*
+	 * Unless the queue is being weight-raised, grant only minimum idle
+	 * time if the queue either has been seeky for long enough or has
+	 * already proved to be constantly seeky.
+	 */
+	if (bfq_sample_valid(bfqq->seek_samples) &&
+	    ((BFQQ_SEEKY(bfqq) && bfqq->entity.service >
+				  bfq_max_budget(bfqq->bfqd) / 8) ||
+	      bfq_bfqq_constantly_seeky(bfqq)) && bfqq->wr_coeff == 1)
+		sl = min(sl, msecs_to_jiffies(BFQ_MIN_TT));
+	else if (bfqq->wr_coeff > 1)
+		sl = sl * 3;
+	bfqd->last_idling_start = ktime_get();
+	mod_timer(&bfqd->idle_slice_timer, jiffies + sl);
+	bfq_log(bfqd, "arm idle: %u/%u ms",
+		jiffies_to_msecs(sl), jiffies_to_msecs(bfqd->bfq_slice_idle));
+}
+
+/*
+ * Set the maximum time for the in-service queue to consume its
+ * budget. This prevents seeky processes from lowering the disk
+ * throughput (always guaranteed with a time slice scheme as in CFQ).
+ */
+static void bfq_set_budget_timeout(struct bfq_data *bfqd)
+{
+	struct bfq_queue *bfqq = bfqd->in_service_queue;
+	unsigned int timeout_coeff;
+	if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time)
+		timeout_coeff = 1;
+	else
+		timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight;
+
+	bfqd->last_budget_start = ktime_get();
+
+	bfq_clear_bfqq_budget_new(bfqq);
+	bfqq->budget_timeout = jiffies +
+		bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] * timeout_coeff;
+
+	bfq_log_bfqq(bfqd, bfqq, "set budget_timeout %u",
+		jiffies_to_msecs(bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] *
+		timeout_coeff));
+}
+
+/*
+ * Move request from internal lists to the request queue dispatch list.
+ */
+static void bfq_dispatch_insert(struct request_queue *q, struct request *rq)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+	struct bfq_queue *bfqq = RQ_BFQQ(rq);
+
+	/*
+	 * For consistency, the next instruction should have been executed
+	 * after removing the request from the queue and dispatching it.
+	 * We execute instead this instruction before bfq_remove_request()
+	 * (and hence introduce a temporary inconsistency), for efficiency.
+	 * In fact, in a forced_dispatch, this prevents two counters related
+	 * to bfqq->dispatched to risk to be uselessly decremented if bfqq
+	 * is not in service, and then to be incremented again after
+	 * incrementing bfqq->dispatched.
+	 */
+	bfqq->dispatched++;
+	bfq_remove_request(rq);
+	elv_dispatch_sort(q, rq);
+
+	if (bfq_bfqq_sync(bfqq))
+		bfqd->sync_flight++;
+}
+
+/*
+ * Return expired entry, or NULL to just start from scratch in rbtree.
+ */
+static struct request *bfq_check_fifo(struct bfq_queue *bfqq)
+{
+	struct request *rq = NULL;
+
+	if (bfq_bfqq_fifo_expire(bfqq))
+		return NULL;
+
+	bfq_mark_bfqq_fifo_expire(bfqq);
+
+	if (list_empty(&bfqq->fifo))
+		return NULL;
+
+	rq = rq_entry_fifo(bfqq->fifo.next);
+
+	if (time_before(jiffies, rq_fifo_time(rq)))
+		return NULL;
+
+	return rq;
+}
+
+static inline unsigned long bfq_bfqq_budget_left(struct bfq_queue *bfqq)
+{
+	struct bfq_entity *entity = &bfqq->entity;
+	return entity->budget - entity->service;
+}
+
+static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+{
+	BUG_ON(bfqq != bfqd->in_service_queue);
+
+	__bfq_bfqd_reset_in_service(bfqd);
+
+	/*
+	 * If this bfqq is shared between multiple processes, check
+	 * to make sure that those processes are still issuing I/Os
+	 * within the mean seek distance. If not, it may be time to
+	 * break the queues apart again.
+	 */
+	if (bfq_bfqq_coop(bfqq) && BFQQ_SEEKY(bfqq))
+		bfq_mark_bfqq_split_coop(bfqq);
+
+	if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
+		/*
+		 * Overloading budget_timeout field to store the time
+		 * at which the queue remains with no backlog; used by
+		 * the weight-raising mechanism.
+		 */
+		bfqq->budget_timeout = jiffies;
+		bfq_del_bfqq_busy(bfqd, bfqq, 1);
+	} else {
+		bfq_activate_bfqq(bfqd, bfqq);
+		/*
+		 * Resort priority tree of potential close cooperators.
+		 */
+		bfq_rq_pos_tree_add(bfqd, bfqq);
+	}
+}
+
+/**
+ * __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior.
+ * @bfqd: device data.
+ * @bfqq: queue to update.
+ * @reason: reason for expiration.
+ *
+ * Handle the feedback on @bfqq budget.  See the body for detailed
+ * comments.
+ */
+static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd,
+				     struct bfq_queue *bfqq,
+				     enum bfqq_expiration reason)
+{
+	struct request *next_rq;
+	unsigned long budget, min_budget;
+
+	budget = bfqq->max_budget;
+	min_budget = bfq_min_budget(bfqd);
+
+	BUG_ON(bfqq != bfqd->in_service_queue);
+
+	bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %lu, budg left %lu",
+		bfqq->entity.budget, bfq_bfqq_budget_left(bfqq));
+	bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %lu, min budg %lu",
+		budget, bfq_min_budget(bfqd));
+	bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d",
+		bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue));
+
+	if (bfq_bfqq_sync(bfqq)) {
+		switch (reason) {
+		/*
+		 * Caveat: in all the following cases we trade latency
+		 * for throughput.
+		 */
+		case BFQ_BFQQ_TOO_IDLE:
+			/*
+			 * This is the only case where we may reduce
+			 * the budget: if there is no request of the
+			 * process still waiting for completion, then
+			 * we assume (tentatively) that the timer has
+			 * expired because the batch of requests of
+			 * the process could have been served with a
+			 * smaller budget.  Hence, betting that
+			 * process will behave in the same way when it
+			 * becomes backlogged again, we reduce its
+			 * next budget.  As long as we guess right,
+			 * this budget cut reduces the latency
+			 * experienced by the process.
+			 *
+			 * However, if there are still outstanding
+			 * requests, then the process may have not yet
+			 * issued its next request just because it is
+			 * still waiting for the completion of some of
+			 * the still outstanding ones.  So in this
+			 * subcase we do not reduce its budget, on the
+			 * contrary we increase it to possibly boost
+			 * the throughput, as discussed in the
+			 * comments to the BUDGET_TIMEOUT case.
+			 */
+			if (bfqq->dispatched > 0) /* still outstanding reqs */
+				budget = min(budget * 2, bfqd->bfq_max_budget);
+			else {
+				if (budget > 5 * min_budget)
+					budget -= 4 * min_budget;
+				else
+					budget = min_budget;
+			}
+			break;
+		case BFQ_BFQQ_BUDGET_TIMEOUT:
+			/*
+			 * We double the budget here because: 1) it
+			 * gives the chance to boost the throughput if
+			 * this is not a seeky process (which may have
+			 * bumped into this timeout because of, e.g.,
+			 * ZBR), 2) together with charge_full_budget
+			 * it helps give seeky processes higher
+			 * timestamps, and hence be served less
+			 * frequently.
+			 */
+			budget = min(budget * 2, bfqd->bfq_max_budget);
+			break;
+		case BFQ_BFQQ_BUDGET_EXHAUSTED:
+			/*
+			 * The process still has backlog, and did not
+			 * let either the budget timeout or the disk
+			 * idling timeout expire. Hence it is not
+			 * seeky, has a short thinktime and may be
+			 * happy with a higher budget too. So
+			 * definitely increase the budget of this good
+			 * candidate to boost the disk throughput.
+			 */
+			budget = min(budget * 4, bfqd->bfq_max_budget);
+			break;
+		case BFQ_BFQQ_NO_MORE_REQUESTS:
+		       /*
+			* Leave the budget unchanged.
+			*/
+		default:
+			return;
+		}
+	} else /* async queue */
+	    /* async queues get always the maximum possible budget
+	     * (their ability to dispatch is limited by
+	     * @bfqd->bfq_max_budget_async_rq).
+	     */
+		budget = bfqd->bfq_max_budget;
+
+	bfqq->max_budget = budget;
+
+	if (bfqd->budgets_assigned >= 194 && bfqd->bfq_user_max_budget == 0 &&
+	    bfqq->max_budget > bfqd->bfq_max_budget)
+		bfqq->max_budget = bfqd->bfq_max_budget;
+
+	/*
+	 * Make sure that we have enough budget for the next request.
+	 * Since the finish time of the bfqq must be kept in sync with
+	 * the budget, be sure to call __bfq_bfqq_expire() after the
+	 * update.
+	 */
+	next_rq = bfqq->next_rq;
+	if (next_rq != NULL)
+		bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget,
+					    bfq_serv_to_charge(next_rq, bfqq));
+	else
+		bfqq->entity.budget = bfqq->max_budget;
+
+	bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %lu",
+			next_rq != NULL ? blk_rq_sectors(next_rq) : 0,
+			bfqq->entity.budget);
+}
+
+static unsigned long bfq_calc_max_budget(u64 peak_rate, u64 timeout)
+{
+	unsigned long max_budget;
+
+	/*
+	 * The max_budget calculated when autotuning is equal to the
+	 * amount of sectors transfered in timeout_sync at the
+	 * estimated peak rate.
+	 */
+	max_budget = (unsigned long)(peak_rate * 1000 *
+				     timeout >> BFQ_RATE_SHIFT);
+
+	return max_budget;
+}
+
+/*
+ * In addition to updating the peak rate, checks whether the process
+ * is "slow", and returns 1 if so. This slow flag is used, in addition
+ * to the budget timeout, to reduce the amount of service provided to
+ * seeky processes, and hence reduce their chances to lower the
+ * throughput. See the code for more details.
+ */
+static int bfq_update_peak_rate(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+				int compensate, enum bfqq_expiration reason)
+{
+	u64 bw, usecs, expected, timeout;
+	ktime_t delta;
+	int update = 0;
+
+	if (!bfq_bfqq_sync(bfqq) || bfq_bfqq_budget_new(bfqq))
+		return 0;
+
+	if (compensate)
+		delta = bfqd->last_idling_start;
+	else
+		delta = ktime_get();
+	delta = ktime_sub(delta, bfqd->last_budget_start);
+	usecs = ktime_to_us(delta);
+
+	/* Don't trust short/unrealistic values. */
+	if (usecs < 100 || usecs >= LONG_MAX)
+		return 0;
+
+	/*
+	 * Calculate the bandwidth for the last slice.  We use a 64 bit
+	 * value to store the peak rate, in sectors per usec in fixed
+	 * point math.  We do so to have enough precision in the estimate
+	 * and to avoid overflows.
+	 */
+	bw = (u64)bfqq->entity.service << BFQ_RATE_SHIFT;
+	do_div(bw, (unsigned long)usecs);
+
+	timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]);
+
+	/*
+	 * Use only long (> 20ms) intervals to filter out spikes for
+	 * the peak rate estimation.
+	 */
+	if (usecs > 20000) {
+		if (bw > bfqd->peak_rate ||
+		   (!BFQQ_SEEKY(bfqq) &&
+		    reason == BFQ_BFQQ_BUDGET_TIMEOUT)) {
+			bfq_log(bfqd, "measured bw =%llu", bw);
+			/*
+			 * To smooth oscillations use a low-pass filter with
+			 * alpha=7/8, i.e.,
+			 * new_rate = (7/8) * old_rate + (1/8) * bw
+			 */
+			do_div(bw, 8);
+			if (bw == 0)
+				return 0;
+			bfqd->peak_rate *= 7;
+			do_div(bfqd->peak_rate, 8);
+			bfqd->peak_rate += bw;
+			update = 1;
+			bfq_log(bfqd, "new peak_rate=%llu", bfqd->peak_rate);
+		}
+
+		update |= bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES - 1;
+
+		if (bfqd->peak_rate_samples < BFQ_PEAK_RATE_SAMPLES)
+			bfqd->peak_rate_samples++;
+
+		if (bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES &&
+		    update) {
+			int dev_type = blk_queue_nonrot(bfqd->queue);
+			if (bfqd->bfq_user_max_budget == 0) {
+				bfqd->bfq_max_budget =
+					bfq_calc_max_budget(bfqd->peak_rate,
+							    timeout);
+				bfq_log(bfqd, "new max_budget=%lu",
+					bfqd->bfq_max_budget);
+			}
+			if (bfqd->device_speed == BFQ_BFQD_FAST &&
+			    bfqd->peak_rate < device_speed_thresh[dev_type]) {
+				bfqd->device_speed = BFQ_BFQD_SLOW;
+				bfqd->RT_prod = R_slow[dev_type] *
+						T_slow[dev_type];
+			} else if (bfqd->device_speed == BFQ_BFQD_SLOW &&
+			    bfqd->peak_rate > device_speed_thresh[dev_type]) {
+				bfqd->device_speed = BFQ_BFQD_FAST;
+				bfqd->RT_prod = R_fast[dev_type] *
+						T_fast[dev_type];
+			}
+		}
+	}
+
+	/*
+	 * If the process has been served for a too short time
+	 * interval to let its possible sequential accesses prevail on
+	 * the initial seek time needed to move the disk head on the
+	 * first sector it requested, then give the process a chance
+	 * and for the moment return false.
+	 */
+	if (bfqq->entity.budget <= bfq_max_budget(bfqd) / 8)
+		return 0;
+
+	/*
+	 * A process is considered ``slow'' (i.e., seeky, so that we
+	 * cannot treat it fairly in the service domain, as it would
+	 * slow down too much the other processes) if, when a slice
+	 * ends for whatever reason, it has received service at a
+	 * rate that would not be high enough to complete the budget
+	 * before the budget timeout expiration.
+	 */
+	expected = bw * 1000 * timeout >> BFQ_RATE_SHIFT;
+
+	/*
+	 * Caveat: processes doing IO in the slower disk zones will
+	 * tend to be slow(er) even if not seeky. And the estimated
+	 * peak rate will actually be an average over the disk
+	 * surface. Hence, to not be too harsh with unlucky processes,
+	 * we keep a budget/3 margin of safety before declaring a
+	 * process slow.
+	 */
+	return expected > (4 * bfqq->entity.budget) / 3;
+}
+
+/*
+ * To be deemed as soft real-time, an application must meet two
+ * requirements. First, the application must not require an average
+ * bandwidth higher than the approximate bandwidth required to playback or
+ * record a compressed high-definition video.
+ * The next function is invoked on the completion of the last request of a
+ * batch, to compute the next-start time instant, soft_rt_next_start, such
+ * that, if the next request of the application does not arrive before
+ * soft_rt_next_start, then the above requirement on the bandwidth is met.
+ *
+ * The second requirement is that the request pattern of the application is
+ * isochronous, i.e., that, after issuing a request or a batch of requests,
+ * the application stops issuing new requests until all its pending requests
+ * have been completed. After that, the application may issue a new batch,
+ * and so on.
+ * For this reason the next function is invoked to compute
+ * soft_rt_next_start only for applications that meet this requirement,
+ * whereas soft_rt_next_start is set to infinity for applications that do
+ * not.
+ *
+ * Unfortunately, even a greedy application may happen to behave in an
+ * isochronous way if the CPU load is high. In fact, the application may
+ * stop issuing requests while the CPUs are busy serving other processes,
+ * then restart, then stop again for a while, and so on. In addition, if
+ * the disk achieves a low enough throughput with the request pattern
+ * issued by the application (e.g., because the request pattern is random
+ * and/or the device is slow), then the application may meet the above
+ * bandwidth requirement too. To prevent such a greedy application to be
+ * deemed as soft real-time, a further rule is used in the computation of
+ * soft_rt_next_start: soft_rt_next_start must be higher than the current
+ * time plus the maximum time for which the arrival of a request is waited
+ * for when a sync queue becomes idle, namely bfqd->bfq_slice_idle.
+ * This filters out greedy applications, as the latter issue instead their
+ * next request as soon as possible after the last one has been completed
+ * (in contrast, when a batch of requests is completed, a soft real-time
+ * application spends some time processing data).
+ *
+ * Unfortunately, the last filter may easily generate false positives if
+ * only bfqd->bfq_slice_idle is used as a reference time interval and one
+ * or both the following cases occur:
+ * 1) HZ is so low that the duration of a jiffy is comparable to or higher
+ *    than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with
+ *    HZ=100.
+ * 2) jiffies, instead of increasing at a constant rate, may stop increasing
+ *    for a while, then suddenly 'jump' by several units to recover the lost
+ *    increments. This seems to happen, e.g., inside virtual machines.
+ * To address this issue, we do not use as a reference time interval just
+ * bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In
+ * particular we add the minimum number of jiffies for which the filter
+ * seems to be quite precise also in embedded systems and KVM/QEMU virtual
+ * machines.
+ */
+static inline unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd,
+						       struct bfq_queue *bfqq)
+{
+	return max(bfqq->last_idle_bklogged +
+		   HZ * bfqq->service_from_backlogged /
+		   bfqd->bfq_wr_max_softrt_rate,
+		   jiffies + bfqq->bfqd->bfq_slice_idle + 4);
+}
+
+/*
+ * Return the largest-possible time instant such that, for as long as possible,
+ * the current time will be lower than this time instant according to the macro
+ * time_is_before_jiffies().
+ */
+static inline unsigned long bfq_infinity_from_now(unsigned long now)
+{
+	return now + ULONG_MAX / 2;
+}
+
+/**
+ * bfq_bfqq_expire - expire a queue.
+ * @bfqd: device owning the queue.
+ * @bfqq: the queue to expire.
+ * @compensate: if true, compensate for the time spent idling.
+ * @reason: the reason causing the expiration.
+ *
+ *
+ * If the process associated to the queue is slow (i.e., seeky), or in
+ * case of budget timeout, or, finally, if it is async, we
+ * artificially charge it an entire budget (independently of the
+ * actual service it received). As a consequence, the queue will get
+ * higher timestamps than the correct ones upon reactivation, and
+ * hence it will be rescheduled as if it had received more service
+ * than what it actually received. In the end, this class of processes
+ * will receive less service in proportion to how slowly they consume
+ * their budgets (and hence how seriously they tend to lower the
+ * throughput).
+ *
+ * In contrast, when a queue expires because it has been idling for
+ * too much or because it exhausted its budget, we do not touch the
+ * amount of service it has received. Hence when the queue will be
+ * reactivated and its timestamps updated, the latter will be in sync
+ * with the actual service received by the queue until expiration.
+ *
+ * Charging a full budget to the first type of queues and the exact
+ * service to the others has the effect of using the WF2Q+ policy to
+ * schedule the former on a timeslice basis, without violating the
+ * service domain guarantees of the latter.
+ */
+static void bfq_bfqq_expire(struct bfq_data *bfqd,
+			    struct bfq_queue *bfqq,
+			    int compensate,
+			    enum bfqq_expiration reason)
+{
+	int slow;
+	BUG_ON(bfqq != bfqd->in_service_queue);
+
+	/* Update disk peak rate for autotuning and check whether the
+	 * process is slow (see bfq_update_peak_rate).
+	 */
+	slow = bfq_update_peak_rate(bfqd, bfqq, compensate, reason);
+
+	/*
+	 * As above explained, 'punish' slow (i.e., seeky), timed-out
+	 * and async queues, to favor sequential sync workloads.
+	 *
+	 * Processes doing I/O in the slower disk zones will tend to be
+	 * slow(er) even if not seeky. Hence, since the estimated peak
+	 * rate is actually an average over the disk surface, these
+	 * processes may timeout just for bad luck. To avoid punishing
+	 * them we do not charge a full budget to a process that
+	 * succeeded in consuming at least 2/3 of its budget.
+	 */
+	if (slow || (reason == BFQ_BFQQ_BUDGET_TIMEOUT &&
+		     bfq_bfqq_budget_left(bfqq) >=  bfqq->entity.budget / 3))
+		bfq_bfqq_charge_full_budget(bfqq);
+
+	bfqq->service_from_backlogged += bfqq->entity.service;
+
+	if (BFQQ_SEEKY(bfqq) && reason == BFQ_BFQQ_BUDGET_TIMEOUT &&
+	    !bfq_bfqq_constantly_seeky(bfqq)) {
+		bfq_mark_bfqq_constantly_seeky(bfqq);
+		if (!blk_queue_nonrot(bfqd->queue))
+			bfqd->const_seeky_busy_in_flight_queues++;
+	}
+
+	if (reason == BFQ_BFQQ_TOO_IDLE &&
+	    bfqq->entity.service <= 2 * bfqq->entity.budget / 10 )
+		bfq_clear_bfqq_IO_bound(bfqq);
+
+	if (bfqd->low_latency && bfqq->wr_coeff == 1)
+		bfqq->last_wr_start_finish = jiffies;
+
+	if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 &&
+	    RB_EMPTY_ROOT(&bfqq->sort_list)) {
+		/*
+		 * If we get here, and there are no outstanding requests,
+		 * then the request pattern is isochronous (see the comments
+		 * to the function bfq_bfqq_softrt_next_start()). Hence we
+		 * can compute soft_rt_next_start. If, instead, the queue
+		 * still has outstanding requests, then we have to wait
+		 * for the completion of all the outstanding requests to
+		 * discover whether the request pattern is actually
+		 * isochronous.
+		 */
+		if (bfqq->dispatched == 0)
+			bfqq->soft_rt_next_start =
+				bfq_bfqq_softrt_next_start(bfqd, bfqq);
+		else {
+			/*
+			 * The application is still waiting for the
+			 * completion of one or more requests:
+			 * prevent it from possibly being incorrectly
+			 * deemed as soft real-time by setting its
+			 * soft_rt_next_start to infinity. In fact,
+			 * without this assignment, the application
+			 * would be incorrectly deemed as soft
+			 * real-time if:
+			 * 1) it issued a new request before the
+			 *    completion of all its in-flight
+			 *    requests, and
+			 * 2) at that time, its soft_rt_next_start
+			 *    happened to be in the past.
+			 */
+			bfqq->soft_rt_next_start =
+				bfq_infinity_from_now(jiffies);
+			/*
+			 * Schedule an update of soft_rt_next_start to when
+			 * the task may be discovered to be isochronous.
+			 */
+			bfq_mark_bfqq_softrt_update(bfqq);
+		}
+	}
+
+	bfq_log_bfqq(bfqd, bfqq,
+		"expire (%d, slow %d, num_disp %d, idle_win %d)", reason,
+		slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq));
+
+	/*
+	 * Increase, decrease or leave budget unchanged according to
+	 * reason.
+	 */
+	__bfq_bfqq_recalc_budget(bfqd, bfqq, reason);
+	__bfq_bfqq_expire(bfqd, bfqq);
+}
+
+/*
+ * Budget timeout is not implemented through a dedicated timer, but
+ * just checked on request arrivals and completions, as well as on
+ * idle timer expirations.
+ */
+static int bfq_bfqq_budget_timeout(struct bfq_queue *bfqq)
+{
+	if (bfq_bfqq_budget_new(bfqq) ||
+	    time_before(jiffies, bfqq->budget_timeout))
+		return 0;
+	return 1;
+}
+
+/*
+ * If we expire a queue that is waiting for the arrival of a new
+ * request, we may prevent the fictitious timestamp back-shifting that
+ * allows the guarantees of the queue to be preserved (see [1] for
+ * this tricky aspect). Hence we return true only if this condition
+ * does not hold, or if the queue is slow enough to deserve only to be
+ * kicked off for preserving a high throughput.
+*/
+static inline int bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq)
+{
+	bfq_log_bfqq(bfqq->bfqd, bfqq,
+		"may_budget_timeout: wait_request %d left %d timeout %d",
+		bfq_bfqq_wait_request(bfqq),
+			bfq_bfqq_budget_left(bfqq) >=  bfqq->entity.budget / 3,
+		bfq_bfqq_budget_timeout(bfqq));
+
+	return (!bfq_bfqq_wait_request(bfqq) ||
+		bfq_bfqq_budget_left(bfqq) >=  bfqq->entity.budget / 3)
+		&&
+		bfq_bfqq_budget_timeout(bfqq);
+}
+
+/*
+ * Device idling is allowed only for the queues for which this function
+ * returns true. For this reason, the return value of this function plays a
+ * critical role for both throughput boosting and service guarantees. The
+ * return value is computed through a logical expression. In this rather
+ * long comment, we try to briefly describe all the details and motivations
+ * behind the components of this logical expression.
+ *
+ * First, the expression is false if bfqq is not sync, or if: bfqq happened
+ * to become active during a large burst of queue activations, and the
+ * pattern of requests bfqq contains boosts the throughput if bfqq is
+ * expired. In fact, queues that became active during a large burst benefit
+ * only from throughput, as discussed in the comments to bfq_handle_burst.
+ * In this respect, expiring bfqq certainly boosts the throughput on NCQ-
+ * capable flash-based devices, whereas, on rotational devices, it boosts
+ * the throughput only if bfqq contains random requests.
+ *
+ * On the opposite end, if (a) bfqq is sync, (b) the above burst-related
+ * condition does not hold, and (c) bfqq is being weight-raised, then the
+ * expression always evaluates to true, as device idling is instrumental
+ * for preserving low-latency guarantees (see [1]). If, instead, conditions
+ * (a) and (b) do hold, but (c) does not, then the expression evaluates to
+ * true only if: (1) bfqq is I/O-bound and has a non-null idle window, and
+ * (2) at least one of the following two conditions holds.
+ * The first condition is that the device is not performing NCQ, because
+ * idling the device most certainly boosts the throughput if this condition
+ * holds and bfqq is I/O-bound and has been granted a non-null idle window.
+ * The second compound condition is made of the logical AND of two components.
+ *
+ * The first component is true only if there is no weight-raised busy
+ * queue. This guarantees that the device is not idled for a sync non-
+ * weight-raised queue when there are busy weight-raised queues. The former
+ * is then expired immediately if empty. Combined with the timestamping
+ * rules of BFQ (see [1] for details), this causes sync non-weight-raised
+ * queues to get a lower number of requests served, and hence to ask for a
+ * lower number of requests from the request pool, before the busy weight-
+ * raised queues get served again.
+ *
+ * This is beneficial for the processes associated with weight-raised
+ * queues, when the request pool is saturated (e.g., in the presence of
+ * write hogs). In fact, if the processes associated with the other queues
+ * ask for requests at a lower rate, then weight-raised processes have a
+ * higher probability to get a request from the pool immediately (or at
+ * least soon) when they need one. Hence they have a higher probability to
+ * actually get a fraction of the disk throughput proportional to their
+ * high weight. This is especially true with NCQ-capable drives, which
+ * enqueue several requests in advance and further reorder internally-
+ * queued requests.
+ *
+ * In the end, mistreating non-weight-raised queues when there are busy
+ * weight-raised queues seems to mitigate starvation problems in the
+ * presence of heavy write workloads and NCQ, and hence to guarantee a
+ * higher application and system responsiveness in these hostile scenarios.
+ *
+ * If the first component of the compound condition is instead true, i.e.,
+ * there is no weight-raised busy queue, then the second component of the
+ * compound condition takes into account service-guarantee and throughput
+ * issues related to NCQ (recall that the compound condition is evaluated
+ * only if the device is detected as supporting NCQ).
+ *
+ * As for service guarantees, allowing the drive to enqueue more than one
+ * request at a time, and hence delegating de facto final scheduling
+ * decisions to the drive's internal scheduler, causes loss of control on
+ * the actual request service order. In this respect, when the drive is
+ * allowed to enqueue more than one request at a time, the service
+ * distribution enforced by the drive's internal scheduler is likely to
+ * coincide with the desired device-throughput distribution only in the
+ * following, perfectly symmetric, scenario:
+ * 1) all active queues have the same weight,
+ * 2) all active groups at the same level in the groups tree have the same
+ *    weight,
+ * 3) all active groups at the same level in the groups tree have the same
+ *    number of children.
+ *
+ * Even in such a scenario, sequential I/O may still receive a preferential
+ * treatment, but this is not likely to be a big issue with flash-based
+ * devices, because of their non-dramatic loss of throughput with random
+ * I/O. Things do differ with HDDs, for which additional care is taken, as
+ * explained after completing the discussion for flash-based devices.
+ *
+ * Unfortunately, keeping the necessary state for evaluating exactly the
+ * above symmetry conditions would be quite complex and time-consuming.
+ * Therefore BFQ evaluates instead the following stronger sub-conditions,
+ * for which it is much easier to maintain the needed state:
+ * 1) all active queues have the same weight,
+ * 2) all active groups have the same weight,
+ * 3) all active groups have at most one active child each.
+ * In particular, the last two conditions are always true if hierarchical
+ * support and the cgroups interface are not enabled, hence no state needs
+ * to be maintained in this case.
+ *
+ * According to the above considerations, the second component of the
+ * compound condition evaluates to true if any of the above symmetry
+ * sub-condition does not hold, or the device is not flash-based. Therefore,
+ * if also the first component is true, then idling is allowed for a sync
+ * queue. These are the only sub-conditions considered if the device is
+ * flash-based, as, for such a device, it is sensible to force idling only
+ * for service-guarantee issues. In fact, as for throughput, idling
+ * NCQ-capable flash-based devices would not boost the throughput even
+ * with sequential I/O; rather it would lower the throughput in proportion
+ * to how fast the device is. In the end, (only) if all the three
+ * sub-conditions hold and the device is flash-based, the compound
+ * condition evaluates to false and therefore no idling is performed.
+ *
+ * As already said, things change with a rotational device, where idling
+ * boosts the throughput with sequential I/O (even with NCQ). Hence, for
+ * such a device the second component of the compound condition evaluates
+ * to true also if the following additional sub-condition does not hold:
+ * the queue is constantly seeky. Unfortunately, this different behavior
+ * with respect to flash-based devices causes an additional asymmetry: if
+ * some sync queues enjoy idling and some other sync queues do not, then
+ * the latter get a low share of the device throughput, simply because the
+ * former get many requests served after being set as in service, whereas
+ * the latter do not. As a consequence, to guarantee the desired throughput
+ * distribution, on HDDs the compound expression evaluates to true (and
+ * hence device idling is performed) also if the following last symmetry
+ * condition does not hold: no other queue is benefiting from idling. Also
+ * this last condition is actually replaced with a simpler-to-maintain and
+ * stronger condition: there is no busy queue which is not constantly seeky
+ * (and hence may also benefit from idling).
+ *
+ * To sum up, when all the required symmetry and throughput-boosting
+ * sub-conditions hold, the second component of the compound condition
+ * evaluates to false, and hence no idling is performed. This helps to
+ * keep the drives' internal queues full on NCQ-capable devices, and hence
+ * to boost the throughput, without causing 'almost' any loss of service
+ * guarantees. The 'almost' follows from the fact that, if the internal
+ * queue of one such device is filled while all the sub-conditions hold,
+ * but at some point in time some sub-condition stops to hold, then it may
+ * become impossible to let requests be served in the new desired order
+ * until all the requests already queued in the device have been served.
+ */
+static inline bool bfq_bfqq_must_not_expire(struct bfq_queue *bfqq)
+{
+	struct bfq_data *bfqd = bfqq->bfqd;
+#ifdef CONFIG_CGROUP_BFQIO
+#define symmetric_scenario	  (!bfqd->active_numerous_groups && \
+				   !bfq_differentiated_weights(bfqd))
+#else
+#define symmetric_scenario	  (!bfq_differentiated_weights(bfqd))
+#endif
+#define cond_for_seeky_on_ncq_hdd (bfq_bfqq_constantly_seeky(bfqq) && \
+				   bfqd->busy_in_flight_queues == \
+				   bfqd->const_seeky_busy_in_flight_queues)
+
+#define cond_for_expiring_in_burst	(bfq_bfqq_in_large_burst(bfqq) && \
+					 bfqd->hw_tag && \
+					 (blk_queue_nonrot(bfqd->queue) || \
+					  bfq_bfqq_constantly_seeky(bfqq)))
+
+/*
+ * Condition for expiring a non-weight-raised queue (and hence not idling
+ * the device).
+ */
+#define cond_for_expiring_non_wr  (bfqd->hw_tag && \
+				   (bfqd->wr_busy_queues > 0 || \
+				    (symmetric_scenario && \
+				     (blk_queue_nonrot(bfqd->queue) || \
+				      cond_for_seeky_on_ncq_hdd))))
+
+	return bfq_bfqq_sync(bfqq) &&
+		!cond_for_expiring_in_burst &&
+		(bfqq->wr_coeff > 1 ||
+		 (bfq_bfqq_IO_bound(bfqq) && bfq_bfqq_idle_window(bfqq) &&
+		  !cond_for_expiring_non_wr)
+	);
+}
+
+/*
+ * If the in-service queue is empty but sync, and the function
+ * bfq_bfqq_must_not_expire returns true, then:
+ * 1) the queue must remain in service and cannot be expired, and
+ * 2) the disk must be idled to wait for the possible arrival of a new
+ *    request for the queue.
+ * See the comments to the function bfq_bfqq_must_not_expire for the reasons
+ * why performing device idling is the best choice to boost the throughput
+ * and preserve service guarantees when bfq_bfqq_must_not_expire itself
+ * returns true.
+ */
+static inline bool bfq_bfqq_must_idle(struct bfq_queue *bfqq)
+{
+	struct bfq_data *bfqd = bfqq->bfqd;
+
+	return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 &&
+	       bfq_bfqq_must_not_expire(bfqq);
+}
+
+/*
+ * Select a queue for service.  If we have a current queue in service,
+ * check whether to continue servicing it, or retrieve and set a new one.
+ */
+static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
+{
+	struct bfq_queue *bfqq;
+	struct request *next_rq;
+	enum bfqq_expiration reason = BFQ_BFQQ_BUDGET_TIMEOUT;
+
+	bfqq = bfqd->in_service_queue;
+	if (bfqq == NULL)
+		goto new_queue;
+
+	bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue");
+
+	if (bfq_may_expire_for_budg_timeout(bfqq) &&
+	    !timer_pending(&bfqd->idle_slice_timer) &&
+	    !bfq_bfqq_must_idle(bfqq))
+		goto expire;
+
+	next_rq = bfqq->next_rq;
+	/*
+	 * If bfqq has requests queued and it has enough budget left to
+	 * serve them, keep the queue, otherwise expire it.
+	 */
+	if (next_rq != NULL) {
+		if (bfq_serv_to_charge(next_rq, bfqq) >
+			bfq_bfqq_budget_left(bfqq)) {
+			reason = BFQ_BFQQ_BUDGET_EXHAUSTED;
+			goto expire;
+		} else {
+			/*
+			 * The idle timer may be pending because we may
+			 * not disable disk idling even when a new request
+			 * arrives.
+			 */
+			if (timer_pending(&bfqd->idle_slice_timer)) {
+				/*
+				 * If we get here: 1) at least a new request
+				 * has arrived but we have not disabled the
+				 * timer because the request was too small,
+				 * 2) then the block layer has unplugged
+				 * the device, causing the dispatch to be
+				 * invoked.
+				 *
+				 * Since the device is unplugged, now the
+				 * requests are probably large enough to
+				 * provide a reasonable throughput.
+				 * So we disable idling.
+				 */
+				bfq_clear_bfqq_wait_request(bfqq);
+				del_timer(&bfqd->idle_slice_timer);
+			}
+			goto keep_queue;
+		}
+	}
+
+	/*
+	 * No requests pending.  If the in-service queue still has requests
+	 * in flight (possibly waiting for a completion) or is idling for a
+	 * new request, then keep it.
+	 */
+	if (timer_pending(&bfqd->idle_slice_timer) ||
+	    (bfqq->dispatched != 0 && bfq_bfqq_must_not_expire(bfqq))) {
+		bfqq = NULL;
+		goto keep_queue;
+	}
+
+	reason = BFQ_BFQQ_NO_MORE_REQUESTS;
+expire:
+	bfq_bfqq_expire(bfqd, bfqq, 0, reason);
+new_queue:
+	bfqq = bfq_set_in_service_queue(bfqd);
+	bfq_log(bfqd, "select_queue: new queue %d returned",
+		bfqq != NULL ? bfqq->pid : 0);
+keep_queue:
+	return bfqq;
+}
+
+static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+{
+	struct bfq_entity *entity = &bfqq->entity;
+	if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */
+		bfq_log_bfqq(bfqd, bfqq,
+			"raising period dur %u/%u msec, old coeff %u, w %d(%d)",
+			jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
+			jiffies_to_msecs(bfqq->wr_cur_max_time),
+			bfqq->wr_coeff,
+			bfqq->entity.weight, bfqq->entity.orig_weight);
+
+		BUG_ON(bfqq != bfqd->in_service_queue && entity->weight !=
+		       entity->orig_weight * bfqq->wr_coeff);
+		if (entity->ioprio_changed)
+			bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change");
+
+		/*
+		 * If the queue was activated in a burst, or
+		 * too much time has elapsed from the beginning
+		 * of this weight-raising period, or the queue has
+		 * exceeded the acceptable number of cooperations,
+		 * then end weight raising.
+		 */
+		if (bfq_bfqq_in_large_burst(bfqq) ||
+		    bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh ||
+		    time_is_before_jiffies(bfqq->last_wr_start_finish +
+					   bfqq->wr_cur_max_time)) {
+			bfqq->last_wr_start_finish = jiffies;
+			bfq_log_bfqq(bfqd, bfqq,
+				     "wrais ending at %lu, rais_max_time %u",
+				     bfqq->last_wr_start_finish,
+				     jiffies_to_msecs(bfqq->wr_cur_max_time));
+			bfq_bfqq_end_wr(bfqq);
+		}
+	}
+	/* Update weight both if it must be raised and if it must be lowered */
+	if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1))
+		__bfq_entity_update_weight_prio(
+			bfq_entity_service_tree(entity),
+			entity);
+}
+
+/*
+ * Dispatch one request from bfqq, moving it to the request queue
+ * dispatch list.
+ */
+static int bfq_dispatch_request(struct bfq_data *bfqd,
+				struct bfq_queue *bfqq)
+{
+	int dispatched = 0;
+	struct request *rq;
+	unsigned long service_to_charge;
+
+	BUG_ON(RB_EMPTY_ROOT(&bfqq->sort_list));
+
+	/* Follow expired path, else get first next available. */
+	rq = bfq_check_fifo(bfqq);
+	if (rq == NULL)
+		rq = bfqq->next_rq;
+	service_to_charge = bfq_serv_to_charge(rq, bfqq);
+
+	if (service_to_charge > bfq_bfqq_budget_left(bfqq)) {
+		/*
+		 * This may happen if the next rq is chosen in fifo order
+		 * instead of sector order. The budget is properly
+		 * dimensioned to be always sufficient to serve the next
+		 * request only if it is chosen in sector order. The reason
+		 * is that it would be quite inefficient and little useful
+		 * to always make sure that the budget is large enough to
+		 * serve even the possible next rq in fifo order.
+		 * In fact, requests are seldom served in fifo order.
+		 *
+		 * Expire the queue for budget exhaustion, and make sure
+		 * that the next act_budget is enough to serve the next
+		 * request, even if it comes from the fifo expired path.
+		 */
+		bfqq->next_rq = rq;
+		/*
+		 * Since this dispatch is failed, make sure that
+		 * a new one will be performed
+		 */
+		if (!bfqd->rq_in_driver)
+			bfq_schedule_dispatch(bfqd);
+		goto expire;
+	}
+
+	/* Finally, insert request into driver dispatch list. */
+	bfq_bfqq_served(bfqq, service_to_charge);
+	bfq_dispatch_insert(bfqd->queue, rq);
+
+	bfq_update_wr_data(bfqd, bfqq);
+
+	bfq_log_bfqq(bfqd, bfqq,
+			"dispatched %u sec req (%llu), budg left %lu",
+			blk_rq_sectors(rq),
+			(long long unsigned)blk_rq_pos(rq),
+			bfq_bfqq_budget_left(bfqq));
+
+	dispatched++;
+
+	if (bfqd->in_service_bic == NULL) {
+		atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount);
+		bfqd->in_service_bic = RQ_BIC(rq);
+	}
+
+	if (bfqd->busy_queues > 1 && ((!bfq_bfqq_sync(bfqq) &&
+	    dispatched >= bfqd->bfq_max_budget_async_rq) ||
+	    bfq_class_idle(bfqq)))
+		goto expire;
+
+	return dispatched;
+
+expire:
+	bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_EXHAUSTED);
+	return dispatched;
+}
+
+static int __bfq_forced_dispatch_bfqq(struct bfq_queue *bfqq)
+{
+	int dispatched = 0;
+
+	while (bfqq->next_rq != NULL) {
+		bfq_dispatch_insert(bfqq->bfqd->queue, bfqq->next_rq);
+		dispatched++;
+	}
+
+	BUG_ON(!list_empty(&bfqq->fifo));
+	return dispatched;
+}
+
+/*
+ * Drain our current requests.
+ * Used for barriers and when switching io schedulers on-the-fly.
+ */
+static int bfq_forced_dispatch(struct bfq_data *bfqd)
+{
+	struct bfq_queue *bfqq, *n;
+	struct bfq_service_tree *st;
+	int dispatched = 0;
+
+	bfqq = bfqd->in_service_queue;
+	if (bfqq != NULL)
+		__bfq_bfqq_expire(bfqd, bfqq);
+
+	/*
+	 * Loop through classes, and be careful to leave the scheduler
+	 * in a consistent state, as feedback mechanisms and vtime
+	 * updates cannot be disabled during the process.
+	 */
+	list_for_each_entry_safe(bfqq, n, &bfqd->active_list, bfqq_list) {
+		st = bfq_entity_service_tree(&bfqq->entity);
+
+		dispatched += __bfq_forced_dispatch_bfqq(bfqq);
+		bfqq->max_budget = bfq_max_budget(bfqd);
+
+		bfq_forget_idle(st);
+	}
+
+	BUG_ON(bfqd->busy_queues != 0);
+
+	return dispatched;
+}
+
+static int bfq_dispatch_requests(struct request_queue *q, int force)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+	struct bfq_queue *bfqq;
+	int max_dispatch;
+
+	bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues);
+	if (bfqd->busy_queues == 0)
+		return 0;
+
+	if (unlikely(force))
+		return bfq_forced_dispatch(bfqd);
+
+	bfqq = bfq_select_queue(bfqd);
+	if (bfqq == NULL)
+		return 0;
+
+	max_dispatch = bfqd->bfq_quantum;
+	if (bfq_class_idle(bfqq))
+		max_dispatch = 1;
+
+	if (!bfq_bfqq_sync(bfqq))
+		max_dispatch = bfqd->bfq_max_budget_async_rq;
+
+	if (bfqq->dispatched >= max_dispatch) {
+		if (bfqd->busy_queues > 1)
+			return 0;
+		if (bfqq->dispatched >= 4 * max_dispatch)
+			return 0;
+	}
+
+	if (bfqd->sync_flight != 0 && !bfq_bfqq_sync(bfqq))
+		return 0;
+
+	bfq_clear_bfqq_wait_request(bfqq);
+	BUG_ON(timer_pending(&bfqd->idle_slice_timer));
+
+	if (!bfq_dispatch_request(bfqd, bfqq))
+		return 0;
+
+	bfq_log_bfqq(bfqd, bfqq, "dispatched one request of %d (max_disp %d)",
+			bfqq->pid, max_dispatch);
+
+	return 1;
+}
+
+/*
+ * Task holds one reference to the queue, dropped when task exits.  Each rq
+ * in-flight on this queue also holds a reference, dropped when rq is freed.
+ *
+ * Queue lock must be held here.
+ */
+static void bfq_put_queue(struct bfq_queue *bfqq)
+{
+	struct bfq_data *bfqd = bfqq->bfqd;
+
+	BUG_ON(atomic_read(&bfqq->ref) <= 0);
+
+	bfq_log_bfqq(bfqd, bfqq, "put_queue: %p %d", bfqq,
+		     atomic_read(&bfqq->ref));
+	if (!atomic_dec_and_test(&bfqq->ref))
+		return;
+
+	BUG_ON(rb_first(&bfqq->sort_list) != NULL);
+	BUG_ON(bfqq->allocated[READ] + bfqq->allocated[WRITE] != 0);
+	BUG_ON(bfqq->entity.tree != NULL);
+	BUG_ON(bfq_bfqq_busy(bfqq));
+	BUG_ON(bfqd->in_service_queue == bfqq);
+
+	if (bfq_bfqq_sync(bfqq))
+		/*
+		 * The fact that this queue is being destroyed does not
+		 * invalidate the fact that this queue may have been
+		 * activated during the current burst. As a consequence,
+		 * although the queue does not exist anymore, and hence
+		 * needs to be removed from the burst list if there,
+		 * the burst size has not to be decremented.
+		 */
+		hlist_del_init(&bfqq->burst_list_node);
+
+	bfq_log_bfqq(bfqd, bfqq, "put_queue: %p freed", bfqq);
+
+	kmem_cache_free(bfq_pool, bfqq);
+}
+
+static void bfq_put_cooperator(struct bfq_queue *bfqq)
+{
+	struct bfq_queue *__bfqq, *next;
+
+	/*
+	 * If this queue was scheduled to merge with another queue, be
+	 * sure to drop the reference taken on that queue (and others in
+	 * the merge chain). See bfq_setup_merge and bfq_merge_bfqqs.
+	 */
+	__bfqq = bfqq->new_bfqq;
+	while (__bfqq) {
+		if (__bfqq == bfqq)
+			break;
+		next = __bfqq->new_bfqq;
+		bfq_put_queue(__bfqq);
+		__bfqq = next;
+	}
+}
+
+static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+{
+	if (bfqq == bfqd->in_service_queue) {
+		__bfq_bfqq_expire(bfqd, bfqq);
+		bfq_schedule_dispatch(bfqd);
+	}
+
+	bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq,
+		     atomic_read(&bfqq->ref));
+
+	bfq_put_cooperator(bfqq);
+
+	bfq_put_queue(bfqq);
+}
+
+static inline void bfq_init_icq(struct io_cq *icq)
+{
+	struct bfq_io_cq *bic = icq_to_bic(icq);
+
+	bic->ttime.last_end_request = jiffies;
+	/*
+	 * A newly created bic indicates that the process has just
+	 * started doing I/O, and is probably mapping into memory its
+	 * executable and libraries: it definitely needs weight raising.
+	 * There is however the possibility that the process performs,
+	 * for a while, I/O close to some other process. EQM intercepts
+	 * this behavior and may merge the queue corresponding to the
+	 * process  with some other queue, BEFORE the weight of the queue
+	 * is raised. Merged queues are not weight-raised (they are assumed
+	 * to belong to processes that benefit only from high throughput).
+	 * If the merge is basically the consequence of an accident, then
+	 * the queue will be split soon and will get back its old weight.
+	 * It is then important to write down somewhere that this queue
+	 * does need weight raising, even if it did not make it to get its
+	 * weight raised before being merged. To this purpose, we overload
+	 * the field raising_time_left and assign 1 to it, to mark the queue
+	 * as needing weight raising.
+	 */
+	bic->wr_time_left = 1;
+}
+
+static void bfq_exit_icq(struct io_cq *icq)
+{
+	struct bfq_io_cq *bic = icq_to_bic(icq);
+	struct bfq_data *bfqd = bic_to_bfqd(bic);
+
+	if (bic->bfqq[BLK_RW_ASYNC]) {
+		bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_ASYNC]);
+		bic->bfqq[BLK_RW_ASYNC] = NULL;
+	}
+
+	if (bic->bfqq[BLK_RW_SYNC]) {
+		/*
+		 * If the bic is using a shared queue, put the reference
+		 * taken on the io_context when the bic started using a
+		 * shared bfq_queue.
+		 */
+		if (bfq_bfqq_coop(bic->bfqq[BLK_RW_SYNC]))
+			put_io_context(icq->ioc);
+		bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_SYNC]);
+		bic->bfqq[BLK_RW_SYNC] = NULL;
+	}
+}
+
+/*
+ * Update the entity prio values; note that the new values will not
+ * be used until the next (re)activation.
+ */
+static void bfq_init_prio_data(struct bfq_queue *bfqq, struct io_context *ioc)
+{
+	struct task_struct *tsk = current;
+	int ioprio_class;
+
+	if (!bfq_bfqq_prio_changed(bfqq))
+		return;
+
+	ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
+	switch (ioprio_class) {
+	default:
+		dev_err(bfqq->bfqd->queue->backing_dev_info.dev,
+			"bfq: bad prio class %d\n", ioprio_class);
+	case IOPRIO_CLASS_NONE:
+		/*
+		 * No prio set, inherit CPU scheduling settings.
+		 */
+		bfqq->entity.new_ioprio = task_nice_ioprio(tsk);
+		bfqq->entity.new_ioprio_class = task_nice_ioclass(tsk);
+		break;
+	case IOPRIO_CLASS_RT:
+		bfqq->entity.new_ioprio = task_ioprio(ioc);
+		bfqq->entity.new_ioprio_class = IOPRIO_CLASS_RT;
+		break;
+	case IOPRIO_CLASS_BE:
+		bfqq->entity.new_ioprio = task_ioprio(ioc);
+		bfqq->entity.new_ioprio_class = IOPRIO_CLASS_BE;
+		break;
+	case IOPRIO_CLASS_IDLE:
+		bfqq->entity.new_ioprio_class = IOPRIO_CLASS_IDLE;
+		bfqq->entity.new_ioprio = 7;
+		bfq_clear_bfqq_idle_window(bfqq);
+		break;
+	}
+
+	if (bfqq->entity.new_ioprio < 0 ||
+	    bfqq->entity.new_ioprio >= IOPRIO_BE_NR) {
+		printk(KERN_CRIT "bfq_init_prio_data: new_ioprio %d\n",
+				 bfqq->entity.new_ioprio);
+		BUG();
+	}
+
+	bfqq->entity.ioprio_changed = 1;
+
+	bfq_clear_bfqq_prio_changed(bfqq);
+}
+
+static void bfq_changed_ioprio(struct io_context *ioc,
+			       struct bfq_io_cq *bic)
+{
+	struct bfq_data *bfqd;
+	struct bfq_queue *bfqq, *new_bfqq;
+	struct bfq_group *bfqg;
+	unsigned long uninitialized_var(flags);
+
+	bfqd = bfq_get_bfqd_locked(&(bic->icq.q->elevator->elevator_data),
+				   &flags);
+	if (unlikely(bfqd == NULL))
+		return;
+
+	bfqq = bic->bfqq[BLK_RW_ASYNC];
+	if (bfqq != NULL) {
+		bfqg = container_of(bfqq->entity.sched_data, struct bfq_group,
+				    sched_data);
+		new_bfqq = bfq_get_queue(bfqd, bfqg, BLK_RW_ASYNC, bic->icq.ioc,
+					 GFP_ATOMIC);
+		if (new_bfqq != NULL) {
+			bic->bfqq[BLK_RW_ASYNC] = new_bfqq;
+			bfq_log_bfqq(bfqd, bfqq,
+				     "changed_ioprio: bfqq %p %d",
+				     bfqq, atomic_read(&bfqq->ref));
+			bfq_put_queue(bfqq);
+		}
+	}
+
+	bfqq = bic->bfqq[BLK_RW_SYNC];
+	if (bfqq != NULL)
+		bfq_mark_bfqq_prio_changed(bfqq);
+
+	bfq_put_bfqd_unlock(bfqd, &flags);
+}
+
+static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+			  pid_t pid, int is_sync)
+{
+	RB_CLEAR_NODE(&bfqq->entity.rb_node);
+	INIT_LIST_HEAD(&bfqq->fifo);
+	INIT_HLIST_NODE(&bfqq->burst_list_node);
+
+	atomic_set(&bfqq->ref, 0);
+	bfqq->bfqd = bfqd;
+
+	bfq_mark_bfqq_prio_changed(bfqq);
+
+	if (is_sync) {
+		if (!bfq_class_idle(bfqq))
+			bfq_mark_bfqq_idle_window(bfqq);
+		bfq_mark_bfqq_sync(bfqq);
+	}
+	bfq_mark_bfqq_IO_bound(bfqq);
+
+	/* Tentative initial value to trade off between thr and lat */
+	bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3;
+	bfqq->pid = pid;
+
+	bfqq->wr_coeff = 1;
+	bfqq->last_wr_start_finish = 0;
+	/*
+	 * Set to the value for which bfqq will not be deemed as
+	 * soft rt when it becomes backlogged.
+	 */
+	bfqq->soft_rt_next_start = bfq_infinity_from_now(jiffies);
+}
+
+static struct bfq_queue *bfq_find_alloc_queue(struct bfq_data *bfqd,
+					      struct bfq_group *bfqg,
+					      int is_sync,
+					      struct io_context *ioc,
+					      gfp_t gfp_mask)
+{
+	struct bfq_queue *bfqq, *new_bfqq = NULL;
+	struct bfq_io_cq *bic;
+
+retry:
+	bic = bfq_bic_lookup(bfqd, ioc);
+	/* bic always exists here */
+	bfqq = bic_to_bfqq(bic, is_sync);
+
+	/*
+	 * Always try a new alloc if we fall back to the OOM bfqq
+	 * originally, since it should just be a temporary situation.
+	 */
+	if (bfqq == NULL || bfqq == &bfqd->oom_bfqq) {
+		bfqq = NULL;
+		if (new_bfqq != NULL) {
+			bfqq = new_bfqq;
+			new_bfqq = NULL;
+		} else if (gfp_mask & __GFP_WAIT) {
+			spin_unlock_irq(bfqd->queue->queue_lock);
+			new_bfqq = kmem_cache_alloc_node(bfq_pool,
+					gfp_mask | __GFP_ZERO,
+					bfqd->queue->node);
+			spin_lock_irq(bfqd->queue->queue_lock);
+			if (new_bfqq != NULL)
+				goto retry;
+		} else {
+			bfqq = kmem_cache_alloc_node(bfq_pool,
+					gfp_mask | __GFP_ZERO,
+					bfqd->queue->node);
+		}
+
+		if (bfqq != NULL) {
+			bfq_init_bfqq(bfqd, bfqq, current->pid, is_sync);
+			bfq_init_prio_data(bfqq, ioc);
+			bfq_init_entity(&bfqq->entity, bfqg);
+			bfq_log_bfqq(bfqd, bfqq, "allocated");
+		} else {
+			bfqq = &bfqd->oom_bfqq;
+			bfq_log_bfqq(bfqd, bfqq, "using oom bfqq");
+		}
+	}
+
+	if (new_bfqq != NULL)
+		kmem_cache_free(bfq_pool, new_bfqq);
+
+	return bfqq;
+}
+
+static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd,
+					       struct bfq_group *bfqg,
+					       int ioprio_class, int ioprio)
+{
+	switch (ioprio_class) {
+	case IOPRIO_CLASS_RT:
+		return &bfqg->async_bfqq[0][ioprio];
+	case IOPRIO_CLASS_BE:
+		return &bfqg->async_bfqq[1][ioprio];
+	case IOPRIO_CLASS_IDLE:
+		return &bfqg->async_idle_bfqq;
+	default:
+		BUG();
+	}
+}
+
+static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
+				       struct bfq_group *bfqg, int is_sync,
+				       struct io_context *ioc, gfp_t gfp_mask)
+{
+	const int ioprio = task_ioprio(ioc);
+	const int ioprio_class = task_ioprio_class(ioc);
+	struct bfq_queue **async_bfqq = NULL;
+	struct bfq_queue *bfqq = NULL;
+
+	if (!is_sync) {
+		async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class,
+						  ioprio);
+		bfqq = *async_bfqq;
+	}
+
+	if (bfqq == NULL)
+		bfqq = bfq_find_alloc_queue(bfqd, bfqg, is_sync, ioc, gfp_mask);
+
+	/*
+	 * Pin the queue now that it's allocated, scheduler exit will
+	 * prune it.
+	 */
+	if (!is_sync && *async_bfqq == NULL) {
+		atomic_inc(&bfqq->ref);
+		bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d",
+			     bfqq, atomic_read(&bfqq->ref));
+		*async_bfqq = bfqq;
+	}
+
+	atomic_inc(&bfqq->ref);
+	bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq,
+		     atomic_read(&bfqq->ref));
+	return bfqq;
+}
+
+static void bfq_update_io_thinktime(struct bfq_data *bfqd,
+				    struct bfq_io_cq *bic)
+{
+	unsigned long elapsed = jiffies - bic->ttime.last_end_request;
+	unsigned long ttime = min(elapsed, 2UL * bfqd->bfq_slice_idle);
+
+	bic->ttime.ttime_samples = (7*bic->ttime.ttime_samples + 256) / 8;
+	bic->ttime.ttime_total = (7*bic->ttime.ttime_total + 256*ttime) / 8;
+	bic->ttime.ttime_mean = (bic->ttime.ttime_total + 128) /
+				bic->ttime.ttime_samples;
+}
+
+static void bfq_update_io_seektime(struct bfq_data *bfqd,
+				   struct bfq_queue *bfqq,
+				   struct request *rq)
+{
+	sector_t sdist;
+	u64 total;
+
+	if (bfqq->last_request_pos < blk_rq_pos(rq))
+		sdist = blk_rq_pos(rq) - bfqq->last_request_pos;
+	else
+		sdist = bfqq->last_request_pos - blk_rq_pos(rq);
+
+	/*
+	 * Don't allow the seek distance to get too large from the
+	 * odd fragment, pagein, etc.
+	 */
+	if (bfqq->seek_samples == 0) /* first request, not really a seek */
+		sdist = 0;
+	else if (bfqq->seek_samples <= 60) /* second & third seek */
+		sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*1024);
+	else
+		sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*64);
+
+	bfqq->seek_samples = (7*bfqq->seek_samples + 256) / 8;
+	bfqq->seek_total = (7*bfqq->seek_total + (u64)256*sdist) / 8;
+	total = bfqq->seek_total + (bfqq->seek_samples/2);
+	do_div(total, bfqq->seek_samples);
+	bfqq->seek_mean = (sector_t)total;
+
+	bfq_log_bfqq(bfqd, bfqq, "dist=%llu mean=%llu", (u64)sdist,
+			(u64)bfqq->seek_mean);
+}
+
+/*
+ * Disable idle window if the process thinks too long or seeks so much that
+ * it doesn't matter.
+ */
+static void bfq_update_idle_window(struct bfq_data *bfqd,
+				   struct bfq_queue *bfqq,
+				   struct bfq_io_cq *bic)
+{
+	int enable_idle;
+
+	/* Don't idle for async or idle io prio class. */
+	if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq))
+		return;
+
+	/* Idle window just restored, statistics are meaningless. */
+	if (bfq_bfqq_just_split(bfqq))
+		return;
+
+	enable_idle = bfq_bfqq_idle_window(bfqq);
+
+	if (atomic_read(&bic->icq.ioc->nr_tasks) == 0 ||
+	    bfqd->bfq_slice_idle == 0 ||
+		(bfqd->hw_tag && BFQQ_SEEKY(bfqq) &&
+			bfqq->wr_coeff == 1))
+		enable_idle = 0;
+	else if (bfq_sample_valid(bic->ttime.ttime_samples)) {
+		if (bic->ttime.ttime_mean > bfqd->bfq_slice_idle &&
+			bfqq->wr_coeff == 1)
+			enable_idle = 0;
+		else
+			enable_idle = 1;
+	}
+	bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d",
+		enable_idle);
+
+	if (enable_idle)
+		bfq_mark_bfqq_idle_window(bfqq);
+	else
+		bfq_clear_bfqq_idle_window(bfqq);
+}
+
+/*
+ * Called when a new fs request (rq) is added to bfqq.  Check if there's
+ * something we should do about it.
+ */
+static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+			    struct request *rq)
+{
+	struct bfq_io_cq *bic = RQ_BIC(rq);
+
+	if (rq->cmd_flags & REQ_META)
+		bfqq->meta_pending++;
+
+	bfq_update_io_thinktime(bfqd, bic);
+	bfq_update_io_seektime(bfqd, bfqq, rq);
+	if (!BFQQ_SEEKY(bfqq) && bfq_bfqq_constantly_seeky(bfqq)) {
+		bfq_clear_bfqq_constantly_seeky(bfqq);
+		if (!blk_queue_nonrot(bfqd->queue)) {
+			BUG_ON(!bfqd->const_seeky_busy_in_flight_queues);
+			bfqd->const_seeky_busy_in_flight_queues--;
+		}
+	}
+	if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 ||
+	    !BFQQ_SEEKY(bfqq))
+		bfq_update_idle_window(bfqd, bfqq, bic);
+	bfq_clear_bfqq_just_split(bfqq);
+
+	bfq_log_bfqq(bfqd, bfqq,
+		     "rq_enqueued: idle_window=%d (seeky %d, mean %llu)",
+		     bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq),
+		     (long long unsigned)bfqq->seek_mean);
+
+	bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
+
+	if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) {
+		int small_req = bfqq->queued[rq_is_sync(rq)] == 1 &&
+				blk_rq_sectors(rq) < 32;
+		int budget_timeout = bfq_bfqq_budget_timeout(bfqq);
+
+		/*
+		 * There is just this request queued: if the request
+		 * is small and the queue is not to be expired, then
+		 * just exit.
+		 *
+		 * In this way, if the disk is being idled to wait for
+		 * a new request from the in-service queue, we avoid
+		 * unplugging the device and committing the disk to serve
+		 * just a small request. On the contrary, we wait for
+		 * the block layer to decide when to unplug the device:
+		 * hopefully, new requests will be merged to this one
+		 * quickly, then the device will be unplugged and
+		 * larger requests will be dispatched.
+		 */
+		if (small_req && !budget_timeout)
+			return;
+
+		/*
+		 * A large enough request arrived, or the queue is to
+		 * be expired: in both cases disk idling is to be
+		 * stopped, so clear wait_request flag and reset
+		 * timer.
+		 */
+		bfq_clear_bfqq_wait_request(bfqq);
+		del_timer(&bfqd->idle_slice_timer);
+
+		/*
+		 * The queue is not empty, because a new request just
+		 * arrived. Hence we can safely expire the queue, in
+		 * case of budget timeout, without risking that the
+		 * timestamps of the queue are not updated correctly.
+		 * See [1] for more details.
+		 */
+		if (budget_timeout)
+			bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_TIMEOUT);
+
+		/*
+		 * Let the request rip immediately, or let a new queue be
+		 * selected if bfqq has just been expired.
+		 */
+		__blk_run_queue(bfqd->queue);
+	}
+}
+
+static void bfq_insert_request(struct request_queue *q, struct request *rq)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+	struct bfq_queue *bfqq = RQ_BFQQ(rq), *new_bfqq;
+
+	assert_spin_locked(bfqd->queue->queue_lock);
+
+	/*
+	 * An unplug may trigger a requeue of a request from the device
+	 * driver: make sure we are in process context while trying to
+	 * merge two bfq_queues.
+	 */
+	if (!in_interrupt()) {
+		new_bfqq = bfq_setup_cooperator(bfqd, bfqq, rq, true);
+		if (new_bfqq != NULL) {
+			if (bic_to_bfqq(RQ_BIC(rq), 1) != bfqq)
+				new_bfqq = bic_to_bfqq(RQ_BIC(rq), 1);
+			/*
+			 * Release the request's reference to the old bfqq
+			 * and make sure one is taken to the shared queue.
+			 */
+			new_bfqq->allocated[rq_data_dir(rq)]++;
+			bfqq->allocated[rq_data_dir(rq)]--;
+			atomic_inc(&new_bfqq->ref);
+			bfq_put_queue(bfqq);
+			if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq)
+				bfq_merge_bfqqs(bfqd, RQ_BIC(rq),
+						bfqq, new_bfqq);
+			rq->elv.priv[1] = new_bfqq;
+			bfqq = new_bfqq;
+		} else
+			bfq_bfqq_increase_failed_cooperations(bfqq);
+	}
+
+	bfq_init_prio_data(bfqq, RQ_BIC(rq)->icq.ioc);
+
+	bfq_add_request(rq);
+
+	/*
+	 * Here a newly-created bfq_queue has already started a weight-raising
+	 * period: clear raising_time_left to prevent bfq_bfqq_save_state()
+	 * from assigning it a full weight-raising period. See the detailed
+	 * comments about this field in bfq_init_icq().
+	 */
+	if (bfqq->bic != NULL)
+		bfqq->bic->wr_time_left = 0;
+	rq_set_fifo_time(rq, jiffies + bfqd->bfq_fifo_expire[rq_is_sync(rq)]);
+	list_add_tail(&rq->queuelist, &bfqq->fifo);
+
+	bfq_rq_enqueued(bfqd, bfqq, rq);
+}
+
+static void bfq_update_hw_tag(struct bfq_data *bfqd)
+{
+	bfqd->max_rq_in_driver = max(bfqd->max_rq_in_driver,
+				     bfqd->rq_in_driver);
+
+	if (bfqd->hw_tag == 1)
+		return;
+
+	/*
+	 * This sample is valid if the number of outstanding requests
+	 * is large enough to allow a queueing behavior.  Note that the
+	 * sum is not exact, as it's not taking into account deactivated
+	 * requests.
+	 */
+	if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD)
+		return;
+
+	if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES)
+		return;
+
+	bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD;
+	bfqd->max_rq_in_driver = 0;
+	bfqd->hw_tag_samples = 0;
+}
+
+static void bfq_completed_request(struct request_queue *q, struct request *rq)
+{
+	struct bfq_queue *bfqq = RQ_BFQQ(rq);
+	struct bfq_data *bfqd = bfqq->bfqd;
+	bool sync = bfq_bfqq_sync(bfqq);
+
+	bfq_log_bfqq(bfqd, bfqq, "completed one req with %u sects left (%d)",
+		     blk_rq_sectors(rq), sync);
+
+	bfq_update_hw_tag(bfqd);
+
+	BUG_ON(!bfqd->rq_in_driver);
+	BUG_ON(!bfqq->dispatched);
+	bfqd->rq_in_driver--;
+	bfqq->dispatched--;
+
+	if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) {
+		bfq_weights_tree_remove(bfqd, &bfqq->entity,
+					&bfqd->queue_weights_tree);
+		if (!blk_queue_nonrot(bfqd->queue)) {
+			BUG_ON(!bfqd->busy_in_flight_queues);
+			bfqd->busy_in_flight_queues--;
+			if (bfq_bfqq_constantly_seeky(bfqq)) {
+				BUG_ON(!bfqd->
+					const_seeky_busy_in_flight_queues);
+				bfqd->const_seeky_busy_in_flight_queues--;
+			}
+		}
+	}
+
+	if (sync) {
+		bfqd->sync_flight--;
+		RQ_BIC(rq)->ttime.last_end_request = jiffies;
+	}
+
+	/*
+	 * If we are waiting to discover whether the request pattern of the
+	 * task associated with the queue is actually isochronous, and
+	 * both requisites for this condition to hold are satisfied, then
+	 * compute soft_rt_next_start (see the comments to the function
+	 * bfq_bfqq_softrt_next_start()).
+	 */
+	if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 &&
+	    RB_EMPTY_ROOT(&bfqq->sort_list))
+		bfqq->soft_rt_next_start =
+			bfq_bfqq_softrt_next_start(bfqd, bfqq);
+
+	/*
+	 * If this is the in-service queue, check if it needs to be expired,
+	 * or if we want to idle in case it has no pending requests.
+	 */
+	if (bfqd->in_service_queue == bfqq) {
+		if (bfq_bfqq_budget_new(bfqq))
+			bfq_set_budget_timeout(bfqd);
+
+		if (bfq_bfqq_must_idle(bfqq)) {
+			bfq_arm_slice_timer(bfqd);
+			goto out;
+		} else if (bfq_may_expire_for_budg_timeout(bfqq))
+			bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_TIMEOUT);
+		else if (RB_EMPTY_ROOT(&bfqq->sort_list) &&
+			 (bfqq->dispatched == 0 ||
+			  !bfq_bfqq_must_not_expire(bfqq)))
+			bfq_bfqq_expire(bfqd, bfqq, 0,
+					BFQ_BFQQ_NO_MORE_REQUESTS);
+	}
+
+	if (!bfqd->rq_in_driver)
+		bfq_schedule_dispatch(bfqd);
+
+out:
+	return;
+}
+
+static inline int __bfq_may_queue(struct bfq_queue *bfqq)
+{
+	if (bfq_bfqq_wait_request(bfqq) && bfq_bfqq_must_alloc(bfqq)) {
+		bfq_clear_bfqq_must_alloc(bfqq);
+		return ELV_MQUEUE_MUST;
+	}
+
+	return ELV_MQUEUE_MAY;
+}
+
+static int bfq_may_queue(struct request_queue *q, int rw)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+	struct task_struct *tsk = current;
+	struct bfq_io_cq *bic;
+	struct bfq_queue *bfqq;
+
+	/*
+	 * Don't force setup of a queue from here, as a call to may_queue
+	 * does not necessarily imply that a request actually will be
+	 * queued. So just lookup a possibly existing queue, or return
+	 * 'may queue' if that fails.
+	 */
+	bic = bfq_bic_lookup(bfqd, tsk->io_context);
+	if (bic == NULL)
+		return ELV_MQUEUE_MAY;
+
+	bfqq = bic_to_bfqq(bic, rw_is_sync(rw));
+	if (bfqq != NULL) {
+		bfq_init_prio_data(bfqq, bic->icq.ioc);
+
+		return __bfq_may_queue(bfqq);
+	}
+
+	return ELV_MQUEUE_MAY;
+}
+
+/*
+ * Queue lock held here.
+ */
+static void bfq_put_request(struct request *rq)
+{
+	struct bfq_queue *bfqq = RQ_BFQQ(rq);
+
+	if (bfqq != NULL) {
+		const int rw = rq_data_dir(rq);
+
+		BUG_ON(!bfqq->allocated[rw]);
+		bfqq->allocated[rw]--;
+
+		rq->elv.priv[0] = NULL;
+		rq->elv.priv[1] = NULL;
+
+		bfq_log_bfqq(bfqq->bfqd, bfqq, "put_request %p, %d",
+			     bfqq, atomic_read(&bfqq->ref));
+		bfq_put_queue(bfqq);
+	}
+}
+
+/*
+ * Returns NULL if a new bfqq should be allocated, or the old bfqq if this
+ * was the last process referring to said bfqq.
+ */
+static struct bfq_queue *
+bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq)
+{
+	bfq_log_bfqq(bfqq->bfqd, bfqq, "splitting queue");
+
+	put_io_context(bic->icq.ioc);
+
+	if (bfqq_process_refs(bfqq) == 1) {
+		bfqq->pid = current->pid;
+		bfq_clear_bfqq_coop(bfqq);
+		bfq_clear_bfqq_split_coop(bfqq);
+		return bfqq;
+	}
+
+	bic_set_bfqq(bic, NULL, 1);
+
+	bfq_put_cooperator(bfqq);
+
+	bfq_put_queue(bfqq);
+	return NULL;
+}
+
+/*
+ * Allocate bfq data structures associated with this request.
+ */
+static int bfq_set_request(struct request_queue *q, struct request *rq,
+			   gfp_t gfp_mask)
+{
+	struct bfq_data *bfqd = q->elevator->elevator_data;
+	struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq);
+	const int rw = rq_data_dir(rq);
+	const int is_sync = rq_is_sync(rq);
+	struct bfq_queue *bfqq;
+	struct bfq_group *bfqg;
+	unsigned long flags;
+	bool split = false;
+
+	/* handle changed prio notifications; cgroup change is handled separately */
+	if (unlikely(icq_get_changed(&bic->icq) & ICQ_IOPRIO_CHANGED))
+		bfq_changed_ioprio(bic->icq.ioc, bic);
+
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+
+	spin_lock_irqsave(q->queue_lock, flags);
+
+	if (bic == NULL)
+		goto queue_fail;
+
+	bfqg = bfq_bic_update_cgroup(bic);
+
+new_queue:
+	bfqq = bic_to_bfqq(bic, is_sync);
+	if (bfqq == NULL || bfqq == &bfqd->oom_bfqq) {
+		bfqq = bfq_get_queue(bfqd, bfqg, is_sync, bic->icq.ioc, gfp_mask);
+		bic_set_bfqq(bic, bfqq, is_sync);
+		if (split && is_sync) {
+			if ((bic->was_in_burst_list && bfqd->large_burst) ||
+			    bic->saved_in_large_burst)
+				bfq_mark_bfqq_in_large_burst(bfqq);
+			else {
+			    bfq_clear_bfqq_in_large_burst(bfqq);
+			    if (bic->was_in_burst_list)
+			       hlist_add_head(&bfqq->burst_list_node,
+				              &bfqd->burst_list);
+			}
+		}
+	} else {
+		/* If the queue was seeky for too long, break it apart. */
+		if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq)) {
+			bfq_log_bfqq(bfqd, bfqq, "breaking apart bfqq");
+			bfqq = bfq_split_bfqq(bic, bfqq);
+			split = true;
+			if (!bfqq)
+				goto new_queue;
+		}
+	}
+
+	bfqq->allocated[rw]++;
+	atomic_inc(&bfqq->ref);
+	bfq_log_bfqq(bfqd, bfqq, "set_request: bfqq %p, %d", bfqq,
+		     atomic_read(&bfqq->ref));
+
+	rq->elv.priv[0] = bic;
+	rq->elv.priv[1] = bfqq;
+
+	/*
+	 * If a bfq_queue has only one process reference, it is owned
+	 * by only one bfq_io_cq: we can set the bic field of the
+	 * bfq_queue to the address of that structure. Also, if the
+	 * queue has just been split, mark a flag so that the
+	 * information is available to the other scheduler hooks.
+	 */
+	if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) {
+		bfqq->bic = bic;
+		if (split) {
+			bfq_mark_bfqq_just_split(bfqq);
+			/*
+			 * If the queue has just been split from a shared
+			 * queue, restore the idle window and the possible
+			 * weight raising period.
+			 */
+			bfq_bfqq_resume_state(bfqq, bic);
+		}
+	}
+
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	return 0;
+
+queue_fail:
+	bfq_schedule_dispatch(bfqd);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	return 1;
+}
+
+static void bfq_kick_queue(struct work_struct *work)
+{
+	struct bfq_data *bfqd =
+		container_of(work, struct bfq_data, unplug_work);
+	struct request_queue *q = bfqd->queue;
+
+	spin_lock_irq(q->queue_lock);
+	__blk_run_queue(q);
+	spin_unlock_irq(q->queue_lock);
+}
+
+/*
+ * Handler of the expiration of the timer running if the in-service queue
+ * is idling inside its time slice.
+ */
+static void bfq_idle_slice_timer(unsigned long data)
+{
+	struct bfq_data *bfqd = (struct bfq_data *)data;
+	struct bfq_queue *bfqq;
+	unsigned long flags;
+	enum bfqq_expiration reason;
+
+	spin_lock_irqsave(bfqd->queue->queue_lock, flags);
+
+	bfqq = bfqd->in_service_queue;
+	/*
+	 * Theoretical race here: the in-service queue can be NULL or
+	 * different from the queue that was idling if the timer handler
+	 * spins on the queue_lock and a new request arrives for the
+	 * current queue and there is a full dispatch cycle that changes
+	 * the in-service queue.  This can hardly happen, but in the worst
+	 * case we just expire a queue too early.
+	 */
+	if (bfqq != NULL) {
+		bfq_log_bfqq(bfqd, bfqq, "slice_timer expired");
+		if (bfq_bfqq_budget_timeout(bfqq))
+			/*
+			 * Also here the queue can be safely expired
+			 * for budget timeout without wasting
+			 * guarantees
+			 */
+			reason = BFQ_BFQQ_BUDGET_TIMEOUT;
+		else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0)
+			/*
+			 * The queue may not be empty upon timer expiration,
+			 * because we may not disable the timer when the
+			 * first request of the in-service queue arrives
+			 * during disk idling.
+			 */
+			reason = BFQ_BFQQ_TOO_IDLE;
+		else
+			goto schedule_dispatch;
+
+		bfq_bfqq_expire(bfqd, bfqq, 1, reason);
+	}
+
+schedule_dispatch:
+	bfq_schedule_dispatch(bfqd);
+
+	spin_unlock_irqrestore(bfqd->queue->queue_lock, flags);
+}
+
+static void bfq_shutdown_timer_wq(struct bfq_data *bfqd)
+{
+	del_timer_sync(&bfqd->idle_slice_timer);
+	cancel_work_sync(&bfqd->unplug_work);
+}
+
+static inline void __bfq_put_async_bfqq(struct bfq_data *bfqd,
+					struct bfq_queue **bfqq_ptr)
+{
+	struct bfq_group *root_group = bfqd->root_group;
+	struct bfq_queue *bfqq = *bfqq_ptr;
+
+	bfq_log(bfqd, "put_async_bfqq: %p", bfqq);
+	if (bfqq != NULL) {
+		bfq_bfqq_move(bfqd, bfqq, &bfqq->entity, root_group);
+		bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d",
+			     bfqq, atomic_read(&bfqq->ref));
+		bfq_put_queue(bfqq);
+		*bfqq_ptr = NULL;
+	}
+}
+
+/*
+ * Release all the bfqg references to its async queues.  If we are
+ * deallocating the group these queues may still contain requests, so
+ * we reparent them to the root cgroup (i.e., the only one that will
+ * exist for sure until all the requests on a device are gone).
+ */
+static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
+{
+	int i, j;
+
+	for (i = 0; i < 2; i++)
+		for (j = 0; j < IOPRIO_BE_NR; j++)
+			__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
+
+	__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
+}
+
+static void bfq_exit_queue(struct elevator_queue *e)
+{
+	struct bfq_data *bfqd = e->elevator_data;
+	struct request_queue *q = bfqd->queue;
+	struct bfq_queue *bfqq, *n;
+
+	bfq_shutdown_timer_wq(bfqd);
+
+	spin_lock_irq(q->queue_lock);
+
+	BUG_ON(bfqd->in_service_queue != NULL);
+	list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list)
+		bfq_deactivate_bfqq(bfqd, bfqq, 0);
+
+	bfq_disconnect_groups(bfqd);
+	spin_unlock_irq(q->queue_lock);
+
+	bfq_shutdown_timer_wq(bfqd);
+
+	synchronize_rcu();
+
+	BUG_ON(timer_pending(&bfqd->idle_slice_timer));
+
+	bfq_free_root_group(bfqd);
+	kfree(bfqd);
+}
+
+static void *bfq_init_queue(struct request_queue *q)
+{
+	struct bfq_group *bfqg;
+	struct bfq_data *bfqd;
+
+	bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node);
+	if (bfqd == NULL)
+		return NULL;
+
+	/*
+	 * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues.
+	 * Grab a permanent reference to it, so that the normal code flow
+	 * will not attempt to free it.
+	 */
+	bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, 1, 0);
+	atomic_inc(&bfqd->oom_bfqq.ref);
+	bfqd->oom_bfqq.entity.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO;
+	bfqd->oom_bfqq.entity.new_ioprio_class = IOPRIO_CLASS_BE;
+	/*
+	 * Trigger weight initialization, according to ioprio, at the
+	 * oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio
+	 * class won't be changed any more.
+	 */
+	bfqd->oom_bfqq.entity.ioprio_changed = 1;
+
+	bfqd->queue = q;
+
+	bfqg = bfq_alloc_root_group(bfqd, q->node);
+	if (bfqg == NULL) {
+		kfree(bfqd);
+		return NULL;
+	}
+
+	bfqd->root_group = bfqg;
+	bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group);
+#ifdef CONFIG_CGROUP_BFQIO
+	bfqd->active_numerous_groups = 0;
+#endif
+
+	init_timer(&bfqd->idle_slice_timer);
+	bfqd->idle_slice_timer.function = bfq_idle_slice_timer;
+	bfqd->idle_slice_timer.data = (unsigned long)bfqd;
+
+	bfqd->rq_pos_tree = RB_ROOT;
+	bfqd->queue_weights_tree = RB_ROOT;
+	bfqd->group_weights_tree = RB_ROOT;
+
+	INIT_WORK(&bfqd->unplug_work, bfq_kick_queue);
+
+	INIT_LIST_HEAD(&bfqd->active_list);
+	INIT_LIST_HEAD(&bfqd->idle_list);
+	INIT_HLIST_HEAD(&bfqd->burst_list);
+
+	bfqd->hw_tag = -1;
+
+	bfqd->bfq_max_budget = bfq_default_max_budget;
+
+	bfqd->bfq_quantum = bfq_quantum;
+	bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0];
+	bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1];
+	bfqd->bfq_back_max = bfq_back_max;
+	bfqd->bfq_back_penalty = bfq_back_penalty;
+	bfqd->bfq_slice_idle = bfq_slice_idle;
+	bfqd->bfq_class_idle_last_service = 0;
+	bfqd->bfq_max_budget_async_rq = bfq_max_budget_async_rq;
+	bfqd->bfq_timeout[BLK_RW_ASYNC] = bfq_timeout_async;
+	bfqd->bfq_timeout[BLK_RW_SYNC] = bfq_timeout_sync;
+
+	bfqd->bfq_coop_thresh = 2;
+	bfqd->bfq_failed_cooperations = 7000;
+	bfqd->bfq_requests_within_timer = 120;
+
+	bfqd->bfq_large_burst_thresh = 11;
+	bfqd->bfq_burst_interval = msecs_to_jiffies(500);
+
+	bfqd->low_latency = true;
+
+	bfqd->bfq_wr_coeff = 20;
+	bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300);
+	bfqd->bfq_wr_max_time = 0;
+	bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000);
+	bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500);
+	bfqd->bfq_wr_max_softrt_rate = 7000; /*
+					      * Approximate rate required
+					      * to playback or record a
+					      * high-definition compressed
+					      * video.
+					      */
+	bfqd->wr_busy_queues = 0;
+	bfqd->busy_in_flight_queues = 0;
+	bfqd->const_seeky_busy_in_flight_queues = 0;
+
+	/*
+	 * Begin by assuming, optimistically, that the device peak rate is
+	 * equal to the highest reference rate.
+	 */
+	bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] *
+			T_fast[blk_queue_nonrot(bfqd->queue)];
+	bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)];
+	bfqd->device_speed = BFQ_BFQD_FAST;
+
+	return bfqd;
+}
+
+static void bfq_slab_kill(void)
+{
+	if (bfq_pool != NULL)
+		kmem_cache_destroy(bfq_pool);
+}
+
+static int __init bfq_slab_setup(void)
+{
+	bfq_pool = KMEM_CACHE(bfq_queue, 0);
+	if (bfq_pool == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+static ssize_t bfq_var_show(unsigned int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t bfq_var_store(unsigned long *var, const char *page,
+			     size_t count)
+{
+	unsigned long new_val;
+	int ret = kstrtoul(page, 10, &new_val);
+
+	if (ret == 0)
+		*var = new_val;
+
+	return count;
+}
+
+static ssize_t bfq_wr_max_time_show(struct elevator_queue *e, char *page)
+{
+	struct bfq_data *bfqd = e->elevator_data;
+	return sprintf(page, "%d\n", bfqd->bfq_wr_max_time > 0 ?
+		       jiffies_to_msecs(bfqd->bfq_wr_max_time) :
+		       jiffies_to_msecs(bfq_wr_duration(bfqd)));
+}
+
+static ssize_t bfq_weights_show(struct elevator_queue *e, char *page)
+{
+	struct bfq_queue *bfqq;
+	struct bfq_data *bfqd = e->elevator_data;
+	ssize_t num_char = 0;
+
+	num_char += sprintf(page + num_char, "Tot reqs queued %d\n\n",
+			    bfqd->queued);
+
+	spin_lock_irq(bfqd->queue->queue_lock);
+
+	num_char += sprintf(page + num_char, "Active:\n");
+	list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) {
+	  num_char += sprintf(page + num_char,
+			      "pid%d: weight %hu, nr_queued %d %d, dur %d/%u\n",
+			      bfqq->pid,
+			      bfqq->entity.weight,
+			      bfqq->queued[0],
+			      bfqq->queued[1],
+			jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
+			jiffies_to_msecs(bfqq->wr_cur_max_time));
+	}
+
+	num_char += sprintf(page + num_char, "Idle:\n");
+	list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) {
+			num_char += sprintf(page + num_char,
+				"pid%d: weight %hu, dur %d/%u\n",
+				bfqq->pid,
+				bfqq->entity.weight,
+				jiffies_to_msecs(jiffies -
+					bfqq->last_wr_start_finish),
+				jiffies_to_msecs(bfqq->wr_cur_max_time));
+	}
+
+	spin_unlock_irq(bfqd->queue->queue_lock);
+
+	return num_char;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
+static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
+{									\
+	struct bfq_data *bfqd = e->elevator_data;			\
+	unsigned int __data = __VAR;					\
+	if (__CONV)							\
+		__data = jiffies_to_msecs(__data);			\
+	return bfq_var_show(__data, (page));				\
+}
+SHOW_FUNCTION(bfq_quantum_show, bfqd->bfq_quantum, 0);
+SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 1);
+SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 1);
+SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0);
+SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0);
+SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 1);
+SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0);
+SHOW_FUNCTION(bfq_max_budget_async_rq_show,
+	      bfqd->bfq_max_budget_async_rq, 0);
+SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout[BLK_RW_SYNC], 1);
+SHOW_FUNCTION(bfq_timeout_async_show, bfqd->bfq_timeout[BLK_RW_ASYNC], 1);
+SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0);
+SHOW_FUNCTION(bfq_wr_coeff_show, bfqd->bfq_wr_coeff, 0);
+SHOW_FUNCTION(bfq_wr_rt_max_time_show, bfqd->bfq_wr_rt_max_time, 1);
+SHOW_FUNCTION(bfq_wr_min_idle_time_show, bfqd->bfq_wr_min_idle_time, 1);
+SHOW_FUNCTION(bfq_wr_min_inter_arr_async_show, bfqd->bfq_wr_min_inter_arr_async,
+	1);
+SHOW_FUNCTION(bfq_wr_max_softrt_rate_show, bfqd->bfq_wr_max_softrt_rate, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
+static ssize_t								\
+__FUNC(struct elevator_queue *e, const char *page, size_t count)	\
+{									\
+	struct bfq_data *bfqd = e->elevator_data;			\
+	unsigned long uninitialized_var(__data);			\
+	int ret = bfq_var_store(&__data, (page), count);		\
+	if (__data < (MIN))						\
+		__data = (MIN);						\
+	else if (__data > (MAX))					\
+		__data = (MAX);						\
+	if (__CONV)							\
+		*(__PTR) = msecs_to_jiffies(__data);			\
+	else								\
+		*(__PTR) = __data;					\
+	return ret;							\
+}
+STORE_FUNCTION(bfq_quantum_store, &bfqd->bfq_quantum, 1, INT_MAX, 0);
+STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1,
+		INT_MAX, 1);
+STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1,
+		INT_MAX, 1);
+STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0);
+STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1,
+		INT_MAX, 0);
+STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 1);
+STORE_FUNCTION(bfq_max_budget_async_rq_store, &bfqd->bfq_max_budget_async_rq,
+		1, INT_MAX, 0);
+STORE_FUNCTION(bfq_timeout_async_store, &bfqd->bfq_timeout[BLK_RW_ASYNC], 0,
+		INT_MAX, 1);
+STORE_FUNCTION(bfq_wr_coeff_store, &bfqd->bfq_wr_coeff, 1, INT_MAX, 0);
+STORE_FUNCTION(bfq_wr_max_time_store, &bfqd->bfq_wr_max_time, 0, INT_MAX, 1);
+STORE_FUNCTION(bfq_wr_rt_max_time_store, &bfqd->bfq_wr_rt_max_time, 0, INT_MAX,
+		1);
+STORE_FUNCTION(bfq_wr_min_idle_time_store, &bfqd->bfq_wr_min_idle_time, 0,
+		INT_MAX, 1);
+STORE_FUNCTION(bfq_wr_min_inter_arr_async_store,
+		&bfqd->bfq_wr_min_inter_arr_async, 0, INT_MAX, 1);
+STORE_FUNCTION(bfq_wr_max_softrt_rate_store, &bfqd->bfq_wr_max_softrt_rate, 0,
+		INT_MAX, 0);
+#undef STORE_FUNCTION
+
+/* do nothing for the moment */
+static ssize_t bfq_weights_store(struct elevator_queue *e,
+				    const char *page, size_t count)
+{
+	return count;
+}
+
+static inline unsigned long bfq_estimated_max_budget(struct bfq_data *bfqd)
+{
+	u64 timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]);
+
+	if (bfqd->peak_rate_samples >= BFQ_PEAK_RATE_SAMPLES)
+		return bfq_calc_max_budget(bfqd->peak_rate, timeout);
+	else
+		return bfq_default_max_budget;
+}
+
+static ssize_t bfq_max_budget_store(struct elevator_queue *e,
+				    const char *page, size_t count)
+{
+	struct bfq_data *bfqd = e->elevator_data;
+	unsigned long uninitialized_var(__data);
+	int ret = bfq_var_store(&__data, (page), count);
+
+	if (__data == 0)
+		bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd);
+	else {
+		if (__data > INT_MAX)
+			__data = INT_MAX;
+		bfqd->bfq_max_budget = __data;
+	}
+
+	bfqd->bfq_user_max_budget = __data;
+
+	return ret;
+}
+
+static ssize_t bfq_timeout_sync_store(struct elevator_queue *e,
+				      const char *page, size_t count)
+{
+	struct bfq_data *bfqd = e->elevator_data;
+	unsigned long uninitialized_var(__data);
+	int ret = bfq_var_store(&__data, (page), count);
+
+	if (__data < 1)
+		__data = 1;
+	else if (__data > INT_MAX)
+		__data = INT_MAX;
+
+	bfqd->bfq_timeout[BLK_RW_SYNC] = msecs_to_jiffies(__data);
+	if (bfqd->bfq_user_max_budget == 0)
+		bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd);
+
+	return ret;
+}
+
+static ssize_t bfq_low_latency_store(struct elevator_queue *e,
+				     const char *page, size_t count)
+{
+	struct bfq_data *bfqd = e->elevator_data;
+	unsigned long uninitialized_var(__data);
+	int ret = bfq_var_store(&__data, (page), count);
+
+	if (__data > 1)
+		__data = 1;
+	if (__data == 0 && bfqd->low_latency != 0)
+		bfq_end_wr(bfqd);
+	bfqd->low_latency = __data;
+
+	return ret;
+}
+
+#define BFQ_ATTR(name) \
+	__ATTR(name, S_IRUGO|S_IWUSR, bfq_##name##_show, bfq_##name##_store)
+
+static struct elv_fs_entry bfq_attrs[] = {
+	BFQ_ATTR(quantum),
+	BFQ_ATTR(fifo_expire_sync),
+	BFQ_ATTR(fifo_expire_async),
+	BFQ_ATTR(back_seek_max),
+	BFQ_ATTR(back_seek_penalty),
+	BFQ_ATTR(slice_idle),
+	BFQ_ATTR(max_budget),
+	BFQ_ATTR(max_budget_async_rq),
+	BFQ_ATTR(timeout_sync),
+	BFQ_ATTR(timeout_async),
+	BFQ_ATTR(low_latency),
+	BFQ_ATTR(wr_coeff),
+	BFQ_ATTR(wr_max_time),
+	BFQ_ATTR(wr_rt_max_time),
+	BFQ_ATTR(wr_min_idle_time),
+	BFQ_ATTR(wr_min_inter_arr_async),
+	BFQ_ATTR(wr_max_softrt_rate),
+	BFQ_ATTR(weights),
+	__ATTR_NULL
+};
+
+static struct elevator_type iosched_bfq = {
+	.ops = {
+		.elevator_merge_fn =		bfq_merge,
+		.elevator_merged_fn =		bfq_merged_request,
+		.elevator_merge_req_fn =	bfq_merged_requests,
+		.elevator_allow_merge_fn =	bfq_allow_merge,
+		.elevator_dispatch_fn =		bfq_dispatch_requests,
+		.elevator_add_req_fn =		bfq_insert_request,
+		.elevator_activate_req_fn =	bfq_activate_request,
+		.elevator_deactivate_req_fn =	bfq_deactivate_request,
+		.elevator_completed_req_fn =	bfq_completed_request,
+		.elevator_former_req_fn =	elv_rb_former_request,
+		.elevator_latter_req_fn =	elv_rb_latter_request,
+		.elevator_init_icq_fn =		bfq_init_icq,
+		.elevator_exit_icq_fn =		bfq_exit_icq,
+		.elevator_set_req_fn =		bfq_set_request,
+		.elevator_put_req_fn =		bfq_put_request,
+		.elevator_may_queue_fn =	bfq_may_queue,
+		.elevator_init_fn =		bfq_init_queue,
+		.elevator_exit_fn =		bfq_exit_queue,
+	},
+	.icq_size =		sizeof(struct bfq_io_cq),
+	.icq_align =		__alignof__(struct bfq_io_cq),
+	.elevator_attrs =	bfq_attrs,
+	.elevator_name =	"bfq",
+	.elevator_owner =	THIS_MODULE,
+};
+
+static int __init bfq_init(void)
+{
+	/*
+	 * Can be 0 on HZ < 1000 setups.
+	 */
+	if (bfq_slice_idle == 0)
+		bfq_slice_idle = 1;
+
+	if (bfq_timeout_async == 0)
+		bfq_timeout_async = 1;
+
+	if (bfq_slab_setup())
+		return -ENOMEM;
+
+	/*
+	 * Times to load large popular applications for the typical systems
+	 * installed on the reference devices (see the comments before the
+	 * definitions of the two arrays).
+	 */
+	T_slow[0] = msecs_to_jiffies(2600);
+	T_slow[1] = msecs_to_jiffies(1000);
+	T_fast[0] = msecs_to_jiffies(5500);
+	T_fast[1] = msecs_to_jiffies(2000);
+
+	/*
+	 * Thresholds that determine the switch between speed classes (see
+	 * the comments before the definition of the array).
+	 */
+	device_speed_thresh[0] = (R_fast[0] + R_slow[0]) / 2;
+	device_speed_thresh[1] = (R_fast[1] + R_slow[1]) / 2;
+
+	elv_register(&iosched_bfq);
+	pr_info("BFQ I/O-scheduler version: v7r7");
+
+	return 0;
+}
+
+static void __exit bfq_exit(void)
+{
+	elv_unregister(&iosched_bfq);
+	bfq_slab_kill();
+}
+
+module_init(bfq_init);
+module_exit(bfq_exit);
+
+MODULE_AUTHOR("Fabio Checconi, Paolo Valente");
+MODULE_LICENSE("GPL");
diff --git a/block/bfq-sched.c b/block/bfq-sched.c
new file mode 100644
index 0000000..6764a7e
--- /dev/null
+++ b/block/bfq-sched.c
@@ -0,0 +1,1186 @@
+/*
+ * BFQ: Hierarchical B-WF2Q+ scheduler.
+ *
+ * Based on ideas and code from CFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
+ *		      Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
+ */
+
+#ifdef CONFIG_CGROUP_BFQIO
+#define for_each_entity(entity)	\
+	for (; entity != NULL; entity = entity->parent)
+
+#define for_each_entity_safe(entity, parent) \
+	for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
+
+static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,
+						 int extract,
+						 struct bfq_data *bfqd);
+
+static inline void bfq_update_budget(struct bfq_entity *next_in_service)
+{
+	struct bfq_entity *bfqg_entity;
+	struct bfq_group *bfqg;
+	struct bfq_sched_data *group_sd;
+
+	BUG_ON(next_in_service == NULL);
+
+	group_sd = next_in_service->sched_data;
+
+	bfqg = container_of(group_sd, struct bfq_group, sched_data);
+	/*
+	 * bfq_group's my_entity field is not NULL only if the group
+	 * is not the root group. We must not touch the root entity
+	 * as it must never become an in-service entity.
+	 */
+	bfqg_entity = bfqg->my_entity;
+	if (bfqg_entity != NULL)
+		bfqg_entity->budget = next_in_service->budget;
+}
+
+static int bfq_update_next_in_service(struct bfq_sched_data *sd)
+{
+	struct bfq_entity *next_in_service;
+
+	if (sd->in_service_entity != NULL)
+		/* will update/requeue at the end of service */
+		return 0;
+
+	/*
+	 * NOTE: this can be improved in many ways, such as returning
+	 * 1 (and thus propagating upwards the update) only when the
+	 * budget changes, or caching the bfqq that will be scheduled
+	 * next from this subtree.  By now we worry more about
+	 * correctness than about performance...
+	 */
+	next_in_service = bfq_lookup_next_entity(sd, 0, NULL);
+	sd->next_in_service = next_in_service;
+
+	if (next_in_service != NULL)
+		bfq_update_budget(next_in_service);
+
+	return 1;
+}
+
+static inline void bfq_check_next_in_service(struct bfq_sched_data *sd,
+					     struct bfq_entity *entity)
+{
+	BUG_ON(sd->next_in_service != entity);
+}
+#else
+#define for_each_entity(entity)	\
+	for (; entity != NULL; entity = NULL)
+
+#define for_each_entity_safe(entity, parent) \
+	for (parent = NULL; entity != NULL; entity = parent)
+
+static inline int bfq_update_next_in_service(struct bfq_sched_data *sd)
+{
+	return 0;
+}
+
+static inline void bfq_check_next_in_service(struct bfq_sched_data *sd,
+					     struct bfq_entity *entity)
+{
+}
+
+static inline void bfq_update_budget(struct bfq_entity *next_in_service)
+{
+}
+#endif
+
+/*
+ * Shift for timestamp calculations.  This actually limits the maximum
+ * service allowed in one timestamp delta (small shift values increase it),
+ * the maximum total weight that can be used for the queues in the system
+ * (big shift values increase it), and the period of virtual time
+ * wraparounds.
+ */
+#define WFQ_SERVICE_SHIFT	22
+
+/**
+ * bfq_gt - compare two timestamps.
+ * @a: first ts.
+ * @b: second ts.
+ *
+ * Return @a > @b, dealing with wrapping correctly.
+ */
+static inline int bfq_gt(u64 a, u64 b)
+{
+	return (s64)(a - b) > 0;
+}
+
+static inline struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = NULL;
+
+	BUG_ON(entity == NULL);
+
+	if (entity->my_sched_data == NULL)
+		bfqq = container_of(entity, struct bfq_queue, entity);
+
+	return bfqq;
+}
+
+
+/**
+ * bfq_delta - map service into the virtual time domain.
+ * @service: amount of service.
+ * @weight: scale factor (weight of an entity or weight sum).
+ */
+static inline u64 bfq_delta(unsigned long service,
+					unsigned long weight)
+{
+	u64 d = (u64)service << WFQ_SERVICE_SHIFT;
+
+	do_div(d, weight);
+	return d;
+}
+
+/**
+ * bfq_calc_finish - assign the finish time to an entity.
+ * @entity: the entity to act upon.
+ * @service: the service to be charged to the entity.
+ */
+static inline void bfq_calc_finish(struct bfq_entity *entity,
+				   unsigned long service)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+
+	BUG_ON(entity->weight == 0);
+
+	entity->finish = entity->start +
+		bfq_delta(service, entity->weight);
+
+	if (bfqq != NULL) {
+		bfq_log_bfqq(bfqq->bfqd, bfqq,
+			"calc_finish: serv %lu, w %d",
+			service, entity->weight);
+		bfq_log_bfqq(bfqq->bfqd, bfqq,
+			"calc_finish: start %llu, finish %llu, delta %llu",
+			entity->start, entity->finish,
+			bfq_delta(service, entity->weight));
+	}
+}
+
+/**
+ * bfq_entity_of - get an entity from a node.
+ * @node: the node field of the entity.
+ *
+ * Convert a node pointer to the relative entity.  This is used only
+ * to simplify the logic of some functions and not as the generic
+ * conversion mechanism because, e.g., in the tree walking functions,
+ * the check for a %NULL value would be redundant.
+ */
+static inline struct bfq_entity *bfq_entity_of(struct rb_node *node)
+{
+	struct bfq_entity *entity = NULL;
+
+	if (node != NULL)
+		entity = rb_entry(node, struct bfq_entity, rb_node);
+
+	return entity;
+}
+
+/**
+ * bfq_extract - remove an entity from a tree.
+ * @root: the tree root.
+ * @entity: the entity to remove.
+ */
+static inline void bfq_extract(struct rb_root *root,
+			       struct bfq_entity *entity)
+{
+	BUG_ON(entity->tree != root);
+
+	entity->tree = NULL;
+	rb_erase(&entity->rb_node, root);
+}
+
+/**
+ * bfq_idle_extract - extract an entity from the idle tree.
+ * @st: the service tree of the owning @entity.
+ * @entity: the entity being removed.
+ */
+static void bfq_idle_extract(struct bfq_service_tree *st,
+			     struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+	struct rb_node *next;
+
+	BUG_ON(entity->tree != &st->idle);
+
+	if (entity == st->first_idle) {
+		next = rb_next(&entity->rb_node);
+		st->first_idle = bfq_entity_of(next);
+	}
+
+	if (entity == st->last_idle) {
+		next = rb_prev(&entity->rb_node);
+		st->last_idle = bfq_entity_of(next);
+	}
+
+	bfq_extract(&st->idle, entity);
+
+	if (bfqq != NULL)
+		list_del(&bfqq->bfqq_list);
+}
+
+/**
+ * bfq_insert - generic tree insertion.
+ * @root: tree root.
+ * @entity: entity to insert.
+ *
+ * This is used for the idle and the active tree, since they are both
+ * ordered by finish time.
+ */
+static void bfq_insert(struct rb_root *root, struct bfq_entity *entity)
+{
+	struct bfq_entity *entry;
+	struct rb_node **node = &root->rb_node;
+	struct rb_node *parent = NULL;
+
+	BUG_ON(entity->tree != NULL);
+
+	while (*node != NULL) {
+		parent = *node;
+		entry = rb_entry(parent, struct bfq_entity, rb_node);
+
+		if (bfq_gt(entry->finish, entity->finish))
+			node = &parent->rb_left;
+		else
+			node = &parent->rb_right;
+	}
+
+	rb_link_node(&entity->rb_node, parent, node);
+	rb_insert_color(&entity->rb_node, root);
+
+	entity->tree = root;
+}
+
+/**
+ * bfq_update_min - update the min_start field of a entity.
+ * @entity: the entity to update.
+ * @node: one of its children.
+ *
+ * This function is called when @entity may store an invalid value for
+ * min_start due to updates to the active tree.  The function  assumes
+ * that the subtree rooted at @node (which may be its left or its right
+ * child) has a valid min_start value.
+ */
+static inline void bfq_update_min(struct bfq_entity *entity,
+				  struct rb_node *node)
+{
+	struct bfq_entity *child;
+
+	if (node != NULL) {
+		child = rb_entry(node, struct bfq_entity, rb_node);
+		if (bfq_gt(entity->min_start, child->min_start))
+			entity->min_start = child->min_start;
+	}
+}
+
+/**
+ * bfq_update_active_node - recalculate min_start.
+ * @node: the node to update.
+ *
+ * @node may have changed position or one of its children may have moved,
+ * this function updates its min_start value.  The left and right subtrees
+ * are assumed to hold a correct min_start value.
+ */
+static inline void bfq_update_active_node(struct rb_node *node)
+{
+	struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node);
+
+	entity->min_start = entity->start;
+	bfq_update_min(entity, node->rb_right);
+	bfq_update_min(entity, node->rb_left);
+}
+
+/**
+ * bfq_update_active_tree - update min_start for the whole active tree.
+ * @node: the starting node.
+ *
+ * @node must be the deepest modified node after an update.  This function
+ * updates its min_start using the values held by its children, assuming
+ * that they did not change, and then updates all the nodes that may have
+ * changed in the path to the root.  The only nodes that may have changed
+ * are the ones in the path or their siblings.
+ */
+static void bfq_update_active_tree(struct rb_node *node)
+{
+	struct rb_node *parent;
+
+up:
+	bfq_update_active_node(node);
+
+	parent = rb_parent(node);
+	if (parent == NULL)
+		return;
+
+	if (node == parent->rb_left && parent->rb_right != NULL)
+		bfq_update_active_node(parent->rb_right);
+	else if (parent->rb_left != NULL)
+		bfq_update_active_node(parent->rb_left);
+
+	node = parent;
+	goto up;
+}
+
+static void bfq_weights_tree_add(struct bfq_data *bfqd,
+				 struct bfq_entity *entity,
+				 struct rb_root *root);
+
+static void bfq_weights_tree_remove(struct bfq_data *bfqd,
+				    struct bfq_entity *entity,
+				    struct rb_root *root);
+
+
+/**
+ * bfq_active_insert - insert an entity in the active tree of its
+ *                     group/device.
+ * @st: the service tree of the entity.
+ * @entity: the entity being inserted.
+ *
+ * The active tree is ordered by finish time, but an extra key is kept
+ * per each node, containing the minimum value for the start times of
+ * its children (and the node itself), so it's possible to search for
+ * the eligible node with the lowest finish time in logarithmic time.
+ */
+static void bfq_active_insert(struct bfq_service_tree *st,
+			      struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+	struct rb_node *node = &entity->rb_node;
+#ifdef CONFIG_CGROUP_BFQIO
+	struct bfq_sched_data *sd = NULL;
+	struct bfq_group *bfqg = NULL;
+	struct bfq_data *bfqd = NULL;
+#endif
+
+	bfq_insert(&st->active, entity);
+
+	if (node->rb_left != NULL)
+		node = node->rb_left;
+	else if (node->rb_right != NULL)
+		node = node->rb_right;
+
+	bfq_update_active_tree(node);
+
+#ifdef CONFIG_CGROUP_BFQIO
+	sd = entity->sched_data;
+	bfqg = container_of(sd, struct bfq_group, sched_data);
+	BUG_ON(!bfqg);
+	bfqd = (struct bfq_data *)bfqg->bfqd;
+#endif
+	if (bfqq != NULL)
+		list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list);
+#ifdef CONFIG_CGROUP_BFQIO
+	else { /* bfq_group */
+		BUG_ON(!bfqd);
+		bfq_weights_tree_add(bfqd, entity, &bfqd->group_weights_tree);
+	}
+	if (bfqg != bfqd->root_group) {
+		BUG_ON(!bfqg);
+		BUG_ON(!bfqd);
+		bfqg->active_entities++;
+		if (bfqg->active_entities == 2)
+			bfqd->active_numerous_groups++;
+	}
+#endif
+}
+
+/**
+ * bfq_ioprio_to_weight - calc a weight from an ioprio.
+ * @ioprio: the ioprio value to convert.
+ */
+static inline unsigned short bfq_ioprio_to_weight(int ioprio)
+{
+	BUG_ON(ioprio < 0 || ioprio >= IOPRIO_BE_NR);
+	return IOPRIO_BE_NR - ioprio;
+}
+
+/**
+ * bfq_weight_to_ioprio - calc an ioprio from a weight.
+ * @weight: the weight value to convert.
+ *
+ * To preserve as mush as possible the old only-ioprio user interface,
+ * 0 is used as an escape ioprio value for weights (numerically) equal or
+ * larger than IOPRIO_BE_NR
+ */
+static inline unsigned short bfq_weight_to_ioprio(int weight)
+{
+	BUG_ON(weight < BFQ_MIN_WEIGHT || weight > BFQ_MAX_WEIGHT);
+	return IOPRIO_BE_NR - weight < 0 ? 0 : IOPRIO_BE_NR - weight;
+}
+
+static inline void bfq_get_entity(struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+
+	if (bfqq != NULL) {
+		atomic_inc(&bfqq->ref);
+		bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",
+			     bfqq, atomic_read(&bfqq->ref));
+	}
+}
+
+/**
+ * bfq_find_deepest - find the deepest node that an extraction can modify.
+ * @node: the node being removed.
+ *
+ * Do the first step of an extraction in an rb tree, looking for the
+ * node that will replace @node, and returning the deepest node that
+ * the following modifications to the tree can touch.  If @node is the
+ * last node in the tree return %NULL.
+ */
+static struct rb_node *bfq_find_deepest(struct rb_node *node)
+{
+	struct rb_node *deepest;
+
+	if (node->rb_right == NULL && node->rb_left == NULL)
+		deepest = rb_parent(node);
+	else if (node->rb_right == NULL)
+		deepest = node->rb_left;
+	else if (node->rb_left == NULL)
+		deepest = node->rb_right;
+	else {
+		deepest = rb_next(node);
+		if (deepest->rb_right != NULL)
+			deepest = deepest->rb_right;
+		else if (rb_parent(deepest) != node)
+			deepest = rb_parent(deepest);
+	}
+
+	return deepest;
+}
+
+/**
+ * bfq_active_extract - remove an entity from the active tree.
+ * @st: the service_tree containing the tree.
+ * @entity: the entity being removed.
+ */
+static void bfq_active_extract(struct bfq_service_tree *st,
+			       struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+	struct rb_node *node;
+#ifdef CONFIG_CGROUP_BFQIO
+	struct bfq_sched_data *sd = NULL;
+	struct bfq_group *bfqg = NULL;
+	struct bfq_data *bfqd = NULL;
+#endif
+
+	node = bfq_find_deepest(&entity->rb_node);
+	bfq_extract(&st->active, entity);
+
+	if (node != NULL)
+		bfq_update_active_tree(node);
+
+#ifdef CONFIG_CGROUP_BFQIO
+	sd = entity->sched_data;
+	bfqg = container_of(sd, struct bfq_group, sched_data);
+	BUG_ON(!bfqg);
+	bfqd = (struct bfq_data *)bfqg->bfqd;
+#endif
+	if (bfqq != NULL)
+		list_del(&bfqq->bfqq_list);
+#ifdef CONFIG_CGROUP_BFQIO
+	else { /* bfq_group */
+		BUG_ON(!bfqd);
+		bfq_weights_tree_remove(bfqd, entity,
+					&bfqd->group_weights_tree);
+	}
+	if (bfqg != bfqd->root_group) {
+		BUG_ON(!bfqg);
+		BUG_ON(!bfqd);
+		BUG_ON(!bfqg->active_entities);
+		bfqg->active_entities--;
+		if (bfqg->active_entities == 1) {
+			BUG_ON(!bfqd->active_numerous_groups);
+			bfqd->active_numerous_groups--;
+		}
+	}
+#endif
+}
+
+/**
+ * bfq_idle_insert - insert an entity into the idle tree.
+ * @st: the service tree containing the tree.
+ * @entity: the entity to insert.
+ */
+static void bfq_idle_insert(struct bfq_service_tree *st,
+			    struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+	struct bfq_entity *first_idle = st->first_idle;
+	struct bfq_entity *last_idle = st->last_idle;
+
+	if (first_idle == NULL || bfq_gt(first_idle->finish, entity->finish))
+		st->first_idle = entity;
+	if (last_idle == NULL || bfq_gt(entity->finish, last_idle->finish))
+		st->last_idle = entity;
+
+	bfq_insert(&st->idle, entity);
+
+	if (bfqq != NULL)
+		list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list);
+}
+
+/**
+ * bfq_forget_entity - remove an entity from the wfq trees.
+ * @st: the service tree.
+ * @entity: the entity being removed.
+ *
+ * Update the device status and forget everything about @entity, putting
+ * the device reference to it, if it is a queue.  Entities belonging to
+ * groups are not refcounted.
+ */
+static void bfq_forget_entity(struct bfq_service_tree *st,
+			      struct bfq_entity *entity)
+{
+	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+	struct bfq_sched_data *sd;
+
+	BUG_ON(!entity->on_st);
+
+	entity->on_st = 0;
+	st->wsum -= entity->weight;
+	if (bfqq != NULL) {
+		sd = entity->sched_data;
+		bfq_log_bfqq(bfqq->bfqd, bfqq, "forget_entity: %p %d",
+			     bfqq, atomic_read(&bfqq->ref));
+		bfq_put_queue(bfqq);
+	}
+}
+
+/**
+ * bfq_put_idle_entity - release the idle tree ref of an entity.
+ * @st: service tree for the entity.
+ * @entity: the entity being released.
+ */
+static void bfq_put_idle_entity(struct bfq_service_tree *st,
+				struct bfq_entity *entity)
+{
+	bfq_idle_extract(st, entity);
+	bfq_forget_entity(st, entity);
+}
+
+/**
+ * bfq_forget_idle - update the idle tree if necessary.
+ * @st: the service tree to act upon.
+ *
+ * To preserve the global O(log N) complexity we only remove one entry here;
+ * as the idle tree will not grow indefinitely this can be done safely.
+ */
+static void bfq_forget_idle(struct bfq_service_tree *st)
+{
+	struct bfq_entity *first_idle = st->first_idle;
+	struct bfq_entity *last_idle = st->last_idle;
+
+	if (RB_EMPTY_ROOT(&st->active) && last_idle != NULL &&
+	    !bfq_gt(last_idle->finish, st->vtime)) {
+		/*
+		 * Forget the whole idle tree, increasing the vtime past
+		 * the last finish time of idle entities.
+		 */
+		st->vtime = last_idle->finish;
+	}
+
+	if (first_idle != NULL && !bfq_gt(first_idle->finish, st->vtime))
+		bfq_put_idle_entity(st, first_idle);
+}
+
+static struct bfq_service_tree *
+__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
+			 struct bfq_entity *entity)
+{
+	struct bfq_service_tree *new_st = old_st;
+
+	if (entity->ioprio_changed) {
+		struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
+		unsigned short prev_weight, new_weight;
+		struct bfq_data *bfqd = NULL;
+		struct rb_root *root;
+#ifdef CONFIG_CGROUP_BFQIO
+		struct bfq_sched_data *sd;
+		struct bfq_group *bfqg;
+#endif
+
+		if (bfqq != NULL)
+			bfqd = bfqq->bfqd;
+#ifdef CONFIG_CGROUP_BFQIO
+		else {
+			sd = entity->my_sched_data;
+			bfqg = container_of(sd, struct bfq_group, sched_data);
+			BUG_ON(!bfqg);
+			bfqd = (struct bfq_data *)bfqg->bfqd;
+			BUG_ON(!bfqd);
+		}
+#endif
+
+		BUG_ON(old_st->wsum < entity->weight);
+		old_st->wsum -= entity->weight;
+
+		if (entity->new_weight != entity->orig_weight) {
+			if (entity->new_weight < BFQ_MIN_WEIGHT ||
+			    entity->new_weight > BFQ_MAX_WEIGHT) {
+				printk(KERN_CRIT "update_weight_prio: "
+						 "new_weight %d\n",
+					entity->new_weight);
+				BUG();
+			}
+			entity->orig_weight = entity->new_weight;
+			entity->ioprio =
+				bfq_weight_to_ioprio(entity->orig_weight);
+		} else if (entity->new_ioprio != entity->ioprio) {
+			entity->ioprio = entity->new_ioprio;
+			entity->orig_weight =
+					bfq_ioprio_to_weight(entity->ioprio);
+		} else
+			entity->new_weight = entity->orig_weight =
+				bfq_ioprio_to_weight(entity->ioprio);
+
+		entity->ioprio_class = entity->new_ioprio_class;
+		entity->ioprio_changed = 0;
+
+		/*
+		 * NOTE: here we may be changing the weight too early,
+		 * this will cause unfairness.  The correct approach
+		 * would have required additional complexity to defer
+		 * weight changes to the proper time instants (i.e.,
+		 * when entity->finish <= old_st->vtime).
+		 */
+		new_st = bfq_entity_service_tree(entity);
+
+		prev_weight = entity->weight;
+		new_weight = entity->orig_weight *
+			     (bfqq != NULL ? bfqq->wr_coeff : 1);
+		/*
+		 * If the weight of the entity changes, remove the entity
+		 * from its old weight counter (if there is a counter
+		 * associated with the entity), and add it to the counter
+		 * associated with its new weight.
+		 */
+		if (prev_weight != new_weight) {
+			root = bfqq ? &bfqd->queue_weights_tree :
+				      &bfqd->group_weights_tree;
+			bfq_weights_tree_remove(bfqd, entity, root);
+		}
+		entity->weight = new_weight;
+		/*
+		 * Add the entity to its weights tree only if it is
+		 * not associated with a weight-raised queue.
+		 */
+		if (prev_weight != new_weight &&
+		    (bfqq ? bfqq->wr_coeff == 1 : 1))
+			/* If we get here, root has been initialized. */
+			bfq_weights_tree_add(bfqd, entity, root);
+
+		new_st->wsum += entity->weight;
+
+		if (new_st != old_st)
+			entity->start = new_st->vtime;
+	}
+
+	return new_st;
+}
+
+/**
+ * bfq_bfqq_served - update the scheduler status after selection for
+ *                   service.
+ * @bfqq: the queue being served.
+ * @served: bytes to transfer.
+ *
+ * NOTE: this can be optimized, as the timestamps of upper level entities
+ * are synchronized every time a new bfqq is selected for service.  By now,
+ * we keep it to better check consistency.
+ */
+static void bfq_bfqq_served(struct bfq_queue *bfqq, unsigned long served)
+{
+	struct bfq_entity *entity = &bfqq->entity;
+	struct bfq_service_tree *st;
+
+	for_each_entity(entity) {
+		st = bfq_entity_service_tree(entity);
+
+		entity->service += served;
+		BUG_ON(entity->service > entity->budget);
+		BUG_ON(st->wsum == 0);
+
+		st->vtime += bfq_delta(served, st->wsum);
+		bfq_forget_idle(st);
+	}
+	bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %lu secs", served);
+}
+
+/**
+ * bfq_bfqq_charge_full_budget - set the service to the entity budget.
+ * @bfqq: the queue that needs a service update.
+ *
+ * When it's not possible to be fair in the service domain, because
+ * a queue is not consuming its budget fast enough (the meaning of
+ * fast depends on the timeout parameter), we charge it a full
+ * budget.  In this way we should obtain a sort of time-domain
+ * fairness among all the seeky/slow queues.
+ */
+static inline void bfq_bfqq_charge_full_budget(struct bfq_queue *bfqq)
+{
+	struct bfq_entity *entity = &bfqq->entity;
+
+	bfq_log_bfqq(bfqq->bfqd, bfqq, "charge_full_budget");
+
+	bfq_bfqq_served(bfqq, entity->budget - entity->service);
+}
+
+/**
+ * __bfq_activate_entity - activate an entity.
+ * @entity: the entity being activated.
+ *
+ * Called whenever an entity is activated, i.e., it is not active and one
+ * of its children receives a new request, or has to be reactivated due to
+ * budget exhaustion.  It uses the current budget of the entity (and the
+ * service received if @entity is active) of the queue to calculate its
+ * timestamps.
+ */
+static void __bfq_activate_entity(struct bfq_entity *entity)
+{
+	struct bfq_sched_data *sd = entity->sched_data;
+	struct bfq_service_tree *st = bfq_entity_service_tree(entity);
+
+	if (entity == sd->in_service_entity) {
+		BUG_ON(entity->tree != NULL);
+		/*
+		 * If we are requeueing the current entity we have
+		 * to take care of not charging to it service it has
+		 * not received.
+		 */
+		bfq_calc_finish(entity, entity->service);
+		entity->start = entity->finish;
+		sd->in_service_entity = NULL;
+	} else if (entity->tree == &st->active) {
+		/*
+		 * Requeueing an entity due to a change of some
+		 * next_in_service entity below it.  We reuse the
+		 * old start time.
+		 */
+		bfq_active_extract(st, entity);
+	} else if (entity->tree == &st->idle) {
+		/*
+		 * Must be on the idle tree, bfq_idle_extract() will
+		 * check for that.
+		 */
+		bfq_idle_extract(st, entity);
+		entity->start = bfq_gt(st->vtime, entity->finish) ?
+				       st->vtime : entity->finish;
+	} else {
+		/*
+		 * The finish time of the entity may be invalid, and
+		 * it is in the past for sure, otherwise the queue
+		 * would have been on the idle tree.
+		 */
+		entity->start = st->vtime;
+		st->wsum += entity->weight;
+		bfq_get_entity(entity);
+
+		BUG_ON(entity->on_st);
+		entity->on_st = 1;
+	}
+
+	st = __bfq_entity_update_weight_prio(st, entity);
+	bfq_calc_finish(entity, entity->budget);
+	bfq_active_insert(st, entity);
+}
+
+/**
+ * bfq_activate_entity - activate an entity and its ancestors if necessary.
+ * @entity: the entity to activate.
+ *
+ * Activate @entity and all the entities on the path from it to the root.
+ */
+static void bfq_activate_entity(struct bfq_entity *entity)
+{
+	struct bfq_sched_data *sd;
+
+	for_each_entity(entity) {
+		__bfq_activate_entity(entity);
+
+		sd = entity->sched_data;
+		if (!bfq_update_next_in_service(sd))
+			/*
+			 * No need to propagate the activation to the
+			 * upper entities, as they will be updated when
+			 * the in-service entity is rescheduled.
+			 */
+			break;
+	}
+}
+
+/**
+ * __bfq_deactivate_entity - deactivate an entity from its service tree.
+ * @entity: the entity to deactivate.
+ * @requeue: if false, the entity will not be put into the idle tree.
+ *
+ * Deactivate an entity, independently from its previous state.  If the
+ * entity was not on a service tree just return, otherwise if it is on
+ * any scheduler tree, extract it from that tree, and if necessary
+ * and if the caller did not specify @requeue, put it on the idle tree.
+ *
+ * Return %1 if the caller should update the entity hierarchy, i.e.,
+ * if the entity was in service or if it was the next_in_service for
+ * its sched_data; return %0 otherwise.
+ */
+static int __bfq_deactivate_entity(struct bfq_entity *entity, int requeue)
+{
+	struct bfq_sched_data *sd = entity->sched_data;
+	struct bfq_service_tree *st = bfq_entity_service_tree(entity);
+	int was_in_service = entity == sd->in_service_entity;
+	int ret = 0;
+
+	if (!entity->on_st)
+		return 0;
+
+	BUG_ON(was_in_service && entity->tree != NULL);
+
+	if (was_in_service) {
+		bfq_calc_finish(entity, entity->service);
+		sd->in_service_entity = NULL;
+	} else if (entity->tree == &st->active)
+		bfq_active_extract(st, entity);
+	else if (entity->tree == &st->idle)
+		bfq_idle_extract(st, entity);
+	else if (entity->tree != NULL)
+		BUG();
+
+	if (was_in_service || sd->next_in_service == entity)
+		ret = bfq_update_next_in_service(sd);
+
+	if (!requeue || !bfq_gt(entity->finish, st->vtime))
+		bfq_forget_entity(st, entity);
+	else
+		bfq_idle_insert(st, entity);
+
+	BUG_ON(sd->in_service_entity == entity);
+	BUG_ON(sd->next_in_service == entity);
+
+	return ret;
+}
+
+/**
+ * bfq_deactivate_entity - deactivate an entity.
+ * @entity: the entity to deactivate.
+ * @requeue: true if the entity can be put on the idle tree
+ */
+static void bfq_deactivate_entity(struct bfq_entity *entity, int requeue)
+{
+	struct bfq_sched_data *sd;
+	struct bfq_entity *parent;
+
+	for_each_entity_safe(entity, parent) {
+		sd = entity->sched_data;
+
+		if (!__bfq_deactivate_entity(entity, requeue))
+			/*
+			 * The parent entity is still backlogged, and
+			 * we don't need to update it as it is still
+			 * in service.
+			 */
+			break;
+
+		if (sd->next_in_service != NULL)
+			/*
+			 * The parent entity is still backlogged and
+			 * the budgets on the path towards the root
+			 * need to be updated.
+			 */
+			goto update;
+
+		/*
+		 * If we reach there the parent is no more backlogged and
+		 * we want to propagate the dequeue upwards.
+		 */
+		requeue = 1;
+	}
+
+	return;
+
+update:
+	entity = parent;
+	for_each_entity(entity) {
+		__bfq_activate_entity(entity);
+
+		sd = entity->sched_data;
+		if (!bfq_update_next_in_service(sd))
+			break;
+	}
+}
+
+/**
+ * bfq_update_vtime - update vtime if necessary.
+ * @st: the service tree to act upon.
+ *
+ * If necessary update the service tree vtime to have at least one
+ * eligible entity, skipping to its start time.  Assumes that the
+ * active tree of the device is not empty.
+ *
+ * NOTE: this hierarchical implementation updates vtimes quite often,
+ * we may end up with reactivated processes getting timestamps after a
+ * vtime skip done because we needed a ->first_active entity on some
+ * intermediate node.
+ */
+static void bfq_update_vtime(struct bfq_service_tree *st)
+{
+	struct bfq_entity *entry;
+	struct rb_node *node = st->active.rb_node;
+
+	entry = rb_entry(node, struct bfq_entity, rb_node);
+	if (bfq_gt(entry->min_start, st->vtime)) {
+		st->vtime = entry->min_start;
+		bfq_forget_idle(st);
+	}
+}
+
+/**
+ * bfq_first_active_entity - find the eligible entity with
+ *                           the smallest finish time
+ * @st: the service tree to select from.
+ *
+ * This function searches the first schedulable entity, starting from the
+ * root of the tree and going on the left every time on this side there is
+ * a subtree with at least one eligible (start >= vtime) entity. The path on
+ * the right is followed only if a) the left subtree contains no eligible
+ * entities and b) no eligible entity has been found yet.
+ */
+static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st)
+{
+	struct bfq_entity *entry, *first = NULL;
+	struct rb_node *node = st->active.rb_node;
+
+	while (node != NULL) {
+		entry = rb_entry(node, struct bfq_entity, rb_node);
+left:
+		if (!bfq_gt(entry->start, st->vtime))
+			first = entry;
+
+		BUG_ON(bfq_gt(entry->min_start, st->vtime));
+
+		if (node->rb_left != NULL) {
+			entry = rb_entry(node->rb_left,
+					 struct bfq_entity, rb_node);
+			if (!bfq_gt(entry->min_start, st->vtime)) {
+				node = node->rb_left;
+				goto left;
+			}
+		}
+		if (first != NULL)
+			break;
+		node = node->rb_right;
+	}
+
+	BUG_ON(first == NULL && !RB_EMPTY_ROOT(&st->active));
+	return first;
+}
+
+/**
+ * __bfq_lookup_next_entity - return the first eligible entity in @st.
+ * @st: the service tree.
+ *
+ * Update the virtual time in @st and return the first eligible entity
+ * it contains.
+ */
+static struct bfq_entity *__bfq_lookup_next_entity(struct bfq_service_tree *st,
+						   bool force)
+{
+	struct bfq_entity *entity, *new_next_in_service = NULL;
+
+	if (RB_EMPTY_ROOT(&st->active))
+		return NULL;
+
+	bfq_update_vtime(st);
+	entity = bfq_first_active_entity(st);
+	BUG_ON(bfq_gt(entity->start, st->vtime));
+
+	/*
+	 * If the chosen entity does not match with the sched_data's
+	 * next_in_service and we are forcedly serving the IDLE priority
+	 * class tree, bubble up budget update.
+	 */
+	if (unlikely(force && entity != entity->sched_data->next_in_service)) {
+		new_next_in_service = entity;
+		for_each_entity(new_next_in_service)
+			bfq_update_budget(new_next_in_service);
+	}
+
+	return entity;
+}
+
+/**
+ * bfq_lookup_next_entity - return the first eligible entity in @sd.
+ * @sd: the sched_data.
+ * @extract: if true the returned entity will be also extracted from @sd.
+ *
+ * NOTE: since we cache the next_in_service entity at each level of the
+ * hierarchy, the complexity of the lookup can be decreased with
+ * absolutely no effort just returning the cached next_in_service value;
+ * we prefer to do full lookups to test the consistency of * the data
+ * structures.
+ */
+static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,
+						 int extract,
+						 struct bfq_data *bfqd)
+{
+	struct bfq_service_tree *st = sd->service_tree;
+	struct bfq_entity *entity;
+	int i = 0;
+
+	BUG_ON(sd->in_service_entity != NULL);
+
+	if (bfqd != NULL &&
+	    jiffies - bfqd->bfq_class_idle_last_service > BFQ_CL_IDLE_TIMEOUT) {
+		entity = __bfq_lookup_next_entity(st + BFQ_IOPRIO_CLASSES - 1,
+						  true);
+		if (entity != NULL) {
+			i = BFQ_IOPRIO_CLASSES - 1;
+			bfqd->bfq_class_idle_last_service = jiffies;
+			sd->next_in_service = entity;
+		}
+	}
+	for (; i < BFQ_IOPRIO_CLASSES; i++) {
+		entity = __bfq_lookup_next_entity(st + i, false);
+		if (entity != NULL) {
+			if (extract) {
+				bfq_check_next_in_service(sd, entity);
+				bfq_active_extract(st + i, entity);
+				sd->in_service_entity = entity;
+				sd->next_in_service = NULL;
+			}
+			break;
+		}
+	}
+
+	return entity;
+}
+
+/*
+ * Get next queue for service.
+ */
+static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)
+{
+	struct bfq_entity *entity = NULL;
+	struct bfq_sched_data *sd;
+	struct bfq_queue *bfqq;
+
+	BUG_ON(bfqd->in_service_queue != NULL);
+
+	if (bfqd->busy_queues == 0)
+		return NULL;
+
+	sd = &bfqd->root_group->sched_data;
+	for (; sd != NULL; sd = entity->my_sched_data) {
+		entity = bfq_lookup_next_entity(sd, 1, bfqd);
+		BUG_ON(entity == NULL);
+		entity->service = 0;
+	}
+
+	bfqq = bfq_entity_to_bfqq(entity);
+	BUG_ON(bfqq == NULL);
+
+	return bfqq;
+}
+
+static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
+{
+	if (bfqd->in_service_bic != NULL) {
+		put_io_context(bfqd->in_service_bic->icq.ioc);
+		bfqd->in_service_bic = NULL;
+	}
+
+	bfqd->in_service_queue = NULL;
+	del_timer(&bfqd->idle_slice_timer);
+}
+
+static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+				int requeue)
+{
+	struct bfq_entity *entity = &bfqq->entity;
+
+	if (bfqq == bfqd->in_service_queue)
+		__bfq_bfqd_reset_in_service(bfqd);
+
+	bfq_deactivate_entity(entity, requeue);
+}
+
+static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+{
+	struct bfq_entity *entity = &bfqq->entity;
+
+	bfq_activate_entity(entity);
+}
+
+/*
+ * Called when the bfqq no longer has requests pending, remove it from
+ * the service tree.
+ */
+static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+			      int requeue)
+{
+	BUG_ON(!bfq_bfqq_busy(bfqq));
+	BUG_ON(!RB_EMPTY_ROOT(&bfqq->sort_list));
+
+	bfq_log_bfqq(bfqd, bfqq, "del from busy");
+
+	bfq_clear_bfqq_busy(bfqq);
+
+	BUG_ON(bfqd->busy_queues == 0);
+	bfqd->busy_queues--;
+
+	if (!bfqq->dispatched) {
+		bfq_weights_tree_remove(bfqd, &bfqq->entity,
+					&bfqd->queue_weights_tree);
+		if (!blk_queue_nonrot(bfqd->queue)) {
+			BUG_ON(!bfqd->busy_in_flight_queues);
+			bfqd->busy_in_flight_queues--;
+			if (bfq_bfqq_constantly_seeky(bfqq)) {
+				BUG_ON(!bfqd->
+					const_seeky_busy_in_flight_queues);
+				bfqd->const_seeky_busy_in_flight_queues--;
+			}
+		}
+	}
+	if (bfqq->wr_coeff > 1)
+		bfqd->wr_busy_queues--;
+
+	bfq_deactivate_bfqq(bfqd, bfqq, requeue);
+}
+
+/*
+ * Called when an inactive queue receives a new request.
+ */
+static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+{
+	BUG_ON(bfq_bfqq_busy(bfqq));
+	BUG_ON(bfqq == bfqd->in_service_queue);
+
+	bfq_log_bfqq(bfqd, bfqq, "add to busy");
+
+	bfq_activate_bfqq(bfqd, bfqq);
+
+	bfq_mark_bfqq_busy(bfqq);
+	bfqd->busy_queues++;
+
+	if (!bfqq->dispatched) {
+		if (bfqq->wr_coeff == 1)
+			bfq_weights_tree_add(bfqd, &bfqq->entity,
+					     &bfqd->queue_weights_tree);
+		if (!blk_queue_nonrot(bfqd->queue)) {
+			bfqd->busy_in_flight_queues++;
+			if (bfq_bfqq_constantly_seeky(bfqq))
+				bfqd->const_seeky_busy_in_flight_queues++;
+		}
+	}
+	if (bfqq->wr_coeff > 1)
+		bfqd->wr_busy_queues++;
+}
diff --git a/block/bfq.h b/block/bfq.h
new file mode 100644
index 0000000..9428d71
--- /dev/null
+++ b/block/bfq.h
@@ -0,0 +1,809 @@
+/*
+ * BFQ-v7r7 for 3.4.0: data structures and common functions prototypes.
+ *
+ * Based on ideas and code from CFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
+ *		      Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
+ */
+
+#ifndef _BFQ_H
+#define _BFQ_H
+
+#include <linux/blktrace_api.h>
+#include <linux/hrtimer.h>
+#include <linux/ioprio.h>
+#include <linux/rbtree.h>
+
+#define BFQ_IOPRIO_CLASSES	3
+#define BFQ_CL_IDLE_TIMEOUT	(HZ/5)
+
+#define BFQ_MIN_WEIGHT	1
+#define BFQ_MAX_WEIGHT	1000
+
+#define BFQ_DEFAULT_QUEUE_IOPRIO	4
+
+#define BFQ_DEFAULT_GRP_WEIGHT	10
+#define BFQ_DEFAULT_GRP_IOPRIO	0
+#define BFQ_DEFAULT_GRP_CLASS	IOPRIO_CLASS_BE
+
+struct bfq_entity;
+
+/**
+ * struct bfq_service_tree - per ioprio_class service tree.
+ * @active: tree for active entities (i.e., those backlogged).
+ * @idle: tree for idle entities (i.e., those not backlogged, with V <= F_i).
+ * @first_idle: idle entity with minimum F_i.
+ * @last_idle: idle entity with maximum F_i.
+ * @vtime: scheduler virtual time.
+ * @wsum: scheduler weight sum; active and idle entities contribute to it.
+ *
+ * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
+ * ioprio_class has its own independent scheduler, and so its own
+ * bfq_service_tree.  All the fields are protected by the queue lock
+ * of the containing bfqd.
+ */
+struct bfq_service_tree {
+	struct rb_root active;
+	struct rb_root idle;
+
+	struct bfq_entity *first_idle;
+	struct bfq_entity *last_idle;
+
+	u64 vtime;
+	unsigned long wsum;
+};
+
+/**
+ * struct bfq_sched_data - multi-class scheduler.
+ * @in_service_entity: entity in service.
+ * @next_in_service: head-of-the-line entity in the scheduler.
+ * @service_tree: array of service trees, one per ioprio_class.
+ *
+ * bfq_sched_data is the basic scheduler queue.  It supports three
+ * ioprio_classes, and can be used either as a toplevel queue or as
+ * an intermediate queue on a hierarchical setup.
+ * @next_in_service points to the active entity of the sched_data
+ * service trees that will be scheduled next.
+ *
+ * The supported ioprio_classes are the same as in CFQ, in descending
+ * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
+ * Requests from higher priority queues are served before all the
+ * requests from lower priority queues; among requests of the same
+ * queue requests are served according to B-WF2Q+.
+ * All the fields are protected by the queue lock of the containing bfqd.
+ */
+struct bfq_sched_data {
+	struct bfq_entity *in_service_entity;
+	struct bfq_entity *next_in_service;
+	struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
+};
+
+/**
+ * struct bfq_weight_counter - counter of the number of all active entities
+ *                             with a given weight.
+ * @weight: weight of the entities that this counter refers to.
+ * @num_active: number of active entities with this weight.
+ * @weights_node: weights tree member (see bfq_data's @queue_weights_tree
+ *                and @group_weights_tree).
+ */
+struct bfq_weight_counter {
+	short int weight;
+	unsigned int num_active;
+	struct rb_node weights_node;
+};
+
+/**
+ * struct bfq_entity - schedulable entity.
+ * @rb_node: service_tree member.
+ * @weight_counter: pointer to the weight counter associated with this entity.
+ * @on_st: flag, true if the entity is on a tree (either the active or
+ *         the idle one of its service_tree).
+ * @finish: B-WF2Q+ finish timestamp (aka F_i).
+ * @start: B-WF2Q+ start timestamp (aka S_i).
+ * @tree: tree the entity is enqueued into; %NULL if not on a tree.
+ * @min_start: minimum start time of the (active) subtree rooted at
+ *             this entity; used for O(log N) lookups into active trees.
+ * @service: service received during the last round of service.
+ * @budget: budget used to calculate F_i; F_i = S_i + @budget / @weight.
+ * @weight: weight of the queue
+ * @parent: parent entity, for hierarchical scheduling.
+ * @my_sched_data: for non-leaf nodes in the cgroup hierarchy, the
+ *                 associated scheduler queue, %NULL on leaf nodes.
+ * @sched_data: the scheduler queue this entity belongs to.
+ * @ioprio: the ioprio in use.
+ * @new_weight: when a weight change is requested, the new weight value.
+ * @orig_weight: original weight, used to implement weight boosting
+ * @new_ioprio: when an ioprio change is requested, the new ioprio value.
+ * @ioprio_class: the ioprio_class in use.
+ * @new_ioprio_class: when an ioprio_class change is requested, the new
+ *                    ioprio_class value.
+ * @ioprio_changed: flag, true when the user requested a weight, ioprio or
+ *                  ioprio_class change.
+ *
+ * A bfq_entity is used to represent either a bfq_queue (leaf node in the
+ * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
+ * entity belongs to the sched_data of the parent group in the cgroup
+ * hierarchy.  Non-leaf entities have also their own sched_data, stored
+ * in @my_sched_data.
+ *
+ * Each entity stores independently its priority values; this would
+ * allow different weights on different devices, but this
+ * functionality is not exported to userspace by now.  Priorities and
+ * weights are updated lazily, first storing the new values into the
+ * new_* fields, then setting the @ioprio_changed flag.  As soon as
+ * there is a transition in the entity state that allows the priority
+ * update to take place the effective and the requested priority
+ * values are synchronized.
+ *
+ * Unless cgroups are used, the weight value is calculated from the
+ * ioprio to export the same interface as CFQ.  When dealing with
+ * ``well-behaved'' queues (i.e., queues that do not spend too much
+ * time to consume their budget and have true sequential behavior, and
+ * when there are no external factors breaking anticipation) the
+ * relative weights at each level of the cgroups hierarchy should be
+ * guaranteed.  All the fields are protected by the queue lock of the
+ * containing bfqd.
+ */
+struct bfq_entity {
+	struct rb_node rb_node;
+	struct bfq_weight_counter *weight_counter;
+
+	int on_st;
+
+	u64 finish;
+	u64 start;
+
+	struct rb_root *tree;
+
+	u64 min_start;
+
+	unsigned long service, budget;
+	unsigned short weight, new_weight;
+	unsigned short orig_weight;
+
+	struct bfq_entity *parent;
+
+	struct bfq_sched_data *my_sched_data;
+	struct bfq_sched_data *sched_data;
+
+	unsigned short ioprio, new_ioprio;
+	unsigned short ioprio_class, new_ioprio_class;
+
+	int ioprio_changed;
+};
+
+struct bfq_group;
+
+/**
+ * struct bfq_queue - leaf schedulable entity.
+ * @ref: reference counter.
+ * @bfqd: parent bfq_data.
+ * @new_bfqq: shared bfq_queue if queue is cooperating with
+ *           one or more other queues.
+ * @pos_node: request-position tree member (see bfq_data's @rq_pos_tree).
+ * @pos_root: request-position tree root (see bfq_data's @rq_pos_tree).
+ * @sort_list: sorted list of pending requests.
+ * @next_rq: if fifo isn't expired, next request to serve.
+ * @queued: nr of requests queued in @sort_list.
+ * @allocated: currently allocated requests.
+ * @meta_pending: pending metadata requests.
+ * @fifo: fifo list of requests in sort_list.
+ * @entity: entity representing this queue in the scheduler.
+ * @max_budget: maximum budget allowed from the feedback mechanism.
+ * @budget_timeout: budget expiration (in jiffies).
+ * @dispatched: number of requests on the dispatch list or inside driver.
+ * @flags: status flags.
+ * @bfqq_list: node for active/idle bfqq list inside our bfqd.
+ * @burst_list_node: node for the device's burst list.
+ * @seek_samples: number of seeks sampled
+ * @seek_total: sum of the distances of the seeks sampled
+ * @seek_mean: mean seek distance
+ * @last_request_pos: position of the last request enqueued
+ * @requests_within_timer: number of consecutive pairs of request completion
+ *                         and arrival, such that the queue becomes idle
+ *                         after the completion, but the next request arrives
+ *                         within an idle time slice; used only if the queue's
+ *                         IO_bound has been cleared.
+ * @pid: pid of the process owning the queue, used for logging purposes.
+ * @last_wr_start_finish: start time of the current weight-raising period if
+ *                        the @bfq-queue is being weight-raised, otherwise
+ *                        finish time of the last weight-raising period
+ * @wr_cur_max_time: current max raising time for this queue
+ * @soft_rt_next_start: minimum time instant such that, only if a new
+ *                      request is enqueued after this time instant in an
+ *                      idle @bfq_queue with no outstanding requests, then
+ *                      the task associated with the queue it is deemed as
+ *                      soft real-time (see the comments to the function
+ *                      bfq_bfqq_softrt_next_start())
+ * @last_idle_bklogged: time of the last transition of the @bfq_queue from
+ *                      idle to backlogged
+ * @service_from_backlogged: cumulative service received from the @bfq_queue
+ *                           since the last transition from idle to
+ *                           backlogged
+ * @bic: pointer to the bfq_io_cq owning the bfq_queue, set to %NULL if the
+ *	 queue is shared
+ *
+ * A bfq_queue is a leaf request queue; it can be associated with an
+ * io_context or more, if it  is  async or shared  between  cooperating
+ * processes. @cgroup holds a reference to the cgroup, to be sure that it
+ * does not disappear while a bfqq still references it (mostly to avoid
+ * races between request issuing and task migration followed by cgroup
+ * destruction).
+ * All the fields are protected by the queue lock of the containing bfqd.
+ */
+struct bfq_queue {
+	atomic_t ref;
+	struct bfq_data *bfqd;
+
+	/* fields for cooperating queues handling */
+	struct bfq_queue *new_bfqq;
+	struct rb_node pos_node;
+	struct rb_root *pos_root;
+
+	struct rb_root sort_list;
+	struct request *next_rq;
+	int queued[2];
+	int allocated[2];
+	int meta_pending;
+	struct list_head fifo;
+
+	struct bfq_entity entity;
+
+	unsigned long max_budget;
+	unsigned long budget_timeout;
+
+	int dispatched;
+
+	unsigned int flags;
+
+	struct list_head bfqq_list;
+
+	struct hlist_node burst_list_node;
+
+	unsigned int seek_samples;
+	u64 seek_total;
+	sector_t seek_mean;
+	sector_t last_request_pos;
+
+	unsigned int requests_within_timer;
+
+	pid_t pid;
+	struct bfq_io_cq *bic;
+
+	/* weight-raising fields */
+	unsigned long wr_cur_max_time;
+	unsigned long soft_rt_next_start;
+	unsigned long last_wr_start_finish;
+	unsigned int wr_coeff;
+	unsigned long last_idle_bklogged;
+	unsigned long service_from_backlogged;
+};
+
+/**
+ * struct bfq_ttime - per process thinktime stats.
+ * @ttime_total: total process thinktime
+ * @ttime_samples: number of thinktime samples
+ * @ttime_mean: average process thinktime
+ */
+struct bfq_ttime {
+	unsigned long last_end_request;
+
+	unsigned long ttime_total;
+	unsigned long ttime_samples;
+	unsigned long ttime_mean;
+};
+
+/**
+ * struct bfq_io_cq - per (request_queue, io_context) structure.
+ * @icq: associated io_cq structure
+ * @bfqq: array of two process queues, the sync and the async
+ * @ttime: associated @bfq_ttime struct
+ * @wr_time_left: snapshot of the time left before weight raising ends
+ *                for the sync queue associated to this process; this
+ *		  snapshot is taken to remember this value while the weight
+ *		  raising is suspended because the queue is merged with a
+ *		  shared queue, and is used to set @raising_cur_max_time
+ *		  when the queue is split from the shared queue and its
+ *		  weight is raised again
+ * @saved_idle_window: same purpose as the previous field for the idle
+ *                     window
+ * @saved_IO_bound: same purpose as the previous two fields for the I/O
+ *                  bound classification of a queue
+ * @saved_in_large_burst: same purpose as the previous fields for the
+ *                        value of the field keeping the queue's belonging
+ *                        to a large burst
+ * @was_in_burst_list: true if the queue belonged to a burst list
+ *                     before its merge with another cooperating queue
+ * @cooperations: counter of consecutive successful queue merges underwent
+ *                by any of the process' @bfq_queues
+ * @failed_cooperations: counter of consecutive failed queue merges of any
+ *                       of the process' @bfq_queues
+ */
+struct bfq_io_cq {
+	struct io_cq icq; /* must be the first member */
+	struct bfq_queue *bfqq[2];
+	struct bfq_ttime ttime;
+
+	unsigned int wr_time_left;
+	bool saved_idle_window;
+	bool saved_IO_bound;
+
+	bool saved_in_large_burst;
+	bool was_in_burst_list;
+
+	unsigned int cooperations;
+	unsigned int failed_cooperations;
+};
+
+enum bfq_device_speed {
+	BFQ_BFQD_FAST,
+	BFQ_BFQD_SLOW,
+};
+
+/**
+ * struct bfq_data - per device data structure.
+ * @queue: request queue for the managed device.
+ * @root_group: root bfq_group for the device.
+ * @rq_pos_tree: rbtree sorted by next_request position, used when
+ *               determining if two or more queues have interleaving
+ *               requests (see bfq_close_cooperator()).
+ * @active_numerous_groups: number of bfq_groups containing more than one
+ *                          active @bfq_entity.
+ * @queue_weights_tree: rbtree of weight counters of @bfq_queues, sorted by
+ *                      weight. Used to keep track of whether all @bfq_queues
+ *                     have the same weight. The tree contains one counter
+ *                     for each distinct weight associated to some active
+ *                     and not weight-raised @bfq_queue (see the comments to
+ *                      the functions bfq_weights_tree_[add|remove] for
+ *                     further details).
+ * @group_weights_tree: rbtree of non-queue @bfq_entity weight counters, sorted
+ *                      by weight. Used to keep track of whether all
+ *                     @bfq_groups have the same weight. The tree contains
+ *                     one counter for each distinct weight associated to
+ *                     some active @bfq_group (see the comments to the
+ *                     functions bfq_weights_tree_[add|remove] for further
+ *                     details).
+ * @busy_queues: number of bfq_queues containing requests (including the
+ *		 queue in service, even if it is idling).
+ * @busy_in_flight_queues: number of @bfq_queues containing pending or
+ *                         in-flight requests, plus the @bfq_queue in
+ *                         service, even if idle but waiting for the
+ *                         possible arrival of its next sync request. This
+ *                         field is updated only if the device is rotational,
+ *                         but used only if the device is also NCQ-capable.
+ *                         The reason why the field is updated also for non-
+ *                         NCQ-capable rotational devices is related to the
+ *                         fact that the value of @hw_tag may be set also
+ *                         later than when busy_in_flight_queues may need to
+ *                         be incremented for the first time(s). Taking also
+ *                         this possibility into account, to avoid unbalanced
+ *                         increments/decrements, would imply more overhead
+ *                         than just updating busy_in_flight_queues
+ *                         regardless of the value of @hw_tag.
+ * @const_seeky_busy_in_flight_queues: number of constantly-seeky @bfq_queues
+ *                                     (that is, seeky queues that expired
+ *                                     for budget timeout at least once)
+ *                                     containing pending or in-flight
+ *                                     requests, including the in-service
+ *                                     @bfq_queue if constantly seeky. This
+ *                                     field is updated only if the device
+ *                                     is rotational, but used only if the
+ *                                     device is also NCQ-capable (see the
+ *                                     comments to @busy_in_flight_queues).
+ * @wr_busy_queues: number of weight-raised busy @bfq_queues.
+ * @queued: number of queued requests.
+ * @rq_in_driver: number of requests dispatched and waiting for completion.
+ * @sync_flight: number of sync requests in the driver.
+ * @max_rq_in_driver: max number of reqs in driver in the last
+ *                    @hw_tag_samples completed requests.
+ * @hw_tag_samples: nr of samples used to calculate hw_tag.
+ * @hw_tag: flag set to one if the driver is showing a queueing behavior.
+ * @budgets_assigned: number of budgets assigned.
+ * @idle_slice_timer: timer set when idling for the next sequential request
+ *                    from the queue in service.
+ * @unplug_work: delayed work to restart dispatching on the request queue.
+ * @in_service_queue: bfq_queue in service.
+ * @in_service_bic: bfq_io_cq (bic) associated with the @in_service_queue.
+ * @last_position: on-disk position of the last served request.
+ * @last_budget_start: beginning of the last budget.
+ * @last_idling_start: beginning of the last idle slice.
+ * @peak_rate: peak transfer rate observed for a budget.
+ * @peak_rate_samples: number of samples used to calculate @peak_rate.
+ * @bfq_max_budget: maximum budget allotted to a bfq_queue before
+ *                  rescheduling.
+ * @group_list: list of all the bfq_groups active on the device.
+ * @active_list: list of all the bfq_queues active on the device.
+ * @idle_list: list of all the bfq_queues idle on the device.
+ * @bfq_quantum: max number of requests dispatched per dispatch round.
+ * @bfq_fifo_expire: timeout for async/sync requests; when it expires
+ *                   requests are served in fifo order.
+ * @bfq_back_penalty: weight of backward seeks wrt forward ones.
+ * @bfq_back_max: maximum allowed backward seek.
+ * @bfq_slice_idle: maximum idling time.
+ * @bfq_user_max_budget: user-configured max budget value
+ *                       (0 for auto-tuning).
+ * @bfq_max_budget_async_rq: maximum budget (in nr of requests) allotted to
+ *                           async queues.
+ * @bfq_timeout: timeout for bfq_queues to consume their budget; used to
+ *               to prevent seeky queues to impose long latencies to well
+ *               behaved ones (this also implies that seeky queues cannot
+ *               receive guarantees in the service domain; after a timeout
+ *               they are charged for the whole allocated budget, to try
+ *               to preserve a behavior reasonably fair among them, but
+ *               without service-domain guarantees).
+ * @bfq_coop_thresh: number of queue merges after which a @bfq_queue is
+ *                   no more granted any weight-raising.
+ * @bfq_failed_cooperations: number of consecutive failed cooperation
+ *                           chances after which weight-raising is restored
+ *                           to a queue subject to more than bfq_coop_thresh
+ *                           queue merges.
+ * @bfq_requests_within_timer: number of consecutive requests that must be
+ *                             issued within the idle time slice to set
+ *                             again idling to a queue which was marked as
+ *                             non-I/O-bound (see the definition of the
+ *                             IO_bound flag for further details).
+ * @last_ins_in_burst: last time at which a queue entered the current
+ *                     burst of queues being activated shortly after
+ *                     each other; for more details about this and the
+ *                     following parameters related to a burst of
+ *                     activations, see the comments to the function
+ *                     @bfq_handle_burst.
+ * @bfq_burst_interval: reference time interval used to decide whether a
+ *                      queue has been activated shortly after
+ *                      @last_ins_in_burst.
+ * @burst_size: number of queues in the current burst of queue activations.
+ * @bfq_large_burst_thresh: maximum burst size above which the current
+ * 			    queue-activation burst is deemed as 'large'.
+ * @large_burst: true if a large queue-activation burst is in progress.
+ * @burst_list: head of the burst list (as for the above fields, more details
+ * 		in the comments to the function bfq_handle_burst).
+ * @low_latency: if set to true, low-latency heuristics are enabled.
+ * @bfq_wr_coeff: maximum factor by which the weight of a weight-raised
+ *                queue is multiplied.
+ * @bfq_wr_max_time: maximum duration of a weight-raising period (jiffies).
+ * @bfq_wr_rt_max_time: maximum duration for soft real-time processes.
+ * @bfq_wr_min_idle_time: minimum idle period after which weight-raising
+ *			  may be reactivated for a queue (in jiffies).
+ * @bfq_wr_min_inter_arr_async: minimum period between request arrivals
+ *				after which weight-raising may be
+ *				reactivated for an already busy queue
+ *				(in jiffies).
+ * @bfq_wr_max_softrt_rate: max service-rate for a soft real-time queue,
+ *			    sectors per seconds.
+ * @RT_prod: cached value of the product R*T used for computing the maximum
+ *	     duration of the weight raising automatically.
+ * @device_speed: device-speed class for the low-latency heuristic.
+ * @oom_bfqq: fallback dummy bfqq for extreme OOM conditions.
+ *
+ * All the fields are protected by the @queue lock.
+ */
+struct bfq_data {
+	struct request_queue *queue;
+
+	struct bfq_group *root_group;
+	struct rb_root rq_pos_tree;
+
+#ifdef CONFIG_CGROUP_BFQIO
+	int active_numerous_groups;
+#endif
+
+	struct rb_root queue_weights_tree;
+	struct rb_root group_weights_tree;
+
+	int busy_queues;
+	int busy_in_flight_queues;
+	int const_seeky_busy_in_flight_queues;
+	int wr_busy_queues;
+	int queued;
+	int rq_in_driver;
+	int sync_flight;
+
+	int max_rq_in_driver;
+	int hw_tag_samples;
+	int hw_tag;
+
+	int budgets_assigned;
+
+	struct timer_list idle_slice_timer;
+	struct work_struct unplug_work;
+
+	struct bfq_queue *in_service_queue;
+	struct bfq_io_cq *in_service_bic;
+
+	sector_t last_position;
+
+	ktime_t last_budget_start;
+	ktime_t last_idling_start;
+	int peak_rate_samples;
+	u64 peak_rate;
+	unsigned long bfq_max_budget;
+
+	struct hlist_head group_list;
+	struct list_head active_list;
+	struct list_head idle_list;
+
+	unsigned int bfq_quantum;
+	unsigned int bfq_fifo_expire[2];
+	unsigned int bfq_back_penalty;
+	unsigned int bfq_back_max;
+	unsigned int bfq_slice_idle;
+	u64 bfq_class_idle_last_service;
+
+	unsigned int bfq_user_max_budget;
+	unsigned int bfq_max_budget_async_rq;
+	unsigned int bfq_timeout[2];
+
+	unsigned int bfq_coop_thresh;
+	unsigned int bfq_failed_cooperations;
+	unsigned int bfq_requests_within_timer;
+
+	unsigned long last_ins_in_burst;
+	unsigned long bfq_burst_interval;
+	int burst_size;
+	unsigned long bfq_large_burst_thresh;
+	bool large_burst;
+	struct hlist_head burst_list;
+
+	bool low_latency;
+
+	/* parameters of the low_latency heuristics */
+	unsigned int bfq_wr_coeff;
+	unsigned int bfq_wr_max_time;
+	unsigned int bfq_wr_rt_max_time;
+	unsigned int bfq_wr_min_idle_time;
+	unsigned long bfq_wr_min_inter_arr_async;
+	unsigned int bfq_wr_max_softrt_rate;
+	u64 RT_prod;
+	enum bfq_device_speed device_speed;
+
+	struct bfq_queue oom_bfqq;
+};
+
+enum bfqq_state_flags {
+	BFQ_BFQQ_FLAG_busy = 0,		/* has requests or is in service */
+	BFQ_BFQQ_FLAG_wait_request,	/* waiting for a request */
+	BFQ_BFQQ_FLAG_must_alloc,	/* must be allowed rq alloc */
+	BFQ_BFQQ_FLAG_fifo_expire,	/* FIFO checked in this slice */
+	BFQ_BFQQ_FLAG_idle_window,	/* slice idling enabled */
+	BFQ_BFQQ_FLAG_prio_changed,	/* task priority has changed */
+	BFQ_BFQQ_FLAG_sync,		/* synchronous queue */
+	BFQ_BFQQ_FLAG_budget_new,	/* no completion with this budget */
+	BFQ_BFQQ_FLAG_IO_bound,		/*
+					 * bfqq has timed-out at least once
+					 * having consumed at most 2/10 of
+					 * its budget
+					 */
+	BFQ_BFQQ_FLAG_in_large_burst,	/*
+					 * bfqq activated in a large burst,
+					 * see comments to bfq_handle_burst.
+					 */
+	BFQ_BFQQ_FLAG_constantly_seeky,	/*
+					 * bfqq has proved to be slow and
+					 * seeky until budget timeout
+					 */
+	BFQ_BFQQ_FLAG_softrt_update,	/*
+					 * may need softrt-next-start
+					 * update
+					 */
+	BFQ_BFQQ_FLAG_coop,		/* bfqq is shared */
+	BFQ_BFQQ_FLAG_split_coop,	/* shared bfqq will be split */
+	BFQ_BFQQ_FLAG_just_split,	/* queue has just been split */
+};
+
+#define BFQ_BFQQ_FNS(name)						\
+static inline void bfq_mark_bfqq_##name(struct bfq_queue *bfqq)		\
+{									\
+	(bfqq)->flags |= (1 << BFQ_BFQQ_FLAG_##name);			\
+}									\
+static inline void bfq_clear_bfqq_##name(struct bfq_queue *bfqq)	\
+{									\
+	(bfqq)->flags &= ~(1 << BFQ_BFQQ_FLAG_##name);			\
+}									\
+static inline int bfq_bfqq_##name(const struct bfq_queue *bfqq)		\
+{									\
+	return ((bfqq)->flags & (1 << BFQ_BFQQ_FLAG_##name)) != 0;	\
+}
+
+BFQ_BFQQ_FNS(busy);
+BFQ_BFQQ_FNS(wait_request);
+BFQ_BFQQ_FNS(must_alloc);
+BFQ_BFQQ_FNS(fifo_expire);
+BFQ_BFQQ_FNS(idle_window);
+BFQ_BFQQ_FNS(prio_changed);
+BFQ_BFQQ_FNS(sync);
+BFQ_BFQQ_FNS(budget_new);
+BFQ_BFQQ_FNS(IO_bound);
+BFQ_BFQQ_FNS(in_large_burst);
+BFQ_BFQQ_FNS(constantly_seeky);
+BFQ_BFQQ_FNS(coop);
+BFQ_BFQQ_FNS(split_coop);
+BFQ_BFQQ_FNS(just_split);
+BFQ_BFQQ_FNS(softrt_update);
+#undef BFQ_BFQQ_FNS
+
+/* Logging facilities. */
+#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \
+	blk_add_trace_msg((bfqd)->queue, "bfq%d " fmt, (bfqq)->pid, ##args)
+
+#define bfq_log(bfqd, fmt, args...) \
+	blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
+
+/* Expiration reasons. */
+enum bfqq_expiration {
+	BFQ_BFQQ_TOO_IDLE = 0,		/*
+					 * queue has been idling for
+					 * too long
+					 */
+	BFQ_BFQQ_BUDGET_TIMEOUT,	/* budget took too long to be used */
+	BFQ_BFQQ_BUDGET_EXHAUSTED,	/* budget consumed */
+	BFQ_BFQQ_NO_MORE_REQUESTS,	/* the queue has no more requests */
+};
+
+#ifdef CONFIG_CGROUP_BFQIO
+/**
+ * struct bfq_group - per (device, cgroup) data structure.
+ * @entity: schedulable entity to insert into the parent group sched_data.
+ * @sched_data: own sched_data, to contain child entities (they may be
+ *              both bfq_queues and bfq_groups).
+ * @group_node: node to be inserted into the bfqio_cgroup->group_data
+ *              list of the containing cgroup's bfqio_cgroup.
+ * @bfqd_node: node to be inserted into the @bfqd->group_list list
+ *             of the groups active on the same device; used for cleanup.
+ * @bfqd: the bfq_data for the device this group acts upon.
+ * @async_bfqq: array of async queues for all the tasks belonging to
+ *              the group, one queue per ioprio value per ioprio_class,
+ *              except for the idle class that has only one queue.
+ * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
+ * @my_entity: pointer to @entity, %NULL for the toplevel group; used
+ *             to avoid too many special cases during group creation/
+ *             migration.
+ * @active_entities: number of active entities belonging to the group;
+ *                   unused for the root group. Used to know whether there
+ *                   are groups with more than one active @bfq_entity
+ *                   (see the comments to the function
+ *                   bfq_bfqq_must_not_expire()).
+ *
+ * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
+ * there is a set of bfq_groups, each one collecting the lower-level
+ * entities belonging to the group that are acting on the same device.
+ *
+ * Locking works as follows:
+ *    o @group_node is protected by the bfqio_cgroup lock, and is accessed
+ *      via RCU from its readers.
+ *    o @bfqd is protected by the queue lock, RCU is used to access it
+ *      from the readers.
+ *    o All the other fields are protected by the @bfqd queue lock.
+ */
+struct bfq_group {
+	struct bfq_entity entity;
+	struct bfq_sched_data sched_data;
+
+	struct hlist_node group_node;
+	struct hlist_node bfqd_node;
+
+	void *bfqd;
+
+	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
+	struct bfq_queue *async_idle_bfqq;
+
+	struct bfq_entity *my_entity;
+
+	int active_entities;
+};
+
+/**
+ * struct bfqio_cgroup - bfq cgroup data structure.
+ * @css: subsystem state for bfq in the containing cgroup.
+ * @weight: cgroup weight.
+ * @ioprio: cgroup ioprio.
+ * @ioprio_class: cgroup ioprio_class.
+ * @lock: spinlock that protects @ioprio, @ioprio_class and @group_data.
+ * @group_data: list containing the bfq_group belonging to this cgroup.
+ *
+ * @group_data is accessed using RCU, with @lock protecting the updates,
+ * @ioprio and @ioprio_class are protected by @lock.
+ */
+struct bfqio_cgroup {
+	struct cgroup_subsys_state css;
+
+	unsigned short weight, ioprio, ioprio_class;
+
+	spinlock_t lock;
+	struct hlist_head group_data;
+};
+#else
+struct bfq_group {
+	struct bfq_sched_data sched_data;
+
+	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
+	struct bfq_queue *async_idle_bfqq;
+};
+#endif
+
+static inline struct bfq_service_tree *
+bfq_entity_service_tree(struct bfq_entity *entity)
+{
+	struct bfq_sched_data *sched_data = entity->sched_data;
+	unsigned int idx = entity->ioprio_class - 1;
+
+	BUG_ON(idx >= BFQ_IOPRIO_CLASSES);
+	BUG_ON(sched_data == NULL);
+
+	return sched_data->service_tree + idx;
+}
+
+static inline struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic,
+					    bool is_sync)
+{
+	return bic->bfqq[is_sync];
+}
+
+static inline void bic_set_bfqq(struct bfq_io_cq *bic,
+				struct bfq_queue *bfqq, bool is_sync)
+{
+	bic->bfqq[is_sync] = bfqq;
+}
+
+static inline struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic)
+{
+	return bic->icq.q->elevator->elevator_data;
+}
+
+/**
+ * bfq_get_bfqd_locked - get a lock to a bfqd using a RCU protected pointer.
+ * @ptr: a pointer to a bfqd.
+ * @flags: storage for the flags to be saved.
+ *
+ * This function allows bfqg->bfqd to be protected by the
+ * queue lock of the bfqd they reference; the pointer is dereferenced
+ * under RCU, so the storage for bfqd is assured to be safe as long
+ * as the RCU read side critical section does not end.  After the
+ * bfqd->queue->queue_lock is taken the pointer is rechecked, to be
+ * sure that no other writer accessed it.  If we raced with a writer,
+ * the function returns NULL, with the queue unlocked, otherwise it
+ * returns the dereferenced pointer, with the queue locked.
+ */
+static inline struct bfq_data *bfq_get_bfqd_locked(void **ptr,
+						   unsigned long *flags)
+{
+	struct bfq_data *bfqd;
+
+	rcu_read_lock();
+	bfqd = rcu_dereference(*(struct bfq_data **)ptr);
+
+	if (bfqd != NULL) {
+		spin_lock_irqsave(bfqd->queue->queue_lock, *flags);
+		if (*ptr == bfqd)
+			goto out;
+		spin_unlock_irqrestore(bfqd->queue->queue_lock, *flags);
+	}
+
+	bfqd = NULL;
+out:
+	rcu_read_unlock();
+	return bfqd;
+}
+
+static inline void bfq_put_bfqd_unlock(struct bfq_data *bfqd,
+				       unsigned long *flags)
+{
+	spin_unlock_irqrestore(bfqd->queue->queue_lock, *flags);
+}
+
+static void bfq_changed_ioprio(struct io_context *ioc,
+			       struct bfq_io_cq *bic);
+static void bfq_put_queue(struct bfq_queue *bfqq);
+static void bfq_dispatch_insert(struct request_queue *q, struct request *rq);
+static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
+				       struct bfq_group *bfqg, int is_sync,
+				       struct io_context *ioc, gfp_t gfp_mask);
+static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
+				    struct bfq_group *bfqg);
+static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
+static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
+
+#endif /* _BFQ_H */
diff --git a/block/fiops-iosched.c b/block/fiops-iosched.c
new file mode 100644
index 0000000..671b1d3
--- /dev/null
+++ b/block/fiops-iosched.c
@@ -0,0 +1,753 @@
+/*
+ * IOPS based IO scheduler. Based on CFQ.
+ *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ *  Shaohua Li <shli@kernel.org>
+ */
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/jiffies.h>
+#include <linux/rbtree.h>
+#include <linux/ioprio.h>
+#include <linux/blktrace_api.h>
+#include "blk.h"
+
+#define VIOS_SCALE_SHIFT 10
+#define VIOS_SCALE (1 << VIOS_SCALE_SHIFT)
+
+#define VIOS_READ_SCALE (1)
+#define VIOS_WRITE_SCALE (1)
+#define VIOS_SYNC_SCALE (2)
+#define VIOS_ASYNC_SCALE (5)
+
+#define VIOS_PRIO_SCALE (5)
+
+struct fiops_rb_root {
+	struct rb_root rb;
+	struct rb_node *left;
+	unsigned count;
+
+	u64 min_vios;
+};
+#define FIOPS_RB_ROOT	(struct fiops_rb_root) { .rb = RB_ROOT}
+
+enum wl_prio_t {
+	IDLE_WORKLOAD = 0,
+	BE_WORKLOAD = 1,
+	RT_WORKLOAD = 2,
+	FIOPS_PRIO_NR,
+};
+
+struct fiops_data {
+	struct request_queue *queue;
+
+	struct fiops_rb_root service_tree[FIOPS_PRIO_NR];
+
+	unsigned int busy_queues;
+	unsigned int in_flight[2];
+
+	struct work_struct unplug_work;
+
+	unsigned int read_scale;
+	unsigned int write_scale;
+	unsigned int sync_scale;
+	unsigned int async_scale;
+};
+
+struct fiops_ioc {
+	struct io_cq icq;
+
+	unsigned int flags;
+	struct fiops_data *fiopsd;
+	struct rb_node rb_node;
+	u64 vios; /* key in service_tree */
+	struct fiops_rb_root *service_tree;
+
+	unsigned int in_flight;
+
+	struct rb_root sort_list;
+	struct list_head fifo;
+
+	pid_t pid;
+	unsigned short ioprio;
+	enum wl_prio_t wl_type;
+};
+
+#define ioc_service_tree(ioc) (&((ioc)->fiopsd->service_tree[(ioc)->wl_type]))
+#define RQ_CIC(rq)		icq_to_cic((rq)->elv.icq)
+
+enum ioc_state_flags {
+	FIOPS_IOC_FLAG_on_rr = 0,	/* on round-robin busy list */
+	FIOPS_IOC_FLAG_prio_changed,	/* task priority has changed */
+};
+
+#define FIOPS_IOC_FNS(name)						\
+static inline void fiops_mark_ioc_##name(struct fiops_ioc *ioc)	\
+{									\
+	ioc->flags |= (1 << FIOPS_IOC_FLAG_##name);			\
+}									\
+static inline void fiops_clear_ioc_##name(struct fiops_ioc *ioc)	\
+{									\
+	ioc->flags &= ~(1 << FIOPS_IOC_FLAG_##name);			\
+}									\
+static inline int fiops_ioc_##name(const struct fiops_ioc *ioc)	\
+{									\
+	return ((ioc)->flags & (1 << FIOPS_IOC_FLAG_##name)) != 0;	\
+}
+
+FIOPS_IOC_FNS(on_rr);
+FIOPS_IOC_FNS(prio_changed);
+#undef FIOPS_IOC_FNS
+
+#define fiops_log_ioc(fiopsd, ioc, fmt, args...)	\
+	blk_add_trace_msg((fiopsd)->queue, "ioc%d " fmt, (ioc)->pid, ##args)
+#define fiops_log(fiopsd, fmt, args...)	\
+	blk_add_trace_msg((fiopsd)->queue, "fiops " fmt, ##args)
+
+enum wl_prio_t fiops_wl_type(short prio_class)
+{
+	if (prio_class == IOPRIO_CLASS_RT)
+		return RT_WORKLOAD;
+	if (prio_class == IOPRIO_CLASS_BE)
+		return BE_WORKLOAD;
+	return IDLE_WORKLOAD;
+}
+
+static inline struct fiops_ioc *icq_to_cic(struct io_cq *icq)
+{
+	/* cic->icq is the first member, %NULL will convert to %NULL */
+	return container_of(icq, struct fiops_ioc, icq);
+}
+
+static inline struct fiops_ioc *fiops_cic_lookup(struct fiops_data *fiopsd,
+					       struct io_context *ioc)
+{
+	if (ioc)
+		return icq_to_cic(ioc_lookup_icq(ioc, fiopsd->queue));
+	return NULL;
+}
+
+/*
+ * The below is leftmost cache rbtree addon
+ */
+static struct fiops_ioc *fiops_rb_first(struct fiops_rb_root *root)
+{
+	/* Service tree is empty */
+	if (!root->count)
+		return NULL;
+
+	if (!root->left)
+		root->left = rb_first(&root->rb);
+
+	if (root->left)
+		return rb_entry(root->left, struct fiops_ioc, rb_node);
+
+	return NULL;
+}
+
+static void rb_erase_init(struct rb_node *n, struct rb_root *root)
+{
+	rb_erase(n, root);
+	RB_CLEAR_NODE(n);
+}
+
+static void fiops_rb_erase(struct rb_node *n, struct fiops_rb_root *root)
+{
+	if (root->left == n)
+		root->left = NULL;
+	rb_erase_init(n, &root->rb);
+	--root->count;
+}
+
+static inline u64 max_vios(u64 min_vios, u64 vios)
+{
+	s64 delta = (s64)(vios - min_vios);
+	if (delta > 0)
+		min_vios = vios;
+
+	return min_vios;
+}
+
+static void fiops_update_min_vios(struct fiops_rb_root *service_tree)
+{
+	struct fiops_ioc *ioc;
+
+	ioc = fiops_rb_first(service_tree);
+	if (!ioc)
+		return;
+	service_tree->min_vios = max_vios(service_tree->min_vios, ioc->vios);
+}
+
+/*
+ * The fiopsd->service_trees holds all pending fiops_ioc's that have
+ * requests waiting to be processed. It is sorted in the order that
+ * we will service the queues.
+ */
+static void fiops_service_tree_add(struct fiops_data *fiopsd,
+	struct fiops_ioc *ioc)
+{
+	struct rb_node **p, *parent;
+	struct fiops_ioc *__ioc;
+	struct fiops_rb_root *service_tree = ioc_service_tree(ioc);
+	u64 vios;
+	int left;
+
+	/* New added IOC */
+	if (RB_EMPTY_NODE(&ioc->rb_node)) {
+		if (ioc->in_flight > 0)
+			vios = ioc->vios;
+		else
+			vios = max_vios(service_tree->min_vios, ioc->vios);
+	} else {
+		vios = ioc->vios;
+		/* ioc->service_tree might not equal to service_tree */
+		fiops_rb_erase(&ioc->rb_node, ioc->service_tree);
+		ioc->service_tree = NULL;
+	}
+
+	fiops_log_ioc(fiopsd, ioc, "service tree add, vios %lld", vios);
+
+	left = 1;
+	parent = NULL;
+	ioc->service_tree = service_tree;
+	p = &service_tree->rb.rb_node;
+	while (*p) {
+		struct rb_node **n;
+
+		parent = *p;
+		__ioc = rb_entry(parent, struct fiops_ioc, rb_node);
+
+		/*
+		 * sort by key, that represents service time.
+		 */
+		if (vios <  __ioc->vios)
+			n = &(*p)->rb_left;
+		else {
+			n = &(*p)->rb_right;
+			left = 0;
+		}
+
+		p = n;
+	}
+
+	if (left)
+		service_tree->left = &ioc->rb_node;
+
+	ioc->vios = vios;
+	rb_link_node(&ioc->rb_node, parent, p);
+	rb_insert_color(&ioc->rb_node, &service_tree->rb);
+	service_tree->count++;
+
+	fiops_update_min_vios(service_tree);
+}
+
+/*
+ * Update ioc's position in the service tree.
+ */
+static void fiops_resort_rr_list(struct fiops_data *fiopsd,
+	struct fiops_ioc *ioc)
+{
+	/*
+	 * Resorting requires the ioc to be on the RR list already.
+	 */
+	if (fiops_ioc_on_rr(ioc))
+		fiops_service_tree_add(fiopsd, ioc);
+}
+
+/*
+ * add to busy list of queues for service, trying to be fair in ordering
+ * the pending list according to last request service
+ */
+static void fiops_add_ioc_rr(struct fiops_data *fiopsd, struct fiops_ioc *ioc)
+{
+	BUG_ON(fiops_ioc_on_rr(ioc));
+	fiops_mark_ioc_on_rr(ioc);
+
+	fiopsd->busy_queues++;
+
+	fiops_resort_rr_list(fiopsd, ioc);
+}
+
+/*
+ * Called when the ioc no longer has requests pending, remove it from
+ * the service tree.
+ */
+static void fiops_del_ioc_rr(struct fiops_data *fiopsd, struct fiops_ioc *ioc)
+{
+	BUG_ON(!fiops_ioc_on_rr(ioc));
+	fiops_clear_ioc_on_rr(ioc);
+
+	if (!RB_EMPTY_NODE(&ioc->rb_node)) {
+		fiops_rb_erase(&ioc->rb_node, ioc->service_tree);
+		ioc->service_tree = NULL;
+	}
+
+	BUG_ON(!fiopsd->busy_queues);
+	fiopsd->busy_queues--;
+}
+
+/*
+ * rb tree support functions
+ */
+static void fiops_del_rq_rb(struct request *rq)
+{
+	struct fiops_ioc *ioc = RQ_CIC(rq);
+
+	elv_rb_del(&ioc->sort_list, rq);
+}
+
+static void fiops_add_rq_rb(struct request *rq)
+{
+	struct fiops_ioc *ioc = RQ_CIC(rq);
+	struct fiops_data *fiopsd = ioc->fiopsd;
+
+	elv_rb_add(&ioc->sort_list, rq);
+
+	if (!fiops_ioc_on_rr(ioc))
+		fiops_add_ioc_rr(fiopsd, ioc);
+}
+
+static void fiops_reposition_rq_rb(struct fiops_ioc *ioc, struct request *rq)
+{
+	elv_rb_del(&ioc->sort_list, rq);
+	fiops_add_rq_rb(rq);
+}
+
+static void fiops_remove_request(struct request *rq)
+{
+	list_del_init(&rq->queuelist);
+	fiops_del_rq_rb(rq);
+}
+
+static u64 fiops_scaled_vios(struct fiops_data *fiopsd,
+	struct fiops_ioc *ioc, struct request *rq)
+{
+	int vios = VIOS_SCALE;
+
+	if (rq_data_dir(rq) == WRITE)
+		vios = vios * fiopsd->write_scale / fiopsd->read_scale;
+
+	if (!rq_is_sync(rq))
+		vios = vios * fiopsd->async_scale / fiopsd->sync_scale;
+
+	vios +=  vios * (ioc->ioprio - IOPRIO_NORM) / VIOS_PRIO_SCALE;
+
+	return vios;
+}
+
+/* return vios dispatched */
+static u64 fiops_dispatch_request(struct fiops_data *fiopsd,
+	struct fiops_ioc *ioc)
+{
+	struct request *rq;
+	struct request_queue *q = fiopsd->queue;
+
+	rq = rq_entry_fifo(ioc->fifo.next);
+
+	fiops_remove_request(rq);
+	elv_dispatch_add_tail(q, rq);
+
+	fiopsd->in_flight[rq_is_sync(rq)]++;
+	ioc->in_flight++;
+
+	return fiops_scaled_vios(fiopsd, ioc, rq);
+}
+
+static int fiops_forced_dispatch(struct fiops_data *fiopsd)
+{
+	struct fiops_ioc *ioc;
+	int dispatched = 0;
+	int i;
+
+	for (i = RT_WORKLOAD; i >= IDLE_WORKLOAD; i--) {
+		while (!RB_EMPTY_ROOT(&fiopsd->service_tree[i].rb)) {
+			ioc = fiops_rb_first(&fiopsd->service_tree[i]);
+
+			while (!list_empty(&ioc->fifo)) {
+				fiops_dispatch_request(fiopsd, ioc);
+				dispatched++;
+			}
+			if (fiops_ioc_on_rr(ioc))
+				fiops_del_ioc_rr(fiopsd, ioc);
+		}
+	}
+	return dispatched;
+}
+
+static struct fiops_ioc *fiops_select_ioc(struct fiops_data *fiopsd)
+{
+	struct fiops_ioc *ioc;
+	struct fiops_rb_root *service_tree = NULL;
+	int i;
+	struct request *rq;
+
+	for (i = RT_WORKLOAD; i >= IDLE_WORKLOAD; i--) {
+		if (!RB_EMPTY_ROOT(&fiopsd->service_tree[i].rb)) {
+			service_tree = &fiopsd->service_tree[i];
+			break;
+		}
+	}
+
+	if (!service_tree)
+		return NULL;
+
+	ioc = fiops_rb_first(service_tree);
+
+	rq = rq_entry_fifo(ioc->fifo.next);
+	/*
+	 * we are the only async task and sync requests are in flight, delay a
+	 * moment. If there are other tasks coming, sync tasks have no chance
+	 * to be starved, don't delay
+	 */
+	if (!rq_is_sync(rq) && fiopsd->in_flight[1] != 0 &&
+			service_tree->count == 1) {
+		fiops_log_ioc(fiopsd, ioc,
+				"postpone async, in_flight async %d sync %d",
+				fiopsd->in_flight[0], fiopsd->in_flight[1]);
+		return NULL;
+	}
+
+	return ioc;
+}
+
+static void fiops_charge_vios(struct fiops_data *fiopsd,
+	struct fiops_ioc *ioc, u64 vios)
+{
+	struct fiops_rb_root *service_tree = ioc->service_tree;
+	ioc->vios += vios;
+
+	fiops_log_ioc(fiopsd, ioc, "charge vios %lld, new vios %lld", vios, ioc->vios);
+
+	if (RB_EMPTY_ROOT(&ioc->sort_list))
+		fiops_del_ioc_rr(fiopsd, ioc);
+	else
+		fiops_resort_rr_list(fiopsd, ioc);
+
+	fiops_update_min_vios(service_tree);
+}
+
+static int fiops_dispatch_requests(struct request_queue *q, int force)
+{
+	struct fiops_data *fiopsd = q->elevator->elevator_data;
+	struct fiops_ioc *ioc;
+	u64 vios;
+
+	if (unlikely(force))
+		return fiops_forced_dispatch(fiopsd);
+
+	ioc = fiops_select_ioc(fiopsd);
+	if (!ioc)
+		return 0;
+
+	vios = fiops_dispatch_request(fiopsd, ioc);
+
+	fiops_charge_vios(fiopsd, ioc, vios);
+	return 1;
+}
+
+static void fiops_init_prio_data(struct fiops_ioc *cic)
+{
+	struct task_struct *tsk = current;
+	struct io_context *ioc = cic->icq.ioc;
+	int ioprio_class;
+
+	if (!fiops_ioc_prio_changed(cic))
+		return;
+
+	ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
+	switch (ioprio_class) {
+	default:
+		printk(KERN_ERR "fiops: bad prio %x\n", ioprio_class);
+	case IOPRIO_CLASS_NONE:
+		/*
+		 * no prio set, inherit CPU scheduling settings
+		 */
+		cic->ioprio = task_nice_ioprio(tsk);
+		cic->wl_type = fiops_wl_type(task_nice_ioclass(tsk));
+		break;
+	case IOPRIO_CLASS_RT:
+		cic->ioprio = task_ioprio(ioc);
+		cic->wl_type = fiops_wl_type(IOPRIO_CLASS_RT);
+		break;
+	case IOPRIO_CLASS_BE:
+		cic->ioprio = task_ioprio(ioc);
+		cic->wl_type = fiops_wl_type(IOPRIO_CLASS_BE);
+		break;
+	case IOPRIO_CLASS_IDLE:
+		cic->wl_type = fiops_wl_type(IOPRIO_CLASS_IDLE);
+		cic->ioprio = 7;
+		break;
+	}
+
+	fiops_clear_ioc_prio_changed(cic);
+}
+
+static void fiops_insert_request(struct request_queue *q, struct request *rq)
+{
+	struct fiops_ioc *ioc = RQ_CIC(rq);
+
+	fiops_init_prio_data(ioc);
+
+	list_add_tail(&rq->queuelist, &ioc->fifo);
+
+	fiops_add_rq_rb(rq);
+}
+
+/*
+ * scheduler run of queue, if there are requests pending and no one in the
+ * driver that will restart queueing
+ */
+static inline void fiops_schedule_dispatch(struct fiops_data *fiopsd)
+{
+	if (fiopsd->busy_queues)
+		kblockd_schedule_work(fiopsd->queue, &fiopsd->unplug_work);
+}
+
+static void fiops_completed_request(struct request_queue *q, struct request *rq)
+{
+	struct fiops_data *fiopsd = q->elevator->elevator_data;
+	struct fiops_ioc *ioc = RQ_CIC(rq);
+
+	fiopsd->in_flight[rq_is_sync(rq)]--;
+	ioc->in_flight--;
+
+	fiops_log_ioc(fiopsd, ioc, "in_flight %d, busy queues %d",
+		ioc->in_flight, fiopsd->busy_queues);
+
+	if (fiopsd->in_flight[0] + fiopsd->in_flight[1] == 0)
+		fiops_schedule_dispatch(fiopsd);
+}
+
+static struct request *
+fiops_find_rq_fmerge(struct fiops_data *fiopsd, struct bio *bio)
+{
+	struct task_struct *tsk = current;
+	struct fiops_ioc *cic;
+
+	cic = fiops_cic_lookup(fiopsd, tsk->io_context);
+
+	if (cic) {
+		sector_t sector = bio->bi_sector + bio_sectors(bio);
+
+		return elv_rb_find(&cic->sort_list, sector);
+	}
+
+	return NULL;
+}
+
+static int fiops_merge(struct request_queue *q, struct request **req,
+		     struct bio *bio)
+{
+	struct fiops_data *fiopsd = q->elevator->elevator_data;
+	struct request *__rq;
+
+	__rq = fiops_find_rq_fmerge(fiopsd, bio);
+	if (__rq && elv_rq_merge_ok(__rq, bio)) {
+		*req = __rq;
+		return ELEVATOR_FRONT_MERGE;
+	}
+
+	return ELEVATOR_NO_MERGE;
+}
+
+static void fiops_merged_request(struct request_queue *q, struct request *req,
+			       int type)
+{
+	if (type == ELEVATOR_FRONT_MERGE) {
+		struct fiops_ioc *ioc = RQ_CIC(req);
+
+		fiops_reposition_rq_rb(ioc, req);
+	}
+}
+
+static void
+fiops_merged_requests(struct request_queue *q, struct request *rq,
+		    struct request *next)
+{
+	struct fiops_ioc *ioc = RQ_CIC(rq);
+	struct fiops_data *fiopsd = q->elevator->elevator_data;
+
+	fiops_remove_request(next);
+
+	ioc = RQ_CIC(next);
+	/*
+	 * all requests of this task are merged to other tasks, delete it
+	 * from the service tree.
+	 */
+	if (fiops_ioc_on_rr(ioc) && RB_EMPTY_ROOT(&ioc->sort_list))
+		fiops_del_ioc_rr(fiopsd, ioc);
+}
+
+static int fiops_allow_merge(struct request_queue *q, struct request *rq,
+			   struct bio *bio)
+{
+	struct fiops_data *fiopsd = q->elevator->elevator_data;
+	struct fiops_ioc *cic;
+
+	/*
+	 * Lookup the ioc that this bio will be queued with. Allow
+	 * merge only if rq is queued there.
+	 */
+	cic = fiops_cic_lookup(fiopsd, current->io_context);
+
+	return cic == RQ_CIC(rq);
+}
+
+static void fiops_exit_queue(struct elevator_queue *e)
+{
+	struct fiops_data *fiopsd = e->elevator_data;
+
+	cancel_work_sync(&fiopsd->unplug_work);
+
+	kfree(fiopsd);
+}
+
+static void fiops_kick_queue(struct work_struct *work)
+{
+	struct fiops_data *fiopsd =
+		container_of(work, struct fiops_data, unplug_work);
+	struct request_queue *q = fiopsd->queue;
+
+	spin_lock_irq(q->queue_lock);
+	__blk_run_queue(q);
+	spin_unlock_irq(q->queue_lock);
+}
+
+static void *fiops_init_queue(struct request_queue *q)
+{
+	struct fiops_data *fiopsd;
+	int i;
+
+	fiopsd = kzalloc_node(sizeof(*fiopsd), GFP_KERNEL, q->node);
+	if (!fiopsd)
+		return NULL;
+
+	fiopsd->queue = q;
+
+	for (i = IDLE_WORKLOAD; i <= RT_WORKLOAD; i++)
+		fiopsd->service_tree[i] = FIOPS_RB_ROOT;
+
+	INIT_WORK(&fiopsd->unplug_work, fiops_kick_queue);
+
+	fiopsd->read_scale = VIOS_READ_SCALE;
+	fiopsd->write_scale = VIOS_WRITE_SCALE;
+	fiopsd->sync_scale = VIOS_SYNC_SCALE;
+	fiopsd->async_scale = VIOS_ASYNC_SCALE;
+
+	return fiopsd;
+}
+
+static void fiops_init_icq(struct io_cq *icq)
+{
+	struct fiops_data *fiopsd = icq->q->elevator->elevator_data;
+	struct fiops_ioc *ioc = icq_to_cic(icq);
+
+	RB_CLEAR_NODE(&ioc->rb_node);
+	INIT_LIST_HEAD(&ioc->fifo);
+	ioc->sort_list = RB_ROOT;
+
+	ioc->fiopsd = fiopsd;
+
+	ioc->pid = current->pid;
+	fiops_mark_ioc_prio_changed(ioc);
+}
+
+/*
+ * sysfs parts below -->
+ */
+static ssize_t
+fiops_var_show(unsigned int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+fiops_var_store(unsigned int *var, const char *page, size_t count)
+{
+	char *p = (char *) page;
+
+	*var = simple_strtoul(p, &p, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR)					\
+static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
+{									\
+	struct fiops_data *fiopsd = e->elevator_data;			\
+	return fiops_var_show(__VAR, (page));				\
+}
+SHOW_FUNCTION(fiops_read_scale_show, fiopsd->read_scale);
+SHOW_FUNCTION(fiops_write_scale_show, fiopsd->write_scale);
+SHOW_FUNCTION(fiops_sync_scale_show, fiopsd->sync_scale);
+SHOW_FUNCTION(fiops_async_scale_show, fiopsd->async_scale);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX)				\
+static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)	\
+{									\
+	struct fiops_data *fiopsd = e->elevator_data;			\
+	unsigned int __data;						\
+	int ret = fiops_var_store(&__data, (page), count);		\
+	if (__data < (MIN))						\
+		__data = (MIN);						\
+	else if (__data > (MAX))					\
+		__data = (MAX);						\
+	*(__PTR) = __data;						\
+	return ret;							\
+}
+STORE_FUNCTION(fiops_read_scale_store, &fiopsd->read_scale, 1, 100);
+STORE_FUNCTION(fiops_write_scale_store, &fiopsd->write_scale, 1, 100);
+STORE_FUNCTION(fiops_sync_scale_store, &fiopsd->sync_scale, 1, 100);
+STORE_FUNCTION(fiops_async_scale_store, &fiopsd->async_scale, 1, 100);
+#undef STORE_FUNCTION
+
+#define FIOPS_ATTR(name) \
+	__ATTR(name, S_IRUGO|S_IWUSR, fiops_##name##_show, fiops_##name##_store)
+
+static struct elv_fs_entry fiops_attrs[] = {
+	FIOPS_ATTR(read_scale),
+	FIOPS_ATTR(write_scale),
+	FIOPS_ATTR(sync_scale),
+	FIOPS_ATTR(async_scale),
+	__ATTR_NULL
+};
+
+static struct elevator_type iosched_fiops = {
+	.ops = {
+		.elevator_merge_fn =		fiops_merge,
+		.elevator_merged_fn =		fiops_merged_request,
+		.elevator_merge_req_fn =	fiops_merged_requests,
+		.elevator_allow_merge_fn =	fiops_allow_merge,
+		.elevator_dispatch_fn =		fiops_dispatch_requests,
+		.elevator_add_req_fn =		fiops_insert_request,
+		.elevator_completed_req_fn =	fiops_completed_request,
+		.elevator_former_req_fn =	elv_rb_former_request,
+		.elevator_latter_req_fn =	elv_rb_latter_request,
+		.elevator_init_icq_fn =		fiops_init_icq,
+		.elevator_init_fn =		fiops_init_queue,
+		.elevator_exit_fn =		fiops_exit_queue,
+	},
+	.icq_size	=	sizeof(struct fiops_ioc),
+	.icq_align	=	__alignof__(struct fiops_ioc),
+	.elevator_attrs =	fiops_attrs,
+	.elevator_name =	"fiops",
+	.elevator_owner =	THIS_MODULE,
+};
+
+static int __init fiops_init(void)
+{
+	return elv_register(&iosched_fiops);
+}
+
+static void __exit fiops_exit(void)
+{
+	elv_unregister(&iosched_fiops);
+}
+
+module_init(fiops_init);
+module_exit(fiops_exit);
+
+MODULE_AUTHOR("Jens Axboe, Shaohua Li <shli@kernel.org>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("IOPS based IO scheduler");
diff --git a/block/sio-iosched.c b/block/sio-iosched.c
new file mode 100644
index 0000000..3661a9a
--- /dev/null
+++ b/block/sio-iosched.c
@@ -0,0 +1,403 @@
+/*
+ * Simple IO scheduler
+ * Based on Noop, Deadline and V(R) IO schedulers.
+ *
+ * Copyright (C) 2012 Miguel Boton <mboton@gmail.com>
+ *
+ *
+ * This algorithm does not do any kind of sorting, as it is aimed for
+ * aleatory access devices, but it does some basic merging. We try to
+ * keep minimum overhead to achieve low latency.
+ *
+ * Asynchronous and synchronous requests are not treated separately, but
+ * we relay on deadlines to ensure fairness.
+ *
+ */
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/version.h>
+
+enum { ASYNC, SYNC };
+
+/* Tunables */
+static const int sync_read_expire  = HZ / 2;	/* max time before a sync read is submitted. */
+static const int sync_write_expire = 2 * HZ;	/* max time before a sync write is submitted. */
+
+static const int async_read_expire  =  4 * HZ;	/* ditto for async, these limits are SOFT! */
+static const int async_write_expire = 16 * HZ;	/* ditto for async, these limits are SOFT! */
+
+static const int writes_starved = 2;		/* max times reads can starve a write */
+static const int fifo_batch     = 8;		/* # of sequential requests treated as one
+						   by the above parameters. For throughput. */
+
+/* Elevator data */
+struct sio_data {
+	/* Request queues */
+	struct list_head fifo_list[2][2];
+
+	/* Attributes */
+	unsigned int batched;
+	unsigned int starved;
+
+	/* Settings */
+	int fifo_expire[2][2];
+	int fifo_batch;
+	int writes_starved;
+};
+
+static void
+sio_merged_requests(struct request_queue *q, struct request *rq,
+		    struct request *next)
+{
+	/*
+	 * If next expires before rq, assign its expire time to rq
+	 * and move into next position (next will be deleted) in fifo.
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) {
+		if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
+			list_move(&rq->queuelist, &next->queuelist);
+			rq_set_fifo_time(rq, rq_fifo_time(next));
+		}
+	}
+
+	/* Delete next request */
+	rq_fifo_clear(next);
+}
+
+static void
+sio_add_request(struct request_queue *q, struct request *rq)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	/*
+	 * Add request to the proper fifo list and set its
+	 * expire time.
+	 */
+	rq_set_fifo_time(rq, jiffies + sd->fifo_expire[sync][data_dir]);
+	list_add_tail(&rq->queuelist, &sd->fifo_list[sync][data_dir]);
+}
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
+static int
+sio_queue_empty(struct request_queue *q)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+
+	/* Check if fifo lists are empty */
+	return list_empty(&sd->fifo_list[SYNC][READ]) && list_empty(&sd->fifo_list[SYNC][WRITE]) &&
+	       list_empty(&sd->fifo_list[ASYNC][READ]) && list_empty(&sd->fifo_list[ASYNC][WRITE]);
+}
+#endif
+
+static struct request *
+sio_expired_request(struct sio_data *sd, int sync, int data_dir)
+{
+	struct list_head *list = &sd->fifo_list[sync][data_dir];
+	struct request *rq;
+
+	if (list_empty(list))
+		return NULL;
+
+	/* Retrieve request */
+	rq = rq_entry_fifo(list->next);
+
+	/* Request has expired */
+	if (time_after(jiffies, rq_fifo_time(rq)))
+		return rq;
+
+	return NULL;
+}
+
+static struct request *
+sio_choose_expired_request(struct sio_data *sd)
+{
+	struct request *rq;
+
+	/*
+	 * Check expired requests.
+	 * Asynchronous requests have priority over synchronous.
+	 * Write requests have priority over read.
+	 */
+	rq = sio_expired_request(sd, ASYNC, WRITE);
+	if (rq)
+		return rq;
+	rq = sio_expired_request(sd, ASYNC, READ);
+	if (rq)
+		return rq;
+
+	rq = sio_expired_request(sd, SYNC, WRITE);
+	if (rq)
+		return rq;
+	rq = sio_expired_request(sd, SYNC, READ);
+	if (rq)
+		return rq;
+
+	return NULL;
+}
+
+static struct request *
+sio_choose_request(struct sio_data *sd, int data_dir)
+{
+	struct list_head *sync = sd->fifo_list[SYNC];
+	struct list_head *async = sd->fifo_list[ASYNC];
+
+	/*
+	 * Retrieve request from available fifo list.
+	 * Synchronous requests have priority over asynchronous.
+	 * Read requests have priority over write.
+	 */
+	if (!list_empty(&sync[data_dir]))
+		return rq_entry_fifo(sync[data_dir].next);
+	if (!list_empty(&async[data_dir]))
+		return rq_entry_fifo(async[data_dir].next);
+
+	if (!list_empty(&sync[!data_dir]))
+		return rq_entry_fifo(sync[!data_dir].next);
+	if (!list_empty(&async[!data_dir]))
+		return rq_entry_fifo(async[!data_dir].next);
+
+	return NULL;
+}
+
+static inline void
+sio_dispatch_request(struct sio_data *sd, struct request *rq)
+{
+	/*
+	 * Remove the request from the fifo list
+	 * and dispatch it.
+	 */
+	rq_fifo_clear(rq);
+	elv_dispatch_add_tail(rq->q, rq);
+
+	sd->batched++;
+
+	if (rq_data_dir(rq))
+		sd->starved = 0;
+	else
+		sd->starved++;
+}
+
+static int
+sio_dispatch_requests(struct request_queue *q, int force)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	struct request *rq = NULL;
+	int data_dir = READ;
+
+	/*
+	 * Retrieve any expired request after a batch of
+	 * sequential requests.
+	 */
+	if (sd->batched > sd->fifo_batch) {
+		sd->batched = 0;
+		rq = sio_choose_expired_request(sd);
+	}
+
+	/* Retrieve request */
+	if (!rq) {
+		if (sd->starved > sd->writes_starved)
+			data_dir = WRITE;
+
+		rq = sio_choose_request(sd, data_dir);
+		if (!rq)
+			return 0;
+	}
+
+	/* Dispatch request */
+	sio_dispatch_request(sd, rq);
+
+	return 1;
+}
+
+static struct request *
+sio_former_request(struct request_queue *q, struct request *rq)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	if (rq->queuelist.prev == &sd->fifo_list[sync][data_dir])
+		return NULL;
+
+	/* Return former request */
+	return list_entry(rq->queuelist.prev, struct request, queuelist);
+}
+
+static struct request *
+sio_latter_request(struct request_queue *q, struct request *rq)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	if (rq->queuelist.next == &sd->fifo_list[sync][data_dir])
+		return NULL;
+
+	/* Return latter request */
+	return list_entry(rq->queuelist.next, struct request, queuelist);
+}
+
+static void *
+sio_init_queue(struct request_queue *q)
+{
+	struct sio_data *sd;
+
+	/* Allocate structure */
+	sd = kmalloc_node(sizeof(*sd), GFP_KERNEL, q->node);
+	if (!sd)
+		return NULL;
+
+	/* Initialize fifo lists */
+	INIT_LIST_HEAD(&sd->fifo_list[SYNC][READ]);
+	INIT_LIST_HEAD(&sd->fifo_list[SYNC][WRITE]);
+	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][READ]);
+	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][WRITE]);
+
+	/* Initialize data */
+	sd->batched = 0;
+	sd->fifo_expire[SYNC][READ] = sync_read_expire;
+	sd->fifo_expire[SYNC][WRITE] = sync_write_expire;
+	sd->fifo_expire[ASYNC][READ] = async_read_expire;
+	sd->fifo_expire[ASYNC][WRITE] = async_write_expire;
+	sd->fifo_batch = fifo_batch;
+
+	return sd;
+}
+
+static void
+sio_exit_queue(struct elevator_queue *e)
+{
+	struct sio_data *sd = e->elevator_data;
+
+	BUG_ON(!list_empty(&sd->fifo_list[SYNC][READ]));
+	BUG_ON(!list_empty(&sd->fifo_list[SYNC][WRITE]));
+	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][READ]));
+	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][WRITE]));
+
+	/* Free structure */
+	kfree(sd);
+}
+
+/*
+ * sysfs code
+ */
+
+static ssize_t
+sio_var_show(int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+sio_var_store(int *var, const char *page, size_t count)
+{
+	char *p = (char *) page;
+
+	*var = simple_strtol(p, &p, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
+static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
+{									\
+	struct sio_data *sd = e->elevator_data;			\
+	int __data = __VAR;						\
+	if (__CONV)							\
+		__data = jiffies_to_msecs(__data);			\
+	return sio_var_show(__data, (page));			\
+}
+SHOW_FUNCTION(sio_sync_read_expire_show, sd->fifo_expire[SYNC][READ], 1);
+SHOW_FUNCTION(sio_sync_write_expire_show, sd->fifo_expire[SYNC][WRITE], 1);
+SHOW_FUNCTION(sio_async_read_expire_show, sd->fifo_expire[ASYNC][READ], 1);
+SHOW_FUNCTION(sio_async_write_expire_show, sd->fifo_expire[ASYNC][WRITE], 1);
+SHOW_FUNCTION(sio_fifo_batch_show, sd->fifo_batch, 0);
+SHOW_FUNCTION(sio_writes_starved_show, sd->writes_starved, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
+static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)	\
+{									\
+	struct sio_data *sd = e->elevator_data;			\
+	int __data;							\
+	int ret = sio_var_store(&__data, (page), count);		\
+	if (__data < (MIN))						\
+		__data = (MIN);						\
+	else if (__data > (MAX))					\
+		__data = (MAX);						\
+	if (__CONV)							\
+		*(__PTR) = msecs_to_jiffies(__data);			\
+	else								\
+		*(__PTR) = __data;					\
+	return ret;							\
+}
+STORE_FUNCTION(sio_sync_read_expire_store, &sd->fifo_expire[SYNC][READ], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_sync_write_expire_store, &sd->fifo_expire[SYNC][WRITE], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_async_read_expire_store, &sd->fifo_expire[ASYNC][READ], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_async_write_expire_store, &sd->fifo_expire[ASYNC][WRITE], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_fifo_batch_store, &sd->fifo_batch, 0, INT_MAX, 0);
+STORE_FUNCTION(sio_writes_starved_store, &sd->writes_starved, 0, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+#define DD_ATTR(name) \
+	__ATTR(name, S_IRUGO|S_IWUSR, sio_##name##_show, \
+				      sio_##name##_store)
+
+static struct elv_fs_entry sio_attrs[] = {
+	DD_ATTR(sync_read_expire),
+	DD_ATTR(sync_write_expire),
+	DD_ATTR(async_read_expire),
+	DD_ATTR(async_write_expire),
+	DD_ATTR(fifo_batch),
+	DD_ATTR(writes_starved),
+	__ATTR_NULL
+};
+
+static struct elevator_type iosched_sio = {
+	.ops = {
+		.elevator_merge_req_fn		= sio_merged_requests,
+		.elevator_dispatch_fn		= sio_dispatch_requests,
+		.elevator_add_req_fn		= sio_add_request,
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
+		.elevator_queue_empty_fn	= sio_queue_empty,
+#endif
+		.elevator_former_req_fn		= sio_former_request,
+		.elevator_latter_req_fn		= sio_latter_request,
+		.elevator_init_fn		= sio_init_queue,
+		.elevator_exit_fn		= sio_exit_queue,
+	},
+
+	.elevator_attrs = sio_attrs,
+	.elevator_name = "sio",
+	.elevator_owner = THIS_MODULE,
+};
+
+static int __init sio_init(void)
+{
+	/* Register elevator */
+	elv_register(&iosched_sio);
+
+	return 0;
+}
+
+static void __exit sio_exit(void)
+{
+	/* Unregister elevator */
+	elv_unregister(&iosched_sio);
+}
+
+#ifdef CONFIG_FAST_RESUME
+beforeresume_initcall(sio_init);
+#else
+module_init(sio_init);
+#endif
+module_exit(sio_exit);
+
+MODULE_AUTHOR("Miguel Boton");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Simple IO scheduler");
+MODULE_VERSION("0.2");
diff --git a/block/sioplus-iosched.c b/block/sioplus-iosched.c
new file mode 100644
index 0000000..6809cb8
--- /dev/null
+++ b/block/sioplus-iosched.c
@@ -0,0 +1,405 @@
+/*
+ * Simple IO scheduler plus
+ * Based on Noop, Deadline and V(R) IO schedulers.
+ *
+ * Copyright (C) 2012 Miguel Boton <mboton@gmail.com>
+ *           (C) 2013, 2014 Boy Petersen <boypetersen@gmail.com>
+ *
+ *
+ * This algorithm does not do any kind of sorting, as it is aimed for
+ * aleatory access devices, but it does some basic merging. We try to
+ * keep minimum overhead to achieve low latency.
+ *
+ * Asynchronous and synchronous requests are not treated separately, but
+ * we relay on deadlines to ensure fairness.
+ *
+ * The plus version incorporates several fixes and logic improvements.
+ *
+ */
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+
+enum { ASYNC, SYNC };
+
+/* Tunables */
+static const int sync_read_expire = (HZ / 4);	/* max time before a sync read is submitted. */
+static const int sync_write_expire = (HZ / 4) * 5;	/* max time before a sync write is submitted. */
+
+static const int async_read_expire = (HZ / 2);	/* ditto for async, these limits are SOFT! */
+static const int async_write_expire = (HZ * 2);	/* ditto for async, these limits are SOFT! */
+
+static const int writes_starved = 1;		/* max times reads can starve a write */
+static const int fifo_batch     = 3;		/* # of sequential requests treated as one
+						   by the above parameters. For throughput. */
+
+/* Elevator data */
+struct sio_data {
+	/* Request queues */
+	struct list_head fifo_list[2][2];
+
+	/* Attributes */
+	unsigned int batched;
+	unsigned int starved;
+
+	/* Settings */
+	int fifo_expire[2][2];
+	int fifo_batch;
+	int writes_starved;
+};
+
+static void
+sio_merged_requests(struct request_queue *q, struct request *rq,
+		    struct request *next)
+{
+	/*
+	 * If next expires before rq, assign its expire time to rq
+	 * and move into next position (next will be deleted) in fifo.
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) {
+		if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
+			list_move(&rq->queuelist, &next->queuelist);
+			rq_set_fifo_time(rq, rq_fifo_time(next));
+		}
+	}
+
+	/* Delete next request */
+	rq_fifo_clear(next);
+}
+
+static void
+sio_add_request(struct request_queue *q, struct request *rq)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	/*
+	 * Add request to the proper fifo list and set its
+	 * expire time.
+	 */
+	rq_set_fifo_time(rq, jiffies + sd->fifo_expire[sync][data_dir]);
+	list_add_tail(&rq->queuelist, &sd->fifo_list[sync][data_dir]);
+}
+
+static int
+sio_queue_empty(struct request_queue *q)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+
+	/* Check if fifo lists are empty */
+	return list_empty(&sd->fifo_list[SYNC][READ]) && list_empty(&sd->fifo_list[SYNC][WRITE]) &&
+	       list_empty(&sd->fifo_list[ASYNC][READ]) && list_empty(&sd->fifo_list[ASYNC][WRITE]);
+}
+
+static struct request *
+sio_expired_request(struct sio_data *sd, int sync, int data_dir)
+{
+	struct list_head *list = &sd->fifo_list[sync][data_dir];
+	struct request *rq;
+
+	if (list_empty(list))
+		return NULL;
+
+	/* Retrieve request */
+	rq = rq_entry_fifo(list->next);
+
+	/* Request has expired */
+	if (time_after_eq(jiffies, rq_fifo_time(rq)))
+		return rq;
+
+	return NULL;
+}
+
+static struct request *
+sio_choose_expired_request(struct sio_data *sd)
+{
+	struct request *rq;
+
+	/* Reset (non-expired-)batch-counter */
+	sd->batched = 0;
+
+	/*
+	 * Check expired requests.
+	 * Asynchronous requests have priority over synchronous.
+	 * Write requests have priority over read.
+	 */
+	rq = sio_expired_request(sd, ASYNC, WRITE);
+	if (rq)
+		return rq;
+	rq = sio_expired_request(sd, ASYNC, READ);
+	if (rq)
+		return rq;
+
+	rq = sio_expired_request(sd, SYNC, WRITE);
+	if (rq)
+		return rq;
+	rq = sio_expired_request(sd, SYNC, READ);
+	if (rq)
+		return rq;
+
+
+	return NULL;
+}
+
+static struct request *
+sio_choose_request(struct sio_data *sd, int data_dir)
+{
+	struct list_head *sync = sd->fifo_list[SYNC];
+	struct list_head *async = sd->fifo_list[ASYNC];
+
+	/* Increase (non-expired-)batch-counter */
+	sd->batched++;
+
+	/*
+	 * Retrieve request from available fifo list.
+	 * Synchronous requests have priority over asynchronous.
+	 * Read requests have priority over write.
+	 */
+	if (!list_empty(&sync[data_dir]))
+		return rq_entry_fifo(sync[data_dir].next);
+	if (!list_empty(&async[data_dir]))
+		return rq_entry_fifo(async[data_dir].next);
+
+	if (!list_empty(&sync[!data_dir]))
+		return rq_entry_fifo(sync[!data_dir].next);
+	if (!list_empty(&async[!data_dir]))
+		return rq_entry_fifo(async[!data_dir].next);
+
+	return NULL;
+}
+
+static inline void
+sio_dispatch_request(struct sio_data *sd, struct request *rq)
+{
+
+	/*
+	 * Remove the request from the fifo list
+	 * and dispatch it.
+	 */
+	rq_fifo_clear(rq);
+	elv_dispatch_add_tail(rq->q, rq);
+
+	if (rq_data_dir(rq)) {
+		sd->starved = 0;
+	} else {
+		if (!list_empty(&sd->fifo_list[SYNC][WRITE]) || 
+				!list_empty(&sd->fifo_list[ASYNC][WRITE]))
+			sd->starved++;
+	}
+}
+
+static int
+sio_dispatch_requests(struct request_queue *q, int force)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	struct request *rq = NULL;
+	int data_dir = READ;
+
+	/*
+	 * Retrieve any expired request after a batch of
+	 * sequential requests.
+	 */
+	if (sd->batched >= sd->fifo_batch)
+		rq = sio_choose_expired_request(sd);
+
+	/* Retrieve request */
+	if (!rq) {
+		if (sd->starved >= sd->writes_starved)
+			data_dir = WRITE;
+
+		rq = sio_choose_request(sd, data_dir);
+		if (!rq)
+			return 0;
+	}
+
+	/* Dispatch request */
+	sio_dispatch_request(sd, rq);
+
+	return 1;
+}
+
+static struct request *
+sio_former_request(struct request_queue *q, struct request *rq)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	if (rq->queuelist.prev == &sd->fifo_list[sync][data_dir])
+		return NULL;
+
+	/* Return former request */
+	return list_entry(rq->queuelist.prev, struct request, queuelist);
+}
+
+static struct request *
+sio_latter_request(struct request_queue *q, struct request *rq)
+{
+	struct sio_data *sd = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	if (rq->queuelist.next == &sd->fifo_list[sync][data_dir])
+		return NULL;
+
+	/* Return latter request */
+	return list_entry(rq->queuelist.next, struct request, queuelist);
+}
+
+static void *
+sio_init_queue(struct request_queue *q)
+{
+	struct sio_data *sd;
+
+	/* Allocate structure */
+	sd = kmalloc_node(sizeof(*sd), GFP_KERNEL, q->node);
+	if (!sd)
+		return NULL;
+
+	/* Initialize fifo lists */
+	INIT_LIST_HEAD(&sd->fifo_list[SYNC][READ]);
+	INIT_LIST_HEAD(&sd->fifo_list[SYNC][WRITE]);
+	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][READ]);
+	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][WRITE]);
+
+	/* Initialize data */
+	sd->batched = 0;
+	sd->fifo_expire[SYNC][READ] = sync_read_expire;
+	sd->fifo_expire[SYNC][WRITE] = sync_write_expire;
+	sd->fifo_expire[ASYNC][READ] = async_read_expire;
+	sd->fifo_expire[ASYNC][WRITE] = async_write_expire;
+	sd->fifo_batch = fifo_batch;
+	sd->writes_starved = writes_starved;
+
+	return sd;
+}
+
+static void
+sio_exit_queue(struct elevator_queue *e)
+{
+	struct sio_data *sd = e->elevator_data;
+
+	BUG_ON(!list_empty(&sd->fifo_list[SYNC][READ]));
+	BUG_ON(!list_empty(&sd->fifo_list[SYNC][WRITE]));
+	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][READ]));
+	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][WRITE]));
+
+	/* Free structure */
+	kfree(sd);
+}
+
+/*
+ * sysfs code
+ */
+
+static ssize_t
+sio_var_show(int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+sio_var_store(int *var, const char *page, size_t count)
+{
+	char *p = (char *) page;
+
+	*var = simple_strtol(p, &p, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
+static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
+{									\
+	struct sio_data *sd = e->elevator_data;			\
+	int __data = __VAR;						\
+	if (__CONV)							\
+		__data = jiffies_to_msecs(__data);			\
+	return sio_var_show(__data, (page));			\
+}
+SHOW_FUNCTION(sio_sync_read_expire_show, sd->fifo_expire[SYNC][READ], 1);
+SHOW_FUNCTION(sio_sync_write_expire_show, sd->fifo_expire[SYNC][WRITE], 1);
+SHOW_FUNCTION(sio_async_read_expire_show, sd->fifo_expire[ASYNC][READ], 1);
+SHOW_FUNCTION(sio_async_write_expire_show, sd->fifo_expire[ASYNC][WRITE], 1);
+SHOW_FUNCTION(sio_fifo_batch_show, sd->fifo_batch, 0);
+SHOW_FUNCTION(sio_writes_starved_show, sd->writes_starved, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
+static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)	\
+{									\
+	struct sio_data *sd = e->elevator_data;			\
+	int __data;							\
+	int ret = sio_var_store(&__data, (page), count);		\
+	if (__data < (MIN))						\
+		__data = (MIN);						\
+	else if (__data > (MAX))					\
+		__data = (MAX);						\
+	if (__CONV)							\
+		*(__PTR) = msecs_to_jiffies(__data);			\
+	else								\
+		*(__PTR) = __data;					\
+	return ret;							\
+}
+STORE_FUNCTION(sio_sync_read_expire_store, &sd->fifo_expire[SYNC][READ], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_sync_write_expire_store, &sd->fifo_expire[SYNC][WRITE], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_async_read_expire_store, &sd->fifo_expire[ASYNC][READ], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_async_write_expire_store, &sd->fifo_expire[ASYNC][WRITE], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_fifo_batch_store, &sd->fifo_batch, 1, INT_MAX, 0);
+STORE_FUNCTION(sio_writes_starved_store, &sd->writes_starved, 1, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+#define DD_ATTR(name) \
+	__ATTR(name, S_IRUGO|S_IWUSR, sio_##name##_show, \
+				      sio_##name##_store)
+
+static struct elv_fs_entry sio_attrs[] = {
+	DD_ATTR(sync_read_expire),
+	DD_ATTR(sync_write_expire),
+	DD_ATTR(async_read_expire),
+	DD_ATTR(async_write_expire),
+	DD_ATTR(fifo_batch),
+	DD_ATTR(writes_starved),
+	__ATTR_NULL
+};
+
+static struct elevator_type iosched_sioplus = {
+	.ops = {
+		.elevator_merge_req_fn		= sio_merged_requests,
+		.elevator_dispatch_fn		= sio_dispatch_requests,
+		.elevator_add_req_fn		= sio_add_request,
+		.elevator_queue_empty_fn	= sio_queue_empty,
+		.elevator_former_req_fn		= sio_former_request,
+		.elevator_latter_req_fn		= sio_latter_request,
+		.elevator_init_fn		= sio_init_queue,
+		.elevator_exit_fn		= sio_exit_queue,
+	},
+
+	.elevator_attrs = sio_attrs,
+	.elevator_name = "sioplus",
+	.elevator_owner = THIS_MODULE,
+};
+
+static int __init sioplus_init(void)
+{
+	/* Register elevator */
+	elv_register(&iosched_sioplus);
+
+	return 0;
+}
+
+static void __exit sioplus_exit(void)
+{
+	/* Unregister elevator */
+	elv_unregister(&iosched_sioplus);
+}
+
+module_init(sioplus_init);
+module_exit(sioplus_exit);
+
+MODULE_AUTHOR("Miguel Boton");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Simple IO scheduler plus");
diff --git a/block/tripndroid-iosched.c b/block/tripndroid-iosched.c
new file mode 100644
index 0000000..a4d0080
--- /dev/null
+++ b/block/tripndroid-iosched.c
@@ -0,0 +1,261 @@
+/*
+ * Copyright (c) 2013, TripNDroid Mobile Engineering
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+enum { ASYNC, SYNC };
+
+static const int sync_read_expire  = 1 * HZ;	/* max time before a sync read is submitted. */
+static const int sync_write_expire = 1 * HZ;	/* max time before a sync write is submitted. */
+static const int async_read_expire  =  2 * HZ;	/* ditto for async, these limits are SOFT! */
+static const int async_write_expire = 2 * HZ;	/* ditto for async, these limits are SOFT! */
+
+static const int writes_starved = 1;		/* max times reads can starve a write */
+static const int fifo_batch     = 1;		/* # of sequential requests treated as one
+						   by the above parameters. For throughput. */
+
+struct tripndroid_data {
+
+	struct list_head fifo_list[2][2];
+
+	unsigned int batched;
+	unsigned int starved;
+
+	int fifo_expire[2][2];
+	int fifo_batch;
+	int writes_starved;
+};
+
+static void tripndroid_merged_requests(struct request_queue *q, struct request *rq,
+		    struct request *next)
+{
+	/*
+	 * If next expires before rq, assign its expire time to rq
+	 * and move into next position (next will be deleted) in fifo.
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) {
+		if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
+			list_move(&rq->queuelist, &next->queuelist);
+			rq_set_fifo_time(rq, rq_fifo_time(next));
+		}
+	}
+
+	rq_fifo_clear(next);
+}
+
+static void tripndroid_add_request(struct request_queue *q, struct request *rq)
+{
+	struct tripndroid_data *td = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	rq_set_fifo_time(rq, jiffies + td->fifo_expire[sync][data_dir]);
+	list_add(&rq->queuelist, &td->fifo_list[sync][data_dir]);
+}
+
+static struct request *tripndroid_expired_request(struct tripndroid_data *td, int sync, int data_dir)
+{
+	struct list_head *list = &td->fifo_list[sync][data_dir];
+	struct request *rq;
+
+	if (list_empty(list))
+		return NULL;
+
+	rq = rq_entry_fifo(list->next);
+
+	if (time_after_eq(jiffies, rq_fifo_time(rq)))
+		return rq;
+
+	return NULL;
+}
+
+static struct request *tripndroid_choose_expired_request(struct tripndroid_data *td)
+{
+	struct request *rq;
+
+	/* Asynchronous requests have priority over synchronous.
+	 * Write requests have priority over read. */
+
+	rq = tripndroid_expired_request(td, ASYNC, WRITE);
+	if (rq)
+		return rq;
+	rq = tripndroid_expired_request(td, ASYNC, READ);
+	if (rq)
+		return rq;
+
+	rq = tripndroid_expired_request(td, SYNC, WRITE);
+	if (rq)
+		return rq;
+	rq = tripndroid_expired_request(td, SYNC, READ);
+	if (rq)
+		return rq;
+
+	return NULL;
+}
+
+static struct request *tripndroid_choose_request(struct tripndroid_data *td, int data_dir)
+{
+	struct list_head *sync = td->fifo_list[SYNC];
+	struct list_head *async = td->fifo_list[ASYNC];
+
+	if (!list_empty(&sync[data_dir]))
+		return rq_entry_fifo(sync[data_dir].next);
+	if (!list_empty(&sync[!data_dir]))
+		return rq_entry_fifo(sync[!data_dir].next);
+
+	if (!list_empty(&async[data_dir]))
+		return rq_entry_fifo(async[data_dir].next);
+	if (!list_empty(&async[!data_dir]))
+		return rq_entry_fifo(async[!data_dir].next);
+
+	return NULL;
+}
+
+static inline void tripndroid_dispatch_request(struct tripndroid_data *td, struct request *rq)
+{
+	/* Dispatch the request */
+	rq_fifo_clear(rq);
+	elv_dispatch_add_tail(rq->q, rq);
+
+	td->batched++;
+
+	if (rq_data_dir(rq))
+		td->starved = 0;
+	else
+		td->starved++;
+}
+
+static int tripndroid_dispatch_requests(struct request_queue *q, int force)
+{
+	struct tripndroid_data *td = q->elevator->elevator_data;
+	struct request *rq = NULL;
+	int data_dir = READ;
+
+	if (td->batched > td->fifo_batch) {
+		td->batched = 0;
+		rq = tripndroid_choose_expired_request(td);
+	}
+
+	if (!rq) {
+		if (td->starved > td->writes_starved)
+			data_dir = WRITE;
+
+		rq = tripndroid_choose_request(td, data_dir);
+		if (!rq)
+			return 0;
+	}
+
+	tripndroid_dispatch_request(td, rq);
+
+	return 1;
+}
+
+static struct request *tripndroid_former_request(struct request_queue *q, struct request *rq)
+{
+	struct tripndroid_data *td = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	if (rq->queuelist.prev == &td->fifo_list[sync][data_dir])
+		return NULL;
+
+	return list_entry(rq->queuelist.prev, struct request, queuelist);
+}
+
+static struct request *tripndroid_latter_request(struct request_queue *q, struct request *rq)
+{
+	struct tripndroid_data *td = q->elevator->elevator_data;
+	const int sync = rq_is_sync(rq);
+	const int data_dir = rq_data_dir(rq);
+
+	if (rq->queuelist.next == &td->fifo_list[sync][data_dir])
+		return NULL;
+
+	return list_entry(rq->queuelist.next, struct request, queuelist);
+}
+
+static void *tripndroid_init_queue(struct request_queue *q)
+{
+	struct tripndroid_data *td;
+
+	td = kmalloc_node(sizeof(*td), GFP_KERNEL, q->node);
+	if (!td)
+		return NULL;
+
+	INIT_LIST_HEAD(&td->fifo_list[SYNC][READ]);
+	INIT_LIST_HEAD(&td->fifo_list[SYNC][WRITE]);
+	INIT_LIST_HEAD(&td->fifo_list[ASYNC][READ]);
+	INIT_LIST_HEAD(&td->fifo_list[ASYNC][WRITE]);
+
+	td->batched = 0;
+	td->fifo_expire[SYNC][READ] = sync_read_expire;
+	td->fifo_expire[SYNC][WRITE] = sync_write_expire;
+	td->fifo_expire[ASYNC][READ] = async_read_expire;
+	td->fifo_expire[ASYNC][WRITE] = async_write_expire;
+	td->fifo_batch = fifo_batch;
+
+	return td;
+}
+
+static void tripndroid_exit_queue(struct elevator_queue *e)
+{
+	struct tripndroid_data *td = e->elevator_data;
+
+	BUG_ON(!list_empty(&td->fifo_list[SYNC][READ]));
+	BUG_ON(!list_empty(&td->fifo_list[SYNC][WRITE]));
+	BUG_ON(!list_empty(&td->fifo_list[ASYNC][READ]));
+	BUG_ON(!list_empty(&td->fifo_list[ASYNC][WRITE]));
+
+	kfree(td);
+}
+
+static struct elevator_type iosched_tripndroid = {
+	.ops = {
+		.elevator_merge_req_fn		= tripndroid_merged_requests,
+		.elevator_dispatch_fn		= tripndroid_dispatch_requests,
+		.elevator_add_req_fn		= tripndroid_add_request,
+		.elevator_former_req_fn		= tripndroid_former_request,
+		.elevator_latter_req_fn		= tripndroid_latter_request,
+		.elevator_init_fn		= tripndroid_init_queue,
+		.elevator_exit_fn		= tripndroid_exit_queue,
+	},
+	.elevator_name = "tripndroid",
+	.elevator_owner = THIS_MODULE,
+};
+
+static int __init tripndroid_init(void)
+{
+	elv_register(&iosched_tripndroid);
+	return 0;
+}
+
+static void __exit tripndroid_exit(void)
+{
+	elv_unregister(&iosched_tripndroid);
+}
+
+module_init(tripndroid_init);
+module_exit(tripndroid_exit);
+
+MODULE_AUTHOR("TripNRaVeR");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TripNDroid IO Scheduler");
diff --git a/block/vr-iosched.c b/block/vr-iosched.c
new file mode 100644
index 0000000..5d8954b
--- /dev/null
+++ b/block/vr-iosched.c
@@ -0,0 +1,432 @@
+/*
+* V(R) I/O Scheduler
+*
+* Copyright (C) 2007 Aaron Carroll <aaronc@gelato.unsw.edu.au>
+*
+*
+* The algorithm:
+*
+* The next request is decided based on its distance from the last
+* request, with a multiplicative penalty of `rev_penalty' applied
+* for reversing the head direction. A rev_penalty of 1 means SSTF
+* behaviour. As this variable is increased, the algorithm approaches
+* pure SCAN. Setting rev_penalty to 0 forces SCAN.
+*
+* Async and synch requests are not treated seperately. Instead we
+* rely on deadlines to ensure fairness.
+*
+*/
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/rbtree.h>
+
+#include <asm/div64.h>
+
+enum vr_data_dir {
+	ASYNC,
+	SYNC,
+};
+
+enum vr_head_dir {
+	FORWARD,
+	BACKWARD,
+};
+
+static const int sync_expire = HZ / 2; /* max time before a sync is submitted. */
+static const int async_expire = 5 * HZ; /* ditto for async, these limits are SOFT! */
+static const int fifo_batch = 1;
+static const int rev_penalty = 10; /* penalty for reversing head direction */
+
+struct vr_data {
+struct rb_root sort_list;
+struct list_head fifo_list[2];
+
+struct request *next_rq;
+struct request *prev_rq;
+
+unsigned int nbatched;
+sector_t last_sector; /* head position */
+int head_dir;
+
+/* tunables */
+int fifo_expire[2];
+int fifo_batch;
+int rev_penalty;
+};
+
+static void vr_move_request(struct vr_data *, struct request *);
+
+static inline struct vr_data *
+vr_get_data(struct request_queue *q)
+{
+	return q->elevator->elevator_data;
+}
+
+static void
+vr_add_rq_rb(struct vr_data *vd, struct request *rq)
+{
+	elv_rb_add(&vd->sort_list, rq);
+
+	if (blk_rq_pos(rq) >= vd->last_sector) {
+		if (!vd->next_rq || blk_rq_pos(vd->next_rq) > blk_rq_pos(rq))
+			vd->next_rq = rq;
+	} else {
+		if (!vd->prev_rq || blk_rq_pos(vd->prev_rq) < blk_rq_pos(rq))
+			vd->prev_rq = rq;
+	}
+
+	BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq);
+	BUG_ON(vd->next_rq && vd->prev_rq && blk_rq_pos(vd->next_rq) < blk_rq_pos(vd->prev_rq));
+}
+
+static void
+vr_del_rq_rb(struct vr_data *vd, struct request *rq)
+{
+	/*
+	* We might be deleting our cached next request.
+	* If so, find its sucessor.
+	*/
+
+	if (vd->next_rq == rq)
+		vd->next_rq = elv_rb_latter_request(NULL, rq);
+	else if (vd->prev_rq == rq)
+		vd->prev_rq = elv_rb_former_request(NULL, rq);
+
+	BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq);
+	BUG_ON(vd->next_rq && vd->prev_rq && blk_rq_pos(vd->next_rq) < blk_rq_pos(vd->prev_rq));
+
+	elv_rb_del(&vd->sort_list, rq);
+}
+
+/*
+ * add rq to rbtree and fifo
+ */
+static void
+vr_add_request(struct request_queue *q, struct request *rq)
+{
+	struct vr_data *vd = vr_get_data(q);
+	const int dir = rq_is_sync(rq);
+
+	vr_add_rq_rb(vd, rq);
+	
+	if (vd->fifo_expire[dir]) {
+		rq_set_fifo_time(rq, jiffies + vd->fifo_expire[dir]);
+		list_add_tail(&rq->queuelist, &vd->fifo_list[dir]);
+	}
+}
+
+/*
+ * remove rq from rbtree and fifo.
+ */
+static void
+vr_remove_request(struct request_queue *q, struct request *rq)
+{
+	struct vr_data *vd = vr_get_data(q);
+
+	rq_fifo_clear(rq);
+	vr_del_rq_rb(vd, rq);
+}
+
+static int
+vr_merge(struct request_queue *q, struct request **rqp, struct bio *bio)
+{
+	sector_t sector = bio->bi_sector + bio_sectors(bio);
+	struct vr_data *vd = vr_get_data(q);
+	struct request *rq = elv_rb_find(&vd->sort_list, sector);
+	
+	if (rq && elv_rq_merge_ok(rq, bio)) {
+		*rqp = rq;
+		return ELEVATOR_FRONT_MERGE;
+	}
+	return ELEVATOR_NO_MERGE;
+}
+
+static void
+vr_merged_request(struct request_queue *q, struct request *req, int type)
+{
+	struct vr_data *vd = vr_get_data(q);
+
+	/*
+	 * if the merge was a front merge, we need to reposition request
+	 */
+	if (type == ELEVATOR_FRONT_MERGE) {
+		vr_del_rq_rb(vd, req);
+		vr_add_rq_rb(vd, req);
+	}
+}
+
+static void
+vr_merged_requests(struct request_queue *q, struct request *rq,
+struct request *next)
+{
+	/*
+	 * if next expires before rq, assign its expire time to rq
+	 * and move into next position (next will be deleted) in fifo
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) {
+		if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
+			list_move(&rq->queuelist, &next->queuelist);
+			rq_set_fifo_time(rq, rq_fifo_time(next));
+		}
+	}
+
+	vr_remove_request(q, next);
+}
+
+/*
+ * move an entry to dispatch queue
+ */
+static void
+vr_move_request(struct vr_data *vd, struct request *rq)
+{
+	struct request_queue *q = rq->q;
+
+	if (blk_rq_pos(rq) > vd->last_sector)
+		vd->head_dir = FORWARD;
+	else
+		vd->head_dir = BACKWARD;
+
+	vd->last_sector = blk_rq_pos(rq);
+	vd->next_rq = elv_rb_latter_request(NULL, rq);
+	vd->prev_rq = elv_rb_former_request(NULL, rq);
+
+	BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq);
+
+	vr_remove_request(q, rq);
+	elv_dispatch_add_tail(q, rq);
+	vd->nbatched++;
+}
+
+/*
+ * get the first expired request in direction ddir
+ */
+static struct request *
+vr_expired_request(struct vr_data *vd, int ddir)
+{
+	struct request *rq;
+
+	if (list_empty(&vd->fifo_list[ddir]))
+		return NULL;
+
+	rq = rq_entry_fifo(vd->fifo_list[ddir].next);
+	if (time_after(jiffies, rq_fifo_time(rq)))
+		return rq;
+
+	return NULL;
+}
+
+/*
+ * Returns the oldest expired request
+ */
+static struct request *
+vr_check_fifo(struct vr_data *vd)
+{
+	struct request *rq_sync = vr_expired_request(vd, SYNC);
+	struct request *rq_async = vr_expired_request(vd, ASYNC);
+
+	if (rq_async && rq_sync) {
+		if (time_after(rq_fifo_time(rq_async), rq_fifo_time(rq_sync)))
+			return rq_sync;
+	}
+	else if (rq_sync)
+		return rq_sync;
+
+	return rq_async;
+}
+
+/*
+* Return the request with the lowest penalty
+*/
+static struct request *
+vr_choose_request(struct vr_data *vd)
+{
+	int penalty = (vd->rev_penalty) ? : INT_MAX;
+	struct request *next = vd->next_rq;
+	struct request *prev = vd->prev_rq;
+	sector_t next_pen, prev_pen;
+	
+	BUG_ON(prev && prev == next);
+
+	if (!prev)
+		return next;
+	else if (!next)
+		return prev;
+
+/* At this point both prev and next are defined and distinct */
+
+	next_pen = blk_rq_pos(next) - vd->last_sector;
+	prev_pen = vd->last_sector - blk_rq_pos(prev);
+
+	if (vd->head_dir == FORWARD)
+		next_pen = do_div(next_pen, penalty);
+	else
+		prev_pen = do_div(prev_pen, penalty);
+
+	if (next_pen <= prev_pen)
+		return next;
+
+	return prev;
+}
+
+static int
+vr_dispatch_requests(struct request_queue *q, int force)
+{
+	struct vr_data *vd = vr_get_data(q);
+	struct request *rq = NULL;
+
+/* Check for and issue expired requests */
+	if (vd->nbatched > vd->fifo_batch) {
+		vd->nbatched = 0;
+		rq = vr_check_fifo(vd);
+	}
+
+	if (!rq) {
+		rq = vr_choose_request(vd);
+		if (!rq)
+			return 0;
+	}
+
+	vr_move_request(vd, rq);
+
+	return 1;
+}
+
+
+static void
+vr_exit_queue(struct elevator_queue *e)
+{
+	struct vr_data *vd = e->elevator_data;
+	BUG_ON(!RB_EMPTY_ROOT(&vd->sort_list));
+	kfree(vd);
+}
+
+/*
+* initialize elevator private data (vr_data).
+*/
+static void *vr_init_queue(struct request_queue *q)
+{
+	struct vr_data *vd;
+	
+	vd = kmalloc_node(sizeof(*vd), GFP_KERNEL | __GFP_ZERO, q->node);
+	if (!vd)
+		return NULL;
+
+	INIT_LIST_HEAD(&vd->fifo_list[SYNC]);
+	INIT_LIST_HEAD(&vd->fifo_list[ASYNC]);
+	vd->sort_list = RB_ROOT;
+	vd->fifo_expire[SYNC] = sync_expire;
+	vd->fifo_expire[ASYNC] = async_expire;
+	vd->fifo_batch = fifo_batch;
+	vd->rev_penalty = rev_penalty;
+	return vd;
+}
+
+/*
+ * sysfs parts below
+ */
+
+static ssize_t
+vr_var_show(int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+vr_var_store(int *var, const char *page, size_t count)
+{
+	*var = simple_strtol(page, NULL, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, char *page) \
+{ \
+struct vr_data *vd = e->elevator_data; \
+int __data = __VAR; \
+if (__CONV) \
+__data = jiffies_to_msecs(__data); \
+return vr_var_show(__data, (page)); \
+}
+SHOW_FUNCTION(vr_sync_expire_show, vd->fifo_expire[SYNC], 1);
+SHOW_FUNCTION(vr_async_expire_show, vd->fifo_expire[ASYNC], 1);
+SHOW_FUNCTION(vr_fifo_batch_show, vd->fifo_batch, 0);
+SHOW_FUNCTION(vr_rev_penalty_show, vd->rev_penalty, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
+{ \
+struct vr_data *vd = e->elevator_data; \
+int __data; \
+int ret = vr_var_store(&__data, (page), count); \
+if (__data < (MIN)) \
+__data = (MIN); \
+else if (__data > (MAX)) \
+__data = (MAX); \
+if (__CONV) \
+*(__PTR) = msecs_to_jiffies(__data); \
+else \
+*(__PTR) = __data; \
+return ret; \
+}
+STORE_FUNCTION(vr_sync_expire_store, &vd->fifo_expire[SYNC], 0, INT_MAX, 1);
+STORE_FUNCTION(vr_async_expire_store, &vd->fifo_expire[ASYNC], 0, INT_MAX, 1);
+STORE_FUNCTION(vr_fifo_batch_store, &vd->fifo_batch, 0, INT_MAX, 0);
+STORE_FUNCTION(vr_rev_penalty_store, &vd->rev_penalty, 0, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+#define DD_ATTR(name) \
+__ATTR(name, S_IRUGO|S_IWUSR, vr_##name##_show, \
+vr_##name##_store)
+
+static struct elv_fs_entry vr_attrs[] = {
+	DD_ATTR(sync_expire),
+	DD_ATTR(async_expire),
+	DD_ATTR(fifo_batch),
+	DD_ATTR(rev_penalty),
+	__ATTR_NULL
+};
+
+static struct elevator_type iosched_vr = {
+	.ops = {
+		.elevator_merge_fn = vr_merge,
+		.elevator_merged_fn = vr_merged_request,
+		.elevator_merge_req_fn = vr_merged_requests,
+		.elevator_dispatch_fn = vr_dispatch_requests,
+		.elevator_add_req_fn = vr_add_request,
+		.elevator_former_req_fn = elv_rb_former_request,
+		.elevator_latter_req_fn = elv_rb_latter_request,
+		.elevator_init_fn = vr_init_queue,
+		.elevator_exit_fn = vr_exit_queue,
+	},
+
+	.elevator_attrs = vr_attrs,
+	.elevator_name = "vr",
+	.elevator_owner = THIS_MODULE,
+};
+	
+static int __init vr_init(void)
+{
+	elv_register(&iosched_vr);
+
+	return 0;
+}
+
+static void __exit vr_exit(void)
+{
+	elv_unregister(&iosched_vr);
+}
+
+module_init(vr_init);
+module_exit(vr_exit);
+
+MODULE_AUTHOR("Aaron Carroll");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("V(R) IO scheduler");
diff --git a/block/zen-iosched.c b/block/zen-iosched.c
new file mode 100644
index 0000000..77145de
--- /dev/null
+++ b/block/zen-iosched.c
@@ -0,0 +1,277 @@
+/*
+ * Zen IO scheduler
+ * Primarily based on Noop, deadline, and SIO IO schedulers.
+ *
+ * Copyright (C) 2012 Brandon Berhent <bbedward@gmail.com>
+ *
+ * FCFS, dispatches are back-inserted, deadlines ensure fairness.
+ * Should work best with devices where there is no travel delay.
+ */
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+
+enum zen_data_dir { ASYNC, SYNC };
+
+static const int sync_expire  = HZ / 4;    /* max time before a sync is submitted. */
+static const int async_expire = 2 * HZ;    /* ditto for async, these limits are SOFT! */
+static const int fifo_batch = 1;
+
+struct zen_data {
+	/* Runtime Data */
+	/* Requests are only present on fifo_list */
+	struct list_head fifo_list[2];
+
+        unsigned int batching;          /* number of sequential requests made */
+
+	/* tunables */
+	int fifo_expire[2];
+	int fifo_batch;
+};
+
+static inline struct zen_data *
+zen_get_data(struct request_queue *q) {
+	return q->elevator->elevator_data;
+}
+
+static void zen_dispatch(struct zen_data *, struct request *);
+
+static void
+zen_merged_requests(struct request_queue *q, struct request *rq,
+                    struct request *next)
+{
+	/*
+	 * if next expires before rq, assign its expire time to arq
+	 * and move into next position (next will be deleted) in fifo
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) {
+		if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
+			list_move(&rq->queuelist, &next->queuelist);
+			rq_set_fifo_time(rq, rq_fifo_time(next));
+		}
+	}
+
+	/* next request is gone */
+	rq_fifo_clear(next);
+}
+
+static void zen_add_request(struct request_queue *q, struct request *rq)
+{
+	struct zen_data *zdata = zen_get_data(q);
+	const int dir = rq_data_dir(rq);
+
+	if (zdata->fifo_expire[dir]) {
+		rq_set_fifo_time(rq, jiffies + zdata->fifo_expire[dir]);
+		list_add_tail(&rq->queuelist, &zdata->fifo_list[dir]);
+	}
+}
+
+static void zen_dispatch(struct zen_data *zdata, struct request *rq)
+{
+	/* Remove request from list and dispatch it */
+	rq_fifo_clear(rq);
+	elv_dispatch_add_tail(rq->q, rq);
+
+	/* Increment # of sequential requests */
+	zdata->batching++;
+}
+
+/*
+ * get the first expired request in direction ddir
+ */
+static struct request *
+zen_expired_request(struct zen_data *zdata, int ddir)
+{
+        struct request *rq;
+
+        if (list_empty(&zdata->fifo_list[ddir]))
+                return NULL;
+
+        rq = rq_entry_fifo(zdata->fifo_list[ddir].next);
+        if (time_after(jiffies, rq_fifo_time(rq)))
+                return rq;
+
+        return NULL;
+}
+
+/*
+ * zen_check_fifo returns 0 if there are no expired requests on the fifo,
+ * otherwise it returns the next expired request
+ */
+static struct request *
+zen_check_fifo(struct zen_data *zdata)
+{
+        struct request *rq_sync = zen_expired_request(zdata, SYNC);
+        struct request *rq_async = zen_expired_request(zdata, ASYNC);
+
+        if (rq_async && rq_sync) {
+        	if (time_after(rq_fifo_time(rq_async), rq_fifo_time(rq_sync)))
+                	return rq_sync;
+        } else if (rq_sync) {
+                return rq_sync;
+	} else if (rq_async) {
+		return rq_async;
+	}
+
+        return 0;
+}
+
+static struct request *
+zen_choose_request(struct zen_data *zdata)
+{
+        /*
+         * Retrieve request from available fifo list.
+         * Synchronous requests have priority over asynchronous.
+         */
+        if (!list_empty(&zdata->fifo_list[SYNC]))
+                return rq_entry_fifo(zdata->fifo_list[SYNC].next);
+        if (!list_empty(&zdata->fifo_list[ASYNC]))
+                return rq_entry_fifo(zdata->fifo_list[ASYNC].next);
+
+        return NULL;
+}
+
+static int zen_dispatch_requests(struct request_queue *q, int force)
+{
+	struct zen_data *zdata = zen_get_data(q);
+	struct request *rq = NULL;
+
+	/* Check for and issue expired requests */
+	if (zdata->batching > zdata->fifo_batch) {
+		zdata->batching = 0;
+		rq = zen_check_fifo(zdata);
+	}
+
+	if (!rq) {
+		rq = zen_choose_request(zdata);
+		if (!rq)
+			return 0;
+	}
+
+	zen_dispatch(zdata, rq);
+
+	return 1;
+}
+
+static void *zen_init_queue(struct request_queue *q)
+{
+	struct zen_data *zdata;
+
+	zdata = kmalloc_node(sizeof(*zdata), GFP_KERNEL, q->node);
+	if (!zdata)
+		return NULL;
+	INIT_LIST_HEAD(&zdata->fifo_list[SYNC]);
+	INIT_LIST_HEAD(&zdata->fifo_list[ASYNC]);
+	zdata->fifo_expire[SYNC] = sync_expire;
+	zdata->fifo_expire[ASYNC] = async_expire;
+	zdata->fifo_batch = fifo_batch;
+	return zdata;
+}
+
+static void zen_exit_queue(struct elevator_queue *e)
+{
+	struct zen_data *zdata = e->elevator_data;
+
+	BUG_ON(!list_empty(&zdata->fifo_list[SYNC]));
+	BUG_ON(!list_empty(&zdata->fifo_list[ASYNC]));
+	kfree(zdata);
+}
+
+/* Sysfs */
+static ssize_t
+zen_var_show(int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+zen_var_store(int *var, const char *page, size_t count)
+{
+	*var = simple_strtol(page, NULL, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, char *page) \
+{ \
+	struct zen_data *zdata = e->elevator_data; \
+	int __data = __VAR; \
+	if (__CONV) \
+		__data = jiffies_to_msecs(__data); \
+		return zen_var_show(__data, (page)); \
+}
+SHOW_FUNCTION(zen_sync_expire_show, zdata->fifo_expire[SYNC], 1);
+SHOW_FUNCTION(zen_async_expire_show, zdata->fifo_expire[ASYNC], 1);
+SHOW_FUNCTION(zen_fifo_batch_show, zdata->fifo_batch, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
+{ \
+	struct zen_data *zdata = e->elevator_data; \
+	int __data; \
+	int ret = zen_var_store(&__data, (page), count); \
+	if (__data < (MIN)) \
+		__data = (MIN); \
+	else if (__data > (MAX)) \
+		__data = (MAX); \
+	if (__CONV) \
+		*(__PTR) = msecs_to_jiffies(__data); \
+	else \
+		*(__PTR) = __data; \
+	return ret; \
+}
+STORE_FUNCTION(zen_sync_expire_store, &zdata->fifo_expire[SYNC], 0, INT_MAX, 1);
+STORE_FUNCTION(zen_async_expire_store, &zdata->fifo_expire[ASYNC], 0, INT_MAX, 1);
+STORE_FUNCTION(zen_fifo_batch_store, &zdata->fifo_batch, 0, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+#define DD_ATTR(name) \
+        __ATTR(name, S_IRUGO|S_IWUSR, zen_##name##_show, \
+                                      zen_##name##_store)
+
+static struct elv_fs_entry zen_attrs[] = {
+        DD_ATTR(sync_expire),
+        DD_ATTR(async_expire),
+        DD_ATTR(fifo_batch),
+        __ATTR_NULL
+};
+
+static struct elevator_type iosched_zen = {
+	.ops = {
+		.elevator_merge_req_fn		= zen_merged_requests,
+		.elevator_dispatch_fn		= zen_dispatch_requests,
+		.elevator_add_req_fn		= zen_add_request,
+		.elevator_former_req_fn         = elv_rb_former_request,
+		.elevator_latter_req_fn         = elv_rb_latter_request,
+		.elevator_init_fn		= zen_init_queue,
+		.elevator_exit_fn		= zen_exit_queue,
+	},
+	.elevator_attrs = zen_attrs,
+	.elevator_name = "zen",
+	.elevator_owner = THIS_MODULE,
+};
+
+static int __init zen_init(void)
+{
+	elv_register(&iosched_zen);
+
+	return 0;
+}
+
+static void __exit zen_exit(void)
+{
+	elv_unregister(&iosched_zen);
+}
+
+module_init(zen_init);
+module_exit(zen_exit);
+
+
+MODULE_AUTHOR("Brandon Berhent");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Zen IO scheduler");
+MODULE_VERSION("1.0");
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 0bd390c..cbf22b1 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -72,3 +72,9 @@ SUBSYS(net_prio)
 #endif
 
 /* */
+
+#ifdef CONFIG_CGROUP_BFQIO
+SUBSYS(bfqio)
+#endif
+
+/* */
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index b36b28f..3e71452 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -22,6 +22,7 @@ typedef void (elevator_bio_merged_fn) (struct request_queue *,
 typedef int (elevator_dispatch_fn) (struct request_queue *, int);
 
 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
+typedef int (elevator_queue_empty_fn) (struct request_queue *);
 typedef int (elevator_reinsert_req_fn) (struct request_queue *,
 					struct request *);
 typedef bool (elevator_is_urgent_fn) (struct request_queue *);
@@ -55,6 +56,7 @@ struct elevator_ops
 	elevator_activate_req_fn *elevator_activate_req_fn;
 	elevator_deactivate_req_fn *elevator_deactivate_req_fn;
 
+	elevator_queue_empty_fn *elevator_queue_empty_fn;
 	elevator_completed_req_fn *elevator_completed_req_fn;
 
 	elevator_request_list_fn *elevator_former_req_fn;
