BFQ patchset for 4.0, v7r7.

4 files changed, 8304 insertions, 0 deletions

diff --git a/0000_README b/0000_README
index 483ca420..bcce9675 100644
--- a/0000_README
+++ b/0000_README
@@ -83,6 +83,18 @@ Patch:  5000_enable-additional-cpu-optimizations-for-gcc.patch
 From:   https://github.com/graysky2/kernel_gcc_patch/
 Desc:   Kernel patch enables gcc < v4.9 optimizations for additional CPUs.
 
+Patch:  5001_block-cgroups-kconfig-build-bits-for-BFQ-v7r7-4.0.patch
+From:   http://algo.ing.unimo.it/people/paolo/disk_sched/
+Desc:   BFQ v7r7 patch 1 for 4.0: Build, cgroups and kconfig bits
+
+Patch:  5002_block-introduce-the-BFQ-v7r7-I-O-sched-for-4.0.patch1
+From:   http://algo.ing.unimo.it/people/paolo/disk_sched/
+Desc:   BFQ v7r7 patch 2 for 4.0: BFQ Scheduler
+
+Patch:  5003_block-bfq-add-Early-Queue-Merge-EQM-to-BFQ-v7r7-for-4.0.0.patch
+From:   http://algo.ing.unimo.it/people/paolo/disk_sched/
+Desc:   BFQ v7r7 patch 3 for 4.0: Early Queue Merge (EQM)
+
 Patch:  5010_enable-additional-cpu-optimizations-for-gcc-4.9.patch
 From:   https://github.com/graysky2/kernel_gcc_patch/
 Desc:   Kernel patch enables gcc >= v4.9 optimizations for additional CPUs.
diff --git a/5001_block-cgroups-kconfig-build-bits-for-BFQ-v7r7-4.0.patch b/5001_block-cgroups-kconfig-build-bits-for-BFQ-v7r7-4.0.patch
new file mode 100644
index 00000000..468d1573
--- /dev/null
+++ b/5001_block-cgroups-kconfig-build-bits-for-BFQ-v7r7-4.0.patch
@@ -0,0 +1,104 @@
+From 63e26848e2df36a3c29d2d38ce8b008539d64a5d Mon Sep 17 00:00:00 2001
+From: Paolo Valente <paolo.valente@unimore.it>
+Date: Tue, 7 Apr 2015 13:39:12 +0200
+Subject: [PATCH 1/3] block: cgroups, kconfig, build bits for BFQ-v7r7-4.0
+
+Update Kconfig.iosched and do the related Makefile changes to include
+kernel configuration options for BFQ. Also add the bfqio controller
+to the cgroups subsystem.
+
+Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
+Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
+---
+ block/Kconfig.iosched         | 32 ++++++++++++++++++++++++++++++++
+ block/Makefile                |  1 +
+ include/linux/cgroup_subsys.h |  4 ++++
+ 3 files changed, 37 insertions(+)
+
+diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
+index 421bef9..0ee5f0f 100644
+--- a/block/Kconfig.iosched
++++ b/block/Kconfig.iosched
+@@ -39,6 +39,27 @@ config CFQ_GROUP_IOSCHED
+ 	---help---
+ 	  Enable group IO scheduling in CFQ.
+ 
++config IOSCHED_BFQ
++	tristate "BFQ I/O scheduler"
++	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.
++
+ choice
+ 	prompt "Default I/O scheduler"
+ 	default DEFAULT_CFQ
+@@ -52,6 +73,16 @@ choice
+ 	config DEFAULT_CFQ
+ 		bool "CFQ" if IOSCHED_CFQ=y
+ 
++	config DEFAULT_BFQ
++		bool "BFQ" if IOSCHED_BFQ=y
++		help
++		  Selects BFQ as the default I/O scheduler which will be
++		  used by default for all block devices.
++		  The BFQ I/O scheduler 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.
++
+ 	config DEFAULT_NOOP
+ 		bool "No-op"
+ 
+@@ -61,6 +92,7 @@ config DEFAULT_IOSCHED
+ 	string
+ 	default "deadline" if DEFAULT_DEADLINE
+ 	default "cfq" if DEFAULT_CFQ
++	default "bfq" if DEFAULT_BFQ
+ 	default "noop" if DEFAULT_NOOP
+ 
+ endmenu
+diff --git a/block/Makefile b/block/Makefile
+index 00ecc97..1ed86d5 100644
+--- a/block/Makefile
++++ b/block/Makefile
+@@ -18,6 +18,7 @@ obj-$(CONFIG_BLK_DEV_THROTTLING)	+= blk-throttle.o
+ obj-$(CONFIG_IOSCHED_NOOP)	+= noop-iosched.o
+ obj-$(CONFIG_IOSCHED_DEADLINE)	+= deadline-iosched.o
+ obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
++obj-$(CONFIG_IOSCHED_BFQ)	+= bfq-iosched.o
+ 
+ obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
+ obj-$(CONFIG_BLK_CMDLINE_PARSER)	+= cmdline-parser.o
+diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
+index e4a96fb..267d681 100644
+--- a/include/linux/cgroup_subsys.h
++++ b/include/linux/cgroup_subsys.h
+@@ -35,6 +35,10 @@ SUBSYS(freezer)
+ SUBSYS(net_cls)
+ #endif
+ 
++#if IS_ENABLED(CONFIG_CGROUP_BFQIO)
++SUBSYS(bfqio)
++#endif
++
+ #if IS_ENABLED(CONFIG_CGROUP_PERF)
+ SUBSYS(perf_event)
+ #endif
+-- 
+2.1.0
+
diff --git a/5002_block-introduce-the-BFQ-v7r7-I-O-sched-for-4.0.patch1 b/5002_block-introduce-the-BFQ-v7r7-I-O-sched-for-4.0.patch1
new file mode 100644
index 00000000..a6cfc585
--- /dev/null
+++ b/5002_block-introduce-the-BFQ-v7r7-I-O-sched-for-4.0.patch1
@@ -0,0 +1,6966 @@
+From 8cdf2dae6ee87049c7bb086d34e2ce981b545813 Mon Sep 17 00:00:00 2001
+From: Paolo Valente <paolo.valente@unimore.it>
+Date: Thu, 9 May 2013 19:10:02 +0200
+Subject: [PATCH 2/3] block: introduce the BFQ-v7r7 I/O sched for 4.0
+
+Add the BFQ-v7r7 I/O scheduler to 4.0.
+The general structure is borrowed from CFQ, as much of the code for
+handling I/O contexts. Over time, several useful features have been
+ported from CFQ as well (details in the changelog in README.BFQ). A
+(bfq_)queue is associated to each task doing I/O on a device, and each
+time a scheduling decision has to be made a queue is selected and served
+until it expires.
+
+    - Slices are given in the service domain: tasks are assigned
+      budgets, measured in number of sectors. Once got the disk, a task
+      must however consume its assigned budget within a configurable
+      maximum time (by default, the maximum possible value of the
+      budgets is automatically computed to comply with this timeout).
+      This allows the desired latency vs "throughput boosting" tradeoff
+      to be set.
+
+    - Budgets are scheduled according to a variant of WF2Q+, implemented
+      using an augmented rb-tree to take eligibility into account while
+      preserving an O(log N) overall complexity.
+
+    - A low-latency tunable is provided; if enabled, both interactive
+      and soft real-time applications are guaranteed a very low latency.
+
+    - Latency guarantees are preserved also in the presence of NCQ.
+
+    - Also with flash-based devices, a high throughput is achieved
+      while still preserving latency guarantees.
+
+    - BFQ features Early Queue Merge (EQM), a sort of fusion of the
+      cooperating-queue-merging and the preemption mechanisms present
+      in CFQ. EQM is in fact a unified mechanism that tries to get a
+      sequential read pattern, and hence a high throughput, with any
+      set of processes performing interleaved I/O over a contiguous
+      sequence of sectors.
+
+    - BFQ supports full hierarchical scheduling, exporting a cgroups
+      interface.  Since each node has a full scheduler, each group can
+      be assigned its own weight.
+
+    - If the cgroups interface is not used, only I/O priorities can be
+      assigned to processes, with ioprio values mapped to weights
+      with the relation weight = IOPRIO_BE_NR - ioprio.
+
+    - ioprio classes are served in strict priority order, i.e., lower
+      priority queues are not served as long as there are higher
+      priority queues.  Among queues in the same class the bandwidth is
+      distributed in proportion to the weight of each queue. A very
+      thin extra bandwidth is however guaranteed to the Idle class, to
+      prevent it from starving.
+
+Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
+Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
+---
+ block/bfq-cgroup.c  |  936 ++++++++++++
+ block/bfq-ioc.c     |   36 +
+ block/bfq-iosched.c | 3902 +++++++++++++++++++++++++++++++++++++++++++++++++++
+ block/bfq-sched.c   | 1214 ++++++++++++++++
+ block/bfq.h         |  775 ++++++++++
+ 5 files changed, 6863 insertions(+)
+ 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
+
+diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
+new file mode 100644
+index 0000000..11e2f1d
+--- /dev/null
++++ b/block/bfq-cgroup.c
+@@ -0,0 +1,936 @@
++/*
++ * 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 DEFINE_MUTEX(bfqio_mutex);
++
++static bool bfqio_is_removed(struct bfqio_cgroup *bgrp)
++{
++	return bgrp ? !bgrp->online : false;
++}
++
++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 *css_to_bfqio(struct cgroup_subsys_state *css)
++{
++	return css ? container_of(css, struct bfqio_cgroup, css) : NULL;
++}
++
++/*
++ * 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;
++	void *key;
++
++	hlist_for_each_entry_rcu(bfqg, &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.
++ * @css: the leaf cgroup_subsys_state 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_subsys_state *css)
++{
++	struct bfqio_cgroup *bgrp;
++	struct bfq_group *bfqg, *prev = NULL, *leaf = NULL;
++
++	for (; css != NULL; css = css->parent) {
++		bgrp = css_to_bfqio(css);
++
++		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.
++ * @css: the leaf cgroup_subsys_state 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_subsys_state *css,
++				 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 (; css != NULL && leaf != NULL; css = css->parent) {
++		bgrp = css_to_bfqio(css);
++		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(css == NULL && leaf != NULL);
++	if (css != NULL && prev != NULL) {
++		bgrp = css_to_bfqio(css);
++		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_subsys_state *css)
++{
++	struct bfqio_cgroup *bgrp = css_to_bfqio(css);
++	struct bfq_group *bfqg;
++
++	bfqg = bfqio_lookup_group(bgrp, bfqd);
++	if (bfqg != NULL)
++		return bfqg;
++
++	bfqg = bfq_group_chain_alloc(bfqd, css);
++	if (bfqg != NULL)
++		bfq_group_chain_link(bfqd, css, 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_subsys_state *css)
++{
++	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 = css_to_bfqio(css);
++
++	bfqg = bfq_find_alloc_group(bfqd, css);
++	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_subsys_state *css)
++{
++	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, css);
++		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_subsys_state *css;
++
++	BUG_ON(bfqd == NULL);
++
++	rcu_read_lock();
++	css = task_css(current, bfqio_cgrp_id);
++	bfqg = __bfq_bic_change_cgroup(bfqd, bic, css);
++	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 *tmp;
++	struct bfq_group *bfqg;
++
++	hlist_for_each_entry_safe(bfqg, tmp, &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 *tmp;
++	struct bfq_group *bfqg;
++
++	bfq_log(bfqd, "disconnect_groups beginning");
++	hlist_for_each_entry_safe(bfqg, tmp, &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_subsys_state *css, \
++				       struct cftype *cftype)		\
++{									\
++	struct bfqio_cgroup *bgrp = css_to_bfqio(css);			\
++	u64 ret = -ENODEV;						\
++									\
++	mutex_lock(&bfqio_mutex);					\
++	if (bfqio_is_removed(bgrp))					\
++		goto out_unlock;					\
++									\
++	spin_lock_irq(&bgrp->lock);					\
++	ret = bgrp->__VAR;						\
++	spin_unlock_irq(&bgrp->lock);					\
++									\
++out_unlock:								\
++	mutex_unlock(&bfqio_mutex);					\
++	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_subsys_state *css,\
++					struct cftype *cftype,		\
++					u64 val)			\
++{									\
++	struct bfqio_cgroup *bgrp = css_to_bfqio(css);			\
++	struct bfq_group *bfqg;						\
++	int ret = -EINVAL;						\
++									\
++	if (val < (__MIN) || val > (__MAX))				\
++		return ret;						\
++									\
++	ret = -ENODEV;							\
++	mutex_lock(&bfqio_mutex);					\
++	if (bfqio_is_removed(bgrp))					\
++		goto out_unlock;					\
++	ret = 0;							\
++									\
++	spin_lock_irq(&bgrp->lock);					\
++	bgrp->__VAR = (unsigned short)val;				\
++	hlist_for_each_entry(bfqg, &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);					\
++									\
++out_unlock:								\
++	mutex_unlock(&bfqio_mutex);					\
++	return ret;							\
++}
++
++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,
++	},
++	{ },	/* terminate */
++};
++
++static struct cgroup_subsys_state *bfqio_create(struct cgroup_subsys_state
++						*parent_css)
++{
++	struct bfqio_cgroup *bgrp;
++
++	if (parent_css != 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_subsys_state *css,
++			    struct cgroup_taskset *tset)
++{
++	struct task_struct *task;
++	struct io_context *ioc;
++	int ret = 0;
++
++	cgroup_taskset_for_each(task, 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_subsys_state *css,
++			 struct cgroup_taskset *tset)
++{
++	struct task_struct *task;
++	struct io_context *ioc;
++	struct io_cq *icq;
++
++	/*
++	 * 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, 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, &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),
++							      css);
++			rcu_read_unlock();
++			put_io_context(ioc);
++		}
++	}
++}
++
++static void bfqio_destroy(struct cgroup_subsys_state *css)
++{
++	struct bfqio_cgroup *bgrp = css_to_bfqio(css);
++	struct hlist_node *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, tmp, &bgrp->group_data, group_node)
++		bfq_destroy_group(bgrp, bfqg);
++
++	BUG_ON(!hlist_empty(&bgrp->group_data));
++
++	kfree(bgrp);
++}
++
++static int bfqio_css_online(struct cgroup_subsys_state *css)
++{
++	struct bfqio_cgroup *bgrp = css_to_bfqio(css);
++
++	mutex_lock(&bfqio_mutex);
++	bgrp->online = true;
++	mutex_unlock(&bfqio_mutex);
++
++	return 0;
++}
++
++static void bfqio_css_offline(struct cgroup_subsys_state *css)
++{
++	struct bfqio_cgroup *bgrp = css_to_bfqio(css);
++
++	mutex_lock(&bfqio_mutex);
++	bgrp->online = false;
++	mutex_unlock(&bfqio_mutex);
++}
++
++struct cgroup_subsys bfqio_cgrp_subsys = {
++	.css_alloc = bfqio_create,
++	.css_online = bfqio_css_online,
++	.css_offline = bfqio_css_offline,
++	.can_attach = bfqio_can_attach,
++	.attach = bfqio_attach,
++	.css_free = bfqio_destroy,
++	.legacy_cftypes = bfqio_files,
++};
++#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..97ee934
+--- /dev/null
++++ b/block/bfq-iosched.c
+@@ -0,0 +1,3902 @@
++/*
++ * 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->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;
++}
++
++/* 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 *n;
++
++	hlist_for_each_entry_safe(item, 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 *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, &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, 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,
++		     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;
++		}
++
++		soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 &&
++			!bfq_bfqq_in_large_burst(bfqq) &&
++			time_is_before_jiffies(bfqq->soft_rt_next_start);
++		interactive = !bfq_bfqq_in_large_burst(bfqq) &&
++			      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 the queue is not being boosted and has been idle
++		 * for enough time, start a weight-raising period
++		 */
++		if (old_wr_coeff == 1 && (interactive || soft_rt)) {
++			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 (bfq_bfqq_in_large_burst(bfqq) ||
++				 (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;
++			}
++		}
++		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)
++		return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio));
++
++	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(next->fifo_time, rq->fifo_time)) {
++		list_move(&rq->queuelist, &next->queuelist);
++		rq->fifo_time = next->fifo_time;
++	}
++
++	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 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;
++
++	/*
++	 * 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));
++	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)
++{
++	if (!bfqq)
++		bfqq = bfq_get_next_queue(bfqd);
++	else
++		bfq_get_next_queue_forced(bfqd, bfqq);
++
++	__bfq_set_in_service_queue(bfqd, bfqq);
++	return bfqq;
++}
++
++static inline sector_t bfq_dist_from_last(struct bfq_data *bfqd,
++					  struct request *rq)
++{
++	if (blk_rq_pos(rq) >= bfqd->last_position)
++		return blk_rq_pos(rq) - bfqd->last_position;
++	else
++		return bfqd->last_position - blk_rq_pos(rq);
++}
++
++/*
++ * Return true if bfqq has no request pending and rq is close enough to
++ * bfqd->last_position, or if rq is closer to bfqd->last_position than
++ * bfqq->next_rq
++ */
++static inline int bfq_rq_close(struct bfq_data *bfqd, struct request *rq)
++{
++	return bfq_dist_from_last(bfqd, rq) <= BFQQ_SEEK_THR;
++}
++
++static struct bfq_queue *bfqq_close(struct bfq_data *bfqd)
++{
++	struct rb_root *root = &bfqd->rq_pos_tree;
++	struct rb_node *parent, *node;
++	struct bfq_queue *__bfqq;
++	sector_t sector = bfqd->last_position;
++
++	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(bfqd, __bfqq->next_rq))
++		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(bfqd, __bfqq->next_rq))
++		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.
++ *
++ * We are assuming that cur_bfqq has dispatched at least one request,
++ * and that bfqd->last_position reflects a position on the disk associated
++ * with the I/O issued by cur_bfqq.
++ */
++static struct bfq_queue *bfq_close_cooperator(struct bfq_data *bfqd,
++					      struct bfq_queue *cur_bfqq)
++{
++	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);
++	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;
++}
++
++/*
++ * 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->active_ref) == 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))
++		return NULL;
++
++	return rq;
++}
++
++/* 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;
++}
++
++static void 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;
++
++	/* Avoid a circular list and skip interim queue merges. */
++	while ((__bfqq = new_bfqq->new_bfqq)) {
++		if (__bfqq == bfqq)
++			return;
++		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;
++
++	/*
++	 * Merge in the direction of the lesser amount of work.
++	 */
++	if (new_process_refs >= process_refs) {
++		bfqq->new_bfqq = new_bfqq;
++		atomic_add(process_refs, &new_bfqq->ref);
++	} else {
++		new_bfqq->new_bfqq = bfqq;
++		atomic_add(new_process_refs, &bfqq->ref);
++	}
++	bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d",
++		new_bfqq->pid);
++}
++
++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, *new_bfqq = NULL;
++	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 another queue has a request waiting within our mean seek
++         * distance, let it run. The expire code will check for close
++         * cooperators and put the close queue at the front of the
++         * service tree. If possible, merge the expiring queue with the
++         * new bfqq.
++         */
++        new_bfqq = bfq_close_cooperator(bfqd, bfqq);
++        if (new_bfqq != NULL && bfqq->new_bfqq == NULL)
++                bfq_setup_merge(bfqq, new_bfqq);
++
++	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);
++			}
++			if (new_bfqq == NULL)
++				goto keep_queue;
++			else
++				goto expire;
++		}
++	}
++
++	/*
++	 * 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 (new_bfqq == NULL && (timer_pending(&bfqd->idle_slice_timer) ||
++	    (bfqq->dispatched != 0 && bfq_bfqq_must_not_expire(bfqq)))) {
++		bfqq = NULL;
++		goto keep_queue;
++	} else if (new_bfqq != NULL && timer_pending(&bfqd->idle_slice_timer)) {
++		/*
++		 * Expiring the queue because there is a close cooperator,
++		 * cancel timer.
++		 */
++		bfq_clear_bfqq_wait_request(bfqq);
++		del_timer(&bfqd->idle_slice_timer);
++	}
++
++	reason = BFQ_BFQQ_NO_MORE_REQUESTS;
++expire:
++	bfq_bfqq_expire(bfqd, bfqq, 0, reason);
++new_queue:
++	bfqq = bfq_set_in_service_queue(bfqd, new_bfqq);
++	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)
++{
++	if (bfqq->wr_coeff > 1) { /* queue is being boosted */
++		struct bfq_entity *entity = &bfqq->entity;
++
++		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, then end weight raising.
++		 */
++		if (bfq_bfqq_in_large_burst(bfqq) ||
++		    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);
++			__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;
++}
++
++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]) {
++		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 bfq_io_cq *bic)
++{
++	struct task_struct *tsk = current;
++	int ioprio_class;
++
++	if (!bfq_bfqq_prio_changed(bfqq))
++		return;
++
++	ioprio_class = IOPRIO_PRIO_CLASS(bic->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 = IOPRIO_PRIO_DATA(bic->ioprio);
++		bfqq->entity.new_ioprio_class = IOPRIO_CLASS_RT;
++		break;
++	case IOPRIO_CLASS_BE:
++		bfqq->entity.new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
++		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 bfq_io_cq *bic)
++{
++	struct bfq_data *bfqd;
++	struct bfq_queue *bfqq, *new_bfqq;
++	struct bfq_group *bfqg;
++	unsigned long uninitialized_var(flags);
++	int ioprio = bic->icq.ioc->ioprio;
++
++	bfqd = bfq_get_bfqd_locked(&(bic->icq.q->elevator->elevator_data),
++				   &flags);
++	/*
++	 * This condition may trigger on a newly created bic, be sure to
++	 * drop the lock before returning.
++	 */
++	if (unlikely(bfqd == NULL) || likely(bic->ioprio == ioprio))
++		goto out;
++
++	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,
++					 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);
++
++	bic->ioprio = ioprio;
++
++out:
++	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 bfq_io_cq *bic,
++					      gfp_t gfp_mask)
++{
++	struct bfq_queue *bfqq, *new_bfqq = NULL;
++
++retry:
++	/* 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, bic);
++			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_NONE:
++		ioprio = IOPRIO_NORM;
++		/* fall through */
++	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 bfq_io_cq *bic, gfp_t gfp_mask)
++{
++	const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
++	const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
++	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, bic, 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;
++
++	enable_idle = bfq_bfqq_idle_window(bfqq);
++
++	if (atomic_read(&bic->icq.ioc->active_ref) == 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_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);
++
++	assert_spin_locked(bfqd->queue->queue_lock);
++	bfq_init_prio_data(bfqq, RQ_BIC(rq));
++
++	bfq_add_request(rq);
++
++	rq->fifo_time = 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);
++
++		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);
++	}
++}
++
++static struct bfq_queue *
++bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
++		struct bfq_queue *bfqq)
++{
++	bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu",
++		(long unsigned)bfqq->new_bfqq->pid);
++	bic_set_bfqq(bic, bfqq->new_bfqq, 1);
++	bfq_mark_bfqq_coop(bfqq->new_bfqq);
++	bfq_put_queue(bfqq);
++	return bic_to_bfqq(bic, 1);
++}
++
++/*
++ * 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");
++	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,
++			   struct bio *bio, 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;
++
++	might_sleep_if(gfp_mask & __GFP_WAIT);
++
++	bfq_changed_ioprio(bic);
++
++	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, gfp_mask);
++		bic_set_bfqq(bic, bfqq, is_sync);
++	} 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);
++			if (!bfqq)
++				goto new_queue;
++		}
++
++		/*
++		 * Check to see if this queue is scheduled to merge with
++		 * another closely cooperating queue. The merging of queues
++		 * happens here as it must be done in process context.
++		 * The reference on new_bfqq was taken in merge_bfqqs.
++		 */
++		if (bfqq->new_bfqq != NULL)
++			bfqq = bfq_merge_bfqqs(bfqd, bic, bfqq);
++	}
++
++	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;
++
++	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 int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
++{
++	struct bfq_group *bfqg;
++	struct bfq_data *bfqd;
++	struct elevator_queue *eq;
++
++	eq = elevator_alloc(q, e);
++	if (eq == NULL)
++		return -ENOMEM;
++
++	bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node);
++	if (bfqd == NULL) {
++		kobject_put(&eq->kobj);
++		return -ENOMEM;
++	}
++	eq->elevator_data = bfqd;
++
++	/*
++	 * 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;
++
++	spin_lock_irq(q->queue_lock);
++	q->elevator = eq;
++	spin_unlock_irq(q->queue_lock);
++
++	bfqg = bfq_alloc_root_group(bfqd, q->node);
++	if (bfqg == NULL) {
++		kfree(bfqd);
++		kobject_put(&eq->kobj);
++		return -ENOMEM;
++	}
++
++	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 0;
++}
++
++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..2931563
+--- /dev/null
++++ b/block/bfq-sched.c
+@@ -0,0 +1,1214 @@
++/*
++ * 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;
++}
++
++/*
++ * Forced extraction of the given queue.
++ */
++static void bfq_get_next_queue_forced(struct bfq_data *bfqd,
++				      struct bfq_queue *bfqq)
++{
++	struct bfq_entity *entity;
++	struct bfq_sched_data *sd;
++
++	BUG_ON(bfqd->in_service_queue != NULL);
++
++	entity = &bfqq->entity;
++	/*
++	 * Bubble up extraction/update from the leaf to the root.
++	*/
++	for_each_entity(entity) {
++		sd = entity->sched_data;
++		bfq_update_budget(entity);
++		bfq_update_vtime(bfq_entity_service_tree(entity));
++		bfq_active_extract(bfq_entity_service_tree(entity), entity);
++		sd->in_service_entity = entity;
++		sd->next_in_service = NULL;
++		entity->service = 0;
++	}
++
++	return;
++}
++
++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..518f2ac
+--- /dev/null
++++ b/block/bfq.h
+@@ -0,0 +1,775 @@
++/*
++ * BFQ-v7r7 for 4.0.0: 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
++ *
++ * 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;
++
++	/* 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
++ */
++struct bfq_io_cq {
++	struct io_cq icq; /* must be the first member */
++	struct bfq_queue *bfqq[2];
++	struct bfq_ttime ttime;
++	int ioprio;
++};
++
++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 splitted */
++};
++
++#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(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.
++ * @online: flag marked when the subsystem is inserted.
++ * @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;
++	bool online;
++
++	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 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 bfq_io_cq *bic, 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 */
+-- 
+2.1.0
+
diff --git a/5003_block-bfq-add-Early-Queue-Merge-EQM-to-BFQ-v7r7-for-4.0.0.patch b/5003_block-bfq-add-Early-Queue-Merge-EQM-to-BFQ-v7r7-for-4.0.0.patch
new file mode 100644
index 00000000..53267cdd
--- /dev/null
+++ b/5003_block-bfq-add-Early-Queue-Merge-EQM-to-BFQ-v7r7-for-4.0.0.patch
@@ -0,0 +1,1222 @@
+From d49cf2e7913ec1c4b86a9de657140d9ec5fa8c19 Mon Sep 17 00:00:00 2001
+From: Mauro Andreolini <mauro.andreolini@unimore.it>
+Date: Thu, 18 Dec 2014 21:32:08 +0100
+Subject: [PATCH 3/3] block, bfq: add Early Queue Merge (EQM) to BFQ-v7r7 for
+ 4.0.0
+
+A set of processes may happen  to  perform interleaved reads, i.e.,requests
+whose union would give rise to a  sequential read  pattern.  There are two
+typical  cases: in the first  case,   processes  read  fixed-size chunks of
+data at a fixed distance from each other, while in the second case processes
+may read variable-size chunks at  variable distances. The latter case occurs
+for  example with  QEMU, which  splits the  I/O generated  by the  guest into
+multiple chunks,  and lets these chunks  be served by a  pool of cooperating
+processes,  iteratively  assigning  the  next  chunk of  I/O  to  the first
+available  process. CFQ  uses actual  queue merging  for the  first type of
+rocesses, whereas it  uses preemption to get a sequential  read pattern out
+of the read requests  performed by the second type of  processes. In the end
+it uses  two different  mechanisms to  achieve the  same goal: boosting the
+throughput with interleaved I/O.
+
+This patch introduces  Early Queue Merge (EQM), a unified mechanism to get a
+sequential  read pattern  with both  types of  processes. The  main idea is
+checking newly arrived requests against the next request of the active queue
+both in case of actual request insert and in case of request merge. By doing
+so, both the types of processes can be handled by just merging their queues.
+EQM is  then simpler and  more compact than the  pair of mechanisms used in
+CFQ.
+
+Finally, EQM  also preserves the  typical low-latency properties of BFQ, by
+properly restoring the weight-raising state of a queue when it gets back to
+a non-merged state.
+
+Signed-off-by: Mauro Andreolini <mauro.andreolini@unimore.it>
+Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
+Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
+---
+ block/bfq-iosched.c | 751 +++++++++++++++++++++++++++++++++++++---------------
+ block/bfq-sched.c   |  28 --
+ block/bfq.h         |  54 +++-
+ 3 files changed, 581 insertions(+), 252 deletions(-)
+
+diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
+index 97ee934..328f33c 100644
+--- a/block/bfq-iosched.c
++++ b/block/bfq-iosched.c
+@@ -571,6 +571,57 @@ static inline unsigned int bfq_wr_duration(struct bfq_data *bfqd)
+ 	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)
+@@ -815,7 +866,7 @@ static void bfq_add_request(struct request *rq)
+ 		bfq_rq_pos_tree_add(bfqd, bfqq);
+ 
+ 	if (!bfq_bfqq_busy(bfqq)) {
+-		bool soft_rt,
++		bool soft_rt, coop_or_in_burst,
+ 		     idle_for_long_time = time_is_before_jiffies(
+ 						bfqq->budget_timeout +
+ 						bfqd->bfq_wr_min_idle_time);
+@@ -839,11 +890,12 @@ static void bfq_add_request(struct request *rq)
+ 				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 &&
+-			!bfq_bfqq_in_large_burst(bfqq) &&
++			!coop_or_in_burst &&
+ 			time_is_before_jiffies(bfqq->soft_rt_next_start);
+-		interactive = !bfq_bfqq_in_large_burst(bfqq) &&
+-			      idle_for_long_time;
++		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));
+ 
+@@ -862,11 +914,20 @@ static void bfq_add_request(struct request *rq)
+ 		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 and has been idle
+-		 * for enough time, start a weight-raising period
++		 * 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)) {
++		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);
+@@ -880,7 +941,7 @@ static void bfq_add_request(struct request *rq)
+ 		} else if (old_wr_coeff > 1) {
+ 			if (interactive)
+ 				bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
+-			else if (bfq_bfqq_in_large_burst(bfqq) ||
++			else if (coop_or_in_burst ||
+ 				 (bfqq->wr_cur_max_time ==
+ 				  bfqd->bfq_wr_rt_max_time &&
+ 				  !soft_rt)) {
+@@ -899,18 +960,18 @@ static void bfq_add_request(struct request *rq)
+ 				/*
+ 				 *
+ 				 * 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).
++				 * 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.
+@@ -945,6 +1006,7 @@ static void bfq_add_request(struct request *rq)
+ 					bfqd->bfq_wr_rt_max_time;
+ 			}
+ 		}
++set_ioprio_changed:
+ 		if (old_wr_coeff != bfqq->wr_coeff)
+ 			entity->ioprio_changed = 1;
+ add_bfqq_busy:
+@@ -1156,90 +1218,35 @@ static void bfq_end_wr(struct bfq_data *bfqd)
+ 	spin_unlock_irq(bfqd->queue->queue_lock);
+ }
+ 
+-static int bfq_allow_merge(struct request_queue *q, struct request *rq,
+-			   struct bio *bio)
++static inline sector_t bfq_io_struct_pos(void *io_struct, bool request)
+ {
+-	struct bfq_data *bfqd = q->elevator->elevator_data;
+-	struct bfq_io_cq *bic;
+-	struct bfq_queue *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));
+-	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)
+-{
+-	if (!bfqq)
+-		bfqq = bfq_get_next_queue(bfqd);
++	if (request)
++		return blk_rq_pos(io_struct);
+ 	else
+-		bfq_get_next_queue_forced(bfqd, bfqq);
+-
+-	__bfq_set_in_service_queue(bfqd, bfqq);
+-	return bfqq;
++		return ((struct bio *)io_struct)->bi_iter.bi_sector;
+ }
+ 
+-static inline sector_t bfq_dist_from_last(struct bfq_data *bfqd,
+-					  struct request *rq)
++static inline sector_t bfq_dist_from(sector_t pos1,
++				     sector_t pos2)
+ {
+-	if (blk_rq_pos(rq) >= bfqd->last_position)
+-		return blk_rq_pos(rq) - bfqd->last_position;
++	if (pos1 >= pos2)
++		return pos1 - pos2;
+ 	else
+-		return bfqd->last_position - blk_rq_pos(rq);
++		return pos2 - pos1;
+ }
+ 
+-/*
+- * Return true if bfqq has no request pending and rq is close enough to
+- * bfqd->last_position, or if rq is closer to bfqd->last_position than
+- * bfqq->next_rq
+- */
+-static inline int bfq_rq_close(struct bfq_data *bfqd, struct request *rq)
++static inline int bfq_rq_close_to_sector(void *io_struct, bool request,
++					 sector_t sector)
+ {
+-	return bfq_dist_from_last(bfqd, rq) <= BFQQ_SEEK_THR;
++	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)
++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;
+-	sector_t sector = bfqd->last_position;
+ 
+ 	if (RB_EMPTY_ROOT(root))
+ 		return NULL;
+@@ -1258,7 +1265,7 @@ static struct bfq_queue *bfqq_close(struct bfq_data *bfqd)
+ 	 * next_request position).
+ 	 */
+ 	__bfqq = rb_entry(parent, struct bfq_queue, pos_node);
+-	if (bfq_rq_close(bfqd, __bfqq->next_rq))
++	if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
+ 		return __bfqq;
+ 
+ 	if (blk_rq_pos(__bfqq->next_rq) < sector)
+@@ -1269,7 +1276,7 @@ static struct bfq_queue *bfqq_close(struct bfq_data *bfqd)
+ 		return NULL;
+ 
+ 	__bfqq = rb_entry(node, struct bfq_queue, pos_node);
+-	if (bfq_rq_close(bfqd, __bfqq->next_rq))
++	if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
+ 		return __bfqq;
+ 
+ 	return NULL;
+@@ -1278,14 +1285,12 @@ static struct bfq_queue *bfqq_close(struct bfq_data *bfqd)
+ /*
+  * bfqd - obvious
+  * cur_bfqq - passed in so that we don't decide that the current queue
+- *            is closely cooperating with itself.
+- *
+- * We are assuming that cur_bfqq has dispatched at least one request,
+- * and that bfqd->last_position reflects a position on the disk associated
+- * with the I/O issued by cur_bfqq.
++ *            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)
++					      struct bfq_queue *cur_bfqq,
++					      sector_t sector)
+ {
+ 	struct bfq_queue *bfqq;
+ 
+@@ -1305,7 +1310,7 @@ static struct bfq_queue *bfq_close_cooperator(struct bfq_data *bfqd,
+ 	 * 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);
++	bfqq = bfqq_close(bfqd, sector);
+ 	if (bfqq == NULL || bfqq == cur_bfqq)
+ 		return NULL;
+ 
+@@ -1332,6 +1337,315 @@ static struct bfq_queue *bfq_close_cooperator(struct bfq_data *bfqd,
+ 	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
+@@ -1475,61 +1789,6 @@ static struct request *bfq_check_fifo(struct bfq_queue *bfqq)
+ 	return rq;
+ }
+ 
+-/* 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;
+-}
+-
+-static void 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;
+-
+-	/* Avoid a circular list and skip interim queue merges. */
+-	while ((__bfqq = new_bfqq->new_bfqq)) {
+-		if (__bfqq == bfqq)
+-			return;
+-		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;
+-
+-	/*
+-	 * Merge in the direction of the lesser amount of work.
+-	 */
+-	if (new_process_refs >= process_refs) {
+-		bfqq->new_bfqq = new_bfqq;
+-		atomic_add(process_refs, &new_bfqq->ref);
+-	} else {
+-		new_bfqq->new_bfqq = bfqq;
+-		atomic_add(new_process_refs, &bfqq->ref);
+-	}
+-	bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d",
+-		new_bfqq->pid);
+-}
+-
+ static inline unsigned long bfq_bfqq_budget_left(struct bfq_queue *bfqq)
+ {
+ 	struct bfq_entity *entity = &bfqq->entity;
+@@ -2263,7 +2522,7 @@ static inline bool bfq_bfqq_must_idle(struct bfq_queue *bfqq)
+  */
+ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
+ {
+-	struct bfq_queue *bfqq, *new_bfqq = NULL;
++	struct bfq_queue *bfqq;
+ 	struct request *next_rq;
+ 	enum bfqq_expiration reason = BFQ_BFQQ_BUDGET_TIMEOUT;
+ 
+@@ -2273,17 +2532,6 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
+ 
+ 	bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue");
+ 
+-	/*
+-         * If another queue has a request waiting within our mean seek
+-         * distance, let it run. The expire code will check for close
+-         * cooperators and put the close queue at the front of the
+-         * service tree. If possible, merge the expiring queue with the
+-         * new bfqq.
+-         */
+-        new_bfqq = bfq_close_cooperator(bfqd, bfqq);
+-        if (new_bfqq != NULL && bfqq->new_bfqq == NULL)
+-                bfq_setup_merge(bfqq, new_bfqq);
+-
+ 	if (bfq_may_expire_for_budg_timeout(bfqq) &&
+ 	    !timer_pending(&bfqd->idle_slice_timer) &&
+ 	    !bfq_bfqq_must_idle(bfqq))
+@@ -2322,10 +2570,7 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
+ 				bfq_clear_bfqq_wait_request(bfqq);
+ 				del_timer(&bfqd->idle_slice_timer);
+ 			}
+-			if (new_bfqq == NULL)
+-				goto keep_queue;
+-			else
+-				goto expire;
++			goto keep_queue;
+ 		}
+ 	}
+ 
+@@ -2334,40 +2579,30 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
+ 	 * in flight (possibly waiting for a completion) or is idling for a
+ 	 * new request, then keep it.
+ 	 */
+-	if (new_bfqq == NULL && (timer_pending(&bfqd->idle_slice_timer) ||
+-	    (bfqq->dispatched != 0 && bfq_bfqq_must_not_expire(bfqq)))) {
++	if (timer_pending(&bfqd->idle_slice_timer) ||
++	    (bfqq->dispatched != 0 && bfq_bfqq_must_not_expire(bfqq))) {
+ 		bfqq = NULL;
+ 		goto keep_queue;
+-	} else if (new_bfqq != NULL && timer_pending(&bfqd->idle_slice_timer)) {
+-		/*
+-		 * Expiring the queue because there is a close cooperator,
+-		 * cancel timer.
+-		 */
+-		bfq_clear_bfqq_wait_request(bfqq);
+-		del_timer(&bfqd->idle_slice_timer);
+ 	}
+ 
+ 	reason = BFQ_BFQQ_NO_MORE_REQUESTS;
+ expire:
+ 	bfq_bfqq_expire(bfqd, bfqq, 0, reason);
+ new_queue:
+-	bfqq = bfq_set_in_service_queue(bfqd, new_bfqq);
++	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)
++static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq)
+ {
+-	if (bfqq->wr_coeff > 1) { /* queue is being boosted */
+-		struct bfq_entity *entity = &bfqq->entity;
+-
++	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(jiffies - bfqq->last_wr_start_finish),
+ 			jiffies_to_msecs(bfqq->wr_cur_max_time),
+ 			bfqq->wr_coeff,
+ 			bfqq->entity.weight, bfqq->entity.orig_weight);
+@@ -2376,12 +2611,16 @@ static void bfq_update_wr_data(struct bfq_data *bfqd,
+ 		       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, then end weight raising.
++		 * 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;
+@@ -2390,11 +2629,13 @@ static void bfq_update_wr_data(struct bfq_data *bfqd,
+ 				     bfqq->last_wr_start_finish,
+ 				     jiffies_to_msecs(bfqq->wr_cur_max_time));
+ 			bfq_bfqq_end_wr(bfqq);
+-			__bfq_entity_update_weight_prio(
+-				bfq_entity_service_tree(entity),
+-				entity);
+ 		}
+ 	}
++	/* 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);
+ }
+ 
+ /*
+@@ -2642,6 +2883,25 @@ 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)
+@@ -2655,6 +2915,13 @@ static void bfq_exit_icq(struct io_cq *icq)
+ 	}
+ 
+ 	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;
+ 	}
+@@ -2950,6 +3217,10 @@ static void bfq_update_idle_window(struct bfq_data *bfqd,
+ 	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->active_ref) == 0 ||
+@@ -2997,6 +3268,7 @@ static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+ 	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)",
+@@ -3057,13 +3329,49 @@ static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+ 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);
++	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));
+ 
+ 	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->fifo_time = jiffies + bfqd->bfq_fifo_expire[rq_is_sync(rq)];
+ 	list_add_tail(&rq->queuelist, &bfqq->fifo);
+ 
+@@ -3228,18 +3536,6 @@ static void bfq_put_request(struct request *rq)
+ 	}
+ }
+ 
+-static struct bfq_queue *
+-bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
+-		struct bfq_queue *bfqq)
+-{
+-	bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu",
+-		(long unsigned)bfqq->new_bfqq->pid);
+-	bic_set_bfqq(bic, bfqq->new_bfqq, 1);
+-	bfq_mark_bfqq_coop(bfqq->new_bfqq);
+-	bfq_put_queue(bfqq);
+-	return bic_to_bfqq(bic, 1);
+-}
+-
+ /*
+  * Returns NULL if a new bfqq should be allocated, or the old bfqq if this
+  * was the last process referring to said bfqq.
+@@ -3248,6 +3544,9 @@ 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);
+@@ -3276,6 +3575,7 @@ static int bfq_set_request(struct request_queue *q, struct request *rq,
+ 	struct bfq_queue *bfqq;
+ 	struct bfq_group *bfqg;
+ 	unsigned long flags;
++	bool split = false;
+ 
+ 	might_sleep_if(gfp_mask & __GFP_WAIT);
+ 
+@@ -3293,25 +3593,26 @@ new_queue:
+ 	if (bfqq == NULL || bfqq == &bfqd->oom_bfqq) {
+ 		bfqq = bfq_get_queue(bfqd, bfqg, is_sync, bic, 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 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;
+ 		}
+-
+-		/*
+-		 * Check to see if this queue is scheduled to merge with
+-		 * another closely cooperating queue. The merging of queues
+-		 * happens here as it must be done in process context.
+-		 * The reference on new_bfqq was taken in merge_bfqqs.
+-		 */
+-		if (bfqq->new_bfqq != NULL)
+-			bfqq = bfq_merge_bfqqs(bfqd, bic, bfqq);
+ 	}
+ 
+ 	bfqq->allocated[rw]++;
+@@ -3322,6 +3623,26 @@ new_queue:
+ 	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;
+diff --git a/block/bfq-sched.c b/block/bfq-sched.c
+index 2931563..6764a7e 100644
+--- a/block/bfq-sched.c
++++ b/block/bfq-sched.c
+@@ -1091,34 +1091,6 @@ static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)
+ 	return bfqq;
+ }
+ 
+-/*
+- * Forced extraction of the given queue.
+- */
+-static void bfq_get_next_queue_forced(struct bfq_data *bfqd,
+-				      struct bfq_queue *bfqq)
+-{
+-	struct bfq_entity *entity;
+-	struct bfq_sched_data *sd;
+-
+-	BUG_ON(bfqd->in_service_queue != NULL);
+-
+-	entity = &bfqq->entity;
+-	/*
+-	 * Bubble up extraction/update from the leaf to the root.
+-	*/
+-	for_each_entity(entity) {
+-		sd = entity->sched_data;
+-		bfq_update_budget(entity);
+-		bfq_update_vtime(bfq_entity_service_tree(entity));
+-		bfq_active_extract(bfq_entity_service_tree(entity), entity);
+-		sd->in_service_entity = entity;
+-		sd->next_in_service = NULL;
+-		entity->service = 0;
+-	}
+-
+-	return;
+-}
+-
+ static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
+ {
+ 	if (bfqd->in_service_bic != NULL) {
+diff --git a/block/bfq.h b/block/bfq.h
+index 518f2ac..4f519ea 100644
+--- a/block/bfq.h
++++ b/block/bfq.h
+@@ -218,18 +218,21 @@ struct bfq_group;
+  *                      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()).
++ *                      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).
++ * 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 {
+@@ -269,6 +272,7 @@ struct bfq_queue {
+ 	unsigned int requests_within_timer;
+ 
+ 	pid_t pid;
++	struct bfq_io_cq *bic;
+ 
+ 	/* weight-raising fields */
+ 	unsigned long wr_cur_max_time;
+@@ -298,12 +302,42 @@ struct bfq_ttime {
+  * @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;
+ 	int ioprio;
++
++	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 {
+@@ -539,7 +573,7 @@ enum bfqq_state_flags {
+ 	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,         /*
++	BFQ_BFQQ_FLAG_IO_bound,		/*
+ 					 * bfqq has timed-out at least once
+ 					 * having consumed at most 2/10 of
+ 					 * its budget
+@@ -552,12 +586,13 @@ enum bfqq_state_flags {
+ 					 * bfqq has proved to be slow and
+ 					 * seeky until budget timeout
+ 					 */
+-	BFQ_BFQQ_FLAG_softrt_update,    /*
++	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 splitted */
++	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)						\
+@@ -587,6 +622,7 @@ 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
+ 
+-- 
+2.1.0
+