Initial import

1 files changed, 936 insertions, 0 deletions

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
new file mode 100644
index 000000000..11e2f1d4e
--- /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