text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * cgroups support for the BFQ I/O scheduler.
   */
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/blkdev.h>
  #include <linux/cgroup.h>
  #include <linux/elevator.h>
  #include <linux/ktime.h>
  #include <linux/rbtree.h>
  #include <linux/ioprio.h>
  #include <linux/sbitmap.h>
  #include <linux/delay.h>
  
  #include "bfq-iosched.h"
  
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  static int bfq_stat_init(struct bfq_stat *stat, gfp_t gfp)
  {
  	int ret;
  
  	ret = percpu_counter_init(&stat->cpu_cnt, 0, gfp);
  	if (ret)
  		return ret;
  
  	atomic64_set(&stat->aux_cnt, 0);
  	return 0;
  }
  
  static void bfq_stat_exit(struct bfq_stat *stat)
  {
  	percpu_counter_destroy(&stat->cpu_cnt);
  }
  
  /**
   * bfq_stat_add - add a value to a bfq_stat
   * @stat: target bfq_stat
   * @val: value to add
   *
   * Add @val to @stat.  The caller must ensure that IRQ on the same CPU
   * don't re-enter this function for the same counter.
   */
  static inline void bfq_stat_add(struct bfq_stat *stat, uint64_t val)
  {
  	percpu_counter_add_batch(&stat->cpu_cnt, val, BLKG_STAT_CPU_BATCH);
  }
  
  /**
   * bfq_stat_read - read the current value of a bfq_stat
   * @stat: bfq_stat to read
   */
  static inline uint64_t bfq_stat_read(struct bfq_stat *stat)
  {
  	return percpu_counter_sum_positive(&stat->cpu_cnt);
  }
  
  /**
   * bfq_stat_reset - reset a bfq_stat
   * @stat: bfq_stat to reset
   */
  static inline void bfq_stat_reset(struct bfq_stat *stat)
  {
  	percpu_counter_set(&stat->cpu_cnt, 0);
  	atomic64_set(&stat->aux_cnt, 0);
  }
  
  /**
   * bfq_stat_add_aux - add a bfq_stat into another's aux count
   * @to: the destination bfq_stat
   * @from: the source
   *
   * Add @from's count including the aux one to @to's aux count.
   */
  static inline void bfq_stat_add_aux(struct bfq_stat *to,
  				     struct bfq_stat *from)
  {
  	atomic64_add(bfq_stat_read(from) + atomic64_read(&from->aux_cnt),
  		     &to->aux_cnt);
  }
  
  /**
   * blkg_prfill_stat - prfill callback for bfq_stat
   * @sf: seq_file to print to
   * @pd: policy private data of interest
   * @off: offset to the bfq_stat in @pd
   *
   * prfill callback for printing a bfq_stat.
   */
  static u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd,
  		int off)
  {
  	return __blkg_prfill_u64(sf, pd, bfq_stat_read((void *)pd + off));
  }
  
  /* bfqg stats flags */
  enum bfqg_stats_flags {
  	BFQG_stats_waiting = 0,
  	BFQG_stats_idling,
  	BFQG_stats_empty,
  };
  
  #define BFQG_FLAG_FNS(name)						\
  static void bfqg_stats_mark_##name(struct bfqg_stats *stats)	\
  {									\
  	stats->flags |= (1 << BFQG_stats_##name);			\
  }									\
  static void bfqg_stats_clear_##name(struct bfqg_stats *stats)	\
  {									\
  	stats->flags &= ~(1 << BFQG_stats_##name);			\
  }									\
  static int bfqg_stats_##name(struct bfqg_stats *stats)		\
  {									\
  	return (stats->flags & (1 << BFQG_stats_##name)) != 0;		\
  }									\
  
  BFQG_FLAG_FNS(waiting)
  BFQG_FLAG_FNS(idling)
  BFQG_FLAG_FNS(empty)
  #undef BFQG_FLAG_FNS
  
  /* This should be called with the scheduler lock held. */
  static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats)
  {
  	u64 now;
  
  	if (!bfqg_stats_waiting(stats))
  		return;
  
  	now = ktime_get_ns();
  	if (now > stats->start_group_wait_time)
  		bfq_stat_add(&stats->group_wait_time,
  			      now - stats->start_group_wait_time);
  	bfqg_stats_clear_waiting(stats);
  }
  
  /* This should be called with the scheduler lock held. */
  static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
  						 struct bfq_group *curr_bfqg)
  {
  	struct bfqg_stats *stats = &bfqg->stats;
  
  	if (bfqg_stats_waiting(stats))
  		return;
  	if (bfqg == curr_bfqg)
  		return;
  	stats->start_group_wait_time = ktime_get_ns();
  	bfqg_stats_mark_waiting(stats);
  }
  
  /* This should be called with the scheduler lock held. */
  static void bfqg_stats_end_empty_time(struct bfqg_stats *stats)
  {
  	u64 now;
  
  	if (!bfqg_stats_empty(stats))
  		return;
  
  	now = ktime_get_ns();
  	if (now > stats->start_empty_time)
  		bfq_stat_add(&stats->empty_time,
  			      now - stats->start_empty_time);
  	bfqg_stats_clear_empty(stats);
  }
  
  void bfqg_stats_update_dequeue(struct bfq_group *bfqg)
  {
  	bfq_stat_add(&bfqg->stats.dequeue, 1);
  }
  
  void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg)
  {
  	struct bfqg_stats *stats = &bfqg->stats;
  
  	if (blkg_rwstat_total(&stats->queued))
  		return;
  
  	/*
  	 * group is already marked empty. This can happen if bfqq got new
  	 * request in parent group and moved to this group while being added
  	 * to service tree. Just ignore the event and move on.
  	 */
  	if (bfqg_stats_empty(stats))
  		return;
  
  	stats->start_empty_time = ktime_get_ns();
  	bfqg_stats_mark_empty(stats);
  }
  
  void bfqg_stats_update_idle_time(struct bfq_group *bfqg)
  {
  	struct bfqg_stats *stats = &bfqg->stats;
  
  	if (bfqg_stats_idling(stats)) {
  		u64 now = ktime_get_ns();
  
  		if (now > stats->start_idle_time)
  			bfq_stat_add(&stats->idle_time,
  				      now - stats->start_idle_time);
  		bfqg_stats_clear_idling(stats);
  	}
  }
  
  void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg)
  {
  	struct bfqg_stats *stats = &bfqg->stats;
  
  	stats->start_idle_time = ktime_get_ns();
  	bfqg_stats_mark_idling(stats);
  }
  
  void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg)
  {
  	struct bfqg_stats *stats = &bfqg->stats;
  
  	bfq_stat_add(&stats->avg_queue_size_sum,
  		      blkg_rwstat_total(&stats->queued));
  	bfq_stat_add(&stats->avg_queue_size_samples, 1);
  	bfqg_stats_update_group_wait_time(stats);
  }
  
  void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
  			      unsigned int op)
  {
  	blkg_rwstat_add(&bfqg->stats.queued, op, 1);
  	bfqg_stats_end_empty_time(&bfqg->stats);
  	if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
  		bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
  }
  
  void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
  {
  	blkg_rwstat_add(&bfqg->stats.queued, op, -1);
  }
  
  void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
  {
  	blkg_rwstat_add(&bfqg->stats.merged, op, 1);
  }
  
  void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
  				  u64 io_start_time_ns, unsigned int op)
  {
  	struct bfqg_stats *stats = &bfqg->stats;
  	u64 now = ktime_get_ns();
  
  	if (now > io_start_time_ns)
  		blkg_rwstat_add(&stats->service_time, op,
  				now - io_start_time_ns);
  	if (io_start_time_ns > start_time_ns)
  		blkg_rwstat_add(&stats->wait_time, op,
  				io_start_time_ns - start_time_ns);
  }
  
  #else /* CONFIG_BFQ_CGROUP_DEBUG */
  
  void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
  			      unsigned int op) { }
  void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
  void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
  void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
  				  u64 io_start_time_ns, unsigned int op) { }
  void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
  void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
  void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
  void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
  void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
  
  #endif /* CONFIG_BFQ_CGROUP_DEBUG */
  
  #ifdef CONFIG_BFQ_GROUP_IOSCHED
  
  /*
   * blk-cgroup policy-related handlers
   * The following functions help in converting between blk-cgroup
   * internal structures and BFQ-specific structures.
   */
  
  static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd)
  {
  	return pd ? container_of(pd, struct bfq_group, pd) : NULL;
  }
  
  struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg)
  {
  	return pd_to_blkg(&bfqg->pd);
  }
  
  static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg)
  {
  	return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq));
  }
  
  /*
   * bfq_group handlers
   * The following functions help in navigating the bfq_group hierarchy
   * by allowing to find the parent of a bfq_group or the bfq_group
   * associated to a bfq_queue.
   */
  
  static struct bfq_group *bfqg_parent(struct bfq_group *bfqg)
  {
  	struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent;
  
  	return pblkg ? blkg_to_bfqg(pblkg) : NULL;
  }
  
  struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
  {
  	struct bfq_entity *group_entity = bfqq->entity.parent;
  
  	return group_entity ? container_of(group_entity, struct bfq_group,
  					   entity) :
  			      bfqq->bfqd->root_group;
  }
  
  /*
   * The following two functions handle get and put of a bfq_group by
   * wrapping the related blk-cgroup hooks.
   */
  
  static void bfqg_get(struct bfq_group *bfqg)
  {
  	bfqg->ref++;
  }
  
  static void bfqg_put(struct bfq_group *bfqg)
  {
  	bfqg->ref--;
  
  	if (bfqg->ref == 0)
  		kfree(bfqg);
  }
  
  static void bfqg_and_blkg_get(struct bfq_group *bfqg)
  {
  	/* see comments in bfq_bic_update_cgroup for why refcounting bfqg */
  	bfqg_get(bfqg);
  
  	blkg_get(bfqg_to_blkg(bfqg));
  }
  
  void bfqg_and_blkg_put(struct bfq_group *bfqg)
  {
  	blkg_put(bfqg_to_blkg(bfqg));
  
  	bfqg_put(bfqg);
  }
  
  void bfqg_stats_update_legacy_io(struct request_queue *q, struct request *rq)
  {
  	struct bfq_group *bfqg = blkg_to_bfqg(rq->bio->bi_blkg);
  
  	if (!bfqg)
  		return;
  
  	blkg_rwstat_add(&bfqg->stats.bytes, rq->cmd_flags, blk_rq_bytes(rq));
  	blkg_rwstat_add(&bfqg->stats.ios, rq->cmd_flags, 1);
  }
  
  /* @stats = 0 */
  static void bfqg_stats_reset(struct bfqg_stats *stats)
  {
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  	/* queued stats shouldn't be cleared */
  	blkg_rwstat_reset(&stats->merged);
  	blkg_rwstat_reset(&stats->service_time);
  	blkg_rwstat_reset(&stats->wait_time);
  	bfq_stat_reset(&stats->time);
  	bfq_stat_reset(&stats->avg_queue_size_sum);
  	bfq_stat_reset(&stats->avg_queue_size_samples);
  	bfq_stat_reset(&stats->dequeue);
  	bfq_stat_reset(&stats->group_wait_time);
  	bfq_stat_reset(&stats->idle_time);
  	bfq_stat_reset(&stats->empty_time);
  #endif
  }
  
  /* @to += @from */
  static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
  {
  	if (!to || !from)
  		return;
  
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  	/* queued stats shouldn't be cleared */
  	blkg_rwstat_add_aux(&to->merged, &from->merged);
  	blkg_rwstat_add_aux(&to->service_time, &from->service_time);
  	blkg_rwstat_add_aux(&to->wait_time, &from->wait_time);
  	bfq_stat_add_aux(&from->time, &from->time);
  	bfq_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
  	bfq_stat_add_aux(&to->avg_queue_size_samples,
  			  &from->avg_queue_size_samples);
  	bfq_stat_add_aux(&to->dequeue, &from->dequeue);
  	bfq_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
  	bfq_stat_add_aux(&to->idle_time, &from->idle_time);
  	bfq_stat_add_aux(&to->empty_time, &from->empty_time);
  #endif
  }
  
  /*
   * Transfer @bfqg's stats to its parent's aux counts so that the ancestors'
   * recursive stats can still account for the amount used by this bfqg after
   * it's gone.
   */
  static void bfqg_stats_xfer_dead(struct bfq_group *bfqg)
  {
  	struct bfq_group *parent;
  
  	if (!bfqg) /* root_group */
  		return;
  
  	parent = bfqg_parent(bfqg);
  
  	lockdep_assert_held(&bfqg_to_blkg(bfqg)->q->queue_lock);
  
  	if (unlikely(!parent))
  		return;
  
  	bfqg_stats_add_aux(&parent->stats, &bfqg->stats);
  	bfqg_stats_reset(&bfqg->stats);
  }
  
  void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
  {
  	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
  
  	entity->weight = entity->new_weight;
  	entity->orig_weight = entity->new_weight;
  	if (bfqq) {
  		bfqq->ioprio = bfqq->new_ioprio;
  		bfqq->ioprio_class = bfqq->new_ioprio_class;
  		/*
  		 * Make sure that bfqg and its associated blkg do not
  		 * disappear before entity.
  		 */
  		bfqg_and_blkg_get(bfqg);
  	}
  	entity->parent = bfqg->my_entity; /* NULL for root group */
  	entity->sched_data = &bfqg->sched_data;
  }
  
  static void bfqg_stats_exit(struct bfqg_stats *stats)
  {
  	blkg_rwstat_exit(&stats->bytes);
  	blkg_rwstat_exit(&stats->ios);
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  	blkg_rwstat_exit(&stats->merged);
  	blkg_rwstat_exit(&stats->service_time);
  	blkg_rwstat_exit(&stats->wait_time);
  	blkg_rwstat_exit(&stats->queued);
  	bfq_stat_exit(&stats->time);
  	bfq_stat_exit(&stats->avg_queue_size_sum);
  	bfq_stat_exit(&stats->avg_queue_size_samples);
  	bfq_stat_exit(&stats->dequeue);
  	bfq_stat_exit(&stats->group_wait_time);
  	bfq_stat_exit(&stats->idle_time);
  	bfq_stat_exit(&stats->empty_time);
  #endif
  }
  
  static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
  {
  	if (blkg_rwstat_init(&stats->bytes, gfp) ||
  	    blkg_rwstat_init(&stats->ios, gfp))
  		return -ENOMEM;
  
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  	if (blkg_rwstat_init(&stats->merged, gfp) ||
  	    blkg_rwstat_init(&stats->service_time, gfp) ||
  	    blkg_rwstat_init(&stats->wait_time, gfp) ||
  	    blkg_rwstat_init(&stats->queued, gfp) ||
  	    bfq_stat_init(&stats->time, gfp) ||
  	    bfq_stat_init(&stats->avg_queue_size_sum, gfp) ||
  	    bfq_stat_init(&stats->avg_queue_size_samples, gfp) ||
  	    bfq_stat_init(&stats->dequeue, gfp) ||
  	    bfq_stat_init(&stats->group_wait_time, gfp) ||
  	    bfq_stat_init(&stats->idle_time, gfp) ||
  	    bfq_stat_init(&stats->empty_time, gfp)) {
  		bfqg_stats_exit(stats);
  		return -ENOMEM;
  	}
  #endif
  
  	return 0;
  }
  
  static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd)
  {
  	return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL;
  }
  
  static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg)
  {
  	return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq));
  }
  
  static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp)
  {
  	struct bfq_group_data *bgd;
  
  	bgd = kzalloc(sizeof(*bgd), gfp);
  	if (!bgd)
  		return NULL;
  	return &bgd->pd;
  }
  
  static void bfq_cpd_init(struct blkcg_policy_data *cpd)
  {
  	struct bfq_group_data *d = cpd_to_bfqgd(cpd);
  
  	d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
  		CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL;
  }
  
  static void bfq_cpd_free(struct blkcg_policy_data *cpd)
  {
  	kfree(cpd_to_bfqgd(cpd));
  }
  
  static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, struct request_queue *q,
  					     struct blkcg *blkcg)
  {
  	struct bfq_group *bfqg;
  
  	bfqg = kzalloc_node(sizeof(*bfqg), gfp, q->node);
  	if (!bfqg)
  		return NULL;
  
  	if (bfqg_stats_init(&bfqg->stats, gfp)) {
  		kfree(bfqg);
  		return NULL;
  	}
  
  	/* see comments in bfq_bic_update_cgroup for why refcounting */
  	bfqg_get(bfqg);
  	return &bfqg->pd;
  }
  
  static void bfq_pd_init(struct blkg_policy_data *pd)
  {
  	struct blkcg_gq *blkg = pd_to_blkg(pd);
  	struct bfq_group *bfqg = blkg_to_bfqg(blkg);
  	struct bfq_data *bfqd = blkg->q->elevator->elevator_data;
  	struct bfq_entity *entity = &bfqg->entity;
  	struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg);
  
  	entity->orig_weight = entity->weight = entity->new_weight = d->weight;
  	entity->my_sched_data = &bfqg->sched_data;
  	bfqg->my_entity = entity; /*
  				   * the root_group's will be set to NULL
  				   * in bfq_init_queue()
  				   */
  	bfqg->bfqd = bfqd;
  	bfqg->active_entities = 0;
  	bfqg->rq_pos_tree = RB_ROOT;
  }
  
  static void bfq_pd_free(struct blkg_policy_data *pd)
  {
  	struct bfq_group *bfqg = pd_to_bfqg(pd);
  
  	bfqg_stats_exit(&bfqg->stats);
  	bfqg_put(bfqg);
  }
  
  static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
  {
  	struct bfq_group *bfqg = pd_to_bfqg(pd);
  
  	bfqg_stats_reset(&bfqg->stats);
  }
  
  static void bfq_group_set_parent(struct bfq_group *bfqg,
  					struct bfq_group *parent)
  {
  	struct bfq_entity *entity;
  
  	entity = &bfqg->entity;
  	entity->parent = parent->my_entity;
  	entity->sched_data = &parent->sched_data;
  }
  
  static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd,
  					 struct blkcg *blkcg)
  {
  	struct blkcg_gq *blkg;
  
  	blkg = blkg_lookup(blkcg, bfqd->queue);
  	if (likely(blkg))
  		return blkg_to_bfqg(blkg);
  	return NULL;
  }
  
  struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
  				     struct blkcg *blkcg)
  {
  	struct bfq_group *bfqg, *parent;
  	struct bfq_entity *entity;
  
  	bfqg = bfq_lookup_bfqg(bfqd, blkcg);
  
  	if (unlikely(!bfqg))
  		return NULL;
  
  	/*
  	 * Update chain of bfq_groups as we might be handling a leaf group
  	 * which, along with some of its relatives, has not been hooked yet
  	 * to the private hierarchy of BFQ.
  	 */
  	entity = &bfqg->entity;
  	for_each_entity(entity) {
  		struct bfq_group *curr_bfqg = container_of(entity,
  						struct bfq_group, entity);
  		if (curr_bfqg != bfqd->root_group) {
  			parent = bfqg_parent(curr_bfqg);
  			if (!parent)
  				parent = bfqd->root_group;
  			bfq_group_set_parent(curr_bfqg, parent);
  		}
  	}
  
  	return bfqg;
  }
  
  /**
   * bfq_bfqq_move - migrate @bfqq to @bfqg.
   * @bfqd: queue descriptor.
   * @bfqq: the queue to move.
   * @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 scheduler lock, to make sure that the blkg
   * owning @bfqg does not disappear (see comments in
   * bfq_bic_update_cgroup on guaranteeing the consistency of blkg
   * objects).
   */
  void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  		   struct bfq_group *bfqg)
  {
  	struct bfq_entity *entity = &bfqq->entity;
  
  	/*
  	 * Get extra reference to prevent bfqq from being freed in
  	 * next possible expire or deactivate.
  	 */
  	bfqq->ref++;
  
  	/* If bfqq is empty, then bfq_bfqq_expire also invokes
  	 * bfq_del_bfqq_busy, thereby removing bfqq and its entity
  	 * from data structures related to current group. Otherwise we
  	 * need to remove bfqq explicitly with bfq_deactivate_bfqq, as
  	 * we do below.
  	 */
  	if (bfqq == bfqd->in_service_queue)
  		bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
  				false, BFQQE_PREEMPTED);
  
  	if (bfq_bfqq_busy(bfqq))
  		bfq_deactivate_bfqq(bfqd, bfqq, false, false);
  	else if (entity->on_st_or_in_serv)
  		bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
  	bfqg_and_blkg_put(bfqq_group(bfqq));
  
  	entity->parent = bfqg->my_entity;
  	entity->sched_data = &bfqg->sched_data;
  	/* pin down bfqg and its associated blkg  */
  	bfqg_and_blkg_get(bfqg);
  
  	if (bfq_bfqq_busy(bfqq)) {
  		if (unlikely(!bfqd->nonrot_with_queueing))
  			bfq_pos_tree_add_move(bfqd, bfqq);
  		bfq_activate_bfqq(bfqd, bfqq);
  	}
  
  	if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
  		bfq_schedule_dispatch(bfqd);
  	/* release extra ref taken above, bfqq may happen to be freed now */
  	bfq_put_queue(bfqq);
  }
  
  /**
   * __bfq_bic_change_cgroup - move @bic to @cgroup.
   * @bfqd: the queue descriptor.
   * @bic: the bic to move.
   * @blkcg: the blk-cgroup to move to.
   *
   * Move bic to blkcg, assuming that bfqd->lock is held; which makes
   * sure that the reference to cgroup is valid across the call (see
   * comments in bfq_bic_update_cgroup on this issue)
   *
   * 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 blkcg *blkcg)
  {
  	struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
  	struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
  	struct bfq_group *bfqg;
  	struct bfq_entity *entity;
  
  	bfqg = bfq_find_set_group(bfqd, blkcg);
  
  	if (unlikely(!bfqg))
  		bfqg = bfqd->root_group;
  
  	if (async_bfqq) {
  		entity = &async_bfqq->entity;
  
  		if (entity->sched_data != &bfqg->sched_data) {
  			bic_set_bfqq(bic, NULL, 0);
  			bfq_release_process_ref(bfqd, async_bfqq);
  		}
  	}
  
  	if (sync_bfqq) {
  		entity = &sync_bfqq->entity;
  		if (entity->sched_data != &bfqg->sched_data)
  			bfq_bfqq_move(bfqd, sync_bfqq, bfqg);
  	}
  
  	return bfqg;
  }
  
  void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
  {
  	struct bfq_data *bfqd = bic_to_bfqd(bic);
  	struct bfq_group *bfqg = NULL;
  	uint64_t serial_nr;
  
  	rcu_read_lock();
  	serial_nr = __bio_blkcg(bio)->css.serial_nr;
  
  	/*
  	 * Check whether blkcg has changed.  The condition may trigger
  	 * spuriously on a newly created cic but there's no harm.
  	 */
  	if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr))
  		goto out;
  
  	bfqg = __bfq_bic_change_cgroup(bfqd, bic, __bio_blkcg(bio));
  	/*
  	 * Update blkg_path for bfq_log_* functions. We cache this
  	 * path, and update it here, for the following
  	 * reasons. Operations on blkg objects in blk-cgroup are
  	 * protected with the request_queue lock, and not with the
  	 * lock that protects the instances of this scheduler
  	 * (bfqd->lock). This exposes BFQ to the following sort of
  	 * race.
  	 *
  	 * The blkg_lookup performed in bfq_get_queue, protected
  	 * through rcu, may happen to return the address of a copy of
  	 * the original blkg. If this is the case, then the
  	 * bfqg_and_blkg_get performed in bfq_get_queue, to pin down
  	 * the blkg, is useless: it does not prevent blk-cgroup code
  	 * from destroying both the original blkg and all objects
  	 * directly or indirectly referred by the copy of the
  	 * blkg.
  	 *
  	 * On the bright side, destroy operations on a blkg invoke, as
  	 * a first step, hooks of the scheduler associated with the
  	 * blkg. And these hooks are executed with bfqd->lock held for
  	 * BFQ. As a consequence, for any blkg associated with the
  	 * request queue this instance of the scheduler is attached
  	 * to, we are guaranteed that such a blkg is not destroyed, and
  	 * that all the pointers it contains are consistent, while we
  	 * are holding bfqd->lock. A blkg_lookup performed with
  	 * bfqd->lock held then returns a fully consistent blkg, which
  	 * remains consistent until this lock is held.
  	 *
  	 * Thanks to the last fact, and to the fact that: (1) bfqg has
  	 * been obtained through a blkg_lookup in the above
  	 * assignment, and (2) bfqd->lock is being held, here we can
  	 * safely use the policy data for the involved blkg (i.e., the
  	 * field bfqg->pd) to get to the blkg associated with bfqg,
  	 * and then we can safely use any field of blkg. After we
  	 * release bfqd->lock, even just getting blkg through this
  	 * bfqg may cause dangling references to be traversed, as
  	 * bfqg->pd may not exist any more.
  	 *
  	 * In view of the above facts, here we cache, in the bfqg, any
  	 * blkg data we may need for this bic, and for its associated
  	 * bfq_queue. As of now, we need to cache only the path of the
  	 * blkg, which is used in the bfq_log_* functions.
  	 *
  	 * Finally, note that bfqg itself needs to be protected from
  	 * destruction on the blkg_free of the original blkg (which
  	 * invokes bfq_pd_free). We use an additional private
  	 * refcounter for bfqg, to let it disappear only after no
  	 * bfq_queue refers to it any longer.
  	 */
  	blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path));
  	bic->blkcg_serial_nr = serial_nr;
  out:
  	rcu_read_unlock();
  }
  
  /**
   * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
   * @st: the service tree being flushed.
   */
  static void bfq_flush_idle_tree(struct bfq_service_tree *st)
  {
  	struct bfq_entity *entity = st->first_idle;
  
  	for (; entity ; entity = st->first_idle)
  		__bfq_deactivate_entity(entity, false);
  }
  
  /**
   * 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, if entity is a leaf; or the parent entity
   *	    of an active leaf entity to move, if entity is not a leaf.
   */
  static void bfq_reparent_leaf_entity(struct bfq_data *bfqd,
  				     struct bfq_entity *entity,
  				     int ioprio_class)
  {
  	struct bfq_queue *bfqq;
  	struct bfq_entity *child_entity = entity;
  
  	while (child_entity->my_sched_data) { /* leaf not reached yet */
  		struct bfq_sched_data *child_sd = child_entity->my_sched_data;
  		struct bfq_service_tree *child_st = child_sd->service_tree +
  			ioprio_class;
  		struct rb_root *child_active = &child_st->active;
  
  		child_entity = bfq_entity_of(rb_first(child_active));
  
  		if (!child_entity)
  			child_entity = child_sd->in_service_entity;
  	}
  
  	bfqq = bfq_entity_to_bfqq(child_entity);
  	bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
  }
  
  /**
   * bfq_reparent_active_queues - move to the root group all active queues.
   * @bfqd: the device data structure with the root group.
   * @bfqg: the group to move from.
   * @st: the service tree to start the search from.
   */
  static void bfq_reparent_active_queues(struct bfq_data *bfqd,
  				       struct bfq_group *bfqg,
  				       struct bfq_service_tree *st,
  				       int ioprio_class)
  {
  	struct rb_root *active = &st->active;
  	struct bfq_entity *entity;
  
  	while ((entity = bfq_entity_of(rb_first(active))))
  		bfq_reparent_leaf_entity(bfqd, entity, ioprio_class);
  
  	if (bfqg->sched_data.in_service_entity)
  		bfq_reparent_leaf_entity(bfqd,
  					 bfqg->sched_data.in_service_entity,
  					 ioprio_class);
  }
  
  /**
   * bfq_pd_offline - deactivate the entity associated with @pd,
   *		    and reparent its children entities.
   * @pd: descriptor of the policy going offline.
   *
   * blkio already grabs the queue_lock for us, so no need to use
   * RCU-based magic
   */
  static void bfq_pd_offline(struct blkg_policy_data *pd)
  {
  	struct bfq_service_tree *st;
  	struct bfq_group *bfqg = pd_to_bfqg(pd);
  	struct bfq_data *bfqd = bfqg->bfqd;
  	struct bfq_entity *entity = bfqg->my_entity;
  	unsigned long flags;
  	int i;
  
  	spin_lock_irqsave(&bfqd->lock, flags);
  
  	if (!entity) /* root group */
  		goto put_async_queues;
  
  	/*
  	 * 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;
  
  		/*
  		 * 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.
  		 */
  		bfq_reparent_active_queues(bfqd, bfqg, st, 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. In addition, even
  		 * bfq_reparent_active_queues() may happen to add some
  		 * entities to the idle tree. It happens if, in some
  		 * of the calls to bfq_bfqq_move() performed by
  		 * bfq_reparent_active_queues(), the queue to move is
  		 * empty and gets expired.
  		 */
  		bfq_flush_idle_tree(st);
  	}
  
  	__bfq_deactivate_entity(entity, false);
  
  put_async_queues:
  	bfq_put_async_queues(bfqd, bfqg);
  
  	spin_unlock_irqrestore(&bfqd->lock, flags);
  	/*
  	 * @blkg is going offline and will be ignored by
  	 * blkg_[rw]stat_recursive_sum().  Transfer stats to the parent so
  	 * that they don't get lost.  If IOs complete after this point, the
  	 * stats for them will be lost.  Oh well...
  	 */
  	bfqg_stats_xfer_dead(bfqg);
  }
  
  void bfq_end_wr_async(struct bfq_data *bfqd)
  {
  	struct blkcg_gq *blkg;
  
  	list_for_each_entry(blkg, &bfqd->queue->blkg_list, q_node) {
  		struct bfq_group *bfqg = blkg_to_bfqg(blkg);
  
  		bfq_end_wr_async_queues(bfqd, bfqg);
  	}
  	bfq_end_wr_async_queues(bfqd, bfqd->root_group);
  }
  
  static int bfq_io_show_weight_legacy(struct seq_file *sf, void *v)
  {
  	struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
  	struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
  	unsigned int val = 0;
  
  	if (bfqgd)
  		val = bfqgd->weight;
  
  	seq_printf(sf, "%u\n", val);
  
  	return 0;
  }
  
  static u64 bfqg_prfill_weight_device(struct seq_file *sf,
  				     struct blkg_policy_data *pd, int off)
  {
  	struct bfq_group *bfqg = pd_to_bfqg(pd);
  
  	if (!bfqg->entity.dev_weight)
  		return 0;
  	return __blkg_prfill_u64(sf, pd, bfqg->entity.dev_weight);
  }
  
  static int bfq_io_show_weight(struct seq_file *sf, void *v)
  {
  	struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
  	struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
  
  	seq_printf(sf, "default %u\n", bfqgd->weight);
  	blkcg_print_blkgs(sf, blkcg, bfqg_prfill_weight_device,
  			  &blkcg_policy_bfq, 0, false);
  	return 0;
  }
  
  static void bfq_group_set_weight(struct bfq_group *bfqg, u64 weight, u64 dev_weight)
  {
  	weight = dev_weight ?: weight;
  
  	bfqg->entity.dev_weight = dev_weight;
  	/*
  	 * Setting the prio_changed flag of the entity
  	 * to 1 with new_weight == weight would re-set
  	 * the value of the weight to its ioprio mapping.
  	 * Set the flag only if necessary.
  	 */
  	if ((unsigned short)weight != bfqg->entity.new_weight) {
  		bfqg->entity.new_weight = (unsigned short)weight;
  		/*
  		 * Make sure that the above new value has been
  		 * stored in bfqg->entity.new_weight before
  		 * setting the prio_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_weight (in
  		 * __bfq_entity_update_weight_prio).
  		 * This barrier makes sure that the new value
  		 * of bfqg->entity.new_weight is correctly
  		 * seen in that code.
  		 */
  		smp_wmb();
  		bfqg->entity.prio_changed = 1;
  	}
  }
  
  static int bfq_io_set_weight_legacy(struct cgroup_subsys_state *css,
  				    struct cftype *cftype,
  				    u64 val)
  {
  	struct blkcg *blkcg = css_to_blkcg(css);
  	struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
  	struct blkcg_gq *blkg;
  	int ret = -ERANGE;
  
  	if (val < BFQ_MIN_WEIGHT || val > BFQ_MAX_WEIGHT)
  		return ret;
  
  	ret = 0;
  	spin_lock_irq(&blkcg->lock);
  	bfqgd->weight = (unsigned short)val;
  	hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
  		struct bfq_group *bfqg = blkg_to_bfqg(blkg);
  
  		if (bfqg)
  			bfq_group_set_weight(bfqg, val, 0);
  	}
  	spin_unlock_irq(&blkcg->lock);
  
  	return ret;
  }
  
  static ssize_t bfq_io_set_device_weight(struct kernfs_open_file *of,
  					char *buf, size_t nbytes,
  					loff_t off)
  {
  	int ret;
  	struct blkg_conf_ctx ctx;
  	struct blkcg *blkcg = css_to_blkcg(of_css(of));
  	struct bfq_group *bfqg;
  	u64 v;
  
  	ret = blkg_conf_prep(blkcg, &blkcg_policy_bfq, buf, &ctx);
  	if (ret)
  		return ret;
  
  	if (sscanf(ctx.body, "%llu", &v) == 1) {
  		/* require "default" on dfl */
  		ret = -ERANGE;
  		if (!v)
  			goto out;
  	} else if (!strcmp(strim(ctx.body), "default")) {
  		v = 0;
  	} else {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	bfqg = blkg_to_bfqg(ctx.blkg);
  
  	ret = -ERANGE;
  	if (!v || (v >= BFQ_MIN_WEIGHT && v <= BFQ_MAX_WEIGHT)) {
  		bfq_group_set_weight(bfqg, bfqg->entity.weight, v);
  		ret = 0;
  	}
  out:
  	blkg_conf_finish(&ctx);
  	return ret ?: nbytes;
  }
  
  static ssize_t bfq_io_set_weight(struct kernfs_open_file *of,
  				 char *buf, size_t nbytes,
  				 loff_t off)
  {
  	char *endp;
  	int ret;
  	u64 v;
  
  	buf = strim(buf);
  
  	/* "WEIGHT" or "default WEIGHT" sets the default weight */
  	v = simple_strtoull(buf, &endp, 0);
  	if (*endp == '\0' || sscanf(buf, "default %llu", &v) == 1) {
  		ret = bfq_io_set_weight_legacy(of_css(of), NULL, v);
  		return ret ?: nbytes;
  	}
  
  	return bfq_io_set_device_weight(of, buf, nbytes, off);
  }
  
  static int bfqg_print_rwstat(struct seq_file *sf, void *v)
  {
  	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
  			  &blkcg_policy_bfq, seq_cft(sf)->private, true);
  	return 0;
  }
  
  static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf,
  					struct blkg_policy_data *pd, int off)
  {
  	struct blkg_rwstat_sample sum;
  
  	blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq, off, &sum);
  	return __blkg_prfill_rwstat(sf, pd, &sum);
  }
  
  static int bfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
  {
  	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
  			  bfqg_prfill_rwstat_recursive, &blkcg_policy_bfq,
  			  seq_cft(sf)->private, true);
  	return 0;
  }
  
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  static int bfqg_print_stat(struct seq_file *sf, void *v)
  {
  	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
  			  &blkcg_policy_bfq, seq_cft(sf)->private, false);
  	return 0;
  }
  
  static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
  				      struct blkg_policy_data *pd, int off)
  {
  	struct blkcg_gq *blkg = pd_to_blkg(pd);
  	struct blkcg_gq *pos_blkg;
  	struct cgroup_subsys_state *pos_css;
  	u64 sum = 0;
  
  	lockdep_assert_held(&blkg->q->queue_lock);
  
  	rcu_read_lock();
  	blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
  		struct bfq_stat *stat;
  
  		if (!pos_blkg->online)
  			continue;
  
  		stat = (void *)blkg_to_pd(pos_blkg, &blkcg_policy_bfq) + off;
  		sum += bfq_stat_read(stat) + atomic64_read(&stat->aux_cnt);
  	}
  	rcu_read_unlock();
  
  	return __blkg_prfill_u64(sf, pd, sum);
  }
  
  static int bfqg_print_stat_recursive(struct seq_file *sf, void *v)
  {
  	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
  			  bfqg_prfill_stat_recursive, &blkcg_policy_bfq,
  			  seq_cft(sf)->private, false);
  	return 0;
  }
  
  static u64 bfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
  			       int off)
  {
  	struct bfq_group *bfqg = blkg_to_bfqg(pd->blkg);
  	u64 sum = blkg_rwstat_total(&bfqg->stats.bytes);
  
  	return __blkg_prfill_u64(sf, pd, sum >> 9);
  }
  
  static int bfqg_print_stat_sectors(struct seq_file *sf, void *v)
  {
  	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
  			  bfqg_prfill_sectors, &blkcg_policy_bfq, 0, false);
  	return 0;
  }
  
  static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf,
  					 struct blkg_policy_data *pd, int off)
  {
  	struct blkg_rwstat_sample tmp;
  
  	blkg_rwstat_recursive_sum(pd->blkg, &blkcg_policy_bfq,
  			offsetof(struct bfq_group, stats.bytes), &tmp);
  
  	return __blkg_prfill_u64(sf, pd,
  		(tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE]) >> 9);
  }
  
  static int bfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
  {
  	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
  			  bfqg_prfill_sectors_recursive, &blkcg_policy_bfq, 0,
  			  false);
  	return 0;
  }
  
  static u64 bfqg_prfill_avg_queue_size(struct seq_file *sf,
  				      struct blkg_policy_data *pd, int off)
  {
  	struct bfq_group *bfqg = pd_to_bfqg(pd);
  	u64 samples = bfq_stat_read(&bfqg->stats.avg_queue_size_samples);
  	u64 v = 0;
  
  	if (samples) {
  		v = bfq_stat_read(&bfqg->stats.avg_queue_size_sum);
  		v = div64_u64(v, samples);
  	}
  	__blkg_prfill_u64(sf, pd, v);
  	return 0;
  }
  
  /* print avg_queue_size */
  static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v)
  {
  	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
  			  bfqg_prfill_avg_queue_size, &blkcg_policy_bfq,
  			  0, false);
  	return 0;
  }
  #endif /* CONFIG_BFQ_CGROUP_DEBUG */
  
  struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
  {
  	int ret;
  
  	ret = blkcg_activate_policy(bfqd->queue, &blkcg_policy_bfq);
  	if (ret)
  		return NULL;
  
  	return blkg_to_bfqg(bfqd->queue->root_blkg);
  }
  
  struct blkcg_policy blkcg_policy_bfq = {
  	.dfl_cftypes		= bfq_blkg_files,
  	.legacy_cftypes		= bfq_blkcg_legacy_files,
  
  	.cpd_alloc_fn		= bfq_cpd_alloc,
  	.cpd_init_fn		= bfq_cpd_init,
  	.cpd_bind_fn	        = bfq_cpd_init,
  	.cpd_free_fn		= bfq_cpd_free,
  
  	.pd_alloc_fn		= bfq_pd_alloc,
  	.pd_init_fn		= bfq_pd_init,
  	.pd_offline_fn		= bfq_pd_offline,
  	.pd_free_fn		= bfq_pd_free,
  	.pd_reset_stats_fn	= bfq_pd_reset_stats,
  };
  
  struct cftype bfq_blkcg_legacy_files[] = {
  	{
  		.name = "bfq.weight",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = bfq_io_show_weight_legacy,
  		.write_u64 = bfq_io_set_weight_legacy,
  	},
  	{
  		.name = "bfq.weight_device",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = bfq_io_show_weight,
  		.write = bfq_io_set_weight,
  	},
  
  	/* statistics, covers only the tasks in the bfqg */
  	{
  		.name = "bfq.io_service_bytes",
  		.private = offsetof(struct bfq_group, stats.bytes),
  		.seq_show = bfqg_print_rwstat,
  	},
  	{
  		.name = "bfq.io_serviced",
  		.private = offsetof(struct bfq_group, stats.ios),
  		.seq_show = bfqg_print_rwstat,
  	},
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  	{
  		.name = "bfq.time",
  		.private = offsetof(struct bfq_group, stats.time),
  		.seq_show = bfqg_print_stat,
  	},
  	{
  		.name = "bfq.sectors",
  		.seq_show = bfqg_print_stat_sectors,
  	},
  	{
  		.name = "bfq.io_service_time",
  		.private = offsetof(struct bfq_group, stats.service_time),
  		.seq_show = bfqg_print_rwstat,
  	},
  	{
  		.name = "bfq.io_wait_time",
  		.private = offsetof(struct bfq_group, stats.wait_time),
  		.seq_show = bfqg_print_rwstat,
  	},
  	{
  		.name = "bfq.io_merged",
  		.private = offsetof(struct bfq_group, stats.merged),
  		.seq_show = bfqg_print_rwstat,
  	},
  	{
  		.name = "bfq.io_queued",
  		.private = offsetof(struct bfq_group, stats.queued),
  		.seq_show = bfqg_print_rwstat,
  	},
  #endif /* CONFIG_BFQ_CGROUP_DEBUG */
  
  	/* the same statistics which cover the bfqg and its descendants */
  	{
  		.name = "bfq.io_service_bytes_recursive",
  		.private = offsetof(struct bfq_group, stats.bytes),
  		.seq_show = bfqg_print_rwstat_recursive,
  	},
  	{
  		.name = "bfq.io_serviced_recursive",
  		.private = offsetof(struct bfq_group, stats.ios),
  		.seq_show = bfqg_print_rwstat_recursive,
  	},
  #ifdef CONFIG_BFQ_CGROUP_DEBUG
  	{
  		.name = "bfq.time_recursive",
  		.private = offsetof(struct bfq_group, stats.time),
  		.seq_show = bfqg_print_stat_recursive,
  	},
  	{
  		.name = "bfq.sectors_recursive",
  		.seq_show = bfqg_print_stat_sectors_recursive,
  	},
  	{
  		.name = "bfq.io_service_time_recursive",
  		.private = offsetof(struct bfq_group, stats.service_time),
  		.seq_show = bfqg_print_rwstat_recursive,
  	},
  	{
  		.name = "bfq.io_wait_time_recursive",
  		.private = offsetof(struct bfq_group, stats.wait_time),
  		.seq_show = bfqg_print_rwstat_recursive,
  	},
  	{
  		.name = "bfq.io_merged_recursive",
  		.private = offsetof(struct bfq_group, stats.merged),
  		.seq_show = bfqg_print_rwstat_recursive,
  	},
  	{
  		.name = "bfq.io_queued_recursive",
  		.private = offsetof(struct bfq_group, stats.queued),
  		.seq_show = bfqg_print_rwstat_recursive,
  	},
  	{
  		.name = "bfq.avg_queue_size",
  		.seq_show = bfqg_print_avg_queue_size,
  	},
  	{
  		.name = "bfq.group_wait_time",
  		.private = offsetof(struct bfq_group, stats.group_wait_time),
  		.seq_show = bfqg_print_stat,
  	},
  	{
  		.name = "bfq.idle_time",
  		.private = offsetof(struct bfq_group, stats.idle_time),
  		.seq_show = bfqg_print_stat,
  	},
  	{
  		.name = "bfq.empty_time",
  		.private = offsetof(struct bfq_group, stats.empty_time),
  		.seq_show = bfqg_print_stat,
  	},
  	{
  		.name = "bfq.dequeue",
  		.private = offsetof(struct bfq_group, stats.dequeue),
  		.seq_show = bfqg_print_stat,
  	},
  #endif	/* CONFIG_BFQ_CGROUP_DEBUG */
  	{ }	/* terminate */
  };
  
  struct cftype bfq_blkg_files[] = {
  	{
  		.name = "bfq.weight",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = bfq_io_show_weight,
  		.write = bfq_io_set_weight,
  	},
  	{} /* terminate */
  };
  
  #else	/* CONFIG_BFQ_GROUP_IOSCHED */
  
  void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  		   struct bfq_group *bfqg) {}
  
  void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
  {
  	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
  
  	entity->weight = entity->new_weight;
  	entity->orig_weight = entity->new_weight;
  	if (bfqq) {
  		bfqq->ioprio = bfqq->new_ioprio;
  		bfqq->ioprio_class = bfqq->new_ioprio_class;
  	}
  	entity->sched_data = &bfqg->sched_data;
  }
  
  void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) {}
  
  void bfq_end_wr_async(struct bfq_data *bfqd)
  {
  	bfq_end_wr_async_queues(bfqd, bfqd->root_group);
  }
  
  struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg *blkcg)
  {
  	return bfqd->root_group;
  }
  
  struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
  {
  	return bfqq->bfqd->root_group;
  }
  
  void bfqg_and_blkg_get(struct bfq_group *bfqg) {}
  
  void bfqg_and_blkg_put(struct bfq_group *bfqg) {}
  
  struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
  {
  	struct bfq_group *bfqg;
  	int i;
  
  	bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node);
  	if (!bfqg)
  		return NULL;
  
  	for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
  		bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
  
  	return bfqg;
  }
  #endif	/* CONFIG_BFQ_GROUP_IOSCHED */
  