/*
   * Common Block IO controller cgroup interface
   *
   * Based on ideas and code from CFQ, CFS and BFQ:
   * 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) 2009 Vivek Goyal <vgoyal@redhat.com>
   * 	              Nauman Rafique <nauman@google.com>
   */
  #include <linux/ioprio.h>

  #include <linux/seq_file.h>
  #include <linux/kdev_t.h>

  #include <linux/module.h>

  #include <linux/err.h>

  #include <linux/blkdev.h>

  #include <linux/slab.h>

  #include "blk-cgroup.h"

  #include <linux/genhd.h>

  #define MAX_KEY_LEN 100

  static DEFINE_SPINLOCK(blkio_list_lock);
  static LIST_HEAD(blkio_list);

  struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };

  EXPORT_SYMBOL_GPL(blkio_root_cgroup);

  static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
  						  struct cgroup *);

  static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
  			      struct cgroup_taskset *);
  static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
  			   struct cgroup_taskset *);

  static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
  static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);

  /* for encoding cft->private value on file */
  #define BLKIOFILE_PRIVATE(x, val)	(((x) << 16) | (val))
  /* What policy owns the file, proportional or throttle */
  #define BLKIOFILE_POLICY(val)		(((val) >> 16) & 0xffff)
  #define BLKIOFILE_ATTR(val)		((val) & 0xffff)

  struct cgroup_subsys blkio_subsys = {
  	.name = "blkio",
  	.create = blkiocg_create,

  	.can_attach = blkiocg_can_attach,
  	.attach = blkiocg_attach,

  	.destroy = blkiocg_destroy,
  	.populate = blkiocg_populate,
  #ifdef CONFIG_BLK_CGROUP
  	/* note: blkio_subsys_id is otherwise defined in blk-cgroup.h */
  	.subsys_id = blkio_subsys_id,
  #endif
  	.use_id = 1,
  	.module = THIS_MODULE,
  };
  EXPORT_SYMBOL_GPL(blkio_subsys);

  static inline void blkio_policy_insert_node(struct blkio_cgroup *blkcg,
  					    struct blkio_policy_node *pn)
  {
  	list_add(&pn->node, &blkcg->policy_list);
  }

  static inline bool cftype_blkg_same_policy(struct cftype *cft,
  			struct blkio_group *blkg)
  {
  	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
  
  	if (blkg->plid == plid)
  		return 1;
  
  	return 0;
  }
  
  /* Determines if policy node matches cgroup file being accessed */
  static inline bool pn_matches_cftype(struct cftype *cft,
  			struct blkio_policy_node *pn)
  {
  	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
  	int fileid = BLKIOFILE_ATTR(cft->private);
  
  	return (plid == pn->plid && fileid == pn->fileid);
  }

  /* Must be called with blkcg->lock held */
  static inline void blkio_policy_delete_node(struct blkio_policy_node *pn)
  {
  	list_del(&pn->node);
  }
  
  /* Must be called with blkcg->lock held */
  static struct blkio_policy_node *

  blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev,
  		enum blkio_policy_id plid, int fileid)

  {
  	struct blkio_policy_node *pn;
  
  	list_for_each_entry(pn, &blkcg->policy_list, node) {

  		if (pn->dev == dev && pn->plid == plid && pn->fileid == fileid)

  			return pn;
  	}
  
  	return NULL;
  }

  struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
  {
  	return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
  			    struct blkio_cgroup, css);
  }

  EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);

  struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
  {
  	return container_of(task_subsys_state(tsk, blkio_subsys_id),
  			    struct blkio_cgroup, css);
  }
  EXPORT_SYMBOL_GPL(task_blkio_cgroup);

  static inline void
  blkio_update_group_weight(struct blkio_group *blkg, unsigned int weight)
  {
  	struct blkio_policy_type *blkiop;
  
  	list_for_each_entry(blkiop, &blkio_list, list) {
  		/* If this policy does not own the blkg, do not send updates */
  		if (blkiop->plid != blkg->plid)
  			continue;
  		if (blkiop->ops.blkio_update_group_weight_fn)

  			blkiop->ops.blkio_update_group_weight_fn(blkg->key,
  							blkg, weight);

  	}
  }

  static inline void blkio_update_group_bps(struct blkio_group *blkg, u64 bps,
  				int fileid)
  {
  	struct blkio_policy_type *blkiop;
  
  	list_for_each_entry(blkiop, &blkio_list, list) {
  
  		/* If this policy does not own the blkg, do not send updates */
  		if (blkiop->plid != blkg->plid)
  			continue;
  
  		if (fileid == BLKIO_THROTL_read_bps_device
  		    && blkiop->ops.blkio_update_group_read_bps_fn)

  			blkiop->ops.blkio_update_group_read_bps_fn(blkg->key,
  								blkg, bps);

  
  		if (fileid == BLKIO_THROTL_write_bps_device
  		    && blkiop->ops.blkio_update_group_write_bps_fn)

  			blkiop->ops.blkio_update_group_write_bps_fn(blkg->key,
  								blkg, bps);

  	}
  }

  static inline void blkio_update_group_iops(struct blkio_group *blkg,
  			unsigned int iops, int fileid)
  {
  	struct blkio_policy_type *blkiop;
  
  	list_for_each_entry(blkiop, &blkio_list, list) {
  
  		/* If this policy does not own the blkg, do not send updates */
  		if (blkiop->plid != blkg->plid)
  			continue;
  
  		if (fileid == BLKIO_THROTL_read_iops_device
  		    && blkiop->ops.blkio_update_group_read_iops_fn)

  			blkiop->ops.blkio_update_group_read_iops_fn(blkg->key,
  								blkg, iops);

  
  		if (fileid == BLKIO_THROTL_write_iops_device
  		    && blkiop->ops.blkio_update_group_write_iops_fn)

  			blkiop->ops.blkio_update_group_write_iops_fn(blkg->key,
  								blkg,iops);

  	}
  }

  /*
   * Add to the appropriate stat variable depending on the request type.
   * This should be called with the blkg->stats_lock held.
   */

  static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
  				bool sync)

  {

  	if (direction)
  		stat[BLKIO_STAT_WRITE] += add;

  	else

  		stat[BLKIO_STAT_READ] += add;
  	if (sync)
  		stat[BLKIO_STAT_SYNC] += add;

  	else

  		stat[BLKIO_STAT_ASYNC] += add;

  }

  /*
   * Decrements the appropriate stat variable if non-zero depending on the
   * request type. Panics on value being zero.
   * This should be called with the blkg->stats_lock held.
   */
  static void blkio_check_and_dec_stat(uint64_t *stat, bool direction, bool sync)
  {
  	if (direction) {
  		BUG_ON(stat[BLKIO_STAT_WRITE] == 0);
  		stat[BLKIO_STAT_WRITE]--;
  	} else {
  		BUG_ON(stat[BLKIO_STAT_READ] == 0);
  		stat[BLKIO_STAT_READ]--;
  	}
  	if (sync) {
  		BUG_ON(stat[BLKIO_STAT_SYNC] == 0);
  		stat[BLKIO_STAT_SYNC]--;
  	} else {
  		BUG_ON(stat[BLKIO_STAT_ASYNC] == 0);
  		stat[BLKIO_STAT_ASYNC]--;
  	}
  }
  
  #ifdef CONFIG_DEBUG_BLK_CGROUP

  /* This should be called with the blkg->stats_lock held. */
  static void blkio_set_start_group_wait_time(struct blkio_group *blkg,
  						struct blkio_group *curr_blkg)
  {
  	if (blkio_blkg_waiting(&blkg->stats))
  		return;
  	if (blkg == curr_blkg)
  		return;
  	blkg->stats.start_group_wait_time = sched_clock();
  	blkio_mark_blkg_waiting(&blkg->stats);
  }
  
  /* This should be called with the blkg->stats_lock held. */
  static void blkio_update_group_wait_time(struct blkio_group_stats *stats)
  {
  	unsigned long long now;
  
  	if (!blkio_blkg_waiting(stats))
  		return;
  
  	now = sched_clock();
  	if (time_after64(now, stats->start_group_wait_time))
  		stats->group_wait_time += now - stats->start_group_wait_time;
  	blkio_clear_blkg_waiting(stats);
  }
  
  /* This should be called with the blkg->stats_lock held. */
  static void blkio_end_empty_time(struct blkio_group_stats *stats)
  {
  	unsigned long long now;
  
  	if (!blkio_blkg_empty(stats))
  		return;
  
  	now = sched_clock();
  	if (time_after64(now, stats->start_empty_time))
  		stats->empty_time += now - stats->start_empty_time;
  	blkio_clear_blkg_empty(stats);
  }
  
  void blkiocg_update_set_idle_time_stats(struct blkio_group *blkg)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	BUG_ON(blkio_blkg_idling(&blkg->stats));
  	blkg->stats.start_idle_time = sched_clock();
  	blkio_mark_blkg_idling(&blkg->stats);
  	spin_unlock_irqrestore(&blkg->stats_lock, flags);
  }
  EXPORT_SYMBOL_GPL(blkiocg_update_set_idle_time_stats);
  
  void blkiocg_update_idle_time_stats(struct blkio_group *blkg)
  {
  	unsigned long flags;
  	unsigned long long now;
  	struct blkio_group_stats *stats;
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	stats = &blkg->stats;
  	if (blkio_blkg_idling(stats)) {
  		now = sched_clock();
  		if (time_after64(now, stats->start_idle_time))
  			stats->idle_time += now - stats->start_idle_time;
  		blkio_clear_blkg_idling(stats);
  	}
  	spin_unlock_irqrestore(&blkg->stats_lock, flags);
  }
  EXPORT_SYMBOL_GPL(blkiocg_update_idle_time_stats);

  void blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg)

  {
  	unsigned long flags;
  	struct blkio_group_stats *stats;
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	stats = &blkg->stats;
  	stats->avg_queue_size_sum +=
  			stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_READ] +
  			stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE];
  	stats->avg_queue_size_samples++;

  	blkio_update_group_wait_time(stats);

  	spin_unlock_irqrestore(&blkg->stats_lock, flags);
  }

  EXPORT_SYMBOL_GPL(blkiocg_update_avg_queue_size_stats);

  void blkiocg_set_start_empty_time(struct blkio_group *blkg)

  {
  	unsigned long flags;
  	struct blkio_group_stats *stats;
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	stats = &blkg->stats;
  
  	if (stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_READ] ||
  			stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE]) {
  		spin_unlock_irqrestore(&blkg->stats_lock, flags);
  		return;
  	}
  
  	/*

  	 * group is already marked empty. This can happen if cfqq 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(blkio_blkg_empty(stats)) {
  		spin_unlock_irqrestore(&blkg->stats_lock, flags);
  		return;
  	}

  	stats->start_empty_time = sched_clock();
  	blkio_mark_blkg_empty(stats);
  	spin_unlock_irqrestore(&blkg->stats_lock, flags);
  }
  EXPORT_SYMBOL_GPL(blkiocg_set_start_empty_time);

  void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
  			unsigned long dequeue)
  {
  	blkg->stats.dequeue += dequeue;
  }
  EXPORT_SYMBOL_GPL(blkiocg_update_dequeue_stats);

  #else
  static inline void blkio_set_start_group_wait_time(struct blkio_group *blkg,
  					struct blkio_group *curr_blkg) {}
  static inline void blkio_end_empty_time(struct blkio_group_stats *stats) {}

  #endif

  void blkiocg_update_io_add_stats(struct blkio_group *blkg,

  			struct blkio_group *curr_blkg, bool direction,
  			bool sync)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	blkio_add_stat(blkg->stats.stat_arr[BLKIO_STAT_QUEUED], 1, direction,
  			sync);

  	blkio_end_empty_time(&blkg->stats);
  	blkio_set_start_group_wait_time(blkg, curr_blkg);

  	spin_unlock_irqrestore(&blkg->stats_lock, flags);
  }

  EXPORT_SYMBOL_GPL(blkiocg_update_io_add_stats);

  void blkiocg_update_io_remove_stats(struct blkio_group *blkg,

  						bool direction, bool sync)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	blkio_check_and_dec_stat(blkg->stats.stat_arr[BLKIO_STAT_QUEUED],
  					direction, sync);
  	spin_unlock_irqrestore(&blkg->stats_lock, flags);
  }

  EXPORT_SYMBOL_GPL(blkiocg_update_io_remove_stats);

  void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time,
  				unsigned long unaccounted_time)

  {

  	unsigned long flags;
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	blkg->stats.time += time;

  #ifdef CONFIG_DEBUG_BLK_CGROUP

  	blkg->stats.unaccounted_time += unaccounted_time;

  #endif

  	spin_unlock_irqrestore(&blkg->stats_lock, flags);

  }

  EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);

  /*
   * should be called under rcu read lock or queue lock to make sure blkg pointer
   * is valid.
   */

  void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
  				uint64_t bytes, bool direction, bool sync)

  {

  	struct blkio_group_stats_cpu *stats_cpu;

  	unsigned long flags;
  
  	/*
  	 * Disabling interrupts to provide mutual exclusion between two
  	 * writes on same cpu. It probably is not needed for 64bit. Not
  	 * optimizing that case yet.
  	 */
  	local_irq_save(flags);

  	stats_cpu = this_cpu_ptr(blkg->stats_cpu);

  	u64_stats_update_begin(&stats_cpu->syncp);

  	stats_cpu->sectors += bytes >> 9;
  	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICED],
  			1, direction, sync);
  	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICE_BYTES],
  			bytes, direction, sync);

  	u64_stats_update_end(&stats_cpu->syncp);
  	local_irq_restore(flags);

  }

  EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);

  void blkiocg_update_completion_stats(struct blkio_group *blkg,
  	uint64_t start_time, uint64_t io_start_time, bool direction, bool sync)

  {
  	struct blkio_group_stats *stats;
  	unsigned long flags;
  	unsigned long long now = sched_clock();
  
  	spin_lock_irqsave(&blkg->stats_lock, flags);
  	stats = &blkg->stats;

  	if (time_after64(now, io_start_time))
  		blkio_add_stat(stats->stat_arr[BLKIO_STAT_SERVICE_TIME],
  				now - io_start_time, direction, sync);
  	if (time_after64(io_start_time, start_time))
  		blkio_add_stat(stats->stat_arr[BLKIO_STAT_WAIT_TIME],
  				io_start_time - start_time, direction, sync);

  	spin_unlock_irqrestore(&blkg->stats_lock, flags);
  }

  EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);

  /*  Merged stats are per cpu.  */

  void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
  					bool sync)
  {

  	struct blkio_group_stats_cpu *stats_cpu;

  	unsigned long flags;

  	/*
  	 * Disabling interrupts to provide mutual exclusion between two
  	 * writes on same cpu. It probably is not needed for 64bit. Not
  	 * optimizing that case yet.
  	 */
  	local_irq_save(flags);
  
  	stats_cpu = this_cpu_ptr(blkg->stats_cpu);
  
  	u64_stats_update_begin(&stats_cpu->syncp);
  	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_MERGED], 1,
  				direction, sync);
  	u64_stats_update_end(&stats_cpu->syncp);
  	local_irq_restore(flags);

  }
  EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);

  /*
   * This function allocates the per cpu stats for blkio_group. Should be called
   * from sleepable context as alloc_per_cpu() requires that.
   */
  int blkio_alloc_blkg_stats(struct blkio_group *blkg)
  {
  	/* Allocate memory for per cpu stats */
  	blkg->stats_cpu = alloc_percpu(struct blkio_group_stats_cpu);
  	if (!blkg->stats_cpu)
  		return -ENOMEM;
  	return 0;
  }
  EXPORT_SYMBOL_GPL(blkio_alloc_blkg_stats);

  void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,

  		struct blkio_group *blkg, void *key, dev_t dev,
  		enum blkio_policy_id plid)

  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&blkcg->lock, flags);

  	spin_lock_init(&blkg->stats_lock);

  	rcu_assign_pointer(blkg->key, key);

  	blkg->blkcg_id = css_id(&blkcg->css);

  	hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);

  	blkg->plid = plid;

  	spin_unlock_irqrestore(&blkcg->lock, flags);

  	/* Need to take css reference ? */
  	cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));

  	blkg->dev = dev;

  }

  EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);

  static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
  {
  	hlist_del_init_rcu(&blkg->blkcg_node);
  	blkg->blkcg_id = 0;
  }
  
  /*
   * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
   * indicating that blk_group was unhashed by the time we got to it.
   */

  int blkiocg_del_blkio_group(struct blkio_group *blkg)
  {

  	struct blkio_cgroup *blkcg;
  	unsigned long flags;
  	struct cgroup_subsys_state *css;
  	int ret = 1;
  
  	rcu_read_lock();
  	css = css_lookup(&blkio_subsys, blkg->blkcg_id);

  	if (css) {
  		blkcg = container_of(css, struct blkio_cgroup, css);
  		spin_lock_irqsave(&blkcg->lock, flags);
  		if (!hlist_unhashed(&blkg->blkcg_node)) {
  			__blkiocg_del_blkio_group(blkg);
  			ret = 0;
  		}
  		spin_unlock_irqrestore(&blkcg->lock, flags);

  	}

  	rcu_read_unlock();
  	return ret;

  }

  EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);

  
  /* called under rcu_read_lock(). */
  struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
  {
  	struct blkio_group *blkg;
  	struct hlist_node *n;
  	void *__key;
  
  	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
  		__key = blkg->key;
  		if (__key == key)
  			return blkg;
  	}
  
  	return NULL;
  }

  EXPORT_SYMBOL_GPL(blkiocg_lookup_group);

  static void blkio_reset_stats_cpu(struct blkio_group *blkg)
  {
  	struct blkio_group_stats_cpu *stats_cpu;
  	int i, j, k;
  	/*
  	 * Note: On 64 bit arch this should not be an issue. This has the
  	 * possibility of returning some inconsistent value on 32bit arch
  	 * as 64bit update on 32bit is non atomic. Taking care of this
  	 * corner case makes code very complicated, like sending IPIs to
  	 * cpus, taking care of stats of offline cpus etc.
  	 *
  	 * reset stats is anyway more of a debug feature and this sounds a
  	 * corner case. So I am not complicating the code yet until and
  	 * unless this becomes a real issue.
  	 */
  	for_each_possible_cpu(i) {
  		stats_cpu = per_cpu_ptr(blkg->stats_cpu, i);
  		stats_cpu->sectors = 0;
  		for(j = 0; j < BLKIO_STAT_CPU_NR; j++)
  			for (k = 0; k < BLKIO_STAT_TOTAL; k++)
  				stats_cpu->stat_arr_cpu[j][k] = 0;
  	}
  }

  static int

  blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)

  {
  	struct blkio_cgroup *blkcg;
  	struct blkio_group *blkg;

  	struct blkio_group_stats *stats;

  	struct hlist_node *n;

  	uint64_t queued[BLKIO_STAT_TOTAL];
  	int i;

  #ifdef CONFIG_DEBUG_BLK_CGROUP
  	bool idling, waiting, empty;
  	unsigned long long now = sched_clock();
  #endif

  
  	blkcg = cgroup_to_blkio_cgroup(cgroup);
  	spin_lock_irq(&blkcg->lock);
  	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
  		spin_lock(&blkg->stats_lock);

  		stats = &blkg->stats;
  #ifdef CONFIG_DEBUG_BLK_CGROUP
  		idling = blkio_blkg_idling(stats);
  		waiting = blkio_blkg_waiting(stats);
  		empty = blkio_blkg_empty(stats);
  #endif

  		for (i = 0; i < BLKIO_STAT_TOTAL; i++)

  			queued[i] = stats->stat_arr[BLKIO_STAT_QUEUED][i];
  		memset(stats, 0, sizeof(struct blkio_group_stats));

  		for (i = 0; i < BLKIO_STAT_TOTAL; i++)

  			stats->stat_arr[BLKIO_STAT_QUEUED][i] = queued[i];
  #ifdef CONFIG_DEBUG_BLK_CGROUP
  		if (idling) {
  			blkio_mark_blkg_idling(stats);
  			stats->start_idle_time = now;
  		}
  		if (waiting) {
  			blkio_mark_blkg_waiting(stats);
  			stats->start_group_wait_time = now;
  		}
  		if (empty) {
  			blkio_mark_blkg_empty(stats);
  			stats->start_empty_time = now;
  		}
  #endif

  		spin_unlock(&blkg->stats_lock);

  
  		/* Reset Per cpu stats which don't take blkg->stats_lock */
  		blkio_reset_stats_cpu(blkg);

  	}

  	spin_unlock_irq(&blkcg->lock);
  	return 0;
  }

  static void blkio_get_key_name(enum stat_sub_type type, dev_t dev, char *str,
  				int chars_left, bool diskname_only)

  {

  	snprintf(str, chars_left, "%d:%d", MAJOR(dev), MINOR(dev));

  	chars_left -= strlen(str);
  	if (chars_left <= 0) {
  		printk(KERN_WARNING
  			"Possibly incorrect cgroup stat display format");
  		return;
  	}

  	if (diskname_only)
  		return;

  	switch (type) {

  	case BLKIO_STAT_READ:

  		strlcat(str, " Read", chars_left);
  		break;

  	case BLKIO_STAT_WRITE:

  		strlcat(str, " Write", chars_left);
  		break;

  	case BLKIO_STAT_SYNC:

  		strlcat(str, " Sync", chars_left);
  		break;

  	case BLKIO_STAT_ASYNC:

  		strlcat(str, " Async", chars_left);
  		break;

  	case BLKIO_STAT_TOTAL:

  		strlcat(str, " Total", chars_left);
  		break;
  	default:
  		strlcat(str, " Invalid", chars_left);
  	}
  }

  static uint64_t blkio_fill_stat(char *str, int chars_left, uint64_t val,
  				struct cgroup_map_cb *cb, dev_t dev)
  {
  	blkio_get_key_name(0, dev, str, chars_left, true);
  	cb->fill(cb, str, val);
  	return val;
  }

  
  static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg,
  			enum stat_type_cpu type, enum stat_sub_type sub_type)
  {
  	int cpu;
  	struct blkio_group_stats_cpu *stats_cpu;

  	u64 val = 0, tval;

  
  	for_each_possible_cpu(cpu) {

  		unsigned int start;

  		stats_cpu  = per_cpu_ptr(blkg->stats_cpu, cpu);

  		do {
  			start = u64_stats_fetch_begin(&stats_cpu->syncp);
  			if (type == BLKIO_STAT_CPU_SECTORS)
  				tval = stats_cpu->sectors;
  			else
  				tval = stats_cpu->stat_arr_cpu[type][sub_type];
  		} while(u64_stats_fetch_retry(&stats_cpu->syncp, start));
  
  		val += tval;

  	}
  
  	return val;
  }
  
  static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg,
  		struct cgroup_map_cb *cb, dev_t dev, enum stat_type_cpu type)
  {
  	uint64_t disk_total, val;
  	char key_str[MAX_KEY_LEN];
  	enum stat_sub_type sub_type;
  
  	if (type == BLKIO_STAT_CPU_SECTORS) {
  		val = blkio_read_stat_cpu(blkg, type, 0);
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1, val, cb, dev);
  	}
  
  	for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
  			sub_type++) {
  		blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
  		val = blkio_read_stat_cpu(blkg, type, sub_type);
  		cb->fill(cb, key_str, val);
  	}
  
  	disk_total = blkio_read_stat_cpu(blkg, type, BLKIO_STAT_READ) +
  			blkio_read_stat_cpu(blkg, type, BLKIO_STAT_WRITE);
  
  	blkio_get_key_name(BLKIO_STAT_TOTAL, dev, key_str, MAX_KEY_LEN, false);
  	cb->fill(cb, key_str, disk_total);
  	return disk_total;
  }

  /* This should be called with blkg->stats_lock held */
  static uint64_t blkio_get_stat(struct blkio_group *blkg,
  		struct cgroup_map_cb *cb, dev_t dev, enum stat_type type)

  {
  	uint64_t disk_total;
  	char key_str[MAX_KEY_LEN];

  	enum stat_sub_type sub_type;
  
  	if (type == BLKIO_STAT_TIME)
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
  					blkg->stats.time, cb, dev);

  #ifdef CONFIG_DEBUG_BLK_CGROUP

  	if (type == BLKIO_STAT_UNACCOUNTED_TIME)
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
  					blkg->stats.unaccounted_time, cb, dev);

  	if (type == BLKIO_STAT_AVG_QUEUE_SIZE) {
  		uint64_t sum = blkg->stats.avg_queue_size_sum;
  		uint64_t samples = blkg->stats.avg_queue_size_samples;
  		if (samples)
  			do_div(sum, samples);
  		else
  			sum = 0;
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1, sum, cb, dev);
  	}

  	if (type == BLKIO_STAT_GROUP_WAIT_TIME)
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
  					blkg->stats.group_wait_time, cb, dev);
  	if (type == BLKIO_STAT_IDLE_TIME)
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
  					blkg->stats.idle_time, cb, dev);
  	if (type == BLKIO_STAT_EMPTY_TIME)
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
  					blkg->stats.empty_time, cb, dev);

  	if (type == BLKIO_STAT_DEQUEUE)
  		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
  					blkg->stats.dequeue, cb, dev);
  #endif

  	for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
  			sub_type++) {
  		blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
  		cb->fill(cb, key_str, blkg->stats.stat_arr[type][sub_type]);

  	}

  	disk_total = blkg->stats.stat_arr[type][BLKIO_STAT_READ] +
  			blkg->stats.stat_arr[type][BLKIO_STAT_WRITE];
  	blkio_get_key_name(BLKIO_STAT_TOTAL, dev, key_str, MAX_KEY_LEN, false);

  	cb->fill(cb, key_str, disk_total);
  	return disk_total;
  }

  static int blkio_policy_parse_and_set(char *buf,

  	struct blkio_policy_node *newpn, enum blkio_policy_id plid, int fileid)

  {

  	struct gendisk *disk = NULL;

  	char *s[4], *p, *major_s = NULL, *minor_s = NULL;

  	unsigned long major, minor;

  	int i = 0, ret = -EINVAL;
  	int part;

  	dev_t dev;

  	u64 temp;

  
  	memset(s, 0, sizeof(s));
  
  	while ((p = strsep(&buf, " ")) != NULL) {
  		if (!*p)
  			continue;
  
  		s[i++] = p;
  
  		/* Prevent from inputing too many things */
  		if (i == 3)
  			break;
  	}
  
  	if (i != 2)

  		goto out;

  
  	p = strsep(&s[0], ":");
  	if (p != NULL)
  		major_s = p;
  	else

  		goto out;

  
  	minor_s = s[0];
  	if (!minor_s)

  		goto out;

  	if (strict_strtoul(major_s, 10, &major))
  		goto out;

  	if (strict_strtoul(minor_s, 10, &minor))
  		goto out;

  
  	dev = MKDEV(major, minor);

  	if (strict_strtoull(s[1], 10, &temp))
  		goto out;

  	/* For rule removal, do not check for device presence. */
  	if (temp) {

  		disk = get_gendisk(dev, &part);
  		if (!disk || part) {
  			ret = -ENODEV;
  			goto out;
  		}

  	}

  	newpn->dev = dev;

  	switch (plid) {
  	case BLKIO_POLICY_PROP:

  		if ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
  		     temp > BLKIO_WEIGHT_MAX)

  			goto out;

  		newpn->plid = plid;
  		newpn->fileid = fileid;

  		newpn->val.weight = temp;
  		break;
  	case BLKIO_POLICY_THROTL:

  		switch(fileid) {
  		case BLKIO_THROTL_read_bps_device:
  		case BLKIO_THROTL_write_bps_device:

  			newpn->plid = plid;
  			newpn->fileid = fileid;

  			newpn->val.bps = temp;

  			break;
  		case BLKIO_THROTL_read_iops_device:
  		case BLKIO_THROTL_write_iops_device:

  			if (temp > THROTL_IOPS_MAX)

  				goto out;

  			newpn->plid = plid;
  			newpn->fileid = fileid;

  			newpn->val.iops = (unsigned int)temp;

  			break;
  		}

  		break;
  	default:
  		BUG();
  	}

  	ret = 0;
  out:
  	put_disk(disk);
  	return ret;

  }
  
  unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,
  			      dev_t dev)
  {
  	struct blkio_policy_node *pn;

  	unsigned long flags;
  	unsigned int weight;
  
  	spin_lock_irqsave(&blkcg->lock, flags);

  	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_PROP,
  				BLKIO_PROP_weight_device);

  	if (pn)

  		weight = pn->val.weight;

  	else

  		weight = blkcg->weight;
  
  	spin_unlock_irqrestore(&blkcg->lock, flags);
  
  	return weight;

  }
  EXPORT_SYMBOL_GPL(blkcg_get_weight);

  uint64_t blkcg_get_read_bps(struct blkio_cgroup *blkcg, dev_t dev)
  {
  	struct blkio_policy_node *pn;

  	unsigned long flags;
  	uint64_t bps = -1;

  	spin_lock_irqsave(&blkcg->lock, flags);

  	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_read_bps_device);
  	if (pn)

  		bps = pn->val.bps;
  	spin_unlock_irqrestore(&blkcg->lock, flags);
  
  	return bps;

  }
  
  uint64_t blkcg_get_write_bps(struct blkio_cgroup *blkcg, dev_t dev)
  {
  	struct blkio_policy_node *pn;

  	unsigned long flags;
  	uint64_t bps = -1;
  
  	spin_lock_irqsave(&blkcg->lock, flags);

  	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_write_bps_device);
  	if (pn)

  		bps = pn->val.bps;
  	spin_unlock_irqrestore(&blkcg->lock, flags);
  
  	return bps;

  }

  unsigned int blkcg_get_read_iops(struct blkio_cgroup *blkcg, dev_t dev)
  {
  	struct blkio_policy_node *pn;

  	unsigned long flags;
  	unsigned int iops = -1;

  	spin_lock_irqsave(&blkcg->lock, flags);

  	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_read_iops_device);
  	if (pn)

  		iops = pn->val.iops;
  	spin_unlock_irqrestore(&blkcg->lock, flags);
  
  	return iops;

  }
  
  unsigned int blkcg_get_write_iops(struct blkio_cgroup *blkcg, dev_t dev)
  {
  	struct blkio_policy_node *pn;

  	unsigned long flags;
  	unsigned int iops = -1;
  
  	spin_lock_irqsave(&blkcg->lock, flags);

  	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_write_iops_device);
  	if (pn)

  		iops = pn->val.iops;
  	spin_unlock_irqrestore(&blkcg->lock, flags);
  
  	return iops;

  }

  /* Checks whether user asked for deleting a policy rule */
  static bool blkio_delete_rule_command(struct blkio_policy_node *pn)
  {
  	switch(pn->plid) {
  	case BLKIO_POLICY_PROP:

  		if (pn->val.weight == 0)
  			return 1;
  		break;
  	case BLKIO_POLICY_THROTL:

  		switch(pn->fileid) {
  		case BLKIO_THROTL_read_bps_device:
  		case BLKIO_THROTL_write_bps_device:
  			if (pn->val.bps == 0)
  				return 1;
  			break;
  		case BLKIO_THROTL_read_iops_device:
  		case BLKIO_THROTL_write_iops_device:
  			if (pn->val.iops == 0)
  				return 1;
  		}

  		break;
  	default:
  		BUG();
  	}
  
  	return 0;
  }
  
  static void blkio_update_policy_rule(struct blkio_policy_node *oldpn,
  					struct blkio_policy_node *newpn)
  {
  	switch(oldpn->plid) {
  	case BLKIO_POLICY_PROP:

  		oldpn->val.weight = newpn->val.weight;
  		break;
  	case BLKIO_POLICY_THROTL:

  		switch(newpn->fileid) {
  		case BLKIO_THROTL_read_bps_device:
  		case BLKIO_THROTL_write_bps_device:
  			oldpn->val.bps = newpn->val.bps;
  			break;
  		case BLKIO_THROTL_read_iops_device:
  		case BLKIO_THROTL_write_iops_device:
  			oldpn->val.iops = newpn->val.iops;
  		}

  		break;
  	default:
  		BUG();
  	}
  }
  
  /*

   * Some rules/values in blkg have changed. Propagate those to respective

   * policies.
   */
  static void blkio_update_blkg_policy(struct blkio_cgroup *blkcg,
  		struct blkio_group *blkg, struct blkio_policy_node *pn)
  {

  	unsigned int weight, iops;

  	u64 bps;

  
  	switch(pn->plid) {
  	case BLKIO_POLICY_PROP:

  		weight = pn->val.weight ? pn->val.weight :

  				blkcg->weight;
  		blkio_update_group_weight(blkg, weight);
  		break;

  	case BLKIO_POLICY_THROTL:
  		switch(pn->fileid) {
  		case BLKIO_THROTL_read_bps_device:
  		case BLKIO_THROTL_write_bps_device:
  			bps = pn->val.bps ? pn->val.bps : (-1);
  			blkio_update_group_bps(blkg, bps, pn->fileid);
  			break;

  		case BLKIO_THROTL_read_iops_device:
  		case BLKIO_THROTL_write_iops_device:
  			iops = pn->val.iops ? pn->val.iops : (-1);
  			blkio_update_group_iops(blkg, iops, pn->fileid);
  			break;

  		}
  		break;

  	default:
  		BUG();
  	}
  }
  
  /*

   * A policy node rule has been updated. Propagate this update to all the

   * block groups which might be affected by this update.
   */
  static void blkio_update_policy_node_blkg(struct blkio_cgroup *blkcg,
  				struct blkio_policy_node *pn)
  {
  	struct blkio_group *blkg;
  	struct hlist_node *n;
  
  	spin_lock(&blkio_list_lock);
  	spin_lock_irq(&blkcg->lock);

  	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
  		if (pn->dev != blkg->dev || pn->plid != blkg->plid)
  			continue;
  		blkio_update_blkg_policy(blkcg, blkg, pn);
  	}
  
  	spin_unlock_irq(&blkcg->lock);
  	spin_unlock(&blkio_list_lock);
  }

  static int blkiocg_file_write(struct cgroup *cgrp, struct cftype *cft,
   				       const char *buffer)

  {
  	int ret = 0;
  	char *buf;
  	struct blkio_policy_node *newpn, *pn;
  	struct blkio_cgroup *blkcg;

  	int keep_newpn = 0;

  	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
  	int fileid = BLKIOFILE_ATTR(cft->private);

  
  	buf = kstrdup(buffer, GFP_KERNEL);
  	if (!buf)
  		return -ENOMEM;
  
  	newpn = kzalloc(sizeof(*newpn), GFP_KERNEL);
  	if (!newpn) {
  		ret = -ENOMEM;
  		goto free_buf;
  	}

  	ret = blkio_policy_parse_and_set(buf, newpn, plid, fileid);

  	if (ret)
  		goto free_newpn;
  
  	blkcg = cgroup_to_blkio_cgroup(cgrp);
  
  	spin_lock_irq(&blkcg->lock);

  	pn = blkio_policy_search_node(blkcg, newpn->dev, plid, fileid);

  	if (!pn) {

  		if (!blkio_delete_rule_command(newpn)) {

  			blkio_policy_insert_node(blkcg, newpn);
  			keep_newpn = 1;
  		}
  		spin_unlock_irq(&blkcg->lock);
  		goto update_io_group;
  	}

  	if (blkio_delete_rule_command(newpn)) {

  		blkio_policy_delete_node(pn);

  		kfree(pn);

  		spin_unlock_irq(&blkcg->lock);
  		goto update_io_group;
  	}
  	spin_unlock_irq(&blkcg->lock);

  	blkio_update_policy_rule(pn, newpn);

  
  update_io_group:

  	blkio_update_policy_node_blkg(blkcg, newpn);

  
  free_newpn:
  	if (!keep_newpn)
  		kfree(newpn);
  free_buf:
  	kfree(buf);
  	return ret;
  }

  static void
  blkio_print_policy_node(struct seq_file *m, struct blkio_policy_node *pn)

  {

  	switch(pn->plid) {
  		case BLKIO_POLICY_PROP:
  			if (pn->fileid == BLKIO_PROP_weight_device)
  				seq_printf(m, "%u:%u\t%u
  ", MAJOR(pn->dev),

  					MINOR(pn->dev), pn->val.weight);
  			break;
  		case BLKIO_POLICY_THROTL:

  			switch(pn->fileid) {
  			case BLKIO_THROTL_read_bps_device:
  			case BLKIO_THROTL_write_bps_device:

  				seq_printf(m, "%u:%u\t%llu
  ", MAJOR(pn->dev),
  					MINOR(pn->dev), pn->val.bps);

  				break;
  			case BLKIO_THROTL_read_iops_device:
  			case BLKIO_THROTL_write_iops_device:
  				seq_printf(m, "%u:%u\t%u
  ", MAJOR(pn->dev),
  					MINOR(pn->dev), pn->val.iops);
  				break;
  			}

  			break;
  		default:
  			BUG();
  	}
  }

  /* cgroup files which read their data from policy nodes end up here */
  static void blkio_read_policy_node_files(struct cftype *cft,
  			struct blkio_cgroup *blkcg, struct seq_file *m)

  {

  	struct blkio_policy_node *pn;

  	if (!list_empty(&blkcg->policy_list)) {
  		spin_lock_irq(&blkcg->lock);
  		list_for_each_entry(pn, &blkcg->policy_list, node) {

  			if (!pn_matches_cftype(cft, pn))
  				continue;
  			blkio_print_policy_node(m, pn);

  		}
  		spin_unlock_irq(&blkcg->lock);

  	}

  }
  
  static int blkiocg_file_read(struct cgroup *cgrp, struct cftype *cft,
  				struct seq_file *m)
  {
  	struct blkio_cgroup *blkcg;
  	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
  	int name = BLKIOFILE_ATTR(cft->private);
  
  	blkcg = cgroup_to_blkio_cgroup(cgrp);
  
  	switch(plid) {
  	case BLKIO_POLICY_PROP:
  		switch(name) {
  		case BLKIO_PROP_weight_device:
  			blkio_read_policy_node_files(cft, blkcg, m);
  			return 0;
  		default:
  			BUG();
  		}
  		break;

  	case BLKIO_POLICY_THROTL:
  		switch(name){
  		case BLKIO_THROTL_read_bps_device:
  		case BLKIO_THROTL_write_bps_device:

  		case BLKIO_THROTL_read_iops_device:
  		case BLKIO_THROTL_write_iops_device:

  			blkio_read_policy_node_files(cft, blkcg, m);
  			return 0;
  		default:
  			BUG();
  		}
  		break;

  	default:
  		BUG();
  	}
  
  	return 0;
  }
  
  static int blkio_read_blkg_stats(struct blkio_cgroup *blkcg,

  		struct cftype *cft, struct cgroup_map_cb *cb,
  		enum stat_type type, bool show_total, bool pcpu)

  {
  	struct blkio_group *blkg;
  	struct hlist_node *n;
  	uint64_t cgroup_total = 0;
  
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
  		if (blkg->dev) {
  			if (!cftype_blkg_same_policy(cft, blkg))
  				continue;

  			if (pcpu)
  				cgroup_total += blkio_get_stat_cpu(blkg, cb,
  						blkg->dev, type);
  			else {
  				spin_lock_irq(&blkg->stats_lock);
  				cgroup_total += blkio_get_stat(blkg, cb,
  						blkg->dev, type);
  				spin_unlock_irq(&blkg->stats_lock);
  			}

  		}
  	}
  	if (show_total)
  		cb->fill(cb, "Total", cgroup_total);
  	rcu_read_unlock();
  	return 0;
  }
  
  /* All map kind of cgroup file get serviced by this function */
  static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
  				struct cgroup_map_cb *cb)
  {
  	struct blkio_cgroup *blkcg;
  	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
  	int name = BLKIOFILE_ATTR(cft->private);
  
  	blkcg = cgroup_to_blkio_cgroup(cgrp);
  
  	switch(plid) {
  	case BLKIO_POLICY_PROP:
  		switch(name) {
  		case BLKIO_PROP_time:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_TIME, 0, 0);

  		case BLKIO_PROP_sectors:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_CPU_SECTORS, 0, 1);

  		case BLKIO_PROP_io_service_bytes:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  					BLKIO_STAT_CPU_SERVICE_BYTES, 1, 1);

  		case BLKIO_PROP_io_serviced:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_CPU_SERVICED, 1, 1);

  		case BLKIO_PROP_io_service_time:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_SERVICE_TIME, 1, 0);

  		case BLKIO_PROP_io_wait_time:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_WAIT_TIME, 1, 0);

  		case BLKIO_PROP_io_merged:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_CPU_MERGED, 1, 1);

  		case BLKIO_PROP_io_queued:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_QUEUED, 1, 0);

  #ifdef CONFIG_DEBUG_BLK_CGROUP

  		case BLKIO_PROP_unaccounted_time:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  					BLKIO_STAT_UNACCOUNTED_TIME, 0, 0);

  		case BLKIO_PROP_dequeue:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_DEQUEUE, 0, 0);

  		case BLKIO_PROP_avg_queue_size:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  					BLKIO_STAT_AVG_QUEUE_SIZE, 0, 0);

  		case BLKIO_PROP_group_wait_time:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  					BLKIO_STAT_GROUP_WAIT_TIME, 0, 0);

  		case BLKIO_PROP_idle_time:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_IDLE_TIME, 0, 0);

  		case BLKIO_PROP_empty_time:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_EMPTY_TIME, 0, 0);

  #endif
  		default:
  			BUG();
  		}
  		break;

  	case BLKIO_POLICY_THROTL:
  		switch(name){
  		case BLKIO_THROTL_io_service_bytes:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_CPU_SERVICE_BYTES, 1, 1);

  		case BLKIO_THROTL_io_serviced:
  			return blkio_read_blkg_stats(blkcg, cft, cb,

  						BLKIO_STAT_CPU_SERVICED, 1, 1);

  		default:
  			BUG();
  		}
  		break;

  	default:
  		BUG();
  	}
  
  	return 0;
  }
  
  static int blkio_weight_write(struct blkio_cgroup *blkcg, u64 val)
  {
  	struct blkio_group *blkg;
  	struct hlist_node *n;
  	struct blkio_policy_node *pn;
  
  	if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
  		return -EINVAL;
  
  	spin_lock(&blkio_list_lock);
  	spin_lock_irq(&blkcg->lock);
  	blkcg->weight = (unsigned int)val;
  
  	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
  		pn = blkio_policy_search_node(blkcg, blkg->dev,
  				BLKIO_POLICY_PROP, BLKIO_PROP_weight_device);
  		if (pn)
  			continue;
  
  		blkio_update_group_weight(blkg, blkcg->weight);
  	}
  	spin_unlock_irq(&blkcg->lock);
  	spin_unlock(&blkio_list_lock);
  	return 0;
  }
  
  static u64 blkiocg_file_read_u64 (struct cgroup *cgrp, struct cftype *cft) {
  	struct blkio_cgroup *blkcg;
  	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
  	int name = BLKIOFILE_ATTR(cft->private);
  
  	blkcg = cgroup_to_blkio_cgroup(cgrp);
  
  	switch(plid) {
  	case BLKIO_POLICY_PROP:
  		switch(name) {
  		case BLKIO_PROP_weight:
  			return (u64)blkcg->weight;
  		}
  		break;
  	default:
  		BUG();
  	}
  	return 0;
  }
  
  static int
  blkiocg_file_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
  {
  	struct blkio_cgroup *blkcg;
  	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
  	int name = BLKIOFILE_ATTR(cft->private);
  
  	blkcg = cgroup_to_blkio_cgroup(cgrp);
  
  	switch(plid) {
  	case BLKIO_POLICY_PROP:
  		switch(name) {
  		case BLKIO_PROP_weight:
  			return blkio_weight_write(blkcg, val);
  		}
  		break;
  	default:
  		BUG();
  	}

  	return 0;
  }

  struct cftype blkio_files[] = {
  	{

  		.name = "weight_device",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_weight_device),
  		.read_seq_string = blkiocg_file_read,
  		.write_string = blkiocg_file_write,

  		.max_write_len = 256,
  	},
  	{

  		.name = "weight",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_weight),
  		.read_u64 = blkiocg_file_read_u64,
  		.write_u64 = blkiocg_file_write_u64,

  	},

  	{
  		.name = "time",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_time),
  		.read_map = blkiocg_file_read_map,

  	},
  	{
  		.name = "sectors",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_sectors),
  		.read_map = blkiocg_file_read_map,

  	},
  	{
  		.name = "io_service_bytes",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_io_service_bytes),
  		.read_map = blkiocg_file_read_map,

  	},
  	{
  		.name = "io_serviced",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_io_serviced),
  		.read_map = blkiocg_file_read_map,

  	},
  	{
  		.name = "io_service_time",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_io_service_time),
  		.read_map = blkiocg_file_read_map,

  	},
  	{
  		.name = "io_wait_time",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_io_wait_time),
  		.read_map = blkiocg_file_read_map,

  	},
  	{

  		.name = "io_merged",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_io_merged),
  		.read_map = blkiocg_file_read_map,

  	},
  	{

  		.name = "io_queued",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_io_queued),
  		.read_map = blkiocg_file_read_map,

  	},
  	{

  		.name = "reset_stats",
  		.write_u64 = blkiocg_reset_stats,

  	},

  #ifdef CONFIG_BLK_DEV_THROTTLING
  	{
  		.name = "throttle.read_bps_device",
  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_read_bps_device),
  		.read_seq_string = blkiocg_file_read,
  		.write_string = blkiocg_file_write,
  		.max_write_len = 256,
  	},
  
  	{
  		.name = "throttle.write_bps_device",
  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_write_bps_device),
  		.read_seq_string = blkiocg_file_read,
  		.write_string = blkiocg_file_write,
  		.max_write_len = 256,
  	},
  
  	{
  		.name = "throttle.read_iops_device",
  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_read_iops_device),
  		.read_seq_string = blkiocg_file_read,
  		.write_string = blkiocg_file_write,
  		.max_write_len = 256,
  	},
  
  	{
  		.name = "throttle.write_iops_device",
  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_write_iops_device),
  		.read_seq_string = blkiocg_file_read,
  		.write_string = blkiocg_file_write,
  		.max_write_len = 256,
  	},
  	{
  		.name = "throttle.io_service_bytes",
  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_io_service_bytes),
  		.read_map = blkiocg_file_read_map,
  	},
  	{
  		.name = "throttle.io_serviced",
  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
  				BLKIO_THROTL_io_serviced),
  		.read_map = blkiocg_file_read_map,
  	},
  #endif /* CONFIG_BLK_DEV_THROTTLING */

  #ifdef CONFIG_DEBUG_BLK_CGROUP

  	{
  		.name = "avg_queue_size",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_avg_queue_size),
  		.read_map = blkiocg_file_read_map,

  	},
  	{

  		.name = "group_wait_time",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_group_wait_time),
  		.read_map = blkiocg_file_read_map,

  	},
  	{
  		.name = "idle_time",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_idle_time),
  		.read_map = blkiocg_file_read_map,

  	},
  	{
  		.name = "empty_time",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_empty_time),
  		.read_map = blkiocg_file_read_map,

  	},
  	{

  		.name = "dequeue",

  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_dequeue),
  		.read_map = blkiocg_file_read_map,

  	},

  	{
  		.name = "unaccounted_time",
  		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
  				BLKIO_PROP_unaccounted_time),
  		.read_map = blkiocg_file_read_map,
  	},

  #endif

  };
  
  static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
  {
  	return cgroup_add_files(cgroup, subsys, blkio_files,
  				ARRAY_SIZE(blkio_files));
  }
  
  static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
  {
  	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);

  	unsigned long flags;
  	struct blkio_group *blkg;
  	void *key;

  	struct blkio_policy_type *blkiop;

  	struct blkio_policy_node *pn, *pntmp;

  
  	rcu_read_lock();

  	do {
  		spin_lock_irqsave(&blkcg->lock, flags);

  		if (hlist_empty(&blkcg->blkg_list)) {
  			spin_unlock_irqrestore(&blkcg->lock, flags);
  			break;
  		}

  		blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
  					blkcg_node);
  		key = rcu_dereference(blkg->key);
  		__blkiocg_del_blkio_group(blkg);

  		spin_unlock_irqrestore(&blkcg->lock, flags);

  		/*
  		 * This blkio_group is being unlinked as associated cgroup is
  		 * going away. Let all the IO controlling policies know about

  		 * this event.

  		 */
  		spin_lock(&blkio_list_lock);

  		list_for_each_entry(blkiop, &blkio_list, list) {
  			if (blkiop->plid != blkg->plid)
  				continue;

  			blkiop->ops.blkio_unlink_group_fn(key, blkg);

  		}

  		spin_unlock(&blkio_list_lock);
  	} while (1);

  	list_for_each_entry_safe(pn, pntmp, &blkcg->policy_list, node) {
  		blkio_policy_delete_node(pn);
  		kfree(pn);
  	}

  	free_css_id(&blkio_subsys, &blkcg->css);

  	rcu_read_unlock();

  	if (blkcg != &blkio_root_cgroup)
  		kfree(blkcg);

  }
  
  static struct cgroup_subsys_state *
  blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
  {

  	struct blkio_cgroup *blkcg;
  	struct cgroup *parent = cgroup->parent;

  	if (!parent) {

  		blkcg = &blkio_root_cgroup;
  		goto done;
  	}

  	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
  	if (!blkcg)
  		return ERR_PTR(-ENOMEM);
  
  	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
  done:
  	spin_lock_init(&blkcg->lock);
  	INIT_HLIST_HEAD(&blkcg->blkg_list);

  	INIT_LIST_HEAD(&blkcg->policy_list);

  	return &blkcg->css;
  }
  
  /*
   * We cannot support shared io contexts, as we have no mean to support
   * two tasks with the same ioc in two different groups without major rework
   * of the main cic data structures.  For now we allow a task to change
   * its cgroup only if it's the only owner of its ioc.
   */

  static int blkiocg_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
  			      struct cgroup_taskset *tset)

  {

  	struct task_struct *task;

  	struct io_context *ioc;
  	int ret = 0;
  
  	/* task_lock() is needed to avoid races with exit_io_context() */

  	cgroup_taskset_for_each(task, cgrp, tset) {
  		task_lock(task);
  		ioc = task->io_context;
  		if (ioc && atomic_read(&ioc->nr_tasks) > 1)
  			ret = -EINVAL;
  		task_unlock(task);
  		if (ret)
  			break;
  	}

  	return ret;
  }

  static void blkiocg_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
  			   struct cgroup_taskset *tset)

  {

  	struct task_struct *task;

  	struct io_context *ioc;

  	cgroup_taskset_for_each(task, cgrp, tset) {

  		/* we don't lose anything even if ioc allocation fails */
  		ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
  		if (ioc) {
  			ioc_cgroup_changed(ioc);
  			put_io_context(ioc, NULL);
  		}

  	}

  }

  void blkio_policy_register(struct blkio_policy_type *blkiop)
  {
  	spin_lock(&blkio_list_lock);
  	list_add_tail(&blkiop->list, &blkio_list);
  	spin_unlock(&blkio_list_lock);
  }
  EXPORT_SYMBOL_GPL(blkio_policy_register);
  
  void blkio_policy_unregister(struct blkio_policy_type *blkiop)
  {
  	spin_lock(&blkio_list_lock);
  	list_del_init(&blkiop->list);
  	spin_unlock(&blkio_list_lock);
  }
  EXPORT_SYMBOL_GPL(blkio_policy_unregister);

  
  static int __init init_cgroup_blkio(void)
  {
  	return cgroup_load_subsys(&blkio_subsys);
  }
  
  static void __exit exit_cgroup_blkio(void)
  {
  	cgroup_unload_subsys(&blkio_subsys);
  }
  
  module_init(init_cgroup_blkio);
  module_exit(exit_cgroup_blkio);
  MODULE_LICENSE("GPL");