#ifndef BLK_INTERNAL_H
  #define BLK_INTERNAL_H

  #include <linux/idr.h>

  /* Amount of time in which a process may batch requests */
  #define BLK_BATCH_TIME	(HZ/50UL)
  
  /* Number of requests a "batching" process may submit */
  #define BLK_BATCH_REQ	32

  extern struct kmem_cache *blk_requestq_cachep;

  extern struct kmem_cache *request_cachep;

  extern struct kobj_type blk_queue_ktype;

  extern struct ida blk_queue_ida;

  static inline void __blk_get_queue(struct request_queue *q)
  {
  	kobject_get(&q->kobj);
  }

  int blk_init_rl(struct request_list *rl, struct request_queue *q,
  		gfp_t gfp_mask);
  void blk_exit_rl(struct request_list *rl);

  void init_request_from_bio(struct request *req, struct bio *bio);
  void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
  			struct bio *bio);

  int blk_rq_append_bio(struct request_queue *q, struct request *rq,
  		      struct bio *bio);

  void blk_queue_bypass_start(struct request_queue *q);
  void blk_queue_bypass_end(struct request_queue *q);

  void blk_dequeue_request(struct request *rq);

  void __blk_queue_free_tags(struct request_queue *q);

  bool __blk_end_bidi_request(struct request *rq, int error,
  			    unsigned int nr_bytes, unsigned int bidi_bytes);

  void blk_rq_timed_out_timer(unsigned long data);

  void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
  			  unsigned int *next_set);
  void __blk_add_timer(struct request *req, struct list_head *timeout_list);

  void blk_delete_timer(struct request *);
  void blk_add_timer(struct request *);

  
  bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
  			     struct bio *bio);
  bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
  			    struct bio *bio);
  bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
  			    unsigned int *request_count);
  
  void blk_account_io_start(struct request *req, bool new_io);
  void blk_account_io_completion(struct request *req, unsigned int bytes);
  void blk_account_io_done(struct request *req);

  /*
   * Internal atomic flags for request handling
   */
  enum rq_atomic_flags {
  	REQ_ATOM_COMPLETE = 0,

  	REQ_ATOM_STARTED,

  };
  
  /*
   * EH timer and IO completion will both attempt to 'grab' the request, make

   * sure that only one of them succeeds

   */
  static inline int blk_mark_rq_complete(struct request *rq)
  {
  	return test_and_set_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
  }
  
  static inline void blk_clear_rq_complete(struct request *rq)
  {
  	clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
  }

  /*
   * Internal elevator interface
   */

  #define ELV_ON_HASH(rq) ((rq)->cmd_flags & REQ_HASHED)

  void blk_insert_flush(struct request *rq);
  void blk_abort_flushes(struct request_queue *q);

  static inline struct request *__elv_next_request(struct request_queue *q)
  {
  	struct request *rq;
  
  	while (1) {

  		if (!list_empty(&q->queue_head)) {

  			rq = list_entry_rq(q->queue_head.next);

  			return rq;

  		}

  		/*
  		 * Flush request is running and flush request isn't queueable
  		 * in the drive, we can hold the queue till flush request is
  		 * finished. Even we don't do this, driver can't dispatch next
  		 * requests and will requeue them. And this can improve
  		 * throughput too. For example, we have request flush1, write1,
  		 * flush 2. flush1 is dispatched, then queue is hold, write1
  		 * isn't inserted to queue. After flush1 is finished, flush2
  		 * will be dispatched. Since disk cache is already clean,
  		 * flush2 will be finished very soon, so looks like flush2 is
  		 * folded to flush1.
  		 * Since the queue is hold, a flag is set to indicate the queue
  		 * should be restarted later. Please see flush_end_io() for
  		 * details.
  		 */
  		if (q->flush_pending_idx != q->flush_running_idx &&
  				!queue_flush_queueable(q)) {
  			q->flush_queue_delayed = 1;
  			return NULL;
  		}

  		if (unlikely(blk_queue_bypass(q)) ||

  		    !q->elevator->type->ops.elevator_dispatch_fn(q, 0))

  			return NULL;
  	}
  }
  
  static inline void elv_activate_rq(struct request_queue *q, struct request *rq)
  {
  	struct elevator_queue *e = q->elevator;

  	if (e->type->ops.elevator_activate_req_fn)
  		e->type->ops.elevator_activate_req_fn(q, rq);

  }
  
  static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq)
  {
  	struct elevator_queue *e = q->elevator;

  	if (e->type->ops.elevator_deactivate_req_fn)
  		e->type->ops.elevator_deactivate_req_fn(q, rq);

  }

  #ifdef CONFIG_FAIL_IO_TIMEOUT
  int blk_should_fake_timeout(struct request_queue *);
  ssize_t part_timeout_show(struct device *, struct device_attribute *, char *);
  ssize_t part_timeout_store(struct device *, struct device_attribute *,
  				const char *, size_t);
  #else
  static inline int blk_should_fake_timeout(struct request_queue *q)
  {
  	return 0;
  }
  #endif

  int ll_back_merge_fn(struct request_queue *q, struct request *req,
  		     struct bio *bio);
  int ll_front_merge_fn(struct request_queue *q, struct request *req, 
  		      struct bio *bio);
  int attempt_back_merge(struct request_queue *q, struct request *rq);
  int attempt_front_merge(struct request_queue *q, struct request *rq);

  int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
  				struct request *next);

  void blk_recalc_rq_segments(struct request *rq);

  void blk_rq_set_mixed_merge(struct request *rq);

  bool blk_rq_merge_ok(struct request *rq, struct bio *bio);
  int blk_try_merge(struct request *rq, struct bio *bio);

  void blk_queue_congestion_threshold(struct request_queue *q);

  void __blk_run_queue_uncond(struct request_queue *q);

  int blk_dev_init(void);

  /*
   * Return the threshold (number of used requests) at which the queue is
   * considered to be congested.  It include a little hysteresis to keep the
   * context switch rate down.
   */
  static inline int queue_congestion_on_threshold(struct request_queue *q)
  {
  	return q->nr_congestion_on;
  }
  
  /*
   * The threshold at which a queue is considered to be uncongested
   */
  static inline int queue_congestion_off_threshold(struct request_queue *q)
  {
  	return q->nr_congestion_off;
  }

  /*
   * Contribute to IO statistics IFF:
   *
   *	a) it's attached to a gendisk, and
   *	b) the queue had IO stats enabled when this request was started, and

   *	c) it's a file system request

   */

  static inline int blk_do_io_stat(struct request *rq)

  {

  	return rq->rq_disk &&
  	       (rq->cmd_flags & REQ_IO_STAT) &&

  		(rq->cmd_type == REQ_TYPE_FS);

  }

  /*
   * Internal io_context interface
   */
  void get_io_context(struct io_context *ioc);

  struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q);

  struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
  			     gfp_t gfp_mask);

  void ioc_clear_queue(struct request_queue *q);

  int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);

  
  /**
   * create_io_context - try to create task->io_context

   * @gfp_mask: allocation mask
   * @node: allocation node
   *

   * If %current->io_context is %NULL, allocate a new io_context and install
   * it.  Returns the current %current->io_context which may be %NULL if
   * allocation failed.

   *
   * Note that this function can't be called with IRQ disabled because

   * task_lock which protects %current->io_context is IRQ-unsafe.

   */

  static inline struct io_context *create_io_context(gfp_t gfp_mask, int node)

  {
  	WARN_ON_ONCE(irqs_disabled());

  	if (unlikely(!current->io_context))
  		create_task_io_context(current, gfp_mask, node);
  	return current->io_context;

  }
  
  /*
   * Internal throttling interface
   */

  #ifdef CONFIG_BLK_DEV_THROTTLING

  extern bool blk_throtl_bio(struct request_queue *q, struct bio *bio);

  extern void blk_throtl_drain(struct request_queue *q);

  extern int blk_throtl_init(struct request_queue *q);
  extern void blk_throtl_exit(struct request_queue *q);
  #else /* CONFIG_BLK_DEV_THROTTLING */

  static inline bool blk_throtl_bio(struct request_queue *q, struct bio *bio)

  {

  	return false;

  }

  static inline void blk_throtl_drain(struct request_queue *q) { }

  static inline int blk_throtl_init(struct request_queue *q) { return 0; }
  static inline void blk_throtl_exit(struct request_queue *q) { }
  #endif /* CONFIG_BLK_DEV_THROTTLING */
  
  #endif /* BLK_INTERNAL_H */