#ifndef IOCONTEXT_H
  #define IOCONTEXT_H

  #include <linux/radix-tree.h>

  #include <linux/rcupdate.h>

  struct cfq_queue;

  struct cfq_ttime {
  	unsigned long last_end_request;
  
  	unsigned long ttime_total;
  	unsigned long ttime_samples;
  	unsigned long ttime_mean;
  };

  struct cfq_io_context {

  	void *key;
  
  	struct cfq_queue *cfqq[2];
  
  	struct io_context *ioc;

  	struct cfq_ttime ttime;

  	struct list_head queue_list;

  	struct hlist_node cic_list;

  
  	void (*dtor)(struct io_context *); /* destructor */
  	void (*exit)(struct io_context *); /* called on task exit */

  
  	struct rcu_head rcu_head;

  };
  
  /*

   * I/O subsystem state of the associated processes.  It is refcounted
   * and kmalloc'ed. These could be shared between processes.

   */
  struct io_context {

  	atomic_long_t refcount;

  	atomic_t nr_tasks;
  
  	/* all the fields below are protected by this lock */
  	spinlock_t lock;

  
  	unsigned short ioprio;
  	unsigned short ioprio_changed;

  #if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)

  	unsigned short cgroup_changed;
  #endif

  	/*
  	 * For request batching
  	 */

  	int nr_batch_requests;     /* Number of requests left in the batch */

  	unsigned long last_waited; /* Time last woken after wait for request */

  	struct radix_tree_root radix_root;

  	struct hlist_head cic_list;

  	void __rcu *ioc_data;

  };

  static inline struct io_context *ioc_task_link(struct io_context *ioc)
  {
  	/*
  	 * if ref count is zero, don't allow sharing (ioc is going away, it's
  	 * a race).
  	 */

  	if (ioc && atomic_long_inc_not_zero(&ioc->refcount)) {

  		atomic_inc(&ioc->nr_tasks);

  		return ioc;

  	}

  
  	return NULL;
  }

  struct task_struct;

  #ifdef CONFIG_BLOCK
  int put_io_context(struct io_context *ioc);

  void exit_io_context(struct task_struct *task);

  struct io_context *get_io_context(gfp_t gfp_flags, int node);
  struct io_context *alloc_io_context(gfp_t gfp_flags, int node);

  #else

  static inline void exit_io_context(struct task_struct *task)

  {
  }
  
  struct io_context;
  static inline int put_io_context(struct io_context *ioc)
  {
  	return 1;
  }
  #endif

  #endif