/*

   * include/linux/writeback.h

   */
  #ifndef WRITEBACK_H
  #define WRITEBACK_H

  #include <linux/sched.h>

  #include <linux/fs.h>

  /*

   * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
   *
   *	(thresh - thresh/DIRTY_FULL_SCOPE, thresh)
   *

   * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
   * time) for the dirty pages to drop, unless written enough pages.
   *
   * The global dirty threshold is normally equal to the global dirty limit,
   * except when the system suddenly allocates a lot of anonymous memory and
   * knocks down the global dirty threshold quickly, in which case the global
   * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
   */

  #define DIRTY_SCOPE		8
  #define DIRTY_FULL_SCOPE	(DIRTY_SCOPE / 2)

  /*
   * 4MB minimal write chunk size
   */
  #define MIN_WRITEBACK_PAGES	(4096UL >> (PAGE_CACHE_SHIFT - 10))

  struct backing_dev_info;

  /*

   * fs/fs-writeback.c
   */
  enum writeback_sync_modes {
  	WB_SYNC_NONE,	/* Don't wait on anything */
  	WB_SYNC_ALL,	/* Wait on every mapping */

  };
  
  /*

   * why some writeback work was initiated
   */
  enum wb_reason {
  	WB_REASON_BACKGROUND,
  	WB_REASON_TRY_TO_FREE_PAGES,
  	WB_REASON_SYNC,
  	WB_REASON_PERIODIC,
  	WB_REASON_LAPTOP_TIMER,
  	WB_REASON_FREE_MORE_MEM,
  	WB_REASON_FS_FREE_SPACE,
  	WB_REASON_FORKER_THREAD,
  
  	WB_REASON_MAX,
  };
  extern const char *wb_reason_name[];
  
  /*

   * A control structure which tells the writeback code what to do.  These are
   * always on the stack, and hence need no locking.  They are always initialised
   * in a manner such that unspecified fields are set to zero.
   */
  struct writeback_control {

  	enum writeback_sync_modes sync_mode;

  	long nr_to_write;		/* Write this many pages, and decrement
  					   this for each page written */
  	long pages_skipped;		/* Pages which were not written */
  
  	/*
  	 * For a_ops->writepages(): is start or end are non-zero then this is
  	 * a hint that the filesystem need only write out the pages inside that
  	 * byterange.  The byte at `end' is included in the writeout request.
  	 */

  	loff_t range_start;
  	loff_t range_end;

  	unsigned for_kupdate:1;		/* A kupdate writeback */

  	unsigned for_background:1;	/* A background writeback */

  	unsigned tagged_writepages:1;	/* tag-and-write to avoid livelock */

  	unsigned for_reclaim:1;		/* Invoked from the page allocator */

  	unsigned range_cyclic:1;	/* range_start is cyclic */

  };
  
  /*

   * fs/fs-writeback.c
   */	

  struct bdi_writeback;

  int inode_wait(void *);

  void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  							enum wb_reason reason);
  int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
  int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
  							enum wb_reason reason);

  void sync_inodes_sb(struct super_block *);

  long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
  				enum wb_reason reason);

  long wb_do_writeback(struct bdi_writeback *wb, int force_wait);

  void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);

  
  /* writeback.h requires fs.h; it, too, is not included from here. */
  static inline void wait_on_inode(struct inode *inode)
  {
  	might_sleep();

  	wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);

  }

  static inline void inode_sync_wait(struct inode *inode)
  {
  	might_sleep();
  	wait_on_bit(&inode->i_state, __I_SYNC, inode_wait,
  							TASK_UNINTERRUPTIBLE);
  }

  
  /*
   * mm/page-writeback.c
   */

  #ifdef CONFIG_BLOCK

  void laptop_io_completion(struct backing_dev_info *info);

  void laptop_sync_completion(void);

  void laptop_mode_sync(struct work_struct *work);
  void laptop_mode_timer_fn(unsigned long data);

  #else
  static inline void laptop_sync_completion(void) { }
  #endif

  void throttle_vm_writeout(gfp_t gfp_mask);

  extern unsigned long global_dirty_limit;

  /* These are exported to sysctl. */
  extern int dirty_background_ratio;

  extern unsigned long dirty_background_bytes;

  extern int vm_dirty_ratio;

  extern unsigned long vm_dirty_bytes;

  extern unsigned int dirty_writeback_interval;
  extern unsigned int dirty_expire_interval;

  extern int vm_highmem_is_dirtyable;

  extern int block_dump;
  extern int laptop_mode;

  extern unsigned long determine_dirtyable_memory(void);

  extern int dirty_background_ratio_handler(struct ctl_table *table, int write,

  		void __user *buffer, size_t *lenp,

  		loff_t *ppos);
  extern int dirty_background_bytes_handler(struct ctl_table *table, int write,

  		void __user *buffer, size_t *lenp,

  		loff_t *ppos);

  extern int dirty_ratio_handler(struct ctl_table *table, int write,

  		void __user *buffer, size_t *lenp,

  		loff_t *ppos);

  extern int dirty_bytes_handler(struct ctl_table *table, int write,

  		void __user *buffer, size_t *lenp,

  		loff_t *ppos);

  struct ctl_table;

  int dirty_writeback_centisecs_handler(struct ctl_table *, int,

  				      void __user *, size_t *, loff_t *);

  void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
  unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
  			       unsigned long dirty);

  void __bdi_update_bandwidth(struct backing_dev_info *bdi,

  			    unsigned long thresh,

  			    unsigned long bg_thresh,

  			    unsigned long dirty,
  			    unsigned long bdi_thresh,
  			    unsigned long bdi_dirty,

  			    unsigned long start_time);

  void page_writeback_init(void);

  void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
  					unsigned long nr_pages_dirtied);
  
  static inline void
  balance_dirty_pages_ratelimited(struct address_space *mapping)
  {
  	balance_dirty_pages_ratelimited_nr(mapping, 1);
  }

  typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
  				void *data);

  int generic_writepages(struct address_space *mapping,
  		       struct writeback_control *wbc);

  void tag_pages_for_writeback(struct address_space *mapping,
  			     pgoff_t start, pgoff_t end);

  int write_cache_pages(struct address_space *mapping,
  		      struct writeback_control *wbc, writepage_t writepage,
  		      void *data);

  int do_writepages(struct address_space *mapping, struct writeback_control *wbc);

  void set_page_dirty_balance(struct page *page, int page_mkwrite);

  void writeback_set_ratelimit(void);

  void tag_pages_for_writeback(struct address_space *mapping,
  			     pgoff_t start, pgoff_t end);

  
  /* pdflush.c */
  extern int nr_pdflush_threads;	/* Global so it can be exported to sysctl
  				   read-only. */
  
  
  #endif		/* WRITEBACK_H */