#ifndef _RAID1_H
  #define _RAID1_H

  struct raid1_info {

  	struct md_rdev	*rdev;

  	sector_t	head_position;

  
  	/* When choose the best device for a read (read_balance())
  	 * we try to keep sequential reads one the same device
  	 */
  	sector_t	next_seq_sect;

  	sector_t	seq_start;

  };
  
  /*
   * memory pools need a pointer to the mddev, so they can force an unplug
   * when memory is tight, and a count of the number of drives that the
   * pool was allocated for, so they know how much to allocate and free.
   * mddev->raid_disks cannot be used, as it can change while a pool is active
   * These two datums are stored in a kmalloced struct.

   * The 'raid_disks' here is twice the raid_disks in r1conf.
   * This allows space for each 'real' device can have a replacement in the
   * second half of the array.

   */
  
  struct pool_info {

  	struct mddev *mddev;

  	int	raid_disks;
  };

  struct r1conf {

  	struct mddev		*mddev;

  	struct raid1_info	*mirrors;	/* twice 'raid_disks' to

  						 * allow for replacements.
  						 */

  	int			raid_disks;

  	/* During resync, read_balancing is only allowed on the part
  	 * of the array that has been resynced.  'next_resync' tells us
  	 * where that is.
  	 */
  	sector_t		next_resync;

  	/* When raid1 starts resync, we divide array into four partitions
  	 * |---------|--------------|---------------------|-------------|
  	 *        next_resync   start_next_window       end_window
  	 * start_next_window = next_resync + NEXT_NORMALIO_DISTANCE
  	 * end_window = start_next_window + NEXT_NORMALIO_DISTANCE
  	 * current_window_requests means the count of normalIO between
  	 *   start_next_window and end_window.
  	 * next_window_requests means the count of normalIO after end_window.
  	 * */
  	sector_t		start_next_window;
  	int			current_window_requests;
  	int			next_window_requests;

  	spinlock_t		device_lock;

  	/* list of 'struct r1bio' that need to be processed by raid1d,
  	 * whether to retry a read, writeout a resync or recovery
  	 * block, or anything else.

  	 */

  	struct list_head	retry_list;

  	/* queue pending writes to be submitted on unplug */
  	struct bio_list		pending_bio_list;

  	int			pending_count;

  	/* for use when syncing mirrors:
  	 * We don't allow both normal IO and resync/recovery IO at
  	 * the same time - resync/recovery can only happen when there
  	 * is no other IO.  So when either is active, the other has to wait.
  	 * See more details description in raid1.c near raise_barrier().
  	 */
  	wait_queue_head_t	wait_barrier;

  	spinlock_t		resync_lock;

  	int			nr_pending;

  	int			nr_waiting;

  	int			nr_queued;

  	int			barrier;

  	int			array_frozen;

  	/* Set to 1 if a full sync is needed, (fresh device added).
  	 * Cleared when a sync completes.
  	 */
  	int			fullsync;

  	/* When the same as mddev->recovery_disabled we don't allow
  	 * recovery to be attempted as we expect a read error.
  	 */
  	int			recovery_disabled;

  	/* poolinfo contains information about the content of the
  	 * mempools - it changes when the array grows or shrinks
  	 */
  	struct pool_info	*poolinfo;

  	mempool_t		*r1bio_pool;
  	mempool_t		*r1buf_pool;

  	/* temporary buffer to synchronous IO when attempting to repair
  	 * a read error.
  	 */
  	struct page		*tmppage;

  	/* When taking over an array from a different personality, we store
  	 * the new thread here until we fully activate the array.
  	 */

  	struct md_thread	*thread;

  };

  /*

   * this is our 'private' RAID1 bio.
   *
   * it contains information about what kind of IO operations were started
   * for this RAID1 operation, and about their status:
   */

  struct r1bio {

  	atomic_t		remaining; /* 'have we finished' count,
  					    * used from IRQ handlers
  					    */

  	atomic_t		behind_remaining; /* number of write-behind ios remaining
  						 * in this BehindIO request
  						 */

  	sector_t		sector;

  	sector_t		start_next_window;

  	int			sectors;
  	unsigned long		state;

  	struct mddev		*mddev;

  	/*
  	 * original bio going to /dev/mdx
  	 */
  	struct bio		*master_bio;
  	/*
  	 * if the IO is in READ direction, then this is where we read
  	 */
  	int			read_disk;
  
  	struct list_head	retry_list;

  	/* Next two are only valid when R1BIO_BehindIO is set */

  	struct bio_vec		*behind_bvecs;

  	int			behind_page_count;

  	/*
  	 * if the IO is in WRITE direction, then multiple bios are used.
  	 * We choose the number when they are allocated.
  	 */
  	struct bio		*bios[0];

  	/* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/

  };
  
  /* bits for r1bio.state */
  #define	R1BIO_Uptodate	0
  #define	R1BIO_IsSync	1

  #define	R1BIO_Degraded	2

  #define	R1BIO_BehindIO	3

  /* Set ReadError on bios that experience a readerror so that
   * raid1d knows what to do with them.
   */
  #define R1BIO_ReadError 4

  /* For write-behind requests, we call bi_end_io when
   * the last non-write-behind device completes, providing
   * any write was successful.  Otherwise we call when
   * any write-behind write succeeds, otherwise we call
   * with failure when last write completes (and all failed).
   * Record that bi_end_io was called with this flag...
   */

  #define	R1BIO_Returned 6

  /* If a write for this request means we can clear some
   * known-bad-block records, we set this flag
   */

  #define	R1BIO_MadeGood 7
  #define	R1BIO_WriteError 8

  extern int md_raid1_congested(struct mddev *mddev, int bits);

  #endif