/*
   * bitmap.h: Copyright (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
   *
   * additions: Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.
   */
  #ifndef BITMAP_H
  #define BITMAP_H 1

  #define BITMAP_MAJOR_LO 3
  /* version 4 insists the bitmap is in little-endian order
   * with version 3, it is host-endian which is non-portable
   */
  #define BITMAP_MAJOR_HI 4
  #define	BITMAP_MAJOR_HOSTENDIAN 3

  #define BITMAP_MINOR 39

  
  /*
   * in-memory bitmap:
   *
   * Use 16 bit block counters to track pending writes to each "chunk".
   * The 2 high order bits are special-purpose, the first is a flag indicating
   * whether a resync is needed.  The second is a flag indicating whether a
   * resync is active.
   * This means that the counter is actually 14 bits:
   *
   * +--------+--------+------------------------------------------------+
   * | resync | resync |               counter                          |
   * | needed | active |                                                |
   * |  (0-1) |  (0-1) |              (0-16383)                         |
   * +--------+--------+------------------------------------------------+
   *
   * The "resync needed" bit is set when:
   *    a '1' bit is read from storage at startup.
   *    a write request fails on some drives
   *    a resync is aborted on a chunk with 'resync active' set
   * It is cleared (and resync-active set) when a resync starts across all drives
   * of the chunk.
   *
   *
   * The "resync active" bit is set when:
   *    a resync is started on all drives, and resync_needed is set.
   *       resync_needed will be cleared (as long as resync_active wasn't already set).
   * It is cleared when a resync completes.
   *
   * The counter counts pending write requests, plus the on-disk bit.
   * When the counter is '1' and the resync bits are clear, the on-disk

   * bit can be cleared as well, thus setting the counter to 0.

   * When we set a bit, or in the counter (to start a write), if the fields is
   * 0, we first set the disk bit and set the counter to 1.
   *
   * If the counter is 0, the on-disk bit is clear and the stipe is clean
   * Anything that dirties the stipe pushes the counter to 2 (at least)
   * and sets the on-disk bit (lazily).
   * If a periodic sweep find the counter at 2, it is decremented to 1.
   * If the sweep find the counter at 1, the on-disk bit is cleared and the
   * counter goes to zero.
   *
   * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
   * counters as a fallback when "page" memory cannot be allocated:
   *
   * Normal case (page memory allocated):
   *
   *     page pointer (32-bit)
   *
   *     [ ] ------+
   *               |
   *               +-------> [   ][   ]..[   ] (4096 byte page == 2048 counters)
   *                          c1   c2    c2048
   *
   * Hijacked case (page memory allocation failed):
   *
   *     hijacked page pointer (32-bit)
   *
   *     [		  ][		  ] (no page memory allocated)
   *      counter #1 (16-bit) counter #2 (16-bit)
   *
   */
  
  #ifdef __KERNEL__
  
  #define PAGE_BITS (PAGE_SIZE << 3)
  #define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
  
  typedef __u16 bitmap_counter_t;
  #define COUNTER_BITS 16
  #define COUNTER_BIT_SHIFT 4

  #define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
  
  #define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
  #define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
  #define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
  #define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
  #define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
  #define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
  
  /* how many counters per page? */
  #define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
  /* same, except a shift value for more efficient bitops */
  #define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
  /* same, except a mask value for more efficient bitops */
  #define PAGE_COUNTER_MASK  (PAGE_COUNTER_RATIO - 1)
  
  #define BITMAP_BLOCK_SIZE 512
  #define BITMAP_BLOCK_SHIFT 9
  
  /* how many blocks per chunk? (this is variable) */

  #define CHUNK_BLOCK_RATIO(bitmap) ((bitmap)->mddev->bitmap_info.chunksize >> BITMAP_BLOCK_SHIFT)

  #define CHUNK_BLOCK_SHIFT(bitmap) ((bitmap)->chunkshift - BITMAP_BLOCK_SHIFT)
  #define CHUNK_BLOCK_MASK(bitmap) (CHUNK_BLOCK_RATIO(bitmap) - 1)
  
  /* when hijacked, the counters and bits represent even larger "chunks" */
  /* there will be 1024 chunks represented by each counter in the page pointers */
  #define PAGEPTR_BLOCK_RATIO(bitmap) \
  			(CHUNK_BLOCK_RATIO(bitmap) << PAGE_COUNTER_SHIFT >> 1)
  #define PAGEPTR_BLOCK_SHIFT(bitmap) \
  			(CHUNK_BLOCK_SHIFT(bitmap) + PAGE_COUNTER_SHIFT - 1)
  #define PAGEPTR_BLOCK_MASK(bitmap) (PAGEPTR_BLOCK_RATIO(bitmap) - 1)

  #endif
  
  /*
   * bitmap structures:
   */
  
  #define BITMAP_MAGIC 0x6d746962
  
  /* use these for bitmap->flags and bitmap->sb->state bit-fields */
  enum bitmap_state {

  	BITMAP_STALE  = 0x002,  /* the bitmap file is out of date or had -EIO */

  	BITMAP_WRITE_ERROR = 0x004, /* A write error has occurred */

  	BITMAP_HOSTENDIAN = 0x8000,

  };
  
  /* the superblock at the front of the bitmap file -- little endian */
  typedef struct bitmap_super_s {

  	__le32 magic;        /*  0  BITMAP_MAGIC */
  	__le32 version;      /*  4  the bitmap major for now, could change... */
  	__u8  uuid[16];      /*  8  128 bit uuid - must match md device uuid */
  	__le64 events;       /* 24  event counter for the bitmap (1)*/
  	__le64 events_cleared;/*32  event counter when last bit cleared (2) */
  	__le64 sync_size;    /* 40  the size of the md device's sync range(3) */
  	__le32 state;        /* 48  bitmap state information */
  	__le32 chunksize;    /* 52  the bitmap chunk size in bytes */
  	__le32 daemon_sleep; /* 56  seconds between disk flushes */
  	__le32 write_behind; /* 60  number of outstanding write-behind writes */

  	__u8  pad[256 - 64]; /* set to zero */

  } bitmap_super_t;
  
  /* notes:
   * (1) This event counter is updated before the eventcounter in the md superblock
   *    When a bitmap is loaded, it is only accepted if this event counter is equal
   *    to, or one greater than, the event counter in the superblock.
   * (2) This event counter is updated when the other one is *if*and*only*if* the
   *    array is not degraded.  As bits are not cleared when the array is degraded,
   *    this represents the last time that any bits were cleared.
   *    If a device is being added that has an event count with this value or
   *    higher, it is accepted as conforming to the bitmap.
   * (3)This is the number of sectors represented by the bitmap, and is the range that
   *    resync happens across.  For raid1 and raid5/6 it is the size of individual
   *    devices.  For raid10 it is the size of the array.
   */
  
  #ifdef __KERNEL__
  
  /* the in-memory bitmap is represented by bitmap_pages */
  struct bitmap_page {
  	/*
  	 * map points to the actual memory page
  	 */
  	char *map;
  	/*
  	 * in emergencies (when map cannot be alloced), hijack the map
  	 * pointer and use it as two counters itself
  	 */
  	unsigned int hijacked:1;
  	/*
  	 * count of dirty bits on the page
  	 */
  	unsigned int  count:31;
  };
  
  /* keep track of bitmap file pages that have pending writes on them */
  struct page_list {
  	struct list_head list;
  	struct page *page;
  };
  
  /* the main bitmap structure - one per mddev */
  struct bitmap {
  	struct bitmap_page *bp;
  	unsigned long pages; /* total number of pages in the bitmap */
  	unsigned long missing_pages; /* number of pages not yet allocated */

  	struct mddev *mddev; /* the md device that the bitmap is for */

  	/* bitmap chunksize -- how much data does each bit represent? */

  	unsigned long chunkshift; /* chunksize = 2^chunkshift (for bitops) */
  	unsigned long chunks; /* total number of data chunks for the array */

  	__u64	events_cleared;

  	int need_sync;

  
  	/* bitmap spinlock */
  	spinlock_t lock;
  
  	struct file *file; /* backing disk file */
  	struct page *sb_page; /* cached copy of the bitmap file superblock */
  	struct page **filemap; /* list of cache pages for the file */
  	unsigned long *filemap_attr; /* attributes associated w/ filemap pages */
  	unsigned long file_pages; /* number of pages in the file */

  	int last_page_size; /* bytes in the last page */

  
  	unsigned long flags;

  	int allclean;

  	atomic_t behind_writes;

  	unsigned long behind_writes_used; /* highest actual value at runtime */

  	/*
  	 * the bitmap daemon - periodically wakes up and sweeps the bitmap
  	 * file, cleaning up bits and flushing out pages to disk as necessary
  	 */
  	unsigned long daemon_lastrun; /* jiffies of last run */

  	unsigned long last_end_sync; /* when we lasted called end_sync to
  				      * update bitmap with resync progress */

  	atomic_t pending_writes; /* pending writes to the bitmap file */
  	wait_queue_head_t write_wait;

  	wait_queue_head_t overflow_wait;

  	wait_queue_head_t behind_wait;

  	struct sysfs_dirent *sysfs_can_clear;

  };
  
  /* the bitmap API */
  
  /* these are used only by md/bitmap */

  int  bitmap_create(struct mddev *mddev);
  int bitmap_load(struct mddev *mddev);
  void bitmap_flush(struct mddev *mddev);
  void bitmap_destroy(struct mddev *mddev);

  void bitmap_print_sb(struct bitmap *bitmap);

  void bitmap_update_sb(struct bitmap *bitmap);

  
  int  bitmap_setallbits(struct bitmap *bitmap);

  void bitmap_write_all(struct bitmap *bitmap);

  void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);

  /* these are exported */

  int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
  			unsigned long sectors, int behind);
  void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
  			unsigned long sectors, int success, int behind);

  int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int degraded);
  void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted);

  void bitmap_close_sync(struct bitmap *bitmap);

  void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector);

  void bitmap_unplug(struct bitmap *bitmap);

  void bitmap_daemon_work(struct mddev *mddev);

  #endif
  
  #endif