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/*

 * 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 aswell, 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_RATIO (COUNTER_BITS / 8)

#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)->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)

/*

 * on-disk bitmap:

 *

 * Use one bit per "chunk" (block set). We do the disk I/O on the bitmap

 * file a page at a time. There's a superblock at the start of the file.

 */

/* map chunks (bits) to file pages - offset by the size of the superblock */

#define CHUNK_BIT_OFFSET(chunk) ((chunk) + (sizeof(bitmap_super_t) << 3))

#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 */

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

        int counter_bits; /* how many bits per block counter */

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

        unsigned long chunksize;

        unsigned long chunkshift; /* chunksize = 2^chunkshift (for bitops) */

        unsigned long chunks; /* total number of data chunks for the array */

        /* We hold a count on the chunk currently being synced, and drop

         * it when the last block is started.  If the resync is aborted

         * midway, we need to be able to drop that count, so we remember

         * the counted chunk..

         */

        unsigned long syncchunk;

        __u64   events_cleared;

        /* bitmap spinlock */

        spinlock_t lock;

        long offset; /* offset from superblock if file is NULL */

        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;

        unsigned long max_write_behind; /* write-behind mode */

        atomic_t behind_writes;

        /*

         * 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 daemon_sleep; /* how many seconds between updates? */

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

        wait_queue_head_t write_wait;

        wait_queue_head_t overflow_wait;

};

/* the bitmap API */

/* these are used only by md/bitmap */

int  bitmap_create(mddev_t *mddev);

void bitmap_flush(mddev_t *mddev);

void bitmap_destroy(mddev_t *mddev);

char *file_path(struct file *file, char *buf, int count);

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, int *blocks, int degraded);

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

void bitmap_close_sync(struct bitmap *bitmap);

void bitmap_unplug(struct bitmap *bitmap);

void bitmap_daemon_work(struct bitmap *bitmap);

#endif

#endif