linux/drivers/md/bitmap.h
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   1/*
   2 * bitmap.h: Copyright (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
   3 *
   4 * additions: Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.
   5 */
   6#ifndef BITMAP_H
   7#define BITMAP_H 1
   8
   9#define BITMAP_MAJOR_LO 3
  10/* version 4 insists the bitmap is in little-endian order
  11 * with version 3, it is host-endian which is non-portable
  12 */
  13#define BITMAP_MAJOR_HI 4
  14#define BITMAP_MAJOR_HOSTENDIAN 3
  15
  16/*
  17 * in-memory bitmap:
  18 *
  19 * Use 16 bit block counters to track pending writes to each "chunk".
  20 * The 2 high order bits are special-purpose, the first is a flag indicating
  21 * whether a resync is needed.  The second is a flag indicating whether a
  22 * resync is active.
  23 * This means that the counter is actually 14 bits:
  24 *
  25 * +--------+--------+------------------------------------------------+
  26 * | resync | resync |               counter                          |
  27 * | needed | active |                                                |
  28 * |  (0-1) |  (0-1) |              (0-16383)                         |
  29 * +--------+--------+------------------------------------------------+
  30 *
  31 * The "resync needed" bit is set when:
  32 *    a '1' bit is read from storage at startup.
  33 *    a write request fails on some drives
  34 *    a resync is aborted on a chunk with 'resync active' set
  35 * It is cleared (and resync-active set) when a resync starts across all drives
  36 * of the chunk.
  37 *
  38 *
  39 * The "resync active" bit is set when:
  40 *    a resync is started on all drives, and resync_needed is set.
  41 *       resync_needed will be cleared (as long as resync_active wasn't already set).
  42 * It is cleared when a resync completes.
  43 *
  44 * The counter counts pending write requests, plus the on-disk bit.
  45 * When the counter is '1' and the resync bits are clear, the on-disk
  46 * bit can be cleared as well, thus setting the counter to 0.
  47 * When we set a bit, or in the counter (to start a write), if the fields is
  48 * 0, we first set the disk bit and set the counter to 1.
  49 *
  50 * If the counter is 0, the on-disk bit is clear and the stipe is clean
  51 * Anything that dirties the stipe pushes the counter to 2 (at least)
  52 * and sets the on-disk bit (lazily).
  53 * If a periodic sweep find the counter at 2, it is decremented to 1.
  54 * If the sweep find the counter at 1, the on-disk bit is cleared and the
  55 * counter goes to zero.
  56 *
  57 * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
  58 * counters as a fallback when "page" memory cannot be allocated:
  59 *
  60 * Normal case (page memory allocated):
  61 *
  62 *     page pointer (32-bit)
  63 *
  64 *     [ ] ------+
  65 *               |
  66 *               +-------> [   ][   ]..[   ] (4096 byte page == 2048 counters)
  67 *                          c1   c2    c2048
  68 *
  69 * Hijacked case (page memory allocation failed):
  70 *
  71 *     hijacked page pointer (32-bit)
  72 *
  73 *     [                  ][              ] (no page memory allocated)
  74 *      counter #1 (16-bit) counter #2 (16-bit)
  75 *
  76 */
  77
  78#ifdef __KERNEL__
  79
  80#define PAGE_BITS (PAGE_SIZE << 3)
  81#define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
  82
  83typedef __u16 bitmap_counter_t;
  84#define COUNTER_BITS 16
  85#define COUNTER_BIT_SHIFT 4
  86#define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
  87
  88#define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
  89#define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
  90#define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
  91#define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
  92#define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
  93#define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
  94
  95/* how many counters per page? */
  96#define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
  97/* same, except a shift value for more efficient bitops */
  98#define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
  99/* same, except a mask value for more efficient bitops */
 100#define PAGE_COUNTER_MASK  (PAGE_COUNTER_RATIO - 1)
 101
 102#define BITMAP_BLOCK_SHIFT 9
 103
 104#endif
 105
 106/*
 107 * bitmap structures:
 108 */
 109
 110#define BITMAP_MAGIC 0x6d746962
 111
 112/* use these for bitmap->flags and bitmap->sb->state bit-fields */
 113enum bitmap_state {
 114        BITMAP_STALE       = 1,  /* the bitmap file is out of date or had -EIO */
 115        BITMAP_WRITE_ERROR = 2, /* A write error has occurred */
 116        BITMAP_HOSTENDIAN  =15,
 117};
 118
 119/* the superblock at the front of the bitmap file -- little endian */
 120typedef struct bitmap_super_s {
 121        __le32 magic;        /*  0  BITMAP_MAGIC */
 122        __le32 version;      /*  4  the bitmap major for now, could change... */
 123        __u8  uuid[16];      /*  8  128 bit uuid - must match md device uuid */
 124        __le64 events;       /* 24  event counter for the bitmap (1)*/
 125        __le64 events_cleared;/*32  event counter when last bit cleared (2) */
 126        __le64 sync_size;    /* 40  the size of the md device's sync range(3) */
 127        __le32 state;        /* 48  bitmap state information */
 128        __le32 chunksize;    /* 52  the bitmap chunk size in bytes */
 129        __le32 daemon_sleep; /* 56  seconds between disk flushes */
 130        __le32 write_behind; /* 60  number of outstanding write-behind writes */
 131        __le32 sectors_reserved; /* 64 number of 512-byte sectors that are
 132                                  * reserved for the bitmap. */
 133
 134        __u8  pad[256 - 68]; /* set to zero */
 135} bitmap_super_t;
 136
 137/* notes:
 138 * (1) This event counter is updated before the eventcounter in the md superblock
 139 *    When a bitmap is loaded, it is only accepted if this event counter is equal
 140 *    to, or one greater than, the event counter in the superblock.
 141 * (2) This event counter is updated when the other one is *if*and*only*if* the
 142 *    array is not degraded.  As bits are not cleared when the array is degraded,
 143 *    this represents the last time that any bits were cleared.
 144 *    If a device is being added that has an event count with this value or
 145 *    higher, it is accepted as conforming to the bitmap.
 146 * (3)This is the number of sectors represented by the bitmap, and is the range that
 147 *    resync happens across.  For raid1 and raid5/6 it is the size of individual
 148 *    devices.  For raid10 it is the size of the array.
 149 */
 150
 151#ifdef __KERNEL__
 152
 153/* the in-memory bitmap is represented by bitmap_pages */
 154struct bitmap_page {
 155        /*
 156         * map points to the actual memory page
 157         */
 158        char *map;
 159        /*
 160         * in emergencies (when map cannot be alloced), hijack the map
 161         * pointer and use it as two counters itself
 162         */
 163        unsigned int hijacked:1;
 164        /*
 165         * If any counter in this page is '1' or '2' - and so could be
 166         * cleared then that page is marked as 'pending'
 167         */
 168        unsigned int pending:1;
 169        /*
 170         * count of dirty bits on the page
 171         */
 172        unsigned int  count:30;
 173};
 174
 175/* the main bitmap structure - one per mddev */
 176struct bitmap {
 177
 178        struct bitmap_counts {
 179                spinlock_t lock;
 180                struct bitmap_page *bp;
 181                unsigned long pages;            /* total number of pages
 182                                                 * in the bitmap */
 183                unsigned long missing_pages;    /* number of pages
 184                                                 * not yet allocated */
 185                unsigned long chunkshift;       /* chunksize = 2^chunkshift
 186                                                 * (for bitops) */
 187                unsigned long chunks;           /* Total number of data
 188                                                 * chunks for the array */
 189        } counts;
 190
 191        struct mddev *mddev; /* the md device that the bitmap is for */
 192
 193        __u64   events_cleared;
 194        int need_sync;
 195
 196        struct bitmap_storage {
 197                struct file *file;              /* backing disk file */
 198                struct page *sb_page;           /* cached copy of the bitmap
 199                                                 * file superblock */
 200                struct page **filemap;          /* list of cache pages for
 201                                                 * the file */
 202                unsigned long *filemap_attr;    /* attributes associated
 203                                                 * w/ filemap pages */
 204                unsigned long file_pages;       /* number of pages in the file*/
 205                unsigned long bytes;            /* total bytes in the bitmap */
 206        } storage;
 207
 208        unsigned long flags;
 209
 210        int allclean;
 211
 212        atomic_t behind_writes;
 213        unsigned long behind_writes_used; /* highest actual value at runtime */
 214
 215        /*
 216         * the bitmap daemon - periodically wakes up and sweeps the bitmap
 217         * file, cleaning up bits and flushing out pages to disk as necessary
 218         */
 219        unsigned long daemon_lastrun; /* jiffies of last run */
 220        unsigned long last_end_sync; /* when we lasted called end_sync to
 221                                      * update bitmap with resync progress */
 222
 223        atomic_t pending_writes; /* pending writes to the bitmap file */
 224        wait_queue_head_t write_wait;
 225        wait_queue_head_t overflow_wait;
 226        wait_queue_head_t behind_wait;
 227
 228        struct sysfs_dirent *sysfs_can_clear;
 229};
 230
 231/* the bitmap API */
 232
 233/* these are used only by md/bitmap */
 234int  bitmap_create(struct mddev *mddev);
 235int bitmap_load(struct mddev *mddev);
 236void bitmap_flush(struct mddev *mddev);
 237void bitmap_destroy(struct mddev *mddev);
 238
 239void bitmap_print_sb(struct bitmap *bitmap);
 240void bitmap_update_sb(struct bitmap *bitmap);
 241void bitmap_status(struct seq_file *seq, struct bitmap *bitmap);
 242
 243int  bitmap_setallbits(struct bitmap *bitmap);
 244void bitmap_write_all(struct bitmap *bitmap);
 245
 246void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);
 247
 248/* these are exported */
 249int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
 250                        unsigned long sectors, int behind);
 251void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
 252                        unsigned long sectors, int success, int behind);
 253int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int degraded);
 254void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted);
 255void bitmap_close_sync(struct bitmap *bitmap);
 256void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector);
 257
 258void bitmap_unplug(struct bitmap *bitmap);
 259void bitmap_daemon_work(struct mddev *mddev);
 260
 261int bitmap_resize(struct bitmap *bitmap, sector_t blocks,
 262                  int chunksize, int init);
 263#endif
 264
 265#endif
 266
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