drivers/md/bitmap.h

   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
  83 typedef __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 */
 113 enum bitmap_state {
 114         BITMAP_STALE  = 0x002,  /* the bitmap file is out of date or had -EIO */
 115         BITMAP_WRITE_ERROR = 0x004, /* A write error has occurred */
 116         BITMAP_HOSTENDIAN = 0x8000,
 117 };
 118
 119 /* the superblock at the front of the bitmap file -- little endian */
 120 typedef 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
 132         __u8  pad[256 - 64]; /* set to zero */
 133 } bitmap_super_t;
 134
 135 /* notes:
 136  * (1) This event counter is updated before the eventcounter in the md superblock
 137  *    When a bitmap is loaded, it is only accepted if this event counter is equal
 138  *    to, or one greater than, the event counter in the superblock.
 139  * (2) This event counter is updated when the other one is *if*and*only*if* the
 140  *    array is not degraded.  As bits are not cleared when the array is degraded,
 141  *    this represents the last time that any bits were cleared.
 142  *    If a device is being added that has an event count with this value or
 143  *    higher, it is accepted as conforming to the bitmap.
 144  * (3)This is the number of sectors represented by the bitmap, and is the range that
 145  *    resync happens across.  For raid1 and raid5/6 it is the size of individual
 146  *    devices.  For raid10 it is the size of the array.
 147  */
 148
 149 #ifdef __KERNEL__
 150
 151 /* the in-memory bitmap is represented by bitmap_pages */
 152 struct bitmap_page {
 153         /*
 154          * map points to the actual memory page
 155          */
 156         char *map;
 157         /*
 158          * in emergencies (when map cannot be alloced), hijack the map
 159          * pointer and use it as two counters itself
 160          */
 161         unsigned int hijacked:1;
 162         /*
 163          * count of dirty bits on the page
 164          */
 165         unsigned int  count:31;
 166 };
 167
 168 /* the main bitmap structure - one per mddev */
 169 struct bitmap {
 170         struct bitmap_page *bp;
 171         unsigned long pages; /* total number of pages in the bitmap */
 172         unsigned long missing_pages; /* number of pages not yet allocated */
 173
 174         struct mddev *mddev; /* the md device that the bitmap is for */
 175
 176         /* bitmap chunksize -- how much data does each bit represent? */
 177         unsigned long chunkshift; /* chunksize = 2^(chunkshift+9) (for bitops) */
 178         unsigned long chunks; /* total number of data chunks for the array */
 179
 180         __u64   events_cleared;
 181         int need_sync;
 182
 183         /* bitmap spinlock */
 184         spinlock_t lock;
 185
 186         struct file *file; /* backing disk file */
 187         struct page *sb_page; /* cached copy of the bitmap file superblock */
 188         struct page **filemap; /* list of cache pages for the file */
 189         unsigned long *filemap_attr; /* attributes associated w/ filemap pages */
 190         unsigned long file_pages; /* number of pages in the file */
 191         int last_page_size; /* bytes in the last page */
 192
 193         unsigned long flags;
 194
 195         int allclean;
 196
 197         atomic_t behind_writes;
 198         unsigned long behind_writes_used; /* highest actual value at runtime */
 199
 200         /*
 201          * the bitmap daemon - periodically wakes up and sweeps the bitmap
 202          * file, cleaning up bits and flushing out pages to disk as necessary
 203          */
 204         unsigned long daemon_lastrun; /* jiffies of last run */
 205         unsigned long last_end_sync; /* when we lasted called end_sync to
 206                                       * update bitmap with resync progress */
 207
 208         atomic_t pending_writes; /* pending writes to the bitmap file */
 209         wait_queue_head_t write_wait;
 210         wait_queue_head_t overflow_wait;
 211         wait_queue_head_t behind_wait;
 212
 213         struct sysfs_dirent *sysfs_can_clear;
 214 };
 215
 216 /* the bitmap API */
 217
 218 /* these are used only by md/bitmap */
 219 int  bitmap_create(struct mddev *mddev);
 220 int bitmap_load(struct mddev *mddev);
 221 void bitmap_flush(struct mddev *mddev);
 222 void bitmap_destroy(struct mddev *mddev);
 223
 224 void bitmap_print_sb(struct bitmap *bitmap);
 225 void bitmap_update_sb(struct bitmap *bitmap);
 226 void bitmap_status(struct seq_file *seq, struct bitmap *bitmap);
 227
 228 int  bitmap_setallbits(struct bitmap *bitmap);
 229 void bitmap_write_all(struct bitmap *bitmap);
 230
 231 void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);
 232
 233 /* these are exported */
 234 int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
 235                         unsigned long sectors, int behind);
 236 void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
 237                         unsigned long sectors, int success, int behind);
 238 int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int degraded);
 239 void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted);
 240 void bitmap_close_sync(struct bitmap *bitmap);
 241 void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector);
 242
 243 void bitmap_unplug(struct bitmap *bitmap);
 244 void bitmap_daemon_work(struct mddev *mddev);
 245 #endif
 246
 247 #endif