LCOV - code coverage report
Current view: top level - drivers/md - bitmap.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 2 2 100.0 %
Date: 2017-01-25 Functions: 0 0 -

          Line data    Source code
       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             : #define BITMAP_MINOR 39
      17             : 
      18             : /*
      19             :  * in-memory bitmap:
      20             :  *
      21             :  * Use 16 bit block counters to track pending writes to each "chunk".
      22             :  * The 2 high order bits are special-purpose, the first is a flag indicating
      23             :  * whether a resync is needed.  The second is a flag indicating whether a
      24             :  * resync is active.
      25             :  * This means that the counter is actually 14 bits:
      26             :  *
      27             :  * +--------+--------+------------------------------------------------+
      28             :  * | resync | resync |               counter                          |
      29             :  * | needed | active |                                                |
      30             :  * |  (0-1) |  (0-1) |              (0-16383)                         |
      31             :  * +--------+--------+------------------------------------------------+
      32             :  *
      33             :  * The "resync needed" bit is set when:
      34             :  *    a '1' bit is read from storage at startup.
      35             :  *    a write request fails on some drives
      36             :  *    a resync is aborted on a chunk with 'resync active' set
      37             :  * It is cleared (and resync-active set) when a resync starts across all drives
      38             :  * of the chunk.
      39             :  *
      40             :  *
      41             :  * The "resync active" bit is set when:
      42             :  *    a resync is started on all drives, and resync_needed is set.
      43             :  *       resync_needed will be cleared (as long as resync_active wasn't already set).
      44             :  * It is cleared when a resync completes.
      45             :  *
      46             :  * The counter counts pending write requests, plus the on-disk bit.
      47             :  * When the counter is '1' and the resync bits are clear, the on-disk
      48             :  * bit can be cleared aswell, thus setting the counter to 0.
      49             :  * When we set a bit, or in the counter (to start a write), if the fields is
      50             :  * 0, we first set the disk bit and set the counter to 1.
      51             :  *
      52             :  * If the counter is 0, the on-disk bit is clear and the stipe is clean
      53             :  * Anything that dirties the stipe pushes the counter to 2 (at least)
      54             :  * and sets the on-disk bit (lazily).
      55             :  * If a periodic sweep find the counter at 2, it is decremented to 1.
      56             :  * If the sweep find the counter at 1, the on-disk bit is cleared and the
      57             :  * counter goes to zero.
      58             :  *
      59             :  * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
      60             :  * counters as a fallback when "page" memory cannot be allocated:
      61             :  *
      62             :  * Normal case (page memory allocated):
      63             :  *
      64             :  *     page pointer (32-bit)
      65             :  *
      66             :  *     [ ] ------+
      67             :  *               |
      68             :  *               +-------> [   ][   ]..[   ] (4096 byte page == 2048 counters)
      69             :  *                          c1   c2    c2048
      70             :  *
      71             :  * Hijacked case (page memory allocation failed):
      72             :  *
      73             :  *     hijacked page pointer (32-bit)
      74             :  *
      75             :  *     [                  ][              ] (no page memory allocated)
      76             :  *      counter #1 (16-bit) counter #2 (16-bit)
      77             :  *
      78             :  */
      79             : 
      80             : #ifdef __KERNEL__
      81             : 
      82             : #define PAGE_BITS (PAGE_SIZE << 3)
      83             : #define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
      84             : 
      85             : typedef __u16 bitmap_counter_t;
      86             : #define COUNTER_BITS 16
      87             : #define COUNTER_BIT_SHIFT 4
      88             : #define COUNTER_BYTE_RATIO (COUNTER_BITS / 8)
      89             : #define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
      90             : 
      91             : #define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
      92             : #define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
      93             : #define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
      94             : #define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
      95             : #define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
      96             : #define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
      97             : 
      98             : /* how many counters per page? */
      99             : #define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
     100             : /* same, except a shift value for more efficient bitops */
     101             : #define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
     102             : /* same, except a mask value for more efficient bitops */
     103             : #define PAGE_COUNTER_MASK  (PAGE_COUNTER_RATIO - 1)
     104             : 
     105             : #define BITMAP_BLOCK_SIZE 512
     106             : #define BITMAP_BLOCK_SHIFT 9
     107             : 
     108             : /* how many blocks per chunk? (this is variable) */
     109             : #define CHUNK_BLOCK_RATIO(bitmap) ((bitmap)->mddev->bitmap_info.chunksize >> BITMAP_BLOCK_SHIFT)
     110             : #define CHUNK_BLOCK_SHIFT(bitmap) ((bitmap)->chunkshift - BITMAP_BLOCK_SHIFT)
     111             : #define CHUNK_BLOCK_MASK(bitmap) (CHUNK_BLOCK_RATIO(bitmap) - 1)
     112             : 
     113             : /* when hijacked, the counters and bits represent even larger "chunks" */
     114             : /* there will be 1024 chunks represented by each counter in the page pointers */
     115             : #define PAGEPTR_BLOCK_RATIO(bitmap) \
     116             :                         (CHUNK_BLOCK_RATIO(bitmap) << PAGE_COUNTER_SHIFT >> 1)
     117             : #define PAGEPTR_BLOCK_SHIFT(bitmap) \
     118             :                         (CHUNK_BLOCK_SHIFT(bitmap) + PAGE_COUNTER_SHIFT - 1)
     119             : #define PAGEPTR_BLOCK_MASK(bitmap) (PAGEPTR_BLOCK_RATIO(bitmap) - 1)
     120             : 
     121             : #endif
     122             : 
     123             : /*
     124             :  * bitmap structures:
     125             :  */
     126             : 
     127             : #define BITMAP_MAGIC 0x6d746962
     128             : 
     129             : /* use these for bitmap->flags and bitmap->sb->state bit-fields */
     130             : enum bitmap_state {
     131             :         BITMAP_STALE  = 0x002,  /* the bitmap file is out of date or had -EIO */
     132             :         BITMAP_WRITE_ERROR = 0x004, /* A write error has occurred */
     133             :         BITMAP_HOSTENDIAN = 0x8000,
     134             : };
     135             : 
     136             : /* the superblock at the front of the bitmap file -- little endian */
     137             : typedef struct bitmap_super_s {
     138             :         __le32 magic;        /*  0  BITMAP_MAGIC */
     139             :         __le32 version;      /*  4  the bitmap major for now, could change... */
     140             :         __u8  uuid[16];      /*  8  128 bit uuid - must match md device uuid */
     141             :         __le64 events;       /* 24  event counter for the bitmap (1)*/
     142             :         __le64 events_cleared;/*32  event counter when last bit cleared (2) */
     143             :         __le64 sync_size;    /* 40  the size of the md device's sync range(3) */
     144             :         __le32 state;        /* 48  bitmap state information */
     145             :         __le32 chunksize;    /* 52  the bitmap chunk size in bytes */
     146             :         __le32 daemon_sleep; /* 56  seconds between disk flushes */
     147             :         __le32 write_behind; /* 60  number of outstanding write-behind writes */
     148             : 
     149             :         __u8  pad[256 - 64]; /* set to zero */
     150             : } bitmap_super_t;
     151           1 : 
     152             : /* notes:
     153             :  * (1) This event counter is updated before the eventcounter in the md superblock
     154             :  *    When a bitmap is loaded, it is only accepted if this event counter is equal
     155             :  *    to, or one greater than, the event counter in the superblock.
     156             :  * (2) This event counter is updated when the other one is *if*and*only*if* the
     157             :  *    array is not degraded.  As bits are not cleared when the array is degraded,
     158             :  *    this represents the last time that any bits were cleared.
     159             :  *    If a device is being added that has an event count with this value or
     160             :  *    higher, it is accepted as conforming to the bitmap.
     161             :  * (3)This is the number of sectors represented by the bitmap, and is the range that
     162             :  *    resync happens across.  For raid1 and raid5/6 it is the size of individual
     163             :  *    devices.  For raid10 it is the size of the array.
     164             :  */
     165             : 
     166             : #ifdef __KERNEL__
     167             : 
     168             : /* the in-memory bitmap is represented by bitmap_pages */
     169             : struct bitmap_page {
     170             :         /*
     171             :          * map points to the actual memory page
     172             :          */
     173             :         char *map;
     174             :         /*
     175             :          * in emergencies (when map cannot be alloced), hijack the map
     176             :          * pointer and use it as two counters itself
     177             :          */
     178             :         unsigned int hijacked:1;
     179             :         /*
     180             :          * count of dirty bits on the page
     181             :          */
     182             :         unsigned int  count:31;
     183             : };
     184             : 
     185             : /* keep track of bitmap file pages that have pending writes on them */
     186             : struct page_list {
     187             :         struct list_head list;
     188             :         struct page *page;
     189             : };
     190           1 : 
     191             : /* the main bitmap structure - one per mddev */
     192             : struct bitmap {
     193             :         struct bitmap_page *bp;
     194             :         unsigned long pages; /* total number of pages in the bitmap */
     195             :         unsigned long missing_pages; /* number of pages not yet allocated */
     196             : 
     197             :         mddev_t *mddev; /* the md device that the bitmap is for */
     198             : 
     199             :         int counter_bits; /* how many bits per block counter */
     200             : 
     201             :         /* bitmap chunksize -- how much data does each bit represent? */
     202             :         unsigned long chunkshift; /* chunksize = 2^chunkshift (for bitops) */
     203             :         unsigned long chunks; /* total number of data chunks for the array */
     204             : 
     205             :         /* We hold a count on the chunk currently being synced, and drop
     206             :          * it when the last block is started.  If the resync is aborted
     207             :          * midway, we need to be able to drop that count, so we remember
     208             :          * the counted chunk..
     209             :          */
     210             :         unsigned long syncchunk;
     211             : 
     212             :         __u64   events_cleared;
     213             :         int need_sync;
     214             : 
     215             :         /* bitmap spinlock */
     216             :         spinlock_t lock;
     217             : 
     218             :         struct file *file; /* backing disk file */
     219             :         struct page *sb_page; /* cached copy of the bitmap file superblock */
     220             :         struct page **filemap; /* list of cache pages for the file */
     221             :         unsigned long *filemap_attr; /* attributes associated w/ filemap pages */
     222             :         unsigned long file_pages; /* number of pages in the file */
     223             :         int last_page_size; /* bytes in the last page */
     224             : 
     225             :         unsigned long flags;
     226             : 
     227             :         int allclean;
     228             : 
     229             :         atomic_t behind_writes;
     230             : 
     231             :         /*
     232             :          * the bitmap daemon - periodically wakes up and sweeps the bitmap
     233             :          * file, cleaning up bits and flushing out pages to disk as necessary
     234             :          */
     235             :         unsigned long daemon_lastrun; /* jiffies of last run */
     236             :         unsigned long last_end_sync; /* when we lasted called end_sync to
     237             :                                       * update bitmap with resync progress */
     238             : 
     239             :         atomic_t pending_writes; /* pending writes to the bitmap file */
     240             :         wait_queue_head_t write_wait;
     241             :         wait_queue_head_t overflow_wait;
     242             : 
     243             :         struct sysfs_dirent *sysfs_can_clear;
     244             : };
     245             : 
     246             : /* the bitmap API */
     247             : 
     248             : /* these are used only by md/bitmap */
     249             : int  bitmap_create(mddev_t *mddev);
     250             : void bitmap_flush(mddev_t *mddev);
     251             : void bitmap_destroy(mddev_t *mddev);
     252             : 
     253             : void bitmap_print_sb(struct bitmap *bitmap);
     254             : void bitmap_update_sb(struct bitmap *bitmap);
     255             : 
     256             : int  bitmap_setallbits(struct bitmap *bitmap);
     257             : void bitmap_write_all(struct bitmap *bitmap);
     258             : 
     259             : void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);
     260             : 
     261             : /* these are exported */
     262             : int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
     263             :                         unsigned long sectors, int behind);
     264             : void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
     265             :                         unsigned long sectors, int success, int behind);
     266             : int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int degraded);
     267             : void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted);
     268             : void bitmap_close_sync(struct bitmap *bitmap);
     269             : void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector);
     270             : 
     271             : void bitmap_unplug(struct bitmap *bitmap);
     272             : void bitmap_daemon_work(mddev_t *mddev);
     273             : #endif
     274             : 
     275             : #endif

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