LXR linux/drivers/md/persistent-data/dm-bitset.h

   1/*
   2 * Copyright (C) 2012 Red Hat, Inc.
   3 *
   4 * This file is released under the GPL.
   5 */
   6#ifndef _LINUX_DM_BITSET_H
   7#define _LINUX_DM_BITSET_H
   8
   9#include "dm-array.h"
  10
  11/*----------------------------------------------------------------*/
  12
  13/*
  14 * This bitset type is a thin wrapper round a dm_array of 64bit words.  It
  15 * uses a tiny, one word cache to reduce the number of array lookups and so
  16 * increase performance.
  17 *
  18 * Like the dm-array that it's based on, the caller needs to keep track of
  19 * the size of the bitset separately.  The underlying dm-array implicitly
  20 * knows how many words it's storing and will return -ENODATA if you try
  21 * and access an out of bounds word.  However, an out of bounds bit in the
  22 * final word will _not_ be detected, you have been warned.
  23 *
  24 * Bits are indexed from zero.
  25
  26 * Typical use:
  27 *
  28 * a) Initialise a dm_disk_bitset structure with dm_disk_bitset_init().
  29 *    This describes the bitset and includes the cache.  It's not called it
  30 *    dm_bitset_info in line with other data structures because it does
  31 *    include instance data.
  32 *
  33 * b) Get yourself a root.  The root is the index of a block of data on the
  34 *    disk that holds a particular instance of an bitset.  You may have a
  35 *    pre existing root in your metadata that you wish to use, or you may
  36 *    want to create a brand new, empty bitset with dm_bitset_empty().
  37 *
  38 * Like the other data structures in this library, dm_bitset objects are
  39 * immutable between transactions.  Update functions will return you the
  40 * root for a _new_ array.  If you've incremented the old root, via
  41 * dm_tm_inc(), before calling the update function you may continue to use
  42 * it in parallel with the new root.
  43 *
  44 * Even read operations may trigger the cache to be flushed and as such
  45 * return a root for a new, updated bitset.
  46 *
  47 * c) resize a bitset with dm_bitset_resize().
  48 *
  49 * d) Set a bit with dm_bitset_set_bit().
  50 *
  51 * e) Clear a bit with dm_bitset_clear_bit().
  52 *
  53 * f) Test a bit with dm_bitset_test_bit().
  54 *
  55 * g) Flush all updates from the cache with dm_bitset_flush().
  56 *
  57 * h) Destroy the bitset with dm_bitset_del().  This tells the transaction
  58 *    manager that you're no longer using this data structure so it can
  59 *    recycle it's blocks.  (dm_bitset_dec() would be a better name for it,
  60 *    but del is in keeping with dm_btree_del()).
  61 */
  62
  63/*
  64 * Opaque object.  Unlike dm_array_info, you should have one of these per
  65 * bitset.  Initialise with dm_disk_bitset_init().
  66 */
  67struct dm_disk_bitset {
  68        struct dm_array_info array_info;
  69
  70        uint32_t current_index;
  71        uint64_t current_bits;
  72
  73        bool current_index_set:1;
  74        bool dirty:1;
  75};
  76
  77/*
  78 * Sets up a dm_disk_bitset structure.  You don't need to do anything with
  79 * this structure when you finish using it.
  80 *
  81 * tm - the transaction manager that should supervise this structure
  82 * info - the structure being initialised
  83 */
  84void dm_disk_bitset_init(struct dm_transaction_manager *tm,
  85                         struct dm_disk_bitset *info);
  86
  87/*
  88 * Create an empty, zero length bitset.
  89 *
  90 * info - describes the bitset
  91 * new_root - on success, points to the new root block
  92 */
  93int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *new_root);
  94
  95/*
  96 * Creates a new bitset populated with values provided by a callback
  97 * function.  This is more efficient than creating an empty bitset,
  98 * resizing, and then setting values since that process incurs a lot of
  99 * copying.
 100 *
 101 * info - describes the array
 102 * root - the root block of the array on disk
 103 * size - the number of entries in the array
 104 * fn - the callback
 105 * context - passed to the callback
 106 */
 107typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
 108int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
 109                  uint32_t size, bit_value_fn fn, void *context);
 110
 111/*
 112 * Resize the bitset.
 113 *
 114 * info - describes the bitset
 115 * old_root - the root block of the array on disk
 116 * old_nr_entries - the number of bits in the old bitset
 117 * new_nr_entries - the number of bits you want in the new bitset
 118 * default_value - the value for any new bits
 119 * new_root - on success, points to the new root block
 120 */
 121int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t old_root,
 122                     uint32_t old_nr_entries, uint32_t new_nr_entries,
 123                     bool default_value, dm_block_t *new_root);
 124
 125/*
 126 * Frees the bitset.
 127 */
 128int dm_bitset_del(struct dm_disk_bitset *info, dm_block_t root);
 129
 130/*
 131 * Set a bit.
 132 *
 133 * info - describes the bitset
 134 * root - the root block of the bitset
 135 * index - the bit index
 136 * new_root - on success, points to the new root block
 137 *
 138 * -ENODATA will be returned if the index is out of bounds.
 139 */
 140int dm_bitset_set_bit(struct dm_disk_bitset *info, dm_block_t root,
 141                      uint32_t index, dm_block_t *new_root);
 142
 143/*
 144 * Clears a bit.
 145 *
 146 * info - describes the bitset
 147 * root - the root block of the bitset
 148 * index - the bit index
 149 * new_root - on success, points to the new root block
 150 *
 151 * -ENODATA will be returned if the index is out of bounds.
 152 */
 153int dm_bitset_clear_bit(struct dm_disk_bitset *info, dm_block_t root,
 154                        uint32_t index, dm_block_t *new_root);
 155
 156/*
 157 * Tests a bit.
 158 *
 159 * info - describes the bitset
 160 * root - the root block of the bitset
 161 * index - the bit index
 162 * new_root - on success, points to the new root block (cached values may have been written)
 163 * result - the bit value you're after
 164 *
 165 * -ENODATA will be returned if the index is out of bounds.
 166 */
 167int dm_bitset_test_bit(struct dm_disk_bitset *info, dm_block_t root,
 168                       uint32_t index, dm_block_t *new_root, bool *result);
 169
 170/*
 171 * Flush any cached changes to disk.
 172 *
 173 * info - describes the bitset
 174 * root - the root block of the bitset
 175 * new_root - on success, points to the new root block
 176 */
 177int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
 178                    dm_block_t *new_root);
 179
 180struct dm_bitset_cursor {
 181        struct dm_disk_bitset *info;
 182        struct dm_array_cursor cursor;
 183
 184        uint32_t entries_remaining;
 185        uint32_t array_index;
 186        uint32_t bit_index;
 187        uint64_t current_bits;
 188};
 189
 190/*
 191 * Make sure you've flush any dm_disk_bitset and updated the root before
 192 * using this.
 193 */
 194int dm_bitset_cursor_begin(struct dm_disk_bitset *info,
 195                           dm_block_t root, uint32_t nr_entries,
 196                           struct dm_bitset_cursor *c);
 197void dm_bitset_cursor_end(struct dm_bitset_cursor *c);
 198
 199int dm_bitset_cursor_next(struct dm_bitset_cursor *c);
 200int dm_bitset_cursor_skip(struct dm_bitset_cursor *c, uint32_t count);
 201bool dm_bitset_cursor_get_value(struct dm_bitset_cursor *c);
 202
 203/*----------------------------------------------------------------*/
 204
 205#endif /* _LINUX_DM_BITSET_H */
 206