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

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright (C) 2012 Red Hat, Inc.
   4  *
   5  * This file is released under the GPL.
   6  */
   7 #ifndef _LINUX_DM_BITSET_H
   8 #define _LINUX_DM_BITSET_H
   9
  10 #include "dm-array.h"
  11
  12 /*----------------------------------------------------------------*/
  13
  14 /*
  15  * This bitset type is a thin wrapper round a dm_array of 64bit words.  It
  16  * uses a tiny, one word cache to reduce the number of array lookups and so
  17  * increase performance.
  18  *
  19  * Like the dm-array that it's based on, the caller needs to keep track of
  20  * the size of the bitset separately.  The underlying dm-array implicitly
  21  * knows how many words it's storing and will return -ENODATA if you try
  22  * and access an out of bounds word.  However, an out of bounds bit in the
  23  * final word will _not_ be detected, you have been warned.
  24  *
  25  * Bits are indexed from zero.
  26
  27  * Typical use:
  28  *
  29  * a) Initialise a dm_disk_bitset structure with dm_disk_bitset_init().
  30  *    This describes the bitset and includes the cache.  It's not called it
  31  *    dm_bitset_info in line with other data structures because it does
  32  *    include instance data.
  33  *
  34  * b) Get yourself a root.  The root is the index of a block of data on the
  35  *    disk that holds a particular instance of an bitset.  You may have a
  36  *    pre existing root in your metadata that you wish to use, or you may
  37  *    want to create a brand new, empty bitset with dm_bitset_empty().
  38  *
  39  * Like the other data structures in this library, dm_bitset objects are
  40  * immutable between transactions.  Update functions will return you the
  41  * root for a _new_ array.  If you've incremented the old root, via
  42  * dm_tm_inc(), before calling the update function you may continue to use
  43  * it in parallel with the new root.
  44  *
  45  * Even read operations may trigger the cache to be flushed and as such
  46  * return a root for a new, updated bitset.
  47  *
  48  * c) resize a bitset with dm_bitset_resize().
  49  *
  50  * d) Set a bit with dm_bitset_set_bit().
  51  *
  52  * e) Clear a bit with dm_bitset_clear_bit().
  53  *
  54  * f) Test a bit with dm_bitset_test_bit().
  55  *
  56  * g) Flush all updates from the cache with dm_bitset_flush().
  57  *
  58  * h) Destroy the bitset with dm_bitset_del().  This tells the transaction
  59  *    manager that you're no longer using this data structure so it can
  60  *    recycle it's blocks.  (dm_bitset_dec() would be a better name for it,
  61  *    but del is in keeping with dm_btree_del()).
  62  */
  63
  64 /*
  65  * Opaque object.  Unlike dm_array_info, you should have one of these per
  66  * bitset.  Initialise with dm_disk_bitset_init().
  67  */
  68 struct dm_disk_bitset {
  69         struct dm_array_info array_info;
  70
  71         uint32_t current_index;
  72         uint64_t current_bits;
  73
  74         bool current_index_set:1;
  75         bool dirty:1;
  76 };
  77
  78 /*
  79  * Sets up a dm_disk_bitset structure.  You don't need to do anything with
  80  * this structure when you finish using it.
  81  *
  82  * tm - the transaction manager that should supervise this structure
  83  * info - the structure being initialised
  84  */
  85 void dm_disk_bitset_init(struct dm_transaction_manager *tm,
  86                          struct dm_disk_bitset *info);
  87
  88 /*
  89  * Create an empty, zero length bitset.
  90  *
  91  * info - describes the bitset
  92  * new_root - on success, points to the new root block
  93  */
  94 int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *new_root);
  95
  96 /*
  97  * Creates a new bitset populated with values provided by a callback
  98  * function.  This is more efficient than creating an empty bitset,
  99  * resizing, and then setting values since that process incurs a lot of
 100  * copying.
 101  *
 102  * info - describes the array
 103  * root - the root block of the array on disk
 104  * size - the number of entries in the array
 105  * fn - the callback
 106  * context - passed to the callback
 107  */
 108 typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
 109 int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
 110                   uint32_t size, bit_value_fn fn, void *context);
 111
 112 /*
 113  * Resize the bitset.
 114  *
 115  * info - describes the bitset
 116  * old_root - the root block of the array on disk
 117  * old_nr_entries - the number of bits in the old bitset
 118  * new_nr_entries - the number of bits you want in the new bitset
 119  * default_value - the value for any new bits
 120  * new_root - on success, points to the new root block
 121  */
 122 int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t old_root,
 123                      uint32_t old_nr_entries, uint32_t new_nr_entries,
 124                      bool default_value, dm_block_t *new_root);
 125
 126 /*
 127  * Frees the bitset.
 128  */
 129 int dm_bitset_del(struct dm_disk_bitset *info, dm_block_t root);
 130
 131 /*
 132  * Set a bit.
 133  *
 134  * info - describes the bitset
 135  * root - the root block of the bitset
 136  * index - the bit index
 137  * new_root - on success, points to the new root block
 138  *
 139  * -ENODATA will be returned if the index is out of bounds.
 140  */
 141 int dm_bitset_set_bit(struct dm_disk_bitset *info, dm_block_t root,
 142                       uint32_t index, dm_block_t *new_root);
 143
 144 /*
 145  * Clears a bit.
 146  *
 147  * info - describes the bitset
 148  * root - the root block of the bitset
 149  * index - the bit index
 150  * new_root - on success, points to the new root block
 151  *
 152  * -ENODATA will be returned if the index is out of bounds.
 153  */
 154 int dm_bitset_clear_bit(struct dm_disk_bitset *info, dm_block_t root,
 155                         uint32_t index, dm_block_t *new_root);
 156
 157 /*
 158  * Tests a bit.
 159  *
 160  * info - describes the bitset
 161  * root - the root block of the bitset
 162  * index - the bit index
 163  * new_root - on success, points to the new root block (cached values may have been written)
 164  * result - the bit value you're after
 165  *
 166  * -ENODATA will be returned if the index is out of bounds.
 167  */
 168 int dm_bitset_test_bit(struct dm_disk_bitset *info, dm_block_t root,
 169                        uint32_t index, dm_block_t *new_root, bool *result);
 170
 171 /*
 172  * Flush any cached changes to disk.
 173  *
 174  * info - describes the bitset
 175  * root - the root block of the bitset
 176  * new_root - on success, points to the new root block
 177  */
 178 int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
 179                     dm_block_t *new_root);
 180
 181 struct dm_bitset_cursor {
 182         struct dm_disk_bitset *info;
 183         struct dm_array_cursor cursor;
 184
 185         uint32_t entries_remaining;
 186         uint32_t array_index;
 187         uint32_t bit_index;
 188         uint64_t current_bits;
 189 };
 190
 191 /*
 192  * Make sure you've flush any dm_disk_bitset and updated the root before
 193  * using this.
 194  */
 195 int dm_bitset_cursor_begin(struct dm_disk_bitset *info,
 196                            dm_block_t root, uint32_t nr_entries,
 197                            struct dm_bitset_cursor *c);
 198 void dm_bitset_cursor_end(struct dm_bitset_cursor *c);
 199
 200 int dm_bitset_cursor_next(struct dm_bitset_cursor *c);
 201 int dm_bitset_cursor_skip(struct dm_bitset_cursor *c, uint32_t count);
 202 bool dm_bitset_cursor_get_value(struct dm_bitset_cursor *c);
 203
 204 /*----------------------------------------------------------------*/
 205
 206 #endif /* _LINUX_DM_BITSET_H */