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 */