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 */
 68struct 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 */
 85void 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 */
 94int 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 */
108typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
109int 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 */
122int 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 */
129int 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 */
141int 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 */
154int 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 */
168int 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 */
178int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
179		    dm_block_t *new_root);
180
181struct 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 */
195int dm_bitset_cursor_begin(struct dm_disk_bitset *info,
196			   dm_block_t root, uint32_t nr_entries,
197			   struct dm_bitset_cursor *c);
198void dm_bitset_cursor_end(struct dm_bitset_cursor *c);
199
200int dm_bitset_cursor_next(struct dm_bitset_cursor *c);
201int dm_bitset_cursor_skip(struct dm_bitset_cursor *c, uint32_t count);
202bool dm_bitset_cursor_get_value(struct dm_bitset_cursor *c);
203
204/*----------------------------------------------------------------*/
205
206#endif /* _LINUX_DM_BITSET_H */