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 */
207

source code of linux/drivers/md/persistent-data/dm-bitset.h