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 * Resize the bitset.
97 *
98 * info - describes the bitset
99 * old_root - the root block of the array on disk
100 * old_nr_entries - the number of bits in the old bitset
101 * new_nr_entries - the number of bits you want in the new bitset
102 * default_value - the value for any new bits
103 * new_root - on success, points to the new root block
104 */
105int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t old_root,
106		     uint32_t old_nr_entries, uint32_t new_nr_entries,
107		     bool default_value, dm_block_t *new_root);
108
109/*
110 * Frees the bitset.
111 */
112int dm_bitset_del(struct dm_disk_bitset *info, dm_block_t root);
113
114/*
115 * Set a bit.
116 *
117 * info - describes the bitset
118 * root - the root block of the bitset
119 * index - the bit index
120 * new_root - on success, points to the new root block
121 *
122 * -ENODATA will be returned if the index is out of bounds.
123 */
124int dm_bitset_set_bit(struct dm_disk_bitset *info, dm_block_t root,
125		      uint32_t index, dm_block_t *new_root);
126
127/*
128 * Clears a bit.
129 *
130 * info - describes the bitset
131 * root - the root block of the bitset
132 * index - the bit index
133 * new_root - on success, points to the new root block
134 *
135 * -ENODATA will be returned if the index is out of bounds.
136 */
137int dm_bitset_clear_bit(struct dm_disk_bitset *info, dm_block_t root,
138			uint32_t index, dm_block_t *new_root);
139
140/*
141 * Tests a bit.
142 *
143 * info - describes the bitset
144 * root - the root block of the bitset
145 * index - the bit index
146 * new_root - on success, points to the new root block (cached values may have been written)
147 * result - the bit value you're after
148 *
149 * -ENODATA will be returned if the index is out of bounds.
150 */
151int dm_bitset_test_bit(struct dm_disk_bitset *info, dm_block_t root,
152		       uint32_t index, dm_block_t *new_root, bool *result);
153
154/*
155 * Flush any cached changes to disk.
156 *
157 * info - describes the bitset
158 * root - the root block of the bitset
159 * new_root - on success, points to the new root block
160 */
161int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
162		    dm_block_t *new_root);
163
164/*----------------------------------------------------------------*/
165
166#endif /* _LINUX_DM_BITSET_H */
167