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 */
67 struct 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 */
84 void 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 */
93 int 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 */
107 typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
108 int 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 */
121 int 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 */
128 int 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 */
140 int 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 */
153 int 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 */
167 int 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 */
177 int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
178 dm_block_t *new_root);
179
180 struct 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 */
194 int dm_bitset_cursor_begin(struct dm_disk_bitset *info,
195 dm_block_t root, uint32_t nr_entries,
196 struct dm_bitset_cursor *c);
197 void dm_bitset_cursor_end(struct dm_bitset_cursor *c);
198
199 int dm_bitset_cursor_next(struct dm_bitset_cursor *c);
200 int dm_bitset_cursor_skip(struct dm_bitset_cursor *c, uint32_t count);
201 bool dm_bitset_cursor_get_value(struct dm_bitset_cursor *c);
202
203 /*----------------------------------------------------------------*/
204
205 #endif /* _LINUX_DM_BITSET_H */