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  */
68 struct 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  */
85 void 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  */
94 int 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  */
108 typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
109 int 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  */
122 int 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  */
129 int 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  */
141 int 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  */
154 int 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  */
168 int 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  */
178 int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
179 		    dm_block_t *new_root);
180 
181 struct 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  */
195 int dm_bitset_cursor_begin(struct dm_disk_bitset *info,
196 			   dm_block_t root, uint32_t nr_entries,
197 			   struct dm_bitset_cursor *c);
198 void dm_bitset_cursor_end(struct dm_bitset_cursor *c);
199 
200 int dm_bitset_cursor_next(struct dm_bitset_cursor *c);
201 int dm_bitset_cursor_skip(struct dm_bitset_cursor *c, uint32_t count);
202 bool dm_bitset_cursor_get_value(struct dm_bitset_cursor *c);
203 
204 /*----------------------------------------------------------------*/
205 
206 #endif /* _LINUX_DM_BITSET_H */
207