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 */
206