1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef BTREE_H
3 #define BTREE_H
4 
5 #include <linux/kernel.h>
6 #include <linux/mempool.h>
7 
8 /**
9  * DOC: B+Tree basics
10  *
11  * A B+Tree is a data structure for looking up arbitrary (currently allowing
12  * unsigned long, u32, u64 and 2 * u64) keys into pointers. The data structure
13  * is described at http://en.wikipedia.org/wiki/B-tree, we currently do not
14  * use binary search to find the key on lookups.
15  *
16  * Each B+Tree consists of a head, that contains bookkeeping information and
17  * a variable number (starting with zero) nodes. Each node contains the keys
18  * and pointers to sub-nodes, or, for leaf nodes, the keys and values for the
19  * tree entries.
20  *
21  * Each node in this implementation has the following layout:
22  * [key1, key2, ..., keyN] [val1, val2, ..., valN]
23  *
24  * Each key here is an array of unsigned longs, geo->no_longs in total. The
25  * number of keys and values (N) is geo->no_pairs.
26  */
27 
28 /**
29  * struct btree_head - btree head
30  *
31  * @node: the first node in the tree
32  * @mempool: mempool used for node allocations
33  * @height: current of the tree
34  */
35 struct btree_head {
36 	unsigned long *node;
37 	mempool_t *mempool;
38 	int height;
39 };
40 
41 /* btree geometry */
42 struct btree_geo;
43 
44 /**
45  * btree_alloc - allocate function for the mempool
46  * @gfp_mask: gfp mask for the allocation
47  * @pool_data: unused
48  */
49 void *btree_alloc(gfp_t gfp_mask, void *pool_data);
50 
51 /**
52  * btree_free - free function for the mempool
53  * @element: the element to free
54  * @pool_data: unused
55  */
56 void btree_free(void *element, void *pool_data);
57 
58 /**
59  * btree_init_mempool - initialise a btree with given mempool
60  *
61  * @head: the btree head to initialise
62  * @mempool: the mempool to use
63  *
64  * When this function is used, there is no need to destroy
65  * the mempool.
66  */
67 void btree_init_mempool(struct btree_head *head, mempool_t *mempool);
68 
69 /**
70  * btree_init - initialise a btree
71  *
72  * @head: the btree head to initialise
73  *
74  * This function allocates the memory pool that the
75  * btree needs. Returns zero or a negative error code
76  * (-%ENOMEM) when memory allocation fails.
77  *
78  */
79 int __must_check btree_init(struct btree_head *head);
80 
81 /**
82  * btree_destroy - destroy mempool
83  *
84  * @head: the btree head to destroy
85  *
86  * This function destroys the internal memory pool, use only
87  * when using btree_init(), not with btree_init_mempool().
88  */
89 void btree_destroy(struct btree_head *head);
90 
91 /**
92  * btree_lookup - look up a key in the btree
93  *
94  * @head: the btree to look in
95  * @geo: the btree geometry
96  * @key: the key to look up
97  *
98  * This function returns the value for the given key, or %NULL.
99  */
100 void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
101 		   unsigned long *key);
102 
103 /**
104  * btree_insert - insert an entry into the btree
105  *
106  * @head: the btree to add to
107  * @geo: the btree geometry
108  * @key: the key to add (must not already be present)
109  * @val: the value to add (must not be %NULL)
110  * @gfp: allocation flags for node allocations
111  *
112  * This function returns 0 if the item could be added, or an
113  * error code if it failed (may fail due to memory pressure).
114  */
115 int __must_check btree_insert(struct btree_head *head, struct btree_geo *geo,
116 			      unsigned long *key, void *val, gfp_t gfp);
117 /**
118  * btree_update - update an entry in the btree
119  *
120  * @head: the btree to update
121  * @geo: the btree geometry
122  * @key: the key to update
123  * @val: the value to change it to (must not be %NULL)
124  *
125  * This function returns 0 if the update was successful, or
126  * -%ENOENT if the key could not be found.
127  */
128 int btree_update(struct btree_head *head, struct btree_geo *geo,
129 		 unsigned long *key, void *val);
130 /**
131  * btree_remove - remove an entry from the btree
132  *
133  * @head: the btree to update
134  * @geo: the btree geometry
135  * @key: the key to remove
136  *
137  * This function returns the removed entry, or %NULL if the key
138  * could not be found.
139  */
140 void *btree_remove(struct btree_head *head, struct btree_geo *geo,
141 		   unsigned long *key);
142 
143 /**
144  * btree_merge - merge two btrees
145  *
146  * @target: the tree that gets all the entries
147  * @victim: the tree that gets merged into @target
148  * @geo: the btree geometry
149  * @gfp: allocation flags
150  *
151  * The two trees @target and @victim may not contain the same keys,
152  * that is a bug and triggers a BUG(). This function returns zero
153  * if the trees were merged successfully, and may return a failure
154  * when memory allocation fails, in which case both trees might have
155  * been partially merged, i.e. some entries have been moved from
156  * @victim to @target.
157  */
158 int btree_merge(struct btree_head *target, struct btree_head *victim,
159 		struct btree_geo *geo, gfp_t gfp);
160 
161 /**
162  * btree_last - get last entry in btree
163  *
164  * @head: btree head
165  * @geo: btree geometry
166  * @key: last key
167  *
168  * Returns the last entry in the btree, and sets @key to the key
169  * of that entry; returns NULL if the tree is empty, in that case
170  * key is not changed.
171  */
172 void *btree_last(struct btree_head *head, struct btree_geo *geo,
173 		 unsigned long *key);
174 
175 /**
176  * btree_get_prev - get previous entry
177  *
178  * @head: btree head
179  * @geo: btree geometry
180  * @key: pointer to key
181  *
182  * The function returns the next item right before the value pointed to by
183  * @key, and updates @key with its key, or returns %NULL when there is no
184  * entry with a key smaller than the given key.
185  */
186 void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
187 		     unsigned long *key);
188 
189 
190 /* internal use, use btree_visitor{l,32,64,128} */
191 size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
192 		     unsigned long opaque,
193 		     void (*func)(void *elem, unsigned long opaque,
194 				  unsigned long *key, size_t index,
195 				  void *func2),
196 		     void *func2);
197 
198 /* internal use, use btree_grim_visitor{l,32,64,128} */
199 size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
200 			  unsigned long opaque,
201 			  void (*func)(void *elem, unsigned long opaque,
202 				       unsigned long *key,
203 				       size_t index, void *func2),
204 			  void *func2);
205 
206 
207 #include <linux/btree-128.h>
208 
209 extern struct btree_geo btree_geo32;
210 #define BTREE_TYPE_SUFFIX l
211 #define BTREE_TYPE_BITS BITS_PER_LONG
212 #define BTREE_TYPE_GEO &btree_geo32
213 #define BTREE_KEYTYPE unsigned long
214 #include <linux/btree-type.h>
215 
216 #define btree_for_each_safel(head, key, val)	\
217 	for (val = btree_lastl(head, &key);	\
218 	     val;				\
219 	     val = btree_get_prevl(head, &key))
220 
221 #define BTREE_TYPE_SUFFIX 32
222 #define BTREE_TYPE_BITS 32
223 #define BTREE_TYPE_GEO &btree_geo32
224 #define BTREE_KEYTYPE u32
225 #include <linux/btree-type.h>
226 
227 #define btree_for_each_safe32(head, key, val)	\
228 	for (val = btree_last32(head, &key);	\
229 	     val;				\
230 	     val = btree_get_prev32(head, &key))
231 
232 extern struct btree_geo btree_geo64;
233 #define BTREE_TYPE_SUFFIX 64
234 #define BTREE_TYPE_BITS 64
235 #define BTREE_TYPE_GEO &btree_geo64
236 #define BTREE_KEYTYPE u64
237 #include <linux/btree-type.h>
238 
239 #define btree_for_each_safe64(head, key, val)	\
240 	for (val = btree_last64(head, &key);	\
241 	     val;				\
242 	     val = btree_get_prev64(head, &key))
243 
244 #endif
245