1/*
2 * Copyright (C) 2011 Red Hat, Inc.
3 *
4 * This file is released under the GPL.
5 */
6#ifndef _LINUX_DM_BTREE_H
7#define _LINUX_DM_BTREE_H
8
9#include "dm-block-manager.h"
10
11struct dm_transaction_manager;
12
13/*----------------------------------------------------------------*/
14
15/*
16 * Annotations used to check on-disk metadata is handled as little-endian.
17 */
18#ifdef __CHECKER__
19#  define __dm_written_to_disk(x) __releases(x)
20#  define __dm_reads_from_disk(x) __acquires(x)
21#  define __dm_bless_for_disk(x) __acquire(x)
22#  define __dm_unbless_for_disk(x) __release(x)
23#else
24#  define __dm_written_to_disk(x)
25#  define __dm_reads_from_disk(x)
26#  define __dm_bless_for_disk(x)
27#  define __dm_unbless_for_disk(x)
28#endif
29
30/*----------------------------------------------------------------*/
31
32/*
33 * Manipulates hierarchical B+ trees with 64-bit keys and arbitrary-sized
34 * values.
35 */
36
37/*
38 * Information about the values stored within the btree.
39 */
40struct dm_btree_value_type {
41	void *context;
42
43	/*
44	 * The size in bytes of each value.
45	 */
46	uint32_t size;
47
48	/*
49	 * Any of these methods can be safely set to NULL if you do not
50	 * need the corresponding feature.
51	 */
52
53	/*
54	 * The btree is making a duplicate of the value, for instance
55	 * because previously-shared btree nodes have now diverged.
56	 * @value argument is the new copy that the copy function may modify.
57	 * (Probably it just wants to increment a reference count
58	 * somewhere.) This method is _not_ called for insertion of a new
59	 * value: It is assumed the ref count is already 1.
60	 */
61	void (*inc)(void *context, const void *value);
62
63	/*
64	 * This value is being deleted.  The btree takes care of freeing
65	 * the memory pointed to by @value.  Often the del function just
66	 * needs to decrement a reference count somewhere.
67	 */
68	void (*dec)(void *context, const void *value);
69
70	/*
71	 * A test for equality between two values.  When a value is
72	 * overwritten with a new one, the old one has the dec method
73	 * called _unless_ the new and old value are deemed equal.
74	 */
75	int (*equal)(void *context, const void *value1, const void *value2);
76};
77
78/*
79 * The shape and contents of a btree.
80 */
81struct dm_btree_info {
82	struct dm_transaction_manager *tm;
83
84	/*
85	 * Number of nested btrees. (Not the depth of a single tree.)
86	 */
87	unsigned levels;
88	struct dm_btree_value_type value_type;
89};
90
91/*
92 * Set up an empty tree.  O(1).
93 */
94int dm_btree_empty(struct dm_btree_info *info, dm_block_t *root);
95
96/*
97 * Delete a tree.  O(n) - this is the slow one!  It can also block, so
98 * please don't call it on an IO path.
99 */
100int dm_btree_del(struct dm_btree_info *info, dm_block_t root);
101
102/*
103 * All the lookup functions return -ENODATA if the key cannot be found.
104 */
105
106/*
107 * Tries to find a key that matches exactly.  O(ln(n))
108 */
109int dm_btree_lookup(struct dm_btree_info *info, dm_block_t root,
110		    uint64_t *keys, void *value_le);
111
112/*
113 * Tries to find the first key where the bottom level key is >= to that
114 * given.  Useful for skipping empty sections of the btree.
115 */
116int dm_btree_lookup_next(struct dm_btree_info *info, dm_block_t root,
117			 uint64_t *keys, uint64_t *rkey, void *value_le);
118
119/*
120 * Insertion (or overwrite an existing value).  O(ln(n))
121 */
122int dm_btree_insert(struct dm_btree_info *info, dm_block_t root,
123		    uint64_t *keys, void *value, dm_block_t *new_root)
124		    __dm_written_to_disk(value);
125
126/*
127 * A variant of insert that indicates whether it actually inserted or just
128 * overwrote.  Useful if you're keeping track of the number of entries in a
129 * tree.
130 */
131int dm_btree_insert_notify(struct dm_btree_info *info, dm_block_t root,
132			   uint64_t *keys, void *value, dm_block_t *new_root,
133			   int *inserted)
134			   __dm_written_to_disk(value);
135
136/*
137 * Remove a key if present.  This doesn't remove empty sub trees.  Normally
138 * subtrees represent a separate entity, like a snapshot map, so this is
139 * correct behaviour.  O(ln(n)).
140 */
141int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
142		    uint64_t *keys, dm_block_t *new_root);
143
144/*
145 * Removes a _contiguous_ run of values starting from 'keys' and not
146 * reaching keys2 (where keys2 is keys with the final key replaced with
147 * 'end_key').  'end_key' is the one-past-the-end value.  'keys' may be
148 * altered.
149 */
150int dm_btree_remove_leaves(struct dm_btree_info *info, dm_block_t root,
151			   uint64_t *keys, uint64_t end_key,
152			   dm_block_t *new_root, unsigned *nr_removed);
153
154/*
155 * Returns < 0 on failure.  Otherwise the number of key entries that have
156 * been filled out.  Remember trees can have zero entries, and as such have
157 * no lowest key.
158 */
159int dm_btree_find_lowest_key(struct dm_btree_info *info, dm_block_t root,
160			     uint64_t *result_keys);
161
162/*
163 * Returns < 0 on failure.  Otherwise the number of key entries that have
164 * been filled out.  Remember trees can have zero entries, and as such have
165 * no highest key.
166 */
167int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
168			      uint64_t *result_keys);
169
170/*
171 * Iterate through the a btree, calling fn() on each entry.
172 * It only works for single level trees and is internally recursive, so
173 * monitor stack usage carefully.
174 */
175int dm_btree_walk(struct dm_btree_info *info, dm_block_t root,
176		  int (*fn)(void *context, uint64_t *keys, void *leaf),
177		  void *context);
178
179
180/*----------------------------------------------------------------*/
181
182/*
183 * Cursor API.  This does not follow the rolling lock convention.  Since we
184 * know the order that values are required we can issue prefetches to speed
185 * up iteration.  Use on a single level btree only.
186 */
187#define DM_BTREE_CURSOR_MAX_DEPTH 16
188
189struct cursor_node {
190	struct dm_block *b;
191	unsigned index;
192};
193
194struct dm_btree_cursor {
195	struct dm_btree_info *info;
196	dm_block_t root;
197
198	bool prefetch_leaves;
199	unsigned depth;
200	struct cursor_node nodes[DM_BTREE_CURSOR_MAX_DEPTH];
201};
202
203/*
204 * Creates a fresh cursor.  If prefetch_leaves is set then it is assumed
205 * the btree contains block indexes that will be prefetched.  The cursor is
206 * quite large, so you probably don't want to put it on the stack.
207 */
208int dm_btree_cursor_begin(struct dm_btree_info *info, dm_block_t root,
209			  bool prefetch_leaves, struct dm_btree_cursor *c);
210void dm_btree_cursor_end(struct dm_btree_cursor *c);
211int dm_btree_cursor_next(struct dm_btree_cursor *c);
212int dm_btree_cursor_skip(struct dm_btree_cursor *c, uint32_t count);
213int dm_btree_cursor_get_value(struct dm_btree_cursor *c, uint64_t *key, void *value_le);
214
215#endif	/* _LINUX_DM_BTREE_H */
216