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1/* Private definitions for the generic associative array implementation.
2 *
3 * See Documentation/assoc_array.txt for information.
4 *
5 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public Licence
10 * as published by the Free Software Foundation; either version
11 * 2 of the Licence, or (at your option) any later version.
12 */
13
14#ifndef _LINUX_ASSOC_ARRAY_PRIV_H
15#define _LINUX_ASSOC_ARRAY_PRIV_H
16
17#ifdef CONFIG_ASSOCIATIVE_ARRAY
18
19#include <linux/assoc_array.h>
20
21#define ASSOC_ARRAY_FAN_OUT 16 /* Number of slots per node */
22#define ASSOC_ARRAY_FAN_MASK (ASSOC_ARRAY_FAN_OUT - 1)
23#define ASSOC_ARRAY_LEVEL_STEP (ilog2(ASSOC_ARRAY_FAN_OUT))
24#define ASSOC_ARRAY_LEVEL_STEP_MASK (ASSOC_ARRAY_LEVEL_STEP - 1)
25#define ASSOC_ARRAY_KEY_CHUNK_MASK (ASSOC_ARRAY_KEY_CHUNK_SIZE - 1)
26#define ASSOC_ARRAY_KEY_CHUNK_SHIFT (ilog2(BITS_PER_LONG))
27
28/*
29 * Undefined type representing a pointer with type information in the bottom
30 * two bits.
31 */
32struct assoc_array_ptr;
33
34/*
35 * An N-way node in the tree.
36 *
37 * Each slot contains one of four things:
38 *
39 * (1) Nothing (NULL).
40 *
41 * (2) A leaf object (pointer types 0).
42 *
43 * (3) A next-level node (pointer type 1, subtype 0).
44 *
45 * (4) A shortcut (pointer type 1, subtype 1).
46 *
47 * The tree is optimised for search-by-ID, but permits reasonable iteration
48 * also.
49 *
50 * The tree is navigated by constructing an index key consisting of an array of
51 * segments, where each segment is ilog2(ASSOC_ARRAY_FAN_OUT) bits in size.
52 *
53 * The segments correspond to levels of the tree (the first segment is used at
54 * level 0, the second at level 1, etc.).
55 */
56struct assoc_array_node {
57 struct assoc_array_ptr *back_pointer;
58 u8 parent_slot;
59 struct assoc_array_ptr *slots[ASSOC_ARRAY_FAN_OUT];
60 unsigned long nr_leaves_on_branch;
61};
62
63/*
64 * A shortcut through the index space out to where a collection of nodes/leaves
65 * with the same IDs live.
66 */
67struct assoc_array_shortcut {
68 struct assoc_array_ptr *back_pointer;
69 int parent_slot;
70 int skip_to_level;
71 struct assoc_array_ptr *next_node;
72 unsigned long index_key[];
73};
74
75/*
76 * Preallocation cache.
77 */
78struct assoc_array_edit {
79 struct rcu_head rcu;
80 struct assoc_array *array;
81 const struct assoc_array_ops *ops;
82 const struct assoc_array_ops *ops_for_excised_subtree;
83 struct assoc_array_ptr *leaf;
84 struct assoc_array_ptr **leaf_p;
85 struct assoc_array_ptr *dead_leaf;
86 struct assoc_array_ptr *new_meta[3];
87 struct assoc_array_ptr *excised_meta[1];
88 struct assoc_array_ptr *excised_subtree;
89 struct assoc_array_ptr **set_backpointers[ASSOC_ARRAY_FAN_OUT];
90 struct assoc_array_ptr *set_backpointers_to;
91 struct assoc_array_node *adjust_count_on;
92 long adjust_count_by;
93 struct {
94 struct assoc_array_ptr **ptr;
95 struct assoc_array_ptr *to;
96 } set[2];
97 struct {
98 u8 *p;
99 u8 to;
100 } set_parent_slot[1];
101 u8 segment_cache[ASSOC_ARRAY_FAN_OUT + 1];
102};
103
104/*
105 * Internal tree member pointers are marked in the bottom one or two bits to
106 * indicate what type they are so that we don't have to look behind every
107 * pointer to see what it points to.
108 *
109 * We provide functions to test type annotations and to create and translate
110 * the annotated pointers.
111 */
112#define ASSOC_ARRAY_PTR_TYPE_MASK 0x1UL
113#define ASSOC_ARRAY_PTR_LEAF_TYPE 0x0UL /* Points to leaf (or nowhere) */
114#define ASSOC_ARRAY_PTR_META_TYPE 0x1UL /* Points to node or shortcut */
115#define ASSOC_ARRAY_PTR_SUBTYPE_MASK 0x2UL
116#define ASSOC_ARRAY_PTR_NODE_SUBTYPE 0x0UL
117#define ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE 0x2UL
118
119static inline bool assoc_array_ptr_is_meta(const struct assoc_array_ptr *x)
120{
121 return (unsigned long)x & ASSOC_ARRAY_PTR_TYPE_MASK;
122}
123static inline bool assoc_array_ptr_is_leaf(const struct assoc_array_ptr *x)
124{
125 return !assoc_array_ptr_is_meta(x);
126}
127static inline bool assoc_array_ptr_is_shortcut(const struct assoc_array_ptr *x)
128{
129 return (unsigned long)x & ASSOC_ARRAY_PTR_SUBTYPE_MASK;
130}
131static inline bool assoc_array_ptr_is_node(const struct assoc_array_ptr *x)
132{
133 return !assoc_array_ptr_is_shortcut(x);
134}
135
136static inline void *assoc_array_ptr_to_leaf(const struct assoc_array_ptr *x)
137{
138 return (void *)((unsigned long)x & ~ASSOC_ARRAY_PTR_TYPE_MASK);
139}
140
141static inline
142unsigned long __assoc_array_ptr_to_meta(const struct assoc_array_ptr *x)
143{
144 return (unsigned long)x &
145 ~(ASSOC_ARRAY_PTR_SUBTYPE_MASK | ASSOC_ARRAY_PTR_TYPE_MASK);
146}
147static inline
148struct assoc_array_node *assoc_array_ptr_to_node(const struct assoc_array_ptr *x)
149{
150 return (struct assoc_array_node *)__assoc_array_ptr_to_meta(x);
151}
152static inline
153struct assoc_array_shortcut *assoc_array_ptr_to_shortcut(const struct assoc_array_ptr *x)
154{
155 return (struct assoc_array_shortcut *)__assoc_array_ptr_to_meta(x);
156}
157
158static inline
159struct assoc_array_ptr *__assoc_array_x_to_ptr(const void *p, unsigned long t)
160{
161 return (struct assoc_array_ptr *)((unsigned long)p | t);
162}
163static inline
164struct assoc_array_ptr *assoc_array_leaf_to_ptr(const void *p)
165{
166 return __assoc_array_x_to_ptr(p, ASSOC_ARRAY_PTR_LEAF_TYPE);
167}
168static inline
169struct assoc_array_ptr *assoc_array_node_to_ptr(const struct assoc_array_node *p)
170{
171 return __assoc_array_x_to_ptr(
172 p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_NODE_SUBTYPE);
173}
174static inline
175struct assoc_array_ptr *assoc_array_shortcut_to_ptr(const struct assoc_array_shortcut *p)
176{
177 return __assoc_array_x_to_ptr(
178 p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE);
179}
180
181#endif /* CONFIG_ASSOCIATIVE_ARRAY */
182#endif /* _LINUX_ASSOC_ARRAY_PRIV_H */
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