1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/* Private definitions for the generic associative array implementation.
3 *
4 * See Documentation/core-api/assoc_array.rst for information.
5 *
6 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
7 * Written by David Howells (dhowells@redhat.com)
8 */
9
10#ifndef _LINUX_ASSOC_ARRAY_PRIV_H
11#define _LINUX_ASSOC_ARRAY_PRIV_H
12
13#ifdef CONFIG_ASSOCIATIVE_ARRAY
14
15#include <linux/assoc_array.h>
16
17#define ASSOC_ARRAY_FAN_OUT 16 /* Number of slots per node */
18#define ASSOC_ARRAY_FAN_MASK (ASSOC_ARRAY_FAN_OUT - 1)
19#define ASSOC_ARRAY_LEVEL_STEP (ilog2(ASSOC_ARRAY_FAN_OUT))
20#define ASSOC_ARRAY_LEVEL_STEP_MASK (ASSOC_ARRAY_LEVEL_STEP - 1)
21#define ASSOC_ARRAY_KEY_CHUNK_MASK (ASSOC_ARRAY_KEY_CHUNK_SIZE - 1)
22#define ASSOC_ARRAY_KEY_CHUNK_SHIFT (ilog2(BITS_PER_LONG))
23
24/*
25 * Undefined type representing a pointer with type information in the bottom
26 * two bits.
27 */
28struct assoc_array_ptr;
29
30/*
31 * An N-way node in the tree.
32 *
33 * Each slot contains one of four things:
34 *
35 * (1) Nothing (NULL).
36 *
37 * (2) A leaf object (pointer types 0).
38 *
39 * (3) A next-level node (pointer type 1, subtype 0).
40 *
41 * (4) A shortcut (pointer type 1, subtype 1).
42 *
43 * The tree is optimised for search-by-ID, but permits reasonable iteration
44 * also.
45 *
46 * The tree is navigated by constructing an index key consisting of an array of
47 * segments, where each segment is ilog2(ASSOC_ARRAY_FAN_OUT) bits in size.
48 *
49 * The segments correspond to levels of the tree (the first segment is used at
50 * level 0, the second at level 1, etc.).
51 */
52struct assoc_array_node {
53 struct assoc_array_ptr *back_pointer;
54 u8 parent_slot;
55 struct assoc_array_ptr *slots[ASSOC_ARRAY_FAN_OUT];
56 unsigned long nr_leaves_on_branch;
57};
58
59/*
60 * A shortcut through the index space out to where a collection of nodes/leaves
61 * with the same IDs live.
62 */
63struct assoc_array_shortcut {
64 struct assoc_array_ptr *back_pointer;
65 int parent_slot;
66 int skip_to_level;
67 struct assoc_array_ptr *next_node;
68 unsigned long index_key[];
69};
70
71/*
72 * Preallocation cache.
73 */
74struct assoc_array_edit {
75 struct rcu_head rcu;
76 struct assoc_array *array;
77 const struct assoc_array_ops *ops;
78 const struct assoc_array_ops *ops_for_excised_subtree;
79 struct assoc_array_ptr *leaf;
80 struct assoc_array_ptr **leaf_p;
81 struct assoc_array_ptr *dead_leaf;
82 struct assoc_array_ptr *new_meta[3];
83 struct assoc_array_ptr *excised_meta[1];
84 struct assoc_array_ptr *excised_subtree;
85 struct assoc_array_ptr **set_backpointers[ASSOC_ARRAY_FAN_OUT];
86 struct assoc_array_ptr *set_backpointers_to;
87 struct assoc_array_node *adjust_count_on;
88 long adjust_count_by;
89 struct {
90 struct assoc_array_ptr **ptr;
91 struct assoc_array_ptr *to;
92 } set[2];
93 struct {
94 u8 *p;
95 u8 to;
96 } set_parent_slot[1];
97 u8 segment_cache[ASSOC_ARRAY_FAN_OUT + 1];
98};
99
100/*
101 * Internal tree member pointers are marked in the bottom one or two bits to
102 * indicate what type they are so that we don't have to look behind every
103 * pointer to see what it points to.
104 *
105 * We provide functions to test type annotations and to create and translate
106 * the annotated pointers.
107 */
108#define ASSOC_ARRAY_PTR_TYPE_MASK 0x1UL
109#define ASSOC_ARRAY_PTR_LEAF_TYPE 0x0UL /* Points to leaf (or nowhere) */
110#define ASSOC_ARRAY_PTR_META_TYPE 0x1UL /* Points to node or shortcut */
111#define ASSOC_ARRAY_PTR_SUBTYPE_MASK 0x2UL
112#define ASSOC_ARRAY_PTR_NODE_SUBTYPE 0x0UL
113#define ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE 0x2UL
114
115static inline bool assoc_array_ptr_is_meta(const struct assoc_array_ptr *x)
116{
117 return (unsigned long)x & ASSOC_ARRAY_PTR_TYPE_MASK;
118}
119static inline bool assoc_array_ptr_is_leaf(const struct assoc_array_ptr *x)
120{
121 return !assoc_array_ptr_is_meta(x);
122}
123static inline bool assoc_array_ptr_is_shortcut(const struct assoc_array_ptr *x)
124{
125 return (unsigned long)x & ASSOC_ARRAY_PTR_SUBTYPE_MASK;
126}
127static inline bool assoc_array_ptr_is_node(const struct assoc_array_ptr *x)
128{
129 return !assoc_array_ptr_is_shortcut(x);
130}
131
132static inline void *assoc_array_ptr_to_leaf(const struct assoc_array_ptr *x)
133{
134 return (void *)((unsigned long)x & ~ASSOC_ARRAY_PTR_TYPE_MASK);
135}
136
137static inline
138unsigned long __assoc_array_ptr_to_meta(const struct assoc_array_ptr *x)
139{
140 return (unsigned long)x &
141 ~(ASSOC_ARRAY_PTR_SUBTYPE_MASK | ASSOC_ARRAY_PTR_TYPE_MASK);
142}
143static inline
144struct assoc_array_node *assoc_array_ptr_to_node(const struct assoc_array_ptr *x)
145{
146 return (struct assoc_array_node *)__assoc_array_ptr_to_meta(x);
147}
148static inline
149struct assoc_array_shortcut *assoc_array_ptr_to_shortcut(const struct assoc_array_ptr *x)
150{
151 return (struct assoc_array_shortcut *)__assoc_array_ptr_to_meta(x);
152}
153
154static inline
155struct assoc_array_ptr *__assoc_array_x_to_ptr(const void *p, unsigned long t)
156{
157 return (struct assoc_array_ptr *)((unsigned long)p | t);
158}
159static inline
160struct assoc_array_ptr *assoc_array_leaf_to_ptr(const void *p)
161{
162 return __assoc_array_x_to_ptr(p, ASSOC_ARRAY_PTR_LEAF_TYPE);
163}
164static inline
165struct assoc_array_ptr *assoc_array_node_to_ptr(const struct assoc_array_node *p)
166{
167 return __assoc_array_x_to_ptr(
168 p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_NODE_SUBTYPE);
169}
170static inline
171struct assoc_array_ptr *assoc_array_shortcut_to_ptr(const struct assoc_array_shortcut *p)
172{
173 return __assoc_array_x_to_ptr(
174 p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE);
175}
176
177#endif /* CONFIG_ASSOCIATIVE_ARRAY */
178#endif /* _LINUX_ASSOC_ARRAY_PRIV_H */
179