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  */
28 struct 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  */
52 struct 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  */
63 struct 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  */
74 struct 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 
assoc_array_ptr_is_meta(const struct assoc_array_ptr * x)115 static 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 }
assoc_array_ptr_is_leaf(const struct assoc_array_ptr * x)119 static inline bool assoc_array_ptr_is_leaf(const struct assoc_array_ptr *x)
120 {
121 	return !assoc_array_ptr_is_meta(x);
122 }
assoc_array_ptr_is_shortcut(const struct assoc_array_ptr * x)123 static 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 }
assoc_array_ptr_is_node(const struct assoc_array_ptr * x)127 static inline bool assoc_array_ptr_is_node(const struct assoc_array_ptr *x)
128 {
129 	return !assoc_array_ptr_is_shortcut(x);
130 }
131 
assoc_array_ptr_to_leaf(const struct assoc_array_ptr * x)132 static 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 
137 static inline
__assoc_array_ptr_to_meta(const struct assoc_array_ptr * x)138 unsigned 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 }
143 static inline
assoc_array_ptr_to_node(const struct assoc_array_ptr * x)144 struct 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 }
148 static inline
assoc_array_ptr_to_shortcut(const struct assoc_array_ptr * x)149 struct 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 
154 static inline
__assoc_array_x_to_ptr(const void * p,unsigned long t)155 struct 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 }
159 static inline
assoc_array_leaf_to_ptr(const void * p)160 struct 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 }
164 static inline
assoc_array_node_to_ptr(const struct assoc_array_node * p)165 struct 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 }
170 static inline
assoc_array_shortcut_to_ptr(const struct assoc_array_shortcut * p)171 struct 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