1 /* Private definitions for the generic associative array implementation.
2  *
3  * See Documentation/core-api/assoc_array.rst 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  */
32 struct 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  */
56 struct 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  */
67 struct 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  */
78 struct 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 
assoc_array_ptr_is_meta(const struct assoc_array_ptr * x)119 static 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 }
assoc_array_ptr_is_leaf(const struct assoc_array_ptr * x)123 static inline bool assoc_array_ptr_is_leaf(const struct assoc_array_ptr *x)
124 {
125 	return !assoc_array_ptr_is_meta(x);
126 }
assoc_array_ptr_is_shortcut(const struct assoc_array_ptr * x)127 static 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 }
assoc_array_ptr_is_node(const struct assoc_array_ptr * x)131 static inline bool assoc_array_ptr_is_node(const struct assoc_array_ptr *x)
132 {
133 	return !assoc_array_ptr_is_shortcut(x);
134 }
135 
assoc_array_ptr_to_leaf(const struct assoc_array_ptr * x)136 static 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 
141 static inline
__assoc_array_ptr_to_meta(const struct assoc_array_ptr * x)142 unsigned 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 }
147 static inline
assoc_array_ptr_to_node(const struct assoc_array_ptr * x)148 struct 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 }
152 static inline
assoc_array_ptr_to_shortcut(const struct assoc_array_ptr * x)153 struct 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 
158 static inline
__assoc_array_x_to_ptr(const void * p,unsigned long t)159 struct 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 }
163 static inline
assoc_array_leaf_to_ptr(const void * p)164 struct 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 }
168 static inline
assoc_array_node_to_ptr(const struct assoc_array_node * p)169 struct 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 }
174 static inline
assoc_array_shortcut_to_ptr(const struct assoc_array_shortcut * p)175 struct 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 */
183