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Linux/include/linux/assoc_array_priv.h

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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  */
 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 
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 }
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 }
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 }
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 
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
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
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
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
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
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
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
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 

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