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1da177e4 LT |
1 | /* |
2 | * Copyright (C) 2001 Momchil Velikov | |
3 | * Portions Copyright (C) 2001 Christoph Hellwig | |
7cf9c2c7 | 4 | * Copyright (C) 2006 Nick Piggin |
1da177e4 LT |
5 | * |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public License as | |
8 | * published by the Free Software Foundation; either version 2, or (at | |
9 | * your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, but | |
12 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program; if not, write to the Free Software | |
18 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
19 | */ | |
20 | #ifndef _LINUX_RADIX_TREE_H | |
21 | #define _LINUX_RADIX_TREE_H | |
22 | ||
23 | #include <linux/preempt.h> | |
24 | #include <linux/types.h> | |
7cf9c2c7 NP |
25 | #include <linux/kernel.h> |
26 | #include <linux/rcupdate.h> | |
27 | ||
28 | /* | |
29 | * A direct pointer (root->rnode pointing directly to a data item, | |
30 | * rather than another radix_tree_node) is signalled by the low bit | |
31 | * set in the root->rnode pointer. | |
32 | * | |
33 | * In this case root->height is also NULL, but the direct pointer tests are | |
34 | * needed for RCU lookups when root->height is unreliable. | |
35 | */ | |
36 | #define RADIX_TREE_DIRECT_PTR 1 | |
37 | ||
38 | static inline void *radix_tree_ptr_to_direct(void *ptr) | |
39 | { | |
40 | return (void *)((unsigned long)ptr | RADIX_TREE_DIRECT_PTR); | |
41 | } | |
42 | ||
43 | static inline void *radix_tree_direct_to_ptr(void *ptr) | |
44 | { | |
45 | return (void *)((unsigned long)ptr & ~RADIX_TREE_DIRECT_PTR); | |
46 | } | |
47 | ||
48 | static inline int radix_tree_is_direct_ptr(void *ptr) | |
49 | { | |
50 | return (int)((unsigned long)ptr & RADIX_TREE_DIRECT_PTR); | |
51 | } | |
52 | ||
53 | /*** radix-tree API starts here ***/ | |
1da177e4 | 54 | |
612d6c19 NP |
55 | #define RADIX_TREE_MAX_TAGS 2 |
56 | ||
57 | /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */ | |
1da177e4 LT |
58 | struct radix_tree_root { |
59 | unsigned int height; | |
fd4f2df2 | 60 | gfp_t gfp_mask; |
1da177e4 LT |
61 | struct radix_tree_node *rnode; |
62 | }; | |
63 | ||
64 | #define RADIX_TREE_INIT(mask) { \ | |
65 | .height = 0, \ | |
66 | .gfp_mask = (mask), \ | |
67 | .rnode = NULL, \ | |
68 | } | |
69 | ||
70 | #define RADIX_TREE(name, mask) \ | |
71 | struct radix_tree_root name = RADIX_TREE_INIT(mask) | |
72 | ||
73 | #define INIT_RADIX_TREE(root, mask) \ | |
74 | do { \ | |
75 | (root)->height = 0; \ | |
76 | (root)->gfp_mask = (mask); \ | |
77 | (root)->rnode = NULL; \ | |
78 | } while (0) | |
79 | ||
7cf9c2c7 NP |
80 | /** |
81 | * Radix-tree synchronization | |
82 | * | |
83 | * The radix-tree API requires that users provide all synchronisation (with | |
84 | * specific exceptions, noted below). | |
85 | * | |
86 | * Synchronization of access to the data items being stored in the tree, and | |
87 | * management of their lifetimes must be completely managed by API users. | |
88 | * | |
89 | * For API usage, in general, | |
90 | * - any function _modifying_ the the tree or tags (inserting or deleting | |
91 | * items, setting or clearing tags must exclude other modifications, and | |
92 | * exclude any functions reading the tree. | |
93 | * - any function _reading_ the the tree or tags (looking up items or tags, | |
94 | * gang lookups) must exclude modifications to the tree, but may occur | |
95 | * concurrently with other readers. | |
96 | * | |
97 | * The notable exceptions to this rule are the following functions: | |
98 | * radix_tree_lookup | |
99 | * radix_tree_tag_get | |
100 | * radix_tree_gang_lookup | |
101 | * radix_tree_gang_lookup_tag | |
102 | * radix_tree_tagged | |
103 | * | |
104 | * The first 4 functions are able to be called locklessly, using RCU. The | |
105 | * caller must ensure calls to these functions are made within rcu_read_lock() | |
106 | * regions. Other readers (lock-free or otherwise) and modifications may be | |
107 | * running concurrently. | |
108 | * | |
109 | * It is still required that the caller manage the synchronization and lifetimes | |
110 | * of the items. So if RCU lock-free lookups are used, typically this would mean | |
111 | * that the items have their own locks, or are amenable to lock-free access; and | |
112 | * that the items are freed by RCU (or only freed after having been deleted from | |
113 | * the radix tree *and* a synchronize_rcu() grace period). | |
114 | * | |
115 | * (Note, rcu_assign_pointer and rcu_dereference are not needed to control | |
116 | * access to data items when inserting into or looking up from the radix tree) | |
117 | * | |
118 | * radix_tree_tagged is able to be called without locking or RCU. | |
119 | */ | |
120 | ||
121 | /** | |
122 | * radix_tree_deref_slot - dereference a slot | |
123 | * @pslot: pointer to slot, returned by radix_tree_lookup_slot | |
124 | * Returns: item that was stored in that slot with any direct pointer flag | |
125 | * removed. | |
126 | * | |
127 | * For use with radix_tree_lookup_slot(). Caller must hold tree at least read | |
128 | * locked across slot lookup and dereference. More likely, will be used with | |
129 | * radix_tree_replace_slot(), as well, so caller will hold tree write locked. | |
130 | */ | |
131 | static inline void *radix_tree_deref_slot(void **pslot) | |
132 | { | |
133 | return radix_tree_direct_to_ptr(*pslot); | |
134 | } | |
135 | /** | |
136 | * radix_tree_replace_slot - replace item in a slot | |
137 | * @pslot: pointer to slot, returned by radix_tree_lookup_slot | |
138 | * @item: new item to store in the slot. | |
139 | * | |
140 | * For use with radix_tree_lookup_slot(). Caller must hold tree write locked | |
141 | * across slot lookup and replacement. | |
142 | */ | |
143 | static inline void radix_tree_replace_slot(void **pslot, void *item) | |
144 | { | |
145 | BUG_ON(radix_tree_is_direct_ptr(item)); | |
146 | rcu_assign_pointer(*pslot, | |
147 | (void *)((unsigned long)item | | |
148 | ((unsigned long)*pslot & RADIX_TREE_DIRECT_PTR))); | |
149 | } | |
150 | ||
1da177e4 LT |
151 | int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); |
152 | void *radix_tree_lookup(struct radix_tree_root *, unsigned long); | |
a4331366 | 153 | void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); |
1da177e4 LT |
154 | void *radix_tree_delete(struct radix_tree_root *, unsigned long); |
155 | unsigned int | |
156 | radix_tree_gang_lookup(struct radix_tree_root *root, void **results, | |
157 | unsigned long first_index, unsigned int max_items); | |
dd0fc66f | 158 | int radix_tree_preload(gfp_t gfp_mask); |
1da177e4 LT |
159 | void radix_tree_init(void); |
160 | void *radix_tree_tag_set(struct radix_tree_root *root, | |
daff89f3 | 161 | unsigned long index, unsigned int tag); |
1da177e4 | 162 | void *radix_tree_tag_clear(struct radix_tree_root *root, |
daff89f3 | 163 | unsigned long index, unsigned int tag); |
1da177e4 | 164 | int radix_tree_tag_get(struct radix_tree_root *root, |
daff89f3 | 165 | unsigned long index, unsigned int tag); |
1da177e4 LT |
166 | unsigned int |
167 | radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, | |
daff89f3 JC |
168 | unsigned long first_index, unsigned int max_items, |
169 | unsigned int tag); | |
170 | int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag); | |
1da177e4 LT |
171 | |
172 | static inline void radix_tree_preload_end(void) | |
173 | { | |
174 | preempt_enable(); | |
175 | } | |
176 | ||
177 | #endif /* _LINUX_RADIX_TREE_H */ |