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1 | /* |
2 | * Copyright (C) 2001 Momchil Velikov |
3 | * Portions Copyright (C) 2001 Christoph Hellwig |
4 | * Copyright (C) 2006 Nick Piggin |
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> |
25 | #include <linux/kernel.h> |
26 | #include <linux/rcupdate.h> |
27 | |
28 | /* |
29 | * An indirect pointer (root->rnode pointing to a radix_tree_node, rather |
30 | * than a data item) is signalled by the low bit set in the root->rnode |
31 | * pointer. |
32 | * |
33 | * In this case root->height is > 0, but the indirect pointer tests are |
34 | * needed for RCU lookups (because root->height is unreliable). The only |
35 | * time callers need worry about this is when doing a lookup_slot under |
36 | * RCU. |
37 | */ |
38 | #define RADIX_TREE_INDIRECT_PTR 1 |
39 | #define RADIX_TREE_RETRY ((void *)-1UL) |
40 | |
41 | static inline void *radix_tree_ptr_to_indirect(void *ptr) |
42 | { |
43 | return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR); |
44 | } |
45 | |
46 | static inline void *radix_tree_indirect_to_ptr(void *ptr) |
47 | { |
48 | return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR); |
49 | } |
50 | |
51 | static inline int radix_tree_is_indirect_ptr(void *ptr) |
52 | { |
53 | return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); |
54 | } |
55 | |
56 | /*** radix-tree API starts here ***/ |
57 | |
58 | #define RADIX_TREE_MAX_TAGS 2 |
59 | |
60 | /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */ |
61 | struct radix_tree_root { |
62 | unsigned int height; |
63 | gfp_t gfp_mask; |
64 | struct radix_tree_node *rnode; |
65 | }; |
66 | |
67 | #define RADIX_TREE_INIT(mask) { \ |
68 | .height = 0, \ |
69 | .gfp_mask = (mask), \ |
70 | .rnode = NULL, \ |
71 | } |
72 | |
73 | #define RADIX_TREE(name, mask) \ |
74 | struct radix_tree_root name = RADIX_TREE_INIT(mask) |
75 | |
76 | #define INIT_RADIX_TREE(root, mask) \ |
77 | do { \ |
78 | (root)->height = 0; \ |
79 | (root)->gfp_mask = (mask); \ |
80 | (root)->rnode = NULL; \ |
81 | } while (0) |
82 | |
83 | /** |
84 | * Radix-tree synchronization |
85 | * |
86 | * The radix-tree API requires that users provide all synchronisation (with |
87 | * specific exceptions, noted below). |
88 | * |
89 | * Synchronization of access to the data items being stored in the tree, and |
90 | * management of their lifetimes must be completely managed by API users. |
91 | * |
92 | * For API usage, in general, |
93 | * - any function _modifying_ the tree or tags (inserting or deleting |
94 | * items, setting or clearing tags) must exclude other modifications, and |
95 | * exclude any functions reading the tree. |
96 | * - any function _reading_ the tree or tags (looking up items or tags, |
97 | * gang lookups) must exclude modifications to the tree, but may occur |
98 | * concurrently with other readers. |
99 | * |
100 | * The notable exceptions to this rule are the following functions: |
101 | * radix_tree_lookup |
102 | * radix_tree_lookup_slot |
103 | * radix_tree_tag_get |
104 | * radix_tree_gang_lookup |
105 | * radix_tree_gang_lookup_slot |
106 | * radix_tree_gang_lookup_tag |
107 | * radix_tree_gang_lookup_tag_slot |
108 | * radix_tree_tagged |
109 | * |
110 | * The first 7 functions are able to be called locklessly, using RCU. The |
111 | * caller must ensure calls to these functions are made within rcu_read_lock() |
112 | * regions. Other readers (lock-free or otherwise) and modifications may be |
113 | * running concurrently. |
114 | * |
115 | * It is still required that the caller manage the synchronization and lifetimes |
116 | * of the items. So if RCU lock-free lookups are used, typically this would mean |
117 | * that the items have their own locks, or are amenable to lock-free access; and |
118 | * that the items are freed by RCU (or only freed after having been deleted from |
119 | * the radix tree *and* a synchronize_rcu() grace period). |
120 | * |
121 | * (Note, rcu_assign_pointer and rcu_dereference are not needed to control |
122 | * access to data items when inserting into or looking up from the radix tree) |
123 | * |
124 | * Note that the value returned by radix_tree_tag_get() may not be relied upon |
125 | * if only the RCU read lock is held. Functions to set/clear tags and to |
126 | * delete nodes running concurrently with it may affect its result such that |
127 | * two consecutive reads in the same locked section may return different |
128 | * values. If reliability is required, modification functions must also be |
129 | * excluded from concurrency. |
130 | * |
131 | * radix_tree_tagged is able to be called without locking or RCU. |
132 | */ |
133 | |
134 | /** |
135 | * radix_tree_deref_slot - dereference a slot |
136 | * @pslot: pointer to slot, returned by radix_tree_lookup_slot |
137 | * Returns: item that was stored in that slot with any direct pointer flag |
138 | * removed. |
139 | * |
140 | * For use with radix_tree_lookup_slot(). Caller must hold tree at least read |
141 | * locked across slot lookup and dereference. More likely, will be used with |
142 | * radix_tree_replace_slot(), as well, so caller will hold tree write locked. |
143 | */ |
144 | static inline void *radix_tree_deref_slot(void **pslot) |
145 | { |
146 | void *ret = rcu_dereference(*pslot); |
147 | if (unlikely(radix_tree_is_indirect_ptr(ret))) |
148 | ret = RADIX_TREE_RETRY; |
149 | return ret; |
150 | } |
151 | /** |
152 | * radix_tree_replace_slot - replace item in a slot |
153 | * @pslot: pointer to slot, returned by radix_tree_lookup_slot |
154 | * @item: new item to store in the slot. |
155 | * |
156 | * For use with radix_tree_lookup_slot(). Caller must hold tree write locked |
157 | * across slot lookup and replacement. |
158 | */ |
159 | static inline void radix_tree_replace_slot(void **pslot, void *item) |
160 | { |
161 | BUG_ON(radix_tree_is_indirect_ptr(item)); |
162 | rcu_assign_pointer(*pslot, item); |
163 | } |
164 | |
165 | int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); |
166 | void *radix_tree_lookup(struct radix_tree_root *, unsigned long); |
167 | void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); |
168 | void *radix_tree_delete(struct radix_tree_root *, unsigned long); |
169 | unsigned int |
170 | radix_tree_gang_lookup(struct radix_tree_root *root, void **results, |
171 | unsigned long first_index, unsigned int max_items); |
172 | unsigned int |
173 | radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results, |
174 | unsigned long first_index, unsigned int max_items); |
175 | unsigned long radix_tree_next_hole(struct radix_tree_root *root, |
176 | unsigned long index, unsigned long max_scan); |
177 | unsigned long radix_tree_prev_hole(struct radix_tree_root *root, |
178 | unsigned long index, unsigned long max_scan); |
179 | int radix_tree_preload(gfp_t gfp_mask); |
180 | void radix_tree_init(void); |
181 | void *radix_tree_tag_set(struct radix_tree_root *root, |
182 | unsigned long index, unsigned int tag); |
183 | void *radix_tree_tag_clear(struct radix_tree_root *root, |
184 | unsigned long index, unsigned int tag); |
185 | int radix_tree_tag_get(struct radix_tree_root *root, |
186 | unsigned long index, unsigned int tag); |
187 | unsigned int |
188 | radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, |
189 | unsigned long first_index, unsigned int max_items, |
190 | unsigned int tag); |
191 | unsigned int |
192 | radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, |
193 | unsigned long first_index, unsigned int max_items, |
194 | unsigned int tag); |
195 | int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag); |
196 | |
197 | static inline void radix_tree_preload_end(void) |
198 | { |
199 | preempt_enable(); |
200 | } |
201 | |
202 | #endif /* _LINUX_RADIX_TREE_H */ |
203 |
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