Line data Source code
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 2 :
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 : * radix_tree_tagged is able to be called without locking or RCU.
125 : */
126 :
127 : /**
128 : * radix_tree_deref_slot - dereference a slot
129 : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
130 : * Returns: item that was stored in that slot with any direct pointer flag
131 : * removed.
132 : *
133 : * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
134 : * locked across slot lookup and dereference. More likely, will be used with
135 : * radix_tree_replace_slot(), as well, so caller will hold tree write locked.
136 : */
137 : static inline void *radix_tree_deref_slot(void **pslot)
138 : {
139 : void *ret = rcu_dereference(*pslot);
140 : if (unlikely(radix_tree_is_indirect_ptr(ret)))
141 : ret = RADIX_TREE_RETRY;
142 : return ret;
143 : }
144 : /**
145 : * radix_tree_replace_slot - replace item in a slot
146 : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
147 : * @item: new item to store in the slot.
148 : *
149 : * For use with radix_tree_lookup_slot(). Caller must hold tree write locked
150 : * across slot lookup and replacement.
151 : */
152 : static inline void radix_tree_replace_slot(void **pslot, void *item)
153 : {
154 : BUG_ON(radix_tree_is_indirect_ptr(item));
155 : rcu_assign_pointer(*pslot, item);
156 : }
157 :
158 : int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
159 : void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
160 : void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
161 : void *radix_tree_delete(struct radix_tree_root *, unsigned long);
162 : unsigned int
163 : radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
164 : unsigned long first_index, unsigned int max_items);
165 : unsigned int
166 : radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results,
167 : unsigned long first_index, unsigned int max_items);
168 : unsigned long radix_tree_next_hole(struct radix_tree_root *root,
169 : unsigned long index, unsigned long max_scan);
170 : unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
171 : unsigned long index, unsigned long max_scan);
172 : int radix_tree_preload(gfp_t gfp_mask);
173 : void radix_tree_init(void);
174 : void *radix_tree_tag_set(struct radix_tree_root *root,
175 : unsigned long index, unsigned int tag);
176 : void *radix_tree_tag_clear(struct radix_tree_root *root,
177 : unsigned long index, unsigned int tag);
178 : int radix_tree_tag_get(struct radix_tree_root *root,
179 : unsigned long index, unsigned int tag);
180 : unsigned int
181 : radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
182 : unsigned long first_index, unsigned int max_items,
183 : unsigned int tag);
184 : unsigned int
185 : radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
186 : unsigned long first_index, unsigned int max_items,
187 : unsigned int tag);
188 : int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
189 :
190 : static inline void radix_tree_preload_end(void)
191 : {
192 : preempt_enable();
193 2 : }
194 :
195 : #endif /* _LINUX_RADIX_TREE_H */
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