1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
|
/*
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
* Copyright (C) 2006 Nick Piggin
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef _LINUX_RADIX_TREE_H
#define _LINUX_RADIX_TREE_H
#include <linux/preempt.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/rcupdate.h>
/*
* An indirect pointer (root->rnode pointing to a radix_tree_node, rather
* than a data item) is signalled by the low bit set in the root->rnode
* pointer.
*
* In this case root->height is > 0, but the indirect pointer tests are
* needed for RCU lookups (because root->height is unreliable). The only
* time callers need worry about this is when doing a lookup_slot under
* RCU.
*
* Indirect pointer in fact is also used to tag the last pointer of a node
* when it is shrunk, before we rcu free the node. See shrink code for
* details.
*/
#define RADIX_TREE_INDIRECT_PTR 1
#define radix_tree_indirect_to_ptr(ptr) \
radix_tree_indirect_to_ptr((void __force *)(ptr))
static inline int radix_tree_is_indirect_ptr(void *ptr)
{
return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
}
/*** radix-tree API starts here ***/
#define RADIX_TREE_MAX_TAGS 3
/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
struct radix_tree_root {
unsigned int height;
gfp_t gfp_mask;
struct radix_tree_node __rcu *rnode;
};
#define RADIX_TREE_INIT(mask) { \
.height = 0, \
.gfp_mask = (mask), \
.rnode = NULL, \
}
#define RADIX_TREE(name, mask) \
struct radix_tree_root name = RADIX_TREE_INIT(mask)
#define INIT_RADIX_TREE(root, mask) \
do { \
(root)->height = 0; \
(root)->gfp_mask = (mask); \
(root)->rnode = NULL; \
} while (0)
/**
* Radix-tree synchronization
*
* The radix-tree API requires that users provide all synchronisation (with
* specific exceptions, noted below).
*
* Synchronization of access to the data items being stored in the tree, and
* management of their lifetimes must be completely managed by API users.
*
* For API usage, in general,
* - any function _modifying_ the tree or tags (inserting or deleting
* items, setting or clearing tags) must exclude other modifications, and
* exclude any functions reading the tree.
* - any function _reading_ the tree or tags (looking up items or tags,
* gang lookups) must exclude modifications to the tree, but may occur
* concurrently with other readers.
*
* The notable exceptions to this rule are the following functions:
* radix_tree_lookup
* radix_tree_lookup_slot
* radix_tree_tag_get
* radix_tree_gang_lookup
* radix_tree_gang_lookup_slot
* radix_tree_gang_lookup_tag
* radix_tree_gang_lookup_tag_slot
* radix_tree_tagged
*
* The first 7 functions are able to be called locklessly, using RCU. The
* caller must ensure calls to these functions are made within rcu_read_lock()
* regions. Other readers (lock-free or otherwise) and modifications may be
* running concurrently.
*
* It is still required that the caller manage the synchronization and lifetimes
* of the items. So if RCU lock-free lookups are used, typically this would mean
* that the items have their own locks, or are amenable to lock-free access; and
* that the items are freed by RCU (or only freed after having been deleted from
* the radix tree *and* a synchronize_rcu() grace period).
*
* (Note, rcu_assign_pointer and rcu_dereference are not needed to control
* access to data items when inserting into or looking up from the radix tree)
*
* Note that the value returned by radix_tree_tag_get() may not be relied upon
* if only the RCU read lock is held. Functions to set/clear tags and to
* delete nodes running concurrently with it may affect its result such that
* two consecutive reads in the same locked section may return different
* values. If reliability is required, modification functions must also be
* excluded from concurrency.
*
* radix_tree_tagged is able to be called without locking or RCU.
*/
/**
* radix_tree_deref_slot - dereference a slot
* @pslot: pointer to slot, returned by radix_tree_lookup_slot
* Returns: item that was stored in that slot with any direct pointer flag
* removed.
*
* For use with radix_tree_lookup_slot(). Caller must hold tree at least read
* locked across slot lookup and dereference. Not required if write lock is
* held (ie. items cannot be concurrently inserted).
*
* radix_tree_deref_retry must be used to confirm validity of the pointer if
* only the read lock is held.
*/
static inline void *radix_tree_deref_slot(void **pslot)
{
return rcu_dereference(*pslot);
}
/**
* radix_tree_deref_retry - check radix_tree_deref_slot
* @arg: pointer returned by radix_tree_deref_slot
* Returns: 0 if retry is not required, otherwise retry is required
*
* radix_tree_deref_retry must be used with radix_tree_deref_slot.
*/
static inline int radix_tree_deref_retry(void *arg)
{
return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
}
/**
* radix_tree_replace_slot - replace item in a slot
* @pslot: pointer to slot, returned by radix_tree_lookup_slot
* @item: new item to store in the slot.
*
* For use with radix_tree_lookup_slot(). Caller must hold tree write locked
* across slot lookup and replacement.
*/
static inline void radix_tree_replace_slot(void **pslot, void *item)
{
BUG_ON(radix_tree_is_indirect_ptr(item));
rcu_assign_pointer(*pslot, item);
}
int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
void *radix_tree_delete(struct radix_tree_root *, unsigned long);
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items);
unsigned int
radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results,
unsigned long first_index, unsigned int max_items);
unsigned long radix_tree_next_hole(struct radix_tree_root *root,
unsigned long index, unsigned long max_scan);
unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
unsigned long index, unsigned long max_scan);
int radix_tree_preload(gfp_t gfp_mask);
void radix_tree_init(void);
void *radix_tree_tag_set(struct radix_tree_root *root,
unsigned long index, unsigned int tag);
void *radix_tree_tag_clear(struct radix_tree_root *root,
unsigned long index, unsigned int tag);
int radix_tree_tag_get(struct radix_tree_root *root,
unsigned long index, unsigned int tag);
unsigned int
radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items,
unsigned int tag);
unsigned int
radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
unsigned long first_index, unsigned int max_items,
unsigned int tag);
unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
unsigned long *first_indexp, unsigned long last_index,
unsigned long nr_to_tag,
unsigned int fromtag, unsigned int totag);
int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
static inline void radix_tree_preload_end(void)
{
preempt_enable();
}
#endif /* _LINUX_RADIX_TREE_H */
|
