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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Copyright (C) 2001 Momchil Velikov
3 * Portions Copyright (C) 2001 Christoph Hellwig
Nick Piggin7cf9c2c2006-12-06 20:33:44 -08004 * Copyright (C) 2006 Nick Piggin
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 *
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>
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080025#include <linux/kernel.h>
26#include <linux/rcupdate.h>
27
28/*
Nick Pigginc0bc9872007-10-16 01:24:42 -070029 * 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.
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080032 *
Nick Pigginc0bc9872007-10-16 01:24:42 -070033 * 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.
Nick Piggin27d20fd2010-11-11 14:05:19 -080037 *
38 * Indirect pointer in fact is also used to tag the last pointer of a node
39 * when it is shrunk, before we rcu free the node. See shrink code for
40 * details.
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080041 */
Nick Pigginc0bc9872007-10-16 01:24:42 -070042#define RADIX_TREE_INDIRECT_PTR 1
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080043
Arnd Bergmanna1115572010-02-25 23:43:52 +010044#define radix_tree_indirect_to_ptr(ptr) \
45 radix_tree_indirect_to_ptr((void __force *)(ptr))
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080046
Nick Pigginc0bc9872007-10-16 01:24:42 -070047static inline int radix_tree_is_indirect_ptr(void *ptr)
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080048{
Nick Pigginc0bc9872007-10-16 01:24:42 -070049 return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080050}
51
52/*** radix-tree API starts here ***/
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
Jan Karaf446daae2010-08-09 17:19:12 -070054#define RADIX_TREE_MAX_TAGS 3
Nick Piggin612d6c12006-06-23 02:03:22 -070055
56/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
Linus Torvalds1da177e2005-04-16 15:20:36 -070057struct radix_tree_root {
58 unsigned int height;
Al Virofd4f2df2005-10-21 03:18:50 -040059 gfp_t gfp_mask;
Arnd Bergmanna1115572010-02-25 23:43:52 +010060 struct radix_tree_node __rcu *rnode;
Linus Torvalds1da177e2005-04-16 15:20:36 -070061};
62
63#define RADIX_TREE_INIT(mask) { \
64 .height = 0, \
65 .gfp_mask = (mask), \
66 .rnode = NULL, \
67}
68
69#define RADIX_TREE(name, mask) \
70 struct radix_tree_root name = RADIX_TREE_INIT(mask)
71
72#define INIT_RADIX_TREE(root, mask) \
73do { \
74 (root)->height = 0; \
75 (root)->gfp_mask = (mask); \
76 (root)->rnode = NULL; \
77} while (0)
78
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080079/**
80 * Radix-tree synchronization
81 *
82 * The radix-tree API requires that users provide all synchronisation (with
83 * specific exceptions, noted below).
84 *
85 * Synchronization of access to the data items being stored in the tree, and
86 * management of their lifetimes must be completely managed by API users.
87 *
88 * For API usage, in general,
Michael Opdenacker59c51592007-05-09 08:57:56 +020089 * - any function _modifying_ the tree or tags (inserting or deleting
Tim Peppereb8dc5e2008-02-03 16:12:47 +020090 * items, setting or clearing tags) must exclude other modifications, and
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080091 * exclude any functions reading the tree.
Michael Opdenacker59c51592007-05-09 08:57:56 +020092 * - any function _reading_ the tree or tags (looking up items or tags,
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080093 * gang lookups) must exclude modifications to the tree, but may occur
94 * concurrently with other readers.
95 *
96 * The notable exceptions to this rule are the following functions:
97 * radix_tree_lookup
Nick Piggin47feff22008-07-25 19:45:29 -070098 * radix_tree_lookup_slot
Nick Piggin7cf9c2c2006-12-06 20:33:44 -080099 * radix_tree_tag_get
100 * radix_tree_gang_lookup
Nick Piggin47feff22008-07-25 19:45:29 -0700101 * radix_tree_gang_lookup_slot
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800102 * radix_tree_gang_lookup_tag
Nick Piggin47feff22008-07-25 19:45:29 -0700103 * radix_tree_gang_lookup_tag_slot
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800104 * radix_tree_tagged
105 *
Nick Piggin47feff22008-07-25 19:45:29 -0700106 * The first 7 functions are able to be called locklessly, using RCU. The
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800107 * caller must ensure calls to these functions are made within rcu_read_lock()
108 * regions. Other readers (lock-free or otherwise) and modifications may be
109 * running concurrently.
110 *
111 * It is still required that the caller manage the synchronization and lifetimes
112 * of the items. So if RCU lock-free lookups are used, typically this would mean
113 * that the items have their own locks, or are amenable to lock-free access; and
114 * that the items are freed by RCU (or only freed after having been deleted from
115 * the radix tree *and* a synchronize_rcu() grace period).
116 *
117 * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
118 * access to data items when inserting into or looking up from the radix tree)
119 *
David Howellsce826532010-04-06 22:36:20 +0100120 * Note that the value returned by radix_tree_tag_get() may not be relied upon
121 * if only the RCU read lock is held. Functions to set/clear tags and to
122 * delete nodes running concurrently with it may affect its result such that
123 * two consecutive reads in the same locked section may return different
124 * values. If reliability is required, modification functions must also be
125 * excluded from concurrency.
126 *
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800127 * radix_tree_tagged is able to be called without locking or RCU.
128 */
129
130/**
131 * radix_tree_deref_slot - dereference a slot
132 * @pslot: pointer to slot, returned by radix_tree_lookup_slot
133 * Returns: item that was stored in that slot with any direct pointer flag
134 * removed.
135 *
136 * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
Nick Piggin27d20fd2010-11-11 14:05:19 -0800137 * locked across slot lookup and dereference. Not required if write lock is
138 * held (ie. items cannot be concurrently inserted).
139 *
140 * radix_tree_deref_retry must be used to confirm validity of the pointer if
141 * only the read lock is held.
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800142 */
143static inline void *radix_tree_deref_slot(void **pslot)
144{
Nick Piggin27d20fd2010-11-11 14:05:19 -0800145 return rcu_dereference(*pslot);
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800146}
Nick Piggin27d20fd2010-11-11 14:05:19 -0800147
148/**
Mel Gorman29c1f672011-01-13 15:47:21 -0800149 * radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held
150 * @pslot: pointer to slot, returned by radix_tree_lookup_slot
151 * Returns: item that was stored in that slot with any direct pointer flag
152 * removed.
153 *
154 * Similar to radix_tree_deref_slot but only used during migration when a pages
155 * mapping is being moved. The caller does not hold the RCU read lock but it
156 * must hold the tree lock to prevent parallel updates.
157 */
158static inline void *radix_tree_deref_slot_protected(void **pslot,
159 spinlock_t *treelock)
160{
161 return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
162}
163
164/**
Nick Piggin27d20fd2010-11-11 14:05:19 -0800165 * radix_tree_deref_retry - check radix_tree_deref_slot
166 * @arg: pointer returned by radix_tree_deref_slot
167 * Returns: 0 if retry is not required, otherwise retry is required
168 *
169 * radix_tree_deref_retry must be used with radix_tree_deref_slot.
170 */
171static inline int radix_tree_deref_retry(void *arg)
172{
173 return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
174}
175
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800176/**
177 * radix_tree_replace_slot - replace item in a slot
178 * @pslot: pointer to slot, returned by radix_tree_lookup_slot
179 * @item: new item to store in the slot.
180 *
181 * For use with radix_tree_lookup_slot(). Caller must hold tree write locked
182 * across slot lookup and replacement.
183 */
184static inline void radix_tree_replace_slot(void **pslot, void *item)
185{
Nick Pigginc0bc9872007-10-16 01:24:42 -0700186 BUG_ON(radix_tree_is_indirect_ptr(item));
187 rcu_assign_pointer(*pslot, item);
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800188}
189
Linus Torvalds1da177e2005-04-16 15:20:36 -0700190int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
191void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
Hans Reisera4331362005-11-07 00:59:29 -0800192void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193void *radix_tree_delete(struct radix_tree_root *, unsigned long);
194unsigned int
195radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
196 unsigned long first_index, unsigned int max_items);
Nick Piggin47feff22008-07-25 19:45:29 -0700197unsigned int
198radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results,
199 unsigned long first_index, unsigned int max_items);
Fengguang Wu6df8ba42007-10-16 01:24:33 -0700200unsigned long radix_tree_next_hole(struct radix_tree_root *root,
201 unsigned long index, unsigned long max_scan);
Wu Fengguangdc566122009-06-16 15:31:32 -0700202unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
203 unsigned long index, unsigned long max_scan);
Al Virodd0fc662005-10-07 07:46:04 +0100204int radix_tree_preload(gfp_t gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205void radix_tree_init(void);
206void *radix_tree_tag_set(struct radix_tree_root *root,
Jonathan Corbetdaff89f2006-03-25 03:08:05 -0800207 unsigned long index, unsigned int tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208void *radix_tree_tag_clear(struct radix_tree_root *root,
Jonathan Corbetdaff89f2006-03-25 03:08:05 -0800209 unsigned long index, unsigned int tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210int radix_tree_tag_get(struct radix_tree_root *root,
Jonathan Corbetdaff89f2006-03-25 03:08:05 -0800211 unsigned long index, unsigned int tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212unsigned int
213radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
Jonathan Corbetdaff89f2006-03-25 03:08:05 -0800214 unsigned long first_index, unsigned int max_items,
215 unsigned int tag);
Nick Piggin47feff22008-07-25 19:45:29 -0700216unsigned int
217radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
218 unsigned long first_index, unsigned int max_items,
219 unsigned int tag);
Jan Karaebf8aa42010-08-09 17:19:11 -0700220unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
221 unsigned long *first_indexp, unsigned long last_index,
222 unsigned long nr_to_tag,
223 unsigned int fromtag, unsigned int totag);
Jonathan Corbetdaff89f2006-03-25 03:08:05 -0800224int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225
226static inline void radix_tree_preload_end(void)
227{
228 preempt_enable();
229}
230
231#endif /* _LINUX_RADIX_TREE_H */