Add linux-next specific files for 20110831
[linux-2.6/next.git] / include / linux / radix-tree.h
blob9d4539c52e53e5f3635345260049999ba90d735e
1 /*
2 * Copyright (C) 2001 Momchil Velikov
3 * Portions Copyright (C) 2001 Christoph Hellwig
4 * Copyright (C) 2006 Nick Piggin
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.
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.
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.
20 #ifndef _LINUX_RADIX_TREE_H
21 #define _LINUX_RADIX_TREE_H
23 #include <linux/preempt.h>
24 #include <linux/types.h>
25 #include <linux/kernel.h>
26 #include <linux/rcupdate.h>
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.
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.
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.
42 #define RADIX_TREE_INDIRECT_PTR 1
44 * A common use of the radix tree is to store pointers to struct pages;
45 * but shmem/tmpfs needs also to store swap entries in the same tree:
46 * those are marked as exceptional entries to distinguish them.
47 * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
49 #define RADIX_TREE_EXCEPTIONAL_ENTRY 2
50 #define RADIX_TREE_EXCEPTIONAL_SHIFT 2
52 #define radix_tree_indirect_to_ptr(ptr) \
53 radix_tree_indirect_to_ptr((void __force *)(ptr))
55 static inline int radix_tree_is_indirect_ptr(void *ptr)
57 return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
60 /*** radix-tree API starts here ***/
62 #define RADIX_TREE_MAX_TAGS 3
64 /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
65 struct radix_tree_root {
66 unsigned int height;
67 gfp_t gfp_mask;
68 struct radix_tree_node __rcu *rnode;
71 #define RADIX_TREE_INIT(mask) { \
72 .height = 0, \
73 .gfp_mask = (mask), \
74 .rnode = NULL, \
77 #define RADIX_TREE(name, mask) \
78 struct radix_tree_root name = RADIX_TREE_INIT(mask)
80 #define INIT_RADIX_TREE(root, mask) \
81 do { \
82 (root)->height = 0; \
83 (root)->gfp_mask = (mask); \
84 (root)->rnode = NULL; \
85 } while (0)
87 /**
88 * Radix-tree synchronization
90 * The radix-tree API requires that users provide all synchronisation (with
91 * specific exceptions, noted below).
93 * Synchronization of access to the data items being stored in the tree, and
94 * management of their lifetimes must be completely managed by API users.
96 * For API usage, in general,
97 * - any function _modifying_ the tree or tags (inserting or deleting
98 * items, setting or clearing tags) must exclude other modifications, and
99 * exclude any functions reading the tree.
100 * - any function _reading_ the tree or tags (looking up items or tags,
101 * gang lookups) must exclude modifications to the tree, but may occur
102 * concurrently with other readers.
104 * The notable exceptions to this rule are the following functions:
105 * radix_tree_lookup
106 * radix_tree_lookup_slot
107 * radix_tree_tag_get
108 * radix_tree_gang_lookup
109 * radix_tree_gang_lookup_slot
110 * radix_tree_gang_lookup_tag
111 * radix_tree_gang_lookup_tag_slot
112 * radix_tree_tagged
114 * The first 7 functions are able to be called locklessly, using RCU. The
115 * caller must ensure calls to these functions are made within rcu_read_lock()
116 * regions. Other readers (lock-free or otherwise) and modifications may be
117 * running concurrently.
119 * It is still required that the caller manage the synchronization and lifetimes
120 * of the items. So if RCU lock-free lookups are used, typically this would mean
121 * that the items have their own locks, or are amenable to lock-free access; and
122 * that the items are freed by RCU (or only freed after having been deleted from
123 * the radix tree *and* a synchronize_rcu() grace period).
125 * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
126 * access to data items when inserting into or looking up from the radix tree)
128 * Note that the value returned by radix_tree_tag_get() may not be relied upon
129 * if only the RCU read lock is held. Functions to set/clear tags and to
130 * delete nodes running concurrently with it may affect its result such that
131 * two consecutive reads in the same locked section may return different
132 * values. If reliability is required, modification functions must also be
133 * excluded from concurrency.
135 * radix_tree_tagged is able to be called without locking or RCU.
139 * radix_tree_deref_slot - dereference a slot
140 * @pslot: pointer to slot, returned by radix_tree_lookup_slot
141 * Returns: item that was stored in that slot with any direct pointer flag
142 * removed.
144 * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
145 * locked across slot lookup and dereference. Not required if write lock is
146 * held (ie. items cannot be concurrently inserted).
148 * radix_tree_deref_retry must be used to confirm validity of the pointer if
149 * only the read lock is held.
151 static inline void *radix_tree_deref_slot(void **pslot)
153 return rcu_dereference(*pslot);
157 * radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held
158 * @pslot: pointer to slot, returned by radix_tree_lookup_slot
159 * Returns: item that was stored in that slot with any direct pointer flag
160 * removed.
162 * Similar to radix_tree_deref_slot but only used during migration when a pages
163 * mapping is being moved. The caller does not hold the RCU read lock but it
164 * must hold the tree lock to prevent parallel updates.
166 static inline void *radix_tree_deref_slot_protected(void **pslot,
167 spinlock_t *treelock)
169 return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
173 * radix_tree_deref_retry - check radix_tree_deref_slot
174 * @arg: pointer returned by radix_tree_deref_slot
175 * Returns: 0 if retry is not required, otherwise retry is required
177 * radix_tree_deref_retry must be used with radix_tree_deref_slot.
179 static inline int radix_tree_deref_retry(void *arg)
181 return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
185 * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
186 * @arg: value returned by radix_tree_deref_slot
187 * Returns: 0 if well-aligned pointer, non-0 if exceptional entry.
189 static inline int radix_tree_exceptional_entry(void *arg)
191 /* Not unlikely because radix_tree_exception often tested first */
192 return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
196 * radix_tree_exception - radix_tree_deref_slot returned either exception?
197 * @arg: value returned by radix_tree_deref_slot
198 * Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
200 static inline int radix_tree_exception(void *arg)
202 return unlikely((unsigned long)arg &
203 (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY));
207 * radix_tree_replace_slot - replace item in a slot
208 * @pslot: pointer to slot, returned by radix_tree_lookup_slot
209 * @item: new item to store in the slot.
211 * For use with radix_tree_lookup_slot(). Caller must hold tree write locked
212 * across slot lookup and replacement.
214 static inline void radix_tree_replace_slot(void **pslot, void *item)
216 BUG_ON(radix_tree_is_indirect_ptr(item));
217 rcu_assign_pointer(*pslot, item);
220 int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
221 void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
222 void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
223 void *radix_tree_delete(struct radix_tree_root *, unsigned long);
224 unsigned int
225 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
226 unsigned long first_index, unsigned int max_items);
227 unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root,
228 void ***results, unsigned long *indices,
229 unsigned long first_index, unsigned int max_items);
230 unsigned long radix_tree_next_hole(struct radix_tree_root *root,
231 unsigned long index, unsigned long max_scan);
232 unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
233 unsigned long index, unsigned long max_scan);
234 int radix_tree_preload(gfp_t gfp_mask);
235 void radix_tree_init(void);
236 void *radix_tree_tag_set(struct radix_tree_root *root,
237 unsigned long index, unsigned int tag);
238 void *radix_tree_tag_clear(struct radix_tree_root *root,
239 unsigned long index, unsigned int tag);
240 int radix_tree_tag_get(struct radix_tree_root *root,
241 unsigned long index, unsigned int tag);
242 unsigned int
243 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
244 unsigned long first_index, unsigned int max_items,
245 unsigned int tag);
246 unsigned int
247 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
248 unsigned long first_index, unsigned int max_items,
249 unsigned int tag);
250 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
251 unsigned long *first_indexp, unsigned long last_index,
252 unsigned long nr_to_tag,
253 unsigned int fromtag, unsigned int totag);
254 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
255 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item);
257 static inline void radix_tree_preload_end(void)
259 preempt_enable();
262 #endif /* _LINUX_RADIX_TREE_H */