2 * Resizable, Scalable, Concurrent Hash Table
4 * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
5 * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
7 * Based on the following paper by Josh Triplett, Paul E. McKenney
8 * and Jonathan Walpole:
9 * https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf
11 * Code partially derived from nft_hash
13 * This program is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU General Public License version 2 as
15 * published by the Free Software Foundation.
18 #ifndef _LINUX_RHASHTABLE_H
19 #define _LINUX_RHASHTABLE_H
21 #include <linux/compiler.h>
22 #include <linux/list_nulls.h>
23 #include <linux/workqueue.h>
24 #include <linux/mutex.h>
27 * The end of the chain is marked with a special nulls marks which has
28 * the following format:
30 * +-------+-----------------------------------------------------+-+
32 * +-------+-----------------------------------------------------+-+
34 * Base (4 bits) : Reserved to distinguish between multiple tables.
35 * Specified via &struct rhashtable_params.nulls_base.
36 * Hash (27 bits): Full hash (unmasked) of first element added to bucket
37 * 1 (1 bit) : Nulls marker (always set)
39 * The remaining bits of the next pointer remain unused for now.
41 #define RHT_BASE_BITS 4
42 #define RHT_HASH_BITS 27
43 #define RHT_BASE_SHIFT RHT_HASH_BITS
46 struct rhash_head __rcu *next;
50 * struct bucket_table - Table of hash buckets
51 * @size: Number of hash buckets
52 * @rehash: Current bucket being rehashed
53 * @hash_rnd: Random seed to fold into hash
54 * @locks_mask: Mask to apply before accessing locks[]
55 * @locks: Array of spinlocks protecting individual buckets
56 * @walkers: List of active walkers
57 * @rcu: RCU structure for freeing the table
58 * @future_tbl: Table under construction during rehashing
59 * @buckets: size * hash buckets
65 unsigned int locks_mask;
67 struct list_head walkers;
70 struct bucket_table __rcu *future_tbl;
72 struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp;
75 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
76 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
81 * struct rhashtable_params - Hash table construction parameters
82 * @nelem_hint: Hint on number of elements, should be 75% of desired size
83 * @key_len: Length of key
84 * @key_offset: Offset of key in struct to be hashed
85 * @head_offset: Offset of rhash_head in struct to be hashed
86 * @max_shift: Maximum number of shifts while expanding
87 * @min_shift: Minimum number of shifts while shrinking
88 * @max_size: Maximum size while expanding
89 * @min_size: Minimum size while shrinking
90 * @nulls_base: Base value to generate nulls marker
91 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
92 * @hashfn: Function to hash key
93 * @obj_hashfn: Function to hash object
95 struct rhashtable_params {
102 unsigned int max_size;
103 unsigned int min_size;
107 rht_obj_hashfn_t obj_hashfn;
111 * struct rhashtable - Hash table handle
113 * @nelems: Number of elements in table
114 * @p: Configuration parameters
115 * @run_work: Deferred worker to expand/shrink asynchronously
116 * @mutex: Mutex to protect current/future table swapping
117 * @being_destroyed: True if table is set up for destruction
120 struct bucket_table __rcu *tbl;
122 bool being_destroyed;
123 struct rhashtable_params p;
124 struct work_struct run_work;
129 * struct rhashtable_walker - Hash table walker
130 * @list: List entry on list of walkers
131 * @tbl: The table that we were walking over
133 struct rhashtable_walker {
134 struct list_head list;
135 struct bucket_table *tbl;
139 * struct rhashtable_iter - Hash table iterator, fits into netlink cb
140 * @ht: Table to iterate through
141 * @p: Current pointer
142 * @walker: Associated rhashtable walker
143 * @slot: Current slot
144 * @skip: Number of entries to skip in slot
146 struct rhashtable_iter {
147 struct rhashtable *ht;
148 struct rhash_head *p;
149 struct rhashtable_walker *walker;
154 static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
156 return NULLS_MARKER(ht->p.nulls_base + hash);
159 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
160 ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
162 static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
164 return ((unsigned long) ptr & 1);
167 static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
169 return ((unsigned long) ptr) >> 1;
172 #ifdef CONFIG_PROVE_LOCKING
173 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
174 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
176 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
181 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
186 #endif /* CONFIG_PROVE_LOCKING */
188 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
190 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
191 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
193 int rhashtable_expand(struct rhashtable *ht);
194 int rhashtable_shrink(struct rhashtable *ht);
196 void *rhashtable_lookup(struct rhashtable *ht, const void *key);
197 void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
198 bool (*compare)(void *, void *), void *arg);
200 bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
201 bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
202 struct rhash_head *obj,
203 bool (*compare)(void *, void *),
206 int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
207 void rhashtable_walk_exit(struct rhashtable_iter *iter);
208 int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
209 void *rhashtable_walk_next(struct rhashtable_iter *iter);
210 void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
212 void rhashtable_destroy(struct rhashtable *ht);
214 #define rht_dereference(p, ht) \
215 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
217 #define rht_dereference_rcu(p, ht) \
218 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
220 #define rht_dereference_bucket(p, tbl, hash) \
221 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
223 #define rht_dereference_bucket_rcu(p, tbl, hash) \
224 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
226 #define rht_entry(tpos, pos, member) \
227 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
230 * rht_for_each_continue - continue iterating over hash chain
231 * @pos: the &struct rhash_head to use as a loop cursor.
232 * @head: the previous &struct rhash_head to continue from
233 * @tbl: the &struct bucket_table
234 * @hash: the hash value / bucket index
236 #define rht_for_each_continue(pos, head, tbl, hash) \
237 for (pos = rht_dereference_bucket(head, tbl, hash); \
238 !rht_is_a_nulls(pos); \
239 pos = rht_dereference_bucket((pos)->next, tbl, hash))
242 * rht_for_each - iterate over hash chain
243 * @pos: the &struct rhash_head to use as a loop cursor.
244 * @tbl: the &struct bucket_table
245 * @hash: the hash value / bucket index
247 #define rht_for_each(pos, tbl, hash) \
248 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
251 * rht_for_each_entry_continue - continue iterating over hash chain
252 * @tpos: the type * to use as a loop cursor.
253 * @pos: the &struct rhash_head to use as a loop cursor.
254 * @head: the previous &struct rhash_head to continue from
255 * @tbl: the &struct bucket_table
256 * @hash: the hash value / bucket index
257 * @member: name of the &struct rhash_head within the hashable struct.
259 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
260 for (pos = rht_dereference_bucket(head, tbl, hash); \
261 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
262 pos = rht_dereference_bucket((pos)->next, tbl, hash))
265 * rht_for_each_entry - iterate over hash chain of given type
266 * @tpos: the type * to use as a loop cursor.
267 * @pos: the &struct rhash_head to use as a loop cursor.
268 * @tbl: the &struct bucket_table
269 * @hash: the hash value / bucket index
270 * @member: name of the &struct rhash_head within the hashable struct.
272 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \
273 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
277 * rht_for_each_entry_safe - safely iterate over hash chain of given type
278 * @tpos: the type * to use as a loop cursor.
279 * @pos: the &struct rhash_head to use as a loop cursor.
280 * @next: the &struct rhash_head to use as next in loop cursor.
281 * @tbl: the &struct bucket_table
282 * @hash: the hash value / bucket index
283 * @member: name of the &struct rhash_head within the hashable struct.
285 * This hash chain list-traversal primitive allows for the looped code to
286 * remove the loop cursor from the list.
288 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
289 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
290 next = !rht_is_a_nulls(pos) ? \
291 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
292 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
294 next = !rht_is_a_nulls(pos) ? \
295 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
298 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
299 * @pos: the &struct rhash_head to use as a loop cursor.
300 * @head: the previous &struct rhash_head to continue from
301 * @tbl: the &struct bucket_table
302 * @hash: the hash value / bucket index
304 * This hash chain list-traversal primitive may safely run concurrently with
305 * the _rcu mutation primitives such as rhashtable_insert() as long as the
306 * traversal is guarded by rcu_read_lock().
308 #define rht_for_each_rcu_continue(pos, head, tbl, hash) \
309 for (({barrier(); }), \
310 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
311 !rht_is_a_nulls(pos); \
312 pos = rcu_dereference_raw(pos->next))
315 * rht_for_each_rcu - iterate over rcu hash chain
316 * @pos: the &struct rhash_head to use as a loop cursor.
317 * @tbl: the &struct bucket_table
318 * @hash: the hash value / bucket index
320 * This hash chain list-traversal primitive may safely run concurrently with
321 * the _rcu mutation primitives such as rhashtable_insert() as long as the
322 * traversal is guarded by rcu_read_lock().
324 #define rht_for_each_rcu(pos, tbl, hash) \
325 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
328 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
329 * @tpos: the type * to use as a loop cursor.
330 * @pos: the &struct rhash_head to use as a loop cursor.
331 * @head: the previous &struct rhash_head to continue from
332 * @tbl: the &struct bucket_table
333 * @hash: the hash value / bucket index
334 * @member: name of the &struct rhash_head within the hashable struct.
336 * This hash chain list-traversal primitive may safely run concurrently with
337 * the _rcu mutation primitives such as rhashtable_insert() as long as the
338 * traversal is guarded by rcu_read_lock().
340 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
341 for (({barrier(); }), \
342 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
343 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
344 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
347 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
348 * @tpos: the type * to use as a loop cursor.
349 * @pos: the &struct rhash_head to use as a loop cursor.
350 * @tbl: the &struct bucket_table
351 * @hash: the hash value / bucket index
352 * @member: name of the &struct rhash_head within the hashable struct.
354 * This hash chain list-traversal primitive may safely run concurrently with
355 * the _rcu mutation primitives such as rhashtable_insert() as long as the
356 * traversal is guarded by rcu_read_lock().
358 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
359 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
362 #endif /* _LINUX_RHASHTABLE_H */