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 * @shift: Current size (1 << shift)
55 * @locks_mask: Mask to apply before accessing locks[]
56 * @locks: Array of spinlocks protecting individual buckets
57 * @walkers: List of active walkers
58 * @rcu: RCU structure for freeing the table
59 * @buckets: size * hash buckets
66 unsigned int locks_mask;
68 struct list_head walkers;
71 struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp;
74 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
75 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
80 * struct rhashtable_params - Hash table construction parameters
81 * @nelem_hint: Hint on number of elements, should be 75% of desired size
82 * @key_len: Length of key
83 * @key_offset: Offset of key in struct to be hashed
84 * @head_offset: Offset of rhash_head in struct to be hashed
85 * @max_shift: Maximum number of shifts while expanding
86 * @min_shift: Minimum number of shifts while shrinking
87 * @nulls_base: Base value to generate nulls marker
88 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
89 * @hashfn: Function to hash key
90 * @obj_hashfn: Function to hash object
92 struct rhashtable_params {
102 rht_obj_hashfn_t obj_hashfn;
106 * struct rhashtable - Hash table handle
108 * @future_tbl: Table under construction during expansion/shrinking
109 * @nelems: Number of elements in table
110 * @p: Configuration parameters
111 * @run_work: Deferred worker to expand/shrink asynchronously
112 * @mutex: Mutex to protect current/future table swapping
113 * @being_destroyed: True if table is set up for destruction
116 struct bucket_table __rcu *tbl;
117 struct bucket_table __rcu *future_tbl;
119 bool being_destroyed;
120 struct rhashtable_params p;
121 struct work_struct run_work;
126 * struct rhashtable_walker - Hash table walker
127 * @list: List entry on list of walkers
128 * @tbl: The table that we were walking over
130 struct rhashtable_walker {
131 struct list_head list;
132 struct bucket_table *tbl;
136 * struct rhashtable_iter - Hash table iterator, fits into netlink cb
137 * @ht: Table to iterate through
138 * @p: Current pointer
139 * @walker: Associated rhashtable walker
140 * @slot: Current slot
141 * @skip: Number of entries to skip in slot
143 struct rhashtable_iter {
144 struct rhashtable *ht;
145 struct rhash_head *p;
146 struct rhashtable_walker *walker;
151 static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
153 return NULLS_MARKER(ht->p.nulls_base + hash);
156 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
157 ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
159 static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
161 return ((unsigned long) ptr & 1);
164 static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
166 return ((unsigned long) ptr) >> 1;
169 #ifdef CONFIG_PROVE_LOCKING
170 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
171 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
173 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
178 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
183 #endif /* CONFIG_PROVE_LOCKING */
185 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
187 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
188 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
190 int rhashtable_expand(struct rhashtable *ht);
191 int rhashtable_shrink(struct rhashtable *ht);
193 void *rhashtable_lookup(struct rhashtable *ht, const void *key);
194 void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
195 bool (*compare)(void *, void *), void *arg);
197 bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
198 bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
199 struct rhash_head *obj,
200 bool (*compare)(void *, void *),
203 int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
204 void rhashtable_walk_exit(struct rhashtable_iter *iter);
205 int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
206 void *rhashtable_walk_next(struct rhashtable_iter *iter);
207 void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
209 void rhashtable_destroy(struct rhashtable *ht);
211 #define rht_dereference(p, ht) \
212 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
214 #define rht_dereference_rcu(p, ht) \
215 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
217 #define rht_dereference_bucket(p, tbl, hash) \
218 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
220 #define rht_dereference_bucket_rcu(p, tbl, hash) \
221 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
223 #define rht_entry(tpos, pos, member) \
224 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
227 * rht_for_each_continue - continue iterating over hash chain
228 * @pos: the &struct rhash_head to use as a loop cursor.
229 * @head: the previous &struct rhash_head to continue from
230 * @tbl: the &struct bucket_table
231 * @hash: the hash value / bucket index
233 #define rht_for_each_continue(pos, head, tbl, hash) \
234 for (pos = rht_dereference_bucket(head, tbl, hash); \
235 !rht_is_a_nulls(pos); \
236 pos = rht_dereference_bucket((pos)->next, tbl, hash))
239 * rht_for_each - iterate over hash chain
240 * @pos: the &struct rhash_head to use as a loop cursor.
241 * @tbl: the &struct bucket_table
242 * @hash: the hash value / bucket index
244 #define rht_for_each(pos, tbl, hash) \
245 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
248 * rht_for_each_entry_continue - continue iterating over hash chain
249 * @tpos: the type * to use as a loop cursor.
250 * @pos: the &struct rhash_head to use as a loop cursor.
251 * @head: the previous &struct rhash_head to continue from
252 * @tbl: the &struct bucket_table
253 * @hash: the hash value / bucket index
254 * @member: name of the &struct rhash_head within the hashable struct.
256 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
257 for (pos = rht_dereference_bucket(head, tbl, hash); \
258 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
259 pos = rht_dereference_bucket((pos)->next, tbl, hash))
262 * rht_for_each_entry - iterate over hash chain of given type
263 * @tpos: the type * to use as a loop cursor.
264 * @pos: the &struct rhash_head to use as a loop cursor.
265 * @tbl: the &struct bucket_table
266 * @hash: the hash value / bucket index
267 * @member: name of the &struct rhash_head within the hashable struct.
269 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \
270 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
274 * rht_for_each_entry_safe - safely iterate over hash chain of given type
275 * @tpos: the type * to use as a loop cursor.
276 * @pos: the &struct rhash_head to use as a loop cursor.
277 * @next: the &struct rhash_head to use as next in loop cursor.
278 * @tbl: the &struct bucket_table
279 * @hash: the hash value / bucket index
280 * @member: name of the &struct rhash_head within the hashable struct.
282 * This hash chain list-traversal primitive allows for the looped code to
283 * remove the loop cursor from the list.
285 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
286 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
287 next = !rht_is_a_nulls(pos) ? \
288 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
289 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
291 next = !rht_is_a_nulls(pos) ? \
292 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
295 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
296 * @pos: the &struct rhash_head to use as a loop cursor.
297 * @head: the previous &struct rhash_head to continue from
298 * @tbl: the &struct bucket_table
299 * @hash: the hash value / bucket index
301 * This hash chain list-traversal primitive may safely run concurrently with
302 * the _rcu mutation primitives such as rhashtable_insert() as long as the
303 * traversal is guarded by rcu_read_lock().
305 #define rht_for_each_rcu_continue(pos, head, tbl, hash) \
306 for (({barrier(); }), \
307 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
308 !rht_is_a_nulls(pos); \
309 pos = rcu_dereference_raw(pos->next))
312 * rht_for_each_rcu - iterate over rcu hash chain
313 * @pos: the &struct rhash_head to use as a loop cursor.
314 * @tbl: the &struct bucket_table
315 * @hash: the hash value / bucket index
317 * This hash chain list-traversal primitive may safely run concurrently with
318 * the _rcu mutation primitives such as rhashtable_insert() as long as the
319 * traversal is guarded by rcu_read_lock().
321 #define rht_for_each_rcu(pos, tbl, hash) \
322 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
325 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
326 * @tpos: the type * to use as a loop cursor.
327 * @pos: the &struct rhash_head to use as a loop cursor.
328 * @head: the previous &struct rhash_head to continue from
329 * @tbl: the &struct bucket_table
330 * @hash: the hash value / bucket index
331 * @member: name of the &struct rhash_head within the hashable struct.
333 * This hash chain list-traversal primitive may safely run concurrently with
334 * the _rcu mutation primitives such as rhashtable_insert() as long as the
335 * traversal is guarded by rcu_read_lock().
337 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
338 for (({barrier(); }), \
339 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
340 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
341 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
344 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
345 * @tpos: the type * to use as a loop cursor.
346 * @pos: the &struct rhash_head to use as a loop cursor.
347 * @tbl: the &struct bucket_table
348 * @hash: the hash value / bucket index
349 * @member: name of the &struct rhash_head within the hashable struct.
351 * This hash chain list-traversal primitive may safely run concurrently with
352 * the _rcu mutation primitives such as rhashtable_insert() as long as the
353 * traversal is guarded by rcu_read_lock().
355 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
356 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
359 #endif /* _LINUX_RHASHTABLE_H */