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 * @locks_mask: Mask to apply before accessing locks[]
53 * @locks: Array of spinlocks protecting individual buckets
54 * @buckets: size * hash buckets
58 unsigned int locks_mask;
60 struct rhash_head __rcu *buckets[];
63 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
64 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
69 * struct rhashtable_params - Hash table construction parameters
70 * @nelem_hint: Hint on number of elements, should be 75% of desired size
71 * @key_len: Length of key
72 * @key_offset: Offset of key in struct to be hashed
73 * @head_offset: Offset of rhash_head in struct to be hashed
74 * @hash_rnd: Seed to use while hashing
75 * @max_shift: Maximum number of shifts while expanding
76 * @min_shift: Minimum number of shifts while shrinking
77 * @nulls_base: Base value to generate nulls marker
78 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
79 * @hashfn: Function to hash key
80 * @obj_hashfn: Function to hash object
81 * @grow_decision: If defined, may return true if table should expand
82 * @shrink_decision: If defined, may return true if table should shrink
84 * Note: when implementing the grow and shrink decision function, min/max
85 * shift must be enforced, otherwise, resizing watermarks they set may be
88 struct rhashtable_params {
99 rht_obj_hashfn_t obj_hashfn;
100 bool (*grow_decision)(const struct rhashtable *ht,
102 bool (*shrink_decision)(const struct rhashtable *ht,
107 * struct rhashtable - Hash table handle
109 * @future_tbl: Table under construction during expansion/shrinking
110 * @nelems: Number of elements in table
111 * @shift: Current size (1 << shift)
112 * @p: Configuration parameters
113 * @run_work: Deferred worker to expand/shrink asynchronously
114 * @mutex: Mutex to protect current/future table swapping
115 * @walkers: List of active walkers
116 * @being_destroyed: True if table is set up for destruction
119 struct bucket_table __rcu *tbl;
120 struct bucket_table __rcu *future_tbl;
123 struct rhashtable_params p;
124 struct work_struct run_work;
126 struct list_head walkers;
127 bool being_destroyed;
131 * struct rhashtable_walker - Hash table walker
132 * @list: List entry on list of walkers
133 * @resize: Resize event occured
135 struct rhashtable_walker {
136 struct list_head list;
141 * struct rhashtable_iter - Hash table iterator, fits into netlink cb
142 * @ht: Table to iterate through
143 * @p: Current pointer
144 * @walker: Associated rhashtable walker
145 * @slot: Current slot
146 * @skip: Number of entries to skip in slot
148 struct rhashtable_iter {
149 struct rhashtable *ht;
150 struct rhash_head *p;
151 struct rhashtable_walker *walker;
156 static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
158 return NULLS_MARKER(ht->p.nulls_base + hash);
161 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
162 ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
164 static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
166 return ((unsigned long) ptr & 1);
169 static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
171 return ((unsigned long) ptr) >> 1;
174 #ifdef CONFIG_PROVE_LOCKING
175 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
176 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
178 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
183 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
188 #endif /* CONFIG_PROVE_LOCKING */
190 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
192 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
193 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
195 bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size);
196 bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size);
198 int rhashtable_expand(struct rhashtable *ht);
199 int rhashtable_shrink(struct rhashtable *ht);
201 void *rhashtable_lookup(struct rhashtable *ht, const void *key);
202 void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
203 bool (*compare)(void *, void *), void *arg);
205 bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
206 bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
207 struct rhash_head *obj,
208 bool (*compare)(void *, void *),
211 int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
212 void rhashtable_walk_exit(struct rhashtable_iter *iter);
213 int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
214 void *rhashtable_walk_next(struct rhashtable_iter *iter);
215 void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
217 void rhashtable_destroy(struct rhashtable *ht);
219 #define rht_dereference(p, ht) \
220 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
222 #define rht_dereference_rcu(p, ht) \
223 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
225 #define rht_dereference_bucket(p, tbl, hash) \
226 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
228 #define rht_dereference_bucket_rcu(p, tbl, hash) \
229 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
231 #define rht_entry(tpos, pos, member) \
232 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
235 * rht_for_each_continue - continue iterating over hash chain
236 * @pos: the &struct rhash_head to use as a loop cursor.
237 * @head: the previous &struct rhash_head to continue from
238 * @tbl: the &struct bucket_table
239 * @hash: the hash value / bucket index
241 #define rht_for_each_continue(pos, head, tbl, hash) \
242 for (pos = rht_dereference_bucket(head, tbl, hash); \
243 !rht_is_a_nulls(pos); \
244 pos = rht_dereference_bucket((pos)->next, tbl, hash))
247 * rht_for_each - iterate over hash chain
248 * @pos: the &struct rhash_head to use as a loop cursor.
249 * @tbl: the &struct bucket_table
250 * @hash: the hash value / bucket index
252 #define rht_for_each(pos, tbl, hash) \
253 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
256 * rht_for_each_entry_continue - continue iterating over hash chain
257 * @tpos: the type * to use as a loop cursor.
258 * @pos: the &struct rhash_head to use as a loop cursor.
259 * @head: the previous &struct rhash_head to continue from
260 * @tbl: the &struct bucket_table
261 * @hash: the hash value / bucket index
262 * @member: name of the &struct rhash_head within the hashable struct.
264 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
265 for (pos = rht_dereference_bucket(head, tbl, hash); \
266 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
267 pos = rht_dereference_bucket((pos)->next, tbl, hash))
270 * rht_for_each_entry - iterate over hash chain of given type
271 * @tpos: the type * to use as a loop cursor.
272 * @pos: the &struct rhash_head to use as a loop cursor.
273 * @tbl: the &struct bucket_table
274 * @hash: the hash value / bucket index
275 * @member: name of the &struct rhash_head within the hashable struct.
277 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \
278 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
282 * rht_for_each_entry_safe - safely iterate over hash chain of given type
283 * @tpos: the type * to use as a loop cursor.
284 * @pos: the &struct rhash_head to use as a loop cursor.
285 * @next: the &struct rhash_head to use as next in loop cursor.
286 * @tbl: the &struct bucket_table
287 * @hash: the hash value / bucket index
288 * @member: name of the &struct rhash_head within the hashable struct.
290 * This hash chain list-traversal primitive allows for the looped code to
291 * remove the loop cursor from the list.
293 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
294 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
295 next = !rht_is_a_nulls(pos) ? \
296 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
297 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
299 next = !rht_is_a_nulls(pos) ? \
300 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
303 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
304 * @pos: the &struct rhash_head to use as a loop cursor.
305 * @head: the previous &struct rhash_head to continue from
306 * @tbl: the &struct bucket_table
307 * @hash: the hash value / bucket index
309 * This hash chain list-traversal primitive may safely run concurrently with
310 * the _rcu mutation primitives such as rhashtable_insert() as long as the
311 * traversal is guarded by rcu_read_lock().
313 #define rht_for_each_rcu_continue(pos, head, tbl, hash) \
314 for (({barrier(); }), \
315 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
316 !rht_is_a_nulls(pos); \
317 pos = rcu_dereference_raw(pos->next))
320 * rht_for_each_rcu - iterate over rcu hash chain
321 * @pos: the &struct rhash_head to use as a loop cursor.
322 * @tbl: the &struct bucket_table
323 * @hash: the hash value / bucket index
325 * This hash chain list-traversal primitive may safely run concurrently with
326 * the _rcu mutation primitives such as rhashtable_insert() as long as the
327 * traversal is guarded by rcu_read_lock().
329 #define rht_for_each_rcu(pos, tbl, hash) \
330 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
333 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
334 * @tpos: the type * to use as a loop cursor.
335 * @pos: the &struct rhash_head to use as a loop cursor.
336 * @head: the previous &struct rhash_head to continue from
337 * @tbl: the &struct bucket_table
338 * @hash: the hash value / bucket index
339 * @member: name of the &struct rhash_head within the hashable struct.
341 * This hash chain list-traversal primitive may safely run concurrently with
342 * the _rcu mutation primitives such as rhashtable_insert() as long as the
343 * traversal is guarded by rcu_read_lock().
345 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
346 for (({barrier(); }), \
347 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
348 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
349 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
352 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
353 * @tpos: the type * to use as a loop cursor.
354 * @pos: the &struct rhash_head to use as a loop cursor.
355 * @tbl: the &struct bucket_table
356 * @hash: the hash value / bucket index
357 * @member: name of the &struct rhash_head within the hashable struct.
359 * This hash chain list-traversal primitive may safely run concurrently with
360 * the _rcu mutation primitives such as rhashtable_insert() as long as the
361 * traversal is guarded by rcu_read_lock().
363 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
364 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
367 #endif /* _LINUX_RHASHTABLE_H */