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 * @future_tbl: Table under construction during rehashing
60 * @buckets: size * hash buckets
67 unsigned int locks_mask;
69 struct list_head walkers;
72 struct bucket_table __rcu *future_tbl;
74 struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp;
77 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
78 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
83 * struct rhashtable_params - Hash table construction parameters
84 * @nelem_hint: Hint on number of elements, should be 75% of desired size
85 * @key_len: Length of key
86 * @key_offset: Offset of key in struct to be hashed
87 * @head_offset: Offset of rhash_head in struct to be hashed
88 * @max_shift: Maximum number of shifts while expanding
89 * @min_shift: Minimum number of shifts 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 {
105 rht_obj_hashfn_t obj_hashfn;
109 * struct rhashtable - Hash table handle
111 * @nelems: Number of elements in table
112 * @p: Configuration parameters
113 * @run_work: Deferred worker to expand/shrink asynchronously
114 * @mutex: Mutex to protect current/future table swapping
115 * @being_destroyed: True if table is set up for destruction
118 struct bucket_table __rcu *tbl;
120 bool being_destroyed;
121 struct rhashtable_params p;
122 struct work_struct run_work;
127 * struct rhashtable_walker - Hash table walker
128 * @list: List entry on list of walkers
129 * @tbl: The table that we were walking over
131 struct rhashtable_walker {
132 struct list_head list;
133 struct bucket_table *tbl;
137 * struct rhashtable_iter - Hash table iterator, fits into netlink cb
138 * @ht: Table to iterate through
139 * @p: Current pointer
140 * @walker: Associated rhashtable walker
141 * @slot: Current slot
142 * @skip: Number of entries to skip in slot
144 struct rhashtable_iter {
145 struct rhashtable *ht;
146 struct rhash_head *p;
147 struct rhashtable_walker *walker;
152 static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
154 return NULLS_MARKER(ht->p.nulls_base + hash);
157 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
158 ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
160 static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
162 return ((unsigned long) ptr & 1);
165 static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
167 return ((unsigned long) ptr) >> 1;
170 #ifdef CONFIG_PROVE_LOCKING
171 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
172 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
174 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
179 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
184 #endif /* CONFIG_PROVE_LOCKING */
186 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
188 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
189 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
191 int rhashtable_expand(struct rhashtable *ht);
192 int rhashtable_shrink(struct rhashtable *ht);
194 void *rhashtable_lookup(struct rhashtable *ht, const void *key);
195 void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
196 bool (*compare)(void *, void *), void *arg);
198 bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
199 bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
200 struct rhash_head *obj,
201 bool (*compare)(void *, void *),
204 int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
205 void rhashtable_walk_exit(struct rhashtable_iter *iter);
206 int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
207 void *rhashtable_walk_next(struct rhashtable_iter *iter);
208 void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
210 void rhashtable_destroy(struct rhashtable *ht);
212 #define rht_dereference(p, ht) \
213 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
215 #define rht_dereference_rcu(p, ht) \
216 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
218 #define rht_dereference_bucket(p, tbl, hash) \
219 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
221 #define rht_dereference_bucket_rcu(p, tbl, hash) \
222 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
224 #define rht_entry(tpos, pos, member) \
225 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
228 * rht_for_each_continue - continue iterating over hash chain
229 * @pos: the &struct rhash_head to use as a loop cursor.
230 * @head: the previous &struct rhash_head to continue from
231 * @tbl: the &struct bucket_table
232 * @hash: the hash value / bucket index
234 #define rht_for_each_continue(pos, head, tbl, hash) \
235 for (pos = rht_dereference_bucket(head, tbl, hash); \
236 !rht_is_a_nulls(pos); \
237 pos = rht_dereference_bucket((pos)->next, tbl, hash))
240 * rht_for_each - iterate over hash chain
241 * @pos: the &struct rhash_head to use as a loop cursor.
242 * @tbl: the &struct bucket_table
243 * @hash: the hash value / bucket index
245 #define rht_for_each(pos, tbl, hash) \
246 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
249 * rht_for_each_entry_continue - continue iterating over hash chain
250 * @tpos: the type * to use as a loop cursor.
251 * @pos: the &struct rhash_head to use as a loop cursor.
252 * @head: the previous &struct rhash_head to continue from
253 * @tbl: the &struct bucket_table
254 * @hash: the hash value / bucket index
255 * @member: name of the &struct rhash_head within the hashable struct.
257 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
258 for (pos = rht_dereference_bucket(head, tbl, hash); \
259 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
260 pos = rht_dereference_bucket((pos)->next, tbl, hash))
263 * rht_for_each_entry - iterate over hash chain of given type
264 * @tpos: the type * to use as a loop cursor.
265 * @pos: the &struct rhash_head to use as a loop cursor.
266 * @tbl: the &struct bucket_table
267 * @hash: the hash value / bucket index
268 * @member: name of the &struct rhash_head within the hashable struct.
270 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \
271 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
275 * rht_for_each_entry_safe - safely iterate over hash chain of given type
276 * @tpos: the type * to use as a loop cursor.
277 * @pos: the &struct rhash_head to use as a loop cursor.
278 * @next: the &struct rhash_head to use as next in loop cursor.
279 * @tbl: the &struct bucket_table
280 * @hash: the hash value / bucket index
281 * @member: name of the &struct rhash_head within the hashable struct.
283 * This hash chain list-traversal primitive allows for the looped code to
284 * remove the loop cursor from the list.
286 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
287 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
288 next = !rht_is_a_nulls(pos) ? \
289 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
290 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
292 next = !rht_is_a_nulls(pos) ? \
293 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
296 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
297 * @pos: the &struct rhash_head to use as a loop cursor.
298 * @head: the previous &struct rhash_head to continue from
299 * @tbl: the &struct bucket_table
300 * @hash: the hash value / bucket index
302 * This hash chain list-traversal primitive may safely run concurrently with
303 * the _rcu mutation primitives such as rhashtable_insert() as long as the
304 * traversal is guarded by rcu_read_lock().
306 #define rht_for_each_rcu_continue(pos, head, tbl, hash) \
307 for (({barrier(); }), \
308 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
309 !rht_is_a_nulls(pos); \
310 pos = rcu_dereference_raw(pos->next))
313 * rht_for_each_rcu - iterate over rcu hash chain
314 * @pos: the &struct rhash_head to use as a loop cursor.
315 * @tbl: the &struct bucket_table
316 * @hash: the hash value / bucket index
318 * This hash chain list-traversal primitive may safely run concurrently with
319 * the _rcu mutation primitives such as rhashtable_insert() as long as the
320 * traversal is guarded by rcu_read_lock().
322 #define rht_for_each_rcu(pos, tbl, hash) \
323 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
326 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
327 * @tpos: the type * to use as a loop cursor.
328 * @pos: the &struct rhash_head to use as a loop cursor.
329 * @head: the previous &struct rhash_head to continue from
330 * @tbl: the &struct bucket_table
331 * @hash: the hash value / bucket index
332 * @member: name of the &struct rhash_head within the hashable struct.
334 * This hash chain list-traversal primitive may safely run concurrently with
335 * the _rcu mutation primitives such as rhashtable_insert() as long as the
336 * traversal is guarded by rcu_read_lock().
338 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
339 for (({barrier(); }), \
340 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
341 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
342 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
345 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
346 * @tpos: the type * to use as a loop cursor.
347 * @pos: the &struct rhash_head to use as a loop cursor.
348 * @tbl: the &struct bucket_table
349 * @hash: the hash value / bucket index
350 * @member: name of the &struct rhash_head within the hashable struct.
352 * This hash chain list-traversal primitive may safely run concurrently with
353 * the _rcu mutation primitives such as rhashtable_insert() as long as the
354 * traversal is guarded by rcu_read_lock().
356 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
357 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
360 #endif /* _LINUX_RHASHTABLE_H */