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1 | /* | |
2 | * Resizable, Scalable, Concurrent Hash Table | |
3 | * | |
4 | * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch> | |
5 | * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net> | |
6 | * | |
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 | |
10 | * | |
11 | * Code partially derived from nft_hash | |
12 | * | |
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. | |
16 | */ | |
17 | ||
18 | #ifndef _LINUX_RHASHTABLE_H | |
19 | #define _LINUX_RHASHTABLE_H | |
20 | ||
21 | #include <linux/compiler.h> | |
22 | #include <linux/list_nulls.h> | |
23 | #include <linux/workqueue.h> | |
24 | #include <linux/mutex.h> | |
25 | ||
26 | /* | |
27 | * The end of the chain is marked with a special nulls marks which has | |
28 | * the following format: | |
29 | * | |
30 | * +-------+-----------------------------------------------------+-+ | |
31 | * | Base | Hash |1| | |
32 | * +-------+-----------------------------------------------------+-+ | |
33 | * | |
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) | |
38 | * | |
39 | * The remaining bits of the next pointer remain unused for now. | |
40 | */ | |
41 | #define RHT_BASE_BITS 4 | |
42 | #define RHT_HASH_BITS 27 | |
43 | #define RHT_BASE_SHIFT RHT_HASH_BITS | |
44 | ||
45 | struct rhash_head { | |
46 | struct rhash_head __rcu *next; | |
47 | }; | |
48 | ||
49 | /** | |
50 | * struct bucket_table - Table of hash buckets | |
51 | * @size: Number of hash buckets | |
52 | * @hash_rnd: Random seed to fold into hash | |
53 | * @shift: Current size (1 << shift) | |
54 | * @locks_mask: Mask to apply before accessing locks[] | |
55 | * @locks: Array of spinlocks protecting individual buckets | |
56 | * @buckets: size * hash buckets | |
57 | */ | |
58 | struct bucket_table { | |
59 | size_t size; | |
60 | u32 hash_rnd; | |
61 | u32 shift; | |
62 | unsigned int locks_mask; | |
63 | spinlock_t *locks; | |
64 | ||
65 | struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp; | |
66 | }; | |
67 | ||
68 | typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed); | |
69 | typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed); | |
70 | ||
71 | struct rhashtable; | |
72 | ||
73 | /** | |
74 | * struct rhashtable_params - Hash table construction parameters | |
75 | * @nelem_hint: Hint on number of elements, should be 75% of desired size | |
76 | * @key_len: Length of key | |
77 | * @key_offset: Offset of key in struct to be hashed | |
78 | * @head_offset: Offset of rhash_head in struct to be hashed | |
79 | * @max_shift: Maximum number of shifts while expanding | |
80 | * @min_shift: Minimum number of shifts while shrinking | |
81 | * @nulls_base: Base value to generate nulls marker | |
82 | * @locks_mul: Number of bucket locks to allocate per cpu (default: 128) | |
83 | * @hashfn: Function to hash key | |
84 | * @obj_hashfn: Function to hash object | |
85 | */ | |
86 | struct rhashtable_params { | |
87 | size_t nelem_hint; | |
88 | size_t key_len; | |
89 | size_t key_offset; | |
90 | size_t head_offset; | |
91 | size_t max_shift; | |
92 | size_t min_shift; | |
93 | u32 nulls_base; | |
94 | size_t locks_mul; | |
95 | rht_hashfn_t hashfn; | |
96 | rht_obj_hashfn_t obj_hashfn; | |
97 | }; | |
98 | ||
99 | /** | |
100 | * struct rhashtable - Hash table handle | |
101 | * @tbl: Bucket table | |
102 | * @future_tbl: Table under construction during expansion/shrinking | |
103 | * @nelems: Number of elements in table | |
104 | * @p: Configuration parameters | |
105 | * @run_work: Deferred worker to expand/shrink asynchronously | |
106 | * @mutex: Mutex to protect current/future table swapping | |
107 | * @walkers: List of active walkers | |
108 | * @being_destroyed: True if table is set up for destruction | |
109 | */ | |
110 | struct rhashtable { | |
111 | struct bucket_table __rcu *tbl; | |
112 | struct bucket_table __rcu *future_tbl; | |
113 | atomic_t nelems; | |
114 | bool being_destroyed; | |
115 | struct rhashtable_params p; | |
116 | struct work_struct run_work; | |
117 | struct mutex mutex; | |
118 | struct list_head walkers; | |
119 | }; | |
120 | ||
121 | /** | |
122 | * struct rhashtable_walker - Hash table walker | |
123 | * @list: List entry on list of walkers | |
124 | * @resize: Resize event occured | |
125 | */ | |
126 | struct rhashtable_walker { | |
127 | struct list_head list; | |
128 | bool resize; | |
129 | }; | |
130 | ||
131 | /** | |
132 | * struct rhashtable_iter - Hash table iterator, fits into netlink cb | |
133 | * @ht: Table to iterate through | |
134 | * @p: Current pointer | |
135 | * @walker: Associated rhashtable walker | |
136 | * @slot: Current slot | |
137 | * @skip: Number of entries to skip in slot | |
138 | */ | |
139 | struct rhashtable_iter { | |
140 | struct rhashtable *ht; | |
141 | struct rhash_head *p; | |
142 | struct rhashtable_walker *walker; | |
143 | unsigned int slot; | |
144 | unsigned int skip; | |
145 | }; | |
146 | ||
147 | static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash) | |
148 | { | |
149 | return NULLS_MARKER(ht->p.nulls_base + hash); | |
150 | } | |
151 | ||
152 | #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \ | |
153 | ((ptr) = (typeof(ptr)) rht_marker(ht, hash)) | |
154 | ||
155 | static inline bool rht_is_a_nulls(const struct rhash_head *ptr) | |
156 | { | |
157 | return ((unsigned long) ptr & 1); | |
158 | } | |
159 | ||
160 | static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr) | |
161 | { | |
162 | return ((unsigned long) ptr) >> 1; | |
163 | } | |
164 | ||
165 | #ifdef CONFIG_PROVE_LOCKING | |
166 | int lockdep_rht_mutex_is_held(struct rhashtable *ht); | |
167 | int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash); | |
168 | #else | |
169 | static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht) | |
170 | { | |
171 | return 1; | |
172 | } | |
173 | ||
174 | static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, | |
175 | u32 hash) | |
176 | { | |
177 | return 1; | |
178 | } | |
179 | #endif /* CONFIG_PROVE_LOCKING */ | |
180 | ||
181 | int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params); | |
182 | ||
183 | void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node); | |
184 | bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node); | |
185 | ||
186 | int rhashtable_expand(struct rhashtable *ht); | |
187 | int rhashtable_shrink(struct rhashtable *ht); | |
188 | ||
189 | void *rhashtable_lookup(struct rhashtable *ht, const void *key); | |
190 | void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key, | |
191 | bool (*compare)(void *, void *), void *arg); | |
192 | ||
193 | bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj); | |
194 | bool rhashtable_lookup_compare_insert(struct rhashtable *ht, | |
195 | struct rhash_head *obj, | |
196 | bool (*compare)(void *, void *), | |
197 | void *arg); | |
198 | ||
199 | int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter); | |
200 | void rhashtable_walk_exit(struct rhashtable_iter *iter); | |
201 | int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU); | |
202 | void *rhashtable_walk_next(struct rhashtable_iter *iter); | |
203 | void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU); | |
204 | ||
205 | void rhashtable_destroy(struct rhashtable *ht); | |
206 | ||
207 | #define rht_dereference(p, ht) \ | |
208 | rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht)) | |
209 | ||
210 | #define rht_dereference_rcu(p, ht) \ | |
211 | rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht)) | |
212 | ||
213 | #define rht_dereference_bucket(p, tbl, hash) \ | |
214 | rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash)) | |
215 | ||
216 | #define rht_dereference_bucket_rcu(p, tbl, hash) \ | |
217 | rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash)) | |
218 | ||
219 | #define rht_entry(tpos, pos, member) \ | |
220 | ({ tpos = container_of(pos, typeof(*tpos), member); 1; }) | |
221 | ||
222 | /** | |
223 | * rht_for_each_continue - continue iterating over hash chain | |
224 | * @pos: the &struct rhash_head to use as a loop cursor. | |
225 | * @head: the previous &struct rhash_head to continue from | |
226 | * @tbl: the &struct bucket_table | |
227 | * @hash: the hash value / bucket index | |
228 | */ | |
229 | #define rht_for_each_continue(pos, head, tbl, hash) \ | |
230 | for (pos = rht_dereference_bucket(head, tbl, hash); \ | |
231 | !rht_is_a_nulls(pos); \ | |
232 | pos = rht_dereference_bucket((pos)->next, tbl, hash)) | |
233 | ||
234 | /** | |
235 | * rht_for_each - iterate over hash chain | |
236 | * @pos: the &struct rhash_head to use as a loop cursor. | |
237 | * @tbl: the &struct bucket_table | |
238 | * @hash: the hash value / bucket index | |
239 | */ | |
240 | #define rht_for_each(pos, tbl, hash) \ | |
241 | rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash) | |
242 | ||
243 | /** | |
244 | * rht_for_each_entry_continue - continue iterating over hash chain | |
245 | * @tpos: the type * to use as a loop cursor. | |
246 | * @pos: the &struct rhash_head to use as a loop cursor. | |
247 | * @head: the previous &struct rhash_head to continue from | |
248 | * @tbl: the &struct bucket_table | |
249 | * @hash: the hash value / bucket index | |
250 | * @member: name of the &struct rhash_head within the hashable struct. | |
251 | */ | |
252 | #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \ | |
253 | for (pos = rht_dereference_bucket(head, tbl, hash); \ | |
254 | (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ | |
255 | pos = rht_dereference_bucket((pos)->next, tbl, hash)) | |
256 | ||
257 | /** | |
258 | * rht_for_each_entry - iterate over hash chain of given type | |
259 | * @tpos: the type * to use as a loop cursor. | |
260 | * @pos: the &struct rhash_head to use as a loop cursor. | |
261 | * @tbl: the &struct bucket_table | |
262 | * @hash: the hash value / bucket index | |
263 | * @member: name of the &struct rhash_head within the hashable struct. | |
264 | */ | |
265 | #define rht_for_each_entry(tpos, pos, tbl, hash, member) \ | |
266 | rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \ | |
267 | tbl, hash, member) | |
268 | ||
269 | /** | |
270 | * rht_for_each_entry_safe - safely 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 | * @next: the &struct rhash_head to use as next in loop cursor. | |
274 | * @tbl: the &struct bucket_table | |
275 | * @hash: the hash value / bucket index | |
276 | * @member: name of the &struct rhash_head within the hashable struct. | |
277 | * | |
278 | * This hash chain list-traversal primitive allows for the looped code to | |
279 | * remove the loop cursor from the list. | |
280 | */ | |
281 | #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \ | |
282 | for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \ | |
283 | next = !rht_is_a_nulls(pos) ? \ | |
284 | rht_dereference_bucket(pos->next, tbl, hash) : NULL; \ | |
285 | (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ | |
286 | pos = next, \ | |
287 | next = !rht_is_a_nulls(pos) ? \ | |
288 | rht_dereference_bucket(pos->next, tbl, hash) : NULL) | |
289 | ||
290 | /** | |
291 | * rht_for_each_rcu_continue - continue iterating over rcu hash chain | |
292 | * @pos: the &struct rhash_head to use as a loop cursor. | |
293 | * @head: the previous &struct rhash_head to continue from | |
294 | * @tbl: the &struct bucket_table | |
295 | * @hash: the hash value / bucket index | |
296 | * | |
297 | * This hash chain list-traversal primitive may safely run concurrently with | |
298 | * the _rcu mutation primitives such as rhashtable_insert() as long as the | |
299 | * traversal is guarded by rcu_read_lock(). | |
300 | */ | |
301 | #define rht_for_each_rcu_continue(pos, head, tbl, hash) \ | |
302 | for (({barrier(); }), \ | |
303 | pos = rht_dereference_bucket_rcu(head, tbl, hash); \ | |
304 | !rht_is_a_nulls(pos); \ | |
305 | pos = rcu_dereference_raw(pos->next)) | |
306 | ||
307 | /** | |
308 | * rht_for_each_rcu - iterate over rcu hash chain | |
309 | * @pos: the &struct rhash_head to use as a loop cursor. | |
310 | * @tbl: the &struct bucket_table | |
311 | * @hash: the hash value / bucket index | |
312 | * | |
313 | * This hash chain list-traversal primitive may safely run concurrently with | |
314 | * the _rcu mutation primitives such as rhashtable_insert() as long as the | |
315 | * traversal is guarded by rcu_read_lock(). | |
316 | */ | |
317 | #define rht_for_each_rcu(pos, tbl, hash) \ | |
318 | rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash) | |
319 | ||
320 | /** | |
321 | * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain | |
322 | * @tpos: the type * to use as a loop cursor. | |
323 | * @pos: the &struct rhash_head to use as a loop cursor. | |
324 | * @head: the previous &struct rhash_head to continue from | |
325 | * @tbl: the &struct bucket_table | |
326 | * @hash: the hash value / bucket index | |
327 | * @member: name of the &struct rhash_head within the hashable struct. | |
328 | * | |
329 | * This hash chain list-traversal primitive may safely run concurrently with | |
330 | * the _rcu mutation primitives such as rhashtable_insert() as long as the | |
331 | * traversal is guarded by rcu_read_lock(). | |
332 | */ | |
333 | #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \ | |
334 | for (({barrier(); }), \ | |
335 | pos = rht_dereference_bucket_rcu(head, tbl, hash); \ | |
336 | (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ | |
337 | pos = rht_dereference_bucket_rcu(pos->next, tbl, hash)) | |
338 | ||
339 | /** | |
340 | * rht_for_each_entry_rcu - iterate over rcu hash chain of given type | |
341 | * @tpos: the type * to use as a loop cursor. | |
342 | * @pos: the &struct rhash_head to use as a loop cursor. | |
343 | * @tbl: the &struct bucket_table | |
344 | * @hash: the hash value / bucket index | |
345 | * @member: name of the &struct rhash_head within the hashable struct. | |
346 | * | |
347 | * This hash chain list-traversal primitive may safely run concurrently with | |
348 | * the _rcu mutation primitives such as rhashtable_insert() as long as the | |
349 | * traversal is guarded by rcu_read_lock(). | |
350 | */ | |
351 | #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \ | |
352 | rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\ | |
353 | tbl, hash, member) | |
354 | ||
355 | #endif /* _LINUX_RHASHTABLE_H */ |