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7e1e7763 TG |
1 | /* |
2 | * Resizable, Scalable, Concurrent Hash Table | |
3 | * | |
dc0ee268 | 4 | * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> |
7e1e7763 TG |
5 | * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch> |
6 | * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net> | |
7 | * | |
7e1e7763 | 8 | * Code partially derived from nft_hash |
dc0ee268 HX |
9 | * Rewritten with rehash code from br_multicast plus single list |
10 | * pointer as suggested by Josh Triplett | |
7e1e7763 TG |
11 | * |
12 | * This program is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU General Public License version 2 as | |
14 | * published by the Free Software Foundation. | |
15 | */ | |
16 | ||
17 | #ifndef _LINUX_RHASHTABLE_H | |
18 | #define _LINUX_RHASHTABLE_H | |
19 | ||
f2dba9c6 | 20 | #include <linux/compiler.h> |
f89bd6f8 | 21 | #include <linux/list_nulls.h> |
97defe1e | 22 | #include <linux/workqueue.h> |
86b35b64 | 23 | #include <linux/mutex.h> |
02fd97c3 | 24 | #include <linux/rcupdate.h> |
7e1e7763 | 25 | |
f89bd6f8 TG |
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 | ||
02fd97c3 HX |
45 | /* Base bits plus 1 bit for nulls marker */ |
46 | #define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1) | |
47 | ||
7e1e7763 | 48 | struct rhash_head { |
5300fdcb | 49 | struct rhash_head __rcu *next; |
7e1e7763 TG |
50 | }; |
51 | ||
97defe1e TG |
52 | /** |
53 | * struct bucket_table - Table of hash buckets | |
54 | * @size: Number of hash buckets | |
63d512d0 | 55 | * @rehash: Current bucket being rehashed |
988dfbd7 | 56 | * @hash_rnd: Random seed to fold into hash |
97defe1e TG |
57 | * @locks_mask: Mask to apply before accessing locks[] |
58 | * @locks: Array of spinlocks protecting individual buckets | |
eddee5ba | 59 | * @walkers: List of active walkers |
9d901bc0 | 60 | * @rcu: RCU structure for freeing the table |
c4db8848 | 61 | * @future_tbl: Table under construction during rehashing |
97defe1e TG |
62 | * @buckets: size * hash buckets |
63 | */ | |
7e1e7763 | 64 | struct bucket_table { |
63d512d0 HX |
65 | unsigned int size; |
66 | unsigned int rehash; | |
988dfbd7 | 67 | u32 hash_rnd; |
b9ebafbe ED |
68 | unsigned int locks_mask; |
69 | spinlock_t *locks; | |
eddee5ba | 70 | struct list_head walkers; |
9d901bc0 | 71 | struct rcu_head rcu; |
b9ebafbe | 72 | |
c4db8848 HX |
73 | struct bucket_table __rcu *future_tbl; |
74 | ||
b9ebafbe | 75 | struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp; |
7e1e7763 TG |
76 | }; |
77 | ||
02fd97c3 HX |
78 | /** |
79 | * struct rhashtable_compare_arg - Key for the function rhashtable_compare | |
80 | * @ht: Hash table | |
81 | * @key: Key to compare against | |
82 | */ | |
83 | struct rhashtable_compare_arg { | |
84 | struct rhashtable *ht; | |
85 | const void *key; | |
86 | }; | |
87 | ||
7e1e7763 TG |
88 | typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed); |
89 | typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed); | |
02fd97c3 HX |
90 | typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg, |
91 | const void *obj); | |
7e1e7763 TG |
92 | |
93 | struct rhashtable; | |
94 | ||
95 | /** | |
96 | * struct rhashtable_params - Hash table construction parameters | |
97 | * @nelem_hint: Hint on number of elements, should be 75% of desired size | |
98 | * @key_len: Length of key | |
99 | * @key_offset: Offset of key in struct to be hashed | |
100 | * @head_offset: Offset of rhash_head in struct to be hashed | |
c2e213cf HX |
101 | * @max_size: Maximum size while expanding |
102 | * @min_size: Minimum size while shrinking | |
f89bd6f8 | 103 | * @nulls_base: Base value to generate nulls marker |
97defe1e | 104 | * @locks_mul: Number of bucket locks to allocate per cpu (default: 128) |
7e1e7763 TG |
105 | * @hashfn: Function to hash key |
106 | * @obj_hashfn: Function to hash object | |
02fd97c3 | 107 | * @obj_cmpfn: Function to compare key with object |
7e1e7763 TG |
108 | */ |
109 | struct rhashtable_params { | |
110 | size_t nelem_hint; | |
111 | size_t key_len; | |
112 | size_t key_offset; | |
113 | size_t head_offset; | |
c2e213cf HX |
114 | unsigned int max_size; |
115 | unsigned int min_size; | |
f89bd6f8 | 116 | u32 nulls_base; |
97defe1e | 117 | size_t locks_mul; |
7e1e7763 TG |
118 | rht_hashfn_t hashfn; |
119 | rht_obj_hashfn_t obj_hashfn; | |
02fd97c3 | 120 | rht_obj_cmpfn_t obj_cmpfn; |
7e1e7763 TG |
121 | }; |
122 | ||
123 | /** | |
124 | * struct rhashtable - Hash table handle | |
125 | * @tbl: Bucket table | |
126 | * @nelems: Number of elements in table | |
7e1e7763 | 127 | * @p: Configuration parameters |
97defe1e TG |
128 | * @run_work: Deferred worker to expand/shrink asynchronously |
129 | * @mutex: Mutex to protect current/future table swapping | |
130 | * @being_destroyed: True if table is set up for destruction | |
7e1e7763 TG |
131 | */ |
132 | struct rhashtable { | |
133 | struct bucket_table __rcu *tbl; | |
97defe1e | 134 | atomic_t nelems; |
a5b6846f | 135 | bool being_destroyed; |
7e1e7763 | 136 | struct rhashtable_params p; |
57699a40 | 137 | struct work_struct run_work; |
97defe1e | 138 | struct mutex mutex; |
7e1e7763 TG |
139 | }; |
140 | ||
f2dba9c6 HX |
141 | /** |
142 | * struct rhashtable_walker - Hash table walker | |
143 | * @list: List entry on list of walkers | |
eddee5ba | 144 | * @tbl: The table that we were walking over |
f2dba9c6 HX |
145 | */ |
146 | struct rhashtable_walker { | |
147 | struct list_head list; | |
eddee5ba | 148 | struct bucket_table *tbl; |
f2dba9c6 HX |
149 | }; |
150 | ||
151 | /** | |
152 | * struct rhashtable_iter - Hash table iterator, fits into netlink cb | |
153 | * @ht: Table to iterate through | |
154 | * @p: Current pointer | |
155 | * @walker: Associated rhashtable walker | |
156 | * @slot: Current slot | |
157 | * @skip: Number of entries to skip in slot | |
158 | */ | |
159 | struct rhashtable_iter { | |
160 | struct rhashtable *ht; | |
161 | struct rhash_head *p; | |
162 | struct rhashtable_walker *walker; | |
163 | unsigned int slot; | |
164 | unsigned int skip; | |
165 | }; | |
166 | ||
f89bd6f8 TG |
167 | static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash) |
168 | { | |
169 | return NULLS_MARKER(ht->p.nulls_base + hash); | |
170 | } | |
171 | ||
172 | #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \ | |
173 | ((ptr) = (typeof(ptr)) rht_marker(ht, hash)) | |
174 | ||
175 | static inline bool rht_is_a_nulls(const struct rhash_head *ptr) | |
176 | { | |
177 | return ((unsigned long) ptr & 1); | |
178 | } | |
179 | ||
180 | static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr) | |
181 | { | |
182 | return ((unsigned long) ptr) >> 1; | |
183 | } | |
184 | ||
02fd97c3 HX |
185 | static inline void *rht_obj(const struct rhashtable *ht, |
186 | const struct rhash_head *he) | |
187 | { | |
188 | return (char *)he - ht->p.head_offset; | |
189 | } | |
190 | ||
191 | static inline unsigned int rht_bucket_index(const struct bucket_table *tbl, | |
192 | unsigned int hash) | |
193 | { | |
194 | return (hash >> RHT_HASH_RESERVED_SPACE) & (tbl->size - 1); | |
195 | } | |
196 | ||
197 | static inline unsigned int rht_key_hashfn( | |
198 | struct rhashtable *ht, const struct bucket_table *tbl, | |
199 | const void *key, const struct rhashtable_params params) | |
200 | { | |
201 | return rht_bucket_index(tbl, params.hashfn(key, params.key_len ?: | |
202 | ht->p.key_len, | |
203 | tbl->hash_rnd)); | |
204 | } | |
205 | ||
206 | static inline unsigned int rht_head_hashfn( | |
207 | struct rhashtable *ht, const struct bucket_table *tbl, | |
208 | const struct rhash_head *he, const struct rhashtable_params params) | |
209 | { | |
210 | const char *ptr = rht_obj(ht, he); | |
211 | ||
212 | return likely(params.obj_hashfn) ? | |
213 | rht_bucket_index(tbl, params.obj_hashfn(ptr, tbl->hash_rnd)) : | |
214 | rht_key_hashfn(ht, tbl, ptr + params.key_offset, params); | |
215 | } | |
216 | ||
217 | /** | |
218 | * rht_grow_above_75 - returns true if nelems > 0.75 * table-size | |
219 | * @ht: hash table | |
220 | * @tbl: current table | |
221 | */ | |
222 | static inline bool rht_grow_above_75(const struct rhashtable *ht, | |
223 | const struct bucket_table *tbl) | |
224 | { | |
225 | /* Expand table when exceeding 75% load */ | |
226 | return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) && | |
227 | (!ht->p.max_size || tbl->size < ht->p.max_size); | |
228 | } | |
229 | ||
230 | /** | |
231 | * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size | |
232 | * @ht: hash table | |
233 | * @tbl: current table | |
234 | */ | |
235 | static inline bool rht_shrink_below_30(const struct rhashtable *ht, | |
236 | const struct bucket_table *tbl) | |
237 | { | |
238 | /* Shrink table beneath 30% load */ | |
239 | return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) && | |
240 | tbl->size > ht->p.min_size; | |
241 | } | |
242 | ||
243 | /* The bucket lock is selected based on the hash and protects mutations | |
244 | * on a group of hash buckets. | |
245 | * | |
246 | * A maximum of tbl->size/2 bucket locks is allocated. This ensures that | |
247 | * a single lock always covers both buckets which may both contains | |
248 | * entries which link to the same bucket of the old table during resizing. | |
249 | * This allows to simplify the locking as locking the bucket in both | |
250 | * tables during resize always guarantee protection. | |
251 | * | |
252 | * IMPORTANT: When holding the bucket lock of both the old and new table | |
253 | * during expansions and shrinking, the old bucket lock must always be | |
254 | * acquired first. | |
255 | */ | |
256 | static inline spinlock_t *rht_bucket_lock(const struct bucket_table *tbl, | |
257 | unsigned int hash) | |
258 | { | |
259 | return &tbl->locks[hash & tbl->locks_mask]; | |
260 | } | |
261 | ||
7e1e7763 | 262 | #ifdef CONFIG_PROVE_LOCKING |
97defe1e | 263 | int lockdep_rht_mutex_is_held(struct rhashtable *ht); |
88d6ed15 | 264 | int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash); |
7e1e7763 | 265 | #else |
97defe1e | 266 | static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht) |
7e1e7763 TG |
267 | { |
268 | return 1; | |
269 | } | |
88d6ed15 TG |
270 | |
271 | static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, | |
272 | u32 hash) | |
273 | { | |
274 | return 1; | |
275 | } | |
7e1e7763 TG |
276 | #endif /* CONFIG_PROVE_LOCKING */ |
277 | ||
488fb86e HX |
278 | int rhashtable_init(struct rhashtable *ht, |
279 | const struct rhashtable_params *params); | |
7e1e7763 | 280 | |
02fd97c3 HX |
281 | int rhashtable_insert_slow(struct rhashtable *ht, const void *key, |
282 | struct rhash_head *obj, | |
283 | struct bucket_table *old_tbl); | |
7e1e7763 | 284 | |
6eba8224 TG |
285 | int rhashtable_expand(struct rhashtable *ht); |
286 | int rhashtable_shrink(struct rhashtable *ht); | |
7e1e7763 | 287 | |
f2dba9c6 HX |
288 | int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter); |
289 | void rhashtable_walk_exit(struct rhashtable_iter *iter); | |
290 | int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU); | |
291 | void *rhashtable_walk_next(struct rhashtable_iter *iter); | |
292 | void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU); | |
293 | ||
97defe1e | 294 | void rhashtable_destroy(struct rhashtable *ht); |
7e1e7763 TG |
295 | |
296 | #define rht_dereference(p, ht) \ | |
297 | rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht)) | |
298 | ||
299 | #define rht_dereference_rcu(p, ht) \ | |
300 | rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht)) | |
301 | ||
88d6ed15 TG |
302 | #define rht_dereference_bucket(p, tbl, hash) \ |
303 | rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash)) | |
7e1e7763 | 304 | |
88d6ed15 TG |
305 | #define rht_dereference_bucket_rcu(p, tbl, hash) \ |
306 | rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash)) | |
307 | ||
308 | #define rht_entry(tpos, pos, member) \ | |
309 | ({ tpos = container_of(pos, typeof(*tpos), member); 1; }) | |
7e1e7763 TG |
310 | |
311 | /** | |
88d6ed15 TG |
312 | * rht_for_each_continue - continue iterating over hash chain |
313 | * @pos: the &struct rhash_head to use as a loop cursor. | |
314 | * @head: the previous &struct rhash_head to continue from | |
315 | * @tbl: the &struct bucket_table | |
316 | * @hash: the hash value / bucket index | |
7e1e7763 | 317 | */ |
88d6ed15 TG |
318 | #define rht_for_each_continue(pos, head, tbl, hash) \ |
319 | for (pos = rht_dereference_bucket(head, tbl, hash); \ | |
f89bd6f8 | 320 | !rht_is_a_nulls(pos); \ |
88d6ed15 TG |
321 | pos = rht_dereference_bucket((pos)->next, tbl, hash)) |
322 | ||
323 | /** | |
324 | * rht_for_each - iterate over hash chain | |
325 | * @pos: the &struct rhash_head to use as a loop cursor. | |
326 | * @tbl: the &struct bucket_table | |
327 | * @hash: the hash value / bucket index | |
328 | */ | |
329 | #define rht_for_each(pos, tbl, hash) \ | |
330 | rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash) | |
331 | ||
332 | /** | |
333 | * rht_for_each_entry_continue - continue iterating over 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. | |
340 | */ | |
341 | #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \ | |
342 | for (pos = rht_dereference_bucket(head, tbl, hash); \ | |
f89bd6f8 | 343 | (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ |
88d6ed15 | 344 | pos = rht_dereference_bucket((pos)->next, tbl, hash)) |
7e1e7763 TG |
345 | |
346 | /** | |
347 | * rht_for_each_entry - iterate over hash chain of given type | |
88d6ed15 TG |
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. | |
7e1e7763 | 353 | */ |
88d6ed15 TG |
354 | #define rht_for_each_entry(tpos, pos, tbl, hash, member) \ |
355 | rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \ | |
356 | tbl, hash, member) | |
7e1e7763 TG |
357 | |
358 | /** | |
359 | * rht_for_each_entry_safe - safely iterate over hash chain of given type | |
88d6ed15 TG |
360 | * @tpos: the type * to use as a loop cursor. |
361 | * @pos: the &struct rhash_head to use as a loop cursor. | |
362 | * @next: the &struct rhash_head to use as next in loop cursor. | |
363 | * @tbl: the &struct bucket_table | |
364 | * @hash: the hash value / bucket index | |
365 | * @member: name of the &struct rhash_head within the hashable struct. | |
7e1e7763 TG |
366 | * |
367 | * This hash chain list-traversal primitive allows for the looped code to | |
368 | * remove the loop cursor from the list. | |
369 | */ | |
88d6ed15 TG |
370 | #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \ |
371 | for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \ | |
f89bd6f8 TG |
372 | next = !rht_is_a_nulls(pos) ? \ |
373 | rht_dereference_bucket(pos->next, tbl, hash) : NULL; \ | |
374 | (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ | |
607954b0 PM |
375 | pos = next, \ |
376 | next = !rht_is_a_nulls(pos) ? \ | |
377 | rht_dereference_bucket(pos->next, tbl, hash) : NULL) | |
88d6ed15 TG |
378 | |
379 | /** | |
380 | * rht_for_each_rcu_continue - continue iterating over rcu hash chain | |
381 | * @pos: the &struct rhash_head to use as a loop cursor. | |
382 | * @head: the previous &struct rhash_head to continue from | |
383 | * @tbl: the &struct bucket_table | |
384 | * @hash: the hash value / bucket index | |
385 | * | |
386 | * This hash chain list-traversal primitive may safely run concurrently with | |
387 | * the _rcu mutation primitives such as rhashtable_insert() as long as the | |
388 | * traversal is guarded by rcu_read_lock(). | |
389 | */ | |
390 | #define rht_for_each_rcu_continue(pos, head, tbl, hash) \ | |
391 | for (({barrier(); }), \ | |
392 | pos = rht_dereference_bucket_rcu(head, tbl, hash); \ | |
f89bd6f8 | 393 | !rht_is_a_nulls(pos); \ |
88d6ed15 | 394 | pos = rcu_dereference_raw(pos->next)) |
7e1e7763 TG |
395 | |
396 | /** | |
397 | * rht_for_each_rcu - iterate over rcu hash chain | |
88d6ed15 TG |
398 | * @pos: the &struct rhash_head to use as a loop cursor. |
399 | * @tbl: the &struct bucket_table | |
400 | * @hash: the hash value / bucket index | |
7e1e7763 TG |
401 | * |
402 | * This hash chain list-traversal primitive may safely run concurrently with | |
88d6ed15 | 403 | * the _rcu mutation primitives such as rhashtable_insert() as long as the |
7e1e7763 TG |
404 | * traversal is guarded by rcu_read_lock(). |
405 | */ | |
88d6ed15 TG |
406 | #define rht_for_each_rcu(pos, tbl, hash) \ |
407 | rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash) | |
408 | ||
409 | /** | |
410 | * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain | |
411 | * @tpos: the type * to use as a loop cursor. | |
412 | * @pos: the &struct rhash_head to use as a loop cursor. | |
413 | * @head: the previous &struct rhash_head to continue from | |
414 | * @tbl: the &struct bucket_table | |
415 | * @hash: the hash value / bucket index | |
416 | * @member: name of the &struct rhash_head within the hashable struct. | |
417 | * | |
418 | * This hash chain list-traversal primitive may safely run concurrently with | |
419 | * the _rcu mutation primitives such as rhashtable_insert() as long as the | |
420 | * traversal is guarded by rcu_read_lock(). | |
421 | */ | |
422 | #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \ | |
423 | for (({barrier(); }), \ | |
424 | pos = rht_dereference_bucket_rcu(head, tbl, hash); \ | |
f89bd6f8 | 425 | (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ |
88d6ed15 | 426 | pos = rht_dereference_bucket_rcu(pos->next, tbl, hash)) |
7e1e7763 TG |
427 | |
428 | /** | |
429 | * rht_for_each_entry_rcu - iterate over rcu hash chain of given type | |
88d6ed15 TG |
430 | * @tpos: the type * to use as a loop cursor. |
431 | * @pos: the &struct rhash_head to use as a loop cursor. | |
432 | * @tbl: the &struct bucket_table | |
433 | * @hash: the hash value / bucket index | |
434 | * @member: name of the &struct rhash_head within the hashable struct. | |
7e1e7763 TG |
435 | * |
436 | * This hash chain list-traversal primitive may safely run concurrently with | |
88d6ed15 | 437 | * the _rcu mutation primitives such as rhashtable_insert() as long as the |
7e1e7763 TG |
438 | * traversal is guarded by rcu_read_lock(). |
439 | */ | |
88d6ed15 TG |
440 | #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \ |
441 | rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\ | |
442 | tbl, hash, member) | |
7e1e7763 | 443 | |
02fd97c3 HX |
444 | static inline int rhashtable_compare(struct rhashtable_compare_arg *arg, |
445 | const void *obj) | |
446 | { | |
447 | struct rhashtable *ht = arg->ht; | |
448 | const char *ptr = obj; | |
449 | ||
450 | return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len); | |
451 | } | |
452 | ||
453 | /** | |
454 | * rhashtable_lookup_fast - search hash table, inlined version | |
455 | * @ht: hash table | |
456 | * @key: the pointer to the key | |
457 | * @params: hash table parameters | |
458 | * | |
459 | * Computes the hash value for the key and traverses the bucket chain looking | |
460 | * for a entry with an identical key. The first matching entry is returned. | |
461 | * | |
462 | * Returns the first entry on which the compare function returned true. | |
463 | */ | |
464 | static inline void *rhashtable_lookup_fast( | |
465 | struct rhashtable *ht, const void *key, | |
466 | const struct rhashtable_params params) | |
467 | { | |
468 | struct rhashtable_compare_arg arg = { | |
469 | .ht = ht, | |
470 | .key = key, | |
471 | }; | |
472 | const struct bucket_table *tbl; | |
473 | struct rhash_head *he; | |
474 | unsigned hash; | |
475 | ||
476 | rcu_read_lock(); | |
477 | ||
478 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
479 | restart: | |
480 | hash = rht_key_hashfn(ht, tbl, key, params); | |
481 | rht_for_each_rcu(he, tbl, hash) { | |
482 | if (params.obj_cmpfn ? | |
483 | params.obj_cmpfn(&arg, rht_obj(ht, he)) : | |
484 | rhashtable_compare(&arg, rht_obj(ht, he))) | |
485 | continue; | |
486 | rcu_read_unlock(); | |
487 | return rht_obj(ht, he); | |
488 | } | |
489 | ||
490 | /* Ensure we see any new tables. */ | |
491 | smp_rmb(); | |
492 | ||
493 | tbl = rht_dereference_rcu(tbl->future_tbl, ht); | |
494 | if (unlikely(tbl)) | |
495 | goto restart; | |
496 | rcu_read_unlock(); | |
497 | ||
498 | return NULL; | |
499 | } | |
500 | ||
501 | static inline int __rhashtable_insert_fast( | |
502 | struct rhashtable *ht, const void *key, struct rhash_head *obj, | |
503 | const struct rhashtable_params params) | |
504 | { | |
505 | struct rhashtable_compare_arg arg = { | |
506 | .ht = ht, | |
507 | .key = key, | |
508 | }; | |
509 | int err = -EEXIST; | |
510 | struct bucket_table *tbl, *new_tbl; | |
511 | struct rhash_head *head; | |
512 | spinlock_t *lock; | |
513 | unsigned hash; | |
514 | ||
515 | rcu_read_lock(); | |
516 | ||
517 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
518 | hash = rht_head_hashfn(ht, tbl, obj, params); | |
519 | lock = rht_bucket_lock(tbl, hash); | |
520 | ||
521 | spin_lock_bh(lock); | |
522 | ||
523 | /* Because we have already taken the bucket lock in tbl, | |
524 | * if we find that future_tbl is not yet visible then | |
525 | * that guarantees all other insertions of the same entry | |
526 | * will also grab the bucket lock in tbl because until | |
527 | * the rehash completes ht->tbl won't be changed. | |
528 | */ | |
529 | new_tbl = rht_dereference_rcu(tbl->future_tbl, ht); | |
530 | if (unlikely(new_tbl)) { | |
531 | err = rhashtable_insert_slow(ht, key, obj, new_tbl); | |
532 | goto out; | |
533 | } | |
534 | ||
535 | if (!key) | |
536 | goto skip_lookup; | |
537 | ||
538 | rht_for_each(head, tbl, hash) { | |
539 | if (unlikely(!(params.obj_cmpfn ? | |
540 | params.obj_cmpfn(&arg, rht_obj(ht, head)) : | |
541 | rhashtable_compare(&arg, rht_obj(ht, head))))) | |
542 | goto out; | |
543 | } | |
544 | ||
545 | skip_lookup: | |
546 | err = 0; | |
547 | ||
548 | head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash); | |
549 | ||
550 | RCU_INIT_POINTER(obj->next, head); | |
551 | ||
552 | rcu_assign_pointer(tbl->buckets[hash], obj); | |
553 | ||
554 | atomic_inc(&ht->nelems); | |
555 | if (rht_grow_above_75(ht, tbl)) | |
556 | schedule_work(&ht->run_work); | |
557 | ||
558 | out: | |
559 | spin_unlock_bh(lock); | |
560 | rcu_read_unlock(); | |
561 | ||
562 | return err; | |
563 | } | |
564 | ||
565 | /** | |
566 | * rhashtable_insert_fast - insert object into hash table | |
567 | * @ht: hash table | |
568 | * @obj: pointer to hash head inside object | |
569 | * @params: hash table parameters | |
570 | * | |
571 | * Will take a per bucket spinlock to protect against mutual mutations | |
572 | * on the same bucket. Multiple insertions may occur in parallel unless | |
573 | * they map to the same bucket lock. | |
574 | * | |
575 | * It is safe to call this function from atomic context. | |
576 | * | |
577 | * Will trigger an automatic deferred table resizing if the size grows | |
578 | * beyond the watermark indicated by grow_decision() which can be passed | |
579 | * to rhashtable_init(). | |
580 | */ | |
581 | static inline int rhashtable_insert_fast( | |
582 | struct rhashtable *ht, struct rhash_head *obj, | |
583 | const struct rhashtable_params params) | |
584 | { | |
585 | return __rhashtable_insert_fast(ht, NULL, obj, params); | |
586 | } | |
587 | ||
588 | /** | |
589 | * rhashtable_lookup_insert_fast - lookup and insert object into hash table | |
590 | * @ht: hash table | |
591 | * @obj: pointer to hash head inside object | |
592 | * @params: hash table parameters | |
593 | * | |
594 | * Locks down the bucket chain in both the old and new table if a resize | |
595 | * is in progress to ensure that writers can't remove from the old table | |
596 | * and can't insert to the new table during the atomic operation of search | |
597 | * and insertion. Searches for duplicates in both the old and new table if | |
598 | * a resize is in progress. | |
599 | * | |
600 | * This lookup function may only be used for fixed key hash table (key_len | |
601 | * parameter set). It will BUG() if used inappropriately. | |
602 | * | |
603 | * It is safe to call this function from atomic context. | |
604 | * | |
605 | * Will trigger an automatic deferred table resizing if the size grows | |
606 | * beyond the watermark indicated by grow_decision() which can be passed | |
607 | * to rhashtable_init(). | |
608 | */ | |
609 | static inline int rhashtable_lookup_insert_fast( | |
610 | struct rhashtable *ht, struct rhash_head *obj, | |
611 | const struct rhashtable_params params) | |
612 | { | |
613 | const char *key = rht_obj(ht, obj); | |
614 | ||
615 | BUG_ON(ht->p.obj_hashfn); | |
616 | ||
617 | return __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj, | |
618 | params); | |
619 | } | |
620 | ||
621 | /** | |
622 | * rhashtable_lookup_insert_key - search and insert object to hash table | |
623 | * with explicit key | |
624 | * @ht: hash table | |
625 | * @key: key | |
626 | * @obj: pointer to hash head inside object | |
627 | * @params: hash table parameters | |
628 | * | |
629 | * Locks down the bucket chain in both the old and new table if a resize | |
630 | * is in progress to ensure that writers can't remove from the old table | |
631 | * and can't insert to the new table during the atomic operation of search | |
632 | * and insertion. Searches for duplicates in both the old and new table if | |
633 | * a resize is in progress. | |
634 | * | |
635 | * Lookups may occur in parallel with hashtable mutations and resizing. | |
636 | * | |
637 | * Will trigger an automatic deferred table resizing if the size grows | |
638 | * beyond the watermark indicated by grow_decision() which can be passed | |
639 | * to rhashtable_init(). | |
640 | * | |
641 | * Returns zero on success. | |
642 | */ | |
643 | static inline int rhashtable_lookup_insert_key( | |
644 | struct rhashtable *ht, const void *key, struct rhash_head *obj, | |
645 | const struct rhashtable_params params) | |
646 | { | |
647 | BUG_ON(!ht->p.obj_hashfn || !key); | |
648 | ||
649 | return __rhashtable_insert_fast(ht, key, obj, params); | |
650 | } | |
651 | ||
652 | static inline int __rhashtable_remove_fast( | |
653 | struct rhashtable *ht, struct bucket_table *tbl, | |
654 | struct rhash_head *obj, const struct rhashtable_params params) | |
655 | { | |
656 | struct rhash_head __rcu **pprev; | |
657 | struct rhash_head *he; | |
658 | spinlock_t * lock; | |
659 | unsigned hash; | |
660 | int err = -ENOENT; | |
661 | ||
662 | hash = rht_head_hashfn(ht, tbl, obj, params); | |
663 | lock = rht_bucket_lock(tbl, hash); | |
664 | ||
665 | spin_lock_bh(lock); | |
666 | ||
667 | pprev = &tbl->buckets[hash]; | |
668 | rht_for_each(he, tbl, hash) { | |
669 | if (he != obj) { | |
670 | pprev = &he->next; | |
671 | continue; | |
672 | } | |
673 | ||
674 | rcu_assign_pointer(*pprev, obj->next); | |
675 | err = 0; | |
676 | break; | |
677 | } | |
678 | ||
679 | spin_unlock_bh(lock); | |
680 | ||
681 | return err; | |
682 | } | |
683 | ||
684 | /** | |
685 | * rhashtable_remove_fast - remove object from hash table | |
686 | * @ht: hash table | |
687 | * @obj: pointer to hash head inside object | |
688 | * @params: hash table parameters | |
689 | * | |
690 | * Since the hash chain is single linked, the removal operation needs to | |
691 | * walk the bucket chain upon removal. The removal operation is thus | |
692 | * considerable slow if the hash table is not correctly sized. | |
693 | * | |
694 | * Will automatically shrink the table via rhashtable_expand() if the | |
695 | * shrink_decision function specified at rhashtable_init() returns true. | |
696 | * | |
697 | * Returns zero on success, -ENOENT if the entry could not be found. | |
698 | */ | |
699 | static inline int rhashtable_remove_fast( | |
700 | struct rhashtable *ht, struct rhash_head *obj, | |
701 | const struct rhashtable_params params) | |
702 | { | |
703 | struct bucket_table *tbl; | |
704 | int err; | |
705 | ||
706 | rcu_read_lock(); | |
707 | ||
708 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
709 | ||
710 | /* Because we have already taken (and released) the bucket | |
711 | * lock in old_tbl, if we find that future_tbl is not yet | |
712 | * visible then that guarantees the entry to still be in | |
713 | * the old tbl if it exists. | |
714 | */ | |
715 | while ((err = __rhashtable_remove_fast(ht, tbl, obj, params)) && | |
716 | (tbl = rht_dereference_rcu(tbl->future_tbl, ht))) | |
717 | ; | |
718 | ||
719 | if (err) | |
720 | goto out; | |
721 | ||
722 | atomic_dec(&ht->nelems); | |
723 | if (rht_shrink_below_30(ht, tbl)) | |
724 | schedule_work(&ht->run_work); | |
725 | ||
726 | out: | |
727 | rcu_read_unlock(); | |
728 | ||
729 | return err; | |
730 | } | |
731 | ||
7e1e7763 | 732 | #endif /* _LINUX_RHASHTABLE_H */ |