1 /* 2 * Resizable, Scalable, Concurrent Hash Table 3 * 4 * Copyright (c) 2014 Thomas Graf <[email protected]> 5 * Copyright (c) 2008-2014 Patrick McHardy <[email protected]> 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 * @locks_mask: Mask to apply before accessing locks[] 53 * @locks: Array of spinlocks protecting individual buckets 54 * @buckets: size * hash buckets 55 */ 56 struct bucket_table { 57 size_t size; 58 unsigned int locks_mask; 59 spinlock_t *locks; 60 struct rhash_head __rcu *buckets[]; 61 }; 62 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); 65 66 struct rhashtable; 67 68 /** 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 83 * 84 * Note: when implementing the grow and shrink decision function, min/max 85 * shift must be enforced, otherwise, resizing watermarks they set may be 86 * useless. 87 */ 88 struct rhashtable_params { 89 size_t nelem_hint; 90 size_t key_len; 91 size_t key_offset; 92 size_t head_offset; 93 u32 hash_rnd; 94 size_t max_shift; 95 size_t min_shift; 96 u32 nulls_base; 97 size_t locks_mul; 98 rht_hashfn_t hashfn; 99 rht_obj_hashfn_t obj_hashfn; 100 bool (*grow_decision)(const struct rhashtable *ht, 101 size_t new_size); 102 bool (*shrink_decision)(const struct rhashtable *ht, 103 size_t new_size); 104 }; 105 106 /** 107 * struct rhashtable - Hash table handle 108 * @tbl: Bucket table 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 117 */ 118 struct rhashtable { 119 struct bucket_table __rcu *tbl; 120 struct bucket_table __rcu *future_tbl; 121 atomic_t nelems; 122 atomic_t shift; 123 struct rhashtable_params p; 124 struct work_struct run_work; 125 struct mutex mutex; 126 struct list_head walkers; 127 bool being_destroyed; 128 }; 129 130 /** 131 * struct rhashtable_walker - Hash table walker 132 * @list: List entry on list of walkers 133 * @resize: Resize event occured 134 */ 135 struct rhashtable_walker { 136 struct list_head list; 137 bool resize; 138 }; 139 140 /** 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 147 */ 148 struct rhashtable_iter { 149 struct rhashtable *ht; 150 struct rhash_head *p; 151 struct rhashtable_walker *walker; 152 unsigned int slot; 153 unsigned int skip; 154 }; 155 156 static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash) 157 { 158 return NULLS_MARKER(ht->p.nulls_base + hash); 159 } 160 161 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \ 162 ((ptr) = (typeof(ptr)) rht_marker(ht, hash)) 163 164 static inline bool rht_is_a_nulls(const struct rhash_head *ptr) 165 { 166 return ((unsigned long) ptr & 1); 167 } 168 169 static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr) 170 { 171 return ((unsigned long) ptr) >> 1; 172 } 173 174 #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); 177 #else 178 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht) 179 { 180 return 1; 181 } 182 183 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, 184 u32 hash) 185 { 186 return 1; 187 } 188 #endif /* CONFIG_PROVE_LOCKING */ 189 190 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params); 191 192 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node); 193 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node); 194 195 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); 197 198 int rhashtable_expand(struct rhashtable *ht); 199 int rhashtable_shrink(struct rhashtable *ht); 200 201 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); 204 205 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 *), 209 void *arg); 210 211 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); 216 217 void rhashtable_destroy(struct rhashtable *ht); 218 219 #define rht_dereference(p, ht) \ 220 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht)) 221 222 #define rht_dereference_rcu(p, ht) \ 223 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht)) 224 225 #define rht_dereference_bucket(p, tbl, hash) \ 226 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash)) 227 228 #define rht_dereference_bucket_rcu(p, tbl, hash) \ 229 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash)) 230 231 #define rht_entry(tpos, pos, member) \ 232 ({ tpos = container_of(pos, typeof(*tpos), member); 1; }) 233 234 /** 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 240 */ 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)) 245 246 /** 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 251 */ 252 #define rht_for_each(pos, tbl, hash) \ 253 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash) 254 255 /** 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. 263 */ 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)) 268 269 /** 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. 276 */ 277 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \ 278 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \ 279 tbl, hash, member) 280 281 /** 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. 289 * 290 * This hash chain list-traversal primitive allows for the looped code to 291 * remove the loop cursor from the list. 292 */ 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); \ 298 pos = next, \ 299 next = !rht_is_a_nulls(pos) ? \ 300 rht_dereference_bucket(pos->next, tbl, hash) : NULL) 301 302 /** 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 308 * 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(). 312 */ 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)) 318 319 /** 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 324 * 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(). 328 */ 329 #define rht_for_each_rcu(pos, tbl, hash) \ 330 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash) 331 332 /** 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. 340 * 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(). 344 */ 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)) 350 351 /** 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. 358 * 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(). 362 */ 363 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \ 364 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\ 365 tbl, hash, member) 366 367 #endif /* _LINUX_RHASHTABLE_H */ 368