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 * @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 61 struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp; 62 }; 63 64 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed); 65 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed); 66 67 struct rhashtable; 68 69 /** 70 * struct rhashtable_params - Hash table construction parameters 71 * @nelem_hint: Hint on number of elements, should be 75% of desired size 72 * @key_len: Length of key 73 * @key_offset: Offset of key in struct to be hashed 74 * @head_offset: Offset of rhash_head in struct to be hashed 75 * @hash_rnd: Seed to use while hashing 76 * @max_shift: Maximum number of shifts while expanding 77 * @min_shift: Minimum number of shifts while shrinking 78 * @nulls_base: Base value to generate nulls marker 79 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128) 80 * @hashfn: Function to hash key 81 * @obj_hashfn: Function to hash object 82 */ 83 struct rhashtable_params { 84 size_t nelem_hint; 85 size_t key_len; 86 size_t key_offset; 87 size_t head_offset; 88 u32 hash_rnd; 89 size_t max_shift; 90 size_t min_shift; 91 u32 nulls_base; 92 size_t locks_mul; 93 rht_hashfn_t hashfn; 94 rht_obj_hashfn_t obj_hashfn; 95 }; 96 97 /** 98 * struct rhashtable - Hash table handle 99 * @tbl: Bucket table 100 * @future_tbl: Table under construction during expansion/shrinking 101 * @nelems: Number of elements in table 102 * @shift: Current size (1 << shift) 103 * @p: Configuration parameters 104 * @run_work: Deferred worker to expand/shrink asynchronously 105 * @mutex: Mutex to protect current/future table swapping 106 * @walkers: List of active walkers 107 * @being_destroyed: True if table is set up for destruction 108 */ 109 struct rhashtable { 110 struct bucket_table __rcu *tbl; 111 struct bucket_table __rcu *future_tbl; 112 atomic_t nelems; 113 atomic_t shift; 114 struct rhashtable_params p; 115 struct work_struct run_work; 116 struct mutex mutex; 117 struct list_head walkers; 118 bool being_destroyed; 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 */ 356