include/linux/rhashtable.h

   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         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 */