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/list_nulls.h>
  22 #include <linux/workqueue.h>
  23 #include <linux/mutex.h>
  24
  25 /*
  26  * The end of the chain is marked with a special nulls marks which has
  27  * the following format:
  28  *
  29  * +-------+-----------------------------------------------------+-+
  30  * | Base  |                      Hash                           |1|
  31  * +-------+-----------------------------------------------------+-+
  32  *
  33  * Base (4 bits) : Reserved to distinguish between multiple tables.
  34  *                 Specified via &struct rhashtable_params.nulls_base.
  35  * Hash (27 bits): Full hash (unmasked) of first element added to bucket
  36  * 1 (1 bit)     : Nulls marker (always set)
  37  *
  38  * The remaining bits of the next pointer remain unused for now.
  39  */
  40 #define RHT_BASE_BITS           4
  41 #define RHT_HASH_BITS           27
  42 #define RHT_BASE_SHIFT          RHT_HASH_BITS
  43
  44 struct rhash_head {
  45         struct rhash_head __rcu         *next;
  46 };
  47
  48 /**
  49  * struct bucket_table - Table of hash buckets
  50  * @size: Number of hash buckets
  51  * @locks_mask: Mask to apply before accessing locks[]
  52  * @locks: Array of spinlocks protecting individual buckets
  53  * @buckets: size * hash buckets
  54  */
  55 struct bucket_table {
  56         size_t                          size;
  57         unsigned int                    locks_mask;
  58         spinlock_t                      *locks;
  59         struct rhash_head __rcu         *buckets[];
  60 };
  61
  62 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
  63 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
  64
  65 struct rhashtable;
  66
  67 /**
  68  * struct rhashtable_params - Hash table construction parameters
  69  * @nelem_hint: Hint on number of elements, should be 75% of desired size
  70  * @key_len: Length of key
  71  * @key_offset: Offset of key in struct to be hashed
  72  * @head_offset: Offset of rhash_head in struct to be hashed
  73  * @hash_rnd: Seed to use while hashing
  74  * @max_shift: Maximum number of shifts while expanding
  75  * @min_shift: Minimum number of shifts while shrinking
  76  * @nulls_base: Base value to generate nulls marker
  77  * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
  78  * @hashfn: Function to hash key
  79  * @obj_hashfn: Function to hash object
  80  * @grow_decision: If defined, may return true if table should expand
  81  * @shrink_decision: If defined, may return true if table should shrink
  82  *
  83  * Note: when implementing the grow and shrink decision function, min/max
  84  * shift must be enforced, otherwise, resizing watermarks they set may be
  85  * useless.
  86  */
  87 struct rhashtable_params {
  88         size_t                  nelem_hint;
  89         size_t                  key_len;
  90         size_t                  key_offset;
  91         size_t                  head_offset;
  92         u32                     hash_rnd;
  93         size_t                  max_shift;
  94         size_t                  min_shift;
  95         u32                     nulls_base;
  96         size_t                  locks_mul;
  97         rht_hashfn_t            hashfn;
  98         rht_obj_hashfn_t        obj_hashfn;
  99         bool                    (*grow_decision)(const struct rhashtable *ht,
 100                                                  size_t new_size);
 101         bool                    (*shrink_decision)(const struct rhashtable *ht,
 102                                                    size_t new_size);
 103 };
 104
 105 /**
 106  * struct rhashtable - Hash table handle
 107  * @tbl: Bucket table
 108  * @future_tbl: Table under construction during expansion/shrinking
 109  * @nelems: Number of elements in table
 110  * @shift: Current size (1 << shift)
 111  * @p: Configuration parameters
 112  * @run_work: Deferred worker to expand/shrink asynchronously
 113  * @mutex: Mutex to protect current/future table swapping
 114  * @being_destroyed: True if table is set up for destruction
 115  */
 116 struct rhashtable {
 117         struct bucket_table __rcu       *tbl;
 118         struct bucket_table __rcu       *future_tbl;
 119         atomic_t                        nelems;
 120         atomic_t                        shift;
 121         struct rhashtable_params        p;
 122         struct work_struct              run_work;
 123         struct mutex                    mutex;
 124         bool                            being_destroyed;
 125 };
 126
 127 static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
 128 {
 129         return NULLS_MARKER(ht->p.nulls_base + hash);
 130 }
 131
 132 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
 133         ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
 134
 135 static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
 136 {
 137         return ((unsigned long) ptr & 1);
 138 }
 139
 140 static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
 141 {
 142         return ((unsigned long) ptr) >> 1;
 143 }
 144
 145 #ifdef CONFIG_PROVE_LOCKING
 146 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
 147 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
 148 #else
 149 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
 150 {
 151         return 1;
 152 }
 153
 154 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
 155                                              u32 hash)
 156 {
 157         return 1;
 158 }
 159 #endif /* CONFIG_PROVE_LOCKING */
 160
 161 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
 162
 163 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
 164 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
 165
 166 bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size);
 167 bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size);
 168
 169 int rhashtable_expand(struct rhashtable *ht);
 170 int rhashtable_shrink(struct rhashtable *ht);
 171
 172 void *rhashtable_lookup(struct rhashtable *ht, const void *key);
 173 void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
 174                                 bool (*compare)(void *, void *), void *arg);
 175
 176 bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
 177 bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
 178                                       struct rhash_head *obj,
 179                                       bool (*compare)(void *, void *),
 180                                       void *arg);
 181
 182 void rhashtable_destroy(struct rhashtable *ht);
 183
 184 #define rht_dereference(p, ht) \
 185         rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
 186
 187 #define rht_dereference_rcu(p, ht) \
 188         rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
 189
 190 #define rht_dereference_bucket(p, tbl, hash) \
 191         rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
 192
 193 #define rht_dereference_bucket_rcu(p, tbl, hash) \
 194         rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
 195
 196 #define rht_entry(tpos, pos, member) \
 197         ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
 198
 199 /**
 200  * rht_for_each_continue - continue iterating over hash chain
 201  * @pos:        the &struct rhash_head to use as a loop cursor.
 202  * @head:       the previous &struct rhash_head to continue from
 203  * @tbl:        the &struct bucket_table
 204  * @hash:       the hash value / bucket index
 205  */
 206 #define rht_for_each_continue(pos, head, tbl, hash) \
 207         for (pos = rht_dereference_bucket(head, tbl, hash); \
 208              !rht_is_a_nulls(pos); \
 209              pos = rht_dereference_bucket((pos)->next, tbl, hash))
 210
 211 /**
 212  * rht_for_each - iterate over hash chain
 213  * @pos:        the &struct rhash_head to use as a loop cursor.
 214  * @tbl:        the &struct bucket_table
 215  * @hash:       the hash value / bucket index
 216  */
 217 #define rht_for_each(pos, tbl, hash) \
 218         rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
 219
 220 /**
 221  * rht_for_each_entry_continue - continue iterating over hash chain
 222  * @tpos:       the type * to use as a loop cursor.
 223  * @pos:        the &struct rhash_head to use as a loop cursor.
 224  * @head:       the previous &struct rhash_head to continue from
 225  * @tbl:        the &struct bucket_table
 226  * @hash:       the hash value / bucket index
 227  * @member:     name of the &struct rhash_head within the hashable struct.
 228  */
 229 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
 230         for (pos = rht_dereference_bucket(head, tbl, hash);             \
 231              (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member);    \
 232              pos = rht_dereference_bucket((pos)->next, tbl, hash))
 233
 234 /**
 235  * rht_for_each_entry - iterate over hash chain of given type
 236  * @tpos:       the type * to use as a loop cursor.
 237  * @pos:        the &struct rhash_head to use as a loop cursor.
 238  * @tbl:        the &struct bucket_table
 239  * @hash:       the hash value / bucket index
 240  * @member:     name of the &struct rhash_head within the hashable struct.
 241  */
 242 #define rht_for_each_entry(tpos, pos, tbl, hash, member)                \
 243         rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash],    \
 244                                     tbl, hash, member)
 245
 246 /**
 247  * rht_for_each_entry_safe - safely iterate over hash chain of given type
 248  * @tpos:       the type * to use as a loop cursor.
 249  * @pos:        the &struct rhash_head to use as a loop cursor.
 250  * @next:       the &struct rhash_head to use as next in loop cursor.
 251  * @tbl:        the &struct bucket_table
 252  * @hash:       the hash value / bucket index
 253  * @member:     name of the &struct rhash_head within the hashable struct.
 254  *
 255  * This hash chain list-traversal primitive allows for the looped code to
 256  * remove the loop cursor from the list.
 257  */
 258 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member)         \
 259         for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
 260              next = !rht_is_a_nulls(pos) ?                                  \
 261                        rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
 262              (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member);        \
 263              pos = next,                                                    \
 264              next = !rht_is_a_nulls(pos) ?                                  \
 265                        rht_dereference_bucket(pos->next, tbl, hash) : NULL)
 266
 267 /**
 268  * rht_for_each_rcu_continue - continue iterating over rcu hash chain
 269  * @pos:        the &struct rhash_head to use as a loop cursor.
 270  * @head:       the previous &struct rhash_head to continue from
 271  * @tbl:        the &struct bucket_table
 272  * @hash:       the hash value / bucket index
 273  *
 274  * This hash chain list-traversal primitive may safely run concurrently with
 275  * the _rcu mutation primitives such as rhashtable_insert() as long as the
 276  * traversal is guarded by rcu_read_lock().
 277  */
 278 #define rht_for_each_rcu_continue(pos, head, tbl, hash)                 \
 279         for (({barrier(); }),                                           \
 280              pos = rht_dereference_bucket_rcu(head, tbl, hash);         \
 281              !rht_is_a_nulls(pos);                                      \
 282              pos = rcu_dereference_raw(pos->next))
 283
 284 /**
 285  * rht_for_each_rcu - iterate over rcu hash chain
 286  * @pos:        the &struct rhash_head to use as a loop cursor.
 287  * @tbl:        the &struct bucket_table
 288  * @hash:       the hash value / bucket index
 289  *
 290  * This hash chain list-traversal primitive may safely run concurrently with
 291  * the _rcu mutation primitives such as rhashtable_insert() as long as the
 292  * traversal is guarded by rcu_read_lock().
 293  */
 294 #define rht_for_each_rcu(pos, tbl, hash)                                \
 295         rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
 296
 297 /**
 298  * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
 299  * @tpos:       the type * to use as a loop cursor.
 300  * @pos:        the &struct rhash_head to use as a loop cursor.
 301  * @head:       the previous &struct rhash_head to continue from
 302  * @tbl:        the &struct bucket_table
 303  * @hash:       the hash value / bucket index
 304  * @member:     name of the &struct rhash_head within the hashable struct.
 305  *
 306  * This hash chain list-traversal primitive may safely run concurrently with
 307  * the _rcu mutation primitives such as rhashtable_insert() as long as the
 308  * traversal is guarded by rcu_read_lock().
 309  */
 310 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
 311         for (({barrier(); }),                                               \
 312              pos = rht_dereference_bucket_rcu(head, tbl, hash);             \
 313              (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member);        \
 314              pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
 315
 316 /**
 317  * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
 318  * @tpos:       the type * to use as a loop cursor.
 319  * @pos:        the &struct rhash_head to use as a loop cursor.
 320  * @tbl:        the &struct bucket_table
 321  * @hash:       the hash value / bucket index
 322  * @member:     name of the &struct rhash_head within the hashable struct.
 323  *
 324  * This hash chain list-traversal primitive may safely run concurrently with
 325  * the _rcu mutation primitives such as rhashtable_insert() as long as the
 326  * traversal is guarded by rcu_read_lock().
 327  */
 328 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member)            \
 329         rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
 330                                         tbl, hash, member)
 331
 332 #endif /* _LINUX_RHASHTABLE_H */