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
  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 */