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/rculist.h>
  22
  23 struct rhash_head {
  24         struct rhash_head __rcu         *next;
  25 };
  26
  27 #define INIT_HASH_HEAD(ptr) ((ptr)->next = NULL)
  28
  29 struct bucket_table {
  30         size_t                          size;
  31         struct rhash_head __rcu         *buckets[];
  32 };
  33
  34 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
  35 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
  36
  37 struct rhashtable;
  38
  39 /**
  40  * struct rhashtable_params - Hash table construction parameters
  41  * @nelem_hint: Hint on number of elements, should be 75% of desired size
  42  * @key_len: Length of key
  43  * @key_offset: Offset of key in struct to be hashed
  44  * @head_offset: Offset of rhash_head in struct to be hashed
  45  * @hash_rnd: Seed to use while hashing
  46  * @max_shift: Maximum number of shifts while expanding
  47  * @min_shift: Minimum number of shifts while shrinking
  48  * @hashfn: Function to hash key
  49  * @obj_hashfn: Function to hash object
  50  * @grow_decision: If defined, may return true if table should expand
  51  * @shrink_decision: If defined, may return true if table should shrink
  52  * @mutex_is_held: Must return true if protecting mutex is held
  53  */
  54 struct rhashtable_params {
  55         size_t                  nelem_hint;
  56         size_t                  key_len;
  57         size_t                  key_offset;
  58         size_t                  head_offset;
  59         u32                     hash_rnd;
  60         size_t                  max_shift;
  61         size_t                  min_shift;
  62         rht_hashfn_t            hashfn;
  63         rht_obj_hashfn_t        obj_hashfn;
  64         bool                    (*grow_decision)(const struct rhashtable *ht,
  65                                                  size_t new_size);
  66         bool                    (*shrink_decision)(const struct rhashtable *ht,
  67                                                    size_t new_size);
  68         int                     (*mutex_is_held)(void);
  69 };
  70
  71 /**
  72  * struct rhashtable - Hash table handle
  73  * @tbl: Bucket table
  74  * @nelems: Number of elements in table
  75  * @shift: Current size (1 << shift)
  76  * @p: Configuration parameters
  77  */
  78 struct rhashtable {
  79         struct bucket_table __rcu       *tbl;
  80         size_t                          nelems;
  81         size_t                          shift;
  82         struct rhashtable_params        p;
  83 };
  84
  85 #ifdef CONFIG_PROVE_LOCKING
  86 int lockdep_rht_mutex_is_held(const struct rhashtable *ht);
  87 #else
  88 static inline int lockdep_rht_mutex_is_held(const struct rhashtable *ht)
  89 {
  90         return 1;
  91 }
  92 #endif /* CONFIG_PROVE_LOCKING */
  93
  94 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
  95
  96 u32 rhashtable_hashfn(const struct rhashtable *ht, const void *key, u32 len);
  97 u32 rhashtable_obj_hashfn(const struct rhashtable *ht, void *ptr);
  98
  99 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node, gfp_t);
 100 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node, gfp_t);
 101 void rhashtable_remove_pprev(struct rhashtable *ht, struct rhash_head *obj,
 102                              struct rhash_head __rcu **pprev, gfp_t flags);
 103
 104 bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size);
 105 bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size);
 106
 107 int rhashtable_expand(struct rhashtable *ht, gfp_t flags);
 108 int rhashtable_shrink(struct rhashtable *ht, gfp_t flags);
 109
 110 void *rhashtable_lookup(const struct rhashtable *ht, const void *key);
 111 void *rhashtable_lookup_compare(const struct rhashtable *ht, u32 hash,
 112                                 bool (*compare)(void *, void *), void *arg);
 113
 114 void rhashtable_destroy(const struct rhashtable *ht);
 115
 116 #define rht_dereference(p, ht) \
 117         rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
 118
 119 #define rht_dereference_rcu(p, ht) \
 120         rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
 121
 122 #define rht_entry(ptr, type, member) container_of(ptr, type, member)
 123 #define rht_entry_safe(ptr, type, member) \
 124 ({ \
 125         typeof(ptr) __ptr = (ptr); \
 126            __ptr ? rht_entry(__ptr, type, member) : NULL; \
 127 })
 128
 129 #define rht_next_entry_safe(pos, ht, member) \
 130 ({ \
 131         pos ? rht_entry_safe(rht_dereference((pos)->member.next, ht), \
 132                              typeof(*(pos)), member) : NULL; \
 133 })
 134
 135 /**
 136  * rht_for_each - iterate over hash chain
 137  * @pos:        &struct rhash_head to use as a loop cursor.
 138  * @head:       head of the hash chain (struct rhash_head *)
 139  * @ht:         pointer to your struct rhashtable
 140  */
 141 #define rht_for_each(pos, head, ht) \
 142         for (pos = rht_dereference(head, ht); \
 143              pos; \
 144              pos = rht_dereference((pos)->next, ht))
 145
 146 /**
 147  * rht_for_each_entry - iterate over hash chain of given type
 148  * @pos:        type * to use as a loop cursor.
 149  * @head:       head of the hash chain (struct rhash_head *)
 150  * @ht:         pointer to your struct rhashtable
 151  * @member:     name of the rhash_head within the hashable struct.
 152  */
 153 #define rht_for_each_entry(pos, head, ht, member) \
 154         for (pos = rht_entry_safe(rht_dereference(head, ht), \
 155                                    typeof(*(pos)), member); \
 156              pos; \
 157              pos = rht_next_entry_safe(pos, ht, member))
 158
 159 /**
 160  * rht_for_each_entry_safe - safely iterate over hash chain of given type
 161  * @pos:        type * to use as a loop cursor.
 162  * @n:          type * to use for temporary next object storage
 163  * @head:       head of the hash chain (struct rhash_head *)
 164  * @ht:         pointer to your struct rhashtable
 165  * @member:     name of the rhash_head within the hashable struct.
 166  *
 167  * This hash chain list-traversal primitive allows for the looped code to
 168  * remove the loop cursor from the list.
 169  */
 170 #define rht_for_each_entry_safe(pos, n, head, ht, member)               \
 171         for (pos = rht_entry_safe(rht_dereference(head, ht), \
 172                                   typeof(*(pos)), member), \
 173              n = rht_next_entry_safe(pos, ht, member); \
 174              pos; \
 175              pos = n, \
 176              n = rht_next_entry_safe(pos, ht, member))
 177
 178 /**
 179  * rht_for_each_rcu - iterate over rcu hash chain
 180  * @pos:        &struct rhash_head to use as a loop cursor.
 181  * @head:       head of the hash chain (struct rhash_head *)
 182  * @ht:         pointer to your struct rhashtable
 183  *
 184  * This hash chain list-traversal primitive may safely run concurrently with
 185  * the _rcu fkht mutation primitives such as rht_insert() as long as the
 186  * traversal is guarded by rcu_read_lock().
 187  */
 188 #define rht_for_each_rcu(pos, head, ht) \
 189         for (pos = rht_dereference_rcu(head, ht); \
 190              pos; \
 191              pos = rht_dereference_rcu((pos)->next, ht))
 192
 193 /**
 194  * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
 195  * @pos:        type * to use as a loop cursor.
 196  * @head:       head of the hash chain (struct rhash_head *)
 197  * @member:     name of the rhash_head within the hashable struct.
 198  *
 199  * This hash chain list-traversal primitive may safely run concurrently with
 200  * the _rcu fkht mutation primitives such as rht_insert() as long as the
 201  * traversal is guarded by rcu_read_lock().
 202  */
 203 #define rht_for_each_entry_rcu(pos, head, member) \
 204         for (pos = rht_entry_safe(rcu_dereference_raw(head), \
 205                                   typeof(*(pos)), member); \
 206              pos; \
 207              pos = rht_entry_safe(rcu_dereference_raw((pos)->member.next), \
 208                                   typeof(*(pos)), member))
 209
 210 #endif /* _LINUX_RHASHTABLE_H */