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