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 */ 211