1 /* 2 * Resizable, Scalable, Concurrent Hash Table 3 * 4 * Copyright (c) 2014 Thomas Graf <[email protected]> 5 * Copyright (c) 2008-2014 Patrick McHardy <[email protected]> 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 */ 209