2 * Resizable, Scalable, Concurrent Hash Table
4 * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
5 * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
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
11 * Code partially derived from nft_hash
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.
18 #ifndef _LINUX_RHASHTABLE_H
19 #define _LINUX_RHASHTABLE_H
21 #include <linux/rculist.h>
24 struct rhash_head __rcu *next;
27 #define INIT_HASH_HEAD(ptr) ((ptr)->next = NULL)
31 struct rhash_head __rcu *buckets[];
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);
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
54 struct rhashtable_params {
63 rht_obj_hashfn_t obj_hashfn;
64 bool (*grow_decision)(const struct rhashtable *ht,
66 bool (*shrink_decision)(const struct rhashtable *ht,
68 int (*mutex_is_held)(void);
72 * struct rhashtable - Hash table handle
74 * @nelems: Number of elements in table
75 * @shift: Current size (1 << shift)
76 * @p: Configuration parameters
79 struct bucket_table __rcu *tbl;
82 struct rhashtable_params p;
85 #ifdef CONFIG_PROVE_LOCKING
86 int lockdep_rht_mutex_is_held(const struct rhashtable *ht);
88 static inline int lockdep_rht_mutex_is_held(const struct rhashtable *ht)
92 #endif /* CONFIG_PROVE_LOCKING */
94 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
96 u32 rhashtable_hashfn(const struct rhashtable *ht, const void *key, u32 len);
97 u32 rhashtable_obj_hashfn(const struct rhashtable *ht, void *ptr);
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);
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);
107 int rhashtable_expand(struct rhashtable *ht, gfp_t flags);
108 int rhashtable_shrink(struct rhashtable *ht, gfp_t flags);
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);
114 void rhashtable_destroy(const struct rhashtable *ht);
116 #define rht_dereference(p, ht) \
117 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
119 #define rht_dereference_rcu(p, ht) \
120 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
122 #define rht_entry(ptr, type, member) container_of(ptr, type, member)
123 #define rht_entry_safe(ptr, type, member) \
125 typeof(ptr) __ptr = (ptr); \
126 __ptr ? rht_entry(__ptr, type, member) : NULL; \
129 #define rht_next_entry_safe(pos, ht, member) \
131 pos ? rht_entry_safe(rht_dereference((pos)->member.next, ht), \
132 typeof(*(pos)), member) : NULL; \
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
141 #define rht_for_each(pos, head, ht) \
142 for (pos = rht_dereference(head, ht); \
144 pos = rht_dereference((pos)->next, ht))
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.
153 #define rht_for_each_entry(pos, head, ht, member) \
154 for (pos = rht_entry_safe(rht_dereference(head, ht), \
155 typeof(*(pos)), member); \
157 pos = rht_next_entry_safe(pos, ht, member))
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.
167 * This hash chain list-traversal primitive allows for the looped code to
168 * remove the loop cursor from the list.
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); \
176 n = rht_next_entry_safe(pos, ht, member))
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
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().
188 #define rht_for_each_rcu(pos, head, ht) \
189 for (pos = rht_dereference_rcu(head, ht); \
191 pos = rht_dereference_rcu((pos)->next, ht))
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.
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().
203 #define rht_for_each_entry_rcu(pos, head, member) \
204 for (pos = rht_entry_safe(rcu_dereference_raw(head), \
205 typeof(*(pos)), member); \
207 pos = rht_entry_safe(rcu_dereference_raw((pos)->member.next), \
208 typeof(*(pos)), member))
210 #endif /* _LINUX_RHASHTABLE_H */