hash.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2/* Copyright (C) B.A.T.M.A.N. contributors:
  3 *
  4 * Simon Wunderlich, Marek Lindner
  5 */
  6
  7#ifndef _NET_BATMAN_ADV_HASH_H_
  8#define _NET_BATMAN_ADV_HASH_H_
  9
 10#include "main.h"
 11
 12#include <linux/atomic.h>
 13#include <linux/compiler.h>
 14#include <linux/list.h>
 15#include <linux/lockdep.h>
 16#include <linux/rculist.h>
 17#include <linux/spinlock.h>
 18#include <linux/stddef.h>
 19#include <linux/types.h>
 20
 21/* callback to a compare function.  should compare 2 element data for their
 22 * keys
 23 *
 24 * Return: true if same and false if not same
 25 */
 26typedef bool (*batadv_hashdata_compare_cb)(const struct hlist_node *,
 27					   const void *);
 28
 29/* the hashfunction
 30 *
 31 * Return: an index based on the key in the data of the first argument and the
 32 * size the second
 33 */
 34typedef u32 (*batadv_hashdata_choose_cb)(const void *, u32);
 35typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);
 36
 37/**
 38 * struct batadv_hashtable - Wrapper of simple hlist based hashtable
 39 */
 40struct batadv_hashtable {
 41	/** @table: the hashtable itself with the buckets */
 42	struct hlist_head *table;
 43
 44	/** @list_locks: spinlock for each hash list entry */
 45	spinlock_t *list_locks;
 46
 47	/** @size: size of hashtable */
 48	u32 size;
 49
 50	/** @generation: current (generation) sequence number */
 51	atomic_t generation;
 52};
 53
 54/* allocates and clears the hash */
 55struct batadv_hashtable *batadv_hash_new(u32 size);
 56
 57/* set class key for all locks */
 58void batadv_hash_set_lock_class(struct batadv_hashtable *hash,
 59				struct lock_class_key *key);
 60
 61/* free only the hashtable and the hash itself. */
 62void batadv_hash_destroy(struct batadv_hashtable *hash);
 63
 64/**
 65 *	batadv_hash_add() - adds data to the hashtable
 66 *	@hash: storage hash table
 67 *	@compare: callback to determine if 2 hash elements are identical
 68 *	@choose: callback calculating the hash index
 69 *	@data: data passed to the aforementioned callbacks as argument
 70 *	@data_node: to be added element
 71 *
 72 *	Return: 0 on success, 1 if the element already is in the hash
 73 *	and -1 on error.
 74 */
 75static inline int batadv_hash_add(struct batadv_hashtable *hash,
 76				  batadv_hashdata_compare_cb compare,
 77				  batadv_hashdata_choose_cb choose,
 78				  const void *data,
 79				  struct hlist_node *data_node)
 80{
 81	u32 index;
 82	int ret = -1;
 83	struct hlist_head *head;
 84	struct hlist_node *node;
 85	spinlock_t *list_lock; /* spinlock to protect write access */
 86
 87	if (!hash)
 88		goto out;
 89
 90	index = choose(data, hash->size);
 91	head = &hash->table[index];
 92	list_lock = &hash->list_locks[index];
 93
 94	spin_lock_bh(list_lock);
 95
 96	hlist_for_each(node, head) {
 97		if (!compare(node, data))
 98			continue;
 99
100		ret = 1;
101		goto unlock;
102	}
103
104	/* no duplicate found in list, add new element */
105	hlist_add_head_rcu(data_node, head);
106	atomic_inc(&hash->generation);
107
108	ret = 0;
109
110unlock:
111	spin_unlock_bh(list_lock);
112out:
113	return ret;
114}
115
116/**
117 * batadv_hash_remove() - Removes data from hash, if found
118 * @hash: hash table
119 * @compare: callback to determine if 2 hash elements are identical
120 * @choose: callback calculating the hash index
121 * @data: data passed to the aforementioned callbacks as argument
122 *
123 * ata could be the structure you use with  just the key filled, we just need
124 * the key for comparing.
125 *
126 * Return: returns pointer do data on success, so you can remove the used
127 * structure yourself, or NULL on error
128 */
129static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
130				       batadv_hashdata_compare_cb compare,
131				       batadv_hashdata_choose_cb choose,
132				       void *data)
133{
134	u32 index;
135	struct hlist_node *node;
136	struct hlist_head *head;
137	void *data_save = NULL;
138
139	index = choose(data, hash->size);
140	head = &hash->table[index];
141
142	spin_lock_bh(&hash->list_locks[index]);
143	hlist_for_each(node, head) {
144		if (!compare(node, data))
145			continue;
146
147		data_save = node;
148		hlist_del_rcu(node);
149		atomic_inc(&hash->generation);
150		break;
151	}
152	spin_unlock_bh(&hash->list_locks[index]);
153
154	return data_save;
155}
156
157#endif /* _NET_BATMAN_ADV_HASH_H_ */