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  */
26 typedef 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  */
34 typedef u32 (*batadv_hashdata_choose_cb)(const void *, u32);
35 typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);
36 
37 /**
38  * struct batadv_hashtable - Wrapper of simple hlist based hashtable
39  */
40 struct 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 */
55 struct batadv_hashtable *batadv_hash_new(u32 size);
56 
57 /* set class key for all locks */
58 void 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. */
62 void 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  */
batadv_hash_add(struct batadv_hashtable * hash,batadv_hashdata_compare_cb compare,batadv_hashdata_choose_cb choose,const void * data,struct hlist_node * data_node)75 static 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 
110 unlock:
111 	spin_unlock_bh(list_lock);
112 out:
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  */
batadv_hash_remove(struct batadv_hashtable * hash,batadv_hashdata_compare_cb compare,batadv_hashdata_choose_cb choose,void * data)129 static 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_ */
158