net/batman-adv/hash.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /* Copyright (C) 2006-2019  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/rculist.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/stddef.h>
  18 #include <linux/types.h>
  19
  20 struct lock_class_key;
  21
  22 /* callback to a compare function.  should compare 2 element datas for their
  23  * keys
  24  *
  25  * Return: true if same and false if not same
  26  */
  27 typedef bool (*batadv_hashdata_compare_cb)(const struct hlist_node *,
  28                                            const void *);
  29
  30 /* the hashfunction
  31  *
  32  * Return: an index based on the key in the data of the first argument and the
  33  * size the second
  34  */
  35 typedef u32 (*batadv_hashdata_choose_cb)(const void *, u32);
  36 typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);
  37
  38 /**
  39  * struct batadv_hashtable - Wrapper of simple hlist based hashtable
  40  */
  41 struct batadv_hashtable {
  42         /** @table: the hashtable itself with the buckets */
  43         struct hlist_head *table;
  44
  45         /** @list_locks: spinlock for each hash list entry */
  46         spinlock_t *list_locks;
  47
  48         /** @size: size of hashtable */
  49         u32 size;
  50
  51         /** @generation: current (generation) sequence number */
  52         atomic_t generation;
  53 };
  54
  55 /* allocates and clears the hash */
  56 struct batadv_hashtable *batadv_hash_new(u32 size);
  57
  58 /* set class key for all locks */
  59 void batadv_hash_set_lock_class(struct batadv_hashtable *hash,
  60                                 struct lock_class_key *key);
  61
  62 /* free only the hashtable and the hash itself. */
  63 void batadv_hash_destroy(struct batadv_hashtable *hash);
  64
  65 /**
  66  *      batadv_hash_add() - adds data to the hashtable
  67  *      @hash: storage hash table
  68  *      @compare: callback to determine if 2 hash elements are identical
  69  *      @choose: callback calculating the hash index
  70  *      @data: data passed to the aforementioned callbacks as argument
  71  *      @data_node: to be added element
  72  *
  73  *      Return: 0 on success, 1 if the element already is in the hash
  74  *      and -1 on error.
  75  */
  76 static inline int batadv_hash_add(struct batadv_hashtable *hash,
  77                                   batadv_hashdata_compare_cb compare,
  78                                   batadv_hashdata_choose_cb choose,
  79                                   const void *data,
  80                                   struct hlist_node *data_node)
  81 {
  82         u32 index;
  83         int ret = -1;
  84         struct hlist_head *head;
  85         struct hlist_node *node;
  86         spinlock_t *list_lock; /* spinlock to protect write access */
  87
  88         if (!hash)
  89                 goto out;
  90
  91         index = choose(data, hash->size);
  92         head = &hash->table[index];
  93         list_lock = &hash->list_locks[index];
  94
  95         spin_lock_bh(list_lock);
  96
  97         hlist_for_each(node, head) {
  98                 if (!compare(node, data))
  99                         continue;
 100
 101                 ret = 1;
 102                 goto unlock;
 103         }
 104
 105         /* no duplicate found in list, add new element */
 106         hlist_add_head_rcu(data_node, head);
 107         atomic_inc(&hash->generation);
 108
 109         ret = 0;
 110
 111 unlock:
 112         spin_unlock_bh(list_lock);
 113 out:
 114         return ret;
 115 }
 116
 117 /**
 118  * batadv_hash_remove() - Removes data from hash, if found
 119  * @hash: hash table
 120  * @compare: callback to determine if 2 hash elements are identical
 121  * @choose: callback calculating the hash index
 122  * @data: data passed to the aforementioned callbacks as argument
 123  *
 124  * ata could be the structure you use with  just the key filled, we just need
 125  * the key for comparing.
 126  *
 127  * Return: returns pointer do data on success, so you can remove the used
 128  * structure yourself, or NULL on error
 129  */
 130 static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
 131                                        batadv_hashdata_compare_cb compare,
 132                                        batadv_hashdata_choose_cb choose,
 133                                        void *data)
 134 {
 135         u32 index;
 136         struct hlist_node *node;
 137         struct hlist_head *head;
 138         void *data_save = NULL;
 139
 140         index = choose(data, hash->size);
 141         head = &hash->table[index];
 142
 143         spin_lock_bh(&hash->list_locks[index]);
 144         hlist_for_each(node, head) {
 145                 if (!compare(node, data))
 146                         continue;
 147
 148                 data_save = node;
 149                 hlist_del_rcu(node);
 150                 atomic_inc(&hash->generation);
 151                 break;
 152         }
 153         spin_unlock_bh(&hash->list_locks[index]);
 154
 155         return data_save;
 156 }
 157
 158 #endif /* _NET_BATMAN_ADV_HASH_H_ */