net/batman-adv/hash.h

   1 /* Copyright (C) 2006-2017  B.A.T.M.A.N. contributors:
   2  *
   3  * Simon Wunderlich, Marek Lindner
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 2 of the GNU General Public
   7  * License as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #ifndef _NET_BATMAN_ADV_HASH_H_
  19 #define _NET_BATMAN_ADV_HASH_H_
  20
  21 #include "main.h"
  22
  23 #include <linux/compiler.h>
  24 #include <linux/list.h>
  25 #include <linux/rculist.h>
  26 #include <linux/spinlock.h>
  27 #include <linux/stddef.h>
  28 #include <linux/types.h>
  29
  30 struct lock_class_key;
  31
  32 /* callback to a compare function.  should compare 2 element datas for their
  33  * keys
  34  *
  35  * Return: true if same and false if not same
  36  */
  37 typedef bool (*batadv_hashdata_compare_cb)(const struct hlist_node *,
  38                                            const void *);
  39
  40 /* the hashfunction
  41  *
  42  * Return: an index based on the key in the data of the first argument and the
  43  * size the second
  44  */
  45 typedef u32 (*batadv_hashdata_choose_cb)(const void *, u32);
  46 typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);
  47
  48 struct batadv_hashtable {
  49         struct hlist_head *table;   /* the hashtable itself with the buckets */
  50         spinlock_t *list_locks;     /* spinlock for each hash list entry */
  51         u32 size;                   /* size of hashtable */
  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  */
  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
 107         ret = 0;
 108
 109 unlock:
 110         spin_unlock_bh(list_lock);
 111 out:
 112         return ret;
 113 }
 114
 115 /* removes data from hash, if found. data could be the structure you use with
 116  * just the key filled, we just need the key for comparing.
 117  *
 118  * Return: returns pointer do data on success, so you can remove the used
 119  * structure yourself, or NULL on error
 120  */
 121 static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
 122                                        batadv_hashdata_compare_cb compare,
 123                                        batadv_hashdata_choose_cb choose,
 124                                        void *data)
 125 {
 126         u32 index;
 127         struct hlist_node *node;
 128         struct hlist_head *head;
 129         void *data_save = NULL;
 130
 131         index = choose(data, hash->size);
 132         head = &hash->table[index];
 133
 134         spin_lock_bh(&hash->list_locks[index]);
 135         hlist_for_each(node, head) {
 136                 if (!compare(node, data))
 137                         continue;
 138
 139                 data_save = node;
 140                 hlist_del_rcu(node);
 141                 break;
 142         }
 143         spin_unlock_bh(&hash->list_locks[index]);
 144
 145         return data_save;
 146 }
 147
 148 #endif /* _NET_BATMAN_ADV_HASH_H_ */