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/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 datas 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  */
  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  */
 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_ */