net/batman-adv/hash.h

   1 /*
   2  * Copyright (C) 2006-2011 B.A.T.M.A.N. contributors:
   3  *
   4  * Simon Wunderlich, Marek Lindner
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of version 2 of the GNU General Public
   8  * License as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13  * General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301, USA
  19  *
  20  */
  21
  22 #ifndef _NET_BATMAN_ADV_HASH_H_
  23 #define _NET_BATMAN_ADV_HASH_H_
  24
  25 #include <linux/list.h>
  26
  27 /* callback to a compare function.  should
  28  * compare 2 element datas for their keys,
  29  * return 0 if same and not 0 if not
  30  * same */
  31 typedef int (*hashdata_compare_cb)(void *, void *);
  32
  33 /* the hashfunction, should return an index
  34  * based on the key in the data of the first
  35  * argument and the size the second */
  36 typedef int (*hashdata_choose_cb)(void *, int);
  37 typedef void (*hashdata_free_cb)(void *, void *);
  38
  39 struct element_t {
  40         void *data;             /* pointer to the data */
  41         struct hlist_node hlist;        /* bucket list pointer */
  42         struct rcu_head rcu;
  43 };
  44
  45 struct hashtable_t {
  46         struct hlist_head *table;   /* the hashtable itself with the buckets */
  47         spinlock_t *list_locks;     /* spinlock for each hash list entry */
  48         int size;                   /* size of hashtable */
  49 };
  50
  51 /* allocates and clears the hash */
  52 struct hashtable_t *hash_new(int size);
  53
  54 /* free only the hashtable and the hash itself. */
  55 void hash_destroy(struct hashtable_t *hash);
  56
  57 void bucket_free_rcu(struct rcu_head *rcu);
  58
  59 /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
  60  * called to remove the elements inside of the hash.  if you don't remove the
  61  * elements, memory might be leaked. */
  62 static inline void hash_delete(struct hashtable_t *hash,
  63                                hashdata_free_cb free_cb, void *arg)
  64 {
  65         struct hlist_head *head;
  66         struct hlist_node *walk, *safe;
  67         struct element_t *bucket;
  68         spinlock_t *list_lock; /* spinlock to protect write access */
  69         int i;
  70
  71         for (i = 0; i < hash->size; i++) {
  72                 head = &hash->table[i];
  73                 list_lock = &hash->list_locks[i];
  74
  75                 spin_lock_bh(list_lock);
  76                 hlist_for_each_entry_safe(bucket, walk, safe, head, hlist) {
  77                         if (free_cb)
  78                                 free_cb(bucket->data, arg);
  79
  80                         hlist_del_rcu(walk);
  81                         call_rcu(&bucket->rcu, bucket_free_rcu);
  82                 }
  83                 spin_unlock_bh(list_lock);
  84         }
  85
  86         hash_destroy(hash);
  87 }
  88
  89 /* adds data to the hashtable. returns 0 on success, -1 on error */
  90 static inline int hash_add(struct hashtable_t *hash,
  91                            hashdata_compare_cb compare,
  92                            hashdata_choose_cb choose, void *data)
  93 {
  94         int index;
  95         struct hlist_head *head;
  96         struct hlist_node *walk, *safe;
  97         struct element_t *bucket;
  98         spinlock_t *list_lock; /* spinlock to protect write access */
  99
 100         if (!hash)
 101                 goto err;
 102
 103         index = choose(data, hash->size);
 104         head = &hash->table[index];
 105         list_lock = &hash->list_locks[index];
 106
 107         rcu_read_lock();
 108         hlist_for_each_entry_safe(bucket, walk, safe, head, hlist) {
 109                 if (compare(bucket->data, data))
 110                         goto err_unlock;
 111         }
 112         rcu_read_unlock();
 113
 114         /* no duplicate found in list, add new element */
 115         bucket = kmalloc(sizeof(struct element_t), GFP_ATOMIC);
 116         if (!bucket)
 117                 goto err;
 118
 119         bucket->data = data;
 120
 121         spin_lock_bh(list_lock);
 122         hlist_add_head_rcu(&bucket->hlist, head);
 123         spin_unlock_bh(list_lock);
 124
 125         return 0;
 126
 127 err_unlock:
 128         rcu_read_unlock();
 129 err:
 130         return -1;
 131 }
 132
 133 /* removes data from hash, if found. returns pointer do data on success, so you
 134  * can remove the used structure yourself, or NULL on error .  data could be the
 135  * structure you use with just the key filled, we just need the key for
 136  * comparing. */
 137 static inline void *hash_remove(struct hashtable_t *hash,
 138                                 hashdata_compare_cb compare,
 139                                 hashdata_choose_cb choose, void *data)
 140 {
 141         size_t index;
 142         struct hlist_node *walk;
 143         struct element_t *bucket;
 144         struct hlist_head *head;
 145         void *data_save = NULL;
 146
 147         index = choose(data, hash->size);
 148         head = &hash->table[index];
 149
 150         spin_lock_bh(&hash->list_locks[index]);
 151         hlist_for_each_entry(bucket, walk, head, hlist) {
 152                 if (compare(bucket->data, data)) {
 153                         data_save = bucket->data;
 154                         hlist_del_rcu(walk);
 155                         call_rcu(&bucket->rcu, bucket_free_rcu);
 156                         break;
 157                 }
 158         }
 159         spin_unlock_bh(&hash->list_locks[index]);
 160
 161         return data_save;
 162 }
 163
 164 /**
 165  * finds data, based on the key in keydata. returns the found data on success,
 166  * or NULL on error
 167  *
 168  * caller must lock with rcu_read_lock() / rcu_read_unlock()
 169  **/
 170 static inline void *hash_find(struct hashtable_t *hash,
 171                               hashdata_compare_cb compare,
 172                               hashdata_choose_cb choose, void *keydata)
 173 {
 174         int index;
 175         struct hlist_head *head;
 176         struct hlist_node *walk;
 177         struct element_t *bucket;
 178         void *bucket_data = NULL;
 179
 180         if (!hash)
 181                 return NULL;
 182
 183         index = choose(keydata , hash->size);
 184         head = &hash->table[index];
 185
 186         hlist_for_each_entry(bucket, walk, head, hlist) {
 187                 if (compare(bucket->data, keydata)) {
 188                         bucket_data = bucket->data;
 189                         break;
 190                 }
 191         }
 192
 193         return bucket_data;
 194 }
 195
 196 #endif /* _NET_BATMAN_ADV_HASH_H_ */