batman-adv: protect each hash row with rcu locks

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>

1 files changed, 49 insertions, 24 deletions

diff --git a/net/batman-adv/hash.h b/net/batman-adv/hash.h
index eae24402fd0a..3c48c6bb1acd 100644
--- a/net/batman-adv/hash.h
+++ b/net/batman-adv/hash.h
@@ -39,10 +39,12 @@ typedef void (*hashdata_free_cb)(void *, void *);
 struct element_t {
         void *data;             /* pointer to the data */
         struct hlist_node hlist;        /* bucket list pointer */
+        struct rcu_head rcu;
 };
 
 struct hashtable_t {
-        struct hlist_head *table;   /* the hashtable itself, with the buckets */
+        struct hlist_head *table;   /* the hashtable itself with the buckets */
+        spinlock_t *list_locks;     /* spinlock for each hash list entry */
         int size;                   /* size of hashtable */
 };
 
@@ -52,6 +54,8 @@ struct hashtable_t *hash_new(int size);
 /* free only the hashtable and the hash itself. */
 void hash_destroy(struct hashtable_t *hash);
 
+void bucket_free_rcu(struct rcu_head *rcu);
+
 /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
  * called to remove the elements inside of the hash.  if you don't remove the
  * elements, memory might be leaked. */
@@ -61,19 +65,22 @@ static inline void hash_delete(struct hashtable_t *hash,
         struct hlist_head *head;
         struct hlist_node *walk, *safe;
         struct element_t *bucket;
+        spinlock_t *list_lock; /* spinlock to protect write access */
         int i;
 
         for (i = 0; i < hash->size; i++) {
                 head = &hash->table[i];
+                list_lock = &hash->list_locks[i];
 
-                hlist_for_each_safe(walk, safe, head) {
-                        bucket = hlist_entry(walk, struct element_t, hlist);
+                spin_lock_bh(list_lock);
+                hlist_for_each_entry_safe(bucket, walk, safe, head, hlist) {
                         if (free_cb)
                                 free_cb(bucket->data, arg);
 
-                        hlist_del(walk);
-                        kfree(bucket);
+                        hlist_del_rcu(walk);
+                        call_rcu(&bucket->rcu, bucket_free_rcu);
                 }
+                spin_unlock_bh(list_lock);
         }
 
         hash_destroy(hash);
@@ -88,29 +95,39 @@ static inline int hash_add(struct hashtable_t *hash,
         struct hlist_head *head;
         struct hlist_node *walk, *safe;
         struct element_t *bucket;
+        spinlock_t *list_lock; /* spinlock to protect write access */
 
         if (!hash)
-                return -1;
+                goto err;
 
         index = choose(data, hash->size);
         head = &hash->table[index];
+        list_lock = &hash->list_locks[index];
 
-        hlist_for_each_safe(walk, safe, head) {
-                bucket = hlist_entry(walk, struct element_t, hlist);
+        rcu_read_lock();
+        hlist_for_each_entry_safe(bucket, walk, safe, head, hlist) {
                 if (compare(bucket->data, data))
-                        return -1;
+                        goto err_unlock;
         }
+        rcu_read_unlock();
 
         /* no duplicate found in list, add new element */
         bucket = kmalloc(sizeof(struct element_t), GFP_ATOMIC);
-
         if (!bucket)
-                return -1;
+                goto err;
 
         bucket->data = data;
-        hlist_add_head(&bucket->hlist, head);
+
+        spin_lock_bh(list_lock);
+        hlist_add_head_rcu(&bucket->hlist, head);
+        spin_unlock_bh(list_lock);
 
         return 0;
+
+err_unlock:
+        rcu_read_unlock();
+err:
+        return -1;
 }
 
 /* removes data from hash, if found. returns pointer do data on success, so you
@@ -125,25 +142,31 @@ static inline void *hash_remove(struct hashtable_t *hash,
         struct hlist_node *walk;
         struct element_t *bucket;
         struct hlist_head *head;
-        void *data_save;
+        void *data_save = NULL;
 
         index = choose(data, hash->size);
         head = &hash->table[index];
 
+        spin_lock_bh(&hash->list_locks[index]);
         hlist_for_each_entry(bucket, walk, head, hlist) {
                 if (compare(bucket->data, data)) {
                         data_save = bucket->data;
-                        hlist_del(walk);
-                        kfree(bucket);
-                        return data_save;
+                        hlist_del_rcu(walk);
+                        call_rcu(&bucket->rcu, bucket_free_rcu);
+                        break;
                 }
         }
+        spin_unlock_bh(&hash->list_locks[index]);
 
-        return NULL;
+        return data_save;
 }
 
-/* finds data, based on the key in keydata. returns the found data on success,
- * or NULL on error */
+/**
+ * finds data, based on the key in keydata. returns the found data on success,
+ * or NULL on error
+ *
+ * caller must lock with rcu_read_lock() / rcu_read_unlock()
+ **/
 static inline void *hash_find(struct hashtable_t *hash,
                               hashdata_compare_cb compare,
                               hashdata_choose_cb choose, void *keydata)
@@ -152,6 +175,7 @@ static inline void *hash_find(struct hashtable_t *hash,
         struct hlist_head *head;
         struct hlist_node *walk;
         struct element_t *bucket;
+        void *bucket_data = NULL;
 
         if (!hash)
                 return NULL;
@@ -159,13 +183,14 @@ static inline void *hash_find(struct hashtable_t *hash,
         index = choose(keydata , hash->size);
         head = &hash->table[index];
 
-        hlist_for_each(walk, head) {
-                bucket = hlist_entry(walk, struct element_t, hlist);
-                if (compare(bucket->data, keydata))
-                        return bucket->data;
+        hlist_for_each_entry(bucket, walk, head, hlist) {
+                if (compare(bucket->data, keydata)) {
+                        bucket_data = bucket->data;
+                        break;
+                }
         }
 
-        return NULL;
+        return bucket_data;
 }
 
 #endif /* _NET_BATMAN_ADV_HASH_H_ */