batman-adv: protect each hash row with rcu locks

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

net/batman-adv/hash.c

@@ -27,13 +27,16 @@ static void hash_init(struct hashtable_t *hash)
 {
 	int i;
 
-	for (i = 0 ; i < hash->size; i++)
+	for (i = 0 ; i < hash->size; i++) {
 		INIT_HLIST_HEAD(&hash->table[i]);
+		spin_lock_init(&hash->list_locks[i]);
+	}
 }
 
 /* free only the hashtable and the hash itself. */
 void hash_destroy(struct hashtable_t *hash)
 {
+	kfree(hash->list_locks);
 	kfree(hash->table);
 	kfree(hash);
 }
@@ -43,20 +46,33 @@ struct hashtable_t *hash_new(int size)
 {
 	struct hashtable_t *hash;
 
-	hash = kmalloc(sizeof(struct hashtable_t) , GFP_ATOMIC);
-
+	hash = kmalloc(sizeof(struct hashtable_t), GFP_ATOMIC);
 	if (!hash)
 		return NULL;
 
-	hash->size = size;
 	hash->table = kmalloc(sizeof(struct element_t *) * size, GFP_ATOMIC);
+	if (!hash->table)
+		goto free_hash;
 
-	if (!hash->table) {
-		kfree(hash);
-		return NULL;
-	}
+	hash->list_locks = kmalloc(sizeof(spinlock_t) * size, GFP_ATOMIC);
+	if (!hash->list_locks)
+		goto free_table;
 
+	hash->size = size;
 	hash_init(hash);
-
 	return hash;
+
+free_table:
+	kfree(hash->table);
+free_hash:
+	kfree(hash);
+	return NULL;
+}
+
+void bucket_free_rcu(struct rcu_head *rcu)
+{
+	struct element_t *bucket;
+
+	bucket = container_of(rcu, struct element_t, rcu);
+	kfree(bucket);
 }

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)
@@ -152,20 +175,22 @@ 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;
 
 	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_ */

net/batman-adv/icmp_socket.c

@@ -220,9 +220,11 @@ static ssize_t bat_socket_write(struct file *file, const char __user *buff,
 		goto dst_unreach;
 
 	spin_lock_bh(&bat_priv->orig_hash_lock);
+	rcu_read_lock();
 	orig_node = ((struct orig_node *)hash_find(bat_priv->orig_hash,
 						   compare_orig, choose_orig,
 						   icmp_packet->dst));
+	rcu_read_unlock();
 
 	if (!orig_node)
 		goto unlock;

net/batman-adv/originator.c

@@ -150,9 +150,11 @@ struct orig_node *get_orig_node(struct bat_priv *bat_priv, uint8_t *addr)
 	int size;
 	int hash_added;
 
+	rcu_read_lock();
 	orig_node = ((struct orig_node *)hash_find(bat_priv->orig_hash,
 						   compare_orig, choose_orig,
 						   addr));
+	rcu_read_unlock();
 
 	if (orig_node)
 		return orig_node;
@@ -294,6 +296,7 @@ static void _purge_orig(struct bat_priv *bat_priv)
 	struct hlist_node *walk, *safe;
 	struct hlist_head *head;
 	struct element_t *bucket;
+	spinlock_t *list_lock; /* spinlock to protect write access */
 	struct orig_node *orig_node;
 	int i;
 
@@ -305,22 +308,26 @@ static void _purge_orig(struct bat_priv *bat_priv)
 	/* for all origins... */
 	for (i = 0; i < hash->size; i++) {
 		head = &hash->table[i];
+		list_lock = &hash->list_locks[i];
 
+		spin_lock_bh(list_lock);
 		hlist_for_each_entry_safe(bucket, walk, safe, head, hlist) {
 			orig_node = bucket->data;
 
 			if (purge_orig_node(bat_priv, orig_node)) {
 				if (orig_node->gw_flags)
 					gw_node_delete(bat_priv, orig_node);
-				hlist_del(walk);
-				kfree(bucket);
+				hlist_del_rcu(walk);
+				call_rcu(&bucket->rcu, bucket_free_rcu);
 				free_orig_node(orig_node, bat_priv);
+				continue;
 			}
 
 			if (time_after(jiffies, orig_node->last_frag_packet +
 						msecs_to_jiffies(FRAG_TIMEOUT)))
 				frag_list_free(&orig_node->frag_list);
 		}
+		spin_unlock_bh(list_lock);
 	}
 
 	spin_unlock_bh(&bat_priv->orig_hash_lock);
@@ -387,7 +394,8 @@ int orig_seq_print_text(struct seq_file *seq, void *offset)
 	for (i = 0; i < hash->size; i++) {
 		head = &hash->table[i];
 
-		hlist_for_each_entry(bucket, walk, head, hlist) {
+		rcu_read_lock();
+		hlist_for_each_entry_rcu(bucket, walk, head, hlist) {
 			orig_node = bucket->data;
 
 			if (!orig_node->router)
@@ -408,17 +416,16 @@ int orig_seq_print_text(struct seq_file *seq, void *offset)
 				   neigh_node->addr,
 				   neigh_node->if_incoming->net_dev->name);
 
-			rcu_read_lock();
 			hlist_for_each_entry_rcu(neigh_node, node,
 						 &orig_node->neigh_list, list) {
 				seq_printf(seq, " %pM (%3i)", neigh_node->addr,
 						neigh_node->tq_avg);
 			}
-			rcu_read_unlock();
 
 			seq_printf(seq, "\n");
 			batman_count++;
 		}
+		rcu_read_unlock();
 	}
 
 	spin_unlock_bh(&bat_priv->orig_hash_lock);
@@ -476,18 +483,21 @@ int orig_hash_add_if(struct batman_if *batman_if, int max_if_num)
 	for (i = 0; i < hash->size; i++) {
 		head = &hash->table[i];
 
-		hlist_for_each_entry(bucket, walk, head, hlist) {
+		rcu_read_lock();
+		hlist_for_each_entry_rcu(bucket, walk, head, hlist) {
 			orig_node = bucket->data;
 
 			if (orig_node_add_if(orig_node, max_if_num) == -1)
 				goto err;
 		}
+		rcu_read_unlock();
 	}
 
 	spin_unlock_bh(&bat_priv->orig_hash_lock);
 	return 0;
 
 err:
+	rcu_read_unlock();
 	spin_unlock_bh(&bat_priv->orig_hash_lock);
 	return -ENOMEM;
 }
@@ -562,7 +572,8 @@ int orig_hash_del_if(struct batman_if *batman_if, int max_if_num)
 	for (i = 0; i < hash->size; i++) {
 		head = &hash->table[i];
 
-		hlist_for_each_entry(bucket, walk, head, hlist) {
+		rcu_read_lock();
+		hlist_for_each_entry_rcu(bucket, walk, head, hlist) {
 			orig_node = bucket->data;
 
 			ret = orig_node_del_if(orig_node, max_if_num,
@@ -571,6 +582,7 @@ int orig_hash_del_if(struct batman_if *batman_if, int max_if_num)
 			if (ret == -1)
 				goto err;
 		}
+		rcu_read_unlock();
 	}
 
 	/* renumber remaining batman interfaces _inside_ of orig_hash_lock */
@@ -595,6 +607,7 @@ int orig_hash_del_if(struct batman_if *batman_if, int max_if_num)
 	return 0;
 
 err:
+	rcu_read_unlock();
 	spin_unlock_bh(&bat_priv->orig_hash_lock);
 	return -ENOMEM;
 }