[B.A.T.M.A.N.] [PATCH 3/4] batman-adv: Correct rcu refcounting for batman_if

Sven Eckelmann
2011-01-30T01:52:58Z

<TODO: write a long monologue about every problem we have or could have or
maybe never had and would have when we not have it>

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
batman-adv/bat_sysfs.c | 12 ++++++------
batman-adv/hard-interface.c | 40 +++++++++++++++++++---------------------
batman-adv/hard-interface.h | 9 ++++-----
batman-adv/types.h | 2 +-
4 files changed, 30 insertions(+), 33 deletions(-)

diff --git a/batman-adv/bat_sysfs.c b/batman-adv/bat_sysfs.c
index f7b93a0..08f9251 100644
--- a/batman-adv/bat_sysfs.c
+++ b/batman-adv/bat_sysfs.c
@@ -450,7 +450,7 @@ static ssize_t show_mesh_iface(struct kobject *kobj, struct attribute *attr,
length = sprintf(buff, "%s\n", batman_if->if_status == IF_NOT_IN_USE ?
"none" : batman_if->soft_iface->name);

- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);

return length;
}
@@ -472,7 +472,7 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr,
if (strlen(buff) >= IFNAMSIZ) {
pr_err("Invalid parameter for 'mesh_iface' setting received: "
"interface name too long '%s'\n", buff);
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
return -EINVAL;
}

@@ -483,7 +483,7 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr,

if ((batman_if->if_status == status_tmp) || ((batman_if->soft_iface) &&
(strncmp(batman_if->soft_iface->name, buff, IFNAMSIZ) == 0))) {
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
return count;
}

@@ -491,7 +491,7 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr,
rtnl_lock();
hardif_disable_interface(batman_if);
rtnl_unlock();
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
return count;
}

@@ -503,7 +503,7 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr,
}

ret = hardif_enable_interface(batman_if, buff);
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);

return ret;
}
@@ -537,7 +537,7 @@ static ssize_t show_iface_status(struct kobject *kobj, struct attribute *attr,
break;
}

- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);

return length;
}
diff --git a/batman-adv/hard-interface.c b/batman-adv/hard-interface.c
index e2b001a..3f59c52 100644
--- a/batman-adv/hard-interface.c
+++ b/batman-adv/hard-interface.c
@@ -40,13 +40,13 @@ static int batman_skb_recv(struct sk_buff *skb,
struct packet_type *ptype,
struct net_device *orig_dev);

-static void hardif_free_rcu(struct rcu_head *rcu)
+void hardif_free_rcu(struct rcu_head *rcu)
{
struct batman_if *batman_if;

batman_if = container_of(rcu, struct batman_if, rcu);
dev_put(batman_if->net_dev);
- kref_put(&batman_if->refcount, hardif_free_ref);
+ kfree(batman_if);
}

struct batman_if *get_batman_if_by_netdev(struct net_device *net_dev)
@@ -55,16 +55,14 @@ struct batman_if *get_batman_if_by_netdev(struct net_device *net_dev)

rcu_read_lock();
list_for_each_entry_rcu(batman_if, &if_list, list) {
- if (batman_if->net_dev == net_dev)
+ if (batman_if->net_dev == net_dev &&
+ atomic_inc_not_zero(&batman_if->refcount))
goto out;
}

batman_if = NULL;

out:
- if (batman_if)
- kref_get(&batman_if->refcount);
-
rcu_read_unlock();
return batman_if;
}
@@ -105,16 +103,14 @@ static struct batman_if *get_active_batman_if(struct net_device *soft_iface)
if (batman_if->soft_iface != soft_iface)
continue;

- if (batman_if->if_status == IF_ACTIVE)
+ if (batman_if->if_status == IF_ACTIVE &&
+ atomic_inc_not_zero(&batman_if->refcount))
goto out;
}

batman_if = NULL;

out:
- if (batman_if)
- kref_get(&batman_if->refcount);
-
rcu_read_unlock();
return batman_if;
}
@@ -137,14 +133,14 @@ static void set_primary_if(struct bat_priv *bat_priv,
struct batman_packet *batman_packet;
struct batman_if *old_if;

- if (batman_if)
- kref_get(&batman_if->refcount);
+ if (batman_if && !atomic_inc_not_zero(&batman_if->refcount))
+ batman_if = NULL;

old_if = bat_priv->primary_if;
bat_priv->primary_if = batman_if;

if (old_if)
- kref_put(&old_if->refcount, hardif_free_ref);
+ hardif_free_ref(old_if);

if (!bat_priv->primary_if)
return;
@@ -290,6 +286,9 @@ int hardif_enable_interface(struct batman_if *batman_if, char *iface_name)
if (batman_if->if_status != IF_NOT_IN_USE)
goto out;

+ if (!atomic_inc_not_zero(&batman_if->refcount))
+ goto out;
+
batman_if->soft_iface = dev_get_by_name(&init_net, iface_name);

if (!batman_if->soft_iface) {
@@ -328,7 +327,6 @@ int hardif_enable_interface(struct batman_if *batman_if, char *iface_name)
batman_if->batman_adv_ptype.type = __constant_htons(ETH_P_BATMAN);
batman_if->batman_adv_ptype.func = batman_skb_recv;
batman_if->batman_adv_ptype.dev = batman_if->net_dev;
- kref_get(&batman_if->refcount);
dev_add_pack(&batman_if->batman_adv_ptype);

atomic_set(&batman_if->seqno, 1);
@@ -371,6 +369,7 @@ out:
return 0;

err:
+ hardif_free_ref(batman_if);
return -ENOMEM;
}

@@ -387,7 +386,7 @@ void hardif_disable_interface(struct batman_if *batman_if)
bat_info(batman_if->soft_iface, "Removing interface: %s\n",
batman_if->net_dev->name);
dev_remove_pack(&batman_if->batman_adv_ptype);
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);

bat_priv->num_ifaces--;
orig_hash_del_if(batman_if, bat_priv->num_ifaces);
@@ -399,7 +398,7 @@ void hardif_disable_interface(struct batman_if *batman_if)
set_primary_if(bat_priv, new_if);

if (new_if)
- kref_put(&new_if->refcount, hardif_free_ref);
+ hardif_free_ref(new_if);
}

kfree(batman_if->packet_buff);
@@ -445,7 +444,8 @@ static struct batman_if *hardif_add_interface(struct net_device *net_dev)
batman_if->soft_iface = NULL;
batman_if->if_status = IF_NOT_IN_USE;
INIT_LIST_HEAD(&batman_if->list);
- kref_init(&batman_if->refcount);
+ /* extra reference for return */
+ atomic_set(&batman_if->refcount, 2);

check_known_mac_addr(batman_if->net_dev);

@@ -453,8 +453,6 @@ static struct batman_if *hardif_add_interface(struct net_device *net_dev)
list_add_tail_rcu(&batman_if->list, &if_list);
spin_unlock(&if_list_lock);

- /* extra reference for return */
- kref_get(&batman_if->refcount);
return batman_if;

free_if:
@@ -476,7 +474,7 @@ static void hardif_remove_interface(struct batman_if *batman_if)

batman_if->if_status = IF_TO_BE_REMOVED;
sysfs_del_hardif(&batman_if->hardif_obj);
- call_rcu(&batman_if->rcu, hardif_free_rcu);
+ hardif_free_ref(batman_if);
}

void hardif_remove_interfaces(void)
@@ -548,7 +546,7 @@ static int hard_if_event(struct notifier_block *this,
};

hardif_put:
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
out:
return NOTIFY_DONE;
}
diff --git a/batman-adv/hard-interface.h b/batman-adv/hard-interface.h
index ad19543..e488b90 100644
--- a/batman-adv/hard-interface.h
+++ b/batman-adv/hard-interface.h
@@ -37,13 +37,12 @@ void hardif_disable_interface(struct batman_if *batman_if);
void hardif_remove_interfaces(void);
int hardif_min_mtu(struct net_device *soft_iface);
void update_min_mtu(struct net_device *soft_iface);
+void hardif_free_rcu(struct rcu_head *rcu);

-static inline void hardif_free_ref(struct kref *refcount)
+static inline void hardif_free_ref(struct batman_if *batman_if)
{
- struct batman_if *batman_if;
-
- batman_if = container_of(refcount, struct batman_if, refcount);
- kfree(batman_if);
+ if (atomic_dec_and_test(&batman_if->refcount))
+ call_rcu(&batman_if->rcu, hardif_free_rcu);
}

#endif /* _NET_BATMAN_ADV_HARD_INTERFACE_H_ */
diff --git a/batman-adv/types.h b/batman-adv/types.h
index 8df6d9d..317ede8 100644
--- a/batman-adv/types.h
+++ b/batman-adv/types.h
@@ -43,7 +43,7 @@ struct batman_if {
unsigned char *packet_buff;
int packet_len;
struct kobject *hardif_obj;
- struct kref refcount;
+ atomic_t refcount;
struct packet_type batman_adv_ptype;
struct net_device *soft_iface;
struct rcu_head rcu;
--
1.7.2.3