[B.A.T.M.A.N.] [PATCH v2 13/30] batman-adv: Convert batadv_gw_node to kref

Sven Eckelmann
2015-12-20T13:17:53Z

batman-adv uses a self-written reference implementation which is just based
on atomic_t. This is less obvious when reading the code than kref and
therefore increases the change that the reference counting will be missed.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
v2:
- split patchset into fixes and kref migration to make it easier when the
decision is made where each patch will be applied

net/batman-adv/gateway_client.c | 40 +++++++++++++++++++++++++++++-----------
net/batman-adv/types.h | 2 +-
2 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 8350775..bf5a6ef 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -28,6 +28,7 @@
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/kernel.h>
+#include <linux/kref.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/rculist.h>
@@ -59,12 +60,29 @@
*/
#define BATADV_DHCP_CHADDR_OFFSET 28

+/**
+ * batadv_gw_node_release - release gw_node from lists and queue for free after
+ * rcu grace period
+ * @ref: kref pointer of the gw_node
+ */
+static void batadv_gw_node_release(struct kref *ref)
+{
+ struct batadv_gw_node *gw_node;
+
+ gw_node = container_of(ref, struct batadv_gw_node, refcount);
+
+ batadv_orig_node_free_ref(gw_node->orig_node);
+ kfree_rcu(gw_node, rcu);
+}
+
+/**
+ * batadv_gw_node_free_ref - decrement the gw_node refcounter and possibly
+ * release it
+ * @gw_node: gateway node to free
+ */
static void batadv_gw_node_free_ref(struct batadv_gw_node *gw_node)
{
- if (atomic_dec_and_test(&gw_node->refcount)) {
- batadv_orig_node_free_ref(gw_node->orig_node);
- kfree_rcu(gw_node, rcu);
- }
+ kref_put(&gw_node->refcount, batadv_gw_node_release);
}

static struct batadv_gw_node *
@@ -77,7 +95,7 @@ batadv_gw_get_selected_gw_node(struct batadv_priv *bat_priv)
if (!gw_node)
goto out;

- if (!atomic_inc_not_zero(&gw_node->refcount))
+ if (!kref_get_unless_zero(&gw_node->refcount))
gw_node = NULL;

out:
@@ -118,7 +136,7 @@ static void batadv_gw_select(struct batadv_priv *bat_priv,

spin_lock_bh(&bat_priv->gw.list_lock);

- if (new_gw_node && !atomic_inc_not_zero(&new_gw_node->refcount))
+ if (new_gw_node && !kref_get_unless_zero(&new_gw_node->refcount))
new_gw_node = NULL;

curr_gw_node = rcu_dereference_protected(bat_priv->gw.curr_gw, 1);
@@ -170,7 +188,7 @@ batadv_gw_get_best_gw_node(struct batadv_priv *bat_priv)
if (!router_ifinfo)
goto next;

- if (!atomic_inc_not_zero(&gw_node->refcount))
+ if (!kref_get_unless_zero(&gw_node->refcount))
goto next;

tq_avg = router_ifinfo->bat_iv.tq_avg;
@@ -188,7 +206,7 @@ batadv_gw_get_best_gw_node(struct batadv_priv *bat_priv)
if (curr_gw)
batadv_gw_node_free_ref(curr_gw);
curr_gw = gw_node;
- atomic_inc(&curr_gw->refcount);
+ kref_get(&curr_gw->refcount);
}
break;

@@ -203,7 +221,7 @@ batadv_gw_get_best_gw_node(struct batadv_priv *bat_priv)
if (curr_gw)
batadv_gw_node_free_ref(curr_gw);
curr_gw = gw_node;
- atomic_inc(&curr_gw->refcount);
+ kref_get(&curr_gw->refcount);
}
break;
}
@@ -436,7 +454,7 @@ static void batadv_gw_node_add(struct batadv_priv *bat_priv,
gw_node->orig_node = orig_node;
gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
- atomic_set(&gw_node->refcount, 1);
+ kref_init(&gw_node->refcount);

spin_lock_bh(&bat_priv->gw.list_lock);
hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.list);
@@ -469,7 +487,7 @@ batadv_gw_node_get(struct batadv_priv *bat_priv,
if (gw_node_tmp->orig_node != orig_node)
continue;

- if (!atomic_inc_not_zero(&gw_node_tmp->refcount))
+ if (!kref_get_unless_zero(&gw_node_tmp->refcount))
continue;

gw_node = gw_node_tmp;
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 091ad76..0b3cbdb 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -342,7 +342,7 @@ struct batadv_gw_node {
struct batadv_orig_node *orig_node;
u32 bandwidth_down;
u32 bandwidth_up;
- atomic_t refcount;
+ struct kref refcount;
struct rcu_head rcu;
};

--
2.6.4