mctp: Add refcounts to mctp_dev

Currently, we tie the struct mctp_dev lifetime to the underlying struct
net_device, and hold/put that device as a proxy for a separate mctp_dev
refcount. This works because we're not holding any references to the
mctp_dev that are different from the netdev lifetime.

In a future change we'll break that assumption though, as we'll need to
hold mctp_dev references in a workqueue, which might live past the
netdev unregister notification.

In order to support that, this change introduces a refcount on the
mctp_dev, currently taken by the net_device->mctp_ptr reference, and
released on netdev unregister events. We can then use this for future
references that might outlast the net device.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/mctpdevice.h b/include/net/mctpdevice.h
index 71a1101..3a43946 100644 (file)
--- a/include/net/mctpdevice.h
+++ b/include/net/mctpdevice.h
@@ -17,6 +17,8 @@
 struct mctp_dev {
        struct net_device       *dev;
 
+       refcount_t              refs;
+
        unsigned int            net;
 
        /* Only modified under RTNL. Reads have addrs_lock held */
@@ -32,4 +34,7 @@ struct mctp_dev {
 struct mctp_dev *mctp_dev_get_rtnl(const struct net_device *dev);
 struct mctp_dev *__mctp_dev_get(const struct net_device *dev);
 
+void mctp_dev_hold(struct mctp_dev *mdev);
+void mctp_dev_put(struct mctp_dev *mdev);
+
 #endif /* __NET_MCTPDEVICE_H */

diff --git a/net/mctp/device.c b/net/mctp/device.c
index c349639..f556c6d 100644 (file)
--- a/net/mctp/device.c
+++ b/net/mctp/device.c
@@ -35,14 +35,6 @@ struct mctp_dev *mctp_dev_get_rtnl(const struct net_device *dev)
        return rtnl_dereference(dev->mctp_ptr);
 }
 
-static void mctp_dev_destroy(struct mctp_dev *mdev)
-{
-       struct net_device *dev = mdev->dev;
-
-       dev_put(dev);
-       kfree_rcu(mdev, rcu);
-}
-
 static int mctp_fill_addrinfo(struct sk_buff *skb, struct netlink_callback *cb,
                              struct mctp_dev *mdev, mctp_eid_t eid)
 {
@@ -255,6 +247,19 @@ static int mctp_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
        return 0;
 }
 
+void mctp_dev_hold(struct mctp_dev *mdev)
+{
+       refcount_inc(&mdev->refs);
+}
+
+void mctp_dev_put(struct mctp_dev *mdev)
+{
+       if (refcount_dec_and_test(&mdev->refs)) {
+               dev_put(mdev->dev);
+               kfree_rcu(mdev, rcu);
+       }
+}
+
 static struct mctp_dev *mctp_add_dev(struct net_device *dev)
 {
        struct mctp_dev *mdev;
@@ -270,7 +275,9 @@ static struct mctp_dev *mctp_add_dev(struct net_device *dev)
        mdev->net = mctp_default_net(dev_net(dev));
 
        /* associate to net_device */
+       refcount_set(&mdev->refs, 1);
        rcu_assign_pointer(dev->mctp_ptr, mdev);
+
        dev_hold(dev);
        mdev->dev = dev;
 
@@ -345,7 +352,7 @@ static void mctp_unregister(struct net_device *dev)
        mctp_neigh_remove_dev(mdev);
        kfree(mdev->addrs);
 
-       mctp_dev_destroy(mdev);
+       mctp_dev_put(mdev);
 }
 
 static int mctp_register(struct net_device *dev)

diff --git a/net/mctp/neigh.c b/net/mctp/neigh.c
index 90ed2f0..5cc0421 100644 (file)
--- a/net/mctp/neigh.c
+++ b/net/mctp/neigh.c
@@ -47,7 +47,7 @@ static int mctp_neigh_add(struct mctp_dev *mdev, mctp_eid_t eid,
        }
        INIT_LIST_HEAD(&neigh->list);
        neigh->dev = mdev;
-       dev_hold(neigh->dev->dev);
+       mctp_dev_hold(neigh->dev);
        neigh->eid = eid;
        neigh->source = source;
        memcpy(neigh->ha, lladdr, lladdr_len);
@@ -63,7 +63,7 @@ static void __mctp_neigh_free(struct rcu_head *rcu)
 {
        struct mctp_neigh *neigh = container_of(rcu, struct mctp_neigh, rcu);
 
-       dev_put(neigh->dev->dev);
+       mctp_dev_put(neigh->dev);
        kfree(neigh);
 }
 

diff --git a/net/mctp/route.c b/net/mctp/route.c
index b2243b1..37aa678 100644 (file)
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -455,7 +455,7 @@ static int mctp_route_output(struct mctp_route *route, struct sk_buff *skb)
 static void mctp_route_release(struct mctp_route *rt)
 {
        if (refcount_dec_and_test(&rt->refs)) {
-               dev_put(rt->dev->dev);
+               mctp_dev_put(rt->dev);
                kfree_rcu(rt, rcu);
        }
 }
@@ -815,7 +815,7 @@ static int mctp_route_add(struct mctp_dev *mdev, mctp_eid_t daddr_start,
        rt->max = daddr_start + daddr_extent;
        rt->mtu = mtu;
        rt->dev = mdev;
-       dev_hold(rt->dev->dev);
+       mctp_dev_hold(rt->dev);
        rt->type = type;
        rt->output = rtfn;