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Date: Wed, 29 Sep 2021 15:26:08 +0800
From: Matt Johnston <matt@...econstruct.com.au>
To: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Cc: Jeremy Kerr <jk@...econstruct.com.au>
Subject: [PATCH net-next 04/10] mctp: Add refcounts to mctp_dev
From: Jeremy Kerr <jk@...econstruct.com.au>
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@...econstruct.com.au>
---
include/net/mctpdevice.h | 5 +++++
net/mctp/device.c | 25 ++++++++++++++++---------
net/mctp/neigh.c | 4 ++--
net/mctp/route.c | 4 ++--
4 files changed, 25 insertions(+), 13 deletions(-)
diff --git a/include/net/mctpdevice.h b/include/net/mctpdevice.h
index 71a11012fac7..3a439463f055 100644
--- 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 c34963974cc1..f556c6d01abc 100644
--- 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 90ed2f02d1fb..5cc042121493 100644
--- 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 b2243b150e71..37aa67847a5a 100644
--- 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;
--
2.30.2
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