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mctp: Add refcounts to mctp_dev

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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>
This commit is contained in:
Jeremy Kerr
2021-09-29 15:26:08 +08:00
committed by David S. Miller
parent 73c618456d
commit 43f55f23f7
4 changed files with 25 additions and 13 deletions
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25
net/mctp/device.c
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@@ -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)