[PATCH net-next v1 1/4] net: devmem: pass net_device pointer to net_devmem_lock_dev()

[Mina Almasry]

Upcoming changes for leased queue support will track the physical DMA
device and the bound device in separate net_device pointers on struct
net_devmem_dmabuf_binding, with different teardown paths locking
different pointers.

Generalize net_devmem_lock_dev() to take a struct net_device **dev_ptr
instead of struct net_devmem_dmabuf_binding *. No functional change.

Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
---
 net/core/devmem.c      | 36 ++++++++++++++++++------------------
 net/core/devmem.h      |  4 ++--
 net/core/netdev-genl.c |  2 +-
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/net/core/devmem.c b/net/core/devmem.c
index 5c7d9640e9d14..f164c90e90b3b 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -85,39 +85,39 @@ net_devmem_dmabuf_binding_unmap(struct net_devmem_dmabuf_binding *binding)
 }
 
 /**
- * net_devmem_lock_dev() - lock a binding's net_device if still alive
- * @binding:		devmem binding whose @dev pointer to lock
+ * net_devmem_lock_dev() - lock a binding's net_device pointer if still alive
+ * @dev_ptr:		pointer to the net_device field on a devmem binding
  * @dev_tracker:	reftracker for the held net_device reference
  *
- * Safely dereference @binding->dev, acquire netdev_lock() on the device, and
- * verify that @binding->dev has not been cleared while waiting for the lock.
+ * Safely dereference @dev_ptr, acquire netdev_lock() on the device, and
+ * verify that *@dev_ptr has not been cleared while waiting for the lock.
  *
- * Invariant: @binding->dev is set once at bind time and is only ever cleared to
- * NULL while holding netdev_lock(dev) (in mp_dmabuf_devmem_uninstall(),
- * net_devmem_unbind_dmabuf(), or net_devmem_dev_unregister() during
- * NETDEV_UNREGISTER before synchronize_net() and netdev_run_todo() free the
- * net_device).
+ * Invariant: *@dev_ptr is set once at bind time and is only ever cleared to
+ * NULL while holding netdev_lock() on that device (in
+ * mp_dmabuf_devmem_uninstall(), net_devmem_unbind_dmabuf(), or
+ * net_devmem_dev_unregister() during NETDEV_UNREGISTER before
+ * synchronize_net() and netdev_run_todo() free the net_device).
  *
- * Taking rcu_read_lock() guarantees that a non-NULL @dev read from
- * @binding->dev has not yet completed unregister_netdevice_many_notify()
+ * Taking rcu_read_lock() guarantees that a non-NULL device read from
+ * *@dev_ptr has not yet completed unregister_netdevice_many_notify()
  * (which waits for an RCU grace period via synchronize_net() after
  * NETDEV_UNREGISTER before freeing the net_device), so netdev_hold() can
  * safely acquire a reference before sleeping on netdev_lock(). Once
- * netdev_lock(dev) is held, re-checking that READ_ONCE(binding->dev) == dev
- * guarantees that the device has not yet been detached from @binding and
+ * netdev_lock() is held, re-checking that READ_ONCE(*dev_ptr) == dev
+ * guarantees that the device has not yet been detached from the binding and
  * cannot finish unregistering until net_devmem_unlock_dev().
  *
- * Return: The locked and held net_device if @binding->dev is still non-NULL,
+ * Return: The locked and held net_device if *@dev_ptr is still non-NULL,
  * or NULL if already cleared.
  */
 struct net_device *
-net_devmem_lock_dev(struct net_devmem_dmabuf_binding *binding,
+net_devmem_lock_dev(struct net_device **dev_ptr,
 		    netdevice_tracker *dev_tracker)
 {
 	struct net_device *dev;
 
 	rcu_read_lock();
-	dev = READ_ONCE(binding->dev);
+	dev = READ_ONCE(*dev_ptr);
 	if (!dev) {
 		rcu_read_unlock();
 		return NULL;
@@ -126,7 +126,7 @@ net_devmem_lock_dev(struct net_devmem_dmabuf_binding *binding,
 	rcu_read_unlock();
 
 	netdev_lock(dev);
-	if (READ_ONCE(binding->dev) != dev) {
+	if (READ_ONCE(*dev_ptr) != dev) {
 		netdev_unlock(dev);
 		netdev_put(dev, dev_tracker);
 		return NULL;
@@ -157,7 +157,7 @@ void __net_devmem_dmabuf_binding_free(struct work_struct *wq)
 		     binding->area.num_niovs, binding->free_count);
 
 	kvfree(binding->area.niovs);
-	dev = net_devmem_lock_dev(binding, &dev_tracker);
+	dev = net_devmem_lock_dev(&binding->dev, &dev_tracker);
 	net_devmem_dmabuf_binding_unmap(binding);
 	xa_erase(&net_devmem_dmabuf_bindings, binding->id);
 	net_devmem_unlock_dev(dev, &dev_tracker);
diff --git a/net/core/devmem.h b/net/core/devmem.h
index c4f476947dfaa..c0aaba0041ff6 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -100,7 +100,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
 		       struct netlink_ext_ack *extack);
 struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id);
 struct net_device *
-net_devmem_lock_dev(struct net_devmem_dmabuf_binding *binding,
+net_devmem_lock_dev(struct net_device **dev_ptr,
 		    netdevice_tracker *dev_tracker);
 void net_devmem_unlock_dev(struct net_device *dev,
 			   netdevice_tracker *dev_tracker);
@@ -189,7 +189,7 @@ static inline struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id)
 }
 
 static inline struct net_device *
-net_devmem_lock_dev(struct net_devmem_dmabuf_binding *binding,
+net_devmem_lock_dev(struct net_device **dev_ptr,
 		    netdevice_tracker *dev_tracker)
 {
 	return NULL;
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 9c5bf17b04e57..2826f7e328340 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1476,7 +1476,7 @@ void netdev_nl_sock_priv_destroy(struct netdev_nl_sock *priv)
 
 	mutex_lock(&priv->lock);
 	list_for_each_entry_safe(binding, temp, &priv->bindings, list) {
-		dev = net_devmem_lock_dev(binding, &dev_tracker);
+		dev = net_devmem_lock_dev(&binding->dev, &dev_tracker);
 		net_devmem_unbind_dmabuf(binding);
 		net_devmem_unlock_dev(dev, &dev_tracker);
 	}
-- 
2.56.0.385.gac671c819a-goog