[PATCH RFC net-next 02/21] net: add RCU variant to search for netdev_adjacent link

[Veaceslav Falico <vfalico@redhat.com>]

Currently we have only the RTNL flavour, however we can traverse it while
holding only RCU, so add the RCU search.

CC: "David S. Miller" <davem@davemloft.net>
CC: Eric Dumazet <edumazet@google.com>
CC: Jiri Pirko <jiri@resnulli.us>
CC: Alexander Duyck <alexander.h.duyck@intel.com>
CC: Cong Wang <amwang@redhat.com>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
---
 net/core/dev.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 9e4eb40..4e67a67 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4380,6 +4380,51 @@ struct netdev_adjacent {
 	struct rcu_head rcu;
 };
 
+static struct netdev_adjacent *__netdev_find_adj_rcu(struct net_device *dev,
+						     struct net_device *adj_dev,
+						     bool upper, bool neighbour)
+{
+	struct netdev_adjacent *adj;
+	struct list_head *dev_list;
+
+	if (neighbour)
+		dev_list = upper ? &dev->neighbour_dev_list.upper :
+				   &dev->neighbour_dev_list.lower;
+	else
+		dev_list = upper ? &dev->all_dev_list.upper :
+				   &dev->all_dev_list.lower;
+
+	list_for_each_entry_rcu(adj, dev_list, list) {
+		if (adj->dev == adj_dev)
+			return adj;
+	}
+	return NULL;
+}
+
+static inline struct netdev_adjacent *__netdev_find_upper_rcu(struct net_device *dev,
+							      struct net_device *udev)
+{
+	return __netdev_find_adj_rcu(dev, udev, true, false);
+}
+
+static inline struct netdev_adjacent *__netdev_find_lower_rcu(struct net_device *dev,
+							      struct net_device *ldev)
+{
+	return __netdev_find_adj_rcu(dev, ldev, false, false);
+}
+
+static inline struct netdev_adjacent *__netdev_find_upper_neighbour_rcu(struct net_device *dev,
+									struct net_device *udev)
+{
+	return __netdev_find_adj_rcu(dev, udev, true, true);
+}
+
+static inline struct netdev_adjacent *__netdev_find_lower_neighbour_rcu(struct net_device *dev,
+									struct net_device *ldev)
+{
+	return __netdev_find_adj_rcu(dev, ldev, false, true);
+}
+
 static struct netdev_adjacent *__netdev_find_adj(struct net_device *dev,
 						 struct net_device *adj_dev,
 						 bool upper, bool neighbour)
-- 
1.8.4