[PATCH net 1/2] net: core: make bond_get_lowest_level_rcu() generic

[Taehee Yoo <ap420073@gmail.com>]

The purpose of bond_get_lowest_level_rcu() is to get nested_level under
RCU. Because dev->nested_level is protected by RTNL, so it shouldn't be
used without RTNL. But bonding module needs this value under RCU without
RTNL.
So, this function was added.

But, there is another module, which needs this function.
So, make this function generic.
the new name is netdev_get_nest_level_rcu().

Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---
 drivers/net/bonding/bond_main.c | 45 +--------------------------------
 include/linux/netdevice.h       |  1 +
 net/core/dev.c                  | 44 ++++++++++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 44 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 83ef62db6285..a9feb039ffa6 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3754,47 +3754,6 @@ static void bond_fold_stats(struct rtnl_link_stats64 *_res,
 	}
 }
 
-#ifdef CONFIG_LOCKDEP
-static int bond_get_lowest_level_rcu(struct net_device *dev)
-{
-	struct net_device *ldev, *next, *now, *dev_stack[MAX_NEST_DEV + 1];
-	struct list_head *niter, *iter, *iter_stack[MAX_NEST_DEV + 1];
-	int cur = 0, max = 0;
-
-	now = dev;
-	iter = &dev->adj_list.lower;
-
-	while (1) {
-		next = NULL;
-		while (1) {
-			ldev = netdev_next_lower_dev_rcu(now, &iter);
-			if (!ldev)
-				break;
-
-			next = ldev;
-			niter = &ldev->adj_list.lower;
-			dev_stack[cur] = now;
-			iter_stack[cur++] = iter;
-			if (max <= cur)
-				max = cur;
-			break;
-		}
-
-		if (!next) {
-			if (!cur)
-				return max;
-			next = dev_stack[--cur];
-			niter = iter_stack[cur];
-		}
-
-		now = next;
-		iter = niter;
-	}
-
-	return max;
-}
-#endif
-
 static void bond_get_stats(struct net_device *bond_dev,
 			   struct rtnl_link_stats64 *stats)
 {
@@ -3806,9 +3765,7 @@ static void bond_get_stats(struct net_device *bond_dev,
 
 
 	rcu_read_lock();
-#ifdef CONFIG_LOCKDEP
-	nest_level = bond_get_lowest_level_rcu(bond_dev);
-#endif
+	nest_level = netdev_get_nest_level_rcu(bond_dev);
 
 	spin_lock_nested(&bond->stats_lock, nest_level);
 	memcpy(stats, &bond->bond_stats, sizeof(*stats));
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 87a5d186faff..507c06bf5dba 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4699,6 +4699,7 @@ int netdev_walk_all_lower_dev(struct net_device *dev,
 			      int (*fn)(struct net_device *lower_dev,
 					struct netdev_nested_priv *priv),
 			      struct netdev_nested_priv *priv);
+int netdev_get_nest_level_rcu(struct net_device *dev);
 int netdev_walk_all_lower_dev_rcu(struct net_device *dev,
 				  int (*fn)(struct net_device *lower_dev,
 					    struct netdev_nested_priv *priv),
diff --git a/net/core/dev.c b/net/core/dev.c
index 15fe36332fb8..efc2bf88eafd 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7709,6 +7709,50 @@ static int __netdev_update_lower_level(struct net_device *dev,
 	return 0;
 }
 
+int netdev_get_nest_level_rcu(struct net_device *dev)
+{
+#ifdef CONFIG_LOCKDEP
+	struct net_device *ldev, *next, *now, *dev_stack[MAX_NEST_DEV + 1];
+	struct list_head *niter, *iter, *iter_stack[MAX_NEST_DEV + 1];
+	int cur = 0, max = 0;
+
+	now = dev;
+	iter = &dev->adj_list.lower;
+
+	while (1) {
+		next = NULL;
+		while (1) {
+			ldev = netdev_next_lower_dev_rcu(now, &iter);
+			if (!ldev)
+				break;
+
+			next = ldev;
+			niter = &ldev->adj_list.lower;
+			dev_stack[cur] = now;
+			iter_stack[cur++] = iter;
+			if (max <= cur)
+				max = cur;
+			break;
+		}
+
+		if (!next) {
+			if (!cur)
+				return max;
+			next = dev_stack[--cur];
+			niter = iter_stack[cur];
+		}
+
+		now = next;
+		iter = niter;
+	}
+
+	return max;
+#else
+	return 0;
+#endif
+}
+EXPORT_SYMBOL_GPL(netdev_get_nest_level_rcu);
+
 int netdev_walk_all_lower_dev_rcu(struct net_device *dev,
 				  int (*fn)(struct net_device *dev,
 					    struct netdev_nested_priv *priv),
-- 
2.17.1