[PATCH v1 net-next 06/13] mpls: Add mpls_dev_rcu().

[Kuniyuki Iwashima <kuniyu@google.com>]

mpls_dev_get() uses rcu_dereference_rtnl() to fetch dev->mpls_ptr.

We will replace RTNL with a dedicated mutex to protect the field.

Then, we will use rcu_dereference_protected() for clarity.

Let's add mpls_dev_rcu() for the RCU reader.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/mpls/af_mpls.c       | 12 ++++++------
 net/mpls/internal.h      |  5 +++++
 net/mpls/mpls_iptunnel.c |  2 +-
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index efc6c7da5766..10130b90c439 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -136,7 +136,7 @@ void mpls_stats_inc_outucastpkts(struct net *net,
 	struct mpls_dev *mdev;
 
 	if (skb->protocol == htons(ETH_P_MPLS_UC)) {
-		mdev = mpls_dev_get(dev);
+		mdev = mpls_dev_rcu(dev);
 		if (mdev)
 			MPLS_INC_STATS_LEN(mdev, skb->len,
 					   tx_packets,
@@ -358,7 +358,7 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
 
 	/* Careful this entire function runs inside of an rcu critical section */
 
-	mdev = mpls_dev_get(dev);
+	mdev = mpls_dev_rcu(dev);
 	if (!mdev)
 		goto drop;
 
@@ -467,7 +467,7 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
 	return 0;
 
 tx_err:
-	out_mdev = out_dev ? mpls_dev_get(out_dev) : NULL;
+	out_mdev = out_dev ? mpls_dev_rcu(out_dev) : NULL;
 	if (out_mdev)
 		MPLS_INC_STATS(out_mdev, tx_errors);
 	goto drop;
@@ -1118,7 +1118,7 @@ static int mpls_fill_stats_af(struct sk_buff *skb,
 	struct mpls_dev *mdev;
 	struct nlattr *nla;
 
-	mdev = mpls_dev_get(dev);
+	mdev = mpls_dev_rcu(dev);
 	if (!mdev)
 		return -ENODATA;
 
@@ -1138,7 +1138,7 @@ static size_t mpls_get_stats_af_size(const struct net_device *dev)
 {
 	struct mpls_dev *mdev;
 
-	mdev = mpls_dev_get(dev);
+	mdev = mpls_dev_rcu(dev);
 	if (!mdev)
 		return 0;
 
@@ -1341,7 +1341,7 @@ static int mpls_netconf_dump_devconf(struct sk_buff *skb,
 
 	rcu_read_lock();
 	for_each_netdev_dump(net, dev, ctx->ifindex) {
-		mdev = mpls_dev_get(dev);
+		mdev = mpls_dev_rcu(dev);
 		if (!mdev)
 			continue;
 		err = mpls_netconf_fill_devconf(skb, mdev,
diff --git a/net/mpls/internal.h b/net/mpls/internal.h
index e491427ea08a..080e82010022 100644
--- a/net/mpls/internal.h
+++ b/net/mpls/internal.h
@@ -185,6 +185,11 @@ static inline struct mpls_entry_decoded mpls_entry_decode(struct mpls_shim_hdr *
 	return result;
 }
 
+static inline struct mpls_dev *mpls_dev_rcu(const struct net_device *dev)
+{
+	return rcu_dereference(dev->mpls_ptr);
+}
+
 static inline struct mpls_dev *mpls_dev_get(const struct net_device *dev)
 {
 	return rcu_dereference_rtnl(dev->mpls_ptr);
diff --git a/net/mpls/mpls_iptunnel.c b/net/mpls/mpls_iptunnel.c
index cfbab7b2fec7..1a1a0eb5b787 100644
--- a/net/mpls/mpls_iptunnel.c
+++ b/net/mpls/mpls_iptunnel.c
@@ -153,7 +153,7 @@ static int mpls_xmit(struct sk_buff *skb)
 	return LWTUNNEL_XMIT_DONE;
 
 drop:
-	out_mdev = out_dev ? mpls_dev_get(out_dev) : NULL;
+	out_mdev = out_dev ? mpls_dev_rcu(out_dev) : NULL;
 	if (out_mdev)
 		MPLS_INC_STATS(out_mdev, tx_errors);
 	kfree_skb(skb);
-- 
2.51.1.838.g19442a804e-goog