[PATCH v1 net-next 04/11] neighbour: Remove __rcu from neigh_tables[].

[Kuniyuki Iwashima <kuniyu@google.com>]

Since commit 1bf20cc62a54 ("neighbour: remove obsolete
EXPORT_SYMBOL()") unexported neigh_table_init(), neigh_table
cannot be registered dynamically.

Let's remove RCU protection for neigh_tables[].

Note that neightbl_set() no longer needs RCU because it holds
spin_lock_bh(&tbl->lock).

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/core/neighbour.c | 23 +++++++++--------------
 net/ipv4/arp.c       |  3 +++
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 6fda0052027b..caa52bf64a2d 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1807,7 +1807,7 @@ void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms)
 
 static struct lock_class_key neigh_table_proxy_queue_class;
 
-static struct neigh_table __rcu *neigh_tables[NEIGH_NR_TABLES] __read_mostly;
+static struct neigh_table *neigh_tables[NEIGH_NR_TABLES] __read_mostly;
 
 void neigh_table_init(int index, struct neigh_table *tbl)
 {
@@ -1864,7 +1864,7 @@ void neigh_table_init(int index, struct neigh_table *tbl)
 	tbl->last_flush = now;
 	tbl->last_rand	= now + tbl->parms.reachable_time * 20;
 
-	rcu_assign_pointer(neigh_tables[index], tbl);
+	neigh_tables[index] = tbl;
 }
 
 /*
@@ -1873,8 +1873,7 @@ void neigh_table_init(int index, struct neigh_table *tbl)
  */
 int neigh_table_clear(int index, struct neigh_table *tbl)
 {
-	RCU_INIT_POINTER(neigh_tables[index], NULL);
-	synchronize_rcu();
+	neigh_tables[index] = NULL;
 
 	/* It is not clean... Fix it to unload IPv6 module safely */
 	cancel_delayed_work_sync(&tbl->managed_work);
@@ -1906,10 +1905,10 @@ static struct neigh_table *neigh_find_table(int family)
 
 	switch (family) {
 	case AF_INET:
-		tbl = rcu_dereference_rtnl(neigh_tables[NEIGH_ARP_TABLE]);
+		tbl = neigh_tables[NEIGH_ARP_TABLE];
 		break;
 	case AF_INET6:
-		tbl = rcu_dereference_rtnl(neigh_tables[NEIGH_ND_TABLE]);
+		tbl = neigh_tables[NEIGH_ND_TABLE];
 		break;
 	}
 
@@ -2391,10 +2390,8 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	ndtmsg = nlmsg_data(nlh);
 
-	rcu_read_lock();
-
 	for (tidx = 0; tidx < NEIGH_NR_TABLES; tidx++) {
-		tbl = rcu_dereference(neigh_tables[tidx]);
+		tbl = neigh_tables[tidx];
 		if (!tbl)
 			continue;
 
@@ -2408,7 +2405,6 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh,
 	}
 
 	if (!found) {
-		rcu_read_unlock();
 		err = -ENOENT;
 		goto errout;
 	}
@@ -2537,7 +2533,6 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 errout_tbl_lock:
 	spin_unlock_bh(&tbl->lock);
-	rcu_read_unlock();
 errout:
 	return err;
 }
@@ -2589,7 +2584,7 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 	for (tidx = 0; tidx < NEIGH_NR_TABLES; tidx++) {
 		struct neigh_parms *p;
 
-		tbl = rcu_dereference(neigh_tables[tidx]);
+		tbl = neigh_tables[tidx];
 		if (!tbl)
 			continue;
 
@@ -2949,7 +2944,7 @@ static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 
 	rcu_read_lock();
 	for (t = 0; t < NEIGH_NR_TABLES; t++) {
-		tbl = rcu_dereference(neigh_tables[t]);
+		tbl = neigh_tables[t];
 
 		if (!tbl)
 			continue;
@@ -3162,7 +3157,7 @@ int neigh_xmit(int index, struct net_device *dev,
 		struct neighbour *neigh;
 
 		rcu_read_lock();
-		tbl = rcu_dereference(neigh_tables[index]);
+		tbl = neigh_tables[index];
 		if (!tbl) {
 			rcu_read_unlock();
 			goto out_kfree_skb;
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index d409f606aec0..66063dd00aaa 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1495,9 +1495,12 @@ static const struct seq_operations arp_seq_ops = {
 
 static int __net_init arp_net_init(struct net *net)
 {
+#ifdef CONFIG_PROC_FS
 	if (!proc_create_net("arp", 0444, net->proc_net, &arp_seq_ops,
 			sizeof(struct neigh_seq_state)))
 		return -ENOMEM;
+#endif
+
 	return 0;
 }
 
-- 
2.55.0.679.g6767b8d81c-goog