netdev - [PATCH v2 net-next 6/7] neighbour: Convert RTM

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Message-ID: <20250418012727.57033-7-kuniyu@amazon.com>
Date: Thu, 17 Apr 2025 18:26:58 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>,
	Kuniyuki Iwashima <kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v2 net-next 6/7] neighbour: Convert RTM_GETNEIGHTBL to RCU.

neightbl_dump_info() calls neightbl_fill_info() and
neightbl_fill_param_info() for each neigh_tables[] entry.

Both functions rely on the table lock (read_lock_bh(&tbl->lock)),
so RTNL is not needed.

Let's fetch the table under RCU and convert RTM_GETNEIGHTBL to RCU.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/core/neighbour.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index ccfef86bb044..38732d8f0ed7 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2467,10 +2467,12 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 
 	family = ((struct rtgenmsg *)nlmsg_data(nlh))->rtgen_family;
 
+	rcu_read_lock();
+
 	for (tidx = 0; tidx < NEIGH_NR_TABLES; tidx++) {
 		struct neigh_parms *p;
 
-		tbl = rcu_dereference_rtnl(neigh_tables[tidx]);
+		tbl = rcu_dereference(neigh_tables[tidx]);
 		if (!tbl)
 			continue;
 
@@ -2504,6 +2506,8 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 		neigh_skip = 0;
 	}
 out:
+	rcu_read_unlock();
+
 	cb->args[0] = tidx;
 	cb->args[1] = nidx;
 
@@ -3811,7 +3815,8 @@ static const struct rtnl_msg_handler neigh_rtnl_msg_handlers[] __initconst = {
 	{.msgtype = RTM_DELNEIGH, .doit = neigh_delete},
 	{.msgtype = RTM_GETNEIGH, .doit = neigh_get, .dumpit = neigh_dump_info,
 	 .flags = RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED},
-	{.msgtype = RTM_GETNEIGHTBL, .dumpit = neightbl_dump_info},
+	{.msgtype = RTM_GETNEIGHTBL, .dumpit = neightbl_dump_info,
+	 .flags = RTNL_FLAG_DUMP_UNLOCKED},
 	{.msgtype = RTM_SETNEIGHTBL, .doit = neightbl_set},
 };
 
-- 
2.49.0