netdev - [PATCH net-next 08/19] ipmr: do not acquire mrt_lock while calling ip_mr

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Message-Id: <20220622051255.700309-9-edumazet@google.com>
Date:   Wed, 22 Jun 2022 05:12:44 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 08/19] ipmr: do not acquire mrt_lock while calling ip_mr_forward()

ip_mr_forward() uses standard RCU protection already.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/ipmr.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 6ea54bc3d9b6555aaa9974d81ba4acd47481724f..b0f2e6d79d62273c8c2682f28cb45fe5ec3df6f3 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1817,7 +1817,7 @@ static bool ipmr_forward_offloaded(struct sk_buff *skb, struct mr_table *mrt,
 }
 #endif
 
-/* Processing handlers for ipmr_forward */
+/* Processing handlers for ipmr_forward, under rcu_read_lock() */
 
 static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,
 			    int in_vifi, struct sk_buff *skb, int vifi)
@@ -1839,9 +1839,7 @@ static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,
 		WRITE_ONCE(vif->bytes_out, vif->bytes_out + skb->len);
 		vif_dev->stats.tx_bytes += skb->len;
 		vif_dev->stats.tx_packets++;
-		rcu_read_lock();
 		ipmr_cache_report(mrt, skb, vifi, IGMPMSG_WHOLEPKT);
-		rcu_read_unlock();
 		goto out_free;
 	}
 
@@ -1936,6 +1934,7 @@ static int ipmr_find_vif(const struct mr_table *mrt, struct net_device *dev)
 }
 
 /* "local" means that we should preserve one skb (for local delivery) */
+/* Called uner rcu_read_lock() */
 static void ip_mr_forward(struct net *net, struct mr_table *mrt,
 			  struct net_device *dev, struct sk_buff *skb,
 			  struct mfc_cache *c, int local)
@@ -1992,12 +1991,10 @@ static void ip_mr_forward(struct net *net, struct mr_table *mrt,
 			       c->_c.mfc_un.res.last_assert +
 			       MFC_ASSERT_THRESH)) {
 			c->_c.mfc_un.res.last_assert = jiffies;
-			rcu_read_lock();
 			ipmr_cache_report(mrt, skb, true_vifi, IGMPMSG_WRONGVIF);
 			if (mrt->mroute_do_wrvifwhole)
 				ipmr_cache_report(mrt, skb, true_vifi,
 						  IGMPMSG_WRVIFWHOLE);
-			rcu_read_unlock();
 		}
 		goto dont_forward;
 	}
@@ -2169,9 +2166,7 @@ int ip_mr_input(struct sk_buff *skb)
 		return -ENODEV;
 	}
 
-	read_lock(&mrt_lock);
 	ip_mr_forward(net, mrt, dev, skb, cache, local);
-	read_unlock(&mrt_lock);
 
 	if (local)
 		return ip_local_deliver(skb);
-- 
2.37.0.rc0.104.g0611611a94-goog