netdev - [PATCH v2 net-next] tcp_metrics: fix wrong lockdep annotations

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Date:	Mon, 16 Mar 2015 07:14:34 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Vagin <avagin@...allels.com>
Cc:	David Miller <davem@...emloft.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, netdev@...r.kernel.org
Subject: [PATCH v2 net-next] tcp_metrics: fix wrong lockdep annotations

From: Eric Dumazet <edumazet@...gle.com>

Changes in tcp_metric hash table are protected by tcp_metrics_lock
only, not by genl_mutex

While we are at it use deref_locked() instead of rcu_dereference()
in tcp_new() to avoid unnecessary barrier, as we hold tcp_metrics_lock
as well.
 
Reported-by: Andrew Vagin <avagin@...allels.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Fixes: 098a697b497e ("tcp_metrics: Use a single hash table for all network namespaces.")
---
 net/ipv4/tcp_metrics.c |   20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 366728cbee4a692394696f13e6aacf0331990eed..5bef3513af77afc8943d99a107f74155b9979aaa 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -152,6 +152,9 @@ static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst
 #define TCP_METRICS_RECLAIM_DEPTH	5
 #define TCP_METRICS_RECLAIM_PTR		(struct tcp_metrics_block *) 0x1UL
 
+#define deref_locked(p)	\
+	rcu_dereference_protected(p, lockdep_is_held(&tcp_metrics_lock))
+
 static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst,
 					  struct inetpeer_addr *saddr,
 					  struct inetpeer_addr *daddr,
@@ -180,9 +183,9 @@ static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst,
 	if (unlikely(reclaim)) {
 		struct tcp_metrics_block *oldest;
 
-		oldest = rcu_dereference(tcp_metrics_hash[hash].chain);
-		for (tm = rcu_dereference(oldest->tcpm_next); tm;
-		     tm = rcu_dereference(tm->tcpm_next)) {
+		oldest = deref_locked(tcp_metrics_hash[hash].chain);
+		for (tm = deref_locked(oldest->tcpm_next); tm;
+		     tm = deref_locked(tm->tcpm_next)) {
 			if (time_before(tm->tcpm_stamp, oldest->tcpm_stamp))
 				oldest = tm;
 		}
@@ -1040,12 +1043,6 @@ out_free:
 	return ret;
 }
 
-#define deref_locked_genl(p)	\
-	rcu_dereference_protected(p, lockdep_genl_is_held() && \
-				     lockdep_is_held(&tcp_metrics_lock))
-
-#define deref_genl(p)	rcu_dereference_protected(p, lockdep_genl_is_held())
-
 static void tcp_metrics_flush_all(struct net *net)
 {
 	unsigned int max_rows = 1U << tcp_metrics_hash_log;
@@ -1057,8 +1054,7 @@ static void tcp_metrics_flush_all(struct net *net)
 		struct tcp_metrics_block __rcu **pp;
 		spin_lock_bh(&tcp_metrics_lock);
 		pp = &hb->chain;
-		for (tm = deref_locked_genl(*pp); tm;
-		     tm = deref_locked_genl(*pp)) {
+		for (tm = deref_locked(*pp); tm; tm = deref_locked(*pp)) {
 			if (net_eq(tm_net(tm), net)) {
 				*pp = tm->tcpm_next;
 				kfree_rcu(tm, rcu_head);
@@ -1097,7 +1093,7 @@ static int tcp_metrics_nl_cmd_del(struct sk_buff *skb, struct genl_info *info)
 	hb = tcp_metrics_hash + hash;
 	pp = &hb->chain;
 	spin_lock_bh(&tcp_metrics_lock);
-	for (tm = deref_locked_genl(*pp); tm; tm = deref_locked_genl(*pp)) {
+	for (tm = deref_locked(*pp); tm; tm = deref_locked(*pp)) {
 		if (addr_same(&tm->tcpm_daddr, &daddr) &&
 		    (!src || addr_same(&tm->tcpm_saddr, &saddr)) &&
 		    net_eq(tm_net(tm), net)) {


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