linux-kernel - [PATCH 2/4] net: use RCU noref infrastructure to track dst noref

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Message-Id: <7c7d6183314d8d4cafb9689ce498ec8759c440b0.1507294365.git.pabeni@redhat.com>
Date:   Fri,  6 Oct 2017 14:57:47 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        netdev@...r.kernel.org
Subject: [PATCH 2/4] net: use RCU noref infrastructure to track dst noref

We can now ensure noref dsts do no escape the relevant RCU
section. This does not introduce any functional changes, it adds
the relevant debug code enabled by CONFIG_RCU_NOREF_DEBUG.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 include/linux/skbuff.h | 1 +
 include/net/dst.h      | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 72299ef00061..5df77c8a0319 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -905,6 +905,7 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
 static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
 {
 	WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
+	rcu_track_noref(skb, dst, true);
 	skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
 }
 
diff --git a/include/net/dst.h b/include/net/dst.h
index 06a6765da074..6bc6fefe178e 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -294,6 +294,8 @@ static inline void refdst_drop(unsigned long refdst)
 static inline void skb_dst_drop(struct sk_buff *skb)
 {
 	if (skb->_skb_refdst) {
+		if (skb->_skb_refdst & SKB_DST_NOREF)
+			rcu_track_noref(skb, skb_dst(skb), false);
 		refdst_drop(skb->_skb_refdst);
 		skb->_skb_refdst = 0UL;
 	}
@@ -304,6 +306,8 @@ static inline void __skb_dst_copy(struct sk_buff *nskb, unsigned long refdst)
 	nskb->_skb_refdst = refdst;
 	if (!(nskb->_skb_refdst & SKB_DST_NOREF))
 		dst_clone(skb_dst(nskb));
+	else
+		rcu_track_noref(nskb, skb_dst(nskb), true);
 }
 
 static inline void skb_dst_copy(struct sk_buff *nskb, const struct sk_buff *oskb)
@@ -335,6 +339,7 @@ static inline void skb_dst_force(struct sk_buff *skb)
 		struct dst_entry *dst = skb_dst(skb);
 
 		WARN_ON(!rcu_read_lock_held());
+		rcu_track_noref(skb, dst, false);
 		if (!dst_hold_safe(dst))
 			dst = NULL;
 
-- 
2.13.6