[PATCH net-next] tcp: introduce skb_rbtree_walk_safe() and use it in tcp_clean_rtx_queue()

[Yafang Shao]

When walk RB tree, we'd better use skb_rbtree_walk* helpers, that can make
the code more clear.
As skb_rbtree_walk() can't be used in tcp_clean_rtx_queue(), so the new
helper skb_rbtree_walk_safe() is introduced.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 include/linux/skbuff.h | 5 +++++
 net/ipv4/tcp_input.c   | 5 ++---
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 73902ac..37ff792 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3256,6 +3256,11 @@ static inline int __skb_grow_rcsum(struct sk_buff *skb, unsigned int len)
 		for (skb = skb_rb_first(root); skb != NULL;			\
 		     skb = skb_rb_next(skb))
 
+#define skb_rbtree_walk_safe(skb, root, tmp)					\
+		for (skb = skb_rb_first(root);					\
+		     tmp = skb ? skb_rb_next(skb) : NULL, skb != NULL;		\
+		     skb = tmp)
+
 #define skb_rbtree_walk_from(skb)						\
 		for (; skb != NULL;						\
 		     skb = skb_rb_next(skb))
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f323978..ab6add2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3043,7 +3043,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
 	struct tcp_sock *tp = tcp_sk(sk);
 	u32 prior_sacked = tp->sacked_out;
 	u32 reord = tp->snd_nxt; /* lowest acked un-retx un-sacked seq */
-	struct sk_buff *skb, *next;
+	struct sk_buff *skb, *tmp;
 	bool fully_acked = true;
 	long sack_rtt_us = -1L;
 	long seq_rtt_us = -1L;
@@ -3055,7 +3055,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
 
 	first_ackt = 0;
 
-	for (skb = skb_rb_first(&sk->tcp_rtx_queue); skb; skb = next) {
+	skb_rbtree_walk_safe(skb, &sk->tcp_rtx_queue, tmp) {
 		struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
 		const u32 start_seq = scb->seq;
 		u8 sacked = scb->sacked;
@@ -3126,7 +3126,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
 		if (!fully_acked)
 			break;
 
-		next = skb_rb_next(skb);
 		if (unlikely(skb == tp->retransmit_skb_hint))
 			tp->retransmit_skb_hint = NULL;
 		if (unlikely(skb == tp->lost_skb_hint))
-- 
1.8.3.1