[Patch net v2 3/4] tcp: refactor tcp_read_skb() a bit

[Cong Wang <xiyou.wangcong@gmail.com>]

From: Cong Wang <cong.wang@bytedance.com>

As tcp_read_skb() only reads one skb at a time, the while loop is
unnecessary, we can turn it into an if. This also simplifies the
code logic.

Cc: Eric Dumazet <edumazet@google.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
---
 net/ipv4/tcp.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 181a0d350123..5212a7512269 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1761,27 +1761,18 @@ int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 	if (sk->sk_state == TCP_LISTEN)
 		return -ENOTCONN;
 
-	while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
-		int used;
-
+	skb = tcp_recv_skb(sk, seq, &offset);
+	if (skb) {
 		__skb_unlink(skb, &sk->sk_receive_queue);
 		WARN_ON(!skb_set_owner_sk_safe(skb, sk));
-		used = recv_actor(sk, skb);
-		if (used <= 0) {
-			if (!copied)
-				copied = used;
-			break;
-		}
-		seq += used;
-		copied += used;
-
-		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
-			++seq;
-			break;
+		copied = recv_actor(sk, skb);
+		if (copied > 0) {
+			seq += copied;
+			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
+				++seq;
 		}
-		break;
+		consume_skb(skb);
 	}
-	consume_skb(skb);
 	WRITE_ONCE(tp->copied_seq, seq);
 
 	tcp_rcv_space_adjust(sk);
-- 
2.34.1