[PATCH net-next 2/2] tcp: factorize logic into tcp_epollin_ready()

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

Both tcp_data_ready() and tcp_stream_is_readable() share the same logic.

Add tcp_epollin_ready() helper to avoid duplication.

Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Arjun Roy <arjun...@google.com>
Cc: Wei Wang <wei...@google.com>
---
 include/net/tcp.h    | 12 ++++++++++++
 net/ipv4/tcp.c       | 16 ++++------------
 net/ipv4/tcp_input.c | 11 ++---------
 3 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 
244208f6f6c2ace87920b633e469421f557427a6..484eb2362645fd478f59b26b42457ecf4510eb14
 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1442,6 +1442,18 @@ static inline bool tcp_rmem_pressure(const struct sock 
*sk)
        return atomic_read(&sk->sk_rmem_alloc) > threshold;
 }
 
+static inline bool tcp_epollin_ready(const struct sock *sk, int target)
+{
+       const struct tcp_sock *tp = tcp_sk(sk);
+       int avail = READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->copied_seq);
+
+       if (avail <= 0)
+               return false;
+
+       return (avail >= target) || tcp_rmem_pressure(sk) ||
+              (tcp_receive_window(tp) <= inet_csk(sk)->icsk_ack.rcv_mss);
+}
+
 extern void tcp_openreq_init_rwin(struct request_sock *req,
                                  const struct sock *sk_listener,
                                  const struct dst_entry *dst);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 
9896ca10bb340924b779cb6a7606d57fdd5c3357..7a6b58ae408d1fb1e5536ccfed8215be123f3b57
 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -481,19 +481,11 @@ static void tcp_tx_timestamp(struct sock *sk, u16 tsflags)
        }
 }
 
-static inline bool tcp_stream_is_readable(const struct tcp_sock *tp,
-                                         int target, struct sock *sk)
+static bool tcp_stream_is_readable(struct sock *sk, int target)
 {
-       int avail = READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->copied_seq);
+       if (tcp_epollin_ready(sk, target))
+               return true;
 
-       if (avail > 0) {
-               if (avail >= target)
-                       return true;
-               if (tcp_rmem_pressure(sk))
-                       return true;
-               if (tcp_receive_window(tp) <= inet_csk(sk)->icsk_ack.rcv_mss)
-                       return true;
-       }
        if (sk->sk_prot->stream_memory_read)
                return sk->sk_prot->stream_memory_read(sk);
        return false;
@@ -568,7 +560,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, 
poll_table *wait)
                    tp->urg_data)
                        target++;
 
-               if (tcp_stream_is_readable(tp, target, sk))
+               if (tcp_stream_is_readable(sk, target))
                        mask |= EPOLLIN | EPOLLRDNORM;
 
                if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 
a8f8f98159531e5d1c80660972148986f6acd20a..e32a7056cb7640c67ef2d6a4d9484684d2602fcd
 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4924,15 +4924,8 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, 
size_t size)
 
 void tcp_data_ready(struct sock *sk)
 {
-       const struct tcp_sock *tp = tcp_sk(sk);
-       int avail = tp->rcv_nxt - tp->copied_seq;
-
-       if (avail < sk->sk_rcvlowat && !tcp_rmem_pressure(sk) &&
-           !sock_flag(sk, SOCK_DONE) &&
-           tcp_receive_window(tp) > inet_csk(sk)->icsk_ack.rcv_mss)
-               return;
-
-       sk->sk_data_ready(sk);
+       if (tcp_epollin_ready(sk, sk->sk_rcvlowat))
+               sk->sk_data_ready(sk);
 }
 
 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
-- 
2.30.0.478.g8a0d178c01-goog