tcp: small optimization in tcp recvmsg()

When reading large chunks of data, incoming packets might
be added to the backlog from BH.

tcp recvmsg() detects the backlog queue is not empty, and uses
a release_sock()/lock_sock() pair to process this backlog.

We now have __sk_flush_backlog() to perform this
a bit faster.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 862e8cb8dda51e76300a427783a7d8c32e82cc7f..24d77a32c9cbcdf0e4380ec6d9aa3e42d2cf8730 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2409,8 +2409,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
 
                if (copied >= target) {
                        /* Do not sleep, just process backlog. */
-                       release_sock(sk);
-                       lock_sock(sk);
+                       __sk_flush_backlog(sk);
                } else {
                        sk_wait_data(sk, &timeo, last);
                }