Subject: [PATCH net-next 1/2] tcp: set recv_skip_hint when tcp_inq is less than PAGE_SIZE

From: Soheil Hassas Yeganeh <[email-masked]>
Date: Wed, 26 Sep 2018 16:57:03 -0400

From: Soheil Hassas Yeganeh <[email-masked]>

When we have less than PAGE_SIZE of data on receive queue,
we set recv_skip_hint to 0. Instead, set it to the actual
number of bytes available.

Signed-off-by: Soheil Hassas Yeganeh <[email-masked]>
Signed-off-by: Eric Dumazet <[email-masked]>
---
 net/ipv4/tcp.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 69c236943f56..3e17501fc1a1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1753,6 +1753,7 @@ static int tcp_zerocopy_receive(struct sock *sk,
 	struct vm_area_struct *vma;
 	struct sk_buff *skb = NULL;
 	struct tcp_sock *tp;
+	int inq;
 	int ret;
 
 	if (address & (PAGE_SIZE - 1) || address != zc->address)
@@ -1773,12 +1774,15 @@ static int tcp_zerocopy_receive(struct sock *sk,
 
 	tp = tcp_sk(sk);
 	seq = tp->copied_seq;
-	zc->length = min_t(u32, zc->length, tcp_inq(sk));
+	inq = tcp_inq(sk);
+	zc->length = min_t(u32, zc->length, inq);
 	zc->length &= ~(PAGE_SIZE - 1);
-
-	zap_page_range(vma, address, zc->length);
-
-	zc->recv_skip_hint = 0;
+	if (zc->length) {
+		zap_page_range(vma, address, zc->length);
+		zc->recv_skip_hint = 0;
+	} else {
+		zc->recv_skip_hint = inq;
+	}
 	ret = 0;
 	while (length + PAGE_SIZE <= zc->length) {
 		if (zc->recv_skip_hint < PAGE_SIZE) {
-- 
2.19.0.605.g01d371f741-goog