netdev - [net-next 5/8] tcp: Fast return if inq < PAGE

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Message-Id: <20201112190205.633640-6-arjunroy.kdev@gmail.com>
Date:   Thu, 12 Nov 2020 11:02:02 -0800
From:   Arjun Roy <arjunroy.kdev@...il.com>
To:     davem@...emloft.net, netdev@...r.kernel.org
Cc:     arjunroy@...gle.com, edumazet@...gle.com, soheil@...gle.com
Subject: [net-next 5/8] tcp: Fast return if inq < PAGE_SIZE for recv zerocopy.

From: Arjun Roy <arjunroy@...gle.com>

Sometimes, we may call tcp receive zerocopy when inq is 0,
or inq < PAGE_SIZE, in which case we cannot remap pages. In this case,
simply return the appropriate hint for regular copying without taking
mmap_sem.

Signed-off-by: Arjun Roy <arjunroy@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>

---
 net/ipv4/tcp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index f3bd606a678d..38f8e03f1182 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1885,6 +1885,14 @@ static int tcp_zerocopy_receive(struct sock *sk,

 	sock_rps_record_flow(sk);

+	if (inq < PAGE_SIZE) {
+		zc->length = 0;
+		zc->recv_skip_hint = inq;
+		if (!inq && sock_flag(sk, SOCK_DONE))
+			return -EIO;
+		return 0;
+	}
+
 	mmap_read_lock(current->mm);

 	vma = find_vma(current->mm, address);
-- 
2.29.2.222.g5d2a92d10f8-goog