netdev - [PATCH net-next v5 09/14] kcm: Use splice

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Date: Wed,  7 Jun 2023 15:05:54 +0100
From: David Howells <dhowells@...hat.com>
To: netdev@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc: David Howells <dhowells@...hat.com>,
	Chuck Lever <chuck.lever@...cle.com>,
	Boris Pismenny <borisp@...dia.com>,
	John Fastabend <john.fastabend@...il.com>,
	Jakub Kicinski <kuba@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	David Ahern <dsahern@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	Jens Axboe <axboe@...nel.dk>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Tom Herbert <tom@...bertland.com>,
	Tom Herbert <tom@...ntonium.net>,
	Cong Wang <cong.wang@...edance.com>
Subject: [PATCH net-next v5 09/14] kcm: Use splice_eof() to flush

Allow splice to undo the effects of MSG_MORE after prematurely ending a
splice/sendfile due to getting an EOF condition (->splice_read() returned
0) after splice had called sendmsg() with MSG_MORE set when the user didn't
set MSG_MORE.

Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Link: https://lore.kernel.org/r/CAHk-=wh=V579PDYvkpnTobCLGczbgxpMgGmmhqiTyE34Cpi5Gg@mail.gmail.com/
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Tom Herbert <tom@...bertland.com>
cc: Tom Herbert <tom@...ntonium.net>
cc: Cong Wang <cong.wang@...edance.com>
cc: Jakub Kicinski <kuba@...nel.org>
cc: Eric Dumazet <edumazet@...gle.com>
cc: "David S. Miller" <davem@...emloft.net>
cc: Paolo Abeni <pabeni@...hat.com>
cc: Jens Axboe <axboe@...nel.dk>
cc: Matthew Wilcox <willy@...radead.org>
cc: netdev@...r.kernel.org
---
 net/kcm/kcmsock.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index ba22af16b96d..d0d8c54562d6 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -968,6 +968,19 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	return err;
 }
 
+static void kcm_splice_eof(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct kcm_sock *kcm = kcm_sk(sk);
+
+	if (skb_queue_empty(&sk->sk_write_queue))
+		return;
+
+	lock_sock(sk);
+	kcm_write_msgs(kcm);
+	release_sock(sk);
+}
+
 static ssize_t kcm_sendpage(struct socket *sock, struct page *page,
 			    int offset, size_t size, int flags)
 
@@ -1773,6 +1786,7 @@ static const struct proto_ops kcm_dgram_ops = {
 	.sendmsg =	kcm_sendmsg,
 	.recvmsg =	kcm_recvmsg,
 	.mmap =		sock_no_mmap,
+	.splice_eof =	kcm_splice_eof,
 	.sendpage =	kcm_sendpage,
 };
 
@@ -1794,6 +1808,7 @@ static const struct proto_ops kcm_seqpacket_ops = {
 	.sendmsg =	kcm_sendmsg,
 	.recvmsg =	kcm_recvmsg,
 	.mmap =		sock_no_mmap,
+	.splice_eof =	kcm_splice_eof,
 	.sendpage =	kcm_sendpage,
 	.splice_read =	kcm_splice_read,
 };