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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <20230607153232.93980-1-kuniyu@amazon.com>
References: <20230607153232.93980-1-kuniyu@amazon.com> <20230607140559.2263470-8-dhowells@redhat.com>
To:     Kuniyuki Iwashima <kuniyu@amazon.com>
Cc:     dhowells@redhat.com, axboe@kernel.dk, borisp@nvidia.com,
        chuck.lever@oracle.com, davem@davemloft.net, dsahern@kernel.org,
        edumazet@google.com, john.fastabend@gmail.com, kuba@kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        netdev@vger.kernel.org, pabeni@redhat.com,
        torvalds@linux-foundation.org, willemdebruijn.kernel@gmail.com,
        willy@infradead.org
Subject: Re: [PATCH net-next v5 07/14] ipv4, ipv6: Use splice_eof() to flush
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Date:   Wed, 07 Jun 2023 16:43:52 +0100
Message-ID: <2269950.1686152632@warthog.procyon.org.uk>
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Kuniyuki Iwashima <kuniyu@amazon.com> wrote:

> > +	/* IPV6_ADDRFORM can change sk->sk_prot under us. */
> > +	prot =3D READ_ONCE(sk->sk_prot);
> > +	if (prot->splice_eof)
> > +		sk->sk_prot->splice_eof(sock);
> =

> We need to use prot here.

Yeah.

> > +	if (up->pending =3D=3D AF_INET)
> > +		udp_splice_eof(sock);
> =

> Do we need this ?

Actually, no.  udp_v6_push_pending_frames() will do this.

> > +	lock_sock(sk);
> > +	if (up->pending && !READ_ONCE(up->corkflag))
> > +		udp_push_pending_frames(sk);
> =

> We should use udp_v6_push_pending_frames(sk) as up->pending
> could be AF_INET even after the test above.

Yeah.

Updated version attached for your perusal (I will post a v6 too).

David
---
commit 8b95b9cd654835eb2ff1ad24cd6de802836c4062
Author: David Howells <dhowells@redhat.com>
Date:   Wed Jun 7 14:44:34 2023 +0100

    ipv4, ipv6: 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() retur=
ned
    0) after splice had called sendmsg() with MSG_MORE set when the user d=
idn't
    set MSG_MORE.
    =

    For UDP, a pending packet will not be emitted if the socket is closed
    before it is flushed; with this change, it be flushed by ->splice_eof(=
).
    =

    For TCP, it's not clear that MSG_MORE is actually effective.
    =

    Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
    Link: https://lore.kernel.org/r/CAHk-=3Dwh=3DV579PDYvkpnTobCLGczbgxpMg=
GmmhqiTyE34Cpi5Gg@mail.gmail.com/
    Signed-off-by: David Howells <dhowells@redhat.com>
    cc: Kuniyuki Iwashima <kuniyu@amazon.com>
    cc: Eric Dumazet <edumazet@google.com>
    cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
    cc: David Ahern <dsahern@kernel.org>
    cc: "David S. Miller" <davem@davemloft.net>
    cc: Jakub Kicinski <kuba@kernel.org>
    cc: Paolo Abeni <pabeni@redhat.com>
    cc: Jens Axboe <axboe@kernel.dk>
    cc: Matthew Wilcox <willy@infradead.org>
    cc: netdev@vger.kernel.org

Notes:
    ver #6)
     - In inet_splice_eof(), use prot after deref of sk->sk_prot.
     - In udpv6_splice_eof(), use udp_v6_push_pending_frames().
     - In udpv6_splice_eof(), don't check for AF_INET.

diff --git a/include/net/inet_common.h b/include/net/inet_common.h
index 77f4b0ef5b92..a75333342c4e 100644
--- a/include/net/inet_common.h
+++ b/include/net/inet_common.h
@@ -35,6 +35,7 @@ void __inet_accept(struct socket *sock, struct socket *n=
ewsock,
 		   struct sock *newsk);
 int inet_send_prepare(struct sock *sk);
 int inet_sendmsg(struct socket *sock, struct msghdr *msg, size_t size);
+void inet_splice_eof(struct socket *sock);
 ssize_t inet_sendpage(struct socket *sock, struct page *page, int offset,
 		      size_t size, int flags);
 int inet_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 68990a8f556a..49611af31bb7 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -327,6 +327,7 @@ int tcp_sendmsg(struct sock *sk, struct msghdr *msg, s=
ize_t size);
 int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size);
 int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied=
,
 			 size_t size, struct ubuf_info *uarg);
+void tcp_splice_eof(struct socket *sock);
 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t s=
ize,
 		 int flags);
 int tcp_sendpage_locked(struct sock *sk, struct page *page, int offset,
diff --git a/include/net/udp.h b/include/net/udp.h
index 5cad44318d71..4ed0b47c5582 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -278,6 +278,7 @@ int udp_get_port(struct sock *sk, unsigned short snum,
 int udp_err(struct sk_buff *, u32);
 int udp_abort(struct sock *sk, int err);
 int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len);
+void udp_splice_eof(struct socket *sock);
 int udp_push_pending_frames(struct sock *sk);
 void udp_flush_pending_frames(struct sock *sk);
 int udp_cmsg_send(struct sock *sk, struct msghdr *msg, u16 *gso_size);
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index b5735b3551cf..fd233c4195ac 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -831,6 +831,21 @@ int inet_sendmsg(struct socket *sock, struct msghdr *=
msg, size_t size)
 }
 EXPORT_SYMBOL(inet_sendmsg);
 =

+void inet_splice_eof(struct socket *sock)
+{
+	const struct proto *prot;
+	struct sock *sk =3D sock->sk;
+
+	if (unlikely(inet_send_prepare(sk)))
+		return;
+
+	/* IPV6_ADDRFORM can change sk->sk_prot under us. */
+	prot =3D READ_ONCE(sk->sk_prot);
+	if (prot->splice_eof)
+		prot->splice_eof(sock);
+}
+EXPORT_SYMBOL_GPL(inet_splice_eof);
+
 ssize_t inet_sendpage(struct socket *sock, struct page *page, int offset,
 		      size_t size, int flags)
 {
@@ -1050,6 +1065,7 @@ const struct proto_ops inet_stream_ops =3D {
 #ifdef CONFIG_MMU
 	.mmap		   =3D tcp_mmap,
 #endif
+	.splice_eof	   =3D inet_splice_eof,
 	.sendpage	   =3D inet_sendpage,
 	.splice_read	   =3D tcp_splice_read,
 	.read_sock	   =3D tcp_read_sock,
@@ -1084,6 +1100,7 @@ const struct proto_ops inet_dgram_ops =3D {
 	.read_skb	   =3D udp_read_skb,
 	.recvmsg	   =3D inet_recvmsg,
 	.mmap		   =3D sock_no_mmap,
+	.splice_eof	   =3D inet_splice_eof,
 	.sendpage	   =3D inet_sendpage,
 	.set_peek_off	   =3D sk_set_peek_off,
 #ifdef CONFIG_COMPAT
@@ -1115,6 +1132,7 @@ static const struct proto_ops inet_sockraw_ops =3D {
 	.sendmsg	   =3D inet_sendmsg,
 	.recvmsg	   =3D inet_recvmsg,
 	.mmap		   =3D sock_no_mmap,
+	.splice_eof	   =3D inet_splice_eof,
 	.sendpage	   =3D inet_sendpage,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	   =3D inet_compat_ioctl,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 53b7751b68e1..09f03221a6f1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1371,6 +1371,22 @@ int tcp_sendmsg(struct sock *sk, struct msghdr *msg=
, size_t size)
 }
 EXPORT_SYMBOL(tcp_sendmsg);
 =

+void tcp_splice_eof(struct socket *sock)
+{
+	struct sock *sk =3D sock->sk;
+	struct tcp_sock *tp =3D tcp_sk(sk);
+	int mss_now, size_goal;
+
+	if (!tcp_write_queue_tail(sk))
+		return;
+
+	lock_sock(sk);
+	mss_now =3D tcp_send_mss(sk, &size_goal, 0);
+	tcp_push(sk, 0, mss_now, tp->nonagle, size_goal);
+	release_sock(sk);
+}
+EXPORT_SYMBOL_GPL(tcp_splice_eof);
+
 /*
  *	Handle reading urgent data. BSD has very simple semantics for
  *	this, no blocking and very strange errors 8)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 53e9ce2f05bb..84a5d557dc1a 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -3116,6 +3116,7 @@ struct proto tcp_prot =3D {
 	.keepalive		=3D tcp_set_keepalive,
 	.recvmsg		=3D tcp_recvmsg,
 	.sendmsg		=3D tcp_sendmsg,
+	.splice_eof		=3D tcp_splice_eof,
 	.sendpage		=3D tcp_sendpage,
 	.backlog_rcv		=3D tcp_v4_do_rcv,
 	.release_cb		=3D tcp_release_cb,
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index fd3dae081f3a..df5e407286d7 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1324,6 +1324,21 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg=
, size_t len)
 }
 EXPORT_SYMBOL(udp_sendmsg);
 =

+void udp_splice_eof(struct socket *sock)
+{
+	struct sock *sk =3D sock->sk;
+	struct udp_sock *up =3D udp_sk(sk);
+
+	if (!up->pending || READ_ONCE(up->corkflag))
+		return;
+
+	lock_sock(sk);
+	if (up->pending && !READ_ONCE(up->corkflag))
+		udp_push_pending_frames(sk);
+	release_sock(sk);
+}
+EXPORT_SYMBOL_GPL(udp_splice_eof);
+
 int udp_sendpage(struct sock *sk, struct page *page, int offset,
 		 size_t size, int flags)
 {
@@ -2918,6 +2933,7 @@ struct proto udp_prot =3D {
 	.getsockopt		=3D udp_getsockopt,
 	.sendmsg		=3D udp_sendmsg,
 	.recvmsg		=3D udp_recvmsg,
+	.splice_eof		=3D udp_splice_eof,
 	.sendpage		=3D udp_sendpage,
 	.release_cb		=3D ip4_datagram_release_cb,
 	.hash			=3D udp_lib_hash,
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 2bbf13216a3d..564942bee067 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -695,6 +695,7 @@ const struct proto_ops inet6_stream_ops =3D {
 #ifdef CONFIG_MMU
 	.mmap		   =3D tcp_mmap,
 #endif
+	.splice_eof	   =3D inet_splice_eof,
 	.sendpage	   =3D inet_sendpage,
 	.sendmsg_locked    =3D tcp_sendmsg_locked,
 	.sendpage_locked   =3D tcp_sendpage_locked,
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d657713d1c71..c17c8ff94b79 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -2150,6 +2150,7 @@ struct proto tcpv6_prot =3D {
 	.keepalive		=3D tcp_set_keepalive,
 	.recvmsg		=3D tcp_recvmsg,
 	.sendmsg		=3D tcp_sendmsg,
+	.splice_eof		=3D tcp_splice_eof,
 	.sendpage		=3D tcp_sendpage,
 	.backlog_rcv		=3D tcp_v6_do_rcv,
 	.release_cb		=3D tcp_release_cb,
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index e5a337e6b970..3a592dc129e9 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1653,6 +1653,20 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *m=
sg, size_t len)
 }
 EXPORT_SYMBOL(udpv6_sendmsg);
 =

+static void udpv6_splice_eof(struct socket *sock)
+{
+	struct sock *sk =3D sock->sk;
+	struct udp_sock *up =3D udp_sk(sk);
+
+	if (!up->pending || READ_ONCE(up->corkflag))
+		return;
+
+	lock_sock(sk);
+	if (up->pending && !READ_ONCE(up->corkflag))
+		udp_push_pending_frames(sk);
+	release_sock(sk);
+}
+
 void udpv6_destroy_sock(struct sock *sk)
 {
 	struct udp_sock *up =3D udp_sk(sk);
@@ -1764,6 +1778,7 @@ struct proto udpv6_prot =3D {
 	.getsockopt		=3D udpv6_getsockopt,
 	.sendmsg		=3D udpv6_sendmsg,
 	.recvmsg		=3D udpv6_recvmsg,
+	.splice_eof		=3D udpv6_splice_eof,
 	.release_cb		=3D ip6_datagram_release_cb,
 	.hash			=3D udp_lib_hash,
 	.unhash			=3D udp_lib_unhash,