linux-kernel - Re: [PATCH net-next v1 08/12] vsock: enable setting SO

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Message-ID: <ynuctxau4ta4pk763ut7gfdaqzcuyve7uf2a2iltyspravs5uf@xrtqtbhuuvwq>
Date:   Tue, 26 Sep 2023 14:56:21 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <avkrasnov@...utedevices.com>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Bobby Eshleman <bobby.eshleman@...edance.com>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...rdevices.ru, oxffffaa@...il.com
Subject: Re: [PATCH net-next v1 08/12] vsock: enable setting SO_ZEROCOPY

On Fri, Sep 22, 2023 at 08:24:24AM +0300, Arseniy Krasnov wrote:
>For AF_VSOCK, zerocopy tx mode depends on transport, so this option must
>be set in AF_VSOCK implementation where transport is accessible (if
>transport is not set during setting SO_ZEROCOPY: for example socket is
>not connected, then SO_ZEROCOPY will be enabled, but once transport will
>be assigned, support of this type of transmission will be checked).
>
>To handle SO_ZEROCOPY, AF_VSOCK implementation uses SOCK_CUSTOM_SOCKOPT
>bit, thus handling SOL_SOCKET option operations, but all of them except
>SO_ZEROCOPY will be forwarded to the generic handler by calling
>'sock_setsockopt()'.
>
>Signed-off-by: Arseniy Krasnov <avkrasnov@...utedevices.com>
>---
> Changelog:
> v5(big patchset) -> v1:
>  * Compact 'if' conditions.
>  * Rename 'zc_val' to 'zerocopy'.
>  * Use 'zerocopy' value directly in 'sock_valbool_flag()', without
>    ?: operator.
>  * Set 'SOCK_CUSTOM_SOCKOPT' bit for connectible sockets only, as
>    suggested by Bobby Eshleman <bobbyeshleman@...il.com>.
>
> net/vmw_vsock/af_vsock.c | 46 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 44 insertions(+), 2 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 482300eb88e0..c05a42e02a17 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1406,8 +1406,16 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
> 			goto out;
> 		}
>
>-		if (vsock_msgzerocopy_allow(transport))
>+		if (vsock_msgzerocopy_allow(transport)) {
> 			set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
>+		} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
>+			/* If this option was set before 'connect()',
>+			 * when transport was unknown, check that this
>+			 * feature is supported here.
>+			 */
>+			err = -EOPNOTSUPP;
>+			goto out;
>+		}
>
> 		err = vsock_auto_bind(vsk);
> 		if (err)
>@@ -1643,7 +1651,7 @@ static int vsock_connectible_setsockopt(struct socket *sock,
> 	const struct vsock_transport *transport;
> 	u64 val;
>
>-	if (level != AF_VSOCK)
>+	if (level != AF_VSOCK && level != SOL_SOCKET)
> 		return -ENOPROTOOPT;
>
> #define COPY_IN(_v)                                       \
>@@ -1666,6 +1674,34 @@ static int vsock_connectible_setsockopt(struct socket *sock,
>
> 	transport = vsk->transport;
>
>+	if (level == SOL_SOCKET) {
>+		int zerocopy;
>+
>+		if (optname != SO_ZEROCOPY) {
>+			release_sock(sk);
>+			return sock_setsockopt(sock, level, optname, optval, optlen);
>+		}
>+
>+		/* Use 'int' type here, because variable to
>+		 * set this option usually has this type.
>+		 */
>+		COPY_IN(zerocopy);
>+
>+		if (zerocopy < 0 || zerocopy > 1) {
>+			err = -EINVAL;
>+			goto exit;
>+		}
>+
>+		if (transport && !vsock_msgzerocopy_allow(transport)) {
>+			err = -EOPNOTSUPP;
>+			goto exit;
>+		}
>+
>+		sock_valbool_flag(sk, SOCK_ZEROCOPY,
>+				  zerocopy);

it's not necessary to wrap this call.

>+		goto exit;
>+	}
>+
> 	switch (optname) {
> 	case SO_VM_SOCKETS_BUFFER_SIZE:
> 		COPY_IN(val);
>@@ -2322,6 +2358,12 @@ static int vsock_create(struct net *net, struct socket *sock,
> 		}
> 	}
>
>+	/* SOCK_DGRAM doesn't have 'setsockopt' callback set in its
>+	 * proto_ops, so there is no handler for custom logic.
>+	 */
>+	if (sock_type_connectible(sock->type))
>+		set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
>+
> 	vsock_insert_unbound(vsk);
>
> 	return 0;
>-- 
>2.25.1
>