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SubjectRe: [RFC PATCH v5 13/17] vsock: enable setting SO_ZEROCOPY
On Sat, Jul 01, 2023 at 09:39:43AM +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@sberdevices.ru>
>---
> Changelog:
> v4 -> v5:
> * This patch is totally reworked. Previous version added check for
> PF_VSOCK directly to 'net/core/sock.c', thus allowing to set
> SO_ZEROCOPY for AF_VSOCK type of socket. This new version catches
> attempt to set SO_ZEROCOPY in 'af_vsock.c'. All other options
> except SO_ZEROCOPY are forwarded to generic handler. Only this
> option is processed in 'af_vsock.c'. Handling this option includes
> access to transport to check that MSG_ZEROCOPY transmission is
> supported by the current transport (if it is set, if not - transport
> will be checked during 'connect()').

Yeah, great, this is much better!

>
> net/vmw_vsock/af_vsock.c | 44 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 42 insertions(+), 2 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index da22ae0ef477..8acc77981d01 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1406,8 +1406,18 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
> goto out;
> }
>
>- if (vsock_msgzerocopy_allow(transport))
>+ if (!vsock_msgzerocopy_allow(transport)) {

Can you leave `if (vsock_msgzerocopy_allow(transport))` and just add
the else branch with this new check?

if (vsock_msgzerocopy_allow(transport)) {
...
} 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.
>+ */
>+ if (sock_flag(sk, SOCK_ZEROCOPY)) {
>+ err = -EOPNOTSUPP;
>+ goto out;
>+ }
>+ } else {
> set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
>+ }
>
> err = vsock_auto_bind(vsk);
> if (err)
>@@ -1643,7 +1653,7 @@ 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 +1676,34 @@ static int vsock_connectible_setsockopt(struct socket *sock,
>
> transport = vsk->transport;
>
>+ if (level == SOL_SOCKET) {

We could reduce the indentation here:
if (optname != SO_ZEROCOPY) {
release_sock(sk);
return sock_setsockopt(sock, level, optname, optval, optlen);
}

Then remove the next indentation.

>+ if (optname == SO_ZEROCOPY) {
>+ int zc_val;

`zerocopy` is more readable.
>+
>+ /* Use 'int' type here, because variable to
>+ * set this option usually has this type.
>+ */
>+ COPY_IN(zc_val);
>+
>+ if (zc_val < 0 || zc_val > 1) {
>+ err = -EINVAL;
>+ goto exit;
>+ }
>+
>+ if (transport && !vsock_msgzerocopy_allow(transport)) {
>+ err = -EOPNOTSUPP;
>+ goto exit;
>+ }
>+
>+ sock_valbool_flag(sk, SOCK_ZEROCOPY,
>+ zc_val ? true : false);

Why not using directly `zc_val`?
The 3rd param of sock_valbool_flag() is an int.

>+ goto exit;
>+ }
>+
>+ release_sock(sk);
>+ return sock_setsockopt(sock, level, optname, optval, optlen);
>+ }
>+
> switch (optname) {
> case SO_VM_SOCKETS_BUFFER_SIZE:
> COPY_IN(val);
>@@ -2321,6 +2359,8 @@ static int vsock_create(struct net *net, struct socket *sock,
> }
> }
>
>+ set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
>+
> vsock_insert_unbound(vsk);
>
> return 0;
>--
>2.25.1
>

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