netdev - Re: [PATCH net-next v3 3/4] vsock: Move lingering logic to af

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Message-ID: <fa71ef5e-7603-4241-bfd3-7aa7b5ea8945@rbox.co>
Date: Wed, 30 Apr 2025 12:33:26 +0200
From: Michal Luczaj <mhal@...x.co>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
 <eperezma@...hat.com>, Stefan Hajnoczi <stefanha@...hat.com>,
 virtualization@...ts.linux.dev, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH net-next v3 3/4] vsock: Move lingering logic to af_vsock
 core

On 4/30/25 11:36, Stefano Garzarella wrote:
> On Wed, Apr 30, 2025 at 11:10:29AM +0200, Michal Luczaj wrote:
>> Lingering should be transport-independent in the long run. In preparation
>> for supporting other transports, as well the linger on shutdown(), move
>> code to core.
>>
>> Guard against an unimplemented vsock_transport::unsent_bytes() callback.
>>
>> Suggested-by: Stefano Garzarella <sgarzare@...hat.com>
>> Signed-off-by: Michal Luczaj <mhal@...x.co>
>> ---
>> include/net/af_vsock.h                  |  1 +
>> net/vmw_vsock/af_vsock.c                | 25 +++++++++++++++++++++++++
>> net/vmw_vsock/virtio_transport_common.c | 23 +----------------------
>> 3 files changed, 27 insertions(+), 22 deletions(-)
>>
>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>> index 9e85424c834353d016a527070dd62e15ff3bfce1..bd8b88d70423051dd05fc445fe37971af631ba03 100644
>> --- a/include/net/af_vsock.h
>> +++ b/include/net/af_vsock.h
>> @@ -221,6 +221,7 @@ void vsock_for_each_connected_socket(struct vsock_transport *transport,
>> 				     void (*fn)(struct sock *sk));
>> int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk);
>> bool vsock_find_cid(unsigned int cid);
>> +void vsock_linger(struct sock *sk, long timeout);
>>
>> /**** TAP ****/
>>
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index fc6afbc8d6806a4d98c66abc3af4bd139c583b08..946b37de679a0e68b84cd982a3af2a959c60ee57 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -1013,6 +1013,31 @@ static int vsock_getname(struct socket *sock,
>> 	return err;
>> }
>>
>> +void vsock_linger(struct sock *sk, long timeout)
>> +{
>> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>> +	ssize_t (*unsent)(struct vsock_sock *vsk);
>> +	struct vsock_sock *vsk = vsock_sk(sk);
>> +
>> +	if (!timeout)
>> +		return;
>> +
>> +	/* unsent_bytes() may be unimplemented. */
>> +	unsent = vsk->transport->unsent_bytes;
>> +	if (!unsent)
>> +		return;
>> +
>> +	add_wait_queue(sk_sleep(sk), &wait);
>> +
>> +	do {
>> +		if (sk_wait_event(sk, &timeout, unsent(vsk) == 0, &wait))
>> +			break;
>> +	} while (!signal_pending(current) && timeout);
>> +
>> +	remove_wait_queue(sk_sleep(sk), &wait);
>> +}
>> +EXPORT_SYMBOL_GPL(vsock_linger);
>> +
>> static int vsock_shutdown(struct socket *sock, int mode)
>> {
>> 	int err;
>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> index 4425802c5d718f65aaea425ea35886ad64e2fe6e..9230b8358ef2ac1f6e72a5961bae39f9093c8884 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -1192,27 +1192,6 @@ static void virtio_transport_remove_sock(struct vsock_sock *vsk)
>> 	vsock_remove_sock(vsk);
>> }
>>
>> -static void virtio_transport_wait_close(struct sock *sk, long timeout)
>> -{
>> -	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>> -	ssize_t (*unsent)(struct vsock_sock *vsk);
>> -	struct vsock_sock *vsk = vsock_sk(sk);
>> -
>> -	if (!timeout)
>> -		return;
>> -
>> -	unsent = vsk->transport->unsent_bytes;
>> -
>> -	add_wait_queue(sk_sleep(sk), &wait);
>> -
>> -	do {
>> -		if (sk_wait_event(sk, &timeout, unsent(vsk) == 0, &wait))
>> -			break;
>> -	} while (!signal_pending(current) && timeout);
>> -
>> -	remove_wait_queue(sk_sleep(sk), &wait);
>> -}
>> -
>> static void virtio_transport_cancel_close_work(struct vsock_sock *vsk,
>> 					       bool cancel_timeout)
>> {
>> @@ -1283,7 +1262,7 @@ static bool virtio_transport_close(struct vsock_sock *vsk)
>> 		(void)virtio_transport_shutdown(vsk, SHUTDOWN_MASK);
>>
>> 	if (sock_flag(sk, SOCK_LINGER) && !(current->flags & PF_EXITING))
>> -		virtio_transport_wait_close(sk, sk->sk_lingertime);
>> +		vsock_linger(sk, sk->sk_lingertime);
> 
> Ah, I'd also move the check in that function, I mean:
> 
> void vsock_linger(struct sock *sk) {
> 	...
> 	if (!sock_flag(sk, SOCK_LINGER) || (current->flags & PF_EXITING))
> 		return;
> 
> 	...
> }

One note: if we ever use vsock_linger() in vsock_shutdown(), the PF_EXITING
condition would be unnecessary checked for that caller, right?

> Or, if we move the call to vsock_linger() in __vsock_release(), we can
> do the check there.
> 
> Thanks,
> Stefano
> 
>>
>> 	if (sock_flag(sk, SOCK_DONE)) {
>> 		return true;
>>
>> -- 
>> 2.49.0
>>
>>