linux-kernel - Re: [PATCH net-next v4 2/3] vsock: Move lingering logic to af

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Message-ID: <6a818cc6-f26c-417b-ad06-0686b698b2fe@rbox.co>
Date: Wed, 7 May 2025 00:47:08 +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 v4 2/3] vsock: Move lingering logic to af_vsock
 core

On 5/6/25 11:53, Stefano Garzarella wrote:
> On Thu, May 01, 2025 at 10:05:23AM +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.
>>
>> Generalize by querying vsock_transport::unsent_bytes(), guard against the
>> callback being unimplemented. Do not pass sk_lingertime explicitly. Pull
>> SOCK_LINGER check into vsock_linger().
>>
>> Flatten the function. Remove the nested block by inverting the condition:
>> return early on !timeout.
>>
>> 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                | 30 ++++++++++++++++++++++++++++++
>> net/vmw_vsock/virtio_transport_common.c | 23 ++---------------------
>> 3 files changed, 33 insertions(+), 21 deletions(-)
>>
>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>> index 9e85424c834353d016a527070dd62e15ff3bfce1..d56e6e135158939087d060dfcf65d3fdaea53bf3 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);
>>
>> /**** TAP ****/
>>
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index fc6afbc8d6806a4d98c66abc3af4bd139c583b08..a31ad6b141cd38d1806df4b5d417924bb8607e32 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -1013,6 +1013,36 @@ static int vsock_getname(struct socket *sock,
>> 	return err;
>> }
>>
>> +void vsock_linger(struct sock *sk)
>> +{
>> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>> +	ssize_t (*unsent)(struct vsock_sock *vsk);
>> +	struct vsock_sock *vsk = vsock_sk(sk);
>> +	long timeout;
>> +
>> +	if (!sock_flag(sk, SOCK_LINGER))
>> +		return;
>> +
>> +	timeout = sk->sk_lingertime;
>> +	if (!timeout)
>> +		return;
>> +
>> +	/* unsent_bytes() may be unimplemented. */
> 
> This comment IMO should be enriched, as it is now it doesn't add much to 
> the code. I'm thinking on something like this:
>      Transports must implement `unsent_bytes` if they want to support
>      SOCK_LINGER through `vsock_linger()` since we use it to check when
>      the socket can be closed.

OK, will do.

Thanks,
Michal