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

[Michal Luczaj <mhal@rbox.co>]

On 4/30/25 12:37, Stefano Garzarella wrote:
> On Wed, 30 Apr 2025 at 12:33, Michal Luczaj <mhal@rbox.co> wrote:
>>
>> 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@redhat.com>
>>>> Signed-off-by: Michal Luczaj <mhal@rbox.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?
> 
> Right, for shutdown it should always be false, so maybe better to keep
> the check in the caller.

Or split it? Check `!sock_flag(sk, SOCK_LINGER) || !timeout` in
vsock_linger() and defer `!(flags & PF_EXITING)` to whoever does the socket
release?