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Message-ID: <baa11cfd-2f12-fea0-3f5c-015f5d682334@kaspersky.com>
Date: Tue, 16 Feb 2021 09:58:32 +0300
From: Arseny Krasnov <arseny.krasnov@...persky.com>
To: Jorgen Hansen <jhansen@...are.com>
CC: Stefan Hajnoczi <stefanha@...hat.com>,
Stefano Garzarella <sgarzare@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Colin Ian King <colin.king@...onical.com>,
Andra Paraschiv <andraprs@...zon.com>,
Alexander Popov <alex.popov@...ux.com>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"stsp2@...dex.ru" <stsp2@...dex.ru>,
"oxffffaa@...il.com" <oxffffaa@...il.com>
Subject: Re: [RFC PATCH v4 02/17] af_vsock: separate wait data loop
On 11.02.2021 18:11, Jorgen Hansen wrote:
>> On 7 Feb 2021, at 16:14, Arseny Krasnov <arseny.krasnov@...persky.com> wrote:
>>
>> This moves wait loop for data to dedicated function, because later
>> it will be used by SEQPACKET data receive loop.
>>
>> Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>> ---
>> net/vmw_vsock/af_vsock.c | 158 +++++++++++++++++++++------------------
>> 1 file changed, 86 insertions(+), 72 deletions(-)
>>
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index f4fabec50650..38927695786f 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -1833,6 +1833,71 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
>> return err;
>> }
>>
>> +static int vsock_wait_data(struct sock *sk, struct wait_queue_entry *wait,
>> + long timeout,
>> + struct vsock_transport_recv_notify_data *recv_data,
>> + size_t target)
>> +{
>> + const struct vsock_transport *transport;
>> + struct vsock_sock *vsk;
>> + s64 data;
>> + int err;
>> +
>> + vsk = vsock_sk(sk);
>> + err = 0;
>> + transport = vsk->transport;
>> + prepare_to_wait(sk_sleep(sk), wait, TASK_INTERRUPTIBLE);
>> +
>> + while ((data = vsock_stream_has_data(vsk)) == 0) {
>> + if (sk->sk_err != 0 ||
>> + (sk->sk_shutdown & RCV_SHUTDOWN) ||
>> + (vsk->peer_shutdown & SEND_SHUTDOWN)) {
>> + goto out;
>> + }
>> +
>> + /* Don't wait for non-blocking sockets. */
>> + if (timeout == 0) {
>> + err = -EAGAIN;
>> + goto out;
>> + }
>> +
>> + if (recv_data) {
>> + err = transport->notify_recv_pre_block(vsk, target, recv_data);
>> + if (err < 0)
>> + goto out;
>> + }
>> +
>> + release_sock(sk);
>> + timeout = schedule_timeout(timeout);
>> + lock_sock(sk);
>> +
>> + if (signal_pending(current)) {
>> + err = sock_intr_errno(timeout);
>> + goto out;
>> + } else if (timeout == 0) {
>> + err = -EAGAIN;
>> + goto out;
>> + }
>> + }
>> +
>> + finish_wait(sk_sleep(sk), wait);
>> +
>> + /* Invalid queue pair content. XXX This should
>> + * be changed to a connection reset in a later
>> + * change.
>> + */
> Since you are here, could you update this comment to something like:
>
> /* Internal transport error when checking for available
> * data. XXX This should be changed to a connection
> * reset in a later change.
> */
>
>> + if (data < 0)
>> + return -ENOMEM;
>> +
>> + /* Have some data, return. */
>> + if (data)
>> + return data;
>> +
>> +out:
>> + finish_wait(sk_sleep(sk), wait);
>> + return err;
>> +}
> I agree with Stefanos suggestion to get rid of the out: part and just have the single finish_wait().
>
>> +
>> static int
>> vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>> int flags)
>> @@ -1912,85 +1977,34 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>
>>
>> while (1) {
>> - s64 ready;
>> + ssize_t read;
>>
>> - prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
>> - ready = vsock_stream_has_data(vsk);
>> -
>> - if (ready == 0) {
>> - if (sk->sk_err != 0 ||
>> - (sk->sk_shutdown & RCV_SHUTDOWN) ||
>> - (vsk->peer_shutdown & SEND_SHUTDOWN)) {
>> - finish_wait(sk_sleep(sk), &wait);
>> - break;
>> - }
>> - /* Don't wait for non-blocking sockets. */
>> - if (timeout == 0) {
>> - err = -EAGAIN;
>> - finish_wait(sk_sleep(sk), &wait);
>> - break;
>> - }
>> -
>> - err = transport->notify_recv_pre_block(
>> - vsk, target, &recv_data);
>> - if (err < 0) {
>> - finish_wait(sk_sleep(sk), &wait);
>> - break;
>> - }
>> - release_sock(sk);
>> - timeout = schedule_timeout(timeout);
>> - lock_sock(sk);
>> -
>> - if (signal_pending(current)) {
>> - err = sock_intr_errno(timeout);
>> - finish_wait(sk_sleep(sk), &wait);
>> - break;
>> - } else if (timeout == 0) {
>> - err = -EAGAIN;
>> - finish_wait(sk_sleep(sk), &wait);
>> - break;
>> - }
>> - } else {
>> - ssize_t read;
>> + err = vsock_wait_data(sk, &wait, timeout, &recv_data, target);
>> + if (err <= 0)
>> + break;
> There is a small change in the behaviour here if vsock_stream_has_data(vsk)
> returned something < 0. Since you just do a break, the err value can be updated
> if there is an sk->sk_err, a receive shutdown has been performed or data has
> already been copied. That should be ok, though.
May be i can add the following 'if' after while (1) loop:
There was:
if (sk->sk_err)
err = -sk->sk->sk_err;
else if (sk->sk_shutdown & RCV_SHUTDOWN)
err = 0;
if (copied > 0)
err = copied;
Will be:
if (err == 0) {
if (sk->sk_err)
err = -sk->sk->sk_err;
else if (sk->sk_shutdown & RCV_SHUTDOWN)
err = 0;
if (copied > 0)
err = copied;
}
E.g. update 'err' only if it is clear. Don't touch otherwise
>
>> - finish_wait(sk_sleep(sk), &wait);
>> -
>> - if (ready < 0) {
>> - /* Invalid queue pair content. XXX This should
>> - * be changed to a connection reset in a later
>> - * change.
>> - */
>> -
>> - err = -ENOMEM;
>> - goto out;
>> - }
>> -
>> - err = transport->notify_recv_pre_dequeue(
>> - vsk, target, &recv_data);
>> - if (err < 0)
>> - break;
>> + err = transport->notify_recv_pre_dequeue(vsk, target,
>> + &recv_data);
>> + if (err < 0)
>> + break;
>>
>> - read = transport->stream_dequeue(
>> - vsk, msg,
>> - len - copied, flags);
>> - if (read < 0) {
>> - err = -ENOMEM;
>> - break;
>> - }
>> + read = transport->stream_dequeue(vsk, msg, len - copied, flags);
>> + if (read < 0) {
>> + err = -ENOMEM;
>> + break;
>> + }
>>
>> - copied += read;
>> + copied += read;
>>
>> - err = transport->notify_recv_post_dequeue(
>> - vsk, target, read,
>> - !(flags & MSG_PEEK), &recv_data);
>> - if (err < 0)
>> - goto out;
>> + err = transport->notify_recv_post_dequeue(vsk, target, read,
>> + !(flags & MSG_PEEK), &recv_data);
>> + if (err < 0)
>> + goto out;
>>
>> - if (read >= target || flags & MSG_PEEK)
>> - break;
>> + if (read >= target || flags & MSG_PEEK)
>> + break;
>>
>> - target -= read;
>> - }
>> + target -= read;
>> }
>>
>> if (sk->sk_err)
>> --
>> 2.25.1
>>
>
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