On 13.05.2021 14:58, Stefano Garzarella wrote:
> On Sat, May 08, 2021 at 07:35:20PM +0300, Arseny Krasnov wrote:
>> This adds transport callback and it's logic for SEQPACKET dequeue.
>> Callback fetches RW packets from rx queue of socket until whole record
>> is copied(if user's buffer is full, user is not woken up). This is done
>> to not stall sender, because if we wake up user and it leaves syscall,
>> nobody will send credit update for rest of record, and sender will wait
>> for next enter of read syscall at receiver's side. So if user buffer is
>> full, we just send credit update and drop data.
>>
>> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
>> ---
>> v8 -> v9:
>> 1) Check for RW packet type is removed from loop(all packet now
>> considered RW).
>> 2) Locking in loop is fixed.
>> 3) cpu_to_le32()/le32_to_cpu() now used.
>> 4) MSG_TRUNC handling removed from transport.
>>
>> include/linux/virtio_vsock.h | 5 ++
>> net/vmw_vsock/virtio_transport_common.c | 64 +++++++++++++++++++++++++
>> 2 files changed, 69 insertions(+)
>>
>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> index dc636b727179..02acf6e9ae04 100644
>> --- a/include/linux/virtio_vsock.h
>> +++ b/include/linux/virtio_vsock.h
>> @@ -80,6 +80,11 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
>> struct msghdr *msg,
>> size_t len, int flags);
>>
>> +ssize_t
>> +virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
>> + struct msghdr *msg,
>> + int flags,
>> + bool *msg_ready);
>> s64 virtio_transport_stream_has_data(struct vsock_sock *vsk);
>> s64 virtio_transport_stream_has_space(struct vsock_sock *vsk);
>>
>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> index ad0d34d41444..f649a21dd23b 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -393,6 +393,58 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
>> return err;
>> }
>>
>> +static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>> + struct msghdr *msg,
>> + int flags,
>> + bool *msg_ready)
>> +{
>> + struct virtio_vsock_sock *vvs = vsk->trans;
>> + struct virtio_vsock_pkt *pkt;
>> + int err = 0;
>> + size_t user_buf_len = msg->msg_iter.count;
>> +
>> + *msg_ready = false;
>> + spin_lock_bh(&vvs->rx_lock);
>> +
>> + while (!*msg_ready && !list_empty(&vvs->rx_queue) && err >= 0) {
>> + size_t bytes_to_copy;
>> + size_t pkt_len;
>> +
>> + pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list);
>> + pkt_len = (size_t)le32_to_cpu(pkt->hdr.len);
>> + bytes_to_copy = min(user_buf_len, pkt_len);
>> +
>> + if (bytes_to_copy) {
>> + /* sk_lock is held by caller so no one else can dequeue.
>> + * Unlock rx_lock since memcpy_to_msg() may sleep.
>> + */
>> + spin_unlock_bh(&vvs->rx_lock);
>> +
>> + if (memcpy_to_msg(msg, pkt->buf, bytes_to_copy))
>> {
>> + err = -EINVAL;
>> + } else {
>> + err += pkt_len;
> If `bytes_to_copy == 0` we are not increasing the real length.
>
> Anyway is a bit confusing increase a variable called `err`, I think is
> better to have another variable to store this information that we return
> if there aren't errors.
Ack
>
>
