linux-kernel - Re: [PATCH net-next 3/3] vsock/virtio: remove redundant `copy

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Date:   Fri, 18 Jun 2021 17:55:00 +0300
From:   Arseny Krasnov <arseny.krasnov@...persky.com>
To:     Stefano Garzarella <sgarzare@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 3/3] vsock/virtio: remove redundant `copy_failed`
 variable


On 18.06.2021 16:35, Stefano Garzarella wrote:
> When memcpy_to_msg() fails in virtio_transport_seqpacket_do_dequeue(),
> we already set `dequeued_len` with the negative error value returned
> by memcpy_to_msg().
>
> So we can directly check `dequeued_len` value instead of using a
> dedicated flag variable to skip the copy path for the rest of
> fragments.
>
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
>  net/vmw_vsock/virtio_transport_common.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index 23704a6bc437..f014ccfdd9c2 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -413,7 +413,6 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>  	struct virtio_vsock_pkt *pkt;
>  	int dequeued_len = 0;
>  	size_t user_buf_len = msg_data_left(msg);
> -	bool copy_failed = false;
>  	bool msg_ready = false;
>  
>  	spin_lock_bh(&vvs->rx_lock);
> @@ -426,7 +425,7 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>  	while (!msg_ready) {
>  		pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list);
>  
> -		if (!copy_failed) {
> +		if (dequeued_len >= 0) {
>  			size_t pkt_len;
>  			size_t bytes_to_copy;
>  
> @@ -443,11 +442,9 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>  
>  				err = memcpy_to_msg(msg, pkt->buf, bytes_to_copy);
>  				if (err) {
> -					/* Copy of message failed, set flag to skip
> -					 * copy path for rest of fragments. Rest of
> +					/* Copy of message failed. Rest of
>  					 * fragments will be freed without copy.
>  					 */
> -					copy_failed = true;
>  					dequeued_len = err;
>  				} else {
>  					user_buf_len -= bytes_to_copy;
LGTM