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Tsirkin" To: Arseniy Krasnov Cc: Stefan Hajnoczi , Stefano Garzarella , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jason Wang , Bobby Eshleman , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@sberdevices.ru, oxffffaa@gmail.com Subject: Re: [PATCH net-next v5 2/3] virtio/vsock: send credit update during setting SO_RCVLOWAT Message-ID: <20231130084044-mutt-send-email-mst@kernel.org> References: <20231130130840.253733-1-avkrasnov@salutedevices.com> <20231130130840.253733-3-avkrasnov@salutedevices.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20231130130840.253733-3-avkrasnov@salutedevices.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Nov 30, 2023 at 04:08:39PM +0300, Arseniy Krasnov wrote: > Send credit update message when SO_RCVLOWAT is updated and it is bigger > than number of bytes in rx queue. It is needed, because 'poll()' will > wait until number of bytes in rx queue will be not smaller than > SO_RCVLOWAT, so kick sender to send more data. Otherwise mutual hungup > for tx/rx is possible: sender waits for free space and receiver is > waiting data in 'poll()'. > > Signed-off-by: Arseniy Krasnov > --- > Changelog: > v1 -> v2: > * Update commit message by removing 'This patch adds XXX' manner. > * Do not initialize 'send_update' variable - set it directly during > first usage. > v3 -> v4: > * Fit comment in 'virtio_transport_notify_set_rcvlowat()' to 80 chars. > v4 -> v5: > * Do not change callbacks order in transport structures. > > drivers/vhost/vsock.c | 1 + > include/linux/virtio_vsock.h | 1 + > net/vmw_vsock/virtio_transport.c | 1 + > net/vmw_vsock/virtio_transport_common.c | 27 +++++++++++++++++++++++++ > net/vmw_vsock/vsock_loopback.c | 1 + > 5 files changed, 31 insertions(+) > > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c > index f75731396b7e..4146f80db8ac 100644 > --- a/drivers/vhost/vsock.c > +++ b/drivers/vhost/vsock.c > @@ -451,6 +451,7 @@ static struct virtio_transport vhost_transport = { > .notify_buffer_size = virtio_transport_notify_buffer_size, > > .read_skb = virtio_transport_read_skb, > + .notify_set_rcvlowat = virtio_transport_notify_set_rcvlowat > }, > > .send_pkt = vhost_transport_send_pkt, > diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h > index ebb3ce63d64d..c82089dee0c8 100644 > --- a/include/linux/virtio_vsock.h > +++ b/include/linux/virtio_vsock.h > @@ -256,4 +256,5 @@ void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit); > void virtio_transport_deliver_tap_pkt(struct sk_buff *skb); > int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *list); > int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t read_actor); > +int virtio_transport_notify_set_rcvlowat(struct vsock_sock *vsk, int val); > #endif /* _LINUX_VIRTIO_VSOCK_H */ > diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c > index af5bab1acee1..8007593a3a93 100644 > --- a/net/vmw_vsock/virtio_transport.c > +++ b/net/vmw_vsock/virtio_transport.c > @@ -539,6 +539,7 @@ static struct virtio_transport virtio_transport = { > .notify_buffer_size = virtio_transport_notify_buffer_size, > > .read_skb = virtio_transport_read_skb, > + .notify_set_rcvlowat = virtio_transport_notify_set_rcvlowat > }, > > .send_pkt = virtio_transport_send_pkt, > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > index f6dc896bf44c..1cb556ad4597 100644 > --- a/net/vmw_vsock/virtio_transport_common.c > +++ b/net/vmw_vsock/virtio_transport_common.c > @@ -1684,6 +1684,33 @@ int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_acto > } > EXPORT_SYMBOL_GPL(virtio_transport_read_skb); > > +int virtio_transport_notify_set_rcvlowat(struct vsock_sock *vsk, int val) > +{ > + struct virtio_vsock_sock *vvs = vsk->trans; > + bool send_update; > + > + spin_lock_bh(&vvs->rx_lock); > + > + /* If number of available bytes is less than new SO_RCVLOWAT value, > + * kick sender to send more data, because sender may sleep in its > + * 'send()' syscall waiting for enough space at our side. > + */ > + send_update = vvs->rx_bytes < val; > + > + spin_unlock_bh(&vvs->rx_lock); > + > + if (send_update) { > + int err; > + > + err = virtio_transport_send_credit_update(vsk); > + if (err < 0) > + return err; > + } > + > + return 0; > +} I find it strange that this will send a credit update even if nothing changed since this was called previously. I'm not sure whether this is a problem protocol-wise, but it certainly was not envisioned when the protocol was built. WDYT? > +EXPORT_SYMBOL_GPL(virtio_transport_notify_set_rcvlowat); > + > MODULE_LICENSE("GPL v2"); > MODULE_AUTHOR("Asias He"); > MODULE_DESCRIPTION("common code for virtio vsock"); > diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c > index 048640167411..9f4b814fbbc7 100644 > --- a/net/vmw_vsock/vsock_loopback.c > +++ b/net/vmw_vsock/vsock_loopback.c > @@ -98,6 +98,7 @@ static struct virtio_transport loopback_transport = { > .notify_buffer_size = virtio_transport_notify_buffer_size, > > .read_skb = virtio_transport_read_skb, > + .notify_set_rcvlowat = virtio_transport_notify_set_rcvlowat > }, > > .send_pkt = vsock_loopback_send_pkt, > -- > 2.25.1