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virtio/vsock: fix logic which reduces credit update messages

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[ Upstream commit 93b8088766 ]

Add one more condition for sending credit update during dequeue from
stream socket: when number of bytes in the rx queue is smaller than
SO_RCVLOWAT value of the socket. This is actual for non-default value
of SO_RCVLOWAT (e.g. not 1) - idea is to "kick" peer to continue data
transmission, because we need at least SO_RCVLOWAT bytes in our rx
queue to wake up user for reading data (in corner case it is also
possible to stuck both tx and rx sides, this is why 'Fixes' is used).

Fixes: b89d882dc9 ("vsock/virtio: reduce credit update messages")
Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Arseniy Krasnov 2023-12-14 15:52:28 +03:00 committed by Greg Kroah-Hartman
parent 30ae0c6631
commit ad43344ab4
1 changed files with 10 additions and 3 deletions
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13
net/vmw_vsock/virtio_transport_common.c
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@ -340,6 +340,8 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
struct virtio_vsock_pkt *pkt;
size_t bytes, total = 0;
u32 free_space;
u32 fwd_cnt_delta;
bool low_rx_bytes;
int err = -EFAULT;
spin_lock_bh(&vvs->rx_lock);
@ -371,7 +373,10 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
}
}
free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs->last_fwd_cnt);
fwd_cnt_delta = vvs->fwd_cnt - vvs->last_fwd_cnt;
free_space = vvs->buf_alloc - fwd_cnt_delta;
low_rx_bytes = (vvs->rx_bytes <
sock_rcvlowat(sk_vsock(vsk), 0, INT_MAX));
spin_unlock_bh(&vvs->rx_lock);
@ -381,9 +386,11 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
* too high causes extra messages. Too low causes transmitter
* stalls. As stalls are in theory more expensive than extra
* messages, we set the limit to a high value. TODO: experiment
* with different values.
* with different values. Also send credit update message when
* number of bytes in rx queue is not enough to wake up reader.
*/
if (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
if (fwd_cnt_delta &&
(free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE || low_rx_bytes)) {
virtio_transport_send_credit_update(vsk,
VIRTIO_VSOCK_TYPE_STREAM,
NULL);