From: Leonardo Bras <leob...@redhat.com> If flush is called when no buffer was sent with MSG_ZEROCOPY, it currently returns 1. This return code should be used only when Linux fails to use MSG_ZEROCOPY on a lot of sendmsg().
Fix this by returning early from flush if no sendmsg(...,MSG_ZEROCOPY) was attempted. Fixes: 2bc58ffc2926 ("QIOChannelSocket: Implement io_writev zero copy flag & io_flush for CONFIG_LINUX") Signed-off-by: Leonardo Bras <leob...@redhat.com> Reviewed-by: Daniel P. Berrangé <berra...@redhat.com> Acked-by: Daniel P. Berrangé <berra...@redhat.com> Reviewed-by: Juan Quintela <quint...@redhat.com> Reviewed-by: Peter Xu <pet...@redhat.com> Message-Id: <20220711211112.18951-2-leob...@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com> --- io/channel-socket.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/io/channel-socket.c b/io/channel-socket.c index 4466bb1cd4..74a936cc1f 100644 --- a/io/channel-socket.c +++ b/io/channel-socket.c @@ -716,12 +716,18 @@ static int qio_channel_socket_flush(QIOChannel *ioc, struct cmsghdr *cm; char control[CMSG_SPACE(sizeof(*serr))]; int received; - int ret = 1; + int ret; + + if (sioc->zero_copy_queued == sioc->zero_copy_sent) { + return 0; + } msg.msg_control = control; msg.msg_controllen = sizeof(control); memset(control, 0, sizeof(control)); + ret = 1; + while (sioc->zero_copy_sent < sioc->zero_copy_queued) { received = recvmsg(sioc->fd, &msg, MSG_ERRQUEUE); if (received < 0) { -- 2.36.1