Re: [PATCH v2 2/2] nvme-tcp: support specifying the congestion-control

Mingbao Sun
2022-03-09T07:32:44Z

> > @@ -1447,6 +1449,21 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl,
> > if (nctrl->opts->tos >= 0)
> > ip_sock_set_tos(queue->sock->sk, nctrl->opts->tos);
> >
> > + if (nctrl->opts->mask & NVMF_OPT_TCP_CONGESTION) {
> > + strncpy(ca_name, nctrl->opts->tcp_congestion,
> > + TCP_CA_NAME_MAX-1);
> > + optval = KERNEL_SOCKPTR(ca_name);
> > + ret = sock_common_setsockopt(queue->sock, IPPROTO_TCP,
> > + TCP_CONGESTION, optval,
> > + strlen(ca_name));
>
> This needs to use kernel_setsockopt. I also can see absolutely no
> need for the optval local variable, and I also don't really see why
> we need ca_name either - if we need to limit the length and terminate
> it (but why?) that can be done during option parsing.

Well, actually at the beginning I did use kernel_setsockopt.
But the compilation failed.

Then I found the API kernel_setsockopt disappeared from kernel v5.8.
So I use sock_common_setsockopt instead.
The birth of variable ca_name and optval is just because of the
the relevant definitions related to the prototype of
sock_common_setsockopt.

But now through thinking your comments and investigating the story of
the disappearance of kernel_setsockopt, I feel I should use
tcp_set_congestion_control instead of sock_common_setsockopt.
Just as target/tcp.c replaced kernel_setsockopt with ip_sock_set_tos.

As for the length limitation of the ca name, I will (if required) move
them into the phase of option parsing in the next version.