From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: Paolo Abeni <pabeni@redhat•com>, netdev@vger•kernel.org
Cc: "David S. Miller" <davem@davemloft•net>,
Jakub Kicinski <kuba@kernel•org>
Subject: Re: [RFC PATCH 1/3] veth: implement support for set_channel ethtool op
Date: Fri, 09 Jul 2021 17:23:00 +0200 [thread overview]
Message-ID: <87lf6feckr.fsf@toke.dk> (raw)
In-Reply-To: <9c451d25fb36bc82e602bb93e384b262be743fbf.camel@redhat.com>
Paolo Abeni <pabeni@redhat•com> writes:
> On Fri, 2021-07-09 at 12:49 +0200, Paolo Abeni wrote:
>> On Fri, 2021-07-09 at 12:15 +0200, Toke Høiland-Jørgensen wrote:
>> > > + if (netif_running(dev))
>> > > + veth_close(dev);
>> > > +
>> > > + priv->num_tx_queues = ch->tx_count;
>> > > + priv->num_rx_queues = ch->rx_count;
>> >
>> > Why can't just you use netif_set_real_num_*_queues() here directly (and
>> > get rid of the priv members as above)?
>>
>> Uhm... I haven't thought about it. Let me try ;)
>
> Here there is a possible problem: if the latter
> netif_set_real_num_*_queues() fails, we should not change the current
> configuration, so we should revert the
> first netif_set_real_num_*_queues() change.
>
> Even that additional revert operation could fail. If/when that happen
> set_channel() will leave the device in a different state from both the
> old one and the new one, possibly with an XDP-incompatible number of
> queues.
>
> Keeping the netif_set_real_num_*_queues() calls in veth_open() avoid
> the above issue: if the queue creation is problematic, the device will
> stay down.
>
> I think the additional fields are worthy, WDYT?
Hmm, wouldn't the right thing to do be to back out the change and return
an error to userspace? Something like:
+ if (netif_running(dev))
+ veth_close(dev);
+
+ old_rx_queues = dev->real_num_rx_queues;
+ err = netif_set_real_num_rx_queues(dev, ch->rx_count);
+ if (err)
+ return err;
+
+ err = netif_set_real_num_tx_queues(dev, ch->tx_count);
+ if (err) {
+ netif_set_real_num_rx_queues(dev, old_rx_queues);
+ return err;
+ }
+
+ if (netif_running(dev))
+ veth_open(dev);
+ return 0;
(also, shouldn't the result of veth_open() be returned? bit weird if you
don't get an error but the device stays down...)
-Toke
next prev parent reply other threads:[~2021-07-09 15:23 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 9:39 [RFC PATCH 0/3] veth: more flexible channels number configuration Paolo Abeni
2021-07-09 9:39 ` [RFC PATCH 1/3] veth: implement support for set_channel ethtool op Paolo Abeni
2021-07-09 10:15 ` Toke Høiland-Jørgensen
2021-07-09 10:49 ` Paolo Abeni
2021-07-09 11:36 ` Toke Høiland-Jørgensen
2021-07-09 14:38 ` Paolo Abeni
2021-07-09 15:23 ` Toke Høiland-Jørgensen [this message]
2021-07-09 16:35 ` Paolo Abeni
2021-07-09 19:56 ` Jakub Kicinski
2021-07-09 19:54 ` Jakub Kicinski
2021-07-12 1:44 ` David Ahern
2021-07-12 10:45 ` Paolo Abeni
2021-07-12 15:23 ` Jakub Kicinski
2021-07-09 9:39 ` [RFC PATCH 2/3] veth: make queues nr configurable via kernel module params Paolo Abeni
2021-07-09 10:24 ` Toke Høiland-Jørgensen
2021-07-09 15:33 ` Paolo Abeni
2021-07-09 16:12 ` Toke Høiland-Jørgensen
2021-07-09 9:39 ` [RFC PATCH 3/3] selftests: net: veth: add tests for set_channel Paolo Abeni
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