netdev - RE: [PATCH net-next] Name NICs based on vmbus offer and enable async probe by default

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Date:   Wed, 10 Jul 2019 01:03:54 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
CC:     "sashal@...nel.org" <sashal@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>, vkuznets <vkuznets@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next] Name NICs based on vmbus offer and enable async
 probe by default



> -----Original Message-----
> From: Stephen Hemminger <stephen@...workplumber.org>
> Sent: Tuesday, July 9, 2019 7:47 PM
> To: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: sashal@...nel.org; linux-hyperv@...r.kernel.org;
> netdev@...r.kernel.org; KY Srinivasan <kys@...rosoft.com>; Stephen
> Hemminger <sthemmin@...rosoft.com>; olaf@...fle.de; vkuznets
> <vkuznets@...hat.com>; davem@...emloft.net; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH net-next] Name NICs based on vmbus offer and enable
> async probe by default
> 
> On Tue, 9 Jul 2019 22:56:30 +0000
> Haiyang Zhang <haiyangz@...rosoft.com> wrote:
> 
> > -				VRSS_CHANNEL_MAX);
> > +	if (probe_type == PROBE_PREFER_ASYNCHRONOUS) {
> > +		snprintf(name, IFNAMSIZ, "eth%d", dev->channel->dev_num);
> 
> What about PCI passthrough or VF devices that are also being probed and
> consuming the ethN names.  Won't there be a collision?

VF usually shows up a few seconds later than the synthetic NIC. Faster probing
will reduce the probability of collision.
Even if a collision happens, the code below will re-register the NIC with "eth%d":
+	if (ret == -EEXIST) {
+		pr_info("NIC name %s exists, request another name.\n",
+			net->name);
+		strlcpy(net->name, "eth%d", IFNAMSIZ);
+		ret = register_netdevice(net);
+	}

Thanks,
- Haiyang