RE: [PATCH net-next, 1/3] Drivers: hv: vmbus: Add a dev_num variable based on channel offer sequence

[Haiyang Zhang]

> -----Original Message-----
> From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
> Sent: Saturday, December 28, 2019 7:20 PM
> To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Cc: sashal@xxxxxxxxxx; linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx;
> KY Srinivasan <kys@xxxxxxxxxxxxx>; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; olaf@xxxxxxxxx; vkuznets
> <vkuznets@xxxxxxxxxx>; davem@xxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH net-next, 1/3] Drivers: hv: vmbus: Add a dev_num variable
> based on channel offer sequence
> 
> On Sat, 28 Dec 2019 15:46:31 -0800
> Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> wrote:
> 
> > +
> > +next:
> > +	found = false;
> > +
> > +	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
> > +		if (i == channel->dev_num &&
> > +		    guid_equal(&channel->offermsg.offer.if_type,
> > +			       &newchannel->offermsg.offer.if_type)) {
> > +			found = true;
> > +			break;
> > +		}
> > +	}
> > +
> > +	if (found) {
> > +		i++;
> > +		goto next;
> > +	}
> > +
> 
> Overall, keeping track of dev_num is a good solution.
> 
> I prefer not having a loop coded with goto's. Why not
> a nested loop.
Sure, I can use a nested loop.

> Also, there already is a search of the channel
> list in vmbus_process_offer() so why is another lookup needed?
vmbus_process_offer() looks for the if_instance and if_type matches
to determine if this is a subchannel vs primary channel. The loop 
terminates at different condition from hv_set_devnum().
So I didn't re-use the existing loop.

And this kind of search happens only during channel offering, and
doesn't impact performance much.

Thanks,
- Haiyang