Date:	Wed, 15 Aug 2012 09:30:45 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Andy Gospodarek <gospo@...hat.com>, netdev@...r.kernel.org,
	davem@...emloft.net, edumazet@...gle.com, faisal.latif@...el.com,
	roland@...nel.org, sean.hefty@...el.com, hal.rosenstock@...il.com,
	fubar@...ibm.com, andy@...yhouse.net, divy@...lsio.com,
	jitendra.kalsaria@...gic.com, sony.chacko@...gic.com,
	linux-driver@...gic.com, kaber@...sh.net, ursula.braun@...ibm.com,
	blaschka@...ux.vnet.ibm.com, linux390@...ibm.com,
	shemminger@...tta.com, therbert@...gle.com,
	xiyou.wangcong@...il.com, joe@...ches.com,
	gregory.v.rose@...el.com, john.r.fastabend@...el.com,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-s390@...r.kernel.org, bridge@...ts.linux-foundation.org,
	fbl@...hat.com
Subject: Re: [patch net-next v2 00/15] net: introduce upper device lists and
 remove dev->master

Tue, Aug 14, 2012 at 10:32:53PM CEST, bhutchings@...arflare.com wrote:
>On Tue, 2012-08-14 at 16:19 -0400, Andy Gospodarek wrote:
>> On Tue, Aug 14, 2012 at 05:05:33PM +0200, Jiri Pirko wrote:
>> > Hi all.
>> > 
>> > Recent discussion around
>> > "[net-next] bonding: don't allow the master to become its slave"
>> > forced me to think about upper<->lower device connections.
>> > 
>> > This patchset adds a possibility to record upper device linkage.
>> > All upper<->lower devices are converted to use this mechanism right after.
>> > That leads to dev->master removal because this info becomes redundant since
>> > "unique links" have the same value.
>> > 
>> > After all changes, there is no longer possible to do:
>> > "bond->someotherdevice->samebond"
>> > 
>> > Also I think that drivers like cxgb3, qlcnic, qeth would benefit by this
>> > in future by being able to get more appropriate info about l3 addresses.
>> > 
>> > v1->v2:
>> > - s/unique/master/ better naming + stays closer to the history
>> > - fixed vlan err goto
>> > - original patch 15 (WARN_ON change) is squashed into the first patch
>> > - fixed netdev_unique_upper_dev_get_rcu() case of upper==NULL
>> I just started to review v1 when v2 came out, but luckily the changes
>> were not too significant that I need to start all over.
>> 
>> The first note is that I didn't like the use of the term 'upper' -- it
>> seems like 'stacked' might be a better alternative as these are stacked
>> devices.
>
>When linking any two devices in a stack, one will be upper and the other
>lower.  The lower device might itself be stacked on top of a further
>device, so 'stacked' is not a useful distinguishing adjective in
>variable names.  It might be a useful term in the commit messages and
>kernel-doc, though.
>
>> One thing to note is that I don't see any clear changelog that states
>> the current goals for this.  You have stated in several places that it
>> will no longer be possible to create bonds of bonds, but there are
>> probably a few more things it might be wise to intentionally outlaw.
>>
>> What about teams of teams?  Or teams of bonds?  Or bonds of teams?
>> Bonds of vlans?
>[...]
>
>It doesn't disallow bonds of bonds (unless I'm missing something).  It
>disallows loops that involve any or all of those types of stacked
>devices.

Exactly. It's every "upper driver" responsibility to check which device
it allows to be added as lower.

>
>Ben.
>
>-- 
>Ben Hutchings, Staff Engineer, Solarflare
>Not speaking for my employer; that's the marketing department's job.
>They asked us to note that Solarflare product names are trademarked.
>
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