netdev - Re: [patch net-next RFC 3/3] switchdev: introduce deferred variants of obj

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Message-ID: <20151008144451.GN2186@nanopsycho.orion>
Date:	Thu, 8 Oct 2015 16:44:51 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Or Gerlitz <gerlitz.or@...il.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>, idosch@...lanox.com,
	Elad Raz <eladr@...lanox.com>,
	Scott Feldman <sfeldma@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	Andrew Lunn <andrew@...n.ch>,
	john fastabend <john.fastabend@...il.com>,
	David Laight <David.Laight@...lab.com>
Subject: Re: [patch net-next RFC 3/3] switchdev: introduce deferred variants
 of obj_add/del helpers

Thu, Oct 08, 2015 at 04:41:43PM CEST, gerlitz.or@...il.com wrote:
>On Thu, Oct 8, 2015 at 4:25 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>> Thu, Oct 08, 2015 at 03:21:44PM CEST, gerlitz.or@...il.com wrote:
>>>On Thu, Oct 8, 2015 at 4:09 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>>>> Thu, Oct 08, 2015 at 10:28:58AM CEST, jiri@...nulli.us wrote:
>>>>>Thu, Oct 08, 2015 at 08:45:58AM CEST, gerlitz.or@...il.com wrote:
>>>>>>On Wed, Oct 7, 2015 at 9:30 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>>>
>>>>>>This introduced a regression to the 2-phase commit scheme, since the
>>>>>>prepare commit can fail
>>>>>>and that would go un-noticed toward the upper layer, agree?
>>>
>>>>>Well, no. This still does the transaction for all lower devices in one
>>>>>go. No change in that.
>>>
>>>> Now I get it, yes you are right. But currently there is no code in
>>>> kernel which would control retval of deferred attr_set or obj_add/del
>>>
>>>I am not sure to understand your reply. You are saying that when the deferred
>>>procedures complete (e.g fail in the prepare phase) they can't actually let
>>>the upper layer to realize that this change isn't possible? this is
>>>exactly the bug.
>>
>> Correct. But check the code. Callers of current deferred variants do
>> not care about the retval. Therefore this is not a regression.
>
>No sure to follow on (current) callers of current deferred variants,
>are there already
>deferred  variants for switchdev ops? aren't they introduced in this series?

Yes they are. Those are those places where deferred variants need to be
called.

>
>> It makes sense in my opinion. If you are a called and you explicitly say to
>> defer the operation, you cannot expect retval.
>
>yes, this might make sure for the caller, if they want to know the
>retval, shouldn't use
>the deferred variant.
>
>Or.
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