linux-kernel - Re: staging: lustre: One function call less in class_register

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Date:	Tue, 26 Jul 2016 17:49:49 -0400
From:	Oleg Drokin <oleg.drokin@...el.com>
To:	SF Markus Elfring <elfring@...rs.sourceforge.net>
Cc:	<devel@...verdev.osuosl.org>, <lustre-devel@...ts.lustre.org>,
	"Andreas Dilger" <andreas.dilger@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	<kernel-janitors@...r.kernel.org>,
	Julia Lawall <julia.lawall@...6.fr>,
	Bhumika Goyal <bhumirks@...il.com>
Subject: Re: staging: lustre: One function call less in class_register_type() after error detection

On Jul 26, 2016, at 3:56 PM, SF Markus Elfring wrote:

>> But kobject_put() already checks for NULL, right?
> 
> Yes. - Such an input parameter validation is performed by the
> function implementation.
> 
> 
>> you just submitted another batch about that in other area.
> 
> I sent update suggestions because of this function property for two
> Linux software modules in the year 2015.
> 
> 
>>> Adjust jump targets according to the Linux coding style convention.
>> 
>> Not that I am totally against this patch,
> 
> Thanks for your feedback.
> 
> 
>> but when we do not need the extra checks, a single jump target is ok too in my mind
> 
> A single goto label will look convenient for a while. It will often work
> for several use cases.
> 
> 
>> (extra benefit - there's not going to be any chance of a mistake to where to jump to).
> 
> I have got an other opinion when you would like to care for a bit
> more software efficiency.
> 
> 
>> And when we have a single jump target, there's no supersmart naming
>> like free_this_and_that_and_that_other_thing_too.
> 
> How often do you care for efficient exception handling in the shown
> function implementations?

This function is called several times during lustre module insert.
Namely it's called 5 times for 5 types:
osc, mdc, lov, lmv, mgc.

It's not called any more than that, so it's not exactly a super hot-path function
to overoptimize it, and the failure is presumed to never happen too
(or the module would be non-functional).

I guess you have already did all the work so I don't have any principal objections
here, it's just like I said, in a non-super contended path, a single
"fail" label is probably easier on the developer when they need to add another
check there, as opposed to figuring and possibly adding a correct another
label that would do something sensible.

Thank you for your contributions.