linux-kernel - Re: [PATCH] ext: EXT4_KUNIT_TESTS should depend on EXT4

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Message-ID: <04d63aa1-ec2b-e6d2-5b51-6c05c5338ded@infradead.org>
Date:   Wed, 21 Oct 2020 20:55:36 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        linux-ext4@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Gow <davidgow@...gle.com>
Subject: Re: [PATCH] ext: EXT4_KUNIT_TESTS should depend on EXT4_FS instead of
 selecting it

On 10/21/20 8:43 PM, Theodore Y. Ts'o wrote:
> On Wed, Oct 21, 2020 at 04:07:15PM -0700, Randy Dunlap wrote:
>>> I'm don't particularly care how this gets achieved, but please think
>>> about how to make it easy for a kernel developer to run a specific set
>>> of subsystem unit tests.  (In fact, being able to do something like
>>> "kunit.py run fs/ext4 fs/jbd2" or maybe "kunit.py run fs/..." would be
>>> *great*.  No need to fuss with hand editing the .kunitconfig file at
>>> all would be **wonderful**.
>>
>> I understand the wish for ease of use, but this is still the tail
>> wagging the dog.
>>
>> The primary documentation for 'select' is
>> Documentation/kbuild/kconfig-language.rst, which says:
>>
>>   Note:
>> 	select should be used with care. select will force
>> 	a symbol to a value without visiting the dependencies.
>> 	By abusing select you are able to select a symbol FOO even
>> 	if FOO depends on BAR that is not set.
>> 	In general use select only for non-visible symbols
>> 	(no prompts anywhere) and for symbols with no dependencies.
>> 	That will limit the usefulness but on the other hand avoid
>> 	the illegal configurations all over.
>>
> 
> Well, the KUNIT configs are kinda of a special case, since normally
> they don't have a lot of huge number of dependencies, since unit tests
> in general are not integration tests.  So ideally, dependencies will
> mostly be replaced with mocking functions.  And if there are *real*
> dependencies that the Kunit Unit tests need, they can be explicitly
> pulled in with selects.
> 
> That being said, as I said, I'm not picky about *how* this gets
> achieved.  But ease of use is a key part of making people more likely
> to run the unit tests.  So another way of solving the problem might be
> to put some kind of automated dependency solver into kunit.py, or some
> way of manually adding the necessary dependencies in some kind of
> Kunitconfig file that are in directories where their are Unit tests,
> or maybe some kind of extenstion to the Kconfig file.  My main
> requirement is that the only thing that should be necessary for
> enabling the ext4 Kunit tests should be adding a single line to the
> .kunitconfig file.  It's not fair to make the human developer manually
> have to figure out the dependency chains.
> 
> As far as I'm concerned, ease of use is important enough to justfy
> special casing and/or bending the rules as far as "select" is concered
> for Kunit-related CONFIG items.  But if someone else want to suggest a
> better approach, I'm all ears.
> 
> Cheers,

Indeed.  For the record, I support testing and have for a long time.
I just don't care for this big fscking hammer approach.
But I doubt that I can change your mind.

g'day.
-- 
~Randy