Re: [PATCH] ext: EXT4_KUNIT_TESTS should depend on EXT4_FS instead of selecting it

[Theodore Y. Ts'o]

On Wed, Oct 21, 2020 at 02:16:56PM -0700, Randy Dunlap wrote:
> On 10/21/20 2:15 PM, Brendan Higgins wrote:
> > On Tue, Oct 20, 2020 at 12:37 AM Geert Uytterhoeven
> > <geert@xxxxxxxxxxxxxx> wrote:
> >>
> >> EXT4_KUNIT_TESTS selects EXT4_FS, thus enabling an optional feature the
> >> user may not want to enable.  Fix this by making the test depend on
> >> EXT4_FS instead.
> >>
> >> Fixes: 1cbeab1b242d16fd ("ext4: add kunit test for decoding extended timestamps")
> >> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > 
> > If I remember correctly, having EXT4_KUNIT_TESTS select EXT4_FS was
> > something that Ted specifically requested, but I don't have any strong
> > feelings on it either way.
> 
> omg, please No. depends on is the right fix here.

So my requirement which led to that particular request is to keep what
needs to be placed in .kunitconfig to a small and reasonable set.

Per Documentation/dev-tools/kunit, we start by:

    cd $PATH_TO_LINUX_REPO
    cp arch/um/configs/kunit_defconfig .kunitconfig

we're then supposed to add whatever Kunit tests we want to enable, to wit:

CONFIG_EXT4_KUNIT_TESTS=y

so that .kunitconfig would look like this:

CONFIG_KUNIT=y
CONFIG_KUNIT_TEST=y
CONFIG_KUNIT_EXAMPLE_TEST=y
CONFIG_EXT4_KUNIT_TESTS=y

... and then you should be able to run:

./tools/testing/kunit/kunit.py run

... and have the kunit tests run.  I would *not* like to have to put a
huge long list of CONFIG_* dependencies into the .kunitconfig file.

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**.

Cheers,

					- Ted