Re: [PATCH for-9.0 1/3] qtest/virtio-9p-test.c: consolidate create dir, file and symlink tests

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Wednesday, March 27, 2024 12:28:17 PM CET Daniel Henrique Barboza wrote:
> On 3/27/24 07:14, Christian Schoenebeck wrote:
> > On Wednesday, March 27, 2024 10:33:27 AM CET Daniel Henrique Barboza wrote:
> >> On 3/27/24 05:47, Christian Schoenebeck wrote:
> >>> On Tuesday, March 26, 2024 6:47:17 PM CET Daniel Henrique Barboza wrote:
> >>>> On 3/26/24 14:05, Greg Kurz wrote:
> >>>>> On Tue, 26 Mar 2024 10:26:04 -0300
> >>>>> Daniel Henrique Barboza <dbarboza@ventanamicro.com> wrote:
> >>>>>
> >>>>>> The local 9p driver in virtio-9p-test.c its temporary dir right at the
> >>>>>> start of qos-test (via virtio_9p_create_local_test_dir()) and only
> >>>>>> deletes it after qos-test is finished (via
> >>>>>> virtio_9p_remove_local_test_dir()).
> >>>>>>
> >>>>>> This means that any qos-test machine that ends up running virtio-9p-test local
> >>>>>> tests more than once will end up re-using the same temp dir. This is
> >>>>>> what's happening in [1] after we introduced the riscv machine nodes: if
> >>>>>> we enable slow tests with the '-m slow' flag using qemu-system-riscv64,
> >>>>>> this is what happens:
> >>>>>>
> >>>>>> - a temp dir is created, e.g. qtest-9p-local-WZLDL2;
> >>>>>>
> >>>>>> - virtio-9p-device tests will run virtio-9p-test successfully;
> >>>>>>
> >>>>>> - virtio-9p-pci tests will run virtio-9p-test, and fail right at the
> >>>>>>      first slow test at fs_create_dir() because the "01" file was already
> >>>>>>      created by fs_create_dir() test when running with the virtio-9p-device.
> >>>>>>
> >>>>>> We can fix it by making every test clean up their changes in the
> >>>>>> filesystem after they're done. But we don't need every test either:
> >>>>>> what fs_create_file() does is already exercised in fs_unlinkat_dir(),
> >>>>>> i.e. a dir is created, verified to be created, and then removed. Fixing
> >>>>>> fs_create_file() would turn it into fs_unlikat_dir(), so we don't need
> >>>>>> both. The same theme follows every test in virtio-9p-test.c, where the
> >>>>>> 'unlikat' variant does the same thing the 'create' does but with some
> >>>>>> cleaning in the end.
> >>>>>>
> >>>>>> Consolide some tests as follows:
> >>>>>>
> >>>>>> - fs_create_dir() is removed. fs_unlinkat_dir() is renamed to
> >>>>>>      fs_create_unlinkat_dir();
> >>>>>>
> >>>>>> - fs_create_file() is removed. fs_unlinkat_file() is renamed to
> >>>>>>      fs_create_unlinkat_file(). The "04" dir it uses is now being removed;
> >>>>>>
> >>>>>> - fs_symlink_file() is removed. fs_unlinkat_symlink() is renamed to
> >>>>>>      fs_create_unlinkat_symlink(). Both "real_file" and the "06" dir it
> >>>>>>      creates is now being removed.
> >>>>>>
> >>>>>
> >>>>> The  change looks good functionally but it breaks the legitimate assumption
> >>>>> that files "06/*" come from test #6 and so on... I think you should consider
> >>>>> renumbering to avoid confusion when debugging logs.
> >>>>>
> >>>>> Since this will bring more hunks, please split this in enough reviewable
> >>>>> patches.
> >>>>
> >>>> Fair enough. Let me cook a v2. Thanks,
> >>>
> >>> Wouldn't it be much simpler to just change the name of the temporary
> >>> directory, such that it contains the device name as well? Then these tests
> >>> runs would run on independent directories and won't interfere with each other
> >>> and that wouldn't need much changes I guess.
> >>
> >> That's true. If we were just trying to fix the issue then I would go with this
> >> approach since it's simpler. But given that we're also cutting half the tests while
> >> retaining the coverage I think this approach is worth the extra code.
> > 
> > Well, I am actually not so keen into all those changes. These tests were
> > intentionally split, and yes with costs of a bit redundant (test case) code.
> > But they were cleanly build up on each other, from fundamental requirements
> > like whether it is possible to create a directory and file ... and then the
> > subsequent tests would become more and more demanding.
> > 
> > That way it was easier to review if somebody reports a test to fail, because
> > you could immediately see whether the preceding fundamental tests succeeded.
> 
> The current test design is flawed. It's based on a premise that doesn't happen, i.e.
> a new temp dir will be created every time the test suit is executed. In reality the
> temp dir is created only once in the constructor of the test, at the start of qos-test
> (tests/qtest/qos-test.c, run_one_test()) and removed only once at the destructor
> at the end of the run.
> 
> It's not possible to add a 'device name' in the created temp dir because we're too early
> in the process, the tests didn't start at that point. So, with the current temp dir design,
> the tests needs to clean themselves up after each run.
> 
> Here's the alternatives I'm willing to go for:
> 
> - what I just sent in v2;
> 
> - add cleanups in all existing tests. We can keep all of them, but the 'create' tests
> will be carbon copies of the 'unlinkat' tests but with different names. Can be done;
> 
> - if we really want the tests untouched we can rework how the 'temp dir' is created/deleted.
> The test dir will be created and removed after each test via the 'before' callback. To be
> honest this seems like the best approach we can take, aside from what I did in v2, and
> it's on par with how tests like vhost-user-test.c works.

Yeah, the latter sounds like the best solution to me, too.

Don't get me wrong, I didn't want to burden you with more work. It's really
just that I think that restructuring all test cases is contra productive.

If you want I can also look into that. Just let me know.

Thanks!

/Christian