Re: Report 2 in ext4 and journal based on v5.17-rc1

Reimar Döffinger
2022-03-05T15:14:05Z

Hi,
Sorry to butt in as an outsider, but this seems like a shockingly disrespectful discussion for such a wide CC list.
I don't want to make rules how you discuss things (I very rarely contribute), and I see the value in a frank discussion, but maybe you could continue with a reduced CC list?
I find it unlikely that I am the only one who could do without this.

Best regards,
Reimar Döffinger

> On 5 Mar 2022, at 15:55, Byungchul Park <byungchul.park@lge.com> wrote:
>
> On Fri, Mar 04, 2022 at 10:40:35PM -0500, Theodore Ts'o wrote:
>> On Fri, Mar 04, 2022 at 12:20:02PM +0900, Byungchul Park wrote:
>>>
>>> I found a point that the two wait channels don't lead a deadlock in
>>> some cases thanks to Jan Kara. I will fix it so that Dept won't
>>> complain it.
>>
>> I sent my last (admittedly cranky) message before you sent this. I'm
>> glad you finally understood Jan's explanation. I was trying to tell
>
> Not finally. I've understood him whenever he tried to tell me something.
>
>> you the same thing, but apparently I failed to communicate in a
>
> I don't think so. Your point and Jan's point are different. All he has
> said make sense. But yours does not.
>
>> sufficiently clear manner. In any case, what Jan described is a
>> fundamental part of how wait queues work, and I'm kind of amazed that
>> you were able to implement DEPT without understanding it. (But maybe
>
> Of course, it was possible because all that Dept has to know for basic
> work is wait and event. The subtle things like what Jan told me help
> Dept be better.
>
>> that is why some of the DEPT reports were completely incomprehensible
>
> It's because you are blinded to blame at it without understanding how
> Dept works at all. I will fix those that must be fixed. Don't worry.
>
>> to me; I couldn't interpret why in the world DEPT was saying there was
>> a problem.)
>
> I can tell you if you really want to understand why. But I can't if you
> are like this.
>
>> In any case, the thing I would ask is a little humility. We regularly
>> use lockdep, and we run a huge number of stress tests, throughout each
>> development cycle.
>
> Sure.
>
>> So if DEPT is issuing lots of reports about apparently circular
>> dependencies, please try to be open to the thought that the fault is
>
> No one was convinced that Dept doesn't have a fault. I think your
> worries are too much.
>
>> in DEPT, and don't try to argue with maintainers that their code MUST
>> be buggy --- but since you don't understand our code, and DEPT must be
>
> No one argued that their code must be buggy, either. So I don't think
> you have to worry about what's never happened.
>
>> theoretically perfect, that it is up to the Maintainers to prove to
>> you that their code is correct.
>>
>> I am going to gently suggest that it is at least as likely, if not
>> more likely, that the failure is in DEPT or your understanding of what
>
> No doubt. I already think so. But it doesn't mean that I have to keep
> quiet without discussing to imporve Dept. I will keep improving Dept in
> a reasonable way.
>
>> how kernel wait channels and locking works. After all, why would it
>> be that we haven't found these problems via our other QA practices?
>
> Let's talk more once you understand how Dept works at least 10%. Or I
> think we cannot talk in a productive way.
>