> On Jun 13, 2023, at 7:59 AM, Theo de Raadt <dera...@openbsd.org> wrote:
>
> Thordur I. Bjornsson <thord...@secnorth.net> wrote:
>
>> On Mon, Jun 12, 2023 at 9:15 PM Bob Beck <b...@obtuse.com> wrote:
>>>
>>> On Mon, Jun 12, 2023 at 11:01:18AM -0600, Theo de Raadt wrote:
>>>> + KASSERTMSG(1, "Ich Habe eine Rotweinflarsche in meinem Arsche");
>>>> That part of the diff is not OK. If everyone did this, we would have a
>>>> mess on our hands.
>>> (or I could simply deleted it)
>> +1
>>
>> Is it on purpose that this is completely silent ?
>> Perhaps the warning in ffs_vfsops should go "WARNING: soft updates are
>> now ignored" and the option dropped from GENERIC ?
>
> The purpose of Bob's diff is to silently (quietly) simply disable softdep
> mount requests.
>
> They will be downgraded to regular mounts. But then we want to make
> sure that the back-end code isn't accidentaly called, because of some
> bug, that's where his whiny assert comes into play.
>
> The reason to disable softdep, is that softdep has crazy callback schemes and
> context issues that are making it hard to reason about vfs locking.
>
> If we disable softdep, we may be able to unlock nami / vfs / etc better.
>
> When / if such locking/scheduling changes are finished, softdep can be
> repaired.
Softdep is also a significant hindrance to progress by mere mortals in the
areas interfacing between the filesystem and the caching mid layer. Don’t get
me wrong, it’s is brilliantly engineered from the point of view of it does
absolutely everything it can within the realm of what’s permissible in current
VFS layer pushing all the boundaries of what you can do in order to do what it
does.
The problem with that is it is one of the things that adds a lot of complexity,
and makes it very hard to change things an evolve for something like, oh,
having a log based filesystem or things like that.
My desire to get rid to it is hopefully to make it where working in this area
of the kernel is something more people could slowly learn how to do and make
progress on things, without any change being an insurmountable obstacle with a
learning curve so high people will give up in frustration because everything
they try has subtle interactions and ends up getting backed out.
