RE: [PATCH] fs/ceph/addr: always call ceph_shift_unused_folios_left()

[Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>]

On Fri, 2025-09-05 at 20:35 +0200, Max Kellermann wrote:
> On Fri, Sep 5, 2025 at 7:11 PM Viacheslav Dubeyko <Slava.Dubeyko@ibm.com> wrote:
> > 
> > On Fri, 2025-09-05 at 05:41 +0200, Max Kellermann wrote:
> > > Thanks, I'm glad you could verify the bug and my fix. In case this
> > > wasn't clear: you saw just a warning, but this is usually a kernel
> > > crash due to NULL pointer dereference. If you only got a warning but
> > > no crash, it means your test VM does not use transparent huge pages
> > > (no huge_zero_folio allocated yet). In a real workload, the kernel
> > > would have crashed.
> > 
> > I would like to reproduce the crash. But you've share only these steps.
> > And it looks like that it's not the complete recipe. So, something was missing.
> > If you could share more precise explanation of steps, it will be great.
> 
> The email you just cited explains the circumstances that are necessary
> for the crash to occur.
> 
> Let me repeat it for you: you have to ensure that huge_zero_folio gets
> allocated (or else the code that dereferences the NULL pointer and
> crashes gets skipped).
> 
> Got it now?

Not yet. I would like to see the clear explanation of steps.
Otherwise, the probability to reproduce the crash is equal to zero.

Thanks,
Slava.