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?