Re: [RFC 0/7] mm: dual-bitmap page allocator consistency checker

David Hildenbrand (Arm)
2026-04-25T05:51:18Z

On 4/24/26 18:25, Sasha Levin wrote:
> On Fri, Apr 24, 2026 at 05:42:53PM +0200, Vlastimil Babka (SUSE) wrote:
>> On 4/24/26 16:00, Sasha Levin wrote:
>>> Existing memory debugging tools - KASAN, KFENCE, page_poisoning - detect
>>> access violations and content corruption, but none of them can detect
>>> silent corruption in the page allocator's own metadata. If a hardware
>>> bit flip corrupts an allocation bitmap, the allocator hands out a page
>>
>> An allocation what? The page allocator is a buddy allocator, it has no
>> bitmap to track free/allocated state of pages?
>
> You're right, the cover letter is misleading there. Buddy doesn't use a bitmap:
> PageBuddy lives in page_type, the free list is a list, and page->private holds
> the order. The dual-bitmap is new metadata the feature adds, maintained from
> the alloc/free hooks.

Given that you have PageBuddy (first "bit"), could we use a second bit in page_ext?

--
Cheers,

David