Re: [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT

[David Hildenbrand (Arm)]

On 9/27/26 21:20, David Carlier wrote:
> On Mon, Sep 21, 2026 at 09:59:02PM +0200, David Hildenbrand (Arm) wrote:
>>  enum {
>> -	SECTION_MARKED_PRESENT_BIT,
>>  	SECTION_HAS_MEM_MAP_BIT,
>>  	SECTION_IS_ONLINE_BIT,
>>  	SECTION_IS_EARLY_BIT,
> 
> Hi David,

Hi!

> 
> It seems dropping SECTION_MARKED_PRESENT_BIT shifts the other section flags down
> one bit. crash hardcodes SECTION_HAS_MEM_MAP as (1UL << 1) in
> pfn_to_map(), so it now tests SECTION_IS_ONLINE: offline and
> ZONE_DEVICE sections no longer resolve to a struct page. makedumpfile
> only checks bit 0 and is fine.

Thanks. To be expected when relying on kernel internals.

Which makes me wonder why makedumpfile
(https://github.com/makedumpfile/makedumpfile) not require any such information.

> 
> Keep bit 0 reserved, or export the bits via vmcoreinfo?
We could export it, or crash can simply detect the change based on the kernel
version. I remember the latter was done in makedumpfile in the past (although we
export it).

I can send a separate patch to export it.

-- 
Cheers,

David