[PATCH v3 4/4] mm/mm_init: Fix pageblock migratetype for ZONE_DEVICE compound pages

[Muchun Song]

> On Apr 21, 2026, at 12:15, Oscar Salvador <osalvador at suse.de> wrote:
> 
> On Tue, Apr 21, 2026 at 10:20:44AM +0800, Muchun Song wrote:
>> The memmap_init_zone_device() function only initializes the migratetype
>> of the first pageblock of a compound page. If the compound page size
>> exceeds pageblock_nr_pages (e.g., 1GB hugepages with 2MB pageblocks),
>> subsequent pageblocks in the compound page remain uninitialized.
>> 
>> Move the migratetype initialization out of __init_zone_device_page()
>> and into a separate pageblock_migratetype_init_range() function. This
>> iterates over the entire PFN range of the memory, ensuring that all
>> pageblocks are correctly initialized.
>> 
>> Fixes: c4386bd8ee3a ("mm/memremap: add ZONE_DEVICE support for compound pages")
>> Signed-off-by: Muchun Song <songmuchun at bytedance.com>
>> Reviewed-by: Mike Rapoport (Microsoft) <rppt at kernel.org>
> 
> Would not the call to __init_zone_device_page() from
> memmap_init_compound() take care of the subsequent pageblocks?
> 

No, it won't handle them automatically, as the page count from
compound_nr_pages doesn't cover the following pageblocks.

Thanks.
Muchun

> 
> -- 
> Oscar Salvador
> SUSE Labs