Re: [PATCH 02/11] mm/mm_init: factor out common struct page initialization

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [High] mm/mm_init: __meminit on memmap_init_page_common() crashes at
  runtime
--

commit bb3e83c26b241fd60613632a0fd50cc529ce8be7
Author: Muchun Song <muchun.song@linux.dev>

mm/mm_init: factor out common struct page initialization

This commit factors out PFN-independent struct page initialization into
memmap_init_page_common() and uses it in both __init_single_page() and
vmemmap_shared_tail_page().

> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 0129152b74d87..9677698f30d3a 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -602,15 +602,28 @@ static inline void vmemmap_optimization_verify_zone(struct page *page)
>  			page_zone_id(page));
>  }
>  
> -void __meminit __init_single_page(struct page *page, unsigned long pfn,
> -				unsigned long zone, int nid)
> +/* Initialize PFN-independent fields common to pages in the same zone. */
> +void __meminit memmap_init_page_common(struct page *page,
> +		enum zone_type zone, int nid)
>  {
>  	mm_zero_struct_page(page);
> -	set_page_links(page, zone, nid, pfn);
> -	init_page_count(page);
> -	atomic_set(&page->_mapcount, -1);
> +	set_page_zone(page, zone);
> +	set_page_node(page, nid);
>  	page_cpupid_reset_last(page);
>  	page_kasan_tag_reset(page);
> +	atomic_set(&page->_mapcount, -1);
> +#ifdef CONFIG_ZONE_DEVICE
> +	if (zone == ZONE_DEVICE)
> +		__SetPageReserved(page);
> +#endif
> +}

[ ... ]

> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 9b80dd7326f7e..fd869617423a3 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -212,12 +212,7 @@ struct page __ref *vmemmap_shared_tail_page(unsigned int order, struct zone *zon
>  
>  	for (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++) {
>  		page = (struct page *)addr + i;
> -		mm_zero_struct_page(page);
> -		atomic_set(&page->_mapcount, -1);
> -		set_page_node(page, zone_to_nid(zone));
> -		set_page_zone(page, zone_idx(zone));
> -		if (zone_is_zone_device(zone))
> -			__SetPageReserved(page);
> +		memmap_init_page_common(page, zone_idx(zone), zone_to_nid(zone));
>  		prep_compound_tail(page, NULL, order);
>  	}

[Severity: High]
Can vmemmap_shared_tail_page() call memmap_init_page_common() after
.init.text has been freed when CONFIG_MEMORY_HOTPLUG is disabled?

When !CONFIG_MEMORY_HOTPLUG, __meminit expands to __init, placing
memmap_init_page_common() in .init.text, while __ref on
vmemmap_shared_tail_page() suppresses the modpost section mismatch warning.
With CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP=y (which does not depend on
CONFIG_MEMORY_HOTPLUG), allocating HugeTLB pages at runtime reaches
vmemmap_optimize_pte() -> folio_vmemmap_shared_tail_page() ->
vmemmap_shared_tail_page() and executes freed .init.text the first time a
zone's shared tail page for that order is allocated after boot.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261109095807.41547-1-songmuchun@bytedance.com?part=2