Re: [PATCH 1/2] mm: convert clear_huge_page() to clear_large_folio()

[Matthew Wilcox <willy@infradead.org>]

On Thu, Jun 13, 2024 at 06:53:43PM +0800, Kefeng Wang wrote:
> +++ b/include/linux/mm.h
> @@ -4071,9 +4071,7 @@ enum mf_action_page_type {
>  };
>  
>  #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
> -extern void clear_huge_page(struct page *page,
> -			    unsigned long addr_hint,
> -			    unsigned int pages_per_huge_page);
> +void clear_large_folio(struct folio *folio, unsigned long addr_hint);

I think this is properly called

void folio_zero_user(struct folio *folio, unsigned long user_addr);

> -void clear_huge_page(struct page *page,
> -		     unsigned long addr_hint, unsigned int pages_per_huge_page)
> +void clear_large_folio(struct folio *folio, unsigned long addr_hint)
>  {
> +	unsigned int pages_per_huge_page = folio_nr_pages(folio);

I think it's worth renaming to nr_pages here.

>  	unsigned long addr = addr_hint &
>  		~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);

This can just be:

	unsigned long addr = user_addr & ~(folio_size(folio) - 1);

Umm.  Except this assumes that the folio is always mapped to userspace
at its natural alignment.  And that's true for hugetlb, but not true
for THP.  So I think this needs to be moved into the callers for which
it is true, and we need documentation that user_addr is expected to be
the base address that the folio is mapped at.