Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros

[Mark Rutland]

On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
> From: James Morse <james.morse@xxxxxxx>
> 
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
> 
> For architectures that don't provide p?d_large() macros, provided a
> does nothing default.
> 
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>
> ---
>  include/asm-generic/pgtable.h | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 05e61e6c843f..f0de24100ac6 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -1186,4 +1186,23 @@ static inline bool arch_has_pfn_modify_check(void)
>  #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
>  #endif
>  
> +/*
> + * p?d_large() - true if this entry is a final mapping to a physical address.

It might make sense to s/final/leaf/, but otherwise that's a great
definition!

> + * This differs from p?d_huge() by the fact that they are always available (if
> + * the architecture supports large pages at the appropriate level) even
> + * if CONFIG_HUGETLB_PAGE is not defined.

I'm not sure if we need this part, since we don't mention
p?d_trans_huge(), etc, but either way:

Acked-by: Mark Rutland <mark.rutland@xxxxxxx>

Thanks,
Mark.

> + */
> +#ifndef pgd_large
> +#define pgd_large(x)	0
> +#endif
> +#ifndef p4d_large
> +#define p4d_large(x)	0
> +#endif
> +#ifndef pud_large
> +#define pud_large(x)	0
> +#endif
> +#ifndef pmd_large
> +#define pmd_large(x)	0
> +#endif
> +
>  #endif /* _ASM_GENERIC_PGTABLE_H */
> -- 
> 2.20.1
>