[PATCH] arm64: mm: Add pgd_page to support RCU fast_gup

[Will Deacon]

On Sat, Dec 20, 2014 at 12:49:40AM +0000, Jungseok Lee wrote:
> This patch adds pgd_page definition in order to keep supporting
> HAVE_GENERIC_RCU_GUP configuration. In addition, it changes pud_page
> expression to align with pmd_page for readability.
> 
> An introduction of pgd_page resolves the following build breakage
> under 4KB + 4Level memory management combo.
> 
> mm/gup.c: In function 'gup_huge_pgd':
> mm/gup.c:889:2: error: implicit declaration of function 'pgd_page' [-Werror=implicit-function-declaration]
>   head = pgd_page(orig);
>   ^
> mm/gup.c:889:7: warning: assignment makes pointer from integer without a cast
>   head = pgd_page(orig);
> 
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: Steve Capper <steve.capper at linaro.org>
> Signed-off-by: Jungseok Lee <jungseoklee85 at gmail.com>
> ---
>  arch/arm64/include/asm/pgtable.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index df22314..a1fe927 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -401,7 +401,7 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
>  	return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(addr);
>  }
>  
> -#define pud_page(pud)           pmd_page(pud_pmd(pud))
> +#define pud_page(pud)		pfn_to_page(__phys_to_pfn(pud_val(pud) & PHYS_MASK))

It would be cleaner to use pud_pfn here, otherwise we end up passing a
physical address with the lower attributes present to __phys_to_pfn, which
"knows" to shift them away.

>  #endif	/* CONFIG_ARM64_PGTABLE_LEVELS > 2 */
>  
> @@ -437,6 +437,8 @@ static inline pud_t *pud_offset(pgd_t *pgd, unsigned long addr)
>  	return (pud_t *)pgd_page_vaddr(*pgd) + pud_index(addr);
>  }
>  
> +#define pgd_page(pgd)		pfn_to_page(__phys_to_pfn(pgd_val(pgd) & PHYS_MASK))

Then you'd need to define pgd_pfn for this guy.

With that change:

  Acked-by: Will Deacon <will.deacon at arm.com>

Will