Re: [PATCH] ARM: update __swp_entry_to_pte() to use PTE_TYPE_FAULT

Anshuman Khandual
2021-05-17T07:49:22Z

On 5/13/21 4:57 PM, Russell King wrote:
> Swap entries use a faulting PTE which have the least two significant
> bits as zero. Due to this, the use of PTE_TYPE_FAULT was overlooked,
> but really should have been included in __swp_entry_to_pte().
>
> Convert this macro to use PTE_TYPE_FAULT to properly document what is
> going on here, and use __pte() to convert the swp_entry_t to a pte_t.
>
> This results in no change to the resulting kernel text.
>
> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
> ---
> arch/arm/include/asm/pgtable.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
> index c02f24400369..c43e07d6046d 100644
> --- a/arch/arm/include/asm/pgtable.h
> +++ b/arch/arm/include/asm/pgtable.h
> @@ -303,7 +303,7 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
> #define __swp_entry(type,offset) ((swp_entry_t) { ((type) << __SWP_TYPE_SHIFT) | ((offset) << __SWP_OFFSET_SHIFT) })
>
> #define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
> -#define __swp_entry_to_pte(swp) ((pte_t) { (swp).val })
> +#define __swp_entry_to_pte(swp) __pte((swp).val | PTE_TYPE_FAULT)

LGTM and FWIW..

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

>
> /*
> * It is an error for the kernel to have more swap files than we can
>