Re: [PATCH 30/30] mm/mmap: Drop ARCH_HAS_VM_GET_PAGE_PROT

[Geert Uytterhoeven]

Hi Anshuman,

On Mon, Feb 14, 2022 at 7:54 AM Anshuman Khandual
<anshuman.khandual@xxxxxxx> wrote:
> All platforms now define their own vm_get_page_prot() and also there is no
> generic version left to fallback on. Hence drop ARCH_HAS_GET_PAGE_PROT.
>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>

Thanks for your patch!

> -       select ARCH_HAS_VM_GET_PAGE_PROT

So before, all architectures selected ARCH_HAS_VM_GET_PAGE_PROT...

> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -81,7 +81,6 @@ static void unmap_region(struct mm_struct *mm,
>                 struct vm_area_struct *vma, struct vm_area_struct *prev,
>                 unsigned long start, unsigned long end);
>
> -#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT

... hence the block below was not included.

>  /* description of effects of mapping type and prot in current implementation.
>   * this is due to the limited x86 page protection hardware.  The expected
>   * behavior is in parens:
> @@ -102,8 +101,6 @@ static void unmap_region(struct mm_struct *mm,
>   *                                                             w: (no) no
>   *                                                             x: (yes) yes
>   */
> -#endif /* CONFIG_ARCH_HAS_VM_GET_PAGE_PROT */
> -

So shouldn't the whole block be removed instead?
Do I need more coffee??

>  static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
>  {
>         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds