linux-kernel - Re: [PATCH 1/4] m68k: mm: Convert get_pointer

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Message-ID: <CAMuHMdXd=eha_pRNGCFHN7sS2OOh60cj=c=yPUyg_-J0S8V8yQ@mail.gmail.com>
Date: Thu, 26 Jun 2025 10:38:48 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc: linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org, 
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/4] m68k: mm: Convert get_pointer_table() to use ptdescs

Hi Vishal,

On Wed, 11 Jun 2025 at 02:13, Vishal Moola (Oracle)
<vishal.moola@...il.com> wrote:
> Motorola uses get_pointer_table() for page tables, so it should be using
> struct ptdesc, not struct page.
>
> This helps us prepare to allocate ptdescs as their own memory
> descriptor, and prepares to remove a user of page->lru.
>
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
i.e. will queue in the m68k tree for v6.17, with the small changes
described below.

> --- a/arch/m68k/mm/motorola.c
> +++ b/arch/m68k/mm/motorola.c
> @@ -148,16 +148,18 @@ void *get_pointer_table(struct mm_struct *mm, int type)
>
>         /*
>          * For a pointer table for a user process address space, a
> -        * table is taken from a page allocated for the purpose.  Each
> -        * page can hold 8 pointer tables.  The page is remapped in
> +        * table is taken from a ptdesc allocated for the purpose.  Each
> +        * ptdesc can hold 8 pointer tables.  The ptdesc is remapped in
>          * virtual address space to be noncacheable.
>          */
>         if (mask == 0) {
> -               void *page;
> +               struct ptdesc *ptdesc = pagetable_alloc(GFP_KERNEL | __GFP_ZERO, 0);

I will move the assignment just before the NULL-check below, to ease
applying the WIP preempt patches on top.

> +               void *pt_addr;

I will move this one line down, to follow the reverse Xmas rule.

>                 ptable_desc *new;
>
> -               if (!(page = (void *)get_zeroed_page(GFP_KERNEL)))
> +               if (!ptdesc)
>                         return NULL;
> +               pt_addr = ptdesc_address(ptdesc);
>
>                 switch (type) {
>                 case TABLE_PTE:

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

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