Re: [PATCH] mm/thp: Define default pmd_pgtable()

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Linux MM <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	 Nick Hu <nickhu@andestech.com>,
	Richard Henderson <rth@twiddle.net>,
	 Vineet Gupta <vgupta@synopsys.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
	Brian Cain <bcain@codeaurora.org>,
	 Michal Simek <monstr@monstr.eu>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	 Ley Foon Tan <ley.foon.tan@intel.com>,
	Jonas Bonn <jonas@southpole.se>,
	 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	Stafford Horne <shorne@gmail.com>,
	 "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
	 Michael Ellerman <mpe@ellerman.id.au>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	 Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Heiko Carstens <hca@linux.ibm.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	 "David S. Miller" <davem@davemloft.net>,
	Jeff Dike <jdike@addtoit.com>,
	 Thomas Gleixner <tglx@linutronix.de>,
	Chris Zankel <chris@zankel.net>,
	 Linux-Arch <linux-arch@vger.kernel.org>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm/thp: Define default pmd_pgtable()
Date: Tue, 8 Jun 2021 08:58:43 +0200	[thread overview]
Message-ID: <CAMuHMdWVrUgfXAud_3fpjfO-1yqXzf75Jtk6SNqqcR39-ZzQJA@mail.gmail.com> (raw)
In-Reply-To: <1623130327-13325-1-git-send-email-anshuman.khandual@arm.com>

Hi Anshuman,

On Tue, Jun 8, 2021 at 7:31 AM Anshuman Khandual
<anshuman.khandual@arm.com> wrote:
> Currently most platforms define pmd_pgtable() as pmd_page() duplicating the
> same code all over. Instead just define a default value i.e pmd_page() for
> pmd_pgtable() and let platforms override when required via <asm/pgtable.h>.
> All the existing platform that override pmd_pgtable() have been moved into
> their respective <asm/pgtable.h> header in order to precede before the new
> generic definition. This makes it much cleaner with reduced code.

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

Thanks for your patch!

> This patch has been built tested across multiple platforms. But the m68k
> changes in particular might not be optimal, followed the existing switch
> from (arch/m68k/include/asm/pgalloc.h).

Indeed.  Why not move them to the existing
arch/m68k/asm/{sun3,mcf,motorola}_pgtable.h>, instead of introducing
yet another #if/#elif/#else/#endif block?

> --- a/arch/m68k/include/asm/mcf_pgalloc.h
> +++ b/arch/m68k/include/asm/mcf_pgalloc.h
> @@ -32,8 +32,6 @@ extern inline pmd_t *pmd_alloc_kernel(pgd_t *pgd, unsigned long address)
>
>  #define pmd_populate_kernel pmd_populate
>
> -#define pmd_pgtable(pmd) pfn_to_virt(pmd_val(pmd) >> PAGE_SHIFT)
> -
>  static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pgtable,
>                                   unsigned long address)
>  {
> diff --git a/arch/m68k/include/asm/motorola_pgalloc.h b/arch/m68k/include/asm/motorola_pgalloc.h
> index b4fc3b4f6bb3..74a817d9387f 100644
> --- a/arch/m68k/include/asm/motorola_pgalloc.h
> +++ b/arch/m68k/include/asm/motorola_pgalloc.h
> @@ -88,7 +88,6 @@ static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd, pgtable_t page
>  {
>         pmd_set(pmd, page);
>  }
> -#define pmd_pgtable(pmd) ((pgtable_t)pmd_page_vaddr(pmd))
>
>  static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
>  {
> diff --git a/arch/m68k/include/asm/pgtable.h b/arch/m68k/include/asm/pgtable.h
> index ad15d655a9bf..7be5e5e712b2 100644
> --- a/arch/m68k/include/asm/pgtable.h
> +++ b/arch/m68k/include/asm/pgtable.h
> @@ -4,3 +4,12 @@
>  #else
>  #include <asm/pgtable_mm.h>
>  #endif
> +
> +
> +#if defined(CONFIG_COLDFIRE)
> +#define pmd_pgtable(pmd) pfn_to_virt(pmd_val(pmd) >> PAGE_SHIFT)
> +#elif defined(CONFIG_SUN3)
> +#define pmd_pgtable(pmd) pmd_page(pmd)
> +#else
> +#define pmd_pgtable(pmd) ((pgtable_t)pmd_page_vaddr(pmd))
> +#endif
> diff --git a/arch/m68k/include/asm/sun3_pgalloc.h b/arch/m68k/include/asm/sun3_pgalloc.h
> index 000f64869b91..198036aff519 100644
> --- a/arch/m68k/include/asm/sun3_pgalloc.h
> +++ b/arch/m68k/include/asm/sun3_pgalloc.h
> @@ -32,7 +32,6 @@ static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd, pgtable_t page
>  {
>         pmd_val(*pmd) = __pa((unsigned long)page_address(page));
>  }
> -#define pmd_pgtable(pmd) pmd_page(pmd)
>
>  /*
>   * allocating and freeing a pmd is trivial: the 1-entry pmd is

Gr{oetje,eeting}s,

                        Geert

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