linux-kernel - Re: [PATCH V2] mm/thp: Define default pmd

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Date:   Wed, 9 Jun 2021 11:50:48 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        Nick Hu <nickhu@...estech.com>,
        Richard Henderson <rth@...ddle.net>,
        Vineet Gupta <vgupta@...opsys.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Brian Cain <bcain@...eaurora.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Simek <monstr@...str.eu>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Jeff Dike <jdike@...toit.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Chris Zankel <chris@...kel.net>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mm/thp: Define default pmd_pgtable()

Hi Anshuman,

On Wed, Jun 09, 2021 at 10:29:59AM +0530, Anshuman Khandual 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.
> 
> Cc: Nick Hu <nickhu@...estech.com>
> Cc: Richard Henderson <rth@...ddle.net>
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Guo Ren <guoren@...nel.org>
> Cc: Brian Cain <bcain@...eaurora.org>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Michal Simek <monstr@...str.eu>
> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> Cc: Ley Foon Tan <ley.foon.tan@...el.com>
> Cc: Jonas Bonn <jonas@...thpole.se>
> Cc: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
> Cc: Stafford Horne <shorne@...il.com>
> Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Jeff Dike <jdike@...toit.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Chris Zankel <chris@...kel.net>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-arch@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>

One nit below, otherwise

Acked-by: Mike Rapoport <rppt@...ux.ibm.com>

> ---
> This patch applies on linux-next (20210608) as there is a merge conflict
> dependency on the following commit.
> 
> 40762590e8be ("mm: define default value for FIRST_USER_ADDRESS").
> 
> This patch has been built tested across multiple platforms.
> 
> Changes in V2:
> 
> - Changed m68k per Geert
> 
> Changes in V1:
> 
> https://lore.kernel.org/linux-arch/1623130327-13325-1-git-send-email-anshuman.khandual@arm.com/

...

> 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
> diff --git a/arch/m68k/include/asm/sun3_pgtable.h b/arch/m68k/include/asm/sun3_pgtable.h
> index 5b24283a0a42..127282bd8b96 100644
> --- a/arch/m68k/include/asm/sun3_pgtable.h
> +++ b/arch/m68k/include/asm/sun3_pgtable.h
> @@ -96,6 +96,8 @@
>  
>  #ifndef __ASSEMBLY__
>  
> +#define pmd_pgtable(pmd) pmd_page(pmd)
> +

Is this one really needed? Won't the generic definition work instead?

>  /*
>   * Conversion functions: convert a page and protection to a page entry,
>   * and a page entry and page directory to the page they refer to.
> diff --git a/arch/microblaze/include/asm/pgalloc.h b/arch/microblaze/include/asm/pgalloc.h
> index d56b9f670ad1..6c33b05f730f 100644
> --- a/arch/microblaze/include/asm/pgalloc.h
> +++ b/arch/microblaze/include/asm/pgalloc.h
> @@ -28,8 +28,6 @@ static inline pgd_t *get_pgd(void)
>  
>  #define pgd_alloc(mm)		get_pgd()
>  
> -#define pmd_pgtable(pmd)	pmd_page(pmd)
> -
>  extern pte_t *pte_alloc_one_kernel(struct mm_struct *mm);
>  
>  #define __pte_free_tlb(tlb, pte, addr)	pte_free((tlb)->mm, (pte))

-- 
Sincerely yours,
Mike.