linux-kernel - Re: [PATCH 09/18] ARC: mm: non-functional code cleanup ahead of 3 levels

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Message-ID: <YRPDL90Qr5RLDmnT@kernel.org>
Date:   Wed, 11 Aug 2021 15:31:43 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Vineet Gupta <vgupta@...nel.org>
Cc:     linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH 09/18] ARC: mm: non-functional code cleanup ahead of 3
 levels

On Tue, Aug 10, 2021 at 05:42:49PM -0700, Vineet Gupta wrote:
> Signed-off-by: Vineet Gupta <vgupta@...nel.org>
> ---
>  arch/arc/include/asm/page.h    | 30 ++++++++++++++++--------------
>  arch/arc/include/asm/pgalloc.h |  7 ++++++-
>  2 files changed, 22 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
> index c4ac827379cd..313e6f543d2d 100644
> --- a/arch/arc/include/asm/page.h
> +++ b/arch/arc/include/asm/page.h
> @@ -34,6 +34,13 @@ void copy_user_highpage(struct page *to, struct page *from,
>  			unsigned long u_vaddr, struct vm_area_struct *vma);
>  void clear_user_page(void *to, unsigned long u_vaddr, struct page *page);
>  
> +typedef struct {
> +	unsigned long pgd;
> +} pgd_t;
> +
> +#define pgd_val(x)	((x).pgd)
> +#define __pgd(x)	((pgd_t) { (x) })
> +
>  typedef struct {
>  #ifdef CONFIG_ARC_HAS_PAE40
>  	unsigned long long pte;
> @@ -41,22 +48,17 @@ typedef struct {
>  	unsigned long pte;
>  #endif
>  } pte_t;
> -typedef struct {
> -	unsigned long pgd;
> -} pgd_t;
> +
> +#define pte_val(x)	((x).pte)
> +#define __pte(x)	((pte_t) { (x) })
> +
>  typedef struct {
>  	unsigned long pgprot;
>  } pgprot_t;
>  
> -#define pte_val(x)      ((x).pte)
> -#define pgd_val(x)      ((x).pgd)
> -#define pgprot_val(x)   ((x).pgprot)
> -
> -#define __pte(x)        ((pte_t) { (x) })
> -#define __pgd(x)        ((pgd_t) { (x) })
> -#define __pgprot(x)     ((pgprot_t) { (x) })
> -
> -#define pte_pgprot(x) __pgprot(pte_val(x))
> +#define pgprot_val(x)	((x).pgprot)
> +#define __pgprot(x)	((pgprot_t) { (x) })
> +#define pte_pgprot(x)	__pgprot(pte_val(x))
>  
>  typedef pte_t * pgtable_t;
>  
> @@ -96,8 +98,8 @@ extern int pfn_valid(unsigned long pfn);
>   * virt here means link-address/program-address as embedded in object code.
>   * And for ARC, link-addr = physical address
>   */
> -#define __pa(vaddr)  ((unsigned long)(vaddr))
> -#define __va(paddr)  ((void *)((unsigned long)(paddr)))
> +#define __pa(vaddr)  		((unsigned long)(vaddr))
> +#define __va(paddr)  		((void *)((unsigned long)(paddr)))
>  
>  #define virt_to_page(kaddr)	pfn_to_page(virt_to_pfn(kaddr))
>  #define virt_addr_valid(kaddr)  pfn_valid(virt_to_pfn(kaddr))
> diff --git a/arch/arc/include/asm/pgalloc.h b/arch/arc/include/asm/pgalloc.h
> index 356237b9c537..0cf73431eb89 100644
> --- a/arch/arc/include/asm/pgalloc.h
> +++ b/arch/arc/include/asm/pgalloc.h
> @@ -29,6 +29,11 @@
>  #ifndef _ASM_ARC_PGALLOC_H
>  #define _ASM_ARC_PGALLOC_H
>  
> +/*
> + * For ARC, pgtable_t is not struct page *, but pte_t * (to avoid
> + * extraneous page_address() calculations) hence can't use
> + * use asm-generic/pgalloc.h which assumes it being struct page *
> + */

Another reason to leave ARC without asm-generic/pgalloc.h was
__get_order_pte() that other arches don't have.
So this and pgtable_t aliased to pte_t * seemed to me too much to bother
then, but probably it's worth reconsidering with addition of 3rd and 4th
levels.

>  #include <linux/mm.h>
>  #include <linux/log2.h>
>  
> @@ -36,7 +41,7 @@ static inline void
>  pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep)
>  {
>  	/*
> -	 * The cast to long below is OK even when pte is long long (PAE40)
> +	 * The cast to long below is OK in 32-bit PAE40 regime with long long pte
>  	 * Despite "wider" pte, the pte table needs to be in non-PAE low memory
>  	 * as all higher levels can only hold long pointers.
>  	 *
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.