linux-kernel - Re: [PATCH v2] mm: clean up redundant code

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Message-ID: <CAGsJ_4yLyXefpjycf05MYEnUis1UkEmH+kKVeKDnCsZzgGNUMw@mail.gmail.com>
Date: Fri, 9 May 2025 14:44:25 +1200
From: Barry Song <21cnbao@...il.com>
To: Feng Lee <379943137@...com>
Cc: david@...hat.com, akpm@...ux-foundation.org, mingo@...nel.org, 
	jgg@...pe.ca, jhubbard@...dia.com, peterx@...hat.com, maobibo@...ngson.cn, 
	trivial@...nel.org, linux-kernel@...r.kernel.org, lance.yang@...ux.dev, 
	anshuman.khandual@....com
Subject: Re: [PATCH v2] mm: clean up redundant code

On Fri, May 9, 2025 at 1:54 PM Feng Lee <379943137@...com> wrote:
>
> Remove pgd_offset_gate() completely and simply make the single
> caller use pgd_offset()

 "."

>
> It appears that the gate area resides in the kernel-mapped segment
> exclusively on IA64. Therefore, removing pgd_offset_k is safe since
> IA64 is now obsolete.
>
> Signed-off-by: Feng Lee <379943137@...com>
>

Better to rename the subject to be more specific, e.g.  "mm: remove
obsolete  pgd_offset_gate()" or similar. Otherwise,

Reviewed-by: Barry Song <baohua@...nel.org>

> ---
> Changes in v2:
>   - remove pgd_offset_gate completely
>   - remove pgd_offset_k from the get_gate_page function completely
> ---
>  include/linux/pgtable.h | 4 ----
>  mm/gup.c                | 5 +----
>  2 files changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index b50447ef1c92..f1e890b60460 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -1164,10 +1164,6 @@ static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
>  }
>  #endif
>
> -#ifndef __HAVE_ARCH_PGD_OFFSET_GATE
> -#define pgd_offset_gate(mm, addr)      pgd_offset(mm, addr)
> -#endif
> -
>  #ifndef __HAVE_ARCH_MOVE_PTE
>  #define move_pte(pte, old_addr, new_addr)      (pte)
>  #endif
> diff --git a/mm/gup.c b/mm/gup.c
> index f32168339390..0685403fe510 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1101,10 +1101,7 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
>         /* user gate pages are read-only */
>         if (gup_flags & FOLL_WRITE)
>                 return -EFAULT;
> -       if (address > TASK_SIZE)
> -               pgd = pgd_offset_k(address);
> -       else
> -               pgd = pgd_offset_gate(mm, address);
> +       pgd = pgd_offset(mm, address);
>         if (pgd_none(*pgd))
>                 return -EFAULT;
>         p4d = p4d_offset(pgd, address);
> --
> 2.49.0
>

Thanks
barry