linux-kernel - Re: [PATCH] mm: Remove src/dst mm parameter in copy_page

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Date:   Fri, 2 Oct 2020 08:43:12 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH] mm: Remove src/dst mm parameter in copy_page_range()

On Wed, Sep 30, 2020 at 04:49:50PM -0400, Peter Xu wrote:
> Both of the mm pointers are not needed after commit 7a4830c380f3 ("mm/fork:
> Pass new vma pointer into copy_page_range()").
> 
> Reported-by: Kirill A. Shutemov <kirill@...temov.name>
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  include/linux/mm.h |  3 +--
>  kernel/fork.c      |  2 +-
>  mm/memory.c        | 43 ++++++++++++++++++++++---------------------
>  3 files changed, 24 insertions(+), 24 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 16b799a0522c..8a0ec8dce5f6 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1645,8 +1645,7 @@ struct mmu_notifier_range;
>  
>  void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
>  		unsigned long end, unsigned long floor, unsigned long ceiling);
> -int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
> -		    struct vm_area_struct *vma, struct vm_area_struct *new);
> +int copy_page_range(struct vm_area_struct *vma, struct vm_area_struct *new);
>  int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
>  		   struct mmu_notifier_range *range,
>  		   pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
> diff --git a/kernel/fork.c b/kernel/fork.c
> index da8d360fb032..5f42d4afe0ae 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -589,7 +589,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
>  
>  		mm->map_count++;
>  		if (!(tmp->vm_flags & VM_WIPEONFORK))
> -			retval = copy_page_range(mm, oldmm, mpnt, tmp);
> +			retval = copy_page_range(mpnt, tmp);
>  
>  		if (tmp->vm_ops && tmp->vm_ops->open)
>  			tmp->vm_ops->open(tmp);
> diff --git a/mm/memory.c b/mm/memory.c
> index fcfc4ca36eba..251bb5082f4e 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -957,11 +957,12 @@ page_copy_prealloc(struct mm_struct *src_mm, struct vm_area_struct *vma,
>  	return new_page;
>  }
>  
> -static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> -		   pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
> -		   struct vm_area_struct *new,
> +static int copy_pte_range(pmd_t *dst_pmd, pmd_t *src_pmd,
> +		   struct vm_area_struct *vma, struct vm_area_struct *new,
>  		   unsigned long addr, unsigned long end)

I link this, my only minor quibble is the mixing of dst/src and new
language, and then reversing the order in each place. Would read
better to be consistent:

  copy_pte_range(dst_vma, dst_pmd, src_vma, src_pmd, addr, end)

Regards,
Jason