Re: [PATCH v3 6/6] mm/hugetlb: remove unused argument of follow_huge_addr()

[Hugh Dickins <hughd@google.com>]

On Thu, 28 Aug 2014, Naoya Horiguchi wrote:

> follow_huge_addr()'s parameter write is not used, so let's remove it.
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

I think this patch is a waste of time: that it should be replaced
by a patch which replaces the "write" argument by a "flags" argument,
so that follow_huge_addr() can do get_page() for FOLL_GET while holding
appropriate lock, instead of the BUG_ON(flags & FOLL_GET) we currently
have.

Once that is implemented, you could try getting hugetlb migration
tested on ia64 and powerpc; but yes, keep hugetlb migration disabled
on all but x86 until it has been tested elsewhere.

> ---
>  arch/ia64/mm/hugetlbpage.c    | 2 +-
>  arch/powerpc/mm/hugetlbpage.c | 2 +-
>  arch/x86/mm/hugetlbpage.c     | 2 +-
>  include/linux/hugetlb.h       | 5 ++---
>  mm/gup.c                      | 2 +-
>  mm/hugetlb.c                  | 3 +--
>  6 files changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git mmotm-2014-08-25-16-52.orig/arch/ia64/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/ia64/mm/hugetlbpage.c
> index 6170381bf074..524a4e001bda 100644
> --- mmotm-2014-08-25-16-52.orig/arch/ia64/mm/hugetlbpage.c
> +++ mmotm-2014-08-25-16-52/arch/ia64/mm/hugetlbpage.c
> @@ -89,7 +89,7 @@ int prepare_hugepage_range(struct file *file,
>  	return 0;
>  }
>  
> -struct page *follow_huge_addr(struct mm_struct *mm, unsigned long addr, int write)
> +struct page *follow_huge_addr(struct mm_struct *mm, unsigned long addr)
>  {
>  	struct page *page = NULL;
>  	pte_t *ptep;
> diff --git mmotm-2014-08-25-16-52.orig/arch/powerpc/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/powerpc/mm/hugetlbpage.c
> index 1d8854a56309..5b6fe8b0cde3 100644
> --- mmotm-2014-08-25-16-52.orig/arch/powerpc/mm/hugetlbpage.c
> +++ mmotm-2014-08-25-16-52/arch/powerpc/mm/hugetlbpage.c
> @@ -674,7 +674,7 @@ void hugetlb_free_pgd_range(struct mmu_gather *tlb,
>  }
>  
>  struct page *
> -follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
> +follow_huge_addr(struct mm_struct *mm, unsigned long address)
>  {
>  	pte_t *ptep;
>  	struct page *page = ERR_PTR(-EINVAL);
> diff --git mmotm-2014-08-25-16-52.orig/arch/x86/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/x86/mm/hugetlbpage.c
> index 03b8a7c11817..cab09d87ae65 100644
> --- mmotm-2014-08-25-16-52.orig/arch/x86/mm/hugetlbpage.c
> +++ mmotm-2014-08-25-16-52/arch/x86/mm/hugetlbpage.c
> @@ -18,7 +18,7 @@
>  
>  #if 0	/* This is just for testing */
>  struct page *
> -follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
> +follow_huge_addr(struct mm_struct *mm, unsigned long address)
>  {
>  	unsigned long start = address;
>  	int length = 1;
> diff --git mmotm-2014-08-25-16-52.orig/include/linux/hugetlb.h mmotm-2014-08-25-16-52/include/linux/hugetlb.h
> index b3200fce07aa..cdff1bd393bb 100644
> --- mmotm-2014-08-25-16-52.orig/include/linux/hugetlb.h
> +++ mmotm-2014-08-25-16-52/include/linux/hugetlb.h
> @@ -96,8 +96,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
>  			unsigned long addr, unsigned long sz);
>  pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr);
>  int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep);
> -struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
> -			      int write);
> +struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address);
>  struct page *follow_huge_pmd(struct vm_area_struct *vma, unsigned long address,
>  				pmd_t *pmd, int flags);
>  struct page *follow_huge_pud(struct vm_area_struct *vma, unsigned long address,
> @@ -124,7 +123,7 @@ static inline unsigned long hugetlb_total_pages(void)
>  }
>  
>  #define follow_hugetlb_page(m,v,p,vs,a,b,i,w)	({ BUG(); 0; })
> -#define follow_huge_addr(mm, addr, write)	ERR_PTR(-EINVAL)
> +#define follow_huge_addr(mm, addr)	ERR_PTR(-EINVAL)
>  #define copy_hugetlb_page_range(src, dst, vma)	({ BUG(); 0; })
>  static inline void hugetlb_report_meminfo(struct seq_file *m)
>  {
> diff --git mmotm-2014-08-25-16-52.orig/mm/gup.c mmotm-2014-08-25-16-52/mm/gup.c
> index 597a5e92e265..8f0550f1770d 100644
> --- mmotm-2014-08-25-16-52.orig/mm/gup.c
> +++ mmotm-2014-08-25-16-52/mm/gup.c
> @@ -149,7 +149,7 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
>  
>  	*page_mask = 0;
>  
> -	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
> +	page = follow_huge_addr(mm, address);
>  	if (!IS_ERR(page)) {
>  		BUG_ON(flags & FOLL_GET);
>  		return page;
> diff --git mmotm-2014-08-25-16-52.orig/mm/hugetlb.c mmotm-2014-08-25-16-52/mm/hugetlb.c
> index 0a4511115ee0..f7dcad3474ec 100644
> --- mmotm-2014-08-25-16-52.orig/mm/hugetlb.c
> +++ mmotm-2014-08-25-16-52/mm/hugetlb.c
> @@ -3690,8 +3690,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
>   * behavior.
>   */
>  struct page * __weak
> -follow_huge_addr(struct mm_struct *mm, unsigned long address,
> -			      int write)
> +follow_huge_addr(struct mm_struct *mm, unsigned long address)
>  {
>  	return ERR_PTR(-EINVAL);
>  }
> -- 
> 1.9.3

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