linux-kernel - Re: [PATCHv4 39/39] thp: map file-backed huge pages on fault

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Date:	Thu, 23 May 2013 19:36:43 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Dave Hansen <dave@...1.net>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 39/39] thp: map file-backed huge pages on fault

On Sun, May 12, 2013 at 9:23 AM, Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
>
> Look like all pieces are in place, we can map file-backed huge-pages
> now.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  include/linux/huge_mm.h |    4 +++-
>  mm/memory.c             |    5 ++++-
>  2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index f4d6626..903f097 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -78,7 +78,9 @@ extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
>            (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG) &&                   \
>            ((__vma)->vm_flags & VM_HUGEPAGE))) &&                       \
>          !((__vma)->vm_flags & VM_NOHUGEPAGE) &&                        \
> -        !is_vma_temporary_stack(__vma))
> +        !is_vma_temporary_stack(__vma) &&                              \
> +        (!(__vma)->vm_ops ||                                           \
> +                 mapping_can_have_hugepages((__vma)->vm_file->f_mapping)))

Redefine, why?

>  #define transparent_hugepage_defrag(__vma)                             \
>         ((transparent_hugepage_flags &                                  \
>           (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)) ||                     \
> diff --git a/mm/memory.c b/mm/memory.c
> index ebff552..7fe9752 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3939,10 +3939,13 @@ retry:
>         if (!pmd)
>                 return VM_FAULT_OOM;
>         if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
> -               int ret = 0;
> +               int ret;
>                 if (!vma->vm_ops)
>                         ret = do_huge_pmd_anonymous_page(mm, vma, address,
>                                         pmd, flags);

Ah vma->vm_ops is checked here, so
		else if (mapping_can_have_hugepages())

> +               else
> +                       ret = do_huge_linear_fault(mm, vma, address,
> +                                       pmd, flags);
>                 if ((ret & VM_FAULT_FALLBACK) == 0)
>                         return ret;
>         } else {
> --
> 1.7.10.4
>
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