linux-kernel - Re: [RFC PATCH] mm: mincore: use PAGE_SIZE instead of PAGE_CACHE

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Date:	Wed, 10 Dec 2014 23:02:46 +0800
From:	Weijie Yang <weijie.yang.kh@...il.com>
To:	Weijie Yang <weijie.yang@...sung.com>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Linux-MM <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] mm: mincore: use PAGE_SIZE instead of PAGE_CACHE_SIZE

ping. Any comments?

On Wed, Nov 12, 2014 at 5:50 PM, Weijie Yang <weijie.yang@...sung.com> wrote:
> This is a RFC patch, because current PAGE_SIZE is equal to PAGE_CACHE_SIZE,
> there isn't any difference and issue when running.
>
> However, the current code mixes these two aligned_size inconsistently, and if
> they are not equal in future mincore_unmapped_range() would check more file
> pages than wanted.
>
> According to man-page, mincore uses PAGE_SIZE as its size unit, so this patch
> uses PAGE_SIZE instead of PAGE_CACHE_SIZE.
>
> Signed-off-by: Weijie Yang <weijie.yang@...sung.com>
> ---
>  mm/mincore.c |   19 +++++++++++++------
>  1 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/mm/mincore.c b/mm/mincore.c
> index 725c809..8c19bce 100644
> --- a/mm/mincore.c
> +++ b/mm/mincore.c
> @@ -102,11 +102,18 @@ static void mincore_unmapped_range(struct vm_area_struct *vma,
>         int i;
>
>         if (vma->vm_file) {
> -               pgoff_t pgoff;
> +               pgoff_t pgoff, pgoff_end;
> +               int j, count;
> +               unsigned char res;
>
> +               count = 1 << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
>                 pgoff = linear_page_index(vma, addr);
> -               for (i = 0; i < nr; i++, pgoff++)
> -                       vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
> +               pgoff_end = linear_page_index(vma, end);
> +               for (i = 0; pgoff < pgoff_end; pgoff++) {
> +                       res = mincore_page(vma->vm_file->f_mapping, pgoff);
> +                       for (j = 0; j < count; j++)
> +                               vec[i++] = res;
> +               }
>         } else {
>                 for (i = 0; i < nr; i++)
>                         vec[i] = 0;
> @@ -258,7 +265,7 @@ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *v
>   * return values:
>   *  zero    - success
>   *  -EFAULT - vec points to an illegal address
> - *  -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
> + *  -EINVAL - addr is not a multiple of PAGE_SIZE
>   *  -ENOMEM - Addresses in the range [addr, addr + len] are
>   *             invalid for the address space of this process, or
>   *             specify one or more pages which are not currently
> @@ -273,14 +280,14 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
>         unsigned char *tmp;
>
>         /* Check the start address: needs to be page-aligned.. */
> -       if (start & ~PAGE_CACHE_MASK)
> +       if (start & ~PAGE_MASK)
>                 return -EINVAL;
>
>         /* ..and we need to be passed a valid user-space range */
>         if (!access_ok(VERIFY_READ, (void __user *) start, len))
>                 return -ENOMEM;
>
> -       /* This also avoids any overflows on PAGE_CACHE_ALIGN */
> +       /* This also avoids any overflows on PAGE_ALIGN */
>         pages = len >> PAGE_SHIFT;
>         pages += (len & ~PAGE_MASK) != 0;
>
> --
> 1.7.0.4
>
>
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