lkml.org 
[lkml]   [2007]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] MM: use DIV_ROUND_UP() in mm/memory.c
On Tue, 24 Apr 2007 16:10:22 +0200 Rolf Eike Beer <eike-kernel@sf-tec.de> wrote:

> This should make no difference in behaviour.
>
> Signed-off-by: Rolf Eike Beer <eike-kernel@sf-tec.de>
>
> ---
> commit 64aa7c3136258d3abc76354b5f83b9a9575169c0
> tree 8037adc04b57cd6150456399b7caccf99489385a
> parent bf0bd376f79cadb4f8cd454db1723eb9be0aabc1
> author Rolf Eike Beer <eike-kernel@sf-tec.de> Tue, 24 Apr 2007 16:05:40 +0200
> committer Rolf Eike Beer <eike-kernel@sf-tec.de> Tue, 24 Apr 2007 16:05:40
> +0200
>
> mm/memory.c | 7 +++----
> 1 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e7066e7..45bba1f 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1838,12 +1838,11 @@ void unmap_mapping_range(struct address_space
> *mapping,
> {
> struct zap_details details;
> pgoff_t hba = holebegin >> PAGE_SHIFT;
> - pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
> + pgoff_t hlen = DIV_ROUND_UP(holelen, PAGE_SIZE);
>
> /* Check for overflow. */
> if (sizeof(holelen) > sizeof(hlen)) {
> - long long holeend =
> - (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
> + long long holeend = DIV_ROUND_UP(holebegin + holelen, PAGE_SIZE);
> if (holeend & ~(long long)ULONG_MAX)
> hlen = ULONG_MAX - hba + 1;
> }
> @@ -2592,7 +2591,7 @@ int make_pages_present(unsigned long addr, unsigned long
> end)
> write = (vma->vm_flags & VM_WRITE) != 0;
> BUG_ON(addr >= end);
> BUG_ON(end > vma->vm_end);
> - len = (end+PAGE_SIZE-1)/PAGE_SIZE-addr/PAGE_SIZE;
> + len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;
> ret = get_user_pages(current, current->mm, addr,
> len, write, 0, NULL, NULL);
> if (ret < 0)

The patch is wordwrapped. Please fix your MUA.

More seriously, on i386:

text data bss dec hex filename
15509 27 28 15564 3ccc mm/memory.o (before)
15561 27 28 15616 3d00 mm/memory.o (after)

I'm not sure why - some of the quantities which we're dividing by there are
64-bit and perhaps the compiler has decided not to do shifting.

Please always check the before-and-after .text size from now on?

Now I'm worried about all the other DIV_ROUND_UP() conversions we did. We
should get in there and work out why it went bad.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-05-04 05:31    [W:0.081 / U:1.104 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site