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SubjectRe: [PATCH] mm/mmap.c: optimization of do_mmap_pgoff function
On Sat 06-06-15 11:54:32, Piotr Kwapulinski wrote:
> The simple check for zero length memory mapping may be performed
> earlier. It causes that in case of zero length memory mapping some
> unnecessary code is not executed at all. It does not make the code less
> readable and saves some CPU cycles.
>
> Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>

Acked-by: Michal Hocko <mhocko@suse.cz>

> ---
> mm/mmap.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index bb50cac..aa632ad 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1258,6 +1258,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
>
> *populate = 0;
>
> + if (!len)
> + return -EINVAL;
> +
> /*
> * Does the application expect PROT_READ to imply PROT_EXEC?
> *
> @@ -1268,9 +1271,6 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
> if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
> prot |= PROT_EXEC;
>
> - if (!len)
> - return -EINVAL;
> -
> if (!(flags & MAP_FIXED))
> addr = round_hint_to_min(addr);
>
> --
> 2.3.7
>

--
Michal Hocko
SUSE Labs


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