Re: [PATCH 04/10] mm: replace get_user_pages_locked() write/force parameters with gup_flags

Jan Kara
2016-10-18T12:54:25Z

On Thu 13-10-16 01:20:14, Lorenzo Stoakes wrote:
> This patch removes the write and force parameters from get_user_pages_locked()
> and replaces them with a gup_flags parameter to make the use of FOLL_FORCE
> explicit in callers as use of this flag can result in surprising behaviour (and
> hence bugs) within the mm subsystem.
>
> Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
> ---
> include/linux/mm.h | 2 +-
> mm/frame_vector.c | 8 +++++++-
> mm/gup.c | 12 +++---------
> mm/nommu.c | 5 ++++-
> 4 files changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 6adc4bc..27ab538 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1282,7 +1282,7 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
> int write, int force, struct page **pages,
> struct vm_area_struct **vmas);
> long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
> - int write, int force, struct page **pages, int *locked);
> + unsigned int gup_flags, struct page **pages, int *locked);

Hum, the prototype is inconsistent with e.g. __get_user_pages_unlocked()
where gup_flags come after **pages argument. Actually it makes more sense
to have it before **pages so that input arguments come first and output
arguments second but I don't care that much. But it definitely should be
consistent...

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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