Re: [PATCH] mm: check VMA flags to avoid invalid PROT_NONE NUMA balancing

Jan Kara
2016-10-10T16:38:01Z

On Mon 10-10-16 09:28:28, Lorenzo Stoakes wrote:
> On Mon, Oct 10, 2016 at 09:47:12AM +0200, Jan Kara wrote:
> > Yeah, so my cleanups where mostly concerned about mmap_sem locking and
> > reducing number of places which cared about those. Regarding flags for
> > get_user_pages() / get_vaddr_frames(), I agree that using flags argument
> > as Linus suggests will make it easier to see what the callers actually
> > want. So I'm for that.
>
> Great, thanks Jan! I have a draft patch that needs a little tweaking/further
> testing but isn't too far off.
>
> One thing I am wondering about is whether functions that have write/force
> parameters replaced with gup_flags should mask against (FOLL_WRITE | FOLL_FORCE)
> to prevent callers from doing unexpected things with other FOLL_* flags?
>
> I'm inclined _not_ to because it adds a rather non-obvious restriction on this
> parameter, reduces clarity about which flags are actually being used (which is
> the point of the patch in the first place), and the caller ought to know what
> they are doing.

Yeah, just leave flags as is. There is no strong reason to restrict them.

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