Re: [PATCH 11/16] mm: consolidate the get_user_pages* implementations

[Jason Gunthorpe]

On Tue, Jun 25, 2019 at 09:56:50AM +0200, Christoph Hellwig wrote:
> On Fri, Jun 21, 2019 at 11:41:31AM -0300, Jason Gunthorpe wrote:
> > >  static bool gup_fast_permitted(unsigned long start, unsigned long end)
> > >  {
> > > -	return true;
> > > +	return IS_ENABLED(CONFIG_HAVE_FAST_GUP) ? true : false;
> > 
> > The ?: is needed with IS_ENABLED?
> 
> It shouldn't, I'll fix it up.
> 
> > I'd suggest to revise this block a tiny bit:
> > 
> > -#ifndef gup_fast_permitted
> > +#if !IS_ENABLED(CONFIG_HAVE_FAST_GUP) || !defined(gup_fast_permitted)
> >  /*
> >   * Check if it's allowed to use __get_user_pages_fast() for the range, or
> >   * we need to fall back to the slow version:
> >   */
> > -bool gup_fast_permitted(unsigned long start, int nr_pages)
> > +static bool gup_fast_permitted(unsigned long start, int nr_pages)
> >  {
> > 
> > Just in case some future arch code mismatches the header and kconfig..
> 
> IS_ENABLED outside a function doesn't really make sense.  But I'll
> just life the IS_ENABLED(CONFIG_HAVE_FAST_GUP) checks into the two
> callers.

I often see '#if IS_ENABLED(CONFIG_X)', IIRC last I looked at that, it
was needed because the usual #ifdef CONFIG_X didn't work if the value
was =m?

Would be interested to know if that is not the right way to use
kconfig

Jason