On Thu, Apr 09, 2020 at 05:47:44PM +0300, Kirill A. Shutemov wrote:
> On Thu, Apr 09, 2020 at 07:32:38AM -0700, Matthew Wilcox wrote:
> > On Thu, Apr 09, 2020 at 05:28:51PM +0300, Kirill A. Shutemov wrote:
> > > > We have a few places that do things like
> > > >
> > > > mm/filemap.c: if (unlikely(compound_head(page)->mapping != mapping)) {
> > >
> > > Good point.
> > >
> > > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> >
> > Darn, I hoped you'd have a better idea. I feel quite ashamed of this patch.
>
> I had two ideas. Both awful.
>
> - Rename compound_head() to __compound_head() or something and make it
> return void *. Then wrap it into a macro that would cast return type to
> type of the argument. It would allow to regain *some* type safety.
>
> - Provide two implementations and use C11 _Generic() :P
> (bump GCC version requirements first)
I guess a reasonable modification would be to add typechecking to the
macros:
typecheck(const struct page *, page)
Not sure though if it threats const vs non-const as compatible.
--
Kirill A. Shutemov
