Re: [PATCHv3 1/2] mm: introduce vm_ops->map_pages()

[Kirill A. Shutemov]

On Mon, Mar 03, 2014 at 03:16:11PM -0800, Andrew Morton wrote:
> On Thu, 27 Feb 2014 21:53:46 +0200 "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> 
> > The patch introduces new vm_ops callback ->map_pages() and uses it for
> > mapping easy accessible pages around fault address.
> > 
> > On read page fault, if filesystem provides ->map_pages(), we try to map
> > up to FAULT_AROUND_PAGES pages around page fault address in hope to
> > reduce number of minor page faults.
> > 
> > We call ->map_pages first and use ->fault() as fallback if page by the
> > offset is not ready to be mapped (cold page cache or something).
> >
> > ...
> >
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> >
> > ...
> >
> > @@ -571,6 +576,9 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
> >  		pte = pte_mkwrite(pte);
> >  	return pte;
> >  }
> > +
> > +void do_set_pte(struct vm_area_struct *vma, unsigned long address,
> > +		struct page *page, pte_t *pte, bool write, bool anon);
> >  #endif
> >  
> >  /*
> 
> lguest made a dubious naming decision:
> 
> drivers/lguest/page_tables.c:890: error: conflicting types for 'do_set_pte'
> include/linux/mm.h:593: note: previous declaration of 'do_set_pte' was here
> 
> I'll rename lguest's do_set_pte() to do_guest_set_pte() as a
> preparatory patch.

Thanks.

> btw, do_set_pte() could really do with some documentation.  It's not a
> trivial function and it does a lot of stuff.  It's exported to other
> compilation units and we should explain the what, the why and
> particularly the locking preconditions.

Like this?