Re: [PATCH 2/2] mm: madvise: make MADV_NOHUGEPAGE a no-op if !THP

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

* Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [250516 11:43]:
> On Fri, May 16, 2025 at 11:40:23AM -0400, Liam R. Howlett wrote:
> > * Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [250515 16:15]:
> > > From: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@kuka.com>
> > >
> > > VM_NOHUGEPAGE is a no-op if CONFIG_TRANSPARENT_HUGEPAGE is disabled. So
> > > it makes no sense to return an error when calling madvise() with
> > > MADV_NOHUGEPAGE in that case.
> > >
> > > Suggested-by: Matthew Wilcox <willy@infradead.org>
> > > Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@kuka.com>
> > > Reviewed-by: Yang Shi <yang@os.amperecomputing.com>
> > > Acked-by: David Hildenbrand <david@redhat.com>
> > > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> >
> > Nice to see you review this for yourself :)
> 
> Haha yeah... this is a Lorenzo-getting-confused-by-kernel-process situation
> again, this is 100% Ignacio's patch, I just bundled it up in this series to
> enforce ordering.
> 
> >
> > > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> 
> ...But of course I did format-patch -s so I signed it off as well :P
> 
> At any rate the From: field and Ignacio's S-o-b should make everything correct
> in the wash. I think.
> 
> Andrew - this is Ignacio's patch for avoidance of doubt :P

Oh yes, I missed the initial sign off.  I think this is okay, but maybe
you didn't need your own RB?

> 
> >
> > Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
> >
> > > ---
> > >  include/linux/huge_mm.h | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > >
> > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > > index 2f190c90192d..1a8082c61e01 100644
> > > --- a/include/linux/huge_mm.h
> > > +++ b/include/linux/huge_mm.h
> > > @@ -506,6 +506,8 @@ bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
> > >
> > >  #else /* CONFIG_TRANSPARENT_HUGEPAGE */
> > >
> > > +#include <uapi/asm/mman.h>
> > > +
> > >  static inline bool folio_test_pmd_mappable(struct folio *folio)
> > >  {
> > >  	return false;
> > > @@ -595,6 +597,9 @@ static inline bool unmap_huge_pmd_locked(struct vm_area_struct *vma,
> > >  static inline int hugepage_madvise(struct vm_area_struct *vma,
> > >  				   unsigned long *vm_flags, int advice)
> > >  {
> > > +	/* On a !THP kernel, MADV_NOHUGEPAGE is a no-op, but MADV_HUGEPAGE is not supported */
> > > +	if (advice == MADV_NOHUGEPAGE)
> > > +		return 0;
> > >  	return -EINVAL;
> > >  }
> > >
> > > --
> > > 2.49.0
> > >
> >