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

[Lorenzo Stoakes]

On Fri, May 16, 2025 at 11:40:23AM -0400, Liam R. Howlett wrote:
> * Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> [250515 16:15]:
> > From: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@xxxxxxxx>
> >
> > 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@xxxxxxxxxxxxx>
> > Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@xxxxxxxx>
> > Reviewed-by: Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx>
> > Acked-by: David Hildenbrand <david@xxxxxxxxxx>
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>

...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

>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
>
> > ---
> >  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
> >
>