Re: [PATCH 02/30] mm: add kdoc comments for vma_start/last_pgoff()

On Tue, Jul 07, 2026 at 04:46:13PM +0200, David Hildenbrand (Arm) wrote:
> On 6/29/26 14:23, Lorenzo Stoakes wrote:
> > Describe what vma_start_pgoff() and vma_last_pgoff() actually provide in
> > detail.
> >
> > This is in order that we can differentiate this between functions that will
> > be added in a subsequent patch which provide a different page offset.
> >
> > No functional change intended.
> >
> > Signed-off-by: Lorenzo Stoakes <[email protected]>
> > ---
> >  include/linux/mm.h | 26 ++++++++++++++++++++++++++
> >  1 file changed, 26 insertions(+)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 059144435729..2f00c75e66bd 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -4278,11 +4278,37 @@ static inline unsigned long vma_pages(const struct vm_area_struct *vma)
> >  	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> >  }
> >
> > +/**
> > + * vma_start_pgoff() - Get the page offset of the start of @vma
> > + * @vma: The VMA whose page offset is required.
> > + *
> > + * If the VMA is file-backed, this is the page offset into the file.
> > + *
> > + * If the VMA is anonymous, this is the virtual page offset of the start of the
> > + * VMA - if unfaulted, then vma->vm_start >> PAGE_SHIFT, if faulted then the
> > + * virtual page offset at the time of first fault.
> > + *
> > + * Note that if @vma is a MAP_PRIVATE file-backed mapping, then this returns the
> > + * file offset.
>
> There is the ugly case of @vma being a MAP_PRIVATE PFNMAP mapping, where it
> returns something different.

Yup, the pfn  I will update doc to mention this abomination too.

The virt pgoff stuff in the RFC fixes this also.

>
> (remap_pfn_range_prepare_vma() -> vma->vm_pgoff set to PFN)
>
> --
> Cheers,
>
> David

Cheers, Lorenzo