Re: [PATCH v2 1/2] mm: Use a folio in the softleaf_is_device_private path

[Hongfu Li <hongfu.li@linux.dev>]

> >  mm/memory.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/memory.c b/mm/memory.c
> > index d5e87624f692..ae521baa8c84 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -4871,18 +4871,19 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> >  				goto unlock;
> >
> 
> Up here we have:
> 
> 			vmf->page = softleaf_to_page(entry);
> 			vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
> 					vmf->address, &vmf->ptl);
> 			if (unlikely(!vmf->pte ||
> 				     !pte_same(ptep_get(vmf->pte),
> 							vmf->orig_pte)))
> 
> Since we're canonicalising to folio why not actually set folio using
> softleaf_to_folio()?
> 
> So
> 
> +			folio = softleaf_to_folio(entry);
> -			vmf->page = softleaf_to_page(entry);
> +			vmf->page = &folio->page;
> 
> This would also make more sense in your 2/2. But more on that in a sec.

Thanks, I've thought through your suggestion carefully.

Could entry reference a tail page of a folio here? 
If so, softleaf_to_folio() retrieves the folio containing this page,
and vmf->page = &folio->page would point to the folio's head page,
which may not be correct.

Best regards,
Hongfu