folio_prealloc
prealloc = folio_prealloc(src_mm, src_vma, addr, false);
new_folio = folio_prealloc(mm, vma, vmf->address, pfn_is_zero);
return folio_prealloc(vma->vm_mm, vma, vmf->address, true);
folio = folio_prealloc(vma->vm_mm, vma, vmf->address, false);