This is v2 of [1] with changed subject:
"[PATCH v1 0/5] s390: page_mapcount(), page_has_private() and PG_arch_1"
Rebased on s390x/features which contains the page_mapcount() and
page_has_private() cleanups, and some PG_arch_1 cleanups from Willy. To
compensate, I added some more cleanups ;)
One "easy" fix upfront. Another issue I spotted is documented in [1].
Once this hits upstream, we can remove HAVE_ARCH_MAKE_PAGE_ACCESSIBLE
from core-mm and s390x, so only the folio variant will remain.