Add PFN_PTE_SHIFT, update_mmu_cache_range() and flush_dcache_folio().
Change the PG_dcache_clean flag from being per-page to per-folio.

Link: https://lkml.kernel.org/r/20230802151406.3735276-12-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Guo Ren <guoren@kernel.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>