mm: memory: add vm_normal_folio_pmd()

mm: memory: add vm_normal_folio_pmd()

Patch series "mm: convert numa balancing functions to use a folio", v2.

do_numa_pages() only handles non-compound pages, and only PMD-mapped THPs
are handled in do_huge_pmd_numa_page().  But a large, PTE-mapped folio
will be supported so let's convert more numa balancing functions to
use/take a folio in preparation for that, no functional change intended
for now.

This patch (of 6):

The new vm_normal_folio_pmd() wrapper is similar to vm_normal_folio(),
which allow them to completely replace the struct page variables with
struct folio variables.

Link: https://lkml.kernel.org/r/20230921074417.24004-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20230921074417.24004-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>