mm: differentiate page_mapped() from page_mapcount() for compound pages

mm: differentiate page_mapped() from page_mapcount() for compound pages

Let's define page_mapped() to be true for compound pages if any
sub-pages of the compound page is mapped (with PMD or PTE).

On other hand page_mapcount() return mapcount for this particular small
page.

This will make cases like page_get_anon_vma() behave correctly once we
allow huge pages to be mapped with PTE.

Most users outside core-mm should use page_mapcount() instead of
page_mapped().

Signed-off-by: Kirill A. Shutemov <[email protected]>
Tested-by: Sasha Levin <[email protected]>
Tested-by: Aneesh Kumar K.V <[email protected]>
Acked-by: Jerome Marchand <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Steve Capper <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>