mm/rmap: move SetPageAnonExclusive() out of page_move_anon_rmap()

mm/rmap: move SetPageAnonExclusive() out of page_move_anon_rmap()

Patch series "mm/rmap: convert page_move_anon_rmap() to
folio_move_anon_rmap()".

Convert page_move_anon_rmap() to folio_move_anon_rmap(), letting the
callers handle PageAnonExclusive.  I'm including cleanup patch #3 because
it fits into the picture and can be done cleaner by the conversion.

This patch (of 3):

Let's move it into the caller: there is a difference between whether an
anon folio can only be mapped by one process (e.g., into one VMA), and
whether it is truly exclusive (e.g., no references -- including GUP --
from other processes).

Further, for large folios the page might not actually be pointing at the
head page of the folio, so it better be handled in the caller.  This is a
preparation for converting page_move_anon_rmap() to consume a folio.

Link: https://lkml.kernel.org/r/20231002142949.235104-1-david@redhat.com
Link: https://lkml.kernel.org/r/20231002142949.235104-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>