Linux page migration code won't wait for writeback to complete unless
it needs to call release_folio. Call SetPagePrivate wherever
PageUptodate is set and define .release_folio, to cause
fallback_migrate_folio to wait for us.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: tstabrawa <59430211+tstabrawa@users.noreply.github.com>
Closes#15140Closes#16568
