mm: mark idle page tracking as BROKEN

mm: mark idle page tracking as BROKEN

In discussion with other MM developers around how idle page tracking
should be fixed for transparent huge pages, several expressed the opinion
that it should be removed as it is inefficient at accomplishing the job
that it is supposed to, and we have better mechanisms (eg uffd) for
accomplishing the same goals these days.

Mark the feature as BROKEN for now and we can remove it entirely in a few
months if nobody complains.  It is not enabled by Android, ChromeOS,
Debian, Fedora or SUSE.  Red Hat enabled it with RHEL-8.1 and UEK followed
suit, but I have been unable to find why RHEL enabled it.

Link: https://lkml.kernel.org/r/20210612000714.775825-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Yu Zhao <yuzhao@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
SeongJae Park <sj38.park@gmail.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>