mm, page_alloc: enable pcpu_drain with zone capability

drain_all_pages is documented to drain per-cpu pages for a given zone (if
non-NULL).  The current implementation doesn't match the description
though.  It will drain all pcp pages for all zones that happen to have
cached pages on the same cpu as the given zone.  This will lead to
premature pcp cache draining for zones that are not of any interest to the
caller - e.g.  compaction, hwpoison or memory offline.

This forces the page allocator to take locks and potential lock contention
as a result.

There is no real reason for this sub-optimal implementation.  Replace
per-cpu work item with a dedicated structure which contains a pointer to
the zone and pass it over to the worker.  This will get the zone
information all the way down to the worker function and do the right job.

[akpm@linux-foundation.org: avoid 80-col tricks]
[mhocko@suse.com: refactor the whole changelog]
Link: http://lkml.kernel.org/r/20181212142550.61686-1-richard.weiyang@gmail.com


Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>