Revert "mm: have order > 0 compaction start off where it left"

Revert "mm: have order > 0 compaction start off where it left"

This reverts commit 7db8889a ("mm: have order > 0 compaction start off
where it left") and commit de74f1cc ("mm: have order > 0 compaction start
near a pageblock with free pages").  These patches were a good idea and
tests confirmed that they massively reduced the amount of scanning but the
implementation is complex and tricky to understand.  A later patch will
cache what pageblocks should be skipped and reimplements the concept of
compact_cached_free_pfn on top for both migration and free scanners.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Richard Davies <richard@arachsys.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Avi Kivity <avi@redhat.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>