mm/compaction.c: fix deferring compaction mistake

Commit aff62249 ("vmscan: only defer compaction for failed order and
higher") fixed bad deferring policy but made mistake about checking
compact_order_failed in __compact_pgdat().  So it can't update
compact_order_failed with the new order.  This ends up preventing
correct operation of policy deferral.  This patch fixes it.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/compaction.c

@@ -861,7 +861,7 @@ static int __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
 		if (cc->order > 0) {
 			int ok = zone_watermark_ok(zone, cc->order,
 						low_wmark_pages(zone), 0, 0);
-			if (ok && cc->order > zone->compact_order_failed)
+			if (ok && cc->order >= zone->compact_order_failed)
 				zone->compact_order_failed = cc->order + 1;
 			/* Currently async compaction is never deferred. */
 			else if (!ok && cc->sync)