mm: compaction: make compact_control order signed

"order" is -1 when compacting via /proc/sys/vm/compact_memory.  Making
it unsigned causes a bug in __compact_pgdat() when we test:

	if (cc->order < 0 || !compaction_deferred(zone, cc->order))
		compact_zone(zone, cc);

[akpm@linux-foundation.org: make __compact_pgdat()'s comparison match other code sites]
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index a08bf219f88c..74a8c825ff28 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -35,7 +35,7 @@ struct compact_control {
         unsigned long migrate_pfn;      /* isolate_migratepages search base */
         bool sync;                      /* Synchronous migration */
 
-        unsigned int order;             /* order a direct compactor needs */
+        int order;                      /* order a direct compactor needs */
         int migratetype;                /* MOVABLE, RECLAIMABLE etc */
         struct zone *zone;
 };
@@ -692,7 +692,7 @@ static int __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
                 INIT_LIST_HEAD(&cc->freepages);
                 INIT_LIST_HEAD(&cc->migratepages);
 
-                if (cc->order < 0 || !compaction_deferred(zone, cc->order))
+                if (cc->order == -1 || !compaction_deferred(zone, cc->order))
                         compact_zone(zone, cc);
 
                 if (cc->order > 0) {