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>

diff --git a/mm/compaction.c b/mm/compaction.c
index a08bf21..74a8c82 100644 (file)
--- 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) {