mm/compaction: respect ignore_skip_hint in update_pageblock_skip

update_pageblock_skip() only fits to compaction which tries to isolate
by pageblock unit.  If isolate_migratepages_range() is called by CMA, it
try to isolate regardless of pageblock unit and it don't reference
get_pageblock_skip() by ignore_skip_hint.  We should also respect it on
update_pageblock_skip() to prevent from setting the wrong information.

Signed-off-by: Joonsoo Kim <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Reviewed-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Wanpeng Li <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Rafael Aquini <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Zhang Yanfei <[email protected]>
Cc: <[email protected]>	[3.7+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/compaction.c

@@ -134,6 +134,10 @@ static void update_pageblock_skip(struct compact_control *cc,
 			bool migrate_scanner)
 {
 	struct zone *zone = cc->zone;
+
+	if (cc->ignore_skip_hint)
+		return;
+
 	if (!page)
 		return;