[PATCH 2/3] mm, compaction: cover all compaction mode in compact_zone

[Michal Hocko]

From: Michal Hocko <mhocko@xxxxxxxx>

the compiler is complaining after "mm, compaction: change COMPACT_
constants into enum"

mm/compaction.c: In function âcompact_zoneâ:
mm/compaction.c:1350:2: warning: enumeration value âCOMPACT_DEFERREDâ not handled in switch [-Wswitch]
  switch (ret) {
  ^
mm/compaction.c:1350:2: warning: enumeration value âCOMPACT_COMPLETEâ not handled in switch [-Wswitch]
mm/compaction.c:1350:2: warning: enumeration value âCOMPACT_NO_SUITABLE_PAGEâ not handled in switch [-Wswitch]
mm/compaction.c:1350:2: warning: enumeration value âCOMPACT_NOT_SUITABLE_ZONEâ not handled in switch [-Wswitch]
mm/compaction.c:1350:2: warning: enumeration value âCOMPACT_CONTENDEDâ not handled in switch [-Wswitch]

compaction_suitable is allowed to return only COMPACT_PARTIAL,
COMPACT_SKIPPED and COMPACT_CONTINUE so other cases are simply
impossible. Put a VM_BUG_ON to catch an impossible return value.

Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 mm/compaction.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 0f61f12d82b6..86968d3a04e6 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1347,15 +1347,12 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
 
 	ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
 							cc->classzone_idx);
-	switch (ret) {
-	case COMPACT_PARTIAL:
-	case COMPACT_SKIPPED:
-		/* Compaction is likely to fail */
+	/* Compaction is likely to fail */
+	if (ret == COMPACT_PARTIAL || ret == COMPACT_SKIPPED)
 		return ret;
-	case COMPACT_CONTINUE:
-		/* Fall through to compaction */
-		;
-	}
+
+	/* huh, compaction_suitable is returning something unexpected */
+	VM_BUG_ON(ret != COMPACT_CONTINUE);
 
 	/*
 	 * Clear pageblock skip if there were failures recently and compaction
-- 
2.7.0