block: enumify ELEVATOR_*_MERGE

Switch these constants to an enum, and make let the compiler ensure that
all callers of blk_try_merge and elv_merge handle all potential values.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 16 insertions, 12 deletions

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index b5825c4f06f7..b38b4e651ea6 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -9,12 +9,21 @@
 struct io_cq;
 struct elevator_type;
 
-typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
+/*
+ * Return values from elevator merger
+ */
+enum elv_merge {
+        ELEVATOR_NO_MERGE       = 0,
+        ELEVATOR_FRONT_MERGE    = 1,
+        ELEVATOR_BACK_MERGE     = 2,
+};
+
+typedef enum elv_merge (elevator_merge_fn) (struct request_queue *, struct request **,
                                  struct bio *);
 
 typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
 
-typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
+typedef void (elevator_merged_fn) (struct request_queue *, struct request *, enum elv_merge);
 
 typedef int (elevator_allow_bio_merge_fn) (struct request_queue *,
                                            struct request *, struct bio *);
@@ -87,7 +96,7 @@ struct elevator_mq_ops {
         bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);
         bool (*bio_merge)(struct blk_mq_hw_ctx *, struct bio *);
         int (*request_merge)(struct request_queue *q, struct request **, struct bio *);
-        void (*request_merged)(struct request_queue *, struct request *, int);
+        void (*request_merged)(struct request_queue *, struct request *, enum elv_merge);
         void (*requests_merged)(struct request_queue *, struct request *, struct request *);
         struct request *(*get_request)(struct request_queue *, unsigned int, struct blk_mq_alloc_data *);
         void (*put_request)(struct request *);
@@ -166,10 +175,12 @@ extern void elv_dispatch_sort(struct request_queue *, struct request *);
 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 extern void elv_add_request(struct request_queue *, struct request *, int);
 extern void __elv_add_request(struct request_queue *, struct request *, int);
-extern int elv_merge(struct request_queue *, struct request **, struct bio *);
+extern enum elv_merge elv_merge(struct request_queue *, struct request **,
+                struct bio *);
 extern void elv_merge_requests(struct request_queue *, struct request *,
                                struct request *);
-extern void elv_merged_request(struct request_queue *, struct request *, int);
+extern void elv_merged_request(struct request_queue *, struct request *,
+                enum elv_merge);
 extern void elv_bio_merged(struct request_queue *q, struct request *,
                                 struct bio *);
 extern bool elv_attempt_insert_merge(struct request_queue *, struct request *);
@@ -219,13 +230,6 @@ extern void elv_rb_del(struct rb_root *, struct request *);
 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 
 /*
- * Return values from elevator merger
- */
-#define ELEVATOR_NO_MERGE       0
-#define ELEVATOR_FRONT_MERGE    1
-#define ELEVATOR_BACK_MERGE     2
-
-/*
  * Insertion selection
  */
 #define ELEVATOR_INSERT_FRONT   1