block: Change the type of req_op() and bio_op() into enum req_op

Improve static type checking by changing the type of the value returned by
req_op() and bio_op() from unsigned int into enum req_op. Insert
'default: break;' in switch statements on the enum req_op type to prevent
that the compiler warns about these switch statements.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Tim Waugh <tim@cyberelk.net>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-5-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -405,6 +405,8 @@ unsigned int blk_recalc_rq_segments(struct request *rq)
 		return 1;
 	case REQ_OP_WRITE_ZEROES:
 		return 0;
+	default:
+		break;
 	}
 
 	rq_for_each_bvec(bv, rq, iter)

drivers/block/paride/pd.c

@@ -501,6 +501,8 @@ static enum action do_pd_io_start(void)
 			return do_pd_read_start();
 		else
 			return do_pd_write_start();
+	default:
+		break;
 	}
 	return Fail;
 }

drivers/md/dm.c

@@ -1542,6 +1542,8 @@ static blk_status_t __process_abnormal_io(struct clone_info *ci,
 	case REQ_OP_WRITE_ZEROES:
 		num_bios = ti->num_write_zeroes_bios;
 		break;
+	default:
+		break;
 	}
 
 	/*

include/linux/blk-mq.h

@@ -198,8 +198,10 @@ struct request {
 	void *end_io_data;
 };
 
-#define req_op(req) \
-	((req)->cmd_flags & REQ_OP_MASK)
+static inline enum req_op req_op(const struct request *req)
+{
+	return req->cmd_flags & REQ_OP_MASK;
+}
 
 static inline bool blk_rq_is_passthrough(struct request *rq)
 {

include/linux/blk_types.h

@@ -463,8 +463,10 @@ enum stat_group {
 	NR_STAT_GROUPS
 };
 
-#define bio_op(bio) \
-	((bio)->bi_opf & REQ_OP_MASK)
+static inline enum req_op bio_op(const struct bio *bio)
+{
+	return bio->bi_opf & REQ_OP_MASK;
+}
 
 /* obsolete, don't use in new code */
 static inline void bio_set_op_attrs(struct bio *bio, unsigned op,