dm: use bio op accessors

Separate the op from the rq_flag_bits and have dm
set/get the bio using bio_set_op_attrs/bio_op.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/md/dm-region-hash.c b/drivers/md/dm-region-hash.c
index 74cb7b99..3550ca7 100644
--- a/drivers/md/dm-region-hash.c
+++ b/drivers/md/dm-region-hash.c
@@ -403,7 +403,7 @@
 		return;
 	}
 
-	if (bio->bi_rw & REQ_DISCARD)
+	if (bio_op(bio) == REQ_OP_DISCARD)
 		return;
 
 	/* We must inform the log that the sync count has changed. */
@@ -526,7 +526,7 @@
 	struct bio *bio;
 
 	for (bio = bios->head; bio; bio = bio->bi_next) {
-		if (bio->bi_rw & (REQ_FLUSH | REQ_DISCARD))
+		if (bio->bi_rw & REQ_FLUSH || bio_op(bio) == REQ_OP_DISCARD)
 			continue;
 		rh_inc(rh, dm_rh_bio_to_region(rh, bio));
 	}