diff --git a/drivers/block/null_blk/zoned.c b/drivers/block/null_blk/zoned.c
index 148b871f263ba91629b52001786074a96fe13a55..fce0a54df0e5ff4a204e98106451c5b9bc6cfb29 100644
--- a/drivers/block/null_blk/zoned.c
+++ b/drivers/block/null_blk/zoned.c
@@ -6,7 +6,10 @@
 #define CREATE_TRACE_POINTS
 #include "trace.h"
 
-#define MB_TO_SECTS(mb) (((sector_t)mb * SZ_1M) >> SECTOR_SHIFT)
+static inline sector_t mb_to_sects(unsigned long mb)
+{
+	return ((sector_t)mb * SZ_1M) >> SECTOR_SHIFT;
+}
 
 static inline unsigned int null_zone_no(struct nullb_device *dev, sector_t sect)
 {
@@ -77,12 +80,11 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
 		return -EINVAL;
 	}
 
-	zone_capacity_sects = MB_TO_SECTS(dev->zone_capacity);
-	dev_capacity_sects = MB_TO_SECTS(dev->size);
-	dev->zone_size_sects = MB_TO_SECTS(dev->zone_size);
-	dev->nr_zones = dev_capacity_sects >> ilog2(dev->zone_size_sects);
-	if (dev_capacity_sects & (dev->zone_size_sects - 1))
-		dev->nr_zones++;
+	zone_capacity_sects = mb_to_sects(dev->zone_capacity);
+	dev_capacity_sects = mb_to_sects(dev->size);
+	dev->zone_size_sects = mb_to_sects(dev->zone_size);
+	dev->nr_zones = round_up(dev_capacity_sects, dev->zone_size_sects)
+		>> ilog2(dev->zone_size_sects);
 
 	dev->zones = kvmalloc_array(dev->nr_zones, sizeof(struct nullb_zone),
 				    GFP_KERNEL | __GFP_ZERO);