+static inline unsigned int *blk_alloc_zone_wp_ofst(unsigned int nr_zones)
+{
+	return kvcalloc(nr_zones, sizeof(unsigned int), GFP_NOIO);
+}

This helper seems a bit pointless.

+int blk_get_zone_wp_offset(struct blk_zone *zone, unsigned int *wp_ofst)
+{
+	switch (zone->cond) {
+	case BLK_ZONE_COND_EMPTY:
+		*wp_ofst = 0;
+		return 0;
+	case BLK_ZONE_COND_IMP_OPEN:
+	case BLK_ZONE_COND_EXP_OPEN:
+	case BLK_ZONE_COND_CLOSED:
+		*wp_ofst = zone->wp - zone->start;
+		return 0;
+	case BLK_ZONE_COND_FULL:
+		*wp_ofst = zone->len;
+		return 0;
+	case BLK_ZONE_COND_NOT_WP:
+	case BLK_ZONE_COND_OFFLINE:
+	case BLK_ZONE_COND_READONLY:
+		/*
+		 * Conventional, offline and read-only zones do not have a valid
+		 * write pointer. Use 0 as a dummy value.
+		 */
+		*wp_ofst = 0;
+		return 0;
+	default:
+		return -ENODEV;
+	}

Why not just return the offset?  The error case is impossible anyway.