ftl: fix is_group_erased() to read the proper offsets

source/ftl/map.c

@@ -14,8 +14,27 @@
  */
 static int is_group_erased(struct ftl_map *map, uint32_t group)
 {
-	return flash_is_erased(map->dev, group << map->log2_pages_per_group,
-		UINT32_C(1) << map->log2_pages_per_group);
+	char data[32];
+	struct flash_dev *dev = map->dev;
+	uint32_t addr = group << (map->log2_pages_per_group + map->log2_page_size);
+	size_t i, nbytes, len = 1 << (map->log2_pages_per_group + map->log2_page_size);
+
+	while (len) {
+		nbytes = min(32, len);
+
+		if (flash_read(dev, addr, data, nbytes) == 0)
+			return 0;
+
+		for (i = 0; i < sizeof(data); ++i) {
+			if (data[i] != 0xff)
+				return 0;
+		}
+
+		addr += nbytes;
+		len -= nbytes;
+	}
+
+	return 1;
 }
 
 /* Given the current user page, this function computes the page number of the