润和Neptune(W800)文件不能写入

参照鸿蒙官方指引，在润和Neptune(W800)开发板上测试，写入字节数总是0，不知道是什么原因，特来请教大神！

相关代码如下：

		else if (strcmp((char *)p_uart_opr->rx_buffer, "test-fs") == 0)
		{
			// open && write
			char fileName[] = "testfile";
			static const char def[] = "utils_file_operation implement.";
			int fd = UtilsFileOpen(fileName, O_RDWR_FS | O_CREAT_FS | O_TRUNC_FS, 0);
			printf("file handle = %d\n", fd);
			int ret = UtilsFileWrite(fd, def, strlen(def));
			printf("write ret = %d\n", ret);

			// seek
			ret = UtilsFileSeek(fd, 5, SEEK_SET_FS);
			printf("lseek ret = %d\n", ret);

			// read && close
			char buf[64] = {0};
			int readLen = UtilsFileRead(fd, buf, 64);
			ret = UtilsFileClose(fd);
			printf("read len = %d : buf = %s\n", readLen, buf);

			// stat
			int fileLen = 0;
			ret = UtilsFileStat(fileName, &fileLen);
			printf("file size = %d\n", fileLen);

			// delete
			ret = UtilsFileDelete(fileName);
			printf("delete ret = %d\n", ret);
		}

在终端打印如下：

Received 7 byte(s) new data from UART1:
test-fs
file handle = 0
write ret = 0
lseek ret = 0
read len = 0 : buf = 
file size = 0
delete ret = 0