Lost storage data on esp8266

To reproduce it, you need to:
(1).Get a string, length about 1000(I download string from WebSocket).
(2).

fs = require("Storage");
fs.erase("aName");
fs.write("aName", thatString);

(3). Code in .boot0:

if(fs.getFree()<4096) fs.compact();

if the free space did less than 4096 and compact() has run and reboot itself after compact, then run fs.compact(); again, if those actions right, you will lost all data in flash.

So according to this issue, I guess flash must have an amount of the abandoned data before running compact, if not, the compact function will cause data loss.