Invisible file(s) fill up the disk

[kalpana]

I've just reinstalled my computer which has multiple HDD. For various reasons, I couldn't check which partition was the original /home, so I chose one (brtfs) and used it without reformating it (I didn't want to risk deleting files that could be important). So far, no particular problem.

Except... Now that I've rebooted, I find myself with a 400G partition that's 100% filled up with nothing : my user partition takes up around 30M, but I can see no file filing up the rest.

df -h tells me the /dev/sdb4 /home is 100% filled
du -h says the files present are that of the brand new account (around 30M)
That stays true even doing it as root.

So I don't know what to do