Why an empty directory take so much space?

Question

Here is the problem:
[kokoko3k@Gozer ~]$ mkdir /tmp/testdir
[kokoko3k@Gozer ~]$ ls -la /tmp/|grep testdir
drwxr-xr-x 2 kokoko3k users 4096 7 feb 12.01 testdir
We have 4K, ok.
[kokoko3k@Gozer ~]$ cd /tmp/testdir/
[kokoko3k@Gozer testdir]$ while true ; do touch $RANDOM ; ls -1 |wc -l ; done
1
2
600
^C
[kokoko3k@Gozer testdir]$ ls -la /tmp/|grep testdir
drwxr-xr-x 2 kokoko3k users 20480 7 feb 12.02 testdir
20K makes sense, it is full of files, but look here:
[kokoko3k@Gozer testdir]$ rm /tmp/testdir/*
[kokoko3k@Gozer testdir]$ ls -la /tmp/|grep testdir
drwxr-xr-x 2 kokoko3k users 20480 7 feb 12.03 testdir
...now the directory is empty and still take so much space, i dropped caches but nothing changes, the only way to free it is to rmdir and mkdir again.
filesystem is ext4 and mount options are: defaults,barrier=0
Is this... normal?

Answer 1

I can clearly "rmdir /tmp/testdir", that means that the directory is empty, or rmdir reports an error, but here it is the log with du, this is on another box:
koko@slimer ~ ls -la /tmp/testdir
ls: cannot access /tmp/testdir: No such file or directory
koko@slimer ~mkdir /tmp/testdir
koko@slimer /tmp/testdir $ sudo du -sh /tmp/testdir
4,0K /tmp/testdir
koko@slimer ~cd /tmp/testdir
koko@slimer /tmp/testdir $ while true ; do touch $RANDOM ; ls -1 |wc -l ; done
1
2
3
648
649
650
651
^C
koko@slimer /tmp/testdir $ sudo du -sh /tmp/testdir
20K /tmp/testdir
koko@slimer /tmp/testdir $ cd ..
koko@slimer /tmp/testdir $ rm /tmp/testdir/*
koko@slimer /tmp/testdir $ sudo du -sh /tmp/testdir
20K /tmp/testdir
koko@slimer /tmp $ ls /tmp/testdir/ -la
totale 44
drwxr-xr-x 2 koko users 20480 7 feb 17.43 .
drwxrwxrwt 16 root root 20480 7 feb 17.49 ..
koko@slimer /tmp $ rmdir /tmp/testdir
koko@slimer /tmp $ mkdir /tmp/testdir
koko@slimer /tmp/testdir $ sudo du -sh /tmp/testdir
4,0K /tmp/testdir
Still, dir size become bigger when a lot of files are put into it, but never gets smaller, even after deleting all of the files.
Is it a bug?
-EDIT-
Seems to be expected...
http://serverfault.com/questions/294301 … lock-count
Last edited by kokoko3k (2012-02-07 16:58:06)