Filesystem space accounting bug

[Walter Hofmann <walter.hofmann@mi.uni-erlangen.de>]

Hi,

I have a backup script which creates a filesystem image which is later 
written to DVD. It is created & loop-mounted with

 dd if=/dev/zero of=${DARIMAGE} bs=1024k count=4460 || exit 1
 mke2fs -F -b 4096 -m 0 -N 32 -O sparse_super -L BACKUP ${DARIMAGE} || exit 1
 sync
 mount /mnt/dar
 touch /mnt/dar/backup-stamp

Then I use the "dar" utility to create a single large file on this. I
believe, but have not checked, that dar writes the file linearly. dar is
instructed to stop writing to the filesystem before it reaches 4GB. 

However, recently, dar failed after approx. 3GB with ENOSPC. The 
filesystem was still mounted, so I could check that there really were 
only 3GB written to it. Still, I could not even create a 1 byte file on 
it, although there should be around 1GB free space left.

There were no error messages logged. I unmounted the image and ran 
e2fsck on it and it reported that the free block count in a number of 
groups on the filesystem was wrong. 

I'm using Linux 2.6.6. I tried to reproduce this, but now it works
again.

Walter