Hello,
 
It may not be a bug at all, but I was surprised to find out that 'du -x' is reporting a lower disk usage on /mnt when partitions are mounted.
 
Here is an example with '/mnt' belonging to the same filesystem as '/' :
 
linux$ LANG=EN ls -l /mnt
total 12
drwxr-xr-x 2 root root 4096 Jul  8  2018 VL1800
drwxr-xr-x 2 root root 4096 Jul  8  2018 data
drwxr-xr-x 3 root root 4096 Aug 19 13:24 nfs
 
# I mount two partitions from other disks on /mnt
 
linux$ sudo mount /mnt/VL1800
linux$ sudo mount /mnt/data
 
linux$ du -x /mnt
4    /mnt/nfs/nas
8    /mnt/nfs
12    /mnt
 
# I unmount the two partitions
 
linux$ sudo umount /mnt/VL1800
linux$ sudo umount /mnt/data
 
linux$ du -x /mnt
4    /mnt/data
4    /mnt/VL1800
4    /mnt/nfs/nas
8    /mnt/nfs
20    /mnt
 
/mnt is now bigger.
 
Is this a normal result, because even when mounted, physically, the directories '/mnt/VL1800' and '/mnt/data' still  exist on the '/' filesystem, or not ?
Shouldn't they still occupy 4Kb of disk space each on the '/' filesystem when partitions are mounted ?
 
Best regards,
Joseph Paul