df and multiple-mounted mountpoints (redux)

[Christian Jones]

This issue is somewhat similar to that reported in
http://mail.gnu.org/archive/html/bug-coreutils/2003-07-msg00027.html

After mounting different devices at the same mount point, df reports the
wrong one:

-bash-2.05b# df
Filesystem           1K-blocks      Used Available Use% Mounted on
rootfs                 3874756    847804   2986952  23% /
/dev/root              3874756    847804   2986952  23% /
var                      32768       964     31804   3% /var

-bash-2.05b# mkdir -p /mnt

-bash-2.05b# mount /dev/discs/disc0/part3 /mnt

-bash-2.05b# ls /mnt
bin  boot  dev  etc  lib  lost+found  mnt  proc  root  sbin  usr  var

-bash-2.05b# mount /dev/discs/disc0/part4 /mnt

-bash-2.05b# ls /mnt
infinit  infinit-0.3  lost+found

-bash-2.05b# df -P
Filesystem         1024-blocks      Used Available Capacity Mounted on
rootfs                 3874756    847804   2986952      23% /
/dev/root              3874756    847804   2986952      23% /
var                      32768       964     31804       3% /var
/dev/discs/disc0/part3  68555700    272936  68282764       1% /mnt
/dev/discs/disc0/part4  68555700    272936  68282764       1% /mnt

-bash-2.05b# df -P /mnt/infinit
Filesystem         1024-blocks      Used Available Capacity Mounted on
/dev/discs/disc0/part3  68555700    272936  68282764       1% /mnt

As the manual (in concordance with posix) states:
With no arguments, `df' reports the space used and available on all
currently mounted filesystems (of all types).  Otherwise, `df' reports
on the filesystem containing each argument FILE.

Whereas clearly (in the above case), it doesn't.  The aforementioned 
thread also notes (in fact, stresses) the fact that the capacity is 
incorrect for /dev/discs/disc0/part3 after something has been mounted 
"over" it.  Unfortunately, the consensus on that report seemed to be 
that there wasn't an obvious way to fix it.  Is there an obvious 
solution to this one, such as reporting the filesystem mounted *last* 
instead of the one mounted first?

CDJ
--
Christian Jones
address@hidden
http://www.aleph0.com/~chjones