[BusyBox] Endless "umount" corner cases: judgement call time...

[Rob Landley]

Okay, with 2.6 you can now happily mount the same block device in several 
places and it acts a bit like multiple --bind mounts (they'll all share the 
same superblock so nothing gets corrupted).

So, if you mount /dev/hda4 in three places and then umount /dev/hda4... Does 
this mean all three places should be unmounted?  Or just the most recent one?  
(Note you can specify a directory you want unmounted, and this is now a 
different thing than specifying the block devices.  Unmounts now always try 
to work on directories because the current internal logic that tries to deal 
with a --bind mount and convert that to a block device is going to get really 
confused.  Not that I'm ever quite sure what it expected to do umounting an 
NFS mount or ramfs anyway...)

Anyway, I'm leaning towards "umount /dev/hda4" umounts all instances of hda4, 
because if you wanted to specify umounting a specific directory you've have 
indicated the directory.  But I'd like a show of hands about this.  (It 
wasn't an issue back before bind mounts existed because you couldn't mount a 
block device in two places and expect it to work back then.)

Rob