Re: [PATCH 12/18] shared mount handling: bind and rbind

[Linus Torvalds <torvalds@osdl.org>]

On Wed, 9 Nov 2005, Ram Pai wrote:
>
> And 'umount .' really doen't make sense. What does it mean? umount the 
> current mount? or umount of the mount that is mounted on this dentry?

"umount <directory>" _absolutely_ makes sense, whether "directory" is "." 
or something else. People do it all the time.

Now, if it doesn't unmount the last thing mounted on top of ".", then 
that's a misfeature. It might be a misfeature in the mount program (it 
might scan /etc/mounts top-to-bottom rather than the other way), but the 
kernel should also support it.

> no. I said application _should_not_ depend on it, because it is a
> undefined semantics.

It's definitely neither unusual nor undefined. I do all my umounts by 
directory (in fact, doing it by anything else really _is_ badly defined, 
since a block device can be mounted in many places), and the only sane 
semantics would be to peel off the last mount on that directory.

Now, that doesn't necessarily mean that "list_add_tail()" is wrong. But 
if we add new mounts to the end, then umount remove them from the end too, 
no?

		Linus