Re: Feature request, "create on mount" to create mount point directory on mount, implied remove on unmount

[Al Viro <viro@ZenIV.linux.org.uk>]

On Sat, Jul 04, 2015 at 11:48:28PM +0100, jon wrote:

> Yes, but like I say automount is normally based on an event. I am simply
> talking about a flag/switch that can be used for optional implied
> mkdir,rmdir around calls to mount() unount() - nothing more, nothing
> less !

umount(2) is not the only way for mount to detached from a mountpoint.
There's exit(2) as well - when the last process in a namespace exits, it
gets dissolved.  What should happen upon those?  Even more interesting question
is what should happen if you do such mount, then clone a process into a new
namespace and have it exit.  Should _that_ rmdir the hell out of that
mountpoint (presumably detaching everything mounted on it in all namespaces)?

What should happen when a process in new namespace decides to unmount that
thing, because they don't what it visible.  Should that take out the instance
in parent namespace? `