Unmounting lower filesystem while overlayfs uses it

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

Hi,

I noticed that you can continue using overlayfs while the underlying 
filesystem is unmounted. While overlayfs continues to use and show the 
entries from the underlying filesystem. Howerver, /proc/mounts is 
missing the lowerdir mount entry. This could be pretty confusing for 
users (say for example for users looking to hot swap devices)

I traced it down to the vfs mount point being copied/cloned as opposed 
to using the original one. Is there a reason why a new vfsmount is used 
as opposed to using the lowerdir's vfsmount? Perhaps I did not look hard 
enough, but I did not find any changes being made to the cloned lowerdir 
vfsmount.

-- 
Goldwyn