Re: Unmounting lower filesystem while overlayfs uses it

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

On 03/10/2016 01:48 PM, Goldwyn Rodrigues wrote:
> 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.

I found the changes to cloned vfsmount: MS_RDONLY flag.
So, we would have to preserve the stack[].mnt [from ovl_fill_super()] 
variables in ovl_fs and perform the mntput() in ovl_put_super()/ Is that 
okay?


-- 
Goldwyn