Re: [RFC PATCH 1/1] ovl: Use fsid as unique identifier for trusted origin

[Christoph Hellwig]

On Wed, Oct 15, 2025 at 07:46:34AM +0800, Anand Jain wrote:
> We needed cloned device mount support for an A/B testing
> use case, but changing the on-disk UUID defeats the purpose.
> 
> Right now, ext4 and Btrfs can mount identical devices,
> but XFS can't. How about extending this to the common
> VFS layer and adding a parameter to tell apart a cloned
> device from the same device accessed through multiple
> paths? I haven't looked into the details yet, but I can
> dig it further.

If you clone a device you need to change the user visible uuid/fsid,
and you need to do that explicitly to a known either saved or user
controlled value.  Assigning a random ID is highly dangerous as seen
here.