Re: [PATCH AUTOSEL 6.18-6.12] btrfs: derive f_fsid from on-disk fsid and dev_t

[Sasha Levin]

On Fri, Sep 11, 2026 at 06:39:19AM -0700, Dave Hansen wrote:
> On 8/31/26 06:23, Sasha Levin wrote:
> > To prevent f_fsid collisions between original and cloned filesystems,
> > this implementation hashes the dev_t for single-device btrfs filesystems
> > to ensure uniqueness. This is limited to single-device filesystems as
> > cloned mounts are currently only supported for that configuration. Note
> > that f_fsid will change if the device is replaced.
> >
> > Additionally, since the kernel cannot distinguish between the original
> > and the cloned filesystem, this new f_fsid derivation is applied to
> > both.
>
> This commit is causing some real pain to end users that use the FSID to
> encrypt VPN keys. Could we keep it out of the stable kernels for the
> moment, please?

Ack!

--
Thanks,
Sasha