UML mount failure with Linux 6.11

[Ritesh Raj Sarraf]

Hello Benjamin,

On Thu, 2024-10-31 at 11:07 +0100, Benjamin Berg wrote:
> Hi,
> 
> Newer kernels have become more picky about that with the new mount
> API.
> This is relevant, see the discussion about "Unknown options":
>   https://lwn.net/Articles/979166/
> 
> We only use hostfs for the root file system and in that case it works
> well if you pass the path using "hostfs=/path" on the kernel command
> line. Doing that avoids issues when remounting the file system later
> on.
> 

As upstream developers for UML, what would you conclude it as ?

We've recommended using hostfs for the UML kernel modules as well. What
would be the alternate approach to ensuring a proper boot for a modular
UML kernel ?


> I suppose that currently it does not work to mount hostfs later on.
> No
> idea what the right fix is. Maybe the host directory should be an
> explicit option like "hostpath=..." or so to make it compatible with
> the new mount APIs.

The ability to mount any hostfs mount point was/is a feature provided
by UML. We've used it and integrated with many tools like debos,
fakemachine etc; the Debian bug report has the details.

There'll be more reports following once UML 6.11 hits Debian Testing.

I hadn't expected a working feature to break with a newer Linux
release. :-(

Thanks,
Ritesh

-- 
Ritesh Raj Sarraf | http://people.debian.org/~rrs
Debian - The Universal Operating System
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