UML mount failure with Linux 6.11

[Hongbo Li]

On 2024/11/26 21:50, Johannes Berg wrote:
> On Mon, 2024-11-25 at 18:43 +0100, Karel Zak wrote:
>>
>> The long-term solution would be to clean up hostfs and use named
>> variables, such as "mount -t hostfs none -o 'path="/home/hostfs"'.
> 
> That's what Hongbo's commit *did*, afaict, but it is a regression.
> 
> Now most of the regression is that with fsconfig() call it was no longer
> possible to specify a bare folder, and then we got discussing what
> happens if the folder name actually contains a comma...
> 
> But this is still a regression, so we need to figure out what to do
> short term?
> 
So for short term, even long term, can we consider handling the hostfs 
situation specially within libmount? Such as treat the whole option as 
one key(also may be with comma, even with equal), in this case, libmount 
will use it as FSCONFIG_SET_FLAG. We can do that because for hostfs, it 
only has one mount option, and no need for extension.

Thanks,
Hongbo

> Ignoring the "path with comma" issue, because we can't even fix that in
> the kernel given what you describe changed in userspace, we can probably
> only
> 
>   1) revert the hostfs conversion to the new API, or
>   2) somehow not require the hostfs= key?
> 
> I don't know if either of those are even possible
> 
> 
> Fixing the regression fully (including for paths containing commas)
> probably also requires userspace changes. If you don't want to make
> those we can only point to your workarounds instead, since we can't do
> anything on the kernel side.
> 
> I don't know the fsconfig() API, is it possible to have key-less or
> value-less calls? What does happen
> 
> johannes
>