UML mount failure with Linux 6.11

[Hongbo Li]

On 2024/11/27 20:02, Karel Zak wrote:
> On Wed, Nov 27, 2024 at 09:26:46AM GMT, Hongbo Li wrote:
>>
>>
>> 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?
> 
> Yes (see reply to Johannes ).
> 
>> Such as treat the whole option as one
>> key(also may be with comma, even with equal)
> 
> There could be userspace specific options, VFS flags, etc.
> 
>    -o /home/hostfs,ro,noexec
> 
> Is it one path or path and two options?
> 
Interesting!
Perhaps more documentation is needed. VFS flags is filtered, but for 
hostfs, it is a valid path. The semantics seems not very complete. :)

Thanks,
Hongbo

>> 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.
> 
> We can automatically add a key (e.g. hostfs=) and use FSCONFIG_SET_FLAG.
> The goal should be to get the path as a value, because key is limited to
> 256 bytes.
> 
>      Karel
>