Re: [PATCH 0/7] btrfs-progs: cmds/tune: add set/clear features

[Qu Wenruo <wqu@suse.com>]

On 2023/9/22 08:03, waxhead wrote:
> Qu Wenruo wrote:
>> This is the first step to convert btrfstune functionality to "btrfs
>> tune" subcommand group.
>>
>> For now only binary features, aka set and clear, is supported,
>> thus uuid and csum change is not yet implemented.
>> (Both need their own subcommand groups other than set/clear groups)
>>
>> And even for set/clear, there is some changes to btrfstune:
>>
>> - Merge seed feature into set/clear
>>    To enable seeding, just go "btrfs tune set seed <device>".
>>
>> - All supported features can be checked by "list-all" feature
>>    Please note that, "btrfs tune set list-all" and
>>    "btrfs tune clear list-all" will have different output.
>>
> As just a regular BTRFS user I would like to please ask you to consider 
> having functions that may have consequences e.g. "dangerous" functions 
> disabled until enabled.
> 
> In other words much like you need to arm a missile or flip a safety 
> cover on a toggle switch
> 
> So if btrfs on every mount set a bit that disabled access to dangerous 
> functions (such as the tune functionality you would have to explicitly 
> enable it to be able to do scary stuff).
> 
> btrfs tune enable
> btrfs tune whatever_needs_tuning=123
> btrfs tune disable (manually disable scary functions)

We hide unsafe features behind the experimental flag of btrfs-progs, 
which is determined at compiling time.

Furthermore, all those features can be set/clear in "btrfs tune" must be 
done offline (unmounted).

Thus I think there is not much I can do to further improve the situation.

Thanks,
Qu

> 
> And yes, I am aware that root users have powers to do scary stuff, but 
> sometimes even root users need to be protected against free will.
> 
> Please consider something like the above...