Re: [PATCH] erofs: add error log in erofs_fc_parse_param

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2025/1/17 17:50, Chen Linxuan wrote:
> On Fri, 2025-01-17 at 17:28 +0800, Gao Xiang wrote:
>> Hi Linxuan,
>>
>> On 2025/1/17 16:52, Chen Linxuan wrote:
>>> While reading erofs code, I notice that `erofs_fc_parse_param` will
>>> return -ENOPARAM, which means that erofs do not support this option,
>>> without report anything when `fs_parse` return an unknown `opt`.
>>>
>>> But if an option is unknown to erofs, I mean that option not in
>>> `erofs_fs_parameters` at all, `fs_parse` will return -ENOPARAM,
>>> which means that `erofs_fs_parameters` should has returned earlier.
>>>
>>> Entering `default` means `fs_parse` return something we unexpected.
>>> I am not sure about it but I think we should return -EINVAL here,
>>> just like `xfs_fs_parse_param`.
>>>
>>> Signed-off-by: Chen Linxuan <chenlinxuan@uniontech.com>
>>
>> I think the default branch is actually deadcode here, see
>> erofs_fc_parse_param() -> fs_parse() -> fs_lookup_key() -> -ENOPARAM
>>
>> then vfs_parse_fs_param() will show "Unknown parameter".
>>
>> Maybe we could just kill `default:` branch...
> 
> ext4 do not have a `default:` branch, but xfs return -EINVAL.
> 
> I think `default:` branch can report error when `fs_parse` or
> `erofs_fs_parameters` goes wrong.

How can it go wrong?

Thanks,
Gao Xiang