linux-kernel - Re: [PATCH] erofs: add error log in erofs_fc_parse

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Message-ID: <58cadb57-22ce-4818-af2b-9ae452c38f27@linux.alibaba.com>
Date: Fri, 17 Jan 2025 17:54:59 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Chen Linxuan <chenlinxuan@...ontech.com>, Gao Xiang <xiang@...nel.org>,
 Chao Yu <chao@...nel.org>, Yue Hu <zbestahu@...il.com>,
 Jeffle Xu <jefflexu@...ux.alibaba.com>, Sandeep Dhavale <dhavale@...gle.com>
Cc: linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] erofs: add error log in erofs_fc_parse_param



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@...ontech.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