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

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Message-ID: <F2BFB040EAD9A1F5+3902f0717d54a9990ffe8f042997c8586044d229.camel@uniontech.com>
Date: Fri, 17 Jan 2025 18:00:06 +0800
From: Chen Linxuan <chenlinxuan@...ontech.com>
To: Gao Xiang <hsiangkao@...ux.alibaba.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 Fri, 2025-01-17 at 17:54 +0800, Gao Xiang wrote:
> 
> 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?

What if we forget to update the switch branch for a new option?

> 
> Thanks,
> Gao Xiang
> 
>