Date:   Tue, 4 Jan 2022 22:58:53 +0800
From:   Gao Xiang <hsiangkao@linux.alibaba.com>
To:     Jeffle Xu <jefflexu@linux.alibaba.com>
Cc:     dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org,
        chao@kernel.org, linux-erofs@lists.ozlabs.org,
        linux-fsdevel@vger.kernel.org, joseph.qi@linux.alibaba.com,
        bo.liu@linux.alibaba.com, tao.peng@linux.alibaba.com,
        gerry@linux.alibaba.com, eguan@linux.alibaba.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 07/23] erofs: add nodev mode
Message-ID: <YdRgrWEDU8sJVExX@B-P7TQMD6M-0146.local>
Mail-Followup-To: Jeffle Xu <jefflexu@linux.alibaba.com>,
        dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org,
        chao@kernel.org, linux-erofs@lists.ozlabs.org,
        linux-fsdevel@vger.kernel.org, joseph.qi@linux.alibaba.com,
        bo.liu@linux.alibaba.com, tao.peng@linux.alibaba.com,
        gerry@linux.alibaba.com, eguan@linux.alibaba.com,
        linux-kernel@vger.kernel.org
References: <20211227125444.21187-1-jefflexu@linux.alibaba.com>
 <20211227125444.21187-8-jefflexu@linux.alibaba.com>
 <YdRattisu+ITYvvZ@B-P7TQMD6M-0146.local>
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On Tue, Jan 04, 2022 at 10:33:26PM +0800, Gao Xiang wrote:
> On Mon, Dec 27, 2021 at 08:54:28PM +0800, Jeffle Xu wrote:
> > Until then erofs is exactly blockdev based filesystem. In other using
> > scenarios (e.g. container image), erofs needs to run upon files.
> > 
> > This patch introduces a new nodev mode, in which erofs could be mounted
> > from a bootstrap blob file containing the complete erofs image.
> > 
> > The following patch will introduce a new mount option "uuid", by which
> > users could specify the bootstrap blob file.
> > 
> > Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> 
> I think the order of some patches in this patchset can be improved.
> 
> Take this patch as an example. This patch introduces a new mount
> option called "uuid", so the kernel will just accept it (which
> generates a user-visible impact) after this patch but it doesn't
> actually work.
> 
> Therefore, we actually have three different behaviors here:
>  - kernel doesn't support "uuid" mount option completely;
>  - kernel support "uuid" but it doesn't work;
>  - kernel support "uuid" correctly (maybe after some random patch);
> 
> Actually that is bad for bisecting since there are some commits
> having temporary behaviors. And we don't know which commit
> actually fully implements this "uuid" mount option.
> 
> So personally I think the proper order is just like the bottom-up
> approach, and make sure each patch can be tested / bisected
> independently.

Oh, I may misread this patch, but I still think we'd better to
avoid dead paths "TODO" like this as much as possible.

Just do in the bottom-up way.

Thanks,
Gao Xiang