Message-ID: <339d2a18-1c5b-998b-29f5-830d8904bcb3@linux.alibaba.com>
Date:   Tue, 24 Jan 2023 08:08:09 +0800
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Subject: Re: [PATCH v3 0/6] Composefs: an opportunistically sharing verified
 image filesystem
To:     Giuseppe Scrivano <gscrivan@redhat.com>,
        Amir Goldstein <amir73il@gmail.com>
Cc:     Alexander Larsson <alexl@redhat.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        david@fromorbit.com, brauner@kernel.org, viro@zeniv.linux.org.uk,
        Vivek Goyal <vgoyal@redhat.com>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Linus Torvalds <torvalds@linux-foundation.org>
References: <cover.1674227308.git.alexl@redhat.com>
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 <87ilh0g88n.fsf@redhat.com>
 <321dfdb1-3771-b16d-604f-224ce8aa22cf@linux.alibaba.com>
 <878rhvg8ru.fsf@redhat.com>
 <3ae1205a-b666-3211-e649-ad402c69e724@linux.alibaba.com>
 <87sfg3ecv5.fsf@redhat.com>
 <31fc4be5-0e53-b1fb-9a2c-f34d598c0fe7@linux.alibaba.com>
 <87cz77djte.fsf@redhat.com> <878rhuewy0.fsf@redhat.com>
From:   Gao Xiang <hsiangkao@linux.alibaba.com>
In-Reply-To: <878rhuewy0.fsf@redhat.com>
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On 2023/1/22 17:32, Giuseppe Scrivano wrote:
> Giuseppe Scrivano <gscrivan@redhat.com> writes:
> 

...

>>
>> How does validation work in EROFS for files served from fscache and that
>> are on a remote file system?
> 
> nevermind my last question, I guess it would still go through the block
> device in EROFS.
> This is clearly a point in favor of a block device approach that a
> stacking file system like overlay or composefs cannot achieve without
> support from the underlying file system.

nevermind my last answer,

I was thinking with Amir's advice, you could just use FUSE+overlayfs option
for this. I wonder if such option can meet all your requirements (including
unprivileged mounts) without increasing on-disk formats in kernel to do
unprivileged mounts.

If there are still missing features, you could enhance FUSE or overlayfs.

Thanks,
Gao Xiang