linux-kernel - Re: [PATCH RFC 0/4] erofs-utils: Add --meta_fix and --meta

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Message-ID: <2408568f-a9e6-4e32-83b2-e79aee83a55a@linux.alibaba.com>
Date: Tue, 22 Apr 2025 21:50:20 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Hongbo Li <lihongbo22@...wei.com>, xiang@...nel.org, chao@...nel.org,
 huyue2@...lpad.com, jefflexu@...ux.alibaba.com
Cc: linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 0/4] erofs-utils: Add --meta_fix and --meta_only
 format options

Hi Hongbo,

On 2025/4/22 20:36, Hongbo Li wrote:
> In this patchset, we have added two formatting options --meta_fix and
> --meta_only to extend the ability of EROFS. In the case of using OBS,
> we can convert the directory tree structure from OBS into the erofs
> image and implement on-demand loading logic based on this. Since OBS
> objects are often large, we need to separate the metadata area from
> the data area, which is the reason we introduce the --meta_fix option.
> To accelerate the formatting process, we can skip the formatting of
> the raw data by adding --meta_only option.

Thanks for the patches!

I wonder if it's possible to reuse blobchunk.c codebase for
such usage in the short term.

Also I hope there could be some better option knobs for these
new features.

> 
> A simple usage example is as follows:
>    1. Build one xattr with OBS key in s3fs.
>    2. mkfs.erofs --meta_fix --meta_only data.img /mnt/s3fs to format
>    3. Implement the loading logic in kernel or userspace.
> 
> Based on the above logic, we can easily expose the directory tree
> from OBS to users in the form of the EROFS file system and implement
> on-demand data loading for large OBS objects.

BTW, It's possible to upstream OBS implementation to erofs-utils
if any chance?

Thanks,
Gao Xiang