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Date:   Sun, 30 Jul 2023 15:31:22 +0200
From:   Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <thomas@t-8ch.de>
To:     Jingbo Xu <jefflexu@linux.alibaba.com>
Cc:     hsiangkao@linux.alibaba.com, chao@kernel.org, huyue2@coolpad.com,
        linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        Karel Zak <kzak@redhat.com>
Subject: Re: [PATCH v2] erofs: deprecate superblock checksum feature
Message-ID: <f796b2ed-8564-45c3-bb04-44dfabb575c7@t-8ch.de>
References: <20230717112703.60130-1-jefflexu@linux.alibaba.com>
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On 2023-07-17 19:27:03+0800, Jingbo Xu wrote:
> Later we're going to try the self-contained image verification.
> The current superblock checksum feature has quite limited
> functionality, instead, merkle trees can provide better protection
> for image integrity.

The crc32c checksum is also used by libblkid to gain more confidence
in its filesystem detection.
I guess a merkle tree would be much harder to implement.

This is for example used by the mount(8) cli program to allow mounting
of devices without explicitly needing to specify a filesystem.

Note: libblkid tests for EROFS_FEATURE_SB_CSUM so at least it won't
break when the checksum is removed.

> xxhash is also used in the following xattr name filter feature.  It is
> redundant for one filesystem to rely on two hashing algorithms at the
> same time.
> 
> Since the superblock checksum is a compatible feature, just deprecate
> it now.
> 
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
> changes since v1:
> - improve commit message (Gao Xiang)
> 
> v1: https://lore.kernel.org/all/20230714033832.111740-1-jefflexu@linux.alibaba.com/
> ---
>  fs/erofs/Kconfig |  1 -
>  fs/erofs/super.c | 44 +++++---------------------------------------
>  2 files changed, 5 insertions(+), 40 deletions(-)

> [..]