linux-ext4 - [bug report] tune2fs: filesystem inconsistency occurs by concurrent write

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Date:   Mon, 26 Jun 2023 00:00:08 +0800
From:   zhanchengbin <zhanchengbin1@...wei.com>
To:     Theodore Ts'o <tytso@....edu>
CC:     <linux-ext4@...r.kernel.org>, linfeilong <linfeilong@...wei.com>,
        <louhongxiang@...wei.com>, <liuzhiqiang26@...wei.com>
Subject: [bug report] tune2fs: filesystem inconsistency occurs by concurrent
 write

Hi Tytso,
Tune2fs does not recognize writes to the manipulated filesystem in another
namespace, there will be two simultaneous write operations on a
block, resulting in filesystem inconsistencies.

The operation is as follows:
first terminal                                      second terminal
mkfs.ext4 /dev/sdb;
mount /dev/sdb /test-sdb;
dd if=/dev/zero of=/test-sdb/test1 bs=1M count=100;
                                                     unshare -m;
umount;
gdb tune2fs;
b io_channel_write_byte
r -e remount-ro /dev/sdb
c(Write a byte of old data into the cache)
                                                     exit;
(gdb finish)
tune2fs -l /dev/sdb;
tune2fs 1.46.4 (18-Aug-2021)
tune2fs: Superblock checksum does not match superblock while trying to 
open /dev/sdb
Couldn't find valid filesystem superblock.

  - bin.