linux-ext4 - Re: ext4 superblock checksum invalid after running resize2fs

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Date:   Tue, 3 Jan 2023 14:17:04 -0700
From:   Andreas Dilger <adilger@...ger.ca>
To:     Zsolt Murzsa <thxer@...er.hu>
Cc:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: ext4 superblock checksum invalid after running resize2fs

On Jan 2, 2023, at 5:35 PM, Zsolt Murzsa <thxer@...er.hu> wrote:
> 
> Hi!
> 
> I've had the same issue with twice in the last couple of days with the resize2fs online expand function.
> I have a md raid 1, with an LVM volume, which is formatted with ext4. I resized the volume (from 4T to 5T), then I ran resize2fs, which ran without error, the file system got bigger.
> 
> After a few hours, I reset the machine (unsafely), due to some zombie processes, but after restarting, the system could not mount the filesystem.
> I checked the disks, and ran some hardware checks, but I didn't find anything wrong. I thought the hard reset caused some problem.
> 
> That was the problem: "Superblock checksum does not match superblock". I tried several superblocks, e2fsck, testdisk, but nothing helped, dumpe2fs showed all the data about the superblock.
> I started to restore from a backup.
> 
> In the meantime, I found the debugfs tool, with which I could skip the checksum check and thus see all the folders and files that I restored to a separate disk.
> I replaced the two drives, recreated md RAID 1, LVM, then reformatted with ext4, started copying the data back.
> 
> I ran out of space so expanded the LV and ran resize2fs again (from 3T to 5T). It ran successfully again, the attached file system is 5T.
> Then I ran an e2fsck.
> 
> "e2fsck -n /dev/vg1/data
> e2fsck 1.46.5 (30-Dec-2021)
> Warning!  /dev/vg1/data is mounted.
> ext2fs_open2: Superblock checksum does not match superblock
> e2fsck: Superblock invalid, trying backup blocks...
> e2fsck: Superblock checksum does not match superblock while trying to open /dev/vg1/data
> 
> The superblock could not be read or does not describe a valid ext2/ext3/ext4
> filesystem.  If the device is valid and it really contains an ext2/ext3/ext4
> filesystem (and not swap or ufs or something else), then the superblock
> is corrupt, and you might try running e2fsck with an alternate superblock:
>    e2fsck -b 8193 <device>
> or
>    e2fsck -b 32768 <device>"

Did you try "e2fsck -fy" to fix the checksum?

> I'm shocked it happened again.
> I can currently write / read the files, but it is suspicious that I will not be able to mount the filesystem again.
> In the first case, I couldn't find a simple solution, but is it possible to fix the checksum somehow?
> It takes a lot of time to use debugfs to copy everything to another drive and back again.
> 
> My current kernel version: 5.19.17-1-pve.
> I can attach all the superblocks (Both the first and second case), or any other information, if needed.


Cheers, Andreas






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