'btrfs rescue' command (recommended by btrfs check) fails on old BTRFS RAID1 on (currently) openSUSE Leap 15.3

[Johannes Kastl <kastl@b1-systems.de>]

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Good evening,

I need your advice on how to continue with one of my BTRFS RAID1 setups.

The machine and the BTRFS RAID1 were built/created in 2014, as far as I can say. 
It was built using openSUSE Leap, I think 13.X or similar. The machine was then 
constantly upgraded and is now running openSUSE Leap 15.3 with a 5.3.18 kernel 
(detailed infos below).

As one of the HDDs started reporting SMART errors, I just dd'ed each of the 4TB 
disks onto new 8TB disks (and fixed the GPT backup). I did not resize the 
filesystem, so it is still 3.6 TiB like on the old HDDs.
To make sure that the filesystem was working, I issued a btrfsck against each of 
the devices.

The output of the check is below. The TL;DR was that I should run 'btrfs rescue 
fix-device-size' to fix a "minor" issue.

Unfortunately, running this command fails:

> root dumbo:/root # btrfs rescue fix-device-size /dev/sdc1
> Unable to find block group for 0
> Unable to find block group for 0
> Unable to find block group for 0
> btrfs unable to find ref byte nr 2959295381504 parent 0 root 3  owner 1 offset 0
> transaction.c:168: btrfs_commit_transaction: BUG_ON `ret` triggered, value -5
> btrfs(+0x51f99)[0x55aeeae12f99]
> btrfs(btrfs_commit_transaction+0x193)[0x55aeeae13573]
> btrfs(btrfs_fix_device_size+0x123)[0x55aeeadfe2a3]
> btrfs(btrfs_fix_device_and_super_size+0x6b)[0x55aeeadfe56b]
> btrfs(+0x6ceee)[0x55aeeae2deee]
> btrfs(main+0x8e)[0x55aeeade008e]
> /lib64/libc.so.6(__libc_start_main+0xef)[0x7f907fc0d2bd]
> btrfs(_start+0x2a)[0x55aeeade028a]
> Aborted (core dumped)
> root dumbo:/root #

So, my question is what I should do:

Do I need to run another command to fix this issue?
Can I safely ignore the issue?
Should I copy all of the data to another disk, and create a new BTRFS RAID1 from 
scratch? (Which of course I would like to avoid, if possible...)

Maybe someone can advise me on how to proceed. I am grateful for all of the 
input I get.

If there is other information I should give, please feel free to reach out to me.

Kind Regards
Johannes

#######################################################################
btrfs check output:

> root dumbo:/root # btrfs check -p /dev/sdc1 ;btrfs check -p /dev/sdd1
> Opening filesystem to check...
> Checking filesystem on /dev/sdc1
> UUID: 50651b41-bf33-47e7-8a08-afbc71ba0bf8
> [1/7] checking root items                      (0:03:09 elapsed, 9467877 items checked)
> WARNING: unaligned total_bytes detected for devid 2, have 4000785964544 should be aligned to 4096
> WARNING: this is OK for older kernel, but may cause kernel warning for newer kernels
> WARNING: this can be fixed by 'btrfs rescue fix-device-size'
> [2/7] checking extents                         (0:38:38 elapsed, 6910485 items checked)
> WARNING: minor unaligned/mismatch device size detected
> WARNING: recommended to use 'btrfs rescue fix-device-size' to fix it
> [3/7] checking free space cache                (0:02:26 elapsed, 3730 items checked)
> [4/7] checking fs roots                        (6:43:40 elapsed, 6614818 items checked)
> [5/7] checking csums (without verifying data)  (0:10:36 elapsed, 1419101 items checked)
> [6/7] checking root refs                       (0:00:00 elapsed, 4 items checked)
> [7/7] checking quota groups skipped (not enabled on this FS)
> found 3308275023872 bytes used, no error found
> total csum bytes: 3119386928
> total tree bytes: 113221238784
> total fs tree bytes: 108770082816
> total extent tree bytes: 971456512
> btree space waste bytes: 15308811797
> file data blocks allocated: 3195053785088
>  referenced 3195047018496

#######################################################################

Machine and filesystem details

> $ uname -a
> Linux dumbo 5.3.18-150300.59.60-default #1 SMP Fri Mar 18 18:37:08 UTC 2022 (79e1683) x86_64 x86_64 x86_64 GNU/Linux
> 
> # btrfs --version
> btrfs-progs v4.19.1
> 
> # btrfs fi show
> Label: 'DUMBO_BACKUP_4TB'  uuid: 50651b41-bf33-47e7-8a08-afbc71ba0bf8
>         Total devices 2 FS bytes used 3.08TiB
>         devid    1 size 3.64TiB used 3.64TiB path /dev/sdd1
>         devid    2 size 3.64TiB used 3.63TiB path /dev/sdc1
> 
> # btrfs fi df /mnt/DUMBO_BACKUP_4TB/
> Data, RAID1: total=3.36TiB, used=2.97TiB
> Data, DUP: total=13.50MiB, used=2.81MiB
> Data, single: total=1.00GiB, used=0.00B
> System, RAID1: total=32.00MiB, used=560.00KiB
> System, single: total=32.00MiB, used=0.00B
> Metadata, RAID1: total=284.94GiB, used=108.05GiB
> Metadata, DUP: total=512.00MiB, used=64.00KiB
> Metadata, single: total=1.00GiB, used=0.00B
> GlobalReserve, single: total=512.00MiB, used=0.00B

-- 
Johannes Kastl
Linux Consultant & Trainer
Tel.: +49 (0) 151 2372 5802
Mail: kastl@b1-systems.de

B1 Systems GmbH
Osterfeldstraße 7 / 85088 Vohburg
http://www.b1-systems.de
GF: Ralph Dehner
Unternehmenssitz: Vohburg / AG: Ingolstadt,HRB 3537

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