Upgraded from Buster to Bullseye, unmountable Btrfs filesystem

["S." <sb56637@gmail.com>]

Hi there, I run OpenMediaVault on an old LaCiE NAS with an armel processor. It has two HDDs, with the Debian root on an EXT4 partition and a simple BtrFS RAID-1 using `/dev/sda3` + `/dev/sdb2` for the OpenMediaVault data. Both drives have a few bad blocks, but I assumed that the filesystem was working around them, because it was running fine for almost 2 years on Buster. The SMART report for both drives says `SMART overall-health self-assessment test result: PASSED`. Today I upgraded to OpenMediaVault 6 and Debian Bullseye, and the BtrFS volume is no longer mountable. Here are my attempts thus far:

https://paste.debian.net/1218866/

For the search engines, these are the key errors:

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     [   86.110770] BTRFS critical (device sda3): corrupt leaf: root=9 block=170459136 slot=0, invalid key objectid, have 1101835439474057344 expect to be aligned to 4096
     [   86.125317] BTRFS error (device sda3): block=170459136 read time tree block corruption detected
     [   86.149595] BTRFS critical (device sda3): corrupt leaf: root=9 block=170459136 slot=0, invalid key objectid, have 1101835439474057344 expect to be aligned to 4096
     [   86.164280] BTRFS error (device sda3): block=170459136 read time tree block corruption detected
     [   86.173099] BTRFS warning (device sda3): failed to read root (objectid=9): -5
     [   86.268589] BTRFS critical (device sda3): corrupt leaf: root=9 block=170459136 slot=0, invalid key objectid, have 1101835439474057344 expect to be aligned to 4096
     [   86.283207] BTRFS error (device sda3): block=170459136 read time tree block corruption detected
     [   86.298934] BTRFS critical (device sda3): corrupt leaf: root=9 block=170459136 slot=0, invalid key objectid, have 1101835439474057344 expect to be aligned to 4096
     [   86.313575] BTRFS error (device sda3): block=170459136 read time tree block corruption detected
     [   86.322394] BTRFS warning (device sda3): failed to read root (objectid=9): -5
     [   86.363745] BTRFS error (device sda3): parent transid verify failed on 78086144 wanted 8060 found 8063
     [   86.390901] BTRFS error (device sda3): parent transid verify failed on 78086144 wanted 8060 found 8063
     [   86.414379] BTRFS error (device sda3): parent transid verify failed on 79216640 wanted 8061 found 8063
     [   86.434284] BTRFS error (device sda3): parent transid verify failed on 79216640 wanted 8061 found 8063
     [   86.465467] BTRFS warning (device sda3): couldn't read tree root
     [   86.500332] BTRFS error (device sda3): open_ctree failed

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     root@OpenMediaVault:~# btrfs check /dev/sda3
     Opening filesystem to check...
     Checking filesystem on /dev/sda3
     UUID: 4a057760-998c-4c66-aa6a-2a08c51d5299
     [1/7] checking root items
     [2/7] checking extents
     Invalid key type(EXTENT_ITEM) found in root(UUID_TREE)
     ignoring invalid key
     [3/7] checking free space cache
     [4/7] checking fs roots
     [5/7] checking only csums items (without verifying data)
     [6/7] checking root refs
     [7/7] checking quota groups skipped (not enabled on this FS)
     found 704343715840 bytes used, no error found
     total csum bytes: 686922316
     total tree bytes: 757006336
     total fs tree bytes: 14794752
     total extent tree bytes: 13795328
     btree space waste bytes: 32551835
     file data blocks allocated: 707684626432
      referenced 707430318080

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Any suggestions? Thanks a lot.