On Wed, Jan 27, 2021 at 12:22 AM Alexey Isaev [off-list ref] wrote:

Hello!

BTRFS volume becomes read-only with this messages in dmesg.
What can i do to repair btrfs partition?

[Jan25 08:18] BTRFS error (device sdg): parent transid verify failed on
52180048330752 wanted 132477 found 132432
[  +0.007587] BTRFS error (device sdg): parent transid verify failed on
52180048330752 wanted 132477 found 132432
[  +0.000132] BTRFS error (device sdg): qgroup scan failed with -5

[Jan25 19:52] BTRFS error (device sdg): parent transid verify failed on
52180048330752 wanted 132477 found 132432
[  +0.009783] BTRFS error (device sdg): parent transid verify failed on
52180048330752 wanted 132477 found 132432
[  +0.000132] BTRFS: error (device sdg) in __btrfs_cow_block:1176:
errno=-5 IO failure
[  +0.000060] BTRFS info (device sdg): forced readonly
[  +0.000004] BTRFS info (device sdg): failed to delete reference to
ftrace.h, inode 2986197 parent 2989315
[  +0.000002] BTRFS: error (device sdg) in __btrfs_unlink_inode:4220:
errno=-5 IO failure
[  +0.006071] BTRFS error (device sdg): pending csums is 430080

What kernel version? What drive make/model?

wanted 132477 found 132432 indicates the drive has lost ~45
transactions, that's not good and also weird. There's no crash or any
other errors? A complete dmesg might be more revealing. And also

smartctl -x /dev/sdg
btrfs check --readonly /dev/sdg

After that I suggest
https://btrfs.wiki.kernel.org/index.php/Restore

And try to get any important data out if it's not backed up. You can
try btrfs-find-root to get a listing of roots, most recent to oldest.
Start at the top, and plug that address in as 'btrfs restore -t' and
see if it'll pull anything out. You likely need -i and -v options as
well.

-- 
Chris Murphy