Re: corruption after block-group-tree conversion, how to recover? (data is readable)

[Qu Wenruo <wqu@suse.com>]

在 2026/4/27 06:53, Thomas Debesse 写道:
> Hi, I just did a `btrfstune --convert-to-block-group-tree` conversion
> operation on a btrfs filesystem and this corrupted the volume:
> 
> ```
> [  786.278571] BTRFS info (device dm-9): first mount of filesystem <uuid>
> [  786.278595] BTRFS info (device dm-9): using crc32c (crc32c-intel)
> checksum algorithm
> [  786.442781] BTRFS error (device dm-9): parent transid verify failed
> on logical 9820282388480 mirror 2 wanted 5715946 found 5717327
> [  786.448020] BTRFS error (device dm-9): parent transid verify failed
> on logical 9820282388480 mirror 1 wanted 5715946 found 5717327

Unfortunately, transid mismatch is not reliably repairable.

> [  786.449543] BTRFS error (device dm-9): failed to read block groups: -5
> [  786.481199] BTRFS error (device dm-9): open_ctree failed: -5
> ```
> 
> I can mount the btrfs volume with `mount -oro,rescue=all`, I can
> browse the filesystem, and every file data I checked loocked fine.
> 
> Here is the log when mounting with `-oro,rescue=all`:
> 
> ```
> [ 2523.344235] BTRFS info (device dm-9): first mount of filesystem <uuid>
> [ 2523.344260] BTRFS info (device dm-9): using crc32c (crc32c-intel)
> checksum algorithm
> [ 2523.612830] BTRFS error (device dm-9: state C): parent transid
> verify failed on logical 9820282388480 mirror 2 wanted 5715946 found
> 5717327
> [ 2523.613372] BTRFS error (device dm-9: state C): parent transid
> verify failed on logical 9820282388480 mirror 1 wanted 5715946 found
> 5717327
> [ 2523.639263] BTRFS info (device dm-9: state C): enabling ssd optimizations
> [ 2523.639268] BTRFS info (device dm-9: state C): disabling log replay
> at mount time
> [ 2523.639271] BTRFS info (device dm-9: state C): turning on async discard
> [ 2523.639273] BTRFS info (device dm-9: state C): enabling free space tree
> [ 2523.639276] BTRFS info (device dm-9: state C): ignoring bad roots
> [ 2523.639278] BTRFS info (device dm-9: state C): ignoring data csums
> ```
> 
> The log reports SSD optimization to be enabled because those drives
> are bcache backing devices. Bcache was disabled throughout the
> operation.
> 
> I expect that recovering from backup would take 10 days, so I would
> like to avoid that if possible. If there are ways to recompute the
> broken metadata for example or other repair operation, I would prefer
> doing that.

I'm afraid restoring from backup is the only reliable solution.

> 
> The system is running Ubuntu 24.04.4 with Linux 6.8.0-110-generic and
> btrfs-progs 6.6.3-1.1build2.

Unfortunately the btrfs-progs is too old, and possibility the root cause.

There are some fixes in progs v6.15, thus it's strongly recommended to 
use progs newer than v6.15.

Thanks,
Qu

> I can run rescue systems on removable
> drives if newer tools are required to repair.
> 
> Best regards,
>