Broken BTRFS Partition

Broken BTRFS Partition

[AccSwtch50]

Hi, How do I fix my broken btrfs partition?

This is the dmesg log when I tried to mount it:
[22709.506970] BTRFS info (device sda21): first mount of filesystem
853da0a7-a25b-423a-8b42-4ef0cec712fe
[22709.506989] BTRFS info (device sda21): using crc32c (crc32c-x86)
checksum algorithm
[22709.506997] BTRFS info (device sda21): using free-space-tree
[22709.809320] BTRFS error (device sda21): level verify failed on logical
205872398336 mirror 1 wanted 1 found 0
[22709.809395] BTRFS error (device sda21): failed to load root free space
[22709.810018] BTRFS error (device sda21): open_ctree failed: -5

And here's the output of btrfs check:
Opening filesystem to check...
ERROR: root [10 0] level 0 does not match 1

ERROR: could not setup free space tree
ERROR: cannot open file system

Re: Broken BTRFS Partition

[Qu Wenruo]

在 2025/8/14 12:51, AccSwtch50 写道:
> Hi, How do I fix my broken btrfs partition?

History please.

This is a pretty serious failure of COW.

Unless you were using nobarrier mount option and a sudden power loss 
happened, it may indicate your storage doesn't properly handle FUA/FLUSH 
commands.

> 
> This is the dmesg log when I tried to mount it:
> [22709.506970] BTRFS info (device sda21): first mount of filesystem
> 853da0a7-a25b-423a-8b42-4ef0cec712fe
> [22709.506989] BTRFS info (device sda21): using crc32c (crc32c-x86)
> checksum algorithm
> [22709.506997] BTRFS info (device sda21): using free-space-tree
> [22709.809320] BTRFS error (device sda21): level verify failed on logical
> 205872398336 mirror 1 wanted 1 found 0
> [22709.809395] BTRFS error (device sda21): failed to load root free space
> [22709.810018] BTRFS error (device sda21): open_ctree failed: -5

You can try "ro,rescue=all", which will make btrfs to ignore the 
corrupted free space tree.

If lucky enough, you can still salvage your data.

> 
> And here's the output of btrfs check:
> Opening filesystem to check...
> ERROR: root [10 0] level 0 does not match 1

Repair will not help much in this case.

Thanks,
Qu

> 
> ERROR: could not setup free space tree
> ERROR: cannot open file system
>