Re: Virtualbox and btrfs superblock issue

["BARDOT Jérôme" <bardot.jerome@gmail.com>]

Le 29/07/2024 à 16:32, Johannes Thumshirn a écrit :
> On 29.07.24 16:03, Jérôme Bardot wrote:
>> Hi,
>>
>> Sorry if I post at the wrong place but  I didn't find an issue manager
>> (like gitlab).
>> (I also asking myself if a not already post but maybe before i subscribe)
>>
>> So my issue :
>>
>> On a windows host laptop and with a parrot vm with a btrfs and after a
>> power failure the vm looks broken.
>> At start the vm drop down to initramfs.
>> When I try to mount from an iso (of the same os/version) i get following error :
>>
>> mount -t btrfs /dev/sdc1 /media/user/to-rescue
>> mount: /media/user/to-rescue: can't read superblock on /dev/sdc1.
>>          dmesg(1) may have more information after failed mount system call.
>>
>> and dmesg get following :
>> [71283.615636] BTRFS: device fsid 70bf0953-3ee3-481f-8a7d-f7327c6fba67
>> devid 1 transid 182616 /dev/sdc1 (8:33) scanned by mount (24156)
>> [71283.627681] BTRFS info (device sdc1): first mount of filesystem
>> 70bf0953-3ee3-481f-8a7d-f7327c6fba67
>> [71283.627711] BTRFS info (device sdc1): using crc32c (crc32c-intel)
>> checksum algorithm
>> [71283.627725] BTRFS info (device sdc1): using free-space-tree
>> [71283.639345] BTRFS error (device sdc1): parent transid verify failed
>> on logical 26984693760 mirror 1 wanted 182616 found 182618
>> [71283.642087] BTRFS error (device sdc1): parent transid verify failed
>> on logical 26984693760 mirror 2 wanted 182616 found 182618
>> [71283.645163] BTRFS warning (device sdc1): couldn't read tree root
>> [71283.646224] BTRFS error (device sdc1): open_ctree failed
>>
>> How can (if I can) I fix that kind of issue.
>> (i did not create backup/btrfs snapshot)
>> I get that issue on 2 similar setup / power failure and one with a xfs
>> system too.
>>
>> I'm really newbie with btrfs.
>>
>> thx for your feedback.
> This looks like the superblock didn't get written correctly, probably
> because of some kind of cache (volatile write cache in case of a disk,
> or some other cache in case of Virtualbox).
>
> Ypu could try to mount with -o ro,rescue=usebackuproot and see if one of
> the backup roots is still valid.
>
>
I try with the same result, the thing is with a xfs i can came back to 
life a disk with the fsck command.

Maybe virtualbox manage better xfs . If it's not only related to vb, 
btrfs can be a improve based on my feedback.

(ready to redo with some debug option or whatever, just ask)


For my issue i guess one of my only solution is to use photorec or 
similar software.

I will make update here if i achieve my rescue.

thx for your help.

J.