Re: Help with unmountable btrfs fs - device tree issues suspected

[Kareem Straker <kareem.straker@gmail.com>]

Hi, I'm still trying to restore data from the drive that I have.

I'm hoping that someone might be able to help, or provide some advice
how I can proceed.

It's starting to seem hopeless for this.

Thanks for any help you can provide.

kareem.

On Wed, 29 Jan 2020 at 21:55, Kareem Straker <kareem.straker@gmail.com> wrote:
>
> Hi,
>
> My first mail to the list, so I hope I'm getting this right.
>
> I'm getting a little despirate trying to recover my Unraid system
> btrfs 2-disk cache pool, that seems to be corrupted. The 1st disk
> seems to have lost the partition information completely, the 2nd seems
> to be present but is not able to mount. Neither disk has been
> overwritten as far as I'm aware. Both disks are nvme model Samsung 970
> Evo Plus 250GB.
>
> Trying to cram info into this mail.
>
> Can anyone help? Advice?
>
> When I use any fsck or btrfs tool, I get an error: bad tree block
> 479137857536, bytenr mismatch, want=479137857536, have=0
>
> I believe the filesystem is there, but seems I need to rebuild the
> superblock or tree.
>
> Any suggestions would be appreciated.
>
> disk paths:
> /dev/nvme0n1p1
> /dev/nvme1n1p1
>
> First info + dmesg.log (attached):
> ```
> root@blaster:~# uname -a
> Linux blaster 4.19.94-Unraid #1 SMP Thu Jan 9 08:20:36 PST 2020 x86_64
> AMD Ryzen 5 3600 6-Core Processor AuthenticAMD GNU/Linux
> root@blaster:~# btrfs --version
> btrfs-progs v5.4
> root@blaster:~# btrfs fi show
> bad tree block 479137857536, bytenr mismatch, want=479137857536, have=0
> Couldn't setup device tree
> Label: none  uuid: 3d4bca36-f541-4b63-bb84-1745a9a384eb
>         Total devices 2 FS bytes used 179.16GiB
>         devid    1 size 232.89GiB used 232.01GiB path /dev/nvme1n1p1
>         *** Some devices missing
>
> root@blaster:~# btrfs fi df /mnt/cache
> ERROR: cannot access '/mnt/cache': No such file or directory
> ```
>
> Extra info:
> ```
> root@blaster:~# btrfs check --repair /dev/nvme1n1p1
> enabling repair mode
> WARNING:
>
>         Do not use --repair unless you are advised to do so by a developer
>         or an experienced user, and then only after having accepted that no
>         fsck can successfully repair all types of filesystem corruption. Eg.
>         some software or hardware bugs can fatally damage a volume.
>         The operation will start in 10 seconds.
>         Use Ctrl-C to stop it.
> 10 9 8 7 6 5 4 3 2 1
> Starting repair.
> Opening filesystem to check...
> bad tree block 479137857536, bytenr mismatch, want=479137857536, have=0
> Couldn't setup device tree
> ERROR: cannot open file system
> root@blaster:~#
> root@blaster:~#
> root@blaster:~# btrfs rescue fix-device-size /dev/nvme1n1p1
> bad tree block 479137857536, bytenr mismatch, want=479137857536, have=0
> Couldn't setup device tree
> ERROR: could not open btrfs
>
> ```
>
> ```
> root@blaster:~# btrfs rescue super-recover -v /dev/nvme1n1p1
> All Devices:
>         Device: id = 1, name = /dev/nvme1n1p1
>
> Before Recovering:
>         [All good supers]:
>                 device name = /dev/nvme1n1p1
>                 superblock bytenr = 65536
>
>                 device name = /dev/nvme1n1p1
>                 superblock bytenr = 67108864
>
>         [All bad supers]:
>
> All supers are valid, no need to recover
> ```