Re: Upgraded from Buster to Bullseye, unmountable Btrfs filesystem

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2021/11/11 21:55, S. wrote:
> On 11/11/21 02:11, Qu Wenruo wrote:
>
>>> root@OpenMediaVault:~# dd if=/dev/sda3 of=/tmp/mirror1 bs=1 count=16k
>>> skip=149487616
>>> 16384+0 records in
>>> 16384+0 records out
>>> 16384 bytes (16 kB, 16 KiB) copied, 0.305711 s, 53.6 kB/s
>>
>> My bad, this copy should be from /dev/sdb2, not /dev/sda3.
>>
>> No wonder both copy doesn't match.
>
> Hi, I really appreciate your help to fix this. I am attaching the new
> `mirror1` image, generated like this:
>
> ------------------------
> root@OpenMediaVault:~# dd if=/dev/sdb2 of=/tmp/mirror1 bs=1 count=16k

You missed the "skip=" parameter.

> 16384+0 records in
> 16384+0 records out
> 16384 bytes (16 kB, 16 KiB) copied, 0.274943 s, 59.6 kB/s
> root@OpenMediaVault:~# rsync -avh /tmp/mirror1
> sully@192.168.1.14:/home/sully/Desktop/
> Password:
> sending incremental file list
> mirror1
>
> sent 16.49K bytes  received 35 bytes  3.67K bytes/sec
> total size is 16.38K  speedup is 0.99
> ------------------------
>
>
>> # dd if=mirror2 of=/dev/sdb2 bs=1 count=16k skip=149487616
>> # dd if=mirror2 of=/dev/sda3 bs=1 count=16k skip=170459136

All my bad.

The correct command line should be:

# dd if=mirror2 of=/dev/sdb2 bs=1 count=16k seek=149487616
# dd if=mirror2 of=/dev/sda3 bs=1 count=16k seek=170459136

Thankfully, even with the wrong command, btrfs has enough space reserved
at its beginning, so your fs is still untouched and very safe.

Thanks,
Qu
>
> After writing out your fixed `mirror2` image with the above commands I
> get these dmesg errors when attempting to mount it:
>
> -------------------------
> [   28.859193] BTRFS info (device sda3): flagging fs with big metadata
> feature
> [   28.866209] BTRFS info (device sda3): disk space caching is enabled
> [   28.872507] BTRFS info (device sda3): has skinny extents
> [   29.053000] BTRFS critical (device sda3): corrupt leaf: root=9
> block=170459136 slot=0, invalid key objectid, have 1101835439474057344
> expect to be aligned to 4096
> [   29.067527] BTRFS error (device sda3): block=170459136 read time tree
> block corruption detected
> [   29.120141] BTRFS critical (device sda3): corrupt leaf: root=9
> block=170459136 slot=0, invalid key objectid, have 1101835439474057344
> expect to be aligned to 4096
> [   29.134781] BTRFS error (device sda3): block=170459136 read time tree
> block corruption detected
> [   29.143568] BTRFS warning (device sda3): failed to read root
> (objectid=9): -5
> [   29.239873] BTRFS error (device sda3): open_ctree failed
> -------------------------
>
> Please let me know if you need anything else. Thanks a lot!