Re: Corrupt leaf, trying to recover

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

On 2022/8/13 15:56, Ash Logan wrote:
> Hi, thanks for your email!
>
>> Please post the output of command "btrfs ins dump-tree -b 35291136
>> <device>"
>
> Attached.

It looks correct, all other ROOT_ITEMS has no extra flags, and only that
offending root has the problem.

Thus it looks more like a bitflip.

>
>> It looks like a bitflip so far, and if that's the case, I strongly
>> recommend to do a memtest before continuing.
>
> Will run now, hopefully it comes back clean.
>
>> Unfortunately since you're upgrading to Debian 11, I believe the damage
>> is there for a long time until you have upgraded to a newer kernel with
>> such sanity checks.
> Ouch. At least this suggests that a kernel downgrade could still allow
> mounting and data recovery.

Yes.

As long as that's the only bitflip, everything else should be fine.

If you want, you can remove subvolume 389 (and if that's the only
bitflip) using the older kernel and then mount using much newer kernel.

Personally speaking, it's strongly recommended to use kernel newer than
v5.11, even if a memtest is clean.

That new sanity check introduced in v5.11 should save a lot of hassle
like this.

Thanks,
Qu

>>
>> Thanks,
>> Qu
>>>
>>> Let me know if you have any advice.
>>>
>>> Thanks,
>>> Ash
>>>