On 2019/1/17 下午9:54, Christian Schneider wrote:
>>>
>>> Do you know, which kernel is needed as base for the patch? Can I apply
>>> it to 4.19 or do I need more recent? If you don't know, I can just try
>>> it out.
>>
>> My base is v5.0-rc1.
>>
>> Although I think there shouldn't be too many conflicts for older kernels.
>>
> I could apply the patch on 4.19, but compilation failed. So I went
> straight to master, where it worked, and I could even mount the fs now.
> 
> Your patch also has a positive impact on free space:
> 
>  df -h /home
> Filesystem      Size  Used Avail Use% Mounted on
> /dev/md42       7.3T  1.9T  1.8P   1% /home
> 
> 1.8PB available space should be enough for the next few years :D
> 
> Thank you very much so far!!!
> 
> So, for further steps: As far as I understood, no possibility to repair
> the fs?

Unfortunately, no possibility.

The corruption of extent tree is pretty nasty.
Your metadata CoW is completely broken.
It really doesn't make much sense to repair, and I don't really believe
the repaired result could be any good.

> I just get the data I can and create it new?

Yep.

And just a general tip, for any unexpected power loss, do a btrfs check
--readonly before doing RW mount.

It would help us to detect and locate possible cause of any corruption
before it cause more damage.

Thanks,
Qu

> 
> BR, CHristian