Re: Endless mount and backpointer mismatch

[Pepie 34 <pepie34@gmail.com>]

Le 27/01/2020 à 22:48, Chris Murphy a écrit :
> On Mon, Jan 27, 2020 at 2:20 PM Pepie 34 <pepie34@gmail.com> wrote:
>> Dear BTRFS community,
>>
>> I've a raid 1 setup on two luks encrypted drives for 4 years that serves
>> me as btrbk backup target from an other computer.
>> There is a lot of ro snaptshots on it.
>>
>> I've mistakenly launched a balance on it which was extremely slow and
>> tried to cancelled it.
>> After two days of cancelling without results, I decided to power off the
>> computer.
>>
>> After the reboot, even with the skip_balance mount option, the mounting
>> is endless, no error in the kernel message and it never mounts.
>>
>> What I have done so far:
>> - mount the volume with the ro option (fast to mount, data OK).
>> - scrub in ro mode, no error found
>> - btrfs check
>> In the extent check  there is plenty of errors like this :
>> =>
>> ref mismatch on [9404816285696 32768] extent item 6, found 5
>>
>> incorrect local backref count on 9404816285696 parent 5712684302336
>> owner 0 offset 0 found 0 wanted 1 back 0x55f371ee1ad0
>> backref disk bytenr does not match extent record, bytenr=9404816285696,
>> ref bytenr=0
>> backpointer mismatch on [9404816285696 32768]
>> <=
>> No errors in other checks, though checking "quota groups" is very slow.
>>
>> What should I do ? btrfs check --repair ?
>> btrfs check --init-extent-tree ?
>> btrfs --clear-space-cache ?
> None of the above.
>
> What kernel version and btrfs-progs? Newer kernels should have better
> performance with quota enabled and many snapshots, even though I think
> that combination is still not advised for performance reasons. Older
> kernel might have a known bug related to the behavior you're
> experiencing, but we need to know the versions.
>
>
>
Kernel : 4.19.0-6-amd64 #1 SMP Debian 4.19.67-2+deb10u2 (2019-11-11)
x86_64 GNU/Linux
btrfs-progs: 4.20.1-2

I'm on debian buster.

Note that I don't really care about perf now, I mainly want to mount r/w
my volume.
With the same setup raid1 / luks  / quota, it was fast to mount and use
before the failed balancing.
(mount took about 2s... )
Now it is not mounting at all (except with ro)

Best regards,

Pepie 34