Re: Endless mount and backpointer mismatch

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

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On 2020/1/28 上午5:20, Pepie 34 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.

Is there anything like "relocating block group XXXX flags XXXX" ?

> 
> 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

So data are all OK.
Just need a way to cancel the balance.

> - 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]
> <=

It could be caused by half-balanced fs.
Need to re-check after we cancel the balance.

> No errors in other checks, though checking "quota groups" is very slow.

That's caused by the nature of qgroup.

> 
> What should I do ? btrfs check --repair ?
> btrfs check --init-extent-tree ?
> btrfs --clear-space-cache ?

None of the options should affect data, but none of them are recommened.

Since the problem is about the balance.

Have you tried to mount the fs with RO,skip_balance, then remount it rw?

Thanks,
Qu

> 
> Will the "init extent tree" option break btrfs receive with old snapshot
> parents ?
> 
> Best regards,
> 
> Pepie34
> 


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