Re: trouble mounting btrfs filesystem....

[Hans van Kranenburg <hans.van.kranenburg@mendix.com>]

On 08/14/2018 03:00 PM, Dmitrii Tcvetkov wrote:
>> Scott E. Blomquist writes:
>>  > Hi All,
>>  > 
>>  > [...]
> 
> I'm not a dev, just user.
> btrfs-zero-log is for very specific case[1], not for transid errors.
> Transid errors mean that some metadata writes are missing, if
> they prevent you from mounting filesystem it's pretty much fatal. If
> btrfs could recover metadata from good copy it'd have done that.
> 
> "wanted 2159304 found 2159295" means that some metadata is stale by 
> 9 commits. You could try to mount it with "ro,usebackuproot" mount
> options as readonly mount is less strict. If that works you can try
> "usebackuproot" without ro option. But 9 commits is probably too much
> and there isn't enough data to rollback so far.

Keep in mind that a successful mount with usebackuproot does not mean
you're looking at a consistent filesystem. After each transaction
commit, disk space that is no longer referenced is immediately freed for
reuse.

So, even if you can mount with usebackuproot, you have to hope that none
of the metadata blocks that were used back then have been overwritten
already, even the ones in distant corners of trees. A full check / scrub
/ etc would be needed to find out.

-- 
Hans van Kranenburg