Re: parent transid verify failed

[Chris Murphy <lists@colorremedies.com>]

On Thu, Dec 30, 2021 at 2:10 PM Eric Levy <contact@ericlevy.name> wrote:
>
> Hello.
>
> I had a simple Btrfs partition, with only one subvolume, about 250 Gb
> in size. As it began to fill, I added a second volume, live. By the
> time the size of the file system reached the limit for the first
> volume, the file system reverted to read only.
>
> From journalctl, the following message has recurred, with the same
> numeric values:
>
> BTRFS error (device sdc1): parent transid verify failed on 867434496
> wanted 9212 found 8675
>
> Presently, the file system mounts only as read only. It will not mount
> in read-write, even with the usebackuproot option.
>
> It seems that balance and scrub are not available, either due to read-
> only mode, or some other reason. Both abort as soon as they begin to
> run.

Complete dmesg, at least since adding the 2nd device and subsequent read only.
`btrfs fi us $mountpoint` for the ro mounted file system so we can see
the space available and bg profiles
`btrfs insp dump-s $anydev` for either of the two devices
kernel version
btrfs-progs version
make/model of the two devices being used

>
> What is the best next step for recovery?

For now, take advantage of the fact it mounts read-only, backup
anything important and prepare to restore from backup. Transid errors
are unlikely to be repairable. What's weird in this case is there's no
crash or powerfailure. For transid problems to show up during normal
operation is unusual, as if one of the drives is dropping writes
occasionally without even needing a crash or powerfail to become
confused.


-- 
Chris Murphy