Re: BTRFS error count 754 after reboot on Debian kernel 6.12.17

[Russell Coker <russell@coker.com.au>]

On Sunday, 23 March 2025 08:36:56 AEDT Qu Wenruo wrote:
> > This is repeatable and it's 754 every time.
> > 
> > After I get the error I remove the device from the array and add it again.
> 
> How did you do the removal and add?

btrfs dev rem ...
btrfs dev add ...

> "btrfs device remove" then "btrfs device add"? Or just power the machine
> down and physically add/remove the device?

I didn't physically remove the devices because working out which device is 
which /dev/sd node is not easy at all.  For unrelated reasons the assignment 
of /dev/sd nodes is apparently random.

> > The system is a Dell PowerEdge T630.
> > 
> > The SSD could have a fault, but if so why does it only show up on reboot
> > and why 754 errors every time?
> 
> The error counters are stored inside the fs, it records all the history
> errors a device hit in the past.
> 
> You need to inform btrfs by either proper btrfs device removal/add, or
> make btrfs to zero the counters.

Yes I had done the proper device removal, but either the counters weren't 
properly reset or some other errors were occuring.  I even tried dding 1G of 
data from /dev/zero over the device after removal and that didn't help.

The problem has gone away now.  I was about to do another run to get dmesg 
output for you but accidentally removed the wrong device.  After I added that 
back then removed and re-added the correct device the problem went away.  I 
can now reboot without seeing an error count of 754.  I presume that forcing a 
bunch of metadata to be moved around changed things somehow.

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