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

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

On Wednesday, 2 April 2025 03:00:33 AEDT Chris Murphy wrote:
> On Tue, Apr 1, 2025, at 1:18 AM, Russell Coker wrote:
> > On Tuesday, 1 April 2025 15:04:20 AEDT Chris Murphy wrote:
> >> These are likely old errors. You'd need to check old logs to see when the
> >> write errors occurred. These statistics are just a counter. You can reset
> >> them with `btrfs dev stats -z` and they'll go back to zero.
> >> 
> >> It's simple counter. It could be 754 errors seen one time. Or it could be
> >> `1 error seen 754 times. Or any combination of multiple errors multiple
> >> times adding up to 754 errors.
> > 
> > Is "btrfs dev stats -z" covered by removing the device from the set and
> > adding it again?  If so I did that but it kept recurring.  The fact that
> > the error count was there in the first place wasn't the unexpected thing,
> > it was the fact that it kept coming back and had no log entries about it.
> 
> Removing it with a `btrfs` command? Or physically disconnecting and
> reconnecting?

btrfs commands.

> The statistics are per device, persistently stored in the device b-tree
> which is metadata block group. So this metadata could be on any device in a
> multiple device Btrfs, not necessarily on the device that produced the
> errors.

It should be on the device itself and once the device is subject to a btrfs 
dev rem command it should be gone for good.

> I'd like to think upon `btrfs device remove` or `btrfs replace` the device's
> stats are also removed from dev tree. But I haven' tested it, and I'm not
> sure what the code says should happen.

After doing the btrfs dev add it reports 0 errors until after reboot.

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