Re: [help needed] parent verity error on HDD

["Chris Murphy" <lists@colorremedies.com>]

On Tue, Jul 8, 2025, at 12:05 PM, Pranshu Tanwar wrote:
>> Copy files out with -o ro,rescue=all and reformat. The problem is probably the result of a drive firmware bug. Keep backups!
> It did not mount, I got the files with btrfs restore to work in a 
> snapshot of a shared snapshot to then restore the files. I am now 
> working on rebuilding the drive with safer mount options for both 
> drives.
>
> These are the options I came up with:
>
> /etc/udisks2/mount_options.conf
> ---
> [defaults]
> btrfs_allow=compress,compress-force,datacow,nodatacow,datasum,nodatasum,autodefrag,noautodefrag,degraded,device,discard,nodiscard,subvol,subvolid,space_cache,commit,noatime,flushoncommit,noflushoncommit,barrier,nobarrier
> btrfs_defaults=commit=1,noatime,compress=zstd,flushoncommit,barrier

I don't know how udisks2/mount_options.conf affects anything. It should have no effect on the root file system. Anyway, you really want to use either upstream default mount options or your distribution's default mount options. You will run into trouble much faster otherwise.

>
> /etc/udev/rules.d/99-disable-write-cache.rules
> ---
> ACTION=="add", SUBSYSTEM=="block", KERNEL=="sd[a-z]", 
> ENV{ID_USB_DRIVER}=="usb-storage", RUN+="/sbin/hdparm -W0 /dev/%k"
>
> But turning write caching off in hdparm is painfully slow, so for now 
> I've commented it out, relying solely on flushoncommit and commit=1

I don't think you'll be happy with the performance of commit=1 , it's too frequent. If there's a firmware bug resulting in flush or FUA transiently being ignored, then decreasing the commit interval just makes it more likely you'll run into a problem.

In my opinion the solution is frequent backups. Btrfs snapshots and send-receive make this quite cheap to do often. But any backup solution that you understand and have tested restore is the one you should use.

Best to reply to the list so responses are archived and everyone can chime in if they want.


-- 
Chris Murphy