ZFS block cloning/dnode_is_dirty bug

[Randell]

I just stumbled over this and I was wondering how it relates to the versions of zfs here in the proxmox kernel? It seems like there is a bug that's been around that seemed a while that was brought to light with the latest block cloning code, or maybe they are 2 different bugs, I don't really know.

https://news.ycombinator.com/item?id=38380240
https://github.com/openzfs/zfs/pull/15571

It also seems like there is a lot of panic by people, so, to be honest, I have no idea how large of an issue this is, and how or if I have been impacted yet. I'm sure the Proxmox team is aware and are evaluating.

 

[broadband9]

Seems like the feature is enabled as per this command:

zpool get feature@block_cloning ssd

(ssd is my zpool name)

my output :

NAME  PROPERTY               VALUE                  SOURCE
ssd   feature@block_cloning  enabled                local

Hence my version 8.1.3 is enabled with block_cloning.

Edit:
My test above was done on a Fresh 8.1.3 server, whilst my other which was upgraded from 8.0 to 8.1.3 does not have this feature enabled even though it has zfs 2.2.0 version installed.

Edit #2:

My other cluster which I upgraded has the feature installed but not enabled. Which i'm thankful for.
So I think depending on the installation and upgrade path either it's installed and enabled, or disabled or not even installed lol:

root@MAN20:~# zpool get feature@block_cloning VmData
NAME    PROPERTY               VALUE                  SOURCE
VmData  feature@block_cloning  disabled               local

 

[Randell]

I think that block_cloning needs to be enabled with zpool upgrade on existing pools which is why you have different results.

 

[fabian]

please check the existing threads as well! irrespective of whether your pool has the block_cloning feature enabled or not, ZFS 2.2 as shipped with PVE 8.1 disables block cloning by default via the tunable "zfs_bclone_enabled". unless you override that, no block cloning will happen.

 

[antipiot]

please check the existing threads as well! irrespective of whether your pool has the block_cloning feature enabled or not, ZFS 2.2 as shipped with PVE 8.1 disables block cloning by default via the tunable "zfs_bclone_enabled". unless you override that, no block cloning will happen.

Hi!
trying to understand a bit and ensure everything is OK:
I've just upgraded my proxmox and checking block cloning status shows that block cloning is disabled.

Then i upgraded the pool using

zpool upgrade -a

and checked status again: block_cloning was enable.

rpool feature@block_cloning          enabled                        local

Am i missing something?

root@pve1:~# zpool set feature@block_cloning=disabled rpool
cannot set property for 'rpool': property 'feature@block_cloning' can only be set to 'disabled' at creation time

Regards

 

[TobiasV]

Am i missing something?

Yes. It is disabled in the zfs module parameters. You can check that with

cat /sys/module/zfs/parameters/zfs_bclone_enabled

 

[fabian]

yes, like @TobiasV said - you need both the pool feature and the tunable to enable it, and the tunable is off by default in PVE.

 

[antipiot]

Yes. It is disabled in the zfs module parameters. You can check that with

cat /sys/module/zfs/parameters/zfs_bclone_enabled

Thanks you very much, this was what i was looking for!

 

[garetht]

More information on the ZFS bug that is triggering this can be found here: [PSA] ZFS Silent Data Corruption