[pbs-devel] [PATCH backup] fix #3336: cleanup when deleting last snapshot

[Shannon Sterz]

On Thu Mar 6, 2025 at 1:08 PM CET, Maximiliano Sandoval wrote:
> When the last snapshot from a group is deleted we clear the entire
> group, this in turn cleans the owner for the group.
>
> Without this change, the user is unable to change the owner of the group
> after the last snapshot has been deleted. This would prevent a new
> backups to the same group from a different owner.
>
> Signed-off-by: Maximiliano Sandoval <m.sandoval at proxmox.com>
> ---
>  src/api2/admin/datastore.rs | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs
> index dbb7ae47..305673f1 100644
> --- a/src/api2/admin/datastore.rs
> +++ b/src/api2/admin/datastore.rs
> @@ -423,10 +423,20 @@ pub async fn delete_snapshot(
>              &backup_dir.group,
>          )?;
>
> -        let snapshot = datastore.backup_dir(ns, backup_dir)?;
> +        let snapshot = datastore.backup_dir(ns.clone(), backup_dir)?;
>
>          snapshot.destroy(false)?;
>
> +        let group = BackupGroup::from(snapshot);
> +        if group.list_backups().is_ok_and(|backups| backups.is_empty()) {
> +            if let Err(err) = datastore.remove_backup_group(&ns, group.as_ref()) {
> +                log::error!(
> +                    "error while cleaning group {path:?} - {err}",
> +                    path = group.full_group_path()
> +                );
> +            }
> +        }
> +

this bug... looks so harmless, but comes back to haunt me every time. as
explained by wobu here [1] it is not really possible to cleanly fix this
bug without reworking our locking mechanism. i did send some patches for
that (checks notes) almost 3 years ago ^^', but they are still not
applied and definitively need a rework at this point [2]. i can pick
this up again, sorry got focused on other things in the meantime.

[1]: https://lore.proxmox.com/pbs-devel/20220314093617.n2mc2jv4k6ntzroo@wobu-vie.proxmox.com/
[2]: https://lore.proxmox.com/pbs-devel/20220824124829.392189-1-s.sterz@proxmox.com/

>          Ok(Value::Null)
>      })
>      .await?