Re: [pbs-devel] [PATCH proxmox-backup v3 05/24] add helper for checking if a removable datastore is available

[Christian Ebner <c.ebner@proxmox.com>]

some comments inline

On 4/9/24 12:59, Hannes Laimer wrote:
> Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
> ---
>   pbs-datastore/src/datastore.rs | 18 ++++++++++++++++++
>   pbs-datastore/src/lib.rs       |  2 +-
>   2 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
> index 0685cc84..db47205c 100644
> --- a/pbs-datastore/src/datastore.rs
> +++ b/pbs-datastore/src/datastore.rs
> @@ -49,6 +49,22 @@ pub fn check_backup_owner(owner: &Authid, auth_id: &Authid) -> Result<(), Error>
>       Ok(())
>   }
>   
> +pub fn check_if_available(config: &DataStoreConfig) -> Result<(), Error> {

the function signature suggests that this checks if the datastore is 
available, so maybe call this `is_datastore_available` and let it return 
a boolean instead, further distinguishing between error states because 
of runtime errors and the datastore simply not being available.

> +    config.backing_device.as_ref().map_or(Ok(()), |uuid| {
> +        let mut command = std::process::Command::new("findmnt");
> +        command.args(["-n", "-o", "TARGET", "--source", &format!("UUID={uuid}")]);
> +
> +        match proxmox_sys::command::run_command(command, None) {
> +            Ok(mount_point) if mount_point.trim_end() == config.path => Ok(()),
> +            _ => Err(format_err!(

this should distinguish between an error because of the `run_command` 
failing because of e.g. outdated/incompatible command line arguments 
passed to `findmnt` and the filesystem not being mounted.
I see however that `findmnt` only has 2 error codes, so maybe this could 
be done by using `lsblk` and filtering the output based on the `uuid` 
instead, but there might be better solutions that I am not aware of.

> +                "device for datastore '{}' has to be mounted at '{}'",

should actually be the filesystem on the device that needs to be 
mounted, not the device?

> +                config.name,
> +                config.path
> +            )),
> +        }
> +    })
> +}
> +
>   /// Datastore Management
>   ///
>   /// A Datastore can store severals backups, and provides the
> @@ -261,6 +277,8 @@ impl DataStore {
>       ) -> Result<Arc<Self>, Error> {
>           let name = config.name.clone();
>   
> +        check_if_available(&config)?;
> +
>           let tuning: DatastoreTuning = serde_json::from_value(
>               DatastoreTuning::API_SCHEMA
>                   .parse_property_string(config.tuning.as_deref().unwrap_or(""))?,
> diff --git a/pbs-datastore/src/lib.rs b/pbs-datastore/src/lib.rs
> index 43050162..f5e93e92 100644
> --- a/pbs-datastore/src/lib.rs
> +++ b/pbs-datastore/src/lib.rs
> @@ -206,7 +206,7 @@ pub use manifest::BackupManifest;
>   pub use store_progress::StoreProgress;
>   
>   mod datastore;
> -pub use datastore::{check_backup_owner, DataStore};
> +pub use datastore::{check_backup_owner, check_if_available, DataStore};
>   
>   mod hierarchy;
>   pub use hierarchy::{