fix #4904: tape changer: add option to eject before unload

some tape libraries need the tape being ejected from the drive before
doing an unload. Since we cannot easily detect if that's the case,
introduce an 'eject_before_unload' option.

Instead of just adding a bool flag to the config, add a new 'options'
property string where we can put such niche options similar to how we
handle the datastore tuning options.

Extend the LtoTapeHandle with 'medium_present' which just uses a
TEST UNIT READY command to check for present medium, so we don't
try to eject an already ejected tape.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

pbs-api-types/src/tape/changer.rs

@@ -3,7 +3,7 @@
 use serde::{Deserialize, Serialize};
 
 use proxmox_schema::{
-    api, ApiStringFormat, ArraySchema, IntegerSchema, Schema, StringSchema, Updater,
+    api, ApiStringFormat, ApiType, ArraySchema, IntegerSchema, Schema, StringSchema, Updater,
 };
 
 use crate::{OptionalDeviceIdentification, PROXMOX_SAFE_ID_FORMAT};
@@ -39,6 +39,26 @@ Import/Export, i.e. any media in those slots are considered to be
 .format(&ApiStringFormat::PropertyString(&SLOT_ARRAY_SCHEMA))
 .schema();
 
+fn is_false(b: &bool) -> bool {
+    !b
+}
+
+#[api]
+#[derive(Serialize, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+/// Options for Changers
+pub struct ChangerOptions {
+    #[serde(default, skip_serializing_if = "is_false")]
+    /// if set to true, tapes are ejected manually before unloading
+    pub eject_before_unload: bool,
+}
+
+pub const CHANGER_OPTIONS_STRING_SCHEMA: Schema = StringSchema::new("Changer options")
+    .format(&ApiStringFormat::PropertyString(
+        &ChangerOptions::API_SCHEMA,
+    ))
+    .schema();
+
 #[api(
     properties: {
         name: {
@@ -51,6 +71,10 @@ Import/Export, i.e. any media in those slots are considered to be
             schema: EXPORT_SLOT_LIST_SCHEMA,
             optional: true,
         },
+        options: {
+            optional: true,
+            schema: CHANGER_OPTIONS_STRING_SCHEMA,
+        },
     },
 )]
 #[derive(Serialize, Deserialize, Updater)]
@@ -62,6 +86,8 @@ pub struct ScsiTapeChanger {
     pub path: String,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub export_slots: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub options: Option<String>,
 }
 
 #[api(

src/api2/config/changer.rs

@@ -138,6 +138,8 @@ pub fn list_changers(
 pub enum DeletableProperty {
     /// Delete export-slots.
     ExportSlots,
+    /// Delete options.
+    Options,
 }
 
 #[api(
@@ -194,6 +196,9 @@ pub fn update_changer(
                 DeletableProperty::ExportSlots => {
                     data.export_slots = None;
                 }
+                DeletableProperty::Options => {
+                    data.options = None;
+                }
             }
         }
     }
@@ -222,6 +227,10 @@ pub fn update_changer(
         }
     }
 
+    if let Some(options) = update.options {
+        data.options = Some(options);
+    }
+
     config.set_data(&name, "changer", &data)?;
 
     pbs_config::drive::save_config(&config)?;

src/bin/proxmox_tape/changer.rs

@@ -161,6 +161,7 @@ fn get_config(param: Value, rpcenv: &mut dyn RpcEnvironment) -> Result<(), Error
     let options = default_table_format_options()
         .column(ColumnConfig::new("name"))
         .column(ColumnConfig::new("path"))
+        .column(ColumnConfig::new("options"))
         .column(ColumnConfig::new("export-slots"));
 
     format_and_print_result_full(&mut data, &info.returns, &output_format, &options);

src/tape/changer/mod.rs

@@ -4,6 +4,7 @@ pub mod mtx;
 
 mod online_status_map;
 pub use online_status_map::*;
+use proxmox_schema::ApiType;
 
 use std::path::PathBuf;
 
@@ -11,9 +12,11 @@ use anyhow::{bail, Error};
 
 use proxmox_sys::fs::{file_read_optional_string, replace_file, CreateOptions};
 
-use pbs_api_types::{LtoTapeDrive, ScsiTapeChanger};
+use pbs_api_types::{ChangerOptions, LtoTapeDrive, ScsiTapeChanger};
 
-use pbs_tape::{sg_pt_changer, ElementStatus, MtxStatus};
+use pbs_tape::{linux_list_drives::open_lto_tape_device, sg_pt_changer, ElementStatus, MtxStatus};
+
+use crate::tape::drive::{LtoTapeHandle, TapeDriver};
 
 /// Interface to SCSI changer devices
 pub trait ScsiMediaChange {
@@ -425,6 +428,20 @@ impl MediaChange for MtxMediaChanger {
     }
 
     fn unload_media(&mut self, target_slot: Option<u64>) -> Result<MtxStatus, Error> {
+        let options: ChangerOptions = serde_json::from_value(
+            ChangerOptions::API_SCHEMA
+                .parse_property_string(self.config.options.as_deref().unwrap_or_default())?,
+        )?;
+
+        if options.eject_before_unload {
+            let file = open_lto_tape_device(&self.drive.path)?;
+            let mut handle = LtoTapeHandle::new(file)?;
+
+            if handle.medium_present() {
+                handle.eject_media()?;
+            }
+        }
+
         if let Some(target_slot) = target_slot {
             self.config.unload(target_slot, self.drive_number())
         } else {

src/tape/drive/lto/mod.rs

@@ -162,6 +162,11 @@ impl LtoTapeHandle {
             .set_medium_removal(true)
             .map_err(|err| format_err!("unlock door failed - {}", err))
     }
+
+    /// Returns if a medium is present
+    pub fn medium_present(&mut self) -> bool {
+        self.sg_tape.test_unit_ready().is_ok()
+    }
 }
 
 impl TapeDriver for LtoTapeHandle {