[pbs-devel] [PATCH proxmox-backup 2/2] fix #4904: tape changer: add option to eject before unload

[Dominik Csapak <d.csapak@proxmox.com>]

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 | 28 +++++++++++++++++++++++++++-
 src/api2/config/changer.rs        |  9 +++++++++
 src/bin/proxmox_tape/changer.rs   |  1 +
 src/tape/changer/mod.rs           | 21 +++++++++++++++++++--
 src/tape/drive/lto/mod.rs         |  5 +++++
 5 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/pbs-api-types/src/tape/changer.rs b/pbs-api-types/src/tape/changer.rs
index c9c7fcaa..e3cf27c1 100644
--- a/pbs-api-types/src/tape/changer.rs
+++ b/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(
diff --git a/src/api2/config/changer.rs b/src/api2/config/changer.rs
index 01908e3b..bff9ed9e 100644
--- a/src/api2/config/changer.rs
+++ b/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)?;
diff --git a/src/bin/proxmox_tape/changer.rs b/src/bin/proxmox_tape/changer.rs
index d1ddb5e0..a8bff173 100644
--- a/src/bin/proxmox_tape/changer.rs
+++ b/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);
diff --git a/src/tape/changer/mod.rs b/src/tape/changer/mod.rs
index bf0a15f4..df63f6f8 100644
--- a/src/tape/changer/mod.rs
+++ b/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 {
diff --git a/src/tape/drive/lto/mod.rs b/src/tape/drive/lto/mod.rs
index 2c3a5a63..955dbdf7 100644
--- a/src/tape/drive/lto/mod.rs
+++ b/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 {
-- 
2.39.2