[PATCH proxmox-backup 1/2] api: datastore: add option to run garbage collection before unmount

[Hannes Laimer <h.laimer@proxmox.com>]

Removable datastores set up for auto-unmount have no natural point at
which to run garbage collection, since the drive is unmounted right
after jobs finish. Expose a gc-on-unmount option so GC can be triggered
as part of the unmount for those setups.

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
---
 src/api2/admin/datastore.rs  | 33 +++++++++++++++++++++++++++------
 src/api2/config/datastore.rs |  9 +++++++++
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs
index 757b3114..5ce30c57 100644
--- a/src/api2/admin/datastore.rs
+++ b/src/api2/admin/datastore.rs
@@ -2641,15 +2641,36 @@ fn do_unmount_device(
 }
 
 async fn do_unmount(store: String, auth_id: Authid, to_stdout: bool) -> Result<Value, Error> {
-    let _lock = pbs_config::datastore::lock_config()?;
-    let (mut section_config, _digest) = pbs_config::datastore::config()?;
-    let mut datastore: DataStoreConfig = section_config.lookup("datastore", &store)?;
+    let gc_on_unmount = {
+        let _lock = pbs_config::datastore::lock_config()?;
+        let (section_config, _digest) = pbs_config::datastore::config()?;
+        let datastore: DataStoreConfig = section_config.lookup("datastore", &store)?;
 
-    if datastore.backing_device.is_none() {
-        bail!("datastore '{store}' is not removable");
+        if datastore.backing_device.is_none() {
+            bail!("datastore '{store}' is not removable");
+        }
+
+        ensure_datastore_is_mounted(&datastore)?;
+
+        datastore.gc_on_unmount.unwrap_or(false)
+    };
+
+    // Must happen outside the config lock, the GC handler acquires it too.
+    if gc_on_unmount {
+        let client = crate::client_helpers::connect_to_localhost()
+            .context("failed to connect to localhost for starting GC")?;
+        match client
+            .post(&format!("api2/json/admin/datastore/{store}/gc"), None)
+            .await
+        {
+            Ok(_) => info!("started garbage collection, unmount will wait for it to finish"),
+            Err(err) => warn!("unable to start garbage collection before unmount: {err}"),
+        }
     }
 
-    ensure_datastore_is_mounted(&datastore)?;
+    let _lock = pbs_config::datastore::lock_config()?;
+    let (mut section_config, _digest) = pbs_config::datastore::config()?;
+    let mut datastore: DataStoreConfig = section_config.lookup("datastore", &store)?;
 
     datastore.set_maintenance_mode(Some(MaintenanceMode {
         ty: MaintenanceType::Unmount,
diff --git a/src/api2/config/datastore.rs b/src/api2/config/datastore.rs
index c44d50d1..c0be0296 100644
--- a/src/api2/config/datastore.rs
+++ b/src/api2/config/datastore.rs
@@ -409,6 +409,8 @@ pub enum DeletableProperty {
     Comment,
     /// Delete the garbage collection schedule.
     GcSchedule,
+    /// Delete the gc-on-unmount property.
+    GcOnUnmount,
     /// Delete the prune job schedule.
     PruneSchedule,
     /// Delete the keep-last property
@@ -495,6 +497,9 @@ pub fn update_datastore(
                 DeletableProperty::GcSchedule => {
                     data.gc_schedule = None;
                 }
+                DeletableProperty::GcOnUnmount => {
+                    data.gc_on_unmount = None;
+                }
                 DeletableProperty::PruneSchedule => {
                     data.prune_schedule = None;
                 }
@@ -560,6 +565,10 @@ pub fn update_datastore(
         data.gc_schedule = update.gc_schedule;
     }
 
+    if update.gc_on_unmount.is_some() {
+        data.gc_on_unmount = update.gc_on_unmount;
+    }
+
     macro_rules! prune_disabled {
         ($(($param:literal, $($member:tt)+)),+) => {
             $(
-- 
2.47.3