[PATCH proxmox 5/5] pbs-api-types: add GarbageCollection maintenance mode

[Robert Obkircher <r.obkircher@proxmox.com>]

This mode may be used to safely prune and garbage collect a datastore
without the risk of running out of space due to new backups.

Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
 pbs-api-types/src/datastore.rs   |  1 +
 pbs-api-types/src/maintenance.rs | 11 +++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/pbs-api-types/src/datastore.rs b/pbs-api-types/src/datastore.rs
index b770bc03..f54af000 100644
--- a/pbs-api-types/src/datastore.rs
+++ b/pbs-api-types/src/datastore.rs
@@ -649,6 +649,7 @@ impl DataStoreConfig {
 
         match current_type {
             Some(MaintenanceType::ReadOnly) => { /* always OK  */ }
+            Some(MaintenanceType::GarbageCollection) => { /* always OK  */ }
             Some(MaintenanceType::Offline) => { /* always OK  */ }
             Some(MaintenanceType::Unmount) => {
                 /* used to reset it after failed unmount, or alternative for aborting unmount task */
diff --git a/pbs-api-types/src/maintenance.rs b/pbs-api-types/src/maintenance.rs
index 2d11aff2..abbdbf3f 100644
--- a/pbs-api-types/src/maintenance.rs
+++ b/pbs-api-types/src/maintenance.rs
@@ -42,12 +42,11 @@ pub enum Operation {
 #[serde(rename_all = "kebab-case")]
 /// Maintenance type.
 pub enum MaintenanceType {
-    // TODO:
-    //  - Add "GarbageCollection" or "DeleteOnly" as type and track GC (or all deletes) as separate
-    //    operation, so that one can enable a mode where nothing new can be added but stuff can be
-    //    cleaned
     /// Only read operations are allowed on the datastore.
     ReadOnly,
+    /// Allow reads and non-expanding writes, but disallow writes
+    /// that may increase storage usage.
+    GarbageCollection,
     /// Neither read nor write operations are allowed on the datastore.
     Offline,
     /// The datastore is being deleted.
@@ -110,6 +109,10 @@ impl MaintenanceMode {
             (MaintenanceType::ReadOnly, Operation::Write | Operation::WriteNonExpanding) => {
                 bail!("read-only maintenance mode: {message}")
             }
+            (MaintenanceType::GarbageCollection, Operation::Write) => {
+                bail!("garbage-collection maintenance mode: {message}")
+            }
+            (MaintenanceType::GarbageCollection, _) => Ok(()),
             #[cfg(feature = "enum-fallback")]
             (MaintenanceType::UnknownEnumValue(m), _) => bail!("unknown maintenance mode: {m}"),
         }
-- 
2.47.3