datastore: remove datastore from internal cache based on maintenance mode

We keep a DataStore cache, so ChunkStore's and lock files are kept by
the proxy process and don't have to be reopened every time. However,
for specific maintenance modes, e.g. 'offline', our process should not
keep file in that datastore open. This clears the cache entry of a
datastore if it is in a specific maintanance mode and the last task
finished, which also drops any files still open by the process.

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
Reviewed-by: Gabriel Goller <g.goller@proxmox.com>
Tested-by: Gabriel Goller <g.goller@proxmox.com>

pbs-api-types/src/maintenance.rs

@@ -77,6 +77,12 @@ pub struct MaintenanceMode {
 }
 
 impl MaintenanceMode {
+    /// Used for deciding whether the datastore is cleared from the internal cache after the last
+    /// task finishes, so all open files are closed.
+    pub fn is_offline(&self) -> bool {
+        self.ty == MaintenanceType::Offline
+    }
+
     pub fn check(&self, operation: Option<Operation>) -> Result<(), Error> {
         if self.ty == MaintenanceType::Delete {
             bail!("datastore is being deleted");