pbs-datastore: use ConfigVersionCache for datastore

instead of relying on the content of some configs

previously, we always read and parsed the config file, and only
generated a new config object when the path or the 'verify-new' option
changed.

now, we increase the datastore generation on config save, and if that
changed (or the last load is 1 minute in the past), we always
generate a new object

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

pbs-config/src/config_version_cache.rs

@@ -24,10 +24,12 @@ struct ConfigVersionCacheData {
     user_cache_generation: AtomicUsize,
     // Traffic control (traffic-control.cfg) generation/version.
     traffic_control_generation: AtomicUsize,
+    // datastore (datastore.cfg) generation/version
+    datastore_generation: AtomicUsize,
 
     // Add further atomics here (and reduce padding size)
 
-    padding: [u8; 4096 - 3*8],
+    padding: [u8; 4096 - 4*8],
 }
 
 
@@ -118,4 +120,18 @@ impl ConfigVersionCache {
             .fetch_add(1, Ordering::AcqRel);
     }
 
+    /// Returns the datastore generation number.
+    pub fn datastore_generation(&self) -> usize {
+        self.shmem
+            .data()
+            .datastore_generation
+            .load(Ordering::Acquire)
+    }
+
+    /// Increase the datastore generation number.
+    pub fn increase_datastore_generation(&self) -> usize {
+        self.shmem
+            .data()
+            .datastore_generation.fetch_add(1, Ordering::Acquire)
+    }
 }

pbs-config/src/datastore.rs

@@ -7,7 +7,7 @@ use proxmox_section_config::{SectionConfig, SectionConfigData, SectionConfigPlug
 
 use pbs_api_types::{DataStoreConfig, DATASTORE_SCHEMA};
 
-use crate::{open_backup_lockfile, replace_backup_config, BackupLockGuard};
+use crate::{open_backup_lockfile, replace_backup_config, BackupLockGuard, ConfigVersionCache};
 
 lazy_static! {
     pub static ref CONFIG: SectionConfig = init();
@@ -46,7 +46,14 @@ pub fn config() -> Result<(SectionConfigData, [u8;32]), Error> {
 
 pub fn save_config(config: &SectionConfigData) -> Result<(), Error> {
     let raw = CONFIG.write(DATASTORE_CFG_FILENAME, config)?;
-    replace_backup_config(DATASTORE_CFG_FILENAME, raw.as_bytes())
+    replace_backup_config(DATASTORE_CFG_FILENAME, raw.as_bytes())?;
+
+    // increase datastore version
+    // We use this in pbs-datastore
+    let version_cache = ConfigVersionCache::new()?;
+    version_cache.increase_datastore_generation();
+
+    Ok(())
 }
 
 // shell completion helper