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

pbs-datastore/src/datastore.rs

@@ -21,7 +21,7 @@ use pbs_api_types::{
     UPID, DataStoreConfig, Authid, GarbageCollectionStatus, HumanByte,
     ChunkOrder, DatastoreTuning,
 };
-use pbs_config::{open_backup_lockfile, BackupLockGuard};
+use pbs_config::{open_backup_lockfile, BackupLockGuard, ConfigVersionCache};
 
 use crate::DataBlob;
 use crate::backup_info::{BackupGroup, BackupDir};
@@ -63,26 +63,30 @@ pub struct DataStore {
     last_gc_status: Mutex<GarbageCollectionStatus>,
     verify_new: bool,
     chunk_order: ChunkOrder,
+    last_generation: usize,
+    last_update: i64,
 }
 
 impl DataStore {
     pub fn lookup_datastore(name: &str) -> Result<Arc<DataStore>, Error> {
+        let version_cache = ConfigVersionCache::new()?;
+        let generation = version_cache.datastore_generation();
+        let now = proxmox_time::epoch_i64();
+
+        let mut map = DATASTORE_MAP.lock().unwrap();
+        let entry = map.get(name);
+
+        if let Some(datastore) = &entry {
+            if datastore.last_generation == generation && now < (datastore.last_update + 60) {
+                return Ok(Arc::clone(datastore));
+            }
+        }
+
         let (config, _digest) = pbs_config::datastore::config()?;
         let config: DataStoreConfig = config.lookup("datastore", name)?;
         let path = PathBuf::from(&config.path);
 
-        let mut map = DATASTORE_MAP.lock().unwrap();
+        let datastore = DataStore::open_with_path(name, &path, config, generation, now)?;
-
-        if let Some(datastore) = map.get(name) {
-            // Compare Config - if changed, create new Datastore object!
-            if datastore.chunk_store.base() == path &&
-                datastore.verify_new == config.verify_new.unwrap_or(false)
-            {
-                return Ok(datastore.clone());
-            }
-        }
-
-        let datastore = DataStore::open_with_path(name, &path, config)?;
 
         let datastore = Arc::new(datastore);
         map.insert(name.to_string(), datastore.clone());
@@ -102,7 +106,13 @@ impl DataStore {
         Ok(())
     }
 
-    fn open_with_path(store_name: &str, path: &Path, config: DataStoreConfig) -> Result<Self, Error> {
+    fn open_with_path(
+        store_name: &str,
+        path: &Path,
+        config: DataStoreConfig,
+        last_generation: usize,
+        last_update: i64,
+    ) -> Result<Self, Error> {
         let chunk_store = ChunkStore::open(store_name, path)?;
 
         let mut gc_status_path = chunk_store.base_path();
@@ -131,6 +141,8 @@ impl DataStore {
             last_gc_status: Mutex::new(gc_status),
             verify_new: config.verify_new.unwrap_or(false),
             chunk_order,
+            last_generation,
+            last_update,
         })
     }