backup/datastore: save garbage collection status to disk

and load it again when opening it

this way we can persist the status of the last garbage collect across
daemon reloads and reboots

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

src/backup/datastore.rs

@@ -9,7 +9,7 @@ use std::fs::File;
 use anyhow::{bail, format_err, Error};
 use lazy_static::lazy_static;
 
-use proxmox::tools::fs::{replace_file, CreateOptions, open_file_locked};
+use proxmox::tools::fs::{replace_file, file_read_optional_string, CreateOptions, open_file_locked};
 
 use super::backup_info::{BackupGroup, BackupDir};
 use super::chunk_store::ChunkStore;
@@ -71,7 +71,20 @@ impl DataStore {
     fn open_with_path(store_name: &str, path: &Path, config: DataStoreConfig) -> Result<Self, Error> {
         let chunk_store = ChunkStore::open(store_name, path)?;
 
-        let gc_status = GarbageCollectionStatus::default();
+        let mut gc_status_path = chunk_store.base_path();
+        gc_status_path.push(".gc-status");
+
+        let gc_status = if let Some(state) = file_read_optional_string(gc_status_path)? {
+            match serde_json::from_str(&state) {
+                Ok(state) => state,
+                Err(err) => {
+                    eprintln!("error reading gc-status: {}", err);
+                    GarbageCollectionStatus::default()
+                }
+            }
+        } else {
+            GarbageCollectionStatus::default()
+        };
 
         Ok(Self {
             chunk_store: Arc::new(chunk_store),
@@ -572,6 +585,23 @@ impl DataStore {
                 crate::task_log!(worker, "Average chunk size: {}", HumanByte::from(avg_chunk));
             }
 
+            if let Ok(serialized) = serde_json::to_string(&gc_status) {
+                let mut path = self.base_path();
+                path.push(".gc-status");
+
+                let backup_user = crate::backup::backup_user()?;
+                let mode = nix::sys::stat::Mode::from_bits_truncate(0o0644);
+                // set the correct owner/group/permissions while saving file
+                // owner(rw) = backup, group(r)= backup
+                let options = CreateOptions::new()
+                    .perm(mode)
+                    .owner(backup_user.uid)
+                    .group(backup_user.gid);
+
+                // ignore errors
+                let _ = replace_file(path, serialized.as_bytes(), options);
+            }
+
             *self.last_gc_status.lock().unwrap() = gc_status;
 
         } else {