From 6d6b4e72d38a35510003c1d0c1cdf1a913fc56bd Mon Sep 17 00:00:00 2001
From: Stefan Reiter <s.reiter@proxmox.com>
Date: Tue, 11 Aug 2020 10:50:38 +0200
Subject: [PATCH] datastore: prevent in-use deletion with locks instead of
 heuristic

Attempt to lock the backup directory to be deleted, if it works keep the
lock until the deletion is complete. This way we ensure that no other
locking operation (e.g. using a snapshot as base for another backup) can
happen concurrently.

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
---
 src/backup/datastore.rs | 40 ++++------------------------------------
 1 file changed, 4 insertions(+), 36 deletions(-)

diff --git a/src/backup/datastore.rs b/src/backup/datastore.rs
index 01695f48..71544d20 100644
--- a/src/backup/datastore.rs
+++ b/src/backup/datastore.rs
@@ -11,7 +11,7 @@ use serde_json::Value;
 
 use proxmox::tools::fs::{replace_file, CreateOptions};
 
-use super::backup_info::{BackupGroup, BackupDir, BackupInfo};
+use super::backup_info::{BackupGroup, BackupDir};
 use super::chunk_store::ChunkStore;
 use super::dynamic_index::{DynamicIndexReader, DynamicIndexWriter};
 use super::fixed_index::{FixedIndexReader, FixedIndexWriter};
@@ -200,19 +200,7 @@ impl DataStore {
 
         let full_path = self.group_path(backup_group);
 
-        let mut snap_list = backup_group.list_backups(&self.base_path())?;
-        BackupInfo::sort_list(&mut snap_list, false);
-        for snap in snap_list {
-            if snap.is_finished() {
-                break;
-            } else {
-                bail!(
-                    "cannot remove backup group {:?}, contains potentially running backup: {}",
-                    full_path,
-                    snap.backup_dir
-                );
-            }
-        }
+        let _guard = tools::fs::lock_dir_noblock(&full_path, "backup group", "possible running backup")?;
 
         log::info!("removing backup group {:?}", full_path);
         std::fs::remove_dir_all(&full_path)
@@ -232,29 +220,9 @@ impl DataStore {
 
         let full_path = self.snapshot_path(backup_dir);
 
+        let _guard;
         if !force {
-            let mut snap_list = backup_dir.group().list_backups(&self.base_path())?;
-            BackupInfo::sort_list(&mut snap_list, false);
-            let mut prev_snap_finished = true;
-            for snap in snap_list {
-                let cur_snap_finished = snap.is_finished();
-                if &snap.backup_dir == backup_dir {
-                    if !cur_snap_finished {
-                        bail!(
-                            "cannot remove currently running snapshot: {:?}",
-                            backup_dir
-                        );
-                    }
-                    if !prev_snap_finished {
-                        bail!(
-                            "cannot remove snapshot {:?}, successor is currently running and potentially based on it",
-                            backup_dir
-                        );
-                    }
-                    break;
-                }
-                prev_snap_finished = cur_snap_finished;
-            }
+            _guard = lock_dir_noblock(&full_path, "snapshot", "possibly running or used as base")?;
         }
 
         log::info!("removing backup snapshot {:?}", full_path);