[pbs-devel] [PATCH v2 proxmox-backup 3/7] datastore: prevent in-use deletion with locks instead of heuristic

[Stefan Reiter]

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 at proxmox.com>
---

For this to actually work the following patches are obviously necessary, but I
wanted to keep them seperate for review.

 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);
-- 
2.20.1