[pbs-devel] [PATCH proxmox-backup v2] backup/datastore: move manifest locking to /run

[Dominik Csapak <d.csapak@proxmox.com>]

this fixes the issue that on some filesystems, you cannot recursively
remove a directory when you hold a lock on a file inside (e.g. nfs/cifs)

it is not really backwards compatible (so during an upgrade, there
could be two daemons have the lock), but since the locking was
broken before (see previous patch) it should not really matter
(also it seems very unlikely that someone will trigger this)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
changes from v1:
* document the path method
* use String instead of PathBuf and use write! to change it
 src/backup/datastore.rs | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/src/backup/datastore.rs b/src/backup/datastore.rs
index 0f74ac3c..19e7ccba 100644
--- a/src/backup/datastore.rs
+++ b/src/backup/datastore.rs
@@ -257,6 +257,12 @@ impl DataStore {
                 )
             })?;
 
+        // the manifest does not exists anymore, we do not need to keep the lock
+        if let Ok(path) = self.manifest_lock_path(backup_dir) {
+            // ignore errors
+            let _ = std::fs::remove_file(path);
+        }
+
         Ok(())
     }
 
@@ -698,13 +704,32 @@ impl DataStore {
         ))
     }
 
+    /// Returns the filename to lock a manifest
+    ///
+    /// Also creates the basedir. The lockfile is located in
+    /// '/run/proxmox-backup/locks/{datastore}/{type}/{id}/{timestamp}.index.json.lck'
+    fn manifest_lock_path(
+        &self,
+        backup_dir: &BackupDir,
+    ) -> Result<String, Error> {
+        let mut path = format!(
+            "/run/proxmox-backup/locks/{}/{}/{}",
+            self.name(),
+            backup_dir.group().backup_type(),
+            backup_dir.group().backup_id(),
+        );
+        std::fs::create_dir_all(&path)?;
+        use std::fmt::Write;
+        write!(path, "/{}{}", backup_dir.backup_time_string(), &MANIFEST_LOCK_NAME)?;
+
+        Ok(path)
+    }
+
     fn lock_manifest(
         &self,
         backup_dir: &BackupDir,
     ) -> Result<File, Error> {
-        let mut path = self.base_path();
-        path.push(backup_dir.relative_path());
-        path.push(&MANIFEST_LOCK_NAME);
+        let path = self.manifest_lock_path(backup_dir)?;
 
         // update_manifest should never take a long time, so if someone else has
         // the lock we can simply block a bit and should get it soon
-- 
2.20.1