backup: flock snapshot on backup start

An flock on the snapshot dir itself is used in addition to the group dir
lock. The lock is used to avoid races with forget and prune, while
having more granularity than the group lock (i.e. the group lock is
necessary to prevent more than one backup per group, but the snapshot
lock still allows backups unrelated to the currently running to be
forgotten/pruned).

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>

diff --git a/src/api2/backup.rs b/src/api2/backup.rs
index 4b019007d8194f01e238c381c6eb0017a1df31e1..f541eb97ff412b6433526374a9f4437449847f6d 100644 (file)
--- a/src/api2/backup.rs
+++ b/src/api2/backup.rs
@@ -106,7 +106,7 @@ async move {
         }
     }
 
-    let (path, is_new) = datastore.create_backup_dir(&backup_dir)?;
+    let (path, is_new, _snap_guard) = datastore.create_locked_backup_dir(&backup_dir)?;
     if !is_new { bail!("backup directory already exists."); }
 
     WorkerTask::spawn("backup", Some(worker_id), userid.clone(), true, move |worker| {
@@ -146,6 +146,7 @@ async move {
         async move {
             // keep flock until task ends
             let _group_guard = _group_guard;
+            let _snap_guard = _snap_guard;
 
             let res = select!{
                 req = req_fut => req,

diff --git a/src/backup/datastore.rs b/src/backup/datastore.rs
index 71544d20c3f432f23248385cfe38f5b5b5fa421f..37f581bcac709d181ec9677ae4a97aa6a79fd3d6 100644 (file)
--- a/src/backup/datastore.rs
+++ b/src/backup/datastore.rs
@@ -334,15 +334,20 @@ impl DataStore {
     /// Creates a new backup snapshot inside a BackupGroup
     ///
     /// The BackupGroup directory needs to exist.
-    pub fn create_backup_dir(&self, backup_dir: &BackupDir) ->  Result<(PathBuf, bool), io::Error> {
+    pub fn create_locked_backup_dir(&self, backup_dir: &BackupDir)
+        -> Result<(PathBuf, bool, DirLockGuard), Error>
+    {
         let relative_path = backup_dir.relative_path();
         let mut full_path = self.base_path();
         full_path.push(&relative_path);
 
+        let lock = ||
+            lock_dir_noblock(&full_path, "snapshot", "internal error - tried creating snapshot that's already in use");
+
         match std::fs::create_dir(&full_path) {
-            Ok(_) => Ok((relative_path, true)),
-            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => Ok((relative_path, false)),
-            Err(e) => Err(e)
+            Ok(_) => Ok((relative_path, true, lock()?)),
+            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => Ok((relative_path, false, lock()?)),
+            Err(e) => Err(e.into())
         }
     }
 

diff --git a/src/client/pull.rs b/src/client/pull.rs
index 05b7c66c87dca087cb5ce6b54f6aee090faf44ec..2428051ac34c3cf2c2549f43bb72252cf0f86b9e 100644 (file)
--- a/src/client/pull.rs
+++ b/src/client/pull.rs
@@ -297,7 +297,7 @@ pub async fn pull_snapshot_from(
     snapshot: &BackupDir,
 ) -> Result<(), Error> {
 
-    let (_path, is_new) = tgt_store.create_backup_dir(&snapshot)?;
+    let (_path, is_new, _snap_lock) = tgt_store.create_locked_backup_dir(&snapshot)?;
 
     if is_new {
         worker.log(format!("sync snapshot {:?}", snapshot.relative_path()));