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From: Shannon Sterz <s.sterz@proxmox.com>
To: pbs-devel@lists.proxmox.com
Subject: [pbs-devel] [PATCH proxmox-backup v7 3/4] fix #3935: datastore: move manifest locking to new locking method
Date: Tue, 11 Mar 2025 14:51:59 +0100	[thread overview]
Message-ID: <20250311135200.309896-4-s.sterz@proxmox.com> (raw)
In-Reply-To: <20250311135200.309896-1-s.sterz@proxmox.com>

adds double stat'ing and removes directory hierarchy to bring manifest
locking in-line with other locks used by the BackupDir trait.

if the old locking mechanism is still supposed to be used, this still
falls back to the previous lock file. however, we already add double
stat'ing since it is trivial to do here and should only provide better
safety when it comes to removing locks.

Signed-off-by: Shannon Sterz <s.sterz@proxmox.com>
---
 pbs-datastore/src/backup_info.rs | 45 ++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/pbs-datastore/src/backup_info.rs b/pbs-datastore/src/backup_info.rs
index fcfc6165..b276fba3 100644
--- a/pbs-datastore/src/backup_info.rs
+++ b/pbs-datastore/src/backup_info.rs
@@ -467,25 +467,41 @@ impl BackupDir {
     /// Returns the filename to lock a manifest
     ///
     /// Also creates the basedir. The lockfile is located in
-    /// '/run/proxmox-backup/locks/{datastore}/[ns/{ns}/]+{type}/{id}/{timestamp}.index.json.lck'
-    fn manifest_lock_path(&self) -> Result<PathBuf, Error> {
-        let mut path = PathBuf::from(&format!("/run/proxmox-backup/locks/{}", self.store.name()));
-        path.push(self.relative_path());
+    /// `${DATASTORE_LOCKS_DIR}/${datastore name}/${lock_file_path_helper(rpath)}.index.json.lck`
+    /// where rpath is the relative path of the snapshot.
+    fn manifest_lock_path(&self) -> PathBuf {
+        let path = Path::new(DATASTORE_LOCKS_DIR).join(self.store.name());
 
-        std::fs::create_dir_all(&path)?;
-        let ts = self.backup_time_string();
-        path.push(format!("{ts}{MANIFEST_LOCK_NAME}"));
+        let rpath = Path::new(self.dir.group.ty.as_str())
+            .join(&self.dir.group.id)
+            .join(&self.backup_time_string)
+            .join(MANIFEST_LOCK_NAME);
 
-        Ok(path)
+        path.join(lock_file_path_helper(&self.ns, rpath))
     }
 
     /// Locks the manifest of a snapshot, for example, to update or delete it.
     pub(crate) fn lock_manifest(&self) -> Result<BackupLockGuard, Error> {
-        let path = self.manifest_lock_path()?;
+        let path = if *OLD_LOCKING {
+            // old manifest lock path
+            let path = Path::new(DATASTORE_LOCKS_DIR)
+                .join(self.store.name())
+                .join(self.relative_path());
 
-        // actions locking the manifest should be relatively short, only wait a few seconds
-        open_backup_lockfile(&path, Some(std::time::Duration::from_secs(5)), true)
-            .map_err(|err| format_err!("unable to acquire manifest lock {:?} - {}", &path, err))
+            std::fs::create_dir_all(&path)?;
+
+            path.join(format!("{}{MANIFEST_LOCK_NAME}", self.backup_time_string()))
+        } else {
+            self.manifest_lock_path()
+        };
+
+        lock_helper(self.store.name(), &path, |p| {
+            // 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
+            open_backup_lockfile(p, Some(Duration::from_secs(5)), true)
+                .map_err(|err| format_err!("unable to acquire manifest lock {p:?} - {err}"))
+        })
     }
 
     /// Returns a file name for locking a snapshot.
@@ -559,10 +575,7 @@ impl BackupDir {
         })?;
 
         // remove no longer needed lock files
-        if let Ok(path) = self.manifest_lock_path() {
-            let _ = std::fs::remove_file(path); // ignore errors
-        }
-
+        let _ = std::fs::remove_file(self.manifest_lock_path()); // ignore errors
         let _ = std::fs::remove_file(self.lock_path()); // ignore errors
 
         Ok(())
-- 
2.39.5



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  parent reply	other threads:[~2025-03-11 13:52 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-11 13:51 [pbs-devel] [PATCH proxmox-backup v7 0/4] refactor datastore locking to use tmpfs Shannon Sterz
2025-03-11 13:51 ` [pbs-devel] [PATCH proxmox-backup v7 1/4] datastore/api/backup: prepare for fix of #3935 by adding lock helpers Shannon Sterz
2025-03-14  8:30   ` Christian Ebner
2025-03-11 13:51 ` [pbs-devel] [PATCH proxmox-backup v7 2/4] fix #3935: datastore/api/backup: move datastore locking to '/run' Shannon Sterz
2025-03-11 13:51 ` Shannon Sterz [this message]
2025-03-11 13:52 ` [pbs-devel] [PATCH proxmox-backup v7 4/4] fix: api: avoid race condition in set_backup_owner Shannon Sterz

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