[pbs-devel] [PATCH proxmox-backup 02/10] server/worker_task: refactor locking of the task list

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

also add the functionality of having a 'shared' (read) lock for the list
we will need this later

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/server/worker_task.rs | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/server/worker_task.rs b/src/server/worker_task.rs
index 771e8447..d220e755 100644
--- a/src/server/worker_task.rs
+++ b/src/server/worker_task.rs
@@ -15,7 +15,7 @@ use tokio::sync::oneshot;
 
 use proxmox::sys::linux::procfs;
 use proxmox::try_block;
-use proxmox::tools::fs::{create_path, open_file_locked, replace_file, CreateOptions};
+use proxmox::tools::fs::{create_path, open_file_locked, open_file_locked_shared, replace_file, CreateOptions};
 
 use super::UPID;
 
@@ -325,6 +325,19 @@ pub struct TaskListInfo {
     pub state: Option<TaskState>, // endtime, status
 }
 
+fn lock_task_list_files(exclusive: bool) -> Result<std::fs::File, Error> {
+    let backup_user = crate::backup::backup_user()?;
+
+    let lock = if exclusive {
+        open_file_locked(PROXMOX_BACKUP_TASK_LOCK_FN, std::time::Duration::new(10, 0))?
+    } else {
+        open_file_locked_shared(PROXMOX_BACKUP_TASK_LOCK_FN, std::time::Duration::new(10, 0))?
+    };
+    nix::unistd::chown(PROXMOX_BACKUP_TASK_LOCK_FN, Some(backup_user.uid), Some(backup_user.gid))?;
+
+    Ok(lock)
+}
+
 // atomically read/update the task list, update status of finished tasks
 // new_upid is added to the list when specified.
 // Returns a sorted list of known tasks,
@@ -332,8 +345,7 @@ fn update_active_workers(new_upid: Option<&UPID>) -> Result<Vec<TaskListInfo>, E
 
     let backup_user = crate::backup::backup_user()?;
 
-    let lock = open_file_locked(PROXMOX_BACKUP_TASK_LOCK_FN, std::time::Duration::new(10, 0))?;
-    nix::unistd::chown(PROXMOX_BACKUP_TASK_LOCK_FN, Some(backup_user.uid), Some(backup_user.gid))?;
+    let lock = lock_task_list_files(true)?;
 
     let reader = match File::open(PROXMOX_BACKUP_ACTIVE_TASK_FN) {
         Ok(f) => Some(BufReader::new(f)),
-- 
2.20.1