[PATCH proxmox-backup 3/4] datastore: move file lock helper to centralized place

[Christian Ebner <c.ebner@proxmox.com>]

Moves the implementation to a more central location, as it is not
only used by the datastore contents, but also by the chunk store.

No functional changes.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
 pbs-datastore/src/backup_info.rs | 35 ++------------------------------
 pbs-datastore/src/chunk_store.rs |  2 +-
 pbs-datastore/src/lib.rs         | 34 +++++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 34 deletions(-)

diff --git a/pbs-datastore/src/backup_info.rs b/pbs-datastore/src/backup_info.rs
index 9919b908a..bae136d3c 100644
--- a/pbs-datastore/src/backup_info.rs
+++ b/pbs-datastore/src/backup_info.rs
@@ -1,5 +1,5 @@
 use std::fmt;
-use std::os::unix::io::{AsRawFd, RawFd};
+use std::os::unix::io::RawFd;
 use std::os::unix::prelude::OsStrExt;
 use std::path::Path;
 use std::path::PathBuf;
@@ -24,7 +24,7 @@ use crate::datastore::{GROUP_NOTES_FILE_NAME, GROUP_OWNER_FILE_NAME};
 use crate::manifest::{BackupManifest, MANIFEST_LOCK_NAME};
 use crate::move_journal;
 use crate::s3::S3_CONTENT_PREFIX;
-use crate::{DataBlob, DataStore, DatastoreBackend, DATASTORE_LOCKS_DIR};
+use crate::{lock_helper, DataBlob, DataStore, DatastoreBackend, DATASTORE_LOCKS_DIR};
 
 pub const PROTECTED_MARKER_FILENAME: &str = ".protected";
 
@@ -1210,34 +1210,3 @@ fn lock_file_path_helper(ns: &BackupNamespace, path: PathBuf) -> PathBuf {
 
     to_return.join(format!("{first_eigthy}...{last_eighty}-{hash}"))
 }
-
-/// Helps implement the double stat'ing procedure. It avoids certain race conditions upon lock
-/// deletion.
-///
-/// It also creates the base directory for lock files.
-pub(crate) fn lock_helper<F>(
-    store_name: &str,
-    path: &std::path::Path,
-    lock_fn: F,
-) -> Result<BackupLockGuard, Error>
-where
-    F: Fn(&std::path::Path) -> Result<BackupLockGuard, Error>,
-{
-    let mut lock_dir = Path::new(DATASTORE_LOCKS_DIR).join(store_name);
-
-    if let Some(parent) = path.parent() {
-        lock_dir = lock_dir.join(parent);
-    };
-
-    std::fs::create_dir_all(&lock_dir)?;
-
-    let lock = lock_fn(path)?;
-
-    let inode = nix::sys::stat::fstat(lock.as_raw_fd())?.st_ino;
-
-    if nix::sys::stat::stat(path).map_or(true, |st| inode != st.st_ino) {
-        bail!("could not acquire lock, another thread modified the lock file");
-    }
-
-    Ok(lock)
-}
diff --git a/pbs-datastore/src/chunk_store.rs b/pbs-datastore/src/chunk_store.rs
index 5b07ebdaa..778897974 100644
--- a/pbs-datastore/src/chunk_store.rs
+++ b/pbs-datastore/src/chunk_store.rs
@@ -944,7 +944,7 @@ impl ChunkStore {
         timeout: Duration,
     ) -> Result<BackupLockGuard, Error> {
         let lock_path = self.chunk_lock_path(digest);
-        let guard = crate::backup_info::lock_helper(self.name(), &lock_path, |path| {
+        let guard = crate::lock_helper(self.name(), &lock_path, |path| {
             pbs_config::open_backup_lockfile(path, Some(timeout), true)
         })?;
         Ok(guard)
diff --git a/pbs-datastore/src/lib.rs b/pbs-datastore/src/lib.rs
index 29d203f87..48acba4c8 100644
--- a/pbs-datastore/src/lib.rs
+++ b/pbs-datastore/src/lib.rs
@@ -157,6 +157,13 @@
 
 #![deny(unsafe_op_in_unsafe_fn)]
 
+use std::os::unix::io::AsRawFd;
+use std::path::Path;
+
+use anyhow::{bail, Error};
+
+use pbs_config::BackupLockGuard;
+
 /// Directory path where active operations counters are saved.
 pub const ACTIVE_OPERATIONS_DIR: &str = concat!(
     pbs_buildcfg::PROXMOX_BACKUP_RUN_DIR_M!(),
@@ -237,3 +244,30 @@ pub use local_chunk_reader::LocalChunkReader;
 
 mod local_datastore_lru_cache;
 pub use local_datastore_lru_cache::LocalDatastoreLruCache;
+
+/// Helps implement the double stat'ing procedure. It avoids certain race conditions upon lock
+/// deletion.
+///
+/// It also creates the base directory for lock files.
+pub fn lock_helper<F>(store_name: &str, path: &Path, lock_fn: F) -> Result<BackupLockGuard, Error>
+where
+    F: Fn(&Path) -> Result<BackupLockGuard, Error>,
+{
+    let mut lock_dir = Path::new(DATASTORE_LOCKS_DIR).join(store_name);
+
+    if let Some(parent) = path.parent() {
+        lock_dir = lock_dir.join(parent);
+    };
+
+    std::fs::create_dir_all(&lock_dir)?;
+
+    let lock = lock_fn(path)?;
+
+    let inode = nix::sys::stat::fstat(lock.as_raw_fd())?.st_ino;
+
+    if nix::sys::stat::stat(path).map_or(true, |st| inode != st.st_ino) {
+        bail!("could not acquire lock, another thread modified the lock file");
+    }
+
+    Ok(lock)
+}
-- 
2.47.3