[pbs-devel] [PATCH proxmox-backup v2 12/19] chunk store: implement per-chunk file locking helper for s3 backend

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

Adds chunk store helper methods to create per-chunk file locks. These
will be used to guard chunk operations on s3 backends to guarantee
exclusive access when performing cache and backend operations.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
Changes since version 1:
- drop lock_chunk_for_backend helper, rather inline the locking

 pbs-datastore/src/backup_info.rs |  2 +-
 pbs-datastore/src/chunk_store.rs | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/pbs-datastore/src/backup_info.rs b/pbs-datastore/src/backup_info.rs
index 4b10b6435..70c0fbe8a 100644
--- a/pbs-datastore/src/backup_info.rs
+++ b/pbs-datastore/src/backup_info.rs
@@ -936,7 +936,7 @@ fn lock_file_path_helper(ns: &BackupNamespace, path: PathBuf) -> PathBuf {
 /// deletion.
 ///
 /// It also creates the base directory for lock files.
-fn lock_helper<F>(
+pub(crate) fn lock_helper<F>(
     store_name: &str,
     path: &std::path::Path,
     lock_fn: F,
diff --git a/pbs-datastore/src/chunk_store.rs b/pbs-datastore/src/chunk_store.rs
index ba7618e40..49687b2fa 100644
--- a/pbs-datastore/src/chunk_store.rs
+++ b/pbs-datastore/src/chunk_store.rs
@@ -8,6 +8,7 @@ use anyhow::{bail, format_err, Context, Error};
 use tracing::{info, warn};
 
 use pbs_api_types::{DatastoreFSyncLevel, GarbageCollectionStatus};
+use pbs_config::BackupLockGuard;
 use proxmox_io::ReadExt;
 use proxmox_s3_client::S3Client;
 use proxmox_sys::fs::{create_dir, create_path, file_type_from_file_stat, CreateOptions};
@@ -16,6 +17,7 @@ use proxmox_sys::process_locker::{
 };
 use proxmox_worker_task::WorkerTaskContext;
 
+use crate::backup_info::DATASTORE_LOCKS_DIR;
 use crate::data_blob::DataChunkBuilder;
 use crate::file_formats::{
     COMPRESSED_BLOB_MAGIC_1_0, ENCRYPTED_BLOB_MAGIC_1_0, UNCOMPRESSED_BLOB_MAGIC_1_0,
@@ -759,6 +761,30 @@ impl ChunkStore {
         ChunkStore::check_permissions(lockfile_path, 0o644)?;
         Ok(())
     }
+
+    /// Generates the path to the chunks lock file
+    pub(crate) fn chunk_lock_path(&self, digest: &[u8]) -> PathBuf {
+        let mut lock_path = Path::new(DATASTORE_LOCKS_DIR).join(self.name.clone());
+        let digest_str = hex::encode(digest);
+        lock_path.push(".chunks");
+        let prefix = digest_to_prefix(digest);
+        lock_path.push(&prefix);
+        lock_path.push(&digest_str);
+        lock_path
+    }
+
+    /// Get an exclusive lock on the chunks lock file
+    pub(crate) fn lock_chunk(
+        &self,
+        digest: &[u8],
+        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| {
+            pbs_config::open_backup_lockfile(path, Some(timeout), true)
+        })?;
+        Ok(guard)
+    }
 }
 
 #[test]
-- 
2.47.3



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