[pbs-devel] [PATCH proxmox-backup v4 1/4] pbs-config: add token.shadow generation to ConfigVersionCache

[Samuel Rufinatscha]

Prepares the config version cache to support token_shadow caching.

Safety: the shmem mapping is fixed to 4096 bytes via the #[repr(C)]
union padding, and the new atomic is appended to the end of the
#[repr(C)] inner struct, so all existing field offsets stay unchanged.
Old processes keep accessing the same bytes and new processes consume
previously reserved padding.

Signed-off-by: Samuel Rufinatscha <s.rufinatscha at proxmox.com>
---
Changes from v3 to v4:
* Rebased
* Adjusted commit message

Changes from v2 to v3:
* Rebased

Changes from v1 to v2:
* Rebased

 pbs-config/src/config_version_cache.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/pbs-config/src/config_version_cache.rs b/pbs-config/src/config_version_cache.rs
index b875f7e0..399a6f79 100644
--- a/pbs-config/src/config_version_cache.rs
+++ b/pbs-config/src/config_version_cache.rs
@@ -27,6 +27,8 @@ struct ConfigVersionCacheDataInner {
     traffic_control_generation: AtomicUsize,
     // datastore (datastore.cfg) generation/version
     datastore_generation: AtomicUsize,
+    // Token shadow (token.shadow) generation/version.
+    token_shadow_generation: AtomicUsize,
     // Add further atomics here
 }
 
@@ -159,4 +161,20 @@ impl ConfigVersionCache {
             .datastore_generation
             .fetch_add(1, Ordering::AcqRel)
     }
+
+    /// Returns the token shadow generation number.
+    pub fn token_shadow_generation(&self) -> usize {
+        self.shmem
+            .data()
+            .token_shadow_generation
+            .load(Ordering::Acquire)
+    }
+
+    /// Increase the token shadow generation number.
+    pub fn increase_token_shadow_generation(&self) -> usize {
+        self.shmem
+            .data()
+            .token_shadow_generation
+            .fetch_add(1, Ordering::AcqRel)
+    }
 }
-- 
2.47.3