fix: kvcache evict workflow

src/cluster/meta_store.rs

@@ -116,6 +116,21 @@ impl MetaStore {
         scores
     }
 
+    /// Remove `instance`'s entry for `block_hash` (e.g. after L1 eviction).
+    ///
+    /// The meta-store must reflect **L1 (DRAM) presence only**, because remote
+    /// RDMA fetch can only reach CPU DRAM, never GPU HBM.  Whenever the L1
+    /// tier evicts a block, the caller must invoke this so the meta-store
+    /// stops advertising the block as remotely available on this instance.
+    pub fn remove(&mut self, block_hash: u64, instance: InstanceId) {
+        if let Some(bucket) = self.map.get_mut(&block_hash) {
+            bucket.retain(|e| e.instance != instance);
+            if bucket.is_empty() {
+                self.map.remove(&block_hash);
+            }
+        }
+    }
+
     /// Lookup which (alive) instances claim to hold a given block.
     pub fn instances_for(&self, hash: u64, now: f64) -> SmallVec<[InstanceId; 4]> {
         let mut out = SmallVec::new();
@@ -149,6 +164,34 @@ mod tests {
         assert_eq!(s[2], 0);
     }
 
+    #[test]
+    fn remove_cleans_up() {
+        let mut m = MetaStore::new(60.0);
+        m.insert(10, 0, 0.0);
+        m.insert(10, 1, 0.0);
+        m.insert(11, 0, 0.0);
+
+        // instance 0 has both blocks, instance 1 has block 10 only
+        let owners = m.instances_for(10, 0.5);
+        assert_eq!(owners.len(), 2);
+
+        // Remove instance 0's entry for block 10
+        m.remove(10, 0);
+        let owners = m.instances_for(10, 0.5);
+        assert_eq!(owners.len(), 1);
+        assert_eq!(owners[0], 1);
+
+        // Instance 0 still owns block 11
+        let owners = m.instances_for(11, 0.5);
+        assert_eq!(owners.len(), 1);
+        assert_eq!(owners[0], 0);
+
+        // Remove last owner of a block -> entry fully cleaned
+        m.remove(10, 1);
+        let owners = m.instances_for(10, 0.5);
+        assert!(owners.is_empty());
+    }
+
     #[test]
     fn ttl_expiry() {
         let mut m = MetaStore::new(1.0);