feat:propagates err in beatree offloaded sync work

nomt/src/beatree/mod.rs

@@ -230,7 +230,7 @@ impl Tree {
         sync: &Sync,
         shared: &Arc<RwLock<Shared>>,
         read_transaction_counter: &ReadTransactionCounter,
-    ) -> (SyncData, Index, Receiver<()>) {
+    ) -> (SyncData, Index, Receiver<std::io::Result<()>>) {
         // Take the shared lock. Briefly.
         let staged_changeset;
         let bbn_index;
@@ -426,7 +426,7 @@ struct SharedSyncController {
     read_transaction_counter: ReadTransactionCounter,
     sync_data: Mutex<Option<SyncData>>,
     bbn_index: Mutex<Option<Index>>,
-    pre_swap_rx: Mutex<Option<Receiver<()>>>,
+    pre_swap_rx: Mutex<Option<Receiver<std::io::Result<()>>>>,
 }
 
 impl SyncController {
@@ -496,15 +496,16 @@ impl SyncController {
     ///
     /// Has to be called after the manifest is updated. Must be invoked by the sync
     /// thread. Blocking.
-    pub fn post_meta(&mut self) {
+    pub fn post_meta(&mut self) -> std::io::Result<()> {
         let pre_swap_rx = self.inner.pre_swap_rx.lock().take().unwrap();
 
-        // UNWRAP: the offloaded non-critical sync work is infallible and may fail only if it
-        // panics.
-        let () = pre_swap_rx.recv().unwrap();
+        // UNWRAP: the offloaded non-critical sync work is infallible
+        // and may fail only if it panics.
+        pre_swap_rx.recv().unwrap()?;
 
         let bbn_index = self.inner.bbn_index.lock().take().unwrap();
         Tree::finish_sync(&self.inner.shared, bbn_index);
+        Ok(())
     }
 }
 

nomt/src/beatree/ops/update/mod.rs

@@ -54,7 +54,7 @@ pub fn update(
     io_handle: IoHandle,
     thread_pool: ThreadPool,
     workers: usize,
-) -> Result<(SyncData, Index, Receiver<()>)> {
+) -> Result<(SyncData, Index, Receiver<std::io::Result<()>>)> {
     let leaf_reader = StoreReader::new(leaf_store.clone(), page_pool.clone());
     let (leaf_writer, leaf_finisher) = leaf_store.start_sync();
     let (bbn_writer, bbn_finisher) = bbn_store.start_sync();
@@ -99,10 +99,18 @@ pub fn update(
 
     let (tx, rx) = crossbeam_channel::bounded(1);
     thread_pool.execute(move || {
-        leaf_stage_outputs.post_io_work.run(&leaf_cache);
-        drop(branch_stage_outputs.post_io_drop);
-        leaf_cache.evict();
-        let _ = tx.send(());
+        let output_or_panic = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
+            leaf_stage_outputs.post_io_work.run(&leaf_cache);
+            drop(branch_stage_outputs.post_io_drop);
+            leaf_cache.evict();
+        }))
+        .map_err(|e| {
+            std::io::Error::new(
+                std::io::ErrorKind::Other,
+                anyhow::anyhow!("panic in beatree offloaded non-critical sync work: {:?}", e),
+            )
+        });
+        let _ = tx.send(output_or_panic);
     });
 
     Ok((

nomt/src/store/sync.rs

@@ -86,7 +86,7 @@ impl Sync {
         }
 
         bitbox_sync.post_meta(shared.io_pool.make_handle())?;
-        beatree_sync.post_meta();
+        beatree_sync.post_meta()?;
 
         if let Some(ref rollback) = rollback_sync {
             rollback.wait_post_meta()?;