Apply suggestions from code review

Co-authored-by: Bastian Köcher <git@kchr.de>

client/api/src/backend.rs

@@ -516,7 +516,7 @@ pub trait Backend<Block: BlockT>: AuxStore + Send + Sync {
 
 	/// Pin the block to keep bodies, justification and state available after pruning.
 	/// Number of pins are reference counted. Users need to make sure to perform
-	/// one call to `unpin_block` per call to `pin_block`.
+	/// one call to [`Self::unpin_block`] per call to [`Self::pin_block`].
 	fn pin_block(&self, hash: Block::Hash) -> sp_blockchain::Result<()>;
 
 	/// Unpin the block to allow pruning.

client/api/src/client.rs

@@ -268,7 +268,7 @@ impl fmt::Display for UsageInfo {
 #[derive(Debug)]
 pub struct UnpinHandleInner<Block: BlockT> {
 	/// Hash of the block pinned by this handle
-	pub hash: Block::Hash,
+	hash: Block::Hash,
 	unpin_worker_sender: TracingUnboundedSender<Block::Hash>,
 }
 
@@ -285,7 +285,7 @@ impl<Block: BlockT> UnpinHandleInner<Block> {
 impl<Block: BlockT> Drop for UnpinHandleInner<Block> {
 	fn drop(&mut self) {
 		if let Err(err) = self.unpin_worker_sender.unbounded_send(self.hash) {
-			log::error!(target: "db", "Unable to unpin block with hash: {}, error: {:?}", self.hash, err);
+			log::debug!(target: "db", "Unable to unpin block with hash: {}, error: {:?}", self.hash, err);
 		};
 	}
 }

client/db/src/lib.rs

@@ -529,8 +529,7 @@ impl<Block: BlockT> BlockchainDb<Block> {
 
 	/// Empty the cache of pinned items.
 	fn clear_pinning_cache(&self) {
-		let mut cache = self.pinned_blocks_cache.write();
-		cache.clear();
+		self.pinned_blocks_cache.write().clear();
 	}
 
 	/// Load a justification into the cache of pinned items.
@@ -2520,14 +2519,14 @@ impl<Block: BlockT> sc_client_api::backend::Backend<Block> for Backend<Block> {
 			self.storage.state_db.pin(&hash, number.saturated_into::<u64>(), hint).map_err(
 				|_| {
 					sp_blockchain::Error::UnknownBlock(format!(
-						"State already discarded for {:?}",
+						"State already discarded for `{:?}`",
 						hash
 					))
 				},
 			)?;
 		} else {
 			return Err(ClientError::UnknownBlock(format!(
-				"Can not pin block with hash {}. Block not found.",
+				"Can not pin block with hash `{:?}`. Block not found.",
 				hash
 			)))
 		}

client/service/src/client/client.rs

@@ -434,11 +434,11 @@ where
 					if let Some(backend) = task_backend.upgrade() {
 						backend.unpin_block(message);
 					} else {
-						log::warn!("Terminating unpin-worker, backend reference was dropped.");
+						log::debug!("Terminating unpin-worker, backend reference was dropped.");
 						return
 					}
 				}
-				log::warn!("Terminating unpin-worker, stream terminated.")
+				log::debug!("Terminating unpin-worker, stream terminated.")
 			}
 			.boxed(),
 		);