Local refcounting of blocks

src/block.rs

@@ -1,25 +1,38 @@
 use std::path::PathBuf;
-use std::sync::Arc;
 
 use tokio::fs;
 use tokio::prelude::*;
+use tokio::sync::Mutex;
+use futures_util::future::*;
 
 use crate::data::*;
 use crate::error::Error;
 use crate::proto::*;
-use crate::server::Garage;
+use crate::background::*;
 
-fn block_dir(garage: &Garage, hash: &Hash) -> PathBuf {
-	let mut path = garage.system.config.data_dir.clone();
-	path.push(hex::encode(&hash.as_slice()[0..1]));
-	path.push(hex::encode(&hash.as_slice()[1..2]));
-	path
+
+pub struct BlockManager {
+	pub data_dir: PathBuf,
+	pub rc: sled::Tree,
+	pub lock: Mutex<()>,
 }
 
-pub async fn write_block(garage: Arc<Garage>, hash: &Hash, data: &[u8]) -> Result<Message, Error> {
-	garage.fs_lock.lock().await;
+impl BlockManager {
+	pub fn new(db: &sled::Db, data_dir: PathBuf) -> Self {
+		let rc = db.open_tree("block_local_rc")
+			.expect("Unable to open block_local_rc tree");
+		rc.set_merge_operator(rc_merge);
+		Self{
+			rc,
+			data_dir,
+			lock: Mutex::new(()),
+		}
+	}
 
-	let mut path = block_dir(&garage, hash);
+	pub async fn write_block(&self, hash: &Hash, data: &[u8]) -> Result<Message, Error> {
+		let _lock = self.lock.lock().await;
+
+		let mut path = self.block_dir(hash);
 		fs::create_dir_all(&path).await?;
 
 		path.push(hex::encode(hash));
@@ -34,8 +47,8 @@ pub async fn write_block(garage: Arc<Garage>, hash: &Hash, data: &[u8]) -> Resul
 		Ok(Message::Ok)
 	}
 
-pub async fn read_block(garage: Arc<Garage>, hash: &Hash) -> Result<Message, Error> {
-	let mut path = block_dir(&garage, hash);
+	pub async fn read_block(&self, hash: &Hash) -> Result<Message, Error> {
+		let mut path = self.block_dir(hash);
 		path.push(hex::encode(hash));
 
 		let mut f = fs::File::open(path).await?;
@@ -47,3 +60,54 @@ pub async fn read_block(garage: Arc<Garage>, hash: &Hash) -> Result<Message, Err
 			data,
 		}))
 	}
+
+	fn block_dir(&self, hash: &Hash) -> PathBuf {
+		let mut path = self.data_dir.clone();
+		path.push(hex::encode(&hash.as_slice()[0..1]));
+		path.push(hex::encode(&hash.as_slice()[1..2]));
+		path
+	}
+
+	pub fn block_incref(&self, hash: &Hash) -> Result<(), Error> {
+		self.rc.merge(&hash, vec![1])?;
+		Ok(())
+	}
+
+	pub fn block_decref(&self, hash: &Hash, background: &BackgroundRunner) -> Result<(), Error> {
+		match self.rc.merge(&hash, vec![0])? {
+			None => {
+				let mut path = self.block_dir(hash);
+				path.push(hex::encode(hash));
+				background.spawn(tokio::fs::remove_file(path).map_err(Into::into));
+				Ok(())
+			}
+			Some(_) => Ok(())
+		}
+	}
+}
+
+fn rc_merge(_key: &[u8], old: Option<&[u8]>, new: &[u8]) -> Option<Vec<u8>> {
+	let old = old.map(|x| {
+		assert!(x.len() == 8);
+		let mut x8 = [0u8; 8];
+		x8.copy_from_slice(x);
+		u64::from_be_bytes(x8)
+	}).unwrap_or(0);
+	assert!(new.len() == 1);
+	let new = match new[0] {
+		0 => {
+			if old > 0 {
+				old - 1
+			} else {
+				0
+			}
+		}
+		1 => old + 1,
+		_ => unreachable!(),
+	};
+	if new == 0 {
+		None
+	} else {
+		Some(u64::to_be_bytes(new).to_vec())
+	}
+}

src/block_ref_table.rs

@@ -45,7 +45,19 @@ impl TableFormat for BlockRefTable {
 	type E = BlockRef;
 
 	async fn updated(&self, old: Option<Self::E>, new: Self::E) {
-		//unimplemented!()
-		// TODO
+		let garage = self.garage.read().await.as_ref().cloned().unwrap();
+
+		let was_before = old.map(|x| !x.deleted).unwrap_or(false);
+		let is_after = !new.deleted;
+		if is_after && !was_before {
+			if let Err(e) = garage.block_manager.block_incref(&new.block) {
+				eprintln!("Failed to incref block {:?}: {}", &new.block, e);
+			}
+		}
+		if was_before && !is_after {
+			if let Err(e) = garage.block_manager.block_decref(&new.block, &garage.background) {
+				eprintln!("Failed to decref or delete block {:?}: {}", &new.block, e);
+			}
+		}
 	}
 }

src/rpc_server.rs

@@ -9,7 +9,6 @@ use hyper::service::{make_service_fn, service_fn};
 use hyper::{Body, Method, Request, Response, Server, StatusCode};
 use serde::Serialize;
 
-use crate::block::*;
 use crate::data::rmp_to_vec_all_named;
 use crate::error::Error;
 use crate::proto::Message;
@@ -65,8 +64,8 @@ async fn handler(
 		Message::AdvertiseNodesUp(adv) => sys.handle_advertise_nodes_up(adv).await,
 		Message::AdvertiseConfig(adv) => sys.handle_advertise_config(adv).await,
 
-		Message::PutBlock(m) => write_block(garage, &m.hash, &m.data).await,
-		Message::GetBlock(h) => read_block(garage, &h).await,
+		Message::PutBlock(m) => garage.block_manager.write_block(&m.hash, &m.data).await,
+		Message::GetBlock(h) => garage.block_manager.read_block(&h).await,
 
 		Message::TableRPC(table, msg) => {
 			if let Some(rpc_handler) = garage.table_rpc_handlers.get(table) {

src/server.rs

@@ -1,4 +1,4 @@
-use futures_util::future::FutureExt;
+pub use futures_util::future::FutureExt;
 use serde::Deserialize;
 use std::collections::HashMap;
 use std::io::{Read, Write};
@@ -6,11 +6,12 @@ use std::net::SocketAddr;
 use std::path::PathBuf;
 use std::sync::Arc;
 use tokio::sync::watch;
-use tokio::sync::{Mutex, RwLock};
+use tokio::sync::RwLock;
 
 use crate::api_server;
 use crate::background::*;
 use crate::data::*;
+use crate::block::*;
 use crate::error::Error;
 use crate::membership::System;
 use crate::proto::*;
@@ -40,7 +41,7 @@ pub struct Config {
 pub struct Garage {
 	pub db: sled::Db,
 	pub system: Arc<System>,
-	pub fs_lock: Mutex<()>,
+	pub block_manager: BlockManager,
 	pub background: Arc<BackgroundRunner>,
 
 	pub table_rpc_handlers: HashMap<String, Box<dyn TableRpcHandler + Sync + Send>>,
@@ -57,6 +58,8 @@ impl Garage {
 		db: sled::Db,
 		background: Arc<BackgroundRunner>,
 	) -> Arc<Self> {
+		let block_manager = BlockManager::new(&db, config.data_dir.clone());
+
 		let system = Arc::new(System::new(config, id, background.clone()));
 
 		let meta_rep_param = TableReplicationParams {
@@ -105,7 +108,7 @@ impl Garage {
 		let mut garage = Self {
 			db,
 			system: system.clone(),
-			fs_lock: Mutex::new(()),
+			block_manager,
 			background,
 			table_rpc_handlers: HashMap::new(),
 			object_table,