From dc213256c0b01cc2de188fffb86a50984db8c624 Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Wed, 1 Oct 2014 22:27:19 +0200
Subject: [PATCH] Optimize extfs syncing blocks.

---
 ext/block.cpp  | 17 ++++++++++++++++-
 ext/block.h    |  2 ++
 ext/device.cpp |  6 ++++--
 ext/device.h   |  1 +
 4 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/ext/block.cpp b/ext/block.cpp
index 10f6abce..8299e232 100644
--- a/ext/block.cpp
+++ b/ext/block.cpp
@@ -35,6 +35,8 @@ Block::Block(Device* device, uint32_t block_id)
 	this->next_block = NULL;
 	this->prev_hashed = NULL;
 	this->next_hashed = NULL;
+	this->prev_dirty = NULL;
+	this->next_dirty = NULL;
 	this->device = device;
 	this->reference_count = 1;
 	this->block_id = block_id;
@@ -69,6 +71,11 @@ void Block::Sync()
 	if ( !dirty )
 		return;
 	dirty = false;
+	(prev_dirty ? prev_dirty->next_dirty : device->dirty_block) = next_dirty;
+	if ( next_dirty )
+		next_dirty->prev_dirty = prev_dirty;
+	prev_dirty = NULL;
+	next_dirty = NULL;
 	if ( !device->write )
 		return;
 	off_t file_offset = (off_t) device->block_size * (off_t) block_id;
@@ -77,7 +84,15 @@ void Block::Sync()
 
 void Block::Dirty()
 {
-	dirty = true;
+	if ( !dirty )
+	{
+		dirty = true;
+		prev_dirty = NULL;
+		next_dirty = device->dirty_block;
+		if ( next_dirty )
+			next_dirty->prev_dirty = this;
+		device->dirty_block = this;
+	}
 	Use();
 }
 
diff --git a/ext/block.h b/ext/block.h
index 94cec14f..6a3f68f4 100644
--- a/ext/block.h
+++ b/ext/block.h
@@ -36,6 +36,8 @@ public:
 	Block* next_block;
 	Block* prev_hashed;
 	Block* next_hashed;
+	Block* prev_dirty;
+	Block* next_dirty;
 	Device* device;
 	size_t reference_count;
 	uint32_t block_id;
diff --git a/ext/device.cpp b/ext/device.cpp
index 13d742fe..4c7a38ab 100644
--- a/ext/device.cpp
+++ b/ext/device.cpp
@@ -23,6 +23,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 
+#include <assert.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
@@ -41,6 +42,7 @@ Device::Device(int fd, uint32_t block_size, bool write)
 	this->device_size = st.st_size;
 	this->mru_block = NULL;
 	this->lru_block = NULL;
+	this->dirty_block = NULL;
 	for ( size_t i = 0; i < DEVICE_HASH_LENGTH; i++ )
 		hash_blocks[i] = NULL;
 }
@@ -91,6 +93,6 @@ Block* Device::GetCachedBlock(uint32_t block_id)
 
 void Device::Sync()
 {
-	for ( Block* iter = mru_block; iter; iter = iter->next_block )
-		iter->Sync();
+	while ( dirty_block )
+		dirty_block->Sync();
 }
diff --git a/ext/device.h b/ext/device.h
index 9a33e5eb..b736f408 100644
--- a/ext/device.h
+++ b/ext/device.h
@@ -36,6 +36,7 @@ public:
 public:
 	Block* mru_block;
 	Block* lru_block;
+	Block* dirty_block;
 	Block* hash_blocks[DEVICE_HASH_LENGTH];
 	off_t device_size;
 	uint32_t block_size;