Btrfs: smarter transaction writeback

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent-tree.c

@@ -762,6 +762,7 @@ struct buffer_head *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 	BUG_ON(ret);
 	buf = btrfs_find_create_tree_block(root, ins.objectid);
 	set_buffer_uptodate(buf);
+	set_radix_bit(&trans->transaction->dirty_pages, buf->b_page->index);
 	return buf;
 }
 

fs/btrfs/super.c

@@ -980,7 +980,6 @@ static int btrfs_sync_fs(struct super_block *sb, int wait)
 		filemap_flush(root->fs_info->btree_inode->i_mapping);
 		return 0;
 	}
-	filemap_write_and_wait(root->fs_info->btree_inode->i_mapping);
 	mutex_lock(&root->fs_info->fs_mutex);
 	trans = btrfs_start_transaction(root, 1);
 	ret = btrfs_commit_transaction(trans, root);

fs/btrfs/transaction.c

@@ -45,6 +45,7 @@ static int join_transaction(struct btrfs_root *root)
 		cur_trans->use_count = 1;
 		cur_trans->commit_done = 0;
 		list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
+		init_bit_radix(&cur_trans->dirty_pages);
 	}
 	cur_trans->num_writers++;
 	return 0;
@@ -106,8 +107,40 @@ int btrfs_end_transaction(struct btrfs_trans_handle *trans,
 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
 				     struct btrfs_root *root)
 {
-	filemap_write_and_wait(root->fs_info->btree_inode->i_mapping);
+	unsigned long gang[16];
-	return 0;
+	int ret;
+	int i;
+	int err;
+	int werr = 0;
+	struct page *page;
+	struct radix_tree_root *dirty_pages;
+	struct inode *btree_inode = root->fs_info->btree_inode;
+
+	if (!trans || !trans->transaction) {
+		return filemap_write_and_wait(btree_inode->i_mapping);
+	}
+	dirty_pages = &trans->transaction->dirty_pages;
+	while(1) {
+		ret = find_first_radix_bit(dirty_pages, gang, ARRAY_SIZE(gang));
+		if (!ret)
+			break;
+		for (i = 0; i < ret; i++) {
+			/* FIXME EIO */
+			clear_radix_bit(dirty_pages, gang[i]);
+			page = find_lock_page(btree_inode->i_mapping,
+					      gang[i]);
+			if (!page)
+				continue;
+			err = write_one_page(page, 0);
+			if (err)
+				werr = err;
+			page_cache_release(page);
+		}
+	}
+	err = filemap_fdatawait(btree_inode->i_mapping);
+	if (err)
+		werr = err;
+	return werr;
 }
 
 int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,

fs/btrfs/transaction.h

@@ -9,6 +9,7 @@ struct btrfs_transaction {
 	int commit_done;
 	int magic;
 	struct list_head list;
+	struct radix_tree_root dirty_pages;
 	wait_queue_head_t writer_wait;
 	wait_queue_head_t commit_wait;
 };