Btrfs: smarter transaction writeback

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 3cc2990..afe42d1 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -9,6 +9,7 @@
 	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;
 };