Btrfs: write barriers on commit, balance level before split

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 047a847..681b239 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -259,6 +259,7 @@
 	struct list_head trans_list;
 	struct crypto_hash *hash_tfm;
 	spinlock_t hash_lock;
+	int do_barriers;
 	struct kobject kobj;
 };