btrfs: add trace for qgroup accounting

We want this to debug qgroup changes on live systems.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 2ce4ce7..1e4c6e9 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1335,6 +1335,8 @@
 	INIT_LIST_HEAD(&oper->elem.list);
 	oper->elem.seq = 0;
 
+	trace_btrfs_qgroup_record_ref(oper);
+
 	if (type == BTRFS_QGROUP_OPER_SUB_SUBTREE) {
 		/*
 		 * If any operation for this bytenr/ref_root combo
@@ -2077,6 +2079,8 @@
 
 	ASSERT(is_fstree(oper->ref_root));
 
+	trace_btrfs_qgroup_account(oper);
+
 	switch (oper->type) {
 	case BTRFS_QGROUP_OPER_ADD_EXCL:
 	case BTRFS_QGROUP_OPER_SUB_EXCL: