perf cgroup: Fix unmatched call to perf_detach_cgroup()

In the failure path, we call perf_detach_cgroup(), but we didn't
call perf_get_cgroup() prio to it.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4D6F346E.9070606@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_event.c

@@ -412,6 +412,9 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
 	cgrp = container_of(css, struct perf_cgroup, css);
 	event->cgrp = cgrp;
 
+	/* must be done before we fput() the file */
+	perf_get_cgroup(event);
+
 	/*
 	 * all events in a group must monitor
 	 * the same cgroup because a task belongs
@@ -420,9 +423,6 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
 	if (group_leader && group_leader->cgrp != cgrp) {
 		perf_detach_cgroup(event);
 		ret = -EINVAL;
-	} else {
-		/* must be done before we fput() the file */
-		perf_get_cgroup(event);
 	}
 out:
 	fput_light(file, fput_needed);