tracing: Keep overwrite in sync between regular and snapshot buffers

commit 80902822658aab18330569587cdb69ac1dfdcea8 upstream.

Changing the overwrite mode for the ring buffer via the trace
option only sets the normal buffer. But the snapshot buffer could
swap with it, and then the snapshot would be in non overwrite mode
and the normal buffer would be in overwrite mode, even though the
option flag states otherwise.

Keep the two buffers overwrite modes in sync.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6751c1158b64d1946a3a8953ac6f2c31c067731a..0c6ce4438d365666ef482d678a45604e38846917 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2650,8 +2650,12 @@ static void set_tracer_flags(unsigned int mask, int enabled)
        if (mask == TRACE_ITER_RECORD_CMD)
                trace_event_enable_cmd_record(enabled);
 
-       if (mask == TRACE_ITER_OVERWRITE)
+       if (mask == TRACE_ITER_OVERWRITE) {
                ring_buffer_change_overwrite(global_trace.buffer, enabled);
+#ifdef CONFIG_TRACER_MAX_TRACE
+               ring_buffer_change_overwrite(max_tr.buffer, enabled);
+#endif
+       }
 }
 
 static ssize_t