tracing: Make the snapshot trigger work with instances

The snapshot trigger currently only affects the main ring buffer, even when
it is used by the instances. This can be confusing as the snapshot trigger
is listed in the instance.

 > # cd /sys/kernel/tracing
 > # mkdir instances/foo
 > # echo snapshot > instances/foo/events/syscalls/sys_enter_fchownat/trigger
 > # echo top buffer > trace_marker
 > # echo foo buffer > instances/foo/trace_marker
 > # touch /tmp/bar
 > # chown rostedt /tmp/bar
 > # cat instances/foo/snapshot
 # tracer: nop
 #
 #
 # * Snapshot is freed *
 #
 # Snapshot commands:
 # echo 0 > snapshot : Clears and frees snapshot buffer
 # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
 #                      Takes a snapshot of the main buffer.
 # echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free)
 #                      (Doesn't have to be '2' works with any number that
 #                       is not a '0' or '1')

 > # cat snapshot
 # tracer: nop
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
             bash-1189  [000] ....   111.488323: tracing_mark_write: top buffer

Not only did the snapshot occur in the top level buffer, but the instance
snapshot buffer should have been allocated, and it is still free.

Cc: stable@vger.kernel.org
Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 414d7210b2ec..bcd93031d042 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -893,7 +893,7 @@ int __trace_bputs(unsigned long ip, const char *str)
 EXPORT_SYMBOL_GPL(__trace_bputs);
 
 #ifdef CONFIG_TRACER_SNAPSHOT
-static void tracing_snapshot_instance(struct trace_array *tr)
+void tracing_snapshot_instance(struct trace_array *tr)
 {
 	struct tracer *tracer = tr->current_trace;
 	unsigned long flags;
@@ -949,7 +949,7 @@ static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
 					struct trace_buffer *size_buf, int cpu_id);
 static void set_buffer_entries(struct trace_buffer *buf, unsigned long val);
 
-static int alloc_snapshot(struct trace_array *tr)
+int tracing_alloc_snapshot_instance(struct trace_array *tr)
 {
 	int ret;
 
@@ -995,7 +995,7 @@ int tracing_alloc_snapshot(void)
 	struct trace_array *tr = &global_trace;
 	int ret;
 
-	ret = alloc_snapshot(tr);
+	ret = tracing_alloc_snapshot_instance(tr);
 	WARN_ON(ret < 0);
 
 	return ret;
@@ -5408,7 +5408,7 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
 
 #ifdef CONFIG_TRACER_MAX_TRACE
 	if (t->use_max_tr && !had_max_tr) {
-		ret = alloc_snapshot(tr);
+		ret = tracing_alloc_snapshot_instance(tr);
 		if (ret < 0)
 			goto out;
 	}
@@ -6451,7 +6451,7 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
 		}
 #endif
 		if (!tr->allocated_snapshot) {
-			ret = alloc_snapshot(tr);
+			ret = tracing_alloc_snapshot_instance(tr);
 			if (ret < 0)
 				break;
 		}
@@ -7179,7 +7179,7 @@ ftrace_trace_snapshot_callback(struct trace_array *tr, struct ftrace_hash *hash,
 		return ret;
 
  out_reg:
-	ret = alloc_snapshot(tr);
+	ret = tracing_alloc_snapshot_instance(tr);
 	if (ret < 0)
 		goto out;