trace-cmd split: Do not allow spliting of latency tracers

trace-cmd split is an operation to make large data records into more
manageable sized files.

But for latency tracers like:

  trace-cmd record wakeup

trace-cmd does not record any binary files, it only records the ASCII
contents of the trace file that is only a snapshot of where the latency
happens (which is usually rather small). trace-cmd split is made for
"flight recording" (constant recording over a period of time) that can
cause the file to become gigabytes in size. Splitting the ASCII text does
not make any sense.

That said, trace-cmd split should not segfault either when trying to split
a latency trace. Instead do what trace-cmd hist does, which is to simply
exit with an error message that says it does not support latency traces.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 15 insertions, 2 deletions

diff --git a/trace-cmd.h b/trace-cmd.h
index 7bce2a56..59194ef4 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -94,6 +94,7 @@ enum {
 enum {
 	TRACECMD_FL_IGNORE_DATE		= (1 << 0),
 	TRACECMD_FL_BUFFER_INSTANCE	= (1 << 1),
+	TRACECMD_FL_LATENCY		= (1 << 2),
 };
 
 struct tracecmd_ftrace {
@@ -116,6 +117,7 @@ int tracecmd_cpus(struct tracecmd_input *handle);
 int tracecmd_copy_headers(struct tracecmd_input *handle, int fd);
 void tracecmd_set_flag(struct tracecmd_input *handle, int flag);
 void tracecmd_clear_flag(struct tracecmd_input *handle, int flag);
+unsigned long tracecmd_get_flags(struct tracecmd_input *handle);
 
 int tracecmd_make_pipe(struct tracecmd_input *handle, int cpu, int fd, int cpus);
 
diff --git a/trace-input.c b/trace-input.c
index 92eba45c..89f4e9e6 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -122,6 +122,11 @@ void tracecmd_clear_flag(struct tracecmd_input *handle, int flag)
 	handle->flags &= ~flag;
 }
 
+unsigned long tracecmd_get_flags(struct tracecmd_input *handle)
+{
+	return handle->flags;
+}
+
 #if DEBUG_RECORD
 static void remove_record(struct page *page, struct pevent_record *record)
 {
@@ -2036,8 +2041,10 @@ static int read_cpu_data(struct tracecmd_input *handle)
 	/*
 	 * Check if this is a latency report or not.
 	 */
-	if (strncmp(buf, "latency", 7) == 0)
+	if (strncmp(buf, "latency", 7) == 0) {
+		handle->flags |= TRACECMD_FL_LATENCY;
 		return 1;
+	}
 
 	/* We expect this to be flyrecord */
 	if (strncmp(buf, "flyrecord", 9) != 0)
@@ -2457,6 +2464,7 @@ struct tracecmd_input *tracecmd_alloc(const char *file)
 struct tracecmd_input *tracecmd_open_fd(int fd)
 {
 	struct tracecmd_input *handle;
+	int ret;
 
 	handle = tracecmd_alloc_fd(fd);
 	if (!handle)
@@ -2465,7 +2473,7 @@ struct tracecmd_input *tracecmd_open_fd(int fd)
 	if (tracecmd_read_headers(handle) < 0)
 		goto fail;
 
-	if (tracecmd_init_data(handle) < 0)
+	if ((ret = tracecmd_init_data(handle)) < 0)
 		goto fail;
 
 	return handle;
diff --git a/trace-split.c b/trace-split.c
index d7d1cb9c..e48c7b11 100644
--- a/trace-split.c
+++ b/trace-split.c
@@ -516,6 +516,9 @@ void trace_split (int argc, char **argv)
 	if (!handle)
 		die("error reading %s", input_file);
 
+	if (tracecmd_get_flags(handle) & TRACECMD_FL_LATENCY)
+		die("trace-cmd split does not work with latency traces\n");
+
 	page_size = tracecmd_page_size(handle);
 
 	if (!output)