[PATCH] tracing: do not create option file latency-format

[Changbin Du <changbin.du@gmail.com>]

The flag LATENCY_FMT actually is usually set by latency tracers internally.
So I think we should not export it to userspace. This patch removes the
option file 'latency-format' but keep the flag defined as usual.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
 kernel/trace/trace.c | 4 ++++
 kernel/trace/trace.h | 4 +++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 29615f15a820..0d190e0021d5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4733,6 +4733,8 @@ static int tracing_trace_options_show(struct seq_file *m, void *v)
 	trace_opts = tr->current_trace->flags->opts;
 
 	for (i = 0; trace_options[i]; i++) {
+		if (strlen(trace_options[i]) == 0)
+			continue;
 		if (tr->trace_flags & (1 << i))
 			seq_printf(m, "%s\n", trace_options[i]);
 		else
@@ -8359,6 +8361,8 @@ static void create_trace_options_dir(struct trace_array *tr)
 		return;
 
 	for (i = 0; trace_options[i]; i++) {
+		if (strlen(trace_options[i]) == 0)
+			continue;
 		if (top_level ||
 		    !((1 << i) & TOP_LEVEL_TRACE_FLAGS))
 			create_trace_option_core_file(tr, trace_options[i], i);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 4eb1d004d5f2..6d9f0bba09c3 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1264,6 +1264,8 @@ extern void trace_parser_put(struct trace_parser *parser);
 extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 	size_t cnt, loff_t *ppos);
 
+#define TRACE_OPTION_HIDE_NAME	""
+
 /*
  * Only create function graph options if function graph is configured.
  */
@@ -1321,7 +1323,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 		C(SYM_USEROBJ,		"sym-userobj"),		\
 		C(PRINTK_MSGONLY,	"printk-msg-only"),	\
 		C(CONTEXT_INFO,		"context-info"),   /* Print pid/cpu/time */ \
-		C(LATENCY_FMT,		"latency-format"),	\
+		C(LATENCY_FMT,		TRACE_OPTION_HIDE_NAME),\
 		C(RECORD_CMD,		"record-cmd"),		\
 		C(RECORD_TGID,		"record-tgid"),		\
 		C(OVERWRITE,		"overwrite"),		\
-- 
2.25.1