[PATCH 1/2] tracing/function: fix the return value of ftrace_trace_onoff_callback()

[Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>]

ftrace_trace_onoff_callback() will return error even if we do the
right operation, for example:

# echo _spin_*:traceon:10 > set_ftrace_filter
-bash: echo: write error: Invalid argument
# cat set_ftrace_filter
#### all functions enabled ####
_spin_trylock_bh:traceon:count=10
_spin_unlock_irq:traceon:count=10
_spin_unlock_bh:traceon:count=10
_spin_lock_irq:traceon:count=10
_spin_unlock:traceon:count=10
_spin_trylock:traceon:count=10
_spin_unlock_irqrestore:traceon:count=10
_spin_lock_irqsave:traceon:count=10
_spin_lock_bh:traceon:count=10
_spin_lock:traceon:count=10

We want to set _spin_*:traceon:10 to set_ftrace_filter, it complain
with "Invalid argument", but the operation is successful.
So, this patch fix it.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 kernel/trace/trace_functions.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 7402144..75ef000 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -363,7 +363,7 @@ ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable)
  out_reg:
 	ret = register_ftrace_function_probe(glob, ops, count);
 
-	return ret;
+	return ret < 0 ? ret : 0;
 }
 
 static struct ftrace_func_command ftrace_traceon_cmd = {
-- 
1.6.1.2