tracing/events: simplify system_enable_read()

A smarter way to figure out the output of an enable file.

[ Impact: clean up ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A0399A5.2080603@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 34 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 45f1099386b6..df394bc6d54b 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -414,10 +414,11 @@ static ssize_t
 system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
                    loff_t *ppos)
 {
+        const char set_to_char[4] = { '?', '0', '1', 'X' };
         const char *system = filp->private_data;
         struct ftrace_event_call *call;
         char buf[2];
-        int set = -1;
+        int set = 0;
         int ret;
 
         mutex_lock(&event_mutex);
@@ -433,47 +434,18 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
                  * or if all events or cleared, or if we have
                  * a mixture.
                  */
-                if (call->enabled) {
-                        switch (set) {
-                        case -1:
-                                set = 1;
-                                break;
-                        case 0:
-                                set = 2;
-                                break;
-                        }
-                } else {
-                        switch (set) {
-                        case -1:
-                                set = 0;
-                                break;
-                        case 1:
-                                set = 2;
-                                break;
-                        }
-                }
+                set |= (1 << !!call->enabled);
+
                 /*
                  * If we have a mixture, no need to look further.
                  */
-                if (set == 2)
+                if (set == 3)
                         break;
         }
         mutex_unlock(&event_mutex);
 
+        buf[0] = set_to_char[set];
         buf[1] = '\n';
-        switch (set) {
-        case 0:
-                buf[0] = '0';
-                break;
-        case 1:
-                buf[0] = '1';
-                break;
-        case 2:
-                buf[0] = 'X';
-                break;
-        default:
-                buf[0] = '?';
-        }
 
         ret = simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);