tracing/kprobes: Simplify the logic of enable_trace_kprobe()

The function enable_trace_kprobe() performs slightly differently if the file
parameter is passed in as NULL on non-NULL. Instead of checking file twice,
move the code between the two tests into a static inline helper function to
make the code easier to follow.

Link: http://lkml.kernel.org/r/20180725224728.7b1d5db2@vmware.local.home
Link: http://lkml.kernel.org/r/20180726121152.4dd54330@gandalf.local.home
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 6b71860..0534eb8 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -393,6 +393,20 @@ static struct trace_kprobe *find_trace_kprobe(const char *event,
        return NULL;
 }
 
+static inline int __enable_trace_kprobe(struct trace_kprobe *tk)
+{
+       int ret = 0;
+
+       if (trace_probe_is_registered(&tk->tp) && !trace_kprobe_has_gone(tk)) {
+               if (trace_kprobe_is_return(tk))
+                       ret = enable_kretprobe(&tk->rp);
+               else
+                       ret = enable_kprobe(&tk->rp.kp);
+       }
+
+       return ret;
+}
+
 /*
  * Enable trace_probe
  * if the file is NULL, enable "perf" handler, or enable "trace" handler.
@@ -400,7 +414,7 @@ static struct trace_kprobe *find_trace_kprobe(const char *event,
 static int
 enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
 {
-       struct event_file_link *link = NULL;
+       struct event_file_link *link;
        int ret = 0;
 
        if (file) {
@@ -414,26 +428,18 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
                list_add_tail_rcu(&link->list, &tk->tp.files);
 
                tk->tp.flags |= TP_FLAG_TRACE;
-       } else
-               tk->tp.flags |= TP_FLAG_PROFILE;
-
-       if (trace_probe_is_registered(&tk->tp) && !trace_kprobe_has_gone(tk)) {
-               if (trace_kprobe_is_return(tk))
-                       ret = enable_kretprobe(&tk->rp);
-               else
-                       ret = enable_kprobe(&tk->rp.kp);
-       }
-
-       if (ret) {
-               if (file) {
-                       /* Notice the if is true on not WARN() */
-                       if (!WARN_ON_ONCE(!link))
-                               list_del_rcu(&link->list);
+               ret = __enable_trace_kprobe(tk);
+               if (ret) {
+                       list_del_rcu(&link->list);
                        kfree(link);
                        tk->tp.flags &= ~TP_FLAG_TRACE;
-               } else {
-                       tk->tp.flags &= ~TP_FLAG_PROFILE;
                }
+
+       } else {
+               tk->tp.flags |= TP_FLAG_PROFILE;
+               ret = __enable_trace_kprobe(tk);
+               if (ret)
+                       tk->tp.flags &= ~TP_FLAG_PROFILE;
        }
  out:
        return ret;