ftrace: Simplify ftrace_match_record() even more
Dan Carpenter sent a patch to remove a check in ftrace_match_record()
because the logic of the code made the check redundant. I looked deeper into
the code, and made the following logic table, with the three variables and
the result of the original code.
modname mod_matches exclude_mod result
------- ----------- ----------- ------
0 0 0 return 0
0 0 1 func_match
0 1 * < cannot exist >
1 0 0 return 0
1 0 1 func_match
1 1 0 func_match
1 1 1 return 0
Notice that when mod_matches == exclude mod, the result is always to
return 0, and when mod_matches != exclude_mod, then the result is to test
the function. This means we only need test if mod_matches is equal to
exclude_mod.
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 84286d3..39dca4e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3631,22 +3631,20 @@
/* blank module name to match all modules */
if (!mod_g->len) {
/* blank module globbing: modname xor exclude_mod */
- if ((!exclude_mod) != (!modname))
+ if (!exclude_mod != !modname)
goto func_match;
return 0;
}
- /* not matching the module */
- if (!modname || !mod_matches) {
- if (exclude_mod)
- goto func_match;
- else
- return 0;
- }
-
- if (exclude_mod)
+ /*
+ * exclude_mod is set to trace everything but the given
+ * module. If it is set and the module matches, then
+ * return 0. If it is not set, and the module doesn't match
+ * also return 0. Otherwise, check the function to see if
+ * that matches.
+ */
+ if (!mod_matches == !exclude_mod)
return 0;
-
func_match:
/* blank search means to match all funcs in the mod */
if (!func_g->len)