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 84286d347cd8de0d52cae808f9e20f62c0fd7926..39dca4e86a94f0867c29aaa29b47d881eefd02e8 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3631,22 +3631,20 @@ ftrace_match_record(struct dyn_ftrace *rec, struct ftrace_glob *func_g,
                /* 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)