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>

1 files changed, 9 insertions, 11 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 84286d347cd8..39dca4e86a94 100644
--- 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)