tracing/function: Simplify __ftrace_replace_code()

Rewrite the __ftrace_replace_code() function, simplify it, but don't
change the code's logic.

First, we get the state we want to set, if the record has the same
state, then do nothing, otherwise enable/disable it.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bce9e01..217caec 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1017,71 +1017,35 @@ static int
 __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
 {
        unsigned long ftrace_addr;
-       unsigned long ip, fl;
+       unsigned long flag = 0UL;
 
        ftrace_addr = (unsigned long)FTRACE_ADDR;
 
-       ip = rec->ip;
-
        /*
-        * If this record is not to be traced and
-        * it is not enabled then do nothing.
+        * If this record is not to be traced or we want to disable it,
+        * then disable it.
         *
-        * If this record is not to be traced and
-        * it is enabled then disable it.
+        * If we want to enable it and filtering is off, then enable it.
         *
+        * If we want to enable it and filtering is on, enable it only if
+        * it's filtered
         */
-       if (rec->flags & FTRACE_FL_NOTRACE) {
-               if (rec->flags & FTRACE_FL_ENABLED)
-                       rec->flags &= ~FTRACE_FL_ENABLED;
-               else
-                       return 0;
-
-       } else if (ftrace_filtered && enable) {
-               /*
-                * Filtering is on:
-                */
-
-               fl = rec->flags & (FTRACE_FL_FILTER | FTRACE_FL_ENABLED);
-
-               /* Record is filtered and enabled, do nothing */
-               if (fl == (FTRACE_FL_FILTER | FTRACE_FL_ENABLED))
-                       return 0;
-
-               /* Record is not filtered or enabled, do nothing */
-               if (!fl)
-                       return 0;
-
-               /* Record is not filtered but enabled, disable it */
-               if (fl == FTRACE_FL_ENABLED)
-                       rec->flags &= ~FTRACE_FL_ENABLED;
-               else
-               /* Otherwise record is filtered but not enabled, enable it */
-                       rec->flags |= FTRACE_FL_ENABLED;
-       } else {
-               /* Disable or not filtered */
-
-               if (enable) {
-                       /* if record is enabled, do nothing */
-                       if (rec->flags & FTRACE_FL_ENABLED)
-                               return 0;
-
-                       rec->flags |= FTRACE_FL_ENABLED;
-
-               } else {
+       if (enable && !(rec->flags & FTRACE_FL_NOTRACE)) {
+               if (!ftrace_filtered || (rec->flags & FTRACE_FL_FILTER))
+                       flag = FTRACE_FL_ENABLED;
+       }
 
-                       /* if record is not enabled, do nothing */
-                       if (!(rec->flags & FTRACE_FL_ENABLED))
-                               return 0;
+       /* If the state of this record hasn't changed, then do nothing */
+       if ((rec->flags & FTRACE_FL_ENABLED) == flag)
+               return 0;
 
-                       rec->flags &= ~FTRACE_FL_ENABLED;
-               }
+       if (flag) {
+               rec->flags |= FTRACE_FL_ENABLED;
+               return ftrace_make_call(rec, ftrace_addr);
        }
 
-       if (rec->flags & FTRACE_FL_ENABLED)
-               return ftrace_make_call(rec, ftrace_addr);
-       else
-               return ftrace_make_nop(NULL, rec, ftrace_addr);
+       rec->flags &= ~FTRACE_FL_ENABLED;
+       return ftrace_make_nop(NULL, rec, ftrace_addr);
 }
 
 static void ftrace_replace_code(int enable)