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>

1 files changed, 18 insertions, 54 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bce9e01a29c8..217caeca71cd 100644
--- 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)