tracing: remove max_tracer_type_len

Limit the length of a tracer's name within 100 chars, and then we
don't have to play with max_tracer_type_len.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4AB32377.9020601@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index fd52a19..8613080 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -125,13 +125,13 @@ int ftrace_dump_on_oops;
 
 static int tracing_set_tracer(const char *buf);
 
-#define BOOTUP_TRACER_SIZE             100
-static char bootup_tracer_buf[BOOTUP_TRACER_SIZE] __initdata;
+#define MAX_TRACER_SIZE                100
+static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
 static char *default_bootup_tracer;
 
 static int __init set_ftrace(char *str)
 {
-       strncpy(bootup_tracer_buf, str, BOOTUP_TRACER_SIZE);
+       strncpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
        default_bootup_tracer = bootup_tracer_buf;
        /* We are using ftrace early, expand it */
        ring_buffer_expanded = 1;
@@ -241,13 +241,6 @@ static struct tracer               *trace_types __read_mostly;
 /* current_trace points to the tracer that is currently active */
 static struct tracer           *current_trace __read_mostly;
 
-/*
- * max_tracer_type_len is used to simplify the allocating of
- * buffers to read userspace tracer names. We keep track of
- * the longest tracer name registered.
- */
-static int                     max_tracer_type_len;
-
 /*
  * trace_types_lock is used to protect the trace_types list.
  * This lock is also used to keep user access serialized.
@@ -619,7 +612,6 @@ __releases(kernel_lock)
 __acquires(kernel_lock)
 {
        struct tracer *t;
-       int len;
        int ret = 0;
 
        if (!type->name) {
@@ -627,6 +619,11 @@ __acquires(kernel_lock)
                return -1;
        }
 
+       if (strlen(type->name) > MAX_TRACER_SIZE) {
+               pr_info("Tracer has a name longer than %d\n", MAX_TRACER_SIZE);
+               return -1;
+       }
+
        /*
         * When this gets called we hold the BKL which means that
         * preemption is disabled. Various trace selftests however
@@ -641,7 +638,7 @@ __acquires(kernel_lock)
        for (t = trace_types; t; t = t->next) {
                if (strcmp(type->name, t->name) == 0) {
                        /* already found */
-                       pr_info("Trace %s already registered\n",
+                       pr_info("Tracer %s already registered\n",
                                type->name);
                        ret = -1;
                        goto out;
@@ -692,9 +689,6 @@ __acquires(kernel_lock)
 
        type->next = trace_types;
        trace_types = type;
-       len = strlen(type->name);
-       if (len > max_tracer_type_len)
-               max_tracer_type_len = len;
 
  out:
        tracing_selftest_running = false;
@@ -703,7 +697,7 @@ __acquires(kernel_lock)
        if (ret || !default_bootup_tracer)
                goto out_unlock;
 
-       if (strncmp(default_bootup_tracer, type->name, BOOTUP_TRACER_SIZE))
+       if (strncmp(default_bootup_tracer, type->name, MAX_TRACER_SIZE))
                goto out_unlock;
 
        printk(KERN_INFO "Starting tracer '%s'\n", type->name);
@@ -725,14 +719,13 @@ __acquires(kernel_lock)
 void unregister_tracer(struct tracer *type)
 {
        struct tracer **t;
-       int len;
 
        mutex_lock(&trace_types_lock);
        for (t = &trace_types; *t; t = &(*t)->next) {
                if (*t == type)
                        goto found;
        }
-       pr_info("Trace %s not registered\n", type->name);
+       pr_info("Tracer %s not registered\n", type->name);
        goto out;
 
  found:
@@ -745,17 +738,7 @@ void unregister_tracer(struct tracer *type)
                        current_trace->stop(&global_trace);
                current_trace = &nop_trace;
        }
-
-       if (strlen(type->name) != max_tracer_type_len)
-               goto out;
-
-       max_tracer_type_len = 0;
-       for (t = &trace_types; *t; t = &(*t)->next) {
-               len = strlen((*t)->name);
-               if (len > max_tracer_type_len)
-                       max_tracer_type_len = len;
-       }
- out:
+out:
        mutex_unlock(&trace_types_lock);
 }
 
@@ -2604,7 +2587,7 @@ static ssize_t
 tracing_set_trace_read(struct file *filp, char __user *ubuf,
                       size_t cnt, loff_t *ppos)
 {
-       char buf[max_tracer_type_len+2];
+       char buf[MAX_TRACER_SIZE+2];
        int r;
 
        mutex_lock(&trace_types_lock);
@@ -2754,15 +2737,15 @@ static ssize_t
 tracing_set_trace_write(struct file *filp, const char __user *ubuf,
                        size_t cnt, loff_t *ppos)
 {
-       char buf[max_tracer_type_len+1];
+       char buf[MAX_TRACER_SIZE+1];
        int i;
        size_t ret;
        int err;
 
        ret = cnt;
 
-       if (cnt > max_tracer_type_len)
-               cnt = max_tracer_type_len;
+       if (cnt > MAX_TRACER_SIZE)
+               cnt = MAX_TRACER_SIZE;
 
        if (copy_from_user(&buf, ubuf, cnt))
                return -EFAULT;