markers: simplify marker_set_format()

current marker_set_format() is complex this patch simplify it,
and decrease the overhead of marker_update_probes().

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/marker.c

@@ -64,6 +64,7 @@ struct marker_entry {
 	void *oldptr;
 	int rcu_pending;
 	unsigned char ptype:1;
+	unsigned char format_allocated:1;
 	char name[0];	/* Contains name'\0'format'\0' */
 };
 
@@ -416,6 +417,7 @@ static struct marker_entry *add_marker(const char *name, const char *format)
 	e->single.probe_private = NULL;
 	e->multi = NULL;
 	e->ptype = 0;
+	e->format_allocated = 0;
 	e->refcount = 0;
 	e->rcu_pending = 0;
 	hlist_add_head(&e->hlist, head);
@@ -447,6 +449,8 @@ static int remove_marker(const char *name)
 	if (e->single.func != __mark_empty_function)
 		return -EBUSY;
 	hlist_del(&e->hlist);
+	if (e->format_allocated)
+		kfree(e->format);
 	/* Make sure the call_rcu has been executed */
 	if (e->rcu_pending)
 		rcu_barrier_sched();
@@ -457,57 +461,34 @@ static int remove_marker(const char *name)
 /*
  * Set the mark_entry format to the format found in the element.
  */
-static int marker_set_format(struct marker_entry **entry, const char *format)
+static int marker_set_format(struct marker_entry *entry, const char *format)
 {
-	struct marker_entry *e;
-	size_t name_len = strlen((*entry)->name) + 1;
-	size_t format_len = strlen(format) + 1;
-
-
-	e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
-			GFP_KERNEL);
-	if (!e)
+	entry->format = kstrdup(format, GFP_KERNEL);
+	if (!entry->format)
 		return -ENOMEM;
-	memcpy(&e->name[0], (*entry)->name, name_len);
-	e->format = &e->name[name_len];
-	memcpy(e->format, format, format_len);
-	if (strcmp(e->format, MARK_NOARGS) == 0)
-		e->call = marker_probe_cb_noarg;
-	else
-		e->call = marker_probe_cb;
-	e->single = (*entry)->single;
-	e->multi = (*entry)->multi;
-	e->ptype = (*entry)->ptype;
-	e->refcount = (*entry)->refcount;
-	e->rcu_pending = 0;
-	hlist_add_before(&e->hlist, &(*entry)->hlist);
-	hlist_del(&(*entry)->hlist);
-	/* Make sure the call_rcu has been executed */
-	if ((*entry)->rcu_pending)
-		rcu_barrier_sched();
-	kfree(*entry);
-	*entry = e;
+	entry->format_allocated = 1;
+
 	trace_mark(core_marker_format, "name %s format %s",
-			e->name, e->format);
+			entry->name, entry->format);
 	return 0;
 }
 
 /*
  * Sets the probe callback corresponding to one marker.
  */
-static int set_marker(struct marker_entry **entry, struct marker *elem,
+static int set_marker(struct marker_entry *entry, struct marker *elem,
 		int active)
 {
 	int ret;
-	WARN_ON(strcmp((*entry)->name, elem->name) != 0);
+	WARN_ON(strcmp(entry->name, elem->name) != 0);
 
-	if ((*entry)->format) {
-		if (strcmp((*entry)->format, elem->format) != 0) {
+	if (entry->format) {
+		if (strcmp(entry->format, elem->format) != 0) {
 			printk(KERN_NOTICE
 				"Format mismatch for probe %s "
 				"(%s), marker (%s)\n",
-				(*entry)->name,
-				(*entry)->format,
+				entry->name,
+				entry->format,
 				elem->format);
 			return -EPERM;
 		}
@@ -523,34 +504,33 @@ static int set_marker(struct marker_entry **entry, struct marker *elem,
 	 * pass from a "safe" callback (with argument) to an "unsafe"
 	 * callback (does not set arguments).
 	 */
-	elem->call = (*entry)->call;
+	elem->call = entry->call;
 	/*
 	 * Sanity check :
 	 * We only update the single probe private data when the ptr is
 	 * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
 	 */
 	WARN_ON(elem->single.func != __mark_empty_function
-		&& elem->single.probe_private
-		!= (*entry)->single.probe_private &&
-		!elem->ptype);
-	elem->single.probe_private = (*entry)->single.probe_private;
+		&& elem->single.probe_private != entry->single.probe_private
+		&& !elem->ptype);
+	elem->single.probe_private = entry->single.probe_private;
 	/*
 	 * Make sure the private data is valid when we update the
 	 * single probe ptr.
 	 */
 	smp_wmb();
-	elem->single.func = (*entry)->single.func;
+	elem->single.func = entry->single.func;
 	/*
 	 * We also make sure that the new probe callbacks array is consistent
 	 * before setting a pointer to it.
 	 */
-	rcu_assign_pointer(elem->multi, (*entry)->multi);
+	rcu_assign_pointer(elem->multi, entry->multi);
 	/*
 	 * Update the function or multi probe array pointer before setting the
 	 * ptype.
 	 */
 	smp_wmb();
-	elem->ptype = (*entry)->ptype;
+	elem->ptype = entry->ptype;
 	elem->state = active;
 
 	return 0;
@@ -594,8 +574,7 @@ void marker_update_probe_range(struct marker *begin,
 	for (iter = begin; iter < end; iter++) {
 		mark_entry = get_marker(iter->name);
 		if (mark_entry) {
-			set_marker(&mark_entry, iter,
-					!!mark_entry->refcount);
+			set_marker(mark_entry, iter, !!mark_entry->refcount);
 			/*
 			 * ignore error, continue
 			 */
@@ -657,7 +636,7 @@ int marker_probe_register(const char *name, const char *format,
 			ret = PTR_ERR(entry);
 	} else if (format) {
 		if (!entry->format)
-			ret = marker_set_format(&entry, format);
+			ret = marker_set_format(entry, format);
 		else if (strcmp(entry->format, format))
 			ret = -EPERM;
 	}