Revert "tracing: Move event storage for array from macro to standalone function"

I originally wrote commit 35bb4399bd to shrink the size of the overhead of
tracepoints by several kilobytes. Later, I received a patch from Vaibhav
Nagarnaik that fixed a bug in the same code that this commit touches. Not
only did it fix a bug, it also removed code and shrunk the size of the
overhead of trace events even more than this commit did.

Since this commit is scheduled for 3.15 and Vaibhav's patch is already in
mainline, I need to revert this patch in order to keep it from conflicting
with Vaibhav's patch. Not to mention, Vaibhav's patch makes this patch
obsolete.

Link: http://lkml.kernel.org/r/20140320225637.0226041b@gandalf.local.home

Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

@@ -221,6 +221,10 @@ void *ftrace_event_buffer_reserve(struct ftrace_event_buffer *fbuffer,
 
 void ftrace_event_buffer_commit(struct ftrace_event_buffer *fbuffer);
 
+int ftrace_event_define_field(struct ftrace_event_call *call,
+			      char *type, int len, char *item, int offset,
+			      int field_size, int sign, int filter);
+
 enum {
 	TRACE_EVENT_FL_FILTERED_BIT,
 	TRACE_EVENT_FL_CAP_ANY_BIT,
@@ -519,6 +523,10 @@ enum {
 	FILTER_TRACE_FN,
 };
 
+#define EVENT_STORAGE_SIZE 128
+extern struct mutex event_storage_mutex;
+extern char event_storage[EVENT_STORAGE_SIZE];
+
 extern int trace_event_raw_init(struct ftrace_event_call *call);
 extern int trace_define_field(struct ftrace_event_call *call, const char *type,
 			      const char *name, int offset, int size,

include/trace/ftrace.h

@@ -302,11 +302,15 @@ static struct trace_event_functions ftrace_event_type_funcs_##call = {	\
 #undef __array
 #define __array(type, item, len)					\
 	do {								\
+		mutex_lock(&event_storage_mutex);			\
 		BUILD_BUG_ON(len > MAX_FILTER_STR_VAL);			\
-		ret = ftrace_event_define_field(event_call, #type, len,	\
-				#item, offsetof(typeof(field), item),   \
-				sizeof(field.item),			\
-			 	is_signed_type(type), FILTER_OTHER); \
+		snprintf(event_storage, sizeof(event_storage),		\
+			 "%s[%d]", #type, len);				\
+		ret = trace_define_field(event_call, event_storage, #item, \
+				 offsetof(typeof(field), item),		\
+				 sizeof(field.item),			\
+				 is_signed_type(type), FILTER_OTHER);	\
+		mutex_unlock(&event_storage_mutex);			\
 		if (ret)						\
 			return ret;					\
 	} while (0);

kernel/trace/trace_events.c

@@ -27,6 +27,12 @@
 
 DEFINE_MUTEX(event_mutex);
 
+DEFINE_MUTEX(event_storage_mutex);
+EXPORT_SYMBOL_GPL(event_storage_mutex);
+
+char event_storage[EVENT_STORAGE_SIZE];
+EXPORT_SYMBOL_GPL(event_storage);
+
 LIST_HEAD(ftrace_events);
 static LIST_HEAD(ftrace_common_fields);
 

kernel/trace/trace_export.c

@@ -96,10 +96,14 @@ static void __always_unused ____ftrace_check_##name(void)		\
 #define __array(type, item, len)					\
 	do {								\
 		BUILD_BUG_ON(len > MAX_FILTER_STR_VAL);			\
-		ret = ftrace_event_define_field(event_call, #type, len,	\
-				#item, offsetof(typeof(field), item),   \
-				sizeof(field.item),			\
-			 	is_signed_type(type), filter_type);	\
+		mutex_lock(&event_storage_mutex);			\
+		snprintf(event_storage, sizeof(event_storage),		\
+			 "%s[%d]", #type, len);				\
+		ret = trace_define_field(event_call, event_storage, #item, \
+				 offsetof(typeof(field), item),		\
+				 sizeof(field.item),			\
+				 is_signed_type(type), filter_type);	\
+		mutex_unlock(&event_storage_mutex);			\
 		if (ret)						\
 			return ret;					\
 	} while (0);

kernel/trace/trace_output.c

@@ -20,10 +20,6 @@ static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;
 
 static int next_event_type = __TRACE_LAST_TYPE + 1;
 
-#define EVENT_STORAGE_SIZE 128
-static DEFINE_MUTEX(event_storage_mutex);
-static char event_storage[EVENT_STORAGE_SIZE];
-
 int trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
 	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
@@ -474,23 +470,6 @@ int ftrace_output_call(struct trace_iterator *iter, char *name, char *fmt, ...)
 }
 EXPORT_SYMBOL_GPL(ftrace_output_call);
 
-int ftrace_event_define_field(struct ftrace_event_call *call,
-			      char *type, int len, char *item, int offset,
-			      int field_size, int sign, int filter)
-{
-	int ret;
-
-	mutex_lock(&event_storage_mutex);
-	snprintf(event_storage, sizeof(event_storage),
-		 "%s[%d]", type, len);
-	ret = trace_define_field(call, event_storage, item, offset,
-				 field_size, sign, filter);
-	mutex_unlock(&event_storage_mutex);
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(ftrace_event_define_field);
-
 #ifdef CONFIG_KRETPROBES
 static inline const char *kretprobed(const char *name)
 {