ring-buffer: make moving the tail page a separate function

Ingo Molnar thought the code would be cleaner if we used a function call
instead of a goto for moving the tail page. After implementing this,
it seems that gcc still inlines the result and the output is pretty much
the same. Since this is considered a cleaner approach, might as well
implement it.

[ Impact: code clean up ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/ring_buffer.c

@@ -1154,51 +1154,18 @@ static unsigned rb_calculate_event_length(unsigned length)
 	return length;
 }
 
+
 static struct ring_buffer_event *
-__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
-		  unsigned type, unsigned long length, u64 *ts)
+rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
+	     unsigned long length, unsigned long tail,
+	     struct buffer_page *commit_page,
+	     struct buffer_page *tail_page, u64 *ts)
 {
-	struct buffer_page *tail_page, *head_page, *reader_page, *commit_page;
-	struct buffer_page *next_page;
-	unsigned long tail, write;
+	struct buffer_page *next_page, *head_page, *reader_page;
 	struct ring_buffer *buffer = cpu_buffer->buffer;
 	struct ring_buffer_event *event;
-	unsigned long flags;
 	bool lock_taken = false;
-
-	commit_page = cpu_buffer->commit_page;
-	/* we just need to protect against interrupts */
-	barrier();
-	tail_page = cpu_buffer->tail_page;
-	write = local_add_return(length, &tail_page->write);
-	tail = write - length;
-
-	/* See if we shot pass the end of this buffer page */
-	if (write > BUF_PAGE_SIZE)
-		goto next_page;
-
-	/* We reserved something on the buffer */
-
-	if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
-		return NULL;
-
-	event = __rb_page_index(tail_page, tail);
-	rb_update_event(event, type, length);
-
-	/* The passed in type is zero for DATA */
-	if (likely(!type))
-		local_inc(&tail_page->entries);
-
-	/*
-	 * If this is a commit and the tail is zero, then update
-	 * this page's time stamp.
-	 */
-	if (!tail && rb_is_commit(cpu_buffer, event))
-		cpu_buffer->commit_page->page->time_stamp = *ts;
-
-	return event;
-
- next_page:
+	unsigned long flags;
 
 	next_page = tail_page;
 
@@ -1318,6 +1285,48 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 	return NULL;
 }
 
+static struct ring_buffer_event *
+__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
+		  unsigned type, unsigned long length, u64 *ts)
+{
+	struct buffer_page *tail_page, *commit_page;
+	struct ring_buffer_event *event;
+	unsigned long tail, write;
+
+	commit_page = cpu_buffer->commit_page;
+	/* we just need to protect against interrupts */
+	barrier();
+	tail_page = cpu_buffer->tail_page;
+	write = local_add_return(length, &tail_page->write);
+	tail = write - length;
+
+	/* See if we shot pass the end of this buffer page */
+	if (write > BUF_PAGE_SIZE)
+		return rb_move_tail(cpu_buffer, length, tail,
+				    commit_page, tail_page, ts);
+
+	/* We reserved something on the buffer */
+
+	if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
+		return NULL;
+
+	event = __rb_page_index(tail_page, tail);
+	rb_update_event(event, type, length);
+
+	/* The passed in type is zero for DATA */
+	if (likely(!type))
+		local_inc(&tail_page->entries);
+
+	/*
+	 * If this is a commit and the tail is zero, then update
+	 * this page's time stamp.
+	 */
+	if (!tail && rb_is_commit(cpu_buffer, event))
+		cpu_buffer->commit_page->page->time_stamp = *ts;
+
+	return event;
+}
+
 static int
 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
 		  u64 *ts, u64 *delta)