seq_buf: Create seq_buf_used() to find out how much was written

Add a helper function seq_buf_used() that replaces the SEQ_BUF_USED()
private macro to let callers have a method to know how much of the
seq_buf was written to.

Link: http://lkml.kernel.org/r/20141114011412.170377300@goodmis.org
Link: http://lkml.kernel.org/r/20141114011413.321654244@goodmis.orgReviewed-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/seq_buf.h

@@ -64,6 +64,12 @@ seq_buf_buffer_left(struct seq_buf *s)
 	return (s->size - 1) - s->len;
 }
 
+/* How much buffer was written? */
+static inline unsigned int seq_buf_used(struct seq_buf *s)
+{
+	return min(s->len, s->size);
+}
+
 extern __printf(2, 3)
 int seq_buf_printf(struct seq_buf *s, const char *fmt, ...);
 extern __printf(2, 0)

kernel/trace/seq_buf.c

@@ -16,9 +16,6 @@
 #include <linux/seq_file.h>
 #include <linux/seq_buf.h>
 
-/* How much buffer is written? */
-#define SEQ_BUF_USED(s) min((s)->len, (s)->size - 1)
-
 /**
  * seq_buf_print_seq - move the contents of seq_buf into a seq_file
  * @m: the seq_file descriptor that is the destination
@@ -28,7 +25,7 @@
  */
 int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s)
 {
-	unsigned int len = SEQ_BUF_USED(s);
+	unsigned int len = seq_buf_used(s);
 
 	return seq_write(m, s->buffer, len);
 }