seq_file: don't call bitmap_scnprintf_len()

"m->count + len < m->size" is true commonly, so bitmap_scnprintf()
is commonly called. this fix saves a call to bitmap_scnprintf_len().
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/seq_file.c

@@ -452,17 +452,18 @@ int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
 
 int seq_bitmap(struct seq_file *m, unsigned long *bits, unsigned int nr_bits)
 {
-	size_t len = bitmap_scnprintf_len(nr_bits);
-
-	if (m->count + len < m->size) {
-		bitmap_scnprintf(m->buf + m->count, m->size - m->count,
-				 bits, nr_bits);
-		m->count += len;
-		return 0;
+	if (m->count < m->size) {
+		int len = bitmap_scnprintf(m->buf + m->count,
+				m->size - m->count, bits, nr_bits);
+		if (m->count + len < m->size) {
+			m->count += len;
+			return 0;
+		}
 	}
 	m->count = m->size;
 	return -1;
 }
+EXPORT_SYMBOL(seq_bitmap);
 
 static void *single_start(struct seq_file *p, loff_t *pos)
 {