mm/mmap.c: remove the first mapping check

Remove the first mapping check for vma_link.  Move the mutex_lock into the
braces when vma->vm_file is true.
Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mmap.c

@@ -640,11 +640,10 @@ static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 {
 	struct address_space *mapping = NULL;
 
-	if (vma->vm_file)
+	if (vma->vm_file) {
 		mapping = vma->vm_file->f_mapping;
-
-	if (mapping)
 		mutex_lock(&mapping->i_mmap_mutex);
+	}
 
 	__vma_link(mm, vma, prev, rb_link, rb_parent);
 	__vma_link_file(vma);