mm/memory.c:print_vma_addr(): call up_read(&mm->mmap_sem) directly

Call up_read(&mm->mmap_sem) directly since we have already got mm via
current->mm at the beginning of print_vma_addr().
Signed-off-by: NJie Liu <jeff.liu@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

@@ -3941,7 +3941,7 @@ void print_vma_addr(char *prefix, unsigned long ip)
 			free_page((unsigned long)buf);
 		}
 	}
-	up_read(&current->mm->mmap_sem);
+	up_read(&mm->mmap_sem);
 }
 
 #ifdef CONFIG_PROVE_LOCKING