kmemleak: Show the age of an unreferenced object

The jiffies shown for unreferenced objects isn't always meaningful to
people debugging kernel memory leaks. This patch adds the age as well to
the displayed information.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index f06c092..ce79d91 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -346,11 +346,13 @@
 			       struct kmemleak_object *object)
 {
 	int i;
+	unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
 
 	seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
 		   object->pointer, object->size);
-	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
-		   object->comm, object->pid, object->jiffies);
+	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
+		   object->comm, object->pid, object->jiffies,
+		   msecs_age / 1000, msecs_age % 1000);
 	hex_dump_object(seq, object);
 	seq_printf(seq, "  backtrace:\n");