debug_objects: add boot-parameter toggle to turn object debugging off again

While trying to debug why my Atom netbook is falling over booting
rawhide debug-enabled kernels, I stumbled across the fact that we've
been enabling object debugging by default. However, once you default it
to on, you've got no way to turn it back off again at runtime.

Add a boolean toggle to turn it off. I would just make it an int
module_param, however people may already expect the boolean enable
behaviour, so just add an analogue for disabling.

Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/kernel-parameters.txt

@@ -604,6 +604,9 @@ and is between 256 and 4096 characters. It is defined in the file
 
 	debug_objects	[KNL] Enable object debugging
 
+	no_debug_objects
+			[KNL] Disable object debugging
+
 	debugpat	[X86] Enable PAT debugging
 
 	decnet.addr=	[HW,NET]

lib/debugobjects.c

@@ -55,7 +55,15 @@ static int __init enable_object_debug(char *str)
 	debug_objects_enabled = 1;
 	return 0;
 }
+
+static int __init disable_object_debug(char *str)
+{
+	debug_objects_enabled = 0;
+	return 0;
+}
+
 early_param("debug_objects", enable_object_debug);
+early_param("no_debug_objects", disable_object_debug);
 
 static const char *obj_states[ODEBUG_STATE_MAX] = {
 	[ODEBUG_STATE_NONE]		= "none",