kmemtrace: trace kfree() calls with NULL or zero-length objects

Impact: also output kfree(NULL) entries

This patch moves the trace_kfree() calls before the ZERO_OR_NULL_PTR
check so that we can trace call-sites that call kfree() with NULL many
times which might be an indication of a bug.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
LKML-Reference: <1237971957.30175.18.camel@penberg-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/mm/slab.c b/mm/slab.c
index fa00fd6..b584002 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3773,6 +3773,8 @@
 	struct kmem_cache *c;
 	unsigned long flags;
 
+	trace_kfree(_RET_IP_, objp);
+
 	if (unlikely(ZERO_OR_NULL_PTR(objp)))
 		return;
 	local_irq_save(flags);
@@ -3782,8 +3784,6 @@
 	debug_check_no_obj_freed(objp, obj_size(c));
 	__cache_free(c, (void *)objp);
 	local_irq_restore(flags);
-
-	trace_kfree(_RET_IP_, objp);
 }
 EXPORT_SYMBOL(kfree);