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/slob.c b/mm/slob.c
index 0000358..a2d4ab3 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -514,6 +514,8 @@
 {
 	struct slob_page *sp;
 
+	trace_kfree(_RET_IP_, block);
+
 	if (unlikely(ZERO_OR_NULL_PTR(block)))
 		return;
 
@@ -524,8 +526,6 @@
 		slob_free(m, *m + align);
 	} else
 		put_page(&sp->page);
-
-	trace_kfree(_RET_IP_, block);
 }
 EXPORT_SYMBOL(kfree);