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>

mm/slab.c

@@ -3773,6 +3773,8 @@ void kfree(const void *objp)
 	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 @@ void kfree(const void *objp)
 	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);
 

mm/slob.c

@@ -514,6 +514,8 @@ void kfree(const void *block)
 {
 	struct slob_page *sp;
 
+	trace_kfree(_RET_IP_, block);
+
 	if (unlikely(ZERO_OR_NULL_PTR(block)))
 		return;
 
@@ -524,8 +526,6 @@ void kfree(const void *block)
 		slob_free(m, *m + align);
 	} else
 		put_page(&sp->page);
-
-	trace_kfree(_RET_IP_, block);
 }
 EXPORT_SYMBOL(kfree);
 

mm/slub.c

@@ -2792,6 +2792,8 @@ void kfree(const void *x)
 	struct page *page;
 	void *object = (void *)x;
 
+	trace_kfree(_RET_IP_, x);
+
 	if (unlikely(ZERO_OR_NULL_PTR(x)))
 		return;
 
@@ -2802,8 +2804,6 @@ void kfree(const void *x)
 		return;
 	}
 	slab_free(page->slab, page, object, _RET_IP_);
-
-	trace_kfree(_RET_IP_, x);
 }
 EXPORT_SYMBOL(kfree);