Common [01/16] slub: Add debugging to verify correct cache use on kmem_cache_free()

[Christoph Lameter <cl@linux.com>]

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Add additional debugging to check that the objects is actually from the cache
the caller claims. Doing so currently trips up some other debugging code. It
takes a lot to infer from that what was happening.

Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2012-07-31 11:46:01.544493395 -0500
+++ linux-2.6/mm/slub.c	2012-07-31 11:53:21.832078581 -0500
@@ -2583,6 +2583,13 @@
 
 	page = virt_to_head_page(x);
 
+	if (kmem_cache_debug(s) && page->slab != s) {
+		printk("kmem_cache_free: Wrong slab cache. %s but object"
+			" is from  %s\n", page->slab->name, s->name);
+		WARN_ON(1);
+		return;
+	}
+
 	slab_free(s, page, x, _RET_IP_);
 
 	trace_kmem_cache_free(_RET_IP_, x);

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