Common11r [01/20] slub: Add debugging to verify correct cache use on kmem_cache_free()

From: Christoph Lameter <cl@linux.com>
To: Joonsoo Kim <js1304@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>,
	Pekka Enberg <penberg@kernel.org>,
	linux-mm@kvack.org, David Rientjes <rientjes@google.com>
Subject: Common11r [01/20] slub: Add debugging to verify correct cache use on kmem_cache_free()
Date: Thu, 09 Aug 2012 08:56:24 -0500	[thread overview]
Message-ID: <20120809135633.629317723@linux.com> (raw)
In-Reply-To: 20120809135623.574621297@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.

V2: Only warn once. 

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

Index: linux-2.6/mm/slub.c
===================================================================

--- linux-2.6.orig/mm/slub.c	2012-08-03 14:16:27.396663869 -0500
+++ linux-2.6/mm/slub.c	2012-08-03 14:16:38.664866880 -0500
@@ -2607,6 +2607,13 @@ void kmem_cache_free(struct kmem_cache *
 
 	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_ONCE(1);
+		return;
+	}
+
 	slab_free(s, page, x, _RET_IP_);
 
 	trace_kmem_cache_free(_RET_IP_, x);

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