slab: Only define slab_error for DEBUG

On Tue, 11 Sep 2012, Stephen Rothwell wrote:
> After merging the final tree, today's linux-next build (sparc64 defconfig)
> produced this warning:
>
> mm/slab.c:808:13: warning: '__slab_error' defined but not used [-Wunused-function]
>
> Introduced by commit 945cf2b6 ("mm/sl[aou]b: Extract a common
> function for kmem_cache_destroy").  All uses of slab_error() are now
> guarded by DEBUG.

There is no use case left for slab builds without DEBUG.
Signed-off-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NPekka Enberg <penberg@kernel.org>

mm/slab.c

@@ -803,6 +803,7 @@ static void cache_estimate(unsigned long gfporder, size_t buffer_size,
 	*left_over = slab_size - nr_objs*buffer_size - mgmt_size;
 }
 
+#if DEBUG
 #define slab_error(cachep, msg) __slab_error(__func__, cachep, msg)
 
 static void __slab_error(const char *function, struct kmem_cache *cachep,
@@ -812,6 +813,7 @@ static void __slab_error(const char *function, struct kmem_cache *cachep,
 	       function, cachep->name, msg);
 	dump_stack();
 }
+#endif
 
 /*
  * By default on NUMA we use alien caches to stage the freeing of