1 files changed, 138 insertions, 226 deletions

diff --git a/mm/slab.c b/mm/slab.c
index a467b308c68..eb2b2ea3013 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -237,11 +237,10 @@ struct arraycache_init {
 /*
  * Need this for bootstrapping a per node allocator.
  */
-#define NUM_INIT_LISTS (3 * MAX_NUMNODES)
+#define NUM_INIT_LISTS (2 * MAX_NUMNODES)
 static struct kmem_cache_node __initdata init_kmem_cache_node[NUM_INIT_LISTS];
 #define	CACHE_CACHE 0
-#define	SIZE_AC MAX_NUMNODES
-#define	SIZE_NODE (2 * MAX_NUMNODES)
+#define	SIZE_NODE (MAX_NUMNODES)
 
 static int drain_freelist(struct kmem_cache *cache,
 			struct kmem_cache_node *n, int tofree);
@@ -253,7 +252,6 @@ static void cache_reap(struct work_struct *unused);
 
 static int slab_early_init = 1;
 
-#define INDEX_AC kmalloc_index(sizeof(struct arraycache_init))
 #define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node))
 
 static void kmem_cache_node_init(struct kmem_cache_node *parent)
@@ -458,9 +456,6 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache,
 	return reciprocal_divide(offset, cache->reciprocal_buffer_size);
 }
 
-static struct arraycache_init initarray_generic =
-    { {0, BOOT_CPUCACHE_ENTRIES, 1, 0} };
-
 /* internal cache of cache description objs */
 static struct kmem_cache kmem_cache_boot = {
 	.batchcount = 1,
@@ -476,7 +471,7 @@ static DEFINE_PER_CPU(struct delayed_work, slab_reap_work);
 
 static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
 {
-	return cachep->array[smp_processor_id()];
+	return this_cpu_ptr(cachep->cpu_cache);
 }
 
 static size_t calculate_freelist_size(int nr_objs, size_t align)
@@ -785,8 +780,8 @@ static inline void *ac_get_obj(struct kmem_cache *cachep,
 	return objp;
 }
 
-static void *__ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
-								void *objp)
+static noinline void *__ac_put_obj(struct kmem_cache *cachep,
+			struct array_cache *ac, void *objp)
 {
 	if (unlikely(pfmemalloc_active)) {
 		/* Some pfmemalloc slabs exist, check if this is one */
@@ -984,46 +979,50 @@ static void drain_alien_cache(struct kmem_cache *cachep,
 	}
 }
 
-static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
+static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
+				int node, int page_node)
 {
-	int nodeid = page_to_nid(virt_to_page(objp));
 	struct kmem_cache_node *n;
 	struct alien_cache *alien = NULL;
 	struct array_cache *ac;
-	int node;
 	LIST_HEAD(list);
 
-	node = numa_mem_id();
-
-	/*
-	 * Make sure we are not freeing a object from another node to the array
-	 * cache on this cpu.
-	 */
-	if (likely(nodeid == node))
-		return 0;
-
 	n = get_node(cachep, node);
 	STATS_INC_NODEFREES(cachep);
-	if (n->alien && n->alien[nodeid]) {
-		alien = n->alien[nodeid];
+	if (n->alien && n->alien[page_node]) {
+		alien = n->alien[page_node];
 		ac = &alien->ac;
 		spin_lock(&alien->lock);
 		if (unlikely(ac->avail == ac->limit)) {
 			STATS_INC_ACOVERFLOW(cachep);
-			__drain_alien_cache(cachep, ac, nodeid, &list);
+			__drain_alien_cache(cachep, ac, page_node, &list);
 		}
 		ac_put_obj(cachep, ac, objp);
 		spin_unlock(&alien->lock);
 		slabs_destroy(cachep, &list);
 	} else {
-		n = get_node(cachep, nodeid);
+		n = get_node(cachep, page_node);
 		spin_lock(&n->list_lock);
-		free_block(cachep, &objp, 1, nodeid, &list);
+		free_block(cachep, &objp, 1, page_node, &list);
 		spin_unlock(&n->list_lock);
 		slabs_destroy(cachep, &list);
 	}
 	return 1;
 }
+
+static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
+{
+	int page_node = page_to_nid(virt_to_page(objp));
+	int node = numa_mem_id();
+	/*
+	 * Make sure we are not freeing a object from another node to the array
+	 * cache on this cpu.
+	 */
+	if (likely(node == page_node))
+		return 0;
+
+	return __cache_free_alien(cachep, objp, node, page_node);
+}
 #endif
 
 /*
@@ -1092,24 +1091,25 @@ static void cpuup_canceled(long cpu)
 		struct alien_cache **alien;
 		LIST_HEAD(list);
 
-		/* cpu is dead; no one can alloc from it. */
-		nc = cachep->array[cpu];
-		cachep->array[cpu] = NULL;
 		n = get_node(cachep, node);
-
 		if (!n)
-			goto free_array_cache;
+			continue;
 
 		spin_lock_irq(&n->list_lock);
 
 		/* Free limit for this kmem_cache_node */
 		n->free_limit -= cachep->batchcount;
-		if (nc)
+
+		/* cpu is dead; no one can alloc from it. */
+		nc = per_cpu_ptr(cachep->cpu_cache, cpu);
+		if (nc) {
 			free_block(cachep, nc->entry, nc->avail, node, &list);
+			nc->avail = 0;
+		}
 
 		if (!cpumask_empty(mask)) {
 			spin_unlock_irq(&n->list_lock);
-			goto free_array_cache;
+			goto free_slab;
 		}
 
 		shared = n->shared;
@@ -1129,9 +1129,9 @@ static void cpuup_canceled(long cpu)
 			drain_alien_cache(cachep, alien);
 			free_alien_cache(alien);
 		}
-free_array_cache:
+
+free_slab:
 		slabs_destroy(cachep, &list);
-		kfree(nc);
 	}
 	/*
 	 * In the previous loop, all the objects were freed to
@@ -1168,32 +1168,23 @@ static int cpuup_prepare(long cpu)
 	 * array caches
 	 */
 	list_for_each_entry(cachep, &slab_caches, list) {
-		struct array_cache *nc;
 		struct array_cache *shared = NULL;
 		struct alien_cache **alien = NULL;
 
-		nc = alloc_arraycache(node, cachep->limit,
-					cachep->batchcount, GFP_KERNEL);
-		if (!nc)
-			goto bad;
 		if (cachep->shared) {
 			shared = alloc_arraycache(node,
 				cachep->shared * cachep->batchcount,
 				0xbaadf00d, GFP_KERNEL);
-			if (!shared) {
-				kfree(nc);
+			if (!shared)
 				goto bad;
-			}
 		}
 		if (use_alien_caches) {
 			alien = alloc_alien_cache(node, cachep->limit, GFP_KERNEL);
 			if (!alien) {
 				kfree(shared);
-				kfree(nc);
 				goto bad;
 			}
 		}
-		cachep->array[cpu] = nc;
 		n = get_node(cachep, node);
 		BUG_ON(!n);
 
@@ -1385,15 +1376,6 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
 }
 
 /*
- * The memory after the last cpu cache pointer is used for the
- * the node pointer.
- */
-static void setup_node_pointer(struct kmem_cache *cachep)
-{
-	cachep->node = (struct kmem_cache_node **)&cachep->array[nr_cpu_ids];
-}
-
-/*
  * Initialisation.  Called after the page allocator have been initialised and
  * before smp_init().
  */
@@ -1404,7 +1386,6 @@ void __init kmem_cache_init(void)
 	BUILD_BUG_ON(sizeof(((struct page *)NULL)->lru) <
 					sizeof(struct rcu_head));
 	kmem_cache = &kmem_cache_boot;
-	setup_node_pointer(kmem_cache);
 
 	if (num_possible_nodes() == 1)
 		use_alien_caches = 0;
@@ -1412,8 +1393,6 @@ void __init kmem_cache_init(void)
 	for (i = 0; i < NUM_INIT_LISTS; i++)
 		kmem_cache_node_init(&init_kmem_cache_node[i]);
 
-	set_up_node(kmem_cache, CACHE_CACHE);
-
 	/*
 	 * Fragmentation resistance on low memory - only use bigger
 	 * page orders on machines with more than 32MB of memory if
@@ -1448,49 +1427,22 @@ void __init kmem_cache_init(void)
 	 * struct kmem_cache size depends on nr_node_ids & nr_cpu_ids
 	 */
 	create_boot_cache(kmem_cache, "kmem_cache",
-		offsetof(struct kmem_cache, array[nr_cpu_ids]) +
+		offsetof(struct kmem_cache, node) +
 				  nr_node_ids * sizeof(struct kmem_cache_node *),
 				  SLAB_HWCACHE_ALIGN);
 	list_add(&kmem_cache->list, &slab_caches);
-
-	/* 2+3) create the kmalloc caches */
+	slab_state = PARTIAL;
 
 	/*
-	 * Initialize the caches that provide memory for the array cache and the
-	 * kmem_cache_node structures first.  Without this, further allocations will
-	 * bug.
+	 * Initialize the caches that provide memory for the  kmem_cache_node
+	 * structures first.  Without this, further allocations will bug.
 	 */
-
-	kmalloc_caches[INDEX_AC] = create_kmalloc_cache("kmalloc-ac",
-					kmalloc_size(INDEX_AC), ARCH_KMALLOC_FLAGS);
-
-	if (INDEX_AC != INDEX_NODE)
-		kmalloc_caches[INDEX_NODE] =
-			create_kmalloc_cache("kmalloc-node",
+	kmalloc_caches[INDEX_NODE] = create_kmalloc_cache("kmalloc-node",
 				kmalloc_size(INDEX_NODE), ARCH_KMALLOC_FLAGS);
+	slab_state = PARTIAL_NODE;
 
 	slab_early_init = 0;
 
-	/* 4) Replace the bootstrap head arrays */
-	{
-		struct array_cache *ptr;
-
-		ptr = kmalloc(sizeof(struct arraycache_init), GFP_NOWAIT);
-
-		memcpy(ptr, cpu_cache_get(kmem_cache),
-		       sizeof(struct arraycache_init));
-
-		kmem_cache->array[smp_processor_id()] = ptr;
-
-		ptr = kmalloc(sizeof(struct arraycache_init), GFP_NOWAIT);
-
-		BUG_ON(cpu_cache_get(kmalloc_caches[INDEX_AC])
-		       != &initarray_generic.cache);
-		memcpy(ptr, cpu_cache_get(kmalloc_caches[INDEX_AC]),
-		       sizeof(struct arraycache_init));
-
-		kmalloc_caches[INDEX_AC]->array[smp_processor_id()] = ptr;
-	}
 	/* 5) Replace the bootstrap kmem_cache_node */
 	{
 		int nid;
@@ -1498,13 +1450,8 @@ void __init kmem_cache_init(void)
 		for_each_online_node(nid) {
 			init_list(kmem_cache, &init_kmem_cache_node[CACHE_CACHE + nid], nid);
 
-			init_list(kmalloc_caches[INDEX_AC],
-				  &init_kmem_cache_node[SIZE_AC + nid], nid);
-
-			if (INDEX_AC != INDEX_NODE) {
-				init_list(kmalloc_caches[INDEX_NODE],
+			init_list(kmalloc_caches[INDEX_NODE],
 					  &init_kmem_cache_node[SIZE_NODE + nid], nid);
-			}
 		}
 	}
 
@@ -2037,56 +1984,53 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
 	return left_over;
 }
 
+static struct array_cache __percpu *alloc_kmem_cache_cpus(
+		struct kmem_cache *cachep, int entries, int batchcount)
+{
+	int cpu;
+	size_t size;
+	struct array_cache __percpu *cpu_cache;
+
+	size = sizeof(void *) * entries + sizeof(struct array_cache);
+	cpu_cache = __alloc_percpu(size, sizeof(void *));
+
+	if (!cpu_cache)
+		return NULL;
+
+	for_each_possible_cpu(cpu) {
+		init_arraycache(per_cpu_ptr(cpu_cache, cpu),
+				entries, batchcount);
+	}
+
+	return cpu_cache;
+}
+
 static int __init_refok setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
 {
 	if (slab_state >= FULL)
 		return enable_cpucache(cachep, gfp);
 
+	cachep->cpu_cache = alloc_kmem_cache_cpus(cachep, 1, 1);
+	if (!cachep->cpu_cache)
+		return 1;
+
 	if (slab_state == DOWN) {
-		/*
-		 * Note: Creation of first cache (kmem_cache).
-		 * The setup_node is taken care
-		 * of by the caller of __kmem_cache_create
-		 */
-		cachep->array[smp_processor_id()] = &initarray_generic.cache;
-		slab_state = PARTIAL;
+		/* Creation of first cache (kmem_cache). */
+		set_up_node(kmem_cache, CACHE_CACHE);
 	} else if (slab_state == PARTIAL) {
-		/*
-		 * Note: the second kmem_cache_create must create the cache
-		 * that's used by kmalloc(24), otherwise the creation of
-		 * further caches will BUG().
-		 */
-		cachep->array[smp_processor_id()] = &initarray_generic.cache;
-
-		/*
-		 * If the cache that's used by kmalloc(sizeof(kmem_cache_node)) is
-		 * the second cache, then we need to set up all its node/,
-		 * otherwise the creation of further caches will BUG().
-		 */
-		set_up_node(cachep, SIZE_AC);
-		if (INDEX_AC == INDEX_NODE)
-			slab_state = PARTIAL_NODE;
-		else
-			slab_state = PARTIAL_ARRAYCACHE;
+		/* For kmem_cache_node */
+		set_up_node(cachep, SIZE_NODE);
 	} else {
-		/* Remaining boot caches */
-		cachep->array[smp_processor_id()] =
-			kmalloc(sizeof(struct arraycache_init), gfp);
+		int node;
 
-		if (slab_state == PARTIAL_ARRAYCACHE) {
-			set_up_node(cachep, SIZE_NODE);
-			slab_state = PARTIAL_NODE;
-		} else {
-			int node;
-			for_each_online_node(node) {
-				cachep->node[node] =
-				    kmalloc_node(sizeof(struct kmem_cache_node),
-						gfp, node);
-				BUG_ON(!cachep->node[node]);
-				kmem_cache_node_init(cachep->node[node]);
-			}
+		for_each_online_node(node) {
+			cachep->node[node] = kmalloc_node(
+				sizeof(struct kmem_cache_node), gfp, node);
+			BUG_ON(!cachep->node[node]);
+			kmem_cache_node_init(cachep->node[node]);
 		}
 	}
+
 	cachep->node[numa_mem_id()]->next_reap =
 			jiffies + REAPTIMEOUT_NODE +
 			((unsigned long)cachep) % REAPTIMEOUT_NODE;
@@ -2100,6 +2044,32 @@ static int __init_refok setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
 	return 0;
 }
 
+unsigned long kmem_cache_flags(unsigned long object_size,
+	unsigned long flags, const char *name,
+	void (*ctor)(void *))
+{
+	return flags;
+}
+
+struct kmem_cache *
+__kmem_cache_alias(const char *name, size_t size, size_t align,
+		   unsigned long flags, void (*ctor)(void *))
+{
+	struct kmem_cache *cachep;
+
+	cachep = find_mergeable(size, align, flags, name, ctor);
+	if (cachep) {
+		cachep->refcount++;
+
+		/*
+		 * Adjust the object sizes so that we clear
+		 * the complete object on kzalloc.
+		 */
+		cachep->object_size = max_t(int, cachep->object_size, size);
+	}
+	return cachep;
+}
+
 /**
  * __kmem_cache_create - Create a cache.
  * @cachep: cache management descriptor
@@ -2124,7 +2094,8 @@ static int __init_refok setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
 int
 __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 {
-	size_t left_over, freelist_size, ralign;
+	size_t left_over, freelist_size;
+	size_t ralign = BYTES_PER_WORD;
 	gfp_t gfp;
 	int err;
 	size_t size = cachep->size;
@@ -2157,14 +2128,6 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 		size &= ~(BYTES_PER_WORD - 1);
 	}
 
-	/*
-	 * Redzoning and user store require word alignment or possibly larger.
-	 * Note this will be overridden by architecture or caller mandated
-	 * alignment if either is greater than BYTES_PER_WORD.
-	 */
-	if (flags & SLAB_STORE_USER)
-		ralign = BYTES_PER_WORD;
-
 	if (flags & SLAB_RED_ZONE) {
 		ralign = REDZONE_ALIGN;
 		/* If redzoning, ensure that the second redzone is suitably
@@ -2190,7 +2153,6 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 	else
 		gfp = GFP_NOWAIT;
 
-	setup_node_pointer(cachep);
 #if DEBUG
 
 	/*
@@ -2447,8 +2409,7 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep)
 	if (rc)
 		return rc;
 
-	for_each_online_cpu(i)
-	    kfree(cachep->array[i]);
+	free_percpu(cachep->cpu_cache);
 
 	/* NUMA: free the node structures */
 	for_each_kmem_cache_node(cachep, i, n) {
@@ -2994,7 +2955,7 @@ out:
 
 #ifdef CONFIG_NUMA
 /*
- * Try allocating on another node if PF_SPREAD_SLAB is a mempolicy is set.
+ * Try allocating on another node if PFA_SPREAD_SLAB is a mempolicy is set.
  *
  * If we are in_interrupt, then process context, including cpusets and
  * mempolicy, may not apply and should not be used for allocation policy.
@@ -3226,7 +3187,7 @@ __do_cache_alloc(struct kmem_cache *cache, gfp_t flags)
 {
 	void *objp;
 
-	if (current->mempolicy || unlikely(current->flags & PF_SPREAD_SLAB)) {
+	if (current->mempolicy || cpuset_do_slab_mem_spread()) {
 		objp = alternate_node_alloc(cache, flags);
 		if (objp)
 			goto out;
@@ -3406,7 +3367,7 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp,
 	if (nr_online_nodes > 1 && cache_free_alien(cachep, objp))
 		return;
 
-	if (likely(ac->avail < ac->limit)) {
+	if (ac->avail < ac->limit) {
 		STATS_INC_FREEHIT(cachep);
 	} else {
 		STATS_INC_FREEMISS(cachep);
@@ -3503,7 +3464,6 @@ __do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller)
 	return kmem_cache_alloc_node_trace(cachep, flags, node, size);
 }
 
-#if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_TRACING)
 void *__kmalloc_node(size_t size, gfp_t flags, int node)
 {
 	return __do_kmalloc_node(size, flags, node, _RET_IP_);
@@ -3516,13 +3476,6 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t flags,
 	return __do_kmalloc_node(size, flags, node, caller);
 }
 EXPORT_SYMBOL(__kmalloc_node_track_caller);
-#else
-void *__kmalloc_node(size_t size, gfp_t flags, int node)
-{
-	return __do_kmalloc_node(size, flags, node, 0);
-}
-EXPORT_SYMBOL(__kmalloc_node);
-#endif /* CONFIG_DEBUG_SLAB || CONFIG_TRACING */
 #endif /* CONFIG_NUMA */
 
 /**
@@ -3548,8 +3501,6 @@ static __always_inline void *__do_kmalloc(size_t size, gfp_t flags,
 	return ret;
 }
 
-
-#if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_TRACING)
 void *__kmalloc(size_t size, gfp_t flags)
 {
 	return __do_kmalloc(size, flags, _RET_IP_);
@@ -3562,14 +3513,6 @@ void *__kmalloc_track_caller(size_t size, gfp_t flags, unsigned long caller)
 }
 EXPORT_SYMBOL(__kmalloc_track_caller);
 
-#else
-void *__kmalloc(size_t size, gfp_t flags)
-{
-	return __do_kmalloc(size, flags, 0);
-}
-EXPORT_SYMBOL(__kmalloc);
-#endif
-
 /**
  * kmem_cache_free - Deallocate an object
  * @cachep: The cache the allocation was from.
@@ -3714,72 +3657,45 @@ fail:
 	return -ENOMEM;
 }
 
-struct ccupdate_struct {
-	struct kmem_cache *cachep;
-	struct array_cache *new[0];
-};
-
-static void do_ccupdate_local(void *info)
-{
-	struct ccupdate_struct *new = info;
-	struct array_cache *old;
-
-	check_irq_off();
-	old = cpu_cache_get(new->cachep);
-
-	new->cachep->array[smp_processor_id()] = new->new[smp_processor_id()];
-	new->new[smp_processor_id()] = old;
-}
-
 /* Always called with the slab_mutex held */
 static int __do_tune_cpucache(struct kmem_cache *cachep, int limit,
 				int batchcount, int shared, gfp_t gfp)
 {
-	struct ccupdate_struct *new;
-	int i;
+	struct array_cache __percpu *cpu_cache, *prev;
+	int cpu;
 
-	new = kzalloc(sizeof(*new) + nr_cpu_ids * sizeof(struct array_cache *),
-		      gfp);
-	if (!new)
+	cpu_cache = alloc_kmem_cache_cpus(cachep, limit, batchcount);
+	if (!cpu_cache)
 		return -ENOMEM;
 
-	for_each_online_cpu(i) {
-		new->new[i] = alloc_arraycache(cpu_to_mem(i), limit,
-						batchcount, gfp);
-		if (!new->new[i]) {
-			for (i--; i >= 0; i--)
-				kfree(new->new[i]);
-			kfree(new);
-			return -ENOMEM;
-		}
-	}
-	new->cachep = cachep;
-
-	on_each_cpu(do_ccupdate_local, (void *)new, 1);
+	prev = cachep->cpu_cache;
+	cachep->cpu_cache = cpu_cache;
+	kick_all_cpus_sync();
 
 	check_irq_on();
 	cachep->batchcount = batchcount;
 	cachep->limit = limit;
 	cachep->shared = shared;
 
-	for_each_online_cpu(i) {
+	if (!prev)
+		goto alloc_node;
+
+	for_each_online_cpu(cpu) {
 		LIST_HEAD(list);
-		struct array_cache *ccold = new->new[i];
 		int node;
 		struct kmem_cache_node *n;
+		struct array_cache *ac = per_cpu_ptr(prev, cpu);
 
-		if (!ccold)
-			continue;
-
-		node = cpu_to_mem(i);
+		node = cpu_to_mem(cpu);
 		n = get_node(cachep, node);
 		spin_lock_irq(&n->list_lock);
-		free_block(cachep, ccold->entry, ccold->avail, node, &list);
+		free_block(cachep, ac->entry, ac->avail, node, &list);
 		spin_unlock_irq(&n->list_lock);
 		slabs_destroy(cachep, &list);
-		kfree(ccold);
 	}
-	kfree(new);
+	free_percpu(prev);
+
+alloc_node:
 	return alloc_kmem_cache_node(cachep, gfp);
 }
 
@@ -4262,19 +4178,15 @@ static const struct seq_operations slabstats_op = {
 
 static int slabstats_open(struct inode *inode, struct file *file)
 {
-	unsigned long *n = kzalloc(PAGE_SIZE, GFP_KERNEL);
-	int ret = -ENOMEM;
-	if (n) {
-		ret = seq_open(file, &slabstats_op);
-		if (!ret) {
-			struct seq_file *m = file->private_data;
-			*n = PAGE_SIZE / (2 * sizeof(unsigned long));
-			m->private = n;
-			n = NULL;
-		}
-		kfree(n);
-	}
-	return ret;
+	unsigned long *n;
+
+	n = __seq_open_private(file, &slabstats_op, PAGE_SIZE);
+	if (!n)
+		return -ENOMEM;
+
+	*n = PAGE_SIZE / (2 * sizeof(unsigned long));
+
+	return 0;
 }
 
 static const struct file_operations proc_slabstats_operations = {