slub: Convert to hotplug state machine

Install the callbacks via the state machine.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Link: http://lkml.kernel.org/r/20160818125731.27256-5-bigeasy@linutronix.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/cpuhotplug.h

@@ -15,6 +15,7 @@ enum cpuhp_state {
 	CPUHP_X86_HPET_DEAD,
 	CPUHP_X86_APB_DEAD,
 	CPUHP_VIRT_NET_DEAD,
+	CPUHP_SLUB_DEAD,
 	CPUHP_WORKQUEUE_PREP,
 	CPUHP_POWER_NUMA_PREPARE,
 	CPUHP_HRTIMERS_PREPARE,

mm/slub.c

@@ -194,10 +194,6 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
 #define __OBJECT_POISON		0x80000000UL /* Poison object */
 #define __CMPXCHG_DOUBLE	0x40000000UL /* Use cmpxchg_double */
 
-#ifdef CONFIG_SMP
-static struct notifier_block slab_notifier;
-#endif
-
 /*
  * Tracking user of a slab.
  */
@@ -2304,6 +2300,25 @@ static void flush_all(struct kmem_cache *s)
 	on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1, GFP_ATOMIC);
 }
 
+/*
+ * Use the cpu notifier to insure that the cpu slabs are flushed when
+ * necessary.
+ */
+static int slub_cpu_dead(unsigned int cpu)
+{
+	struct kmem_cache *s;
+	unsigned long flags;
+
+	mutex_lock(&slab_mutex);
+	list_for_each_entry(s, &slab_caches, list) {
+		local_irq_save(flags);
+		__flush_cpu_slab(s, cpu);
+		local_irq_restore(flags);
+	}
+	mutex_unlock(&slab_mutex);
+	return 0;
+}
+
 /*
  * Check if the objects in a per cpu structure fit numa
  * locality expectations.
@@ -4144,9 +4159,8 @@ void __init kmem_cache_init(void)
 	/* Setup random freelists for each cache */
 	init_freelist_randomization();
 
-#ifdef CONFIG_SMP
-	register_cpu_notifier(&slab_notifier);
-#endif
+	cpuhp_setup_state_nocalls(CPUHP_SLUB_DEAD, "slub:dead", NULL,
+				  slub_cpu_dead);
 
 	pr_info("SLUB: HWalign=%d, Order=%d-%d, MinObjects=%d, CPUs=%d, Nodes=%d\n",
 		cache_line_size(),
@@ -4210,43 +4224,6 @@ int __kmem_cache_create(struct kmem_cache *s, unsigned long flags)
 	return err;
 }
 
-#ifdef CONFIG_SMP
-/*
- * Use the cpu notifier to insure that the cpu slabs are flushed when
- * necessary.
- */
-static int slab_cpuup_callback(struct notifier_block *nfb,
-		unsigned long action, void *hcpu)
-{
-	long cpu = (long)hcpu;
-	struct kmem_cache *s;
-	unsigned long flags;
-
-	switch (action) {
-	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		mutex_lock(&slab_mutex);
-		list_for_each_entry(s, &slab_caches, list) {
-			local_irq_save(flags);
-			__flush_cpu_slab(s, cpu);
-			local_irq_restore(flags);
-		}
-		mutex_unlock(&slab_mutex);
-		break;
-	default:
-		break;
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block slab_notifier = {
-	.notifier_call = slab_cpuup_callback
-};
-
-#endif
-
 void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller)
 {
 	struct kmem_cache *s;