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Subject[tip:smp/hotplug] slab: Convert to hotplug state machine
Commit-ID:  e37b94bdb19a66c1164b0916c648da15c44ff39a
Gitweb: http://git.kernel.org/tip/e37b94bdb19a66c1164b0916c648da15c44ff39a
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Tue, 23 Aug 2016 14:53:19 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 6 Sep 2016 16:20:29 +0200

slab: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Link: http://lkml.kernel.org/r/20160823125319.abeapfjapf2kfezp@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
include/linux/slab.h | 8 ++++
kernel/cpu.c | 6 +++
mm/slab.c | 114 +++++++++++++++++++++++----------------------------
3 files changed, 65 insertions(+), 63 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 4293808..084b12b 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -650,4 +650,12 @@ static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
unsigned int kmem_cache_size(struct kmem_cache *s);
void __init kmem_cache_init_late(void);

+#if defined(CONFIG_SMP) && defined(CONFIG_SLAB)
+int slab_prepare_cpu(unsigned int cpu);
+int slab_dead_cpu(unsigned int cpu);
+#else
+#define slab_prepare_cpu NULL
+#define slab_dead_cpu NULL
+#endif
+
#endif /* _LINUX_SLAB_H */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 09f66cc..c70fae3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -24,6 +24,7 @@
#include <linux/irq.h>
#include <linux/smpboot.h>
#include <linux/relay.h>
+#include <linux/slab.h>

#include <trace/events/power.h>
#define CREATE_TRACE_POINTS
@@ -1278,6 +1279,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
.startup = relay_prepare_cpu,
.teardown = NULL,
},
+ [CPUHP_SLAB_PREPARE] = {
+ .name = "slab:prepare",
+ .startup = slab_prepare_cpu,
+ .teardown = slab_dead_cpu,
+ },
[CPUHP_RCUTREE_PREP] = {
.name = "RCU/tree:prepare",
.startup.single = rcutree_prepare_cpu,
diff --git a/mm/slab.c b/mm/slab.c
index b672710..090fb26 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -886,6 +886,7 @@ static int init_cache_node(struct kmem_cache *cachep, int node, gfp_t gfp)
return 0;
}

+#if (defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)) || defined(CONFIG_SMP)
/*
* Allocates and initializes node for a node on each slab cache, used for
* either memory or cpu hotplug. If memory is being hot-added, the kmem_cache_node
@@ -908,6 +909,7 @@ static int init_cache_node_node(int node)

return 0;
}
+#endif

static int setup_kmem_cache_node(struct kmem_cache *cachep,
int node, gfp_t gfp, bool force_change)
@@ -975,6 +977,8 @@ fail:
return ret;
}

+#ifdef CONFIG_SMP
+
static void cpuup_canceled(long cpu)
{
struct kmem_cache *cachep;
@@ -1075,65 +1079,54 @@ bad:
return -ENOMEM;
}

-static int cpuup_callback(struct notifier_block *nfb,
- unsigned long action, void *hcpu)
+int slab_prepare_cpu(unsigned int cpu)
{
- long cpu = (long)hcpu;
- int err = 0;
+ int err;

- switch (action) {
- case CPU_UP_PREPARE:
- case CPU_UP_PREPARE_FROZEN:
- mutex_lock(&slab_mutex);
- err = cpuup_prepare(cpu);
- mutex_unlock(&slab_mutex);
- break;
- case CPU_ONLINE:
- case CPU_ONLINE_FROZEN:
- start_cpu_timer(cpu);
- break;
-#ifdef CONFIG_HOTPLUG_CPU
- case CPU_DOWN_PREPARE:
- case CPU_DOWN_PREPARE_FROZEN:
- /*
- * Shutdown cache reaper. Note that the slab_mutex is
- * held so that if cache_reap() is invoked it cannot do
- * anything expensive but will only modify reap_work
- * and reschedule the timer.
- */
- cancel_delayed_work_sync(&per_cpu(slab_reap_work, cpu));
- /* Now the cache_reaper is guaranteed to be not running. */
- per_cpu(slab_reap_work, cpu).work.func = NULL;
- break;
- case CPU_DOWN_FAILED:
- case CPU_DOWN_FAILED_FROZEN:
- start_cpu_timer(cpu);
- break;
- case CPU_DEAD:
- case CPU_DEAD_FROZEN:
- /*
- * Even if all the cpus of a node are down, we don't free the
- * kmem_cache_node of any cache. This to avoid a race between
- * cpu_down, and a kmalloc allocation from another cpu for
- * memory from the node of the cpu going down. The node
- * structure is usually allocated from kmem_cache_create() and
- * gets destroyed at kmem_cache_destroy().
- */
- /* fall through */
+ mutex_lock(&slab_mutex);
+ err = cpuup_prepare(cpu);
+ mutex_unlock(&slab_mutex);
+ return err;
+}
+
+/*
+ * This is called for a failed online attempt and for a successful
+ * offline.
+ *
+ * Even if all the cpus of a node are down, we don't free the
+ * kmem_list3 of any cache. This to avoid a race between cpu_down, and
+ * a kmalloc allocation from another cpu for memory from the node of
+ * the cpu going down. The list3 structure is usually allocated from
+ * kmem_cache_create() and gets destroyed at kmem_cache_destroy().
+ */
+int slab_dead_cpu(unsigned int cpu)
+{
+ mutex_lock(&slab_mutex);
+ cpuup_canceled(cpu);
+ mutex_unlock(&slab_mutex);
+ return 0;
+}
#endif
- case CPU_UP_CANCELED:
- case CPU_UP_CANCELED_FROZEN:
- mutex_lock(&slab_mutex);
- cpuup_canceled(cpu);
- mutex_unlock(&slab_mutex);
- break;
- }
- return notifier_from_errno(err);
+
+static int slab_online_cpu(unsigned int cpu)
+{
+ start_cpu_timer(cpu);
+ return 0;
}

-static struct notifier_block cpucache_notifier = {
- &cpuup_callback, NULL, 0
-};
+static int slab_offline_cpu(unsigned int cpu)
+{
+ /*
+ * Shutdown cache reaper. Note that the slab_mutex is held so
+ * that if cache_reap() is invoked it cannot do anything
+ * expensive but will only modify reap_work and reschedule the
+ * timer.
+ */
+ cancel_delayed_work_sync(&per_cpu(slab_reap_work, cpu));
+ /* Now the cache_reaper is guaranteed to be not running. */
+ per_cpu(slab_reap_work, cpu).work.func = NULL;
+ return 0;
+}

#if defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)
/*
@@ -1336,12 +1329,6 @@ void __init kmem_cache_init_late(void)
/* Done! */
slab_state = FULL;

- /*
- * Register a cpu startup notifier callback that initializes
- * cpu_cache_get for all new cpus
- */
- register_cpu_notifier(&cpucache_notifier);
-
#ifdef CONFIG_NUMA
/*
* Register a memory hotplug callback that initializes and frees
@@ -1358,13 +1345,14 @@ void __init kmem_cache_init_late(void)

static int __init cpucache_init(void)
{
- int cpu;
+ int ret;

/*
* Register the timers that return unneeded pages to the page allocator
*/
- for_each_online_cpu(cpu)
- start_cpu_timer(cpu);
+ ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "SLAB online",
+ slab_online_cpu, slab_offline_cpu);
+ WARN_ON(ret < 0);

/* Done! */
slab_state = FULL;
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