[tip:smp/hotplug] mm/writeback: Convert to hotplug state machine

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  1d7ac6aec947d222042b6d22b3cec109db4fd19e
Gitweb:     http://git.kernel.org/tip/1d7ac6aec947d222042b6d22b3cec109db4fd19e
Author:     Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate: Thu, 18 Aug 2016 14:57:20 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 6 Sep 2016 18:30:20 +0200

mm/writeback: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: rt@xxxxxxxxxxxxx
Cc: Tejun Heo <tj@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20160818125731.27256-6-bigeasy@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---
 include/linux/cpuhotplug.h |  1 +
 mm/page-writeback.c        | 26 +++++++-------------------
 2 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 82ee321..854e59a 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -16,6 +16,7 @@ enum cpuhp_state {
 	CPUHP_X86_APB_DEAD,
 	CPUHP_VIRT_NET_DEAD,
 	CPUHP_SLUB_DEAD,
+	CPUHP_MM_WRITEBACK_DEAD,
 	CPUHP_WORKQUEUE_PREP,
 	CPUHP_POWER_NUMA_PREPARE,
 	CPUHP_HRTIMERS_PREPARE,
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index f4cd7d8..28d6f36 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2080,26 +2080,12 @@ void writeback_set_ratelimit(void)
 		ratelimit_pages = 16;
 }
 
-static int
-ratelimit_handler(struct notifier_block *self, unsigned long action,
-		  void *hcpu)
+static int page_writeback_cpu_online(unsigned int cpu)
 {
-
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_ONLINE:
-	case CPU_DEAD:
-		writeback_set_ratelimit();
-		return NOTIFY_OK;
-	default:
-		return NOTIFY_DONE;
-	}
+	writeback_set_ratelimit();
+	return 0;
 }
 
-static struct notifier_block ratelimit_nb = {
-	.notifier_call	= ratelimit_handler,
-	.next		= NULL,
-};
-
 /*
  * Called early on to tune the page writeback dirty limits.
  *
@@ -2122,8 +2108,10 @@ void __init page_writeback_init(void)
 {
 	BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL));
 
-	writeback_set_ratelimit();
-	register_cpu_notifier(&ratelimit_nb);
+	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online",
+			  page_writeback_cpu_online, NULL);
+	cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL,
+			  page_writeback_cpu_online);
 }
 
 /**