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@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jens Axboe <axboe@fb.com>
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20160818125731.27256-6-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 8 insertions, 19 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 82ee32107dff..854e59a426d4 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 f4cd7d8005c9..28d6f36a2d79 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);
 }
 
 /**