mm/compaction: Convert to hotplug state machine

Install the callbacks via the state machine. Should the hotplug init fail then
no threads are spawned.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20161126231350.10321-15-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 18 insertions, 13 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 0409a4ad6ea1..0d37192d9423 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2043,33 +2043,38 @@ void kcompactd_stop(int nid)
  * away, we get changed to run anywhere: as the first one comes back,
  * restore their cpu bindings.
  */
-static int cpu_callback(struct notifier_block *nfb, unsigned long action,
-                        void *hcpu)
+static int kcompactd_cpu_online(unsigned int cpu)
 {
         int nid;
 
-        if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
-                for_each_node_state(nid, N_MEMORY) {
-                        pg_data_t *pgdat = NODE_DATA(nid);
-                        const struct cpumask *mask;
+        for_each_node_state(nid, N_MEMORY) {
+                pg_data_t *pgdat = NODE_DATA(nid);
+                const struct cpumask *mask;
 
-                        mask = cpumask_of_node(pgdat->node_id);
+                mask = cpumask_of_node(pgdat->node_id);
 
-                        if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
-                                /* One of our CPUs online: restore mask */
-                                set_cpus_allowed_ptr(pgdat->kcompactd, mask);
-                }
+                if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
+                        /* One of our CPUs online: restore mask */
+                        set_cpus_allowed_ptr(pgdat->kcompactd, mask);
         }
-        return NOTIFY_OK;
+        return 0;
 }
 
 static int __init kcompactd_init(void)
 {
         int nid;
+        int ret;
+
+        ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+                                        "mm/compaction:online",
+                                        kcompactd_cpu_online, NULL);
+        if (ret < 0) {
+                pr_err("kcompactd: failed to register hotplug callbacks.\n");
+                return ret;
+        }
 
         for_each_node_state(nid, N_MEMORY)
                 kcompactd_run(nid);
-        hotcpu_notifier(cpu_callback, 0);
         return 0;
 }
 subsys_initcall(kcompactd_init)