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>

diff --git a/mm/compaction.c b/mm/compaction.c
index 0409a4ad6ea1363611d49269ecbb5ef88afe5c87..0d37192d9423996edf17c717d94936987c9e80b8 100644 (file)
--- 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)