virtio scsi: Convert to hotplug state machine

Install the callbacks via the state machine. It uses the multi instance
infrastructure of the hotplug code to handle each interface.

virtscsi_set_affinity() is removed from virtscsi_init() because
virtscsi_cpu_notif_add() (the function which registers the instance) is invoked
right after it and the cpuhp_state_add_instance() functions invokes the startup
callback on all online CPUs.

The same thing can not be applied virtscsi_cpu_notif_remove() because
virtscsi_remove_vqs() invokes virtscsi_set_affinity() with affinity = false as
argument but the old CPU_DEAD state invoked the function with affinity = true
(which does not match the DEAD callback).

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: virtualization@lists.linux-foundation.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160906170457.32393-11-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 7dbbb29d24c6cf5290cd06a7a97df570a8860f18..deefab3a94d0ff386b304adcd8e341181fd21101 100644 (file)
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -107,8 +107,8 @@ struct virtio_scsi {
        /* If the affinity hint is set for virtqueues */
        bool affinity_hint_set;
 
-       /* CPU hotplug notifier */
-       struct notifier_block nb;
+       struct hlist_node node;
+       struct hlist_node node_dead;
 
        /* Protected by event_vq lock */
        bool stop_events;
@@ -118,6 +118,7 @@ struct virtio_scsi {
        struct virtio_scsi_vq req_vqs[];
 };
 
+static enum cpuhp_state virtioscsi_online;
 static struct kmem_cache *virtscsi_cmd_cache;
 static mempool_t *virtscsi_cmd_pool;
 
@@ -852,21 +853,33 @@ static void virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
        put_online_cpus();
 }
 
-static int virtscsi_cpu_callback(struct notifier_block *nfb,
-                                unsigned long action, void *hcpu)
+static int virtscsi_cpu_online(unsigned int cpu, struct hlist_node *node)
 {
-       struct virtio_scsi *vscsi = container_of(nfb, struct virtio_scsi, nb);
-       switch(action) {
-       case CPU_ONLINE:
-       case CPU_ONLINE_FROZEN:
-       case CPU_DEAD:
-       case CPU_DEAD_FROZEN:
-               __virtscsi_set_affinity(vscsi, true);
-               break;
-       default:
-               break;
-       }
-       return NOTIFY_OK;
+       struct virtio_scsi *vscsi = hlist_entry_safe(node, struct virtio_scsi,
+                                                    node);
+       __virtscsi_set_affinity(vscsi, true);
+       return 0;
+}
+
+static int virtscsi_cpu_notif_add(struct virtio_scsi *vi)
+{
+       int ret;
+
+       ret = cpuhp_state_add_instance(virtioscsi_online, &vi->node);
+       if (ret)
+               return ret;
+
+       ret = cpuhp_state_add_instance(CPUHP_VIRT_SCSI_DEAD, &vi->node_dead);
+       if (ret)
+               cpuhp_state_remove_instance(virtioscsi_online, &vi->node);
+       return ret;
+}
+
+static void virtscsi_cpu_notif_remove(struct virtio_scsi *vi)
+{
+       cpuhp_state_remove_instance_nocalls(virtioscsi_online, &vi->node);
+       cpuhp_state_remove_instance_nocalls(CPUHP_VIRT_SCSI_DEAD,
+                                           &vi->node_dead);
 }
 
 static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
@@ -929,8 +942,6 @@ static int virtscsi_init(struct virtio_device *vdev,
                virtscsi_init_vq(&vscsi->req_vqs[i - VIRTIO_SCSI_VQ_BASE],
                                 vqs[i]);
 
-       virtscsi_set_affinity(vscsi, true);
-
        virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
        virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);
 
@@ -987,12 +998,9 @@ static int virtscsi_probe(struct virtio_device *vdev)
        if (err)
                goto virtscsi_init_failed;
 
-       vscsi->nb.notifier_call = &virtscsi_cpu_callback;
-       err = register_hotcpu_notifier(&vscsi->nb);
-       if (err) {
-               pr_err("registering cpu notifier failed\n");
+       err = virtscsi_cpu_notif_add(vscsi);
+       if (err)
                goto scsi_add_host_failed;
-       }
 
        cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
        shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue);
@@ -1049,7 +1057,7 @@ static void virtscsi_remove(struct virtio_device *vdev)
 
        scsi_remove_host(shost);
 
-       unregister_hotcpu_notifier(&vscsi->nb);
+       virtscsi_cpu_notif_remove(vscsi);
 
        virtscsi_remove_vqs(vdev);
        scsi_host_put(shost);
@@ -1061,7 +1069,7 @@ static int virtscsi_freeze(struct virtio_device *vdev)
        struct Scsi_Host *sh = virtio_scsi_host(vdev);
        struct virtio_scsi *vscsi = shost_priv(sh);
 
-       unregister_hotcpu_notifier(&vscsi->nb);
+       virtscsi_cpu_notif_remove(vscsi);
        virtscsi_remove_vqs(vdev);
        return 0;
 }
@@ -1076,12 +1084,11 @@ static int virtscsi_restore(struct virtio_device *vdev)
        if (err)
                return err;
 
-       err = register_hotcpu_notifier(&vscsi->nb);
+       err = virtscsi_cpu_notif_add(vscsi);
        if (err) {
                vdev->config->del_vqs(vdev);
                return err;
        }
-
        virtio_device_ready(vdev);
 
        if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
@@ -1136,6 +1143,16 @@ static int __init init(void)
                pr_err("mempool_create() for virtscsi_cmd_pool failed\n");
                goto error;
        }
+       ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
+                                     "scsi/virtio:online",
+                                     virtscsi_cpu_online, NULL);
+       if (ret < 0)
+               goto error;
+       virtioscsi_online = ret;
+       ret = cpuhp_setup_state_multi(CPUHP_VIRT_SCSI_DEAD, "scsi/virtio:dead",
+                                     NULL, virtscsi_cpu_online);
+       if (ret)
+               goto error;
        ret = register_virtio_driver(&virtio_scsi_driver);
        if (ret < 0)
                goto error;
@@ -1151,12 +1168,17 @@ error:
                kmem_cache_destroy(virtscsi_cmd_cache);
                virtscsi_cmd_cache = NULL;
        }
+       if (virtioscsi_online)
+               cpuhp_remove_multi_state(virtioscsi_online);
+       cpuhp_remove_multi_state(CPUHP_VIRT_SCSI_DEAD);
        return ret;
 }
 
 static void __exit fini(void)
 {
        unregister_virtio_driver(&virtio_scsi_driver);
+       cpuhp_remove_multi_state(virtioscsi_online);
+       cpuhp_remove_multi_state(CPUHP_VIRT_SCSI_DEAD);
        mempool_destroy(virtscsi_cmd_pool);
        kmem_cache_destroy(virtscsi_cmd_cache);
 }

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index d4274d51fe27936c5436d65da3e9011c26923908..e7146ee88ea4f573baf759b3fb8f26a5bab95ed4 100644 (file)
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -24,6 +24,7 @@ enum cpuhp_state {
        CPUHP_ARM_OMAP_WAKE_DEAD,
        CPUHP_IRQ_POLL_DEAD,
        CPUHP_BLOCK_SOFTIRQ_DEAD,
+       CPUHP_VIRT_SCSI_DEAD,
        CPUHP_WORKQUEUE_PREP,
        CPUHP_POWER_NUMA_PREPARE,
        CPUHP_HRTIMERS_PREPARE,