[PATCH 10/21] virtio scsi: Convert to hotplug state machine

Sebastian Andrzej Siewior
2016-09-06T17:06:29Z

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).

Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/scsi/virtio_scsi.c | 76 ++++++++++++++++++++++++++++++----------------
include/linux/cpuhotplug.h | 1 +
2 files changed, 50 insertions(+), 27 deletions(-)

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 7dbbb29d24c6..deefab3a94d0 100644
--- 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 @@ static int __init init(void)
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 a12044828e03..73a4daf08c04 100644
--- 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,
--
2.9.3