[PATCH v3 5/5] virtio-scsi: reset virtqueue affinity when doing cpu hotplug

[Paolo Bonzini <pbonzini@redhat.com>]

From: Wanlong Gao <gaowanlong@cn.fujitsu.com>

Add hot cpu notifier to reset the request virtqueue affinity
when doing cpu hotplug.

Cc: linux-scsi@vger.kernel.org
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
[ The version that doesn't get/put_online_cpus is now called
  __virtscsi_set_affinity - Paolo ]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 drivers/scsi/virtio_scsi.c |   31 +++++++++++++++++++++++++++++++
 1 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index a2bdae1..733307a 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -20,6 +20,7 @@
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.h>
 #include <linux/virtio_scsi.h>
+#include <linux/cpu.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_device.h>
 #include <scsi/scsi_cmnd.h>
@@ -109,6 +110,9 @@ struct virtio_scsi {
 	/* Does the affinity hint is set for virtqueues? */
 	bool affinity_hint_set;
 
+	/* CPU hotplug notifier */
+	struct notifier_block nb;
+
 	struct virtio_scsi_vq ctrl_vq;
 	struct virtio_scsi_vq event_vq;
 	struct virtio_scsi_vq req_vqs[];
@@ -734,6 +738,7 @@ static void __virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
 	}
 }
 
+
 static void virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
 {
 	get_online_cpus();
@@ -741,6 +746,23 @@ 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)
+{
+	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;
+}
+
 static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
 			     struct virtqueue *vq)
 {
@@ -885,6 +907,13 @@ 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("virtio_scsi: registering cpu notifier failed\n");
+		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);
 	shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF;
@@ -922,6 +951,8 @@ static void virtscsi_remove(struct virtio_device *vdev)
 
 	scsi_remove_host(shost);
 
+	unregister_hotcpu_notifier(&vscsi->nb);
+
 	virtscsi_remove_vqs(vdev);
 	scsi_host_put(shost);
 }
-- 
1.7.1