[SCSI] virtio-scsi: support online resizing of disks

Support the LUN parameter change event.  Currently, the host fires this event
when the capacity of a disk is changed from the virtual machine monitor.
The resize then appears in the kernel log like this:

  sd 0:0:0:0: [sda] 46137344 512-byte logical blocks: (23.6 GB/22.0 GIb)
  sda: detected capacity change from 22548578304 to 23622320128

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 30 insertions, 1 deletions

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index a7cf726bc747..595af1ae4421 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -279,6 +279,31 @@ static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
         }
 }
 
+static void virtscsi_handle_param_change(struct virtio_scsi *vscsi,
+                                         struct virtio_scsi_event *event)
+{
+        struct scsi_device *sdev;
+        struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
+        unsigned int target = event->lun[1];
+        unsigned int lun = (event->lun[2] << 8) | event->lun[3];
+        u8 asc = event->reason & 255;
+        u8 ascq = event->reason >> 8;
+
+        sdev = scsi_device_lookup(shost, 0, target, lun);
+        if (!sdev) {
+                pr_err("SCSI device %d 0 %d %d not found\n",
+                        shost->host_no, target, lun);
+                return;
+        }
+
+        /* Handle "Parameters changed", "Mode parameters changed", and
+           "Capacity data has changed".  */
+        if (asc == 0x2a && (ascq == 0x00 || ascq == 0x01 || ascq == 0x09))
+                scsi_rescan_device(&sdev->sdev_gendev);
+
+        scsi_device_put(sdev);
+}
+
 static void virtscsi_handle_event(struct work_struct *work)
 {
         struct virtio_scsi_event_node *event_node =
@@ -297,6 +322,9 @@ static void virtscsi_handle_event(struct work_struct *work)
         case VIRTIO_SCSI_T_TRANSPORT_RESET:
                 virtscsi_handle_transport_reset(vscsi, event);
                 break;
+        case VIRTIO_SCSI_T_PARAM_CHANGE:
+                virtscsi_handle_param_change(vscsi, event);
+                break;
         default:
                 pr_err("Unsupport virtio scsi event %x\n", event->event);
         }
@@ -737,7 +765,8 @@ static struct virtio_device_id id_table[] = {
 };
 
 static unsigned int features[] = {
-        VIRTIO_SCSI_F_HOTPLUG
+        VIRTIO_SCSI_F_HOTPLUG,
+        VIRTIO_SCSI_F_CHANGE,
 };
 
 static struct virtio_driver virtio_scsi_driver = {