[SCSI] virtio-scsi: Add vdrv->scan for post VIRTIO_CONFIG_S_DRIVER_OK LUN scanning

This patch changes virtio-scsi to use a new virtio_driver->scan() callback
so that scsi_scan_host() can be properly invoked once virtio_dev_probe() has
set add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK) to signal active virtio-ring
operation, instead of from within virtscsi_probe().

This fixes a bug where SCSI LUN scanning for both virtio-scsi-raw and
virtio-scsi/tcm_vhost setups was happening before VIRTIO_CONFIG_S_DRIVER_OK
had been set, causing VIRTIO_SCSI_S_BAD_TARGET to occur.  This fixes a bug
with virtio-scsi/tcm_vhost where LUN scan was not detecting LUNs.

Tested with virtio-scsi-raw + virtio-scsi/tcm_vhost w/ IBLOCK on 3.5-rc2 code.

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

3 files changed, 17 insertions, 4 deletions

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index ae3bef7c523f..c7030fbee79c 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -571,6 +571,13 @@ static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
         return tgt;
 }
 
+static void virtscsi_scan(struct virtio_device *vdev)
+{
+        struct Scsi_Host *shost = (struct Scsi_Host *)vdev->priv;
+
+        scsi_scan_host(shost);
+}
+
 static void virtscsi_remove_vqs(struct virtio_device *vdev)
 {
         struct Scsi_Host *sh = virtio_scsi_host(vdev);
@@ -677,9 +684,10 @@ static int __devinit virtscsi_probe(struct virtio_device *vdev)
         err = scsi_add_host(shost, &vdev->dev);
         if (err)
                 goto scsi_add_host_failed;
-
-        scsi_scan_host(shost);
-
+        /*
+         * scsi_scan_host() happens in virtscsi_scan() via virtio_driver->scan()
+         * after VIRTIO_CONFIG_S_DRIVER_OK has been set..
+         */
         return 0;
 
 scsi_add_host_failed:
@@ -735,6 +743,7 @@ static struct virtio_driver virtio_scsi_driver = {
         .driver.owner = THIS_MODULE,
         .id_table = id_table,
         .probe = virtscsi_probe,
+        .scan = virtscsi_scan,
 #ifdef CONFIG_PM
         .freeze = virtscsi_freeze,
         .restore = virtscsi_restore,
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index f3558070e375..c3b3f7f0d9d1 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -141,8 +141,11 @@ static int virtio_dev_probe(struct device *_d)
         err = drv->probe(dev);
         if (err)
                 add_status(dev, VIRTIO_CONFIG_S_FAILED);
-        else
+        else {
                 add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
+                if (drv->scan)
+                        drv->scan(dev);
+        }
 
         return err;
 }
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 8efd28ae5597..a1ba8bbd9fbe 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -92,6 +92,7 @@ struct virtio_driver {
         const unsigned int *feature_table;
         unsigned int feature_table_size;
         int (*probe)(struct virtio_device *dev);
+        void (*scan)(struct virtio_device *dev);
         void (*remove)(struct virtio_device *dev);
         void (*config_changed)(struct virtio_device *dev);
 #ifdef CONFIG_PM