virtio-scsi: redo allocation of target data

virtio_scsi_target_state is now empty.  We will find new uses for it in
the next few patches, so this patch does not drop it completely.

And as James suggested, we use entries target_alloc and target_destroy
in the host template to allocate and destroy the virtio_scsi_target_state
of each target, attach this struct to scsi_target->hostdata. Now
we can get at it from the sdev with scsi_target(sdev)->hostdata.
No messing around with fixed size arrays and bulk memory allocation
and no need to pass in the maximum target size as a parameter because
everything should now happen dynamically.

Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Reviewed-by: Asias He <asias@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/scsi/virtio_scsi.c

@@ -75,8 +75,6 @@ struct virtio_scsi {
 
 	/* Get some buffers ready for event vq */
 	struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
-
-	struct virtio_scsi_target_state *tgt[];
 };
 
 static struct kmem_cache *virtscsi_cmd_cache;
@@ -530,6 +528,25 @@ static int virtscsi_abort(struct scsi_cmnd *sc)
 	return virtscsi_tmf(vscsi, cmd);
 }
 
+static int virtscsi_target_alloc(struct scsi_target *starget)
+{
+	struct virtio_scsi_target_state *tgt =
+				kmalloc(sizeof(*tgt), GFP_KERNEL);
+	if (!tgt)
+		return -ENOMEM;
+
+	spin_lock_init(&tgt->tgt_lock);
+
+	starget->hostdata = tgt;
+	return 0;
+}
+
+static void virtscsi_target_destroy(struct scsi_target *starget)
+{
+	struct virtio_scsi_target_state *tgt = starget->hostdata;
+	kfree(tgt);
+}
+
 static struct scsi_host_template virtscsi_host_template = {
 	.module = THIS_MODULE,
 	.name = "Virtio SCSI HBA",
@@ -542,6 +559,8 @@ static struct scsi_host_template virtscsi_host_template = {
 	.can_queue = 1024,
 	.dma_boundary = UINT_MAX,
 	.use_clustering = ENABLE_CLUSTERING,
+	.target_alloc = virtscsi_target_alloc,
+	.target_destroy = virtscsi_target_destroy,
 };
 
 #define virtscsi_config_get(vdev, fld) \
@@ -568,20 +587,6 @@ static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
 	virtscsi_vq->vq = vq;
 }
 
-static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
-	struct virtio_device *vdev)
-{
-	struct virtio_scsi_target_state *tgt;
-	gfp_t gfp_mask = GFP_KERNEL;
-
-	tgt = kmalloc(sizeof(*tgt), gfp_mask);
-	if (!tgt)
-		return NULL;
-
-	spin_lock_init(&tgt->tgt_lock);
-	return tgt;
-}
-
 static void virtscsi_scan(struct virtio_device *vdev)
 {
 	struct Scsi_Host *shost = (struct Scsi_Host *)vdev->priv;
@@ -591,28 +596,17 @@ static void virtscsi_scan(struct virtio_device *vdev)
 
 static void virtscsi_remove_vqs(struct virtio_device *vdev)
 {
-	struct Scsi_Host *sh = virtio_scsi_host(vdev);
-	struct virtio_scsi *vscsi = shost_priv(sh);
-	u32 i, num_targets;
-
 	/* Stop all the virtqueues. */
 	vdev->config->reset(vdev);
 
-	num_targets = sh->max_id;
-	for (i = 0; i < num_targets; i++) {
-		kfree(vscsi->tgt[i]);
-		vscsi->tgt[i] = NULL;
-	}
-
 	vdev->config->del_vqs(vdev);
 }
 
 static int virtscsi_init(struct virtio_device *vdev,
-			 struct virtio_scsi *vscsi, int num_targets)
+			 struct virtio_scsi *vscsi)
 {
 	int err;
 	struct virtqueue *vqs[3];
-	u32 i;
 
 	vq_callback_t *callbacks[] = {
 		virtscsi_ctrl_done,
@@ -640,18 +634,6 @@ static int virtscsi_init(struct virtio_device *vdev,
 	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
 		virtscsi_kick_event_all(vscsi);
 
-	for (i = 0; i < num_targets; i++) {
-		vscsi->tgt[i] = virtscsi_alloc_tgt(vdev);
-		if (!vscsi->tgt[i]) {
-			err = -ENOMEM;
-			goto out;
-		}
-	}
-	err = 0;
-
-out:
-	if (err)
-		virtscsi_remove_vqs(vdev);
 	return err;
 }
 
@@ -663,12 +645,9 @@ static int virtscsi_probe(struct virtio_device *vdev)
 	u32 sg_elems, num_targets;
 	u32 cmd_per_lun;
 
-	/* Allocate memory and link the structs together.  */
 	num_targets = virtscsi_config_get(vdev, max_target) + 1;
-	shost = scsi_host_alloc(&virtscsi_host_template,
-		sizeof(*vscsi)
-		+ num_targets * sizeof(struct virtio_scsi_target_state));
 
+	shost = scsi_host_alloc(&virtscsi_host_template, sizeof(*vscsi));
 	if (!shost)
 		return -ENOMEM;
 
@@ -678,7 +657,7 @@ static int virtscsi_probe(struct virtio_device *vdev)
 	vscsi->vdev = vdev;
 	vdev->priv = shost;
 
-	err = virtscsi_init(vdev, vscsi, num_targets);
+	err = virtscsi_init(vdev, vscsi);
 	if (err)
 		goto virtscsi_init_failed;
 
@@ -735,7 +714,7 @@ static int virtscsi_restore(struct virtio_device *vdev)
 	struct Scsi_Host *sh = virtio_scsi_host(vdev);
 	struct virtio_scsi *vscsi = shost_priv(sh);
 
-	return virtscsi_init(vdev, vscsi, sh->max_id);
+	return virtscsi_init(vdev, vscsi);
 }
 #endif