vhost scsi: fix lun reset completion handling

vhost scsi owns the scsi se_cmd but lio frees the se_cmd->se_tmr
before calling release_cmd, so while with normal cmd completion we
can access the se_cmd from the vhost work, we can't do the same with
se_cmd->se_tmr. This has us copy the tmf response in
vhost_scsi_queue_tm_rsp to our internal vhost-scsi tmf struct for
when it gets sent to the guest from our worker thread.

Fixes: efd838f ("vhost scsi: Add support for LUN resets.")
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/1605887459-3864-1-git-send-email-michael.christie@oracle.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/scsi.c

@@ -220,6 +220,7 @@ struct vhost_scsi_tmf {
 	struct list_head queue_entry;
 
 	struct se_cmd se_cmd;
+	u8 scsi_resp;
 	struct vhost_scsi_inflight *inflight;
 	struct iovec resp_iov;
 	int in_iovs;
@@ -426,6 +427,7 @@ static void vhost_scsi_queue_tm_rsp(struct se_cmd *se_cmd)
 	struct vhost_scsi_tmf *tmf = container_of(se_cmd, struct vhost_scsi_tmf,
 						  se_cmd);
 
+	tmf->scsi_resp = se_cmd->se_tmr_req->response;
 	transport_generic_free_cmd(&tmf->se_cmd, 0);
 }
 
@@ -1183,7 +1185,7 @@ static void vhost_scsi_tmf_resp_work(struct vhost_work *work)
 						  vwork);
 	int resp_code;
 
-	if (tmf->se_cmd.se_tmr_req->response == TMR_FUNCTION_COMPLETE)
+	if (tmf->scsi_resp == TMR_FUNCTION_COMPLETE)
 		resp_code = VIRTIO_SCSI_S_FUNCTION_SUCCEEDED;
 	else
 		resp_code = VIRTIO_SCSI_S_FUNCTION_REJECTED;