virtio_scsi: use cmd_size

Taken almost entirely from Nicholas Bellinger's scsi-mq conversion.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index dd7c998221b3..e016e2ac38df 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -133,6 +133,15 @@ struct scsi_cmnd {
         unsigned char tag;      /* SCSI-II queued command tag */
 };
 
+/*
+ * Return the driver private allocation behind the command.
+ * Only works if cmd_size is set in the host template.
+ */
+static inline void *scsi_cmd_priv(struct scsi_cmnd *cmd)
+{
+        return cmd + 1;
+}
+
 /* make sure not to use it with REQ_TYPE_BLOCK_PC commands */
 static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
 {