target/transport: Always initialize bidi fields in se_cmd

Fields t_bidi_data_sg and t_bidi_data_nents are set only in the presence
of BIDI commands. This means that the underlying code (for example TCMU)
cannot inspect them when the SCSI command is not a BIDI one.

Ensure the code always initializes these fields with the given values,
even when the SCSI command is not a BIDI one. Set t_bidi_data_sg to
sgl_bidi (which should be NULL for non-BIDI commands) and
t_bidi_data_nents to sgl_bidi_count (which should be 0 for non-BIDI
commands). This allows the underlying code to use these fields
unconditionally.

Signed-off-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: Vangelis Koukis <vkoukis@arrikto.com>
Reviewed-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_transport.c

@@ -1353,11 +1353,9 @@ transport_generic_map_mem_to_cmd(struct se_cmd *cmd, struct scatterlist *sgl,
 
 	cmd->t_data_sg = sgl;
 	cmd->t_data_nents = sgl_count;
-
-	if (sgl_bidi && sgl_bidi_count) {
 	cmd->t_bidi_data_sg = sgl_bidi;
 	cmd->t_bidi_data_nents = sgl_bidi_count;
-	}
+
 	cmd->se_cmd_flags |= SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC;
 	return 0;
 }