diff --git a/doc/scst_user_spec.txt b/doc/scst_user_spec.txt
index 7f1a4aca2..1f4ed23e1 100644
--- a/doc/scst_user_spec.txt
+++ b/doc/scst_user_spec.txt
@@ -850,6 +850,7 @@ struct scst_user_scsi_cmd_reply_parse
 	uint32_t op_flags;
 	int32_t data_len;
 	int32_t bufflen;
+	int32_t out_bufflen;
 },
 
 where:
@@ -857,7 +858,7 @@ where:
  - queue_type - SCSI task attribute (queue type). NOTE! In current
    implementation setting changing this field from the provided value
    affects commands execution only when then produced by iSCSI-SCST
-   target. With al other target drivers, this field is ignored. This is
+   target. With all other target drivers, this field is ignored. This is
    because for them commands queueing is set before parse() called.
 
  - data_direction - command's data flow direction, one of SCST_DATA_*
@@ -866,11 +867,17 @@ where:
  - cdb_len - length of CDB
 
  - op_flags - commands flags, one or more scst_cdb_flags bits, see above.
+   At least SCST_INFO_VALID must be set for correct processing.
+   SCST_IMPLICIT_HQ not implemented (yet) for single stage init target
+   drivers (all, except iSCSI), because custom parse can reorder
+   commands due to multithreaded processing.
 
  - data_len - command's data length
 
  - bufflen - command's buffer length
 
+ - out_bufflen - command's out buffer length (for bidirectional commands)
+
 
 struct scst_user_scsi_cmd_reply_alloc_mem
 {
diff --git a/scst/include/scst_user.h b/scst/include/scst_user.h
index 8b19075bf..53b7584ea 100644
--- a/scst/include/scst_user.h
+++ b/scst/include/scst_user.h
@@ -227,6 +227,7 @@ struct scst_user_scsi_cmd_reply_parse {
 			uint32_t op_flags;
 			int32_t data_len;
 			int32_t bufflen;
+			int32_t out_bufflen;
 		};
 		struct {
 			uint8_t sense_len;
diff --git a/scst/src/dev_handlers/scst_user.c b/scst/src/dev_handlers/scst_user.c
index 2358580c5..1e7d34de7 100644
--- a/scst/src/dev_handlers/scst_user.c
+++ b/scst/src/dev_handlers/scst_user.c
@@ -1272,12 +1272,16 @@ static int dev_user_process_reply_parse(struct scst_user_cmd *ucmd,
 		     (preply->bufflen == 0)))
 		goto out_inval;
 
-	if (unlikely((preply->bufflen < 0) || (preply->data_len < 0)))
+	if (unlikely((preply->bufflen < 0) || (preply->out_bufflen < 0) ||
+		     (preply->data_len < 0)))
 		goto out_inval;
 
 	if (unlikely(preply->cdb_len > cmd->cdb_len))
 		goto out_inval;
 
+	if (!(preply->op_flags & SCST_INFO_VALID))
+		goto out_inval;
+
 	TRACE_DBG("ucmd %p, queue_type %x, data_direction, %x, bufflen %d, "
 		"data_len %d, pbuf %llx, cdb_len %d, op_flags %x", ucmd,
 		preply->queue_type, preply->data_direction, preply->bufflen,
@@ -1287,11 +1291,11 @@ static int dev_user_process_reply_parse(struct scst_user_cmd *ucmd,
 	cmd->queue_type = preply->queue_type;
 	cmd->data_direction = preply->data_direction;
 	cmd->bufflen = preply->bufflen;
+	cmd->out_bufflen = preply->out_bufflen;
 	cmd->data_len = preply->data_len;
 	if (preply->cdb_len > 0)
 		cmd->cdb_len = preply->cdb_len;
-	if (preply->op_flags & SCST_INFO_VALID)
-		cmd->op_flags = preply->op_flags;
+	cmd->op_flags = preply->op_flags;
 
 out_process:
 	scst_post_parse(cmd);
diff --git a/scst/src/scst_targ.c b/scst/src/scst_targ.c
index a56e98618..319ea0bda 100644
--- a/scst/src/scst_targ.c
+++ b/scst/src/scst_targ.c
@@ -3845,8 +3845,15 @@ static int __scst_init_cmd(struct scst_cmd *cmd)
 		if (unlikely(failure))
 			goto out_busy;
 
-		if (unlikely(scst_pre_parse(cmd) != 0))
-			goto out;
+		/*
+		 * SCST_IMPLICIT_HQ for unknown commands not implemented for
+		 * case when set_sn_on_restart_cmd not set, because custom parse
+		 * can reorder commands due to multithreaded processing. To
+		 * implement it we need to implement all unknown commands as
+		 * ORDERED in the beginning and post parse reprocess of
+		 * queue_type to change it if needed. ToDo.
+		 */
+		scst_pre_parse(cmd);
 
 		if (!cmd->set_sn_on_restart_cmd)
 			scst_cmd_set_sn(cmd);
diff --git a/usr/fileio/common.c b/usr/fileio/common.c
index e8199b5bd..17dfff0bf 100644
--- a/usr/fileio/common.c
+++ b/usr/fileio/common.c
@@ -192,8 +192,18 @@ static int do_parse(struct vdisk_cmd *vcmd)
 	reply->data_direction = cmd->expected_data_direction;
 	reply->data_len = cmd->expected_transfer_len;
 	reply->bufflen = cmd->expected_transfer_len;
+	reply->out_bufflen = cmd->expected_out_transfer_len;
 	reply->cdb_len = cmd->cdb_len;
-	reply->op_flags = reply->op_flags;
+
+	if (cmd->op_flags & SCST_INFO_VALID)
+		reply->op_flags = cmd->op_flags;
+	else {
+		TRACE_DBG_SPECIAL("Extra parse (op %x)", cmd->cdb[0]);
+
+		if (reply->data_direction & SCST_DATA_WRITE)
+			reply->op_flags |= SCST_WRITE_MEDIUM;
+		reply->op_flags |= SCST_INFO_VALID;
+	}
 
 out:
 	TRACE_EXIT_RES(res);