[SCSI] IB/iser: Add Discovery support

To run discovery over iSER we need to advertize the CAP_TEXT_NEGO capability
towards user space. Also need to make sure the login RX buffer is posted when
SendTargets TEXT PDUs are sent. For that end, we use a setting of the
ISCSI_PARAM_DISCOVERY_SESS iscsi param as an indication that this is
discovery session.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/infiniband/ulp/iser/iscsi_iser.c

@@ -672,6 +672,7 @@ static umode_t iser_attr_is_visible(int param_type, int param)
 		case ISCSI_PARAM_TGT_RESET_TMO:
 		case ISCSI_PARAM_IFACE_NAME:
 		case ISCSI_PARAM_INITIATOR_NAME:
+		case ISCSI_PARAM_DISCOVERY_SESS:
 			return S_IRUGO;
 		default:
 			return 0;
@@ -701,7 +702,7 @@ static struct scsi_host_template iscsi_iser_sht = {
 static struct iscsi_transport iscsi_iser_transport = {
 	.owner                  = THIS_MODULE,
 	.name                   = "iser",
-	.caps                   = CAP_RECOVERY_L0 | CAP_MULTI_R2T,
+	.caps                   = CAP_RECOVERY_L0 | CAP_MULTI_R2T | CAP_TEXT_NEGO,
 	/* session management */
 	.create_session         = iscsi_iser_session_create,
 	.destroy_session        = iscsi_iser_session_destroy,

drivers/infiniband/ulp/iser/iser_initiator.c

@@ -234,6 +234,7 @@ void iser_free_rx_descriptors(struct iser_conn *ib_conn)
 static int iser_post_rx_bufs(struct iscsi_conn *conn, struct iscsi_hdr *req)
 {
 	struct iscsi_iser_conn *iser_conn = conn->dd_data;
+	struct iscsi_session *session = conn->session;
 
 	iser_dbg("req op %x flags %x\n", req->opcode, req->flags);
 	/* check if this is the last login - going to full feature phase */
@@ -248,7 +249,13 @@ static int iser_post_rx_bufs(struct iscsi_conn *conn, struct iscsi_hdr *req)
 	WARN_ON(iser_conn->ib_conn->post_recv_buf_count != 1);
 	WARN_ON(atomic_read(&iser_conn->ib_conn->post_send_buf_count) != 0);
 
-	iser_dbg("Initially post: %d\n", ISER_MIN_POSTED_RX);
+	if (session->discovery_sess) {
+		iser_info("Discovery session, re-using login RX buffer\n");
+		return 0;
+	} else
+		iser_info("Normal session, posting batch of RX %d buffers\n",
+			  ISER_MIN_POSTED_RX);
+
 	/* Initial post receive buffers */
 	if (iser_post_recvm(iser_conn->ib_conn, ISER_MIN_POSTED_RX))
 		return -ENOMEM;
@@ -425,6 +432,8 @@ int iser_send_control(struct iscsi_conn *conn,
 	}
 
 	if (task == conn->login_task) {
+		iser_dbg("op %x dsl %lx, posting login rx buffer\n",
+			 task->hdr->opcode, data_seg_len);
 		err = iser_post_recvl(iser_conn->ib_conn);
 		if (err)
 			goto send_control_error;

drivers/scsi/libiscsi.c

@@ -3170,6 +3170,7 @@ int iscsi_set_param(struct iscsi_cls_conn *cls_conn,
 {
 	struct iscsi_conn *conn = cls_conn->dd_data;
 	struct iscsi_session *session = conn->session;
+	int val;
 
 	switch(param) {
 	case ISCSI_PARAM_FAST_ABORT:
@@ -3264,6 +3265,10 @@ int iscsi_set_param(struct iscsi_cls_conn *cls_conn,
 	case ISCSI_PARAM_DISCOVERY_PARENT_TYPE:
 		return iscsi_switch_str_param(&session->discovery_parent_type,
 					      buf);
+	case ISCSI_PARAM_DISCOVERY_SESS:
+		sscanf(buf, "%d", &val);
+		session->discovery_sess = !!val;
+		break;
 	default:
 		return -ENOSYS;
 	}