iser-target: Match FRMR descriptors to available session tags

This patch changes isert_conn_create_fastreg_pool() to follow
logic in iscsi_target_locate_portal() for determining how many
FRMR descriptors to allocate based upon the number of possible
per-session command slots that are available.

This addresses an OOPs in isert_reg_rdma() where due to the
use of ISCSI_DEF_XMIT_CMDS_MAX could end up returning a bogus
fast_reg_descriptor when the number of active tags exceeded
the original hardcoded max.

Note this also includes moving isert_conn_create_fastreg_pool()
from isert_connect_request() to isert_put_login_tx() before
posting the final Login Response PDU in order to determine the
se_nacl->queue_depth (eg: number of tags) per session the target
will be enforcing.

v2 changes:
  - Move isert_conn->conn_fr_pool list_head init into
    isert_conn_request()
v3 changes:
  - Drop unnecessary list_empty() check in isert_reg_rdma()
    (Sagi)

Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: <stable@vger.kernel.org> #3.12+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/isert/ib_isert.c

@@ -508,11 +508,18 @@ isert_conn_create_fastreg_pool(struct isert_conn *isert_conn, u8 pi_support)
 {
 	struct fast_reg_descriptor *fr_desc;
 	struct isert_device *device = isert_conn->conn_device;
-	int i, ret;
+	struct se_session *se_sess = isert_conn->conn->sess->se_sess;
+	struct se_node_acl *se_nacl = se_sess->se_node_acl;
+	int i, ret, tag_num;
+	/*
+	 * Setup the number of FRMRs based upon the number of tags
+	 * available to session in iscsi_target_locate_portal().
+	 */
+	tag_num = max_t(u32, ISCSIT_MIN_TAGS, se_nacl->queue_depth);
+	tag_num = (tag_num * 2) + ISCSIT_EXTRA_TAGS;
 
-	INIT_LIST_HEAD(&isert_conn->conn_fr_pool);
 	isert_conn->conn_fr_pool_size = 0;
-	for (i = 0; i < ISCSI_DEF_XMIT_CMDS_MAX; i++) {
+	for (i = 0; i < tag_num; i++) {
 		fr_desc = kzalloc(sizeof(*fr_desc), GFP_KERNEL);
 		if (!fr_desc) {
 			pr_err("Failed to allocate fast_reg descriptor\n");
@@ -572,6 +579,7 @@ isert_connect_request(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
 	kref_get(&isert_conn->conn_kref);
 	mutex_init(&isert_conn->conn_mutex);
 	spin_lock_init(&isert_conn->conn_lock);
+	INIT_LIST_HEAD(&isert_conn->conn_fr_pool);
 
 	cma_id->context = isert_conn;
 	isert_conn->conn_cm_id = cma_id;
@@ -649,15 +657,6 @@ isert_connect_request(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
 		goto out_mr;
 	}
 
-	if (device->use_fastreg) {
-		ret = isert_conn_create_fastreg_pool(isert_conn, pi_support);
-		if (ret) {
-			pr_err("Conn: %p failed to create fastreg pool\n",
-			       isert_conn);
-			goto out_fastreg;
-		}
-	}
-
 	ret = isert_conn_setup_qp(isert_conn, cma_id, pi_support);
 	if (ret)
 		goto out_conn_dev;
@@ -671,9 +670,6 @@ isert_connect_request(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
 	return 0;
 
 out_conn_dev:
-	if (device->use_fastreg)
-		isert_conn_free_fastreg_pool(isert_conn);
-out_fastreg:
 	ib_dereg_mr(isert_conn->conn_mr);
 out_mr:
 	ib_dealloc_pd(isert_conn->conn_pd);
@@ -1047,6 +1043,18 @@ isert_put_login_tx(struct iscsi_conn *conn, struct iscsi_login *login,
 	}
 	if (!login->login_failed) {
 		if (login->login_complete) {
+			if (isert_conn->conn_device->use_fastreg) {
+				u8 pi_support = login->np->tpg_np->tpg->tpg_attrib.t10_pi;
+
+				ret = isert_conn_create_fastreg_pool(isert_conn,
+								     pi_support);
+				if (ret) {
+					pr_err("Conn: %p failed to create"
+					       " fastreg pool\n", isert_conn);
+					return ret;
+				}
+			}
+
 			ret = isert_alloc_rx_descriptors(isert_conn);
 			if (ret)
 				return ret;