iser-target: Match FRMR descriptors to available session tags
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 <380ce2a82d3d08e67ab163b51dc6d30288ad3f13@mellanox.com>
Cc: Or Gerlitz <de1b678a59344538ef9f2ddb34a5f9486544e2f9@mellanox.com>
Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org> #3.12+
Signed-off-by: Nicholas Bellinger <978acd1567d5598152161fdf8bf3ca568f950c9b@linux-iscsi.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs