IB/iser: Remove redundant locking from iser scsi command response flow

Currently the iSER receive completion flow takes the session lock
twice.  Optimize it to avoid the first one by letting
iser_task_rdma_finalize() be called only from the cleanup_task
callback invoked by iscsi_free_task, thus reducing the contention on
the session lock between the scsi command submission to the scsi
command completion flows.
Signed-off-by: Or Gerlitz <ogerlitz@voltaire.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/iser/iser_initiator.c

@@ -440,10 +440,7 @@ void iser_rcv_completion(struct iser_rx_desc *rx_desc,
 			 struct iser_conn *ib_conn)
 {
 	struct iscsi_iser_conn *conn = ib_conn->iser_conn;
-	struct iscsi_task *task;
-	struct iscsi_iser_task *iser_task;
 	struct iscsi_hdr *hdr;
-	unsigned char opcode;
 	u64 rx_dma;
 	int rx_buflen, outstanding, count, err;
 
@@ -464,28 +461,6 @@ void iser_rcv_completion(struct iser_rx_desc *rx_desc,
 	iser_dbg("op 0x%x itt 0x%x dlen %d\n", hdr->opcode,
 			hdr->itt, (int)(rx_xfer_len - ISER_HEADERS_LEN));
 
-	opcode = hdr->opcode & ISCSI_OPCODE_MASK;
-
-	if (opcode == ISCSI_OP_SCSI_CMD_RSP) {
-		spin_lock(&conn->iscsi_conn->session->lock);
-		task = iscsi_itt_to_ctask(conn->iscsi_conn, hdr->itt);
-		if (task)
-			__iscsi_get_task(task);
-		spin_unlock(&conn->iscsi_conn->session->lock);
-
-		if (!task)
-			iser_err("itt can't be matched to task!!! "
-				 "conn %p opcode %d itt %d\n",
-				 conn->iscsi_conn, opcode, hdr->itt);
-		else {
-			iser_task = task->dd_data;
-			iser_dbg("itt %d task %p\n",hdr->itt, task);
-			iser_task->status = ISER_TASK_STATUS_COMPLETED;
-			iser_task_rdma_finalize(iser_task);
-			iscsi_put_task(task);
-		}
-	}
-
 	iscsi_iser_recv(conn->iscsi_conn, hdr,
 		rx_desc->data, rx_xfer_len - ISER_HEADERS_LEN);