IB/iser: DMA unmap TX bufs used for iSCSI/iSER headers

The current driver never does DMA unmapping on these buffers.  Fix that
by adding DMA unmapping to the task cleanup callback, and DMA mapping to
the task init function (drop the headers_initialized micro-optimization).
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/iser/iscsi_iser.c

@@ -151,7 +151,6 @@ int iser_initialize_task_headers(struct iscsi_task *task,
 	tx_desc->tx_sg[0].length = ISER_HEADERS_LEN;
 	tx_desc->tx_sg[0].lkey   = device->mr->lkey;
 
-	iser_task->headers_initialized	= 1;
 	iser_task->iser_conn		= iser_conn;
 	return 0;
 }
@@ -166,7 +165,6 @@ iscsi_iser_task_init(struct iscsi_task *task)
 {
 	struct iscsi_iser_task *iser_task = task->dd_data;
 
-	if (!iser_task->headers_initialized)
 	if (iser_initialize_task_headers(task, &iser_task->desc))
 			return -ENOMEM;
 
@@ -278,6 +276,13 @@ iscsi_iser_task_xmit(struct iscsi_task *task)
 static void iscsi_iser_cleanup_task(struct iscsi_task *task)
 {
 	struct iscsi_iser_task *iser_task = task->dd_data;
+	struct iser_tx_desc	*tx_desc = &iser_task->desc;
+
+	struct iscsi_iser_conn *iser_conn = task->conn->dd_data;
+	struct iser_device     *device    = iser_conn->ib_conn->device;
+
+	ib_dma_unmap_single(device->ib_device,
+		tx_desc->dma_addr, ISER_HEADERS_LEN, DMA_TO_DEVICE);
 
 	/* mgmt tasks do not need special cleanup */
 	if (!task->sc)

drivers/infiniband/ulp/iser/iscsi_iser.h

@@ -278,7 +278,6 @@ struct iscsi_iser_task {
 	struct iser_regd_buf         rdma_regd[ISER_DIRS_NUM];/* regd rdma buf */
 	struct iser_data_buf         data[ISER_DIRS_NUM];     /* orig. data des*/
 	struct iser_data_buf         data_copy[ISER_DIRS_NUM];/* contig. copy  */
-	int                          headers_initialized;
 };
 
 struct iser_page_vec {