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>
diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.c b/drivers/infiniband/ulp/iser/iscsi_iser.c
index 84e8c29..c42b8f3 100644
--- a/drivers/infiniband/ulp/iser/iscsi_iser.c
+++ b/drivers/infiniband/ulp/iser/iscsi_iser.c
@@ -151,7 +151,6 @@
 	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;
 }
@@ -166,8 +165,7 @@
 {
 	struct iscsi_iser_task *iser_task = task->dd_data;
 
-	if (!iser_task->headers_initialized)
-		if (iser_initialize_task_headers(task, &iser_task->desc))
+	if (iser_initialize_task_headers(task, &iser_task->desc))
 			return -ENOMEM;
 
 	/* mgmt task */
@@ -278,6 +276,13 @@
 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)