IB/iser: Fix possible bogus DMA unmapping

If iser_initialize_task_headers() routine failed before
dma mapping, we should not attempt to unmap in cleanup_task().

Fixes: 7414dde0 (IB/iser: Fix race between iser connection ...)
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/ulp/iser/iscsi_iser.c

@@ -200,6 +200,7 @@ iser_initialize_task_headers(struct iscsi_task *task,
 		goto out;
 	}
 
+	tx_desc->mapped = true;
 	tx_desc->dma_addr = dma_addr;
 	tx_desc->tx_sg[0].addr   = tx_desc->dma_addr;
 	tx_desc->tx_sg[0].length = ISER_HEADERS_LEN;
@@ -367,8 +368,11 @@ static void iscsi_iser_cleanup_task(struct iscsi_task *task)
 	if (!device)
 		return;
 
-	ib_dma_unmap_single(device->ib_device,
-		tx_desc->dma_addr, ISER_HEADERS_LEN, DMA_TO_DEVICE);
+	if (likely(tx_desc->mapped)) {
+		ib_dma_unmap_single(device->ib_device, tx_desc->dma_addr,
+				    ISER_HEADERS_LEN, DMA_TO_DEVICE);
+		tx_desc->mapped = false;
+	}
 
 	/* mgmt tasks do not need special cleanup */
 	if (!task->sc)

drivers/infiniband/ulp/iser/iscsi_iser.h

@@ -270,6 +270,7 @@ enum iser_desc_type {
  *                 sg[1] optionally points to either of immediate data
  *                 unsolicited data-out or control
  * @num_sge:       number sges used on this TX task
+ * @mapped:        Is the task header mapped
  */
 struct iser_tx_desc {
 	struct iser_hdr              iser_header;
@@ -278,6 +279,7 @@ struct iser_tx_desc {
 	u64		             dma_addr;
 	struct ib_sge		     tx_sg[2];
 	int                          num_sge;
+	bool			     mapped;
 };
 
 #define ISER_RX_PAD_SIZE	(256 - (ISER_RX_PAYLOAD_SIZE + \