IB/iser: Fix error flow in case of registration failure

During READ/WRITE preparation, in case of failure in memory registration
using iser_reg_mem_fastreg we must unmap previously mapped iser task.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Sergey Gorenko <[e-mail]>
Signed-off-by: Max Gurtovoy <[e-mail]>
Acked-by: Sagi Grimberg <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/ulp/iser/iser_initiator.c

···
 	err = iser_reg_mem_fastreg(iser_task, ISER_DIR_IN, false);
 	if (err) {
 		iser_err("Failed to set up Data-IN RDMA\n");
-		return err;
+		goto out_err;
 	}
 	mem_reg = &iser_task->rdma_reg[ISER_DIR_IN];
 
···
 		 (unsigned long long)mem_reg->sge.addr);
 
 	return 0;
+
+out_err:
+	iser_dma_unmap_task_data(iser_task, ISER_DIR_IN, DMA_FROM_DEVICE);
+	return err;
 }
 
 /* Register user buffer memory and initialize passive rdma
···
 
 	err = iser_reg_mem_fastreg(iser_task, ISER_DIR_OUT,
 				   buf_out->data_len == imm_sz);
-	if (err != 0) {
+	if (err) {
 		iser_err("Failed to register write cmd RDMA mem\n");
-		return err;
+		goto out_err;
 	}
 
 	mem_reg = &iser_task->rdma_reg[ISER_DIR_OUT];
···
 	}
 
 	return 0;
+
+out_err:
+	iser_dma_unmap_task_data(iser_task, ISER_DIR_OUT, DMA_TO_DEVICE);
+	return err;
 }
 
 /* creates a new tx descriptor and adds header regd buffer */