IB/srpt: Remove use of transport_do_task_sg_chain()

With the modern target core, se_cmd->t_data_sg already points to a
sglist that covers the whole command.  So task_sg chaining is needless
overhead and obfuscation -- instead of splicing the split up task
sglists back into one list, we can just use the original list directly.
Signed-off-by: Roland Dreier <roland@purestorage.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/srpt/ib_srpt.c

@@ -1099,9 +1099,8 @@ static int srpt_map_sg_to_ib_sge(struct srpt_rdma_ch *ch,
 	dir = cmd->data_direction;
 	BUG_ON(dir == DMA_NONE);
 
-	transport_do_task_sg_chain(cmd);
-	ioctx->sg = sg = sg_orig = cmd->t_tasks_sg_chained;
-	ioctx->sg_cnt = sg_cnt = cmd->t_tasks_sg_chained_no;
+	ioctx->sg = sg = sg_orig = cmd->t_data_sg;
+	ioctx->sg_cnt = sg_cnt = cmd->t_data_nents;
 
 	count = ib_dma_map_sg(ch->sport->sdev->device, sg, sg_cnt,
 			      opposite_dma_dir(dir));
@@ -4003,9 +4002,6 @@ static int __init srpt_init_module(void)
 
 	srpt_target->tf_ops = srpt_template;
 
-	/* Enable SG chaining */
-	srpt_target->tf_ops.task_sg_chaining = true;
-
 	/*
 	 * Set up default attribute lists.
 	 */