tcm_fc: 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>
Acked-by: Kiran Patil <Kiran.patil@intel.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/tcm_fc/tfc_cmd.c

@@ -215,20 +215,10 @@ int ft_write_pending(struct se_cmd *se_cmd)
 		 */
 		if ((ep->xid <= lport->lro_xid) &&
 		    (fh->fh_r_ctl == FC_RCTL_DD_DATA_DESC)) {
-			if (se_cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB) {
+			if ((se_cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB) &&
-				/*
+			    lport->tt.ddp_target(lport, ep->xid,
-				 * cmd may have been broken up into multiple
+						 se_cmd->t_data_sg,
-				 * tasks. Link their sgs together so we can
+						 se_cmd->t_data_nents))
-				 * operate on them all at once.
-				 */
-				transport_do_task_sg_chain(se_cmd);
-				cmd->sg = se_cmd->t_tasks_sg_chained;
-				cmd->sg_cnt =
-					se_cmd->t_tasks_sg_chained_no;
-			}
-			if (cmd->sg && lport->tt.ddp_target(lport, ep->xid,
-							    cmd->sg,
-							    cmd->sg_cnt))
 				cmd->was_ddp_setup = 1;
 		}
 	}

drivers/target/tcm_fc/tfc_conf.c

@@ -576,9 +576,6 @@ int ft_register_configfs(void)
 	}
 	fabric->tf_ops = ft_fabric_ops;
 
-	/* Allowing support for task_sg_chaining */
-	fabric->tf_ops.task_sg_chaining = 1;
-
 	/*
 	 * Setup default attribute lists for various fabric->tf_cit_tmpl
 	 */

drivers/target/tcm_fc/tfc_io.c

@@ -228,7 +228,7 @@ void ft_recv_write_data(struct ft_cmd *cmd, struct fc_frame *fp)
 				"payload, Frame will be dropped if"
 				"'Sequence Initiative' bit in f_ctl is"
 				"not set\n", __func__, ep->xid, f_ctl,
-				cmd->sg, cmd->sg_cnt);
+				se_cmd->t_data_sg, se_cmd->t_data_nents);
 		/*
 		 * Invalidate HW DDP context if it was setup for respective
 		 * command. Invalidation of HW DDP context is requited in both