target: Enable READ_STRIP emulation in target_complete_ok_work

This patch enables the use of READ_STRIP software emulation in
target_complete_ok_work() code for I/O READs.

This is useful when the fabric does not support READ_STRIP hardware
offload, but would still like to interact with backend device
that have T10 PI enabled.

v2 changes:
   - Move TARGET_PROT_DIN_STRIP check from target_check_read_strip()
     into target_complete_ok_work() (Sagi)

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Quinn Tran <quinn.tran@qlogic.com>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_transport.c

@@ -1905,6 +1905,21 @@ static void transport_handle_queue_full(
 	schedule_work(&cmd->se_dev->qf_work_queue);
 }
 
+static bool target_check_read_strip(struct se_cmd *cmd)
+{
+	sense_reason_t rc;
+
+	if (!(cmd->se_sess->sup_prot_ops & TARGET_PROT_DIN_STRIP)) {
+		rc = sbc_dif_read_strip(cmd);
+		if (rc) {
+			cmd->pi_err = rc;
+			return true;
+		}
+	}
+
+	return false;
+}
+
 static void target_complete_ok_work(struct work_struct *work)
 {
 	struct se_cmd *cmd = container_of(work, struct se_cmd, work);
@@ -1969,6 +1984,22 @@ static void target_complete_ok_work(struct work_struct *work)
 					cmd->data_length;
 		}
 		spin_unlock(&cmd->se_lun->lun_sep_lock);
+		/*
+		 * Perform READ_STRIP of PI using software emulation when
+		 * backend had PI enabled, if the transport will not be
+		 * performing hardware READ_STRIP offload.
+		 */
+		if (cmd->prot_op == TARGET_PROT_DIN_STRIP &&
+		    target_check_read_strip(cmd)) {
+			ret = transport_send_check_condition_and_sense(cmd,
+						cmd->pi_err, 0);
+			if (ret == -EAGAIN || ret == -ENOMEM)
+				goto queue_full;
+
+			transport_lun_remove_cmd(cmd);
+			transport_cmd_check_stop_to_fabric(cmd);
+			return;
+		}
 
 		trace_target_cmd_complete(cmd);
 		ret = cmd->se_tfo->queue_data_in(cmd);