target: Make EXTENDED_COPY 0xe4 failure return COPY TARGET DEVICE NOT REACHABLE

This patch addresses a bug where EXTENDED_COPY across multiple LUNs
results in a CHECK_CONDITION when the source + destination are not
located on the same physical node.

ESX Host environments expect sense COPY_ABORTED w/ COPY TARGET DEVICE
NOT REACHABLE to be returned when this occurs, in order to signal
fallback to local copy method.

As described in section 6.3.3 of spc4r22:

  "If it is not possible to complete processing of a segment because the
   copy manager is unable to establish communications with a copy target
   device, because the copy target device does not respond to INQUIRY,
   or because the data returned in response to INQUIRY indicates
   an unsupported logical unit, then the EXTENDED COPY command shall be
   terminated with CHECK CONDITION status, with the sense key set to
   COPY ABORTED, and the additional sense code set to COPY TARGET DEVICE
   NOT REACHABLE."

Tested on v4.1.y with ESX v5.5u2+ with BlockCopy across multiple nodes.

Reported-by: Nixon Vincent <nixon.vincent@calsoftinc.com>
Tested-by: Nixon Vincent <nixon.vincent@calsoftinc.com>
Cc: Nixon Vincent <nixon.vincent@calsoftinc.com>
Tested-by: Dinesh Israni <ddi@datera.io>
Signed-off-by: Dinesh Israni <ddi@datera.io>
Cc: Dinesh Israni <ddi@datera.io>
Cc: stable@vger.kernel.org # 3.14+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 00ec464..000bc6d 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1706,6 +1706,7 @@
 	case TCM_LOGICAL_BLOCK_GUARD_CHECK_FAILED:
 	case TCM_LOGICAL_BLOCK_APP_TAG_CHECK_FAILED:
 	case TCM_LOGICAL_BLOCK_REF_TAG_CHECK_FAILED:
+	case TCM_COPY_TARGET_DEVICE_NOT_REACHABLE:
 		break;
 	case TCM_OUT_OF_RESOURCES:
 		sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
@@ -2873,6 +2874,12 @@
 		.ascq = 0x03, /* LOGICAL BLOCK REFERENCE TAG CHECK FAILED */
 		.add_sector_info = true,
 	},
+	[TCM_COPY_TARGET_DEVICE_NOT_REACHABLE] = {
+		.key = COPY_ABORTED,
+		.asc = 0x0d,
+		.ascq = 0x02, /* COPY TARGET DEVICE NOT REACHABLE */
+
+	},
 	[TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE] = {
 		/*
 		 * Returning ILLEGAL REQUEST would cause immediate IO errors on