target: Set additional sense length field in sense data

The target code was not setting the additional sense length field in the
sense data it returned, which meant that at least the Linux stack
ignored the ASC/ASCQ fields.  For example, without this patch, on a
tcm_loop device:

    # sg_raw -v /dev/sda 2 0 0 0 0 0

gives

        cdb to send: 02 00 00 00 00 00
    SCSI Status: Check Condition

    Sense Information:
     Fixed format, current;  Sense key: Illegal Request
      Raw sense data (in hex):
            70 00 05 00 00 00 00 00

while after the patch we correctly get the following (which matches what
a regular disk returns):

        cdb to send: 02 00 00 00 00 00
    SCSI Status: Check Condition

    Sense Information:
     Fixed format, current;  Sense key: Illegal Request
     Additional sense: Invalid command operation code
     Raw sense data (in hex):
            70 00 05 00 00 00 00 0a  00 00 00 00 20 00 00 00
            00 00

Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: stable@kernel.org
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 b5fdacc..d3ddd13 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -4398,6 +4398,7 @@
 	case TCM_NON_EXISTENT_LUN:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ILLEGAL REQUEST */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ILLEGAL_REQUEST;
 		/* LOGICAL UNIT NOT SUPPORTED */
@@ -4407,6 +4408,7 @@
 	case TCM_SECTOR_COUNT_TOO_MANY:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ILLEGAL REQUEST */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ILLEGAL_REQUEST;
 		/* INVALID COMMAND OPERATION CODE */
@@ -4415,6 +4417,7 @@
 	case TCM_UNKNOWN_MODE_PAGE:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ILLEGAL REQUEST */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ILLEGAL_REQUEST;
 		/* INVALID FIELD IN CDB */
@@ -4423,6 +4426,7 @@
 	case TCM_CHECK_CONDITION_ABORT_CMD:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ABORTED COMMAND */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ABORTED_COMMAND;
 		/* BUS DEVICE RESET FUNCTION OCCURRED */
@@ -4432,6 +4436,7 @@
 	case TCM_INCORRECT_AMOUNT_OF_DATA:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ABORTED COMMAND */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ABORTED_COMMAND;
 		/* WRITE ERROR */
@@ -4442,6 +4447,7 @@
 	case TCM_INVALID_CDB_FIELD:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ABORTED COMMAND */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ABORTED_COMMAND;
 		/* INVALID FIELD IN CDB */
@@ -4450,6 +4456,7 @@
 	case TCM_INVALID_PARAMETER_LIST:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ABORTED COMMAND */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ABORTED_COMMAND;
 		/* INVALID FIELD IN PARAMETER LIST */
@@ -4458,6 +4465,7 @@
 	case TCM_UNEXPECTED_UNSOLICITED_DATA:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ABORTED COMMAND */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ABORTED_COMMAND;
 		/* WRITE ERROR */
@@ -4468,6 +4476,7 @@
 	case TCM_SERVICE_CRC_ERROR:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ABORTED COMMAND */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ABORTED_COMMAND;
 		/* PROTOCOL SERVICE CRC ERROR */
@@ -4478,6 +4487,7 @@
 	case TCM_SNACK_REJECTED:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ABORTED COMMAND */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ABORTED_COMMAND;
 		/* READ ERROR */
@@ -4488,6 +4498,7 @@
 	case TCM_WRITE_PROTECTED:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* DATA PROTECT */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = DATA_PROTECT;
 		/* WRITE PROTECTED */
@@ -4496,6 +4507,7 @@
 	case TCM_CHECK_CONDITION_UNIT_ATTENTION:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* UNIT ATTENTION */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = UNIT_ATTENTION;
 		core_scsi3_ua_for_check_condition(cmd, &asc, &ascq);
@@ -4505,6 +4517,7 @@
 	case TCM_CHECK_CONDITION_NOT_READY:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* Not Ready */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = NOT_READY;
 		transport_get_sense_codes(cmd, &asc, &ascq);
@@ -4515,6 +4528,7 @@
 	default:
 		/* CURRENT ERROR */
 		buffer[offset] = 0x70;
+		buffer[offset+SPC_ADD_SENSE_LEN_OFFSET] = 10;
 		/* ILLEGAL REQUEST */
 		buffer[offset+SPC_SENSE_KEY_OFFSET] = ILLEGAL_REQUEST;
 		/* LOGICAL UNIT COMMUNICATION FAILURE */
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index a74cb2b..daf532b 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -35,6 +35,7 @@
 #define TRANSPORT_SENSE_BUFFER			SCSI_SENSE_BUFFERSIZE
 /* Used by transport_send_check_condition_and_sense() */
 #define SPC_SENSE_KEY_OFFSET			2
+#define SPC_ADD_SENSE_LEN_OFFSET		7
 #define SPC_ASC_KEY_OFFSET			12
 #define SPC_ASCQ_KEY_OFFSET			13
 #define TRANSPORT_IQN_LEN			224