scsi: zfcp: fix payload with full FCP_RSP IU in SCSI trace records

scsi: zfcp: fix payload with full FCP_RSP IU in SCSI trace records

If the FCP_RSP UI has optional parts (FCP_SNS_INFO or FCP_RSP_INFO) and
thus does not fit into the fsp_rsp field built into a SCSI trace record,
trace the full FCP_RSP UI with all optional parts as payload record
instead of just FCP_SNS_INFO as payload and
a 1 byte RSP_INFO_CODE part of FCP_RSP_INFO built into the SCSI record.

That way we would also get the full FCP_SNS_INFO in case a
target would ever send more than
min(SCSI_SENSE_BUFFERSIZE==96, ZFCP_DBF_PAY_MAX_REC==256)==96.

The mandatory part of FCP_RSP IU is only 24 bytes.
PAYload costs at least one full PAY record of 256 bytes anyway.
We cap to the hardware response size which is only FSF_FCP_RSP_SIZE==128.
So we can just put the whole FCP_RSP IU with any optional parts into
PAYload similarly as we do for SAN PAY since v4.9 commit aceeffbb59bb
("zfcp: trace full payload of all SAN records (req,resp,iels)").
This does not cause any additional trace records wasting memory.

Decoded trace records were confusing because they showed a hard-coded
sense data length of 96 even if the FCP_RSP_IU field FCP_SNS_LEN showed
actually less.

Since the same commit, we set pl_len for SAN traces to the full length of a
request/response even if we cap the corresponding trace.
In contrast, here for SCSI traces we set pl_len to the pre-computed
length of FCP_RSP IU considering SNS_LEN or RSP_LEN if valid.
Nonetheless we trace a hardcoded payload of length FSF_FCP_RSP_SIZE==128
if there were optional parts.
This makes it easier for the zfcpdbf tool to format only the relevant
part of the long FCP_RSP UI buffer. And any trailing information is still
available in the payload trace record just in case.

Rename the payload record tag from "fcp_sns" to "fcp_riu" to make the new
content explicit to zfcpdbf which can then pick a suitable field name such
as "FCP rsp IU all:" instead of "Sense info :"
Also, the same zfcpdbf can still be backwards compatible with "fcp_sns".

Old example trace record before this fix, formatted with the tool zfcpdbf
from s390-tools:

Timestamp      : ...
Area           : SCSI
Subarea        : 00
Level          : 3
Exception      : -
CPU id         : ..
Caller         : 0x...
Record id      : 1
Tag            : rsl_err
Request id     : 0x<request_id>
SCSI ID        : 0x...
SCSI LUN       : 0x...
SCSI result    : 0x00000002
SCSI retries   : 0x00
SCSI allowed   : 0x05
SCSI scribble  : 0x<request_id>
SCSI opcode    : 00000000 00000000 00000000 00000000
FCP rsp inf cod: 0x00
FCP rsp IU     : 00000000 00000000 00000202 00000000
                                       ^^==FCP_SNS_LEN_VALID
                 00000020 00000000
                 ^^^^^^^^==FCP_SNS_LEN==32
Sense len      : 96 <==min(SCSI_SENSE_BUFFERSIZE,ZFCP_DBF_PAY_MAX_REC)
Sense info     : 70000600 00000018 00000000 29000000
                 00000400 00000000 00000000 00000000
                 00000000 00000000 00000000 00000000<==superfluous
                 00000000 00000000 00000000 00000000<==superfluous
                 00000000 00000000 00000000 00000000<==superfluous
                 00000000 00000000 00000000 00000000<==superfluous

New example trace records with this fix:

Timestamp      : ...
Area           : SCSI
Subarea        : 00
Level          : 3
Exception      : -
CPU ID         : ..
Caller         : 0x...
Record ID      : 1
Tag            : rsl_err
Request ID     : 0x<request_id>
SCSI ID        : 0x...
SCSI LUN       : 0x...
SCSI result    : 0x00000002
SCSI retries   : 0x00
SCSI allowed   : 0x03
SCSI scribble  : 0x<request_id>
SCSI opcode    : a30c0112 00000000 02000000 00000000
FCP rsp inf cod: 0x00
FCP rsp IU     : 00000000 00000000 00000a02 00000200
                 00000020 00000000
FCP rsp IU len : 56
FCP rsp IU all : 00000000 00000000 00000a02 00000200
                                       ^^=FCP_RESID_UNDER|FCP_SNS_LEN_VALID
                 00000020 00000000 70000500 00000018
                 ^^^^^^^^==FCP_SNS_LEN
                                   ^^^^^^^^^^^^^^^^^
                 00000000 240000cb 00011100 00000000
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                 00000000 00000000
                 ^^^^^^^^^^^^^^^^^==FCP_SNS_INFO

Timestamp      : ...
Area           : SCSI
Subarea        : 00
Level          : 1
Exception      : -
CPU ID         : ..
Caller         : 0x...
Record ID      : 1
Tag            : lr_okay
Request ID     : 0x<request_id>
SCSI ID        : 0x...
SCSI LUN       : 0x...
SCSI result    : 0x00000000
SCSI retries   : 0x00
SCSI allowed   : 0x05
SCSI scribble  : 0x<request_id>
SCSI opcode    : <CDB of unrelated SCSI command passed to eh handler>
FCP rsp inf cod: 0x00
FCP rsp IU     : 00000000 00000000 00000100 00000000
                 00000000 00000008
FCP rsp IU len : 32
FCP rsp IU all : 00000000 00000000 00000100 00000000
                                       ^^==FCP_RSP_LEN_VALID
                 00000000 00000008 00000000 00000000
                          ^^^^^^^^==FCP_RSP_LEN
                                   ^^^^^^^^^^^^^^^^^==FCP_RSP_INFO

Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Fixes: 250a1352b95e ("[SCSI] zfcp: Redesign of the debug tracing for SCSI records.")
Cc: <stable@vger.kernel.org> #2.6.38+
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>