[PATCH 3.16 028/133] scsi: zfcp: fix payload with full FCP_RSP IU in SCSI trace records

[Ben Hutchings <ben@decadent.org.uk>]

3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Steffen Maier <maier@linux.vnet.ibm.com>

commit 12c3e5754c8022a4f2fd1e9f00d19e99ee0d3cc1 upstream.

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.")
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/s390/scsi/zfcp_dbf.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

--- a/drivers/s390/scsi/zfcp_dbf.c
+++ b/drivers/s390/scsi/zfcp_dbf.c
@@ -571,19 +571,32 @@ void zfcp_dbf_scsi(char *tag, int level,
 
 	if (fsf) {
 		rec->fsf_req_id = fsf->req_id;
+		rec->pl_len = FCP_RESP_WITH_EXT;
 		fcp_rsp = (struct fcp_resp_with_ext *)
 				&(fsf->qtcb->bottom.io.fcp_rsp);
+		/* mandatory parts of FCP_RSP IU in this SCSI record */
 		memcpy(&rec->fcp_rsp, fcp_rsp, FCP_RESP_WITH_EXT);
 		if (fcp_rsp->resp.fr_flags & FCP_RSP_LEN_VAL) {
 			fcp_rsp_info = (struct fcp_resp_rsp_info *) &fcp_rsp[1];
 			rec->fcp_rsp_info = fcp_rsp_info->rsp_code;
+			rec->pl_len += be32_to_cpu(fcp_rsp->ext.fr_rsp_len);
 		}
 		if (fcp_rsp->resp.fr_flags & FCP_SNS_LEN_VAL) {
-			rec->pl_len = min((u16)SCSI_SENSE_BUFFERSIZE,
-					  (u16)ZFCP_DBF_PAY_MAX_REC);
-			zfcp_dbf_pl_write(dbf, sc->sense_buffer, rec->pl_len,
-					  "fcp_sns", fsf->req_id);
+			rec->pl_len += be32_to_cpu(fcp_rsp->ext.fr_sns_len);
 		}
+		/* complete FCP_RSP IU in associated PAYload record
+		 * but only if there are optional parts
+		 */
+		if (fcp_rsp->resp.fr_flags != 0)
+			zfcp_dbf_pl_write(
+				dbf, fcp_rsp,
+				/* at least one full PAY record
+				 * but not beyond hardware response field
+				 */
+				min_t(u16, max_t(u16, rec->pl_len,
+						 ZFCP_DBF_PAY_MAX_REC),
+				      FSF_FCP_RSP_SIZE),
+				"fcp_riu", fsf->req_id);
 	}
 
 	debug_event(dbf->scsi, level, rec, sizeof(*rec));