[PATCH 2/3] zfcp: do not trace pure benign residual HBA responses at default level

[Steffen Maier <maier@linux.vnet.ibm.com>]

Since quite a while, Linux issues enough SCSI commands per scsi_device
which successfully return with FCP_RESID_UNDER, FSF_FCP_RSP_AVAILABLE,
and SAM_STAT_GOOD.
This floods the HBA trace area and we cannot see other and
important HBA trace records long enough.

Therefore, do not trace HBA response errors for pure
benign residual under counts at the default trace level.

This excludes benign residual under count combined with other
validity bits set in FCP_RSP_IU, such as FCP_SNS_LEN_VAL.
For all those other cases, we still do want to see
both the HBA record and the corresponding SCSI record by default.

Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Fixes: a54ca0f62f95 ("[SCSI] zfcp: Redesign of the debug tracing for HBA records.")
Cc: <stable@vger.kernel.org> #2.6.37+
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
---
 drivers/s390/scsi/zfcp_dbf.h | 30 ++++++++++++++++++++++++++++--
 drivers/s390/scsi/zfcp_fsf.h |  3 ++-
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_dbf.h b/drivers/s390/scsi/zfcp_dbf.h
index 2d06b5d2c05b..db186d44cfaf 100644
--- a/drivers/s390/scsi/zfcp_dbf.h
+++ b/drivers/s390/scsi/zfcp_dbf.h
@@ -2,7 +2,7 @@
  * zfcp device driver
  * debug feature declarations
  *
- * Copyright IBM Corp. 2008, 2015
+ * Copyright IBM Corp. 2008, 2016
  */
 
 #ifndef ZFCP_DBF_H
@@ -283,6 +283,30 @@ struct zfcp_dbf {
 	struct zfcp_dbf_scsi		scsi_buf;
 };
 
+/**
+ * zfcp_dbf_hba_fsf_resp_suppress - true if we should not trace by default
+ * @req: request that has been completed
+ *
+ * Returns true if FCP response with only benign residual under count.
+ */
+static inline
+bool zfcp_dbf_hba_fsf_resp_suppress(struct zfcp_fsf_req *req)
+{
+	struct fsf_qtcb *qtcb = req->qtcb;
+	u32 fsf_stat = qtcb->header.fsf_status;
+	struct fcp_resp *fcp_rsp;
+	u8 rsp_flags, fr_status;
+
+	if (qtcb->prefix.qtcb_type != FSF_IO_COMMAND)
+		return false; /* not an FCP response */
+	fcp_rsp = (struct fcp_resp *)&qtcb->bottom.io.fcp_rsp;
+	rsp_flags = fcp_rsp->fr_flags;
+	fr_status = fcp_rsp->fr_status;
+	return (fsf_stat == FSF_FCP_RSP_AVAILABLE) &&
+		(rsp_flags == FCP_RESID_UNDER) &&
+		(fr_status == SAM_STAT_GOOD);
+}
+
 static inline
 void zfcp_dbf_hba_fsf_resp(char *tag, int level, struct zfcp_fsf_req *req)
 {
@@ -304,7 +328,9 @@ void zfcp_dbf_hba_fsf_response(struct zfcp_fsf_req *req)
 		zfcp_dbf_hba_fsf_resp("fs_perr", 1, req);
 
 	} else if (qtcb->header.fsf_status != FSF_GOOD) {
-		zfcp_dbf_hba_fsf_resp("fs_ferr", 1, req);
+		zfcp_dbf_hba_fsf_resp("fs_ferr",
+				      zfcp_dbf_hba_fsf_resp_suppress(req)
+				      ? 5 : 1, req);
 
 	} else if ((req->fsf_command == FSF_QTCB_OPEN_PORT_WITH_DID) ||
 		   (req->fsf_command == FSF_QTCB_OPEN_LUN)) {
diff --git a/drivers/s390/scsi/zfcp_fsf.h b/drivers/s390/scsi/zfcp_fsf.h
index be1c04b334c5..ea3c76ac0de1 100644
--- a/drivers/s390/scsi/zfcp_fsf.h
+++ b/drivers/s390/scsi/zfcp_fsf.h
@@ -3,7 +3,7 @@
  *
  * Interface to the FSF support functions.
  *
- * Copyright IBM Corp. 2002, 2015
+ * Copyright IBM Corp. 2002, 2016
  */
 
 #ifndef FSF_H
@@ -78,6 +78,7 @@
 #define FSF_APP_TAG_CHECK_FAILURE		0x00000082
 #define FSF_REF_TAG_CHECK_FAILURE		0x00000083
 #define FSF_ADAPTER_STATUS_AVAILABLE		0x000000AD
+#define FSF_FCP_RSP_AVAILABLE			0x000000AF
 #define FSF_UNKNOWN_COMMAND			0x000000E2
 #define FSF_UNKNOWN_OP_SUBTYPE                  0x000000E3
 #define FSF_INVALID_COMMAND_OPTION              0x000000E5
-- 
2.8.4