linux-stable/drivers/s390/scsi
Steffen Maier c820657917 scsi: zfcp: reduce flood of fcrscn1 trace records on multi-element RSCN
If an incoming ELS of type RSCN contains more than one element, zfcp
suboptimally causes repeated erp trigger NOP trace records for each
previously failed port. These could be ports that went away.  It loops over
each RSCN element, and for each of those in an inner loop over all
zfcp_ports.

The trigger to recover failed ports should be just the reception of some
RSCN, no matter how many elements it has. So we can loop over failed ports
separately, and only then loop over each RSCN element to handle the
non-failed ports.

The call chain was:

  zfcp_fc_incoming_rscn
    for (i = 1; i < no_entries; i++)
      _zfcp_fc_incoming_rscn
        list_for_each_entry(port, &adapter->port_list, list)
          if (masked port->d_id match) zfcp_fc_test_link
          if (!port->d_id) zfcp_erp_port_reopen "fcrscn1"   <===

In order the reduce the "flooding" of the REC trace area in such cases, we
factor out handling the failed ports to be outside of the entries loop:

  zfcp_fc_incoming_rscn
    if (no_entries > 1)                                     <===
      list_for_each_entry(port, &adapter->port_list, list)  <===
        if (!port->d_id) zfcp_erp_port_reopen "fcrscn1"     <===
    for (i = 1; i < no_entries; i++)
      _zfcp_fc_incoming_rscn
        list_for_each_entry(port, &adapter->port_list, list)
          if (masked port->d_id match) zfcp_fc_test_link

Abbreviated example trace records before this code change:

Tag            : fcrscn1
WWPN           : 0x500507630310d327
ERP want       : 0x02
ERP need       : 0x02

Tag            : fcrscn1
WWPN           : 0x500507630310d327
ERP want       : 0x02
ERP need       : 0x00                 NOP => superfluous trace record

The last trace entry repeats if there are more than 2 RSCN elements.

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
2019-03-27 21:26:12 -04:00
..
Makefile s390: add a few more SPDX identifiers 2017-12-05 07:51:09 +01:00
zfcp_aux.c scsi: zfcp: fix sysfs block queue limit output for max_segment_size 2019-01-29 01:14:59 -05:00
zfcp_ccw.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
zfcp_dbf.c scsi: zfcp: silence all W=1 build warnings for existing kdoc 2018-11-15 15:01:18 -05:00
zfcp_dbf.h scsi: zfcp: silence remaining kdoc warnings in header files 2018-11-15 15:01:18 -05:00
zfcp_def.h scsi: zfcp: use enum zfcp_erp_steps for struct zfcp_erp_action.step 2018-11-15 15:01:18 -05:00
zfcp_erp.c scsi: zfcp: fix scsi_eh host reset with port_forced ERP for non-NPIV FCP devices 2019-03-27 21:26:12 -04:00
zfcp_ext.h scsi: zfcp: fix scsi_eh host reset with port_forced ERP for non-NPIV FCP devices 2019-03-27 21:26:12 -04:00
zfcp_fc.c scsi: zfcp: reduce flood of fcrscn1 trace records on multi-element RSCN 2019-03-27 21:26:12 -04:00
zfcp_fc.h scsi: zfcp: silence remaining kdoc warnings in header files 2018-11-15 15:01:18 -05:00
zfcp_fsf.c scsi: zfcp: silence all W=1 build warnings for existing kdoc 2018-11-15 15:01:18 -05:00
zfcp_fsf.h scsi: zfcp: silence remaining kdoc warnings in header files 2018-11-15 15:01:18 -05:00
zfcp_qdio.c s390/qdio: make SBAL address array type-safe 2019-02-07 11:57:07 +01:00
zfcp_qdio.h scsi: zfcp: silence remaining kdoc warnings in header files 2018-11-15 15:01:18 -05:00
zfcp_reqlist.h scsi: zfcp: silence remaining kdoc warnings in header files 2018-11-15 15:01:18 -05:00
zfcp_scsi.c scsi: zfcp: fix scsi_eh host reset with port_forced ERP for non-NPIV FCP devices 2019-03-27 21:26:12 -04:00
zfcp_sysfs.c scsi: zfcp: support SCSI_ADAPTER_RESET via scsi_host sysfs attribute host_reset 2018-05-18 11:28:15 -04:00
zfcp_unit.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00