Fibre Channel NPIV - device names in /dev/disk/by-path are not persistent / unique

This document (7022659) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 12 Service Pack 1 (SLES 12 SP1)

Situation

The "/dev/disk/by-path" links are not unique for Fibre Channel NPIV devices.

Resolution

It is needed to create two additional udev files each with the content and location / naming as below:

1. "/usr/lib/udev/rules.d/59-fc-wwpn-id.rules"

#
# FC WWPN-based by-path links
#

ACTION!="add|change", GOTO="fc_wwpn_end"
KERNEL!="sd*", GOTO="fc_wwpn_end"

ENV{DEVTYPE}=="disk", IMPORT{program}="fc_wwpn_id %p"
ENV{DEVTYPE}=="partition", IMPORT{parent}="FC_*"
ENV{FC_TARGET_WWPN}!="$*"; GOTO="fc_wwpn_end"
ENV{FC_INITIATOR_WWPN}!="$*"; GOTO="fc_wwpn_end"
ENV{FC_TARGET_LUN}!="$*"; GOTO="fc_wwpn_end"

ENV{DEVTYPE}=="disk", SYMLINK+="disk/by-path/fc-$env{FC_INITIATOR_WWPN}-$env{FC_TARGET_WWPN}-lun-$env{FC_TARGET_LUN}"
ENV{DEVTYPE}=="partition", SYMLINK+="disk/by-path/fc-$env{FC_INITIATOR_WWPN}-$env{FC_TARGET_WWPN}-lun-$env{FC_TARGET_LUN}-part%n"

LABEL="fc_wwpn_end"

2. "/usr/lib/udev/fc_wwpn_id"

#!/bin/bash
#
# fc_wwpn_id
#
# Generates device node names links based on FC WWPN
# Copyright (c) 2016 Hannes Reinecke, SUSE Linux GmbH
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation version 2 of the License.
#

DEVPATH=$1
SCSIPATH=$(cd -P "/sys$DEVPATH/device" || exit; echo "$PWD")

d=$SCSIPATH
[ -d "$d/scsi_disk" ] || exit 0
target_lun=${d##*:}

    while [ -n "$d" ] ; do
        d=${d%/*}
        e=${d##*/}
        case "$e" in
        rport*)
            rport=$e
            rport_dir="/sys/class/fc_remote_ports/$rport"
            if [ -d "$rport_dir" ] ; then
            rport_wwpn=$(cat "$rport_dir/port_name")
            fi
            ;;
        host*)
            host=$e
            host_dir="/sys/class/fc_host/$host"
            if [ -d "$host_dir" ] ; then
            host_wwpn=$(cat "$host_dir/port_name")
            break;
            fi
        esac
done

echo "FC_TARGET_LUN=$target_lun"

if [ -n "$rport_wwpn" ] ; then
    echo "FC_TARGET_WWPN=$rport_wwpn"
fi

if [ -n "$host_wwpn" ] ; then
    echo "FC_INITIATOR_WWPN=$host_wwpn"
fi

3. Make sure to set the script file to be executable by running "chmod +x /usr/lib/udev/fc_wwpn_id".

Cause

Creation of symlinks for Fibre Channel NPIV devices are not handled correctly.

Additional Information

For SLES12 SP2 and later, the issue is resolved with "sg3_utils-1.43-16.5.1.x86_64" and later. However since SLES12 SP1 is in LTSS (Long Term Service Pack Support) updates for SP1 can only be accepted if the problem is a regression that was caused by a maintenance update, which is not the case here.

Due to this the resolution to resolve the issue for SLES12 SP1 systems are documented with this TID.

Disclaimer

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