DLPX-73192 Establish appropriate systemd service dependencies for iSCSI initiator (#262)

* DLPX-73192 Establish appropriate systemd service dependencies for iSCSI initiator

* Fix comment.

Author: Don Brady

files/common/etc/systemd/system/open-iscsi.service.d/override.conf

@@ -0,0 +1,10 @@
+#
+# Customize the open-iscsi service to be zfs aware.  When attempting a service
+# stop, check if there are any zpools still actively using iSCSI devices.
+#
+[Service]
+ExecStop=
+ExecStop=/lib/open-iscsi/zpool_on_iscsi.sh
+ExecStop=/lib/open-iscsi/umountiscsi.sh
+ExecStop=/bin/sync
+ExecStop=/lib/open-iscsi/logout-all.sh

files/common/lib/open-iscsi/zpool_on_iscsi.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+#
+# Copyright (c) 2021 by Delphix. All rights reserved.
+#
+
+#
+# This script checks if any iSCSI devices are in use by an active zfs pool.
+#
+
+PATH=/sbin:/bin
+
+ZFS_FS_TYPE="zfs_member"
+
+function usage() {
+	echo "Usage: $0 [--verbose]" >&2
+	exit 2
+}
+
+if [[ $# -gt 1 ]]; then
+	usage
+fi
+
+VERBOSE=0
+if [[ $# -eq 1 ]]; then
+	if [[ "$1" != "--verbose" ]]; then
+		usage
+	fi
+	VERBOSE=1
+fi
+
+shopt -s nullglob
+
+# locate iscsi devices that belong to a zfs pool
+while read -r type transport device; do
+	# first locate iscsi devices
+	[[ "$type" == "disk" && "$transport" == "iscsi" ]] || continue
+	[[ $VERBOSE -eq 0 ]] || echo "${device} uses iSCSI"
+
+	# locate any partitions for this device
+	for partition in /dev/"${device}"?*; do
+		# check if partition type is zfs and grab the pool name
+		read -r fstype pool <<<"$(lsblk -n -o FSTYPE,LABEL "${partition}")"
+		[[ "$fstype" == "$ZFS_FS_TYPE" && -n "$pool" ]] || continue
+		[[ $VERBOSE -eq 0 ]] || echo " ${partition} is a member of pool ${pool}"
+
+		# check if pool is active (imported)
+		health=$(zpool list -H -o name,health "${pool}" 2>&1)
+		status=$?
+		[[ $VERBOSE -eq 0 ]] || echo "  ${health} ($status)"
+		if [[ $status -eq 0 ]]; then
+			echo "device '${partition}' in use by zfs pool '${pool}'" >&2
+			exit 1
+		fi
+	done
+done < <(lsblk --scsi -n -o TYPE,TRAN,NAME)
+
+exit 0