systemd mount generator and tracking ZEDLET

zfs-mount-generator implements the "systemd generator" protocol,
producing systemd.mount units from the cached outputs of zfs list,
during early boot, integrating with systemd.

Each pool has an indpendent cache of the command

  zfs list -H -oname,mountpoint,canmount -tfilesystem -r $pool

which is kept synchronized by the ZEDLET

  history_event-zfs-list-cacher.sh

Datasets not in the cache will be loaded later in the boot process by
zfs-mount.service, including pools without a cache.

Among other things, this allows for complex mount hierarchies.

Reviewed-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Antonio Russo <antonio.e.russo@gmail.com>
Closes #7329
This commit is contained in:
Antonio Russo 2018-04-06 17:11:09 -04:00 committed by Brian Behlendorf
parent 5c27ec1088
commit 55d80e651a
12 changed files with 282 additions and 3 deletions

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@ -4,7 +4,8 @@ DEFAULT_INCLUDES += \
-I$(top_srcdir)/include \
-I$(top_srcdir)/lib/libspl/include
EXTRA_DIST = zed.d/README
EXTRA_DIST = zed.d/README \
zed.d/history_event-zfs-list-cacher.sh.in
sbin_PROGRAMS = zed
@ -60,6 +61,7 @@ dist_zedexec_SCRIPTS = \
zed.d/all-syslog.sh \
zed.d/data-notify.sh \
zed.d/generic-notify.sh \
zed.d/history_event-zfs-list-cacher.sh \
zed.d/resilver_finish-notify.sh \
zed.d/scrub_finish-notify.sh \
zed.d/statechange-led.sh \
@ -69,6 +71,13 @@ dist_zedexec_SCRIPTS = \
zed.d/pool_import-led.sh \
zed.d/resilver_finish-start-scrub.sh
zed.d/history_event-zfs-list-cacher.sh: %: %.in
-$(SED) -e 's,@bindir\@,$(bindir),g' \
-e 's,@runstatedir\@,$(runstatedir),g' \
-e 's,@sbindir\@,$(sbindir),g' \
-e 's,@sysconfdir\@,$(sysconfdir),g' \
$< >'$@'
zedconfdefaults = \
all-syslog.sh \
data-notify.sh \

1
cmd/zed/zed.d/.gitignore vendored Normal file
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@ -0,0 +1 @@
history_event-zfs-list-cacher.sh

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@ -0,0 +1,73 @@
#!/bin/sh
#
# Track changes to enumerated pools for use in early-boot
set -ef
FSLIST_DIR="@sysconfdir@/zfs/zfs-list.cache"
FSLIST_TMP="@runstatedir@/zfs-list.cache.new"
FSLIST="${FSLIST_DIR}/${ZEVENT_POOL}"
# If the pool specific cache file is not writeable, abort
[ -w "${FSLIST}" ] || exit 0
[ -f "${ZED_ZEDLET_DIR}/zed.rc" ] && . "${ZED_ZEDLET_DIR}/zed.rc"
. "${ZED_ZEDLET_DIR}/zed-functions.sh"
zed_exit_if_ignoring_this_event
zed_check_cmd "${ZFS}" sort diff grep
# If we are acting on a snapshot, we have nothing to do
printf '%s' "${ZEVENT_HISTORY_DSNAME}" | grep '@' && exit 0
# We obtain a lock on zfs-list to avoid any simultaneous writes.
# If we run into trouble, log and drop the lock
abort_alter() {
zed_log_msg "Error updating zfs-list.cache!"
zed_unlock zfs-list
}
finished() {
zed_unlock zfs-list
trap - EXIT
exit 0
}
case "${ZEVENT_HISTORY_INTERNAL_NAME}" in
create|"finish receiving"|import|destroy|rename)
;;
export)
zed_lock zfs-list
trap abort_alter EXIT
echo > "${FSLIST}"
finished
;;
set|inherit)
# Only act if the mountpoint or canmount setting is altered.
case "${ZEVENT_HISTORY_INTERNAL_STR}" in
canmount=*|mountpoint=*) ;;
*) exit 0 ;;
esac
;;
*)
# Ignore all other events.
exit 0
;;
esac
zed_lock zfs-list
trap abort_alter EXIT
"${ZFS}" list -H -tfilesystem -oname,mountpoint,canmount -r "${ZEVENT_POOL}" \
>"${FSLIST_TMP}"
# Sort the output so that it is stable
sort "${FSLIST_TMP}" -o "${FSLIST_TMP}"
# Don't modify the file if it hasn't changed
diff -q "${FSLIST_TMP}" "${FSLIST}" || mv "${FSLIST_TMP}" "${FSLIST}"
rm -f "${FSLIST_TMP}"
finished

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@ -20,6 +20,11 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
[install systemd module load files into dir [[/usr/lib/modules-load.d]]]),
systemdmoduleloaddir=$withval,systemdmodulesloaddir=/usr/lib/modules-load.d)
AC_ARG_WITH(systemdgeneratordir,
AC_HELP_STRING([--with-systemdgeneratordir=DIR],
[install systemd generators in dir [[/usr/lib/systemd/system-generators]]]),
systemdgeneratordir=$withval,systemdgeneratordir=/usr/lib/systemd/system-generators)
AS_IF([test "x$enable_systemd" = xcheck], [
AS_IF([systemctl --version >/dev/null 2>&1],
[enable_systemd=yes],
@ -32,7 +37,7 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
AS_IF([test "x$enable_systemd" = xyes], [
ZFS_INIT_SYSTEMD=systemd
ZFS_MODULE_LOAD=modules-load.d
DEFINE_SYSTEMD='--with systemd --define "_unitdir $(systemdunitdir)" --define "_presetdir $(systemdpresetdir)"'
DEFINE_SYSTEMD='--with systemd --define "_unitdir $(systemdunitdir)" --define "_presetdir $(systemdpresetdir)" --define "_generatordir $(systemdgeneratordir)"'
modulesloaddir=$systemdmodulesloaddir
],[
DEFINE_SYSTEMD='--without systemd'
@ -43,5 +48,6 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
AC_SUBST(DEFINE_SYSTEMD)
AC_SUBST(systemdunitdir)
AC_SUBST(systemdpresetdir)
AC_SUBST(systemdgeneratordir)
AC_SUBST(modulesloaddir)
])

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@ -67,6 +67,7 @@ AC_CONFIG_FILES([
etc/zfs/Makefile
etc/systemd/Makefile
etc/systemd/system/Makefile
etc/systemd/system-generators/Makefile
etc/sudoers.d/Makefile
etc/modules-load.d/Makefile
man/Makefile

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@ -1 +1 @@
SUBDIRS = system
SUBDIRS = system system-generators

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@ -0,0 +1 @@
zfs-mount-generator

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@ -0,0 +1,15 @@
systemdgenerator_SCRIPTS = \
zfs-mount-generator
EXTRA_DIST = \
$(top_srcdir)/etc/systemd/system-generators/zfs-mount-generator.in
$(systemdgenerator_SCRIPTS): %: %.in
-$(SED) -e 's,@bindir\@,$(bindir),g' \
-e 's,@runstatedir\@,$(runstatedir),g' \
-e 's,@sbindir\@,$(sbindir),g' \
-e 's,@sysconfdir\@,$(sysconfdir),g' \
$< >'$@'
distclean-local::
-$(RM) $(systemdgenerator_SCRIPTS)

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@ -0,0 +1,115 @@
#!/bin/sh
# zfs-mount-generator - generates systemd mount units for zfs
# Copyright (c) 2017 Antonio Russo <antonio.e.russo@gmail.com>
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
set -ef
FSLIST="@sysconfdir@/zfs/zfs-list.cache"
[ -d "${FSLIST}" ] || exit 0
do_fail() {
printf 'zfs-mount-generator.sh: %s\n' "$*" > /dev/kmsg
exit 1
}
# see systemd.generator
if [ $# -eq 0 ] ; then
dest_norm="/tmp"
elif [ $# -eq 3 ] ; then
dest_norm="${1}"
else
do_fail "zero or three arguments required"
fi
# For ZFSs marked "auto", a dependency is created for local-fs.target. To
# avoid regressions, this dependency is reduced to "wants" rather than
# "requires". **THIS MAY CHANGE**
req_dir="${dest_norm}/local-fs.target.wants/"
mkdir -p "${req_dir}"
# All needed information about each ZFS is available from
# zfs list -H -t filesystem -oname,mountpoint,canmount
# cached in $FSLIST, and each line is processed by the following function:
process_line() {
# Check for canmount=off .
if [ "${3}" = "off" ] ; then
return
elif [ "${3}" = "noauto" ] ; then
# Don't let a noauto marked mountpoint block an "auto" market mountpoint
return
elif [ "${3}" = "on" ] ; then
: # This is OK
else
do_fail "invalid canmount"
fi
# Check for legacy and blank mountpoints.
if [ "${2}" = "legacy" ] ; then
return
elif [ "${2}" = "none" ] ; then
return
elif [ "${2%"${2#?}"}" != "/" ] ; then
do_fail "invalid mountpoint $*"
fi
# Escape the mountpoint per systemd policy.
mountfile="$(systemd-escape "${2#?}").mount"
# If the mountpoint has already been created, give it precedence.
if [ -e "${dest_norm}/${mountfile}" ] ; then
printf 'zfs-mount-generator.sh: %s.mount already exists\n' "${2}" \
>/dev/kmsg
return
fi
# By ordering before zfs-mount.service, we avoid race conditions.
cat > "${dest_norm}/${mountfile}" << EOF
# Automatically generated by zfs-mount-generator
[Unit]
SourcePath=${FSLIST}/${cachefile}
Documentation=man:zfs-mount-generator(8)
Before=local-fs.target zfs-mount.service
After=zfs-import.target
Wants=zfs-import.target
[Mount]
Where=${2}
What=${1}
Type=zfs
Options=zfsutil,auto
EOF
# Finally, create the appropriate dependencies based on the ZFS properties.
[ "$3" = "on" ] & ln -s "../${mountfile}" "${req_dir}"
}
# Feed each line into process_line
for cachefile in $(ls "${FSLIST}") ; do
while read -r fs ; do
process_line $fs
done < "${FSLIST}/${cachefile}"
done

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@ -4,6 +4,7 @@ dist_man_MANS = \
vdev_id.8 \
zdb.8 \
zfs.8 \
zfs-mount-generator.8 \
zfs-program.8 \
zgenhostid.8 \
zinject.8 \

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@ -0,0 +1,56 @@
.TH "ZFS\-MOUNT\-GENERATOR" "8" "ZFS" "zfs-mount-generator" "\""
.SH "NAME"
zfs\-mount\-generator \- generates systemd mount units for zfs
.SH SYNOPSIS
.B /lib/systemd/system-generators/zfs\-mount\-generator
.sp
.SH DESCRIPTION
The zfs\-mount\-generator implements the \fBGenerators Specification\fP
of
.BR systemd (1),
and is called during early boot to generate
.BR systemd.mount (5)
units for automatically mounted datasets. Mount ordering and dependencies
are created for all tracked pools (see below). If a dataset has
.BR canmount=on
and
.BR mountpoint
set, the
.BR auto
mount option will be set, and a dependency for
.BR local-fs.target
on the mount will be created.
Because zfs pools may not be available very early in the boot process,
information on ZFS mountpoints must be stored separately. The output
of the command
.PP
.RS 4
zfs list -H -oname,mountpoint,canmount
.RE
.PP
for datasets that should be mounted by systemd, should be kept
separate from the pool, at
.PP
.RS 4
.RI @sysconfdir@/zfs/zfs-list.cache/ POOLNAME
.
.RE
.PP
The cache file, if writeable, will be kept synchronized with the pool
state by the ZEDLET
.PP
.RS 4
history_event-zfs-list-cacher.sh .
.RE
.PP
.sp
.SH SEE ALSO
.BR zfs (5)
.BR zfs-events (5)
.BR zed (8)
.BR zpool (5)
.BR systemd (1)
.BR systemd.target (5)
.BR systemd.special (7)
.BR systemd.mount (7)

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@ -338,6 +338,7 @@ systemctl --system daemon-reload >/dev/null || true
/usr/lib/modules-load.d/*
%{_unitdir}/*
%{_presetdir}/*
%{_generatordir}/*
%else
%config(noreplace) %{_sysconfdir}/init.d/*
%config(noreplace) %{_initconfdir}/zfs