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contrib: dracut: fix race with root=zfs:dset when necessities required 

This had always worked in my testing, but a user on hardware reported
this to happen 100%, and I reproduced it once with cold VM host caches.

dracut-zfs-generator runs as a systemd generator, i.e. at Some
Relatively Early Time; if root= is a fixed dataset, it tries to
"solve [necessities] statically at generation time".

If by that point zfs-import.target hasn't popped (because the import is
taking a non-negligible amount of time for whatever reason), it'll see
no children for the root datase, and as such generate no mounts.

This has never had any right to work. No-one caught this earlier because
it's just that much more convenient to have root=zfs:AUTO, which orders
itself properly.

To fix this, always run zfs-nonroot-necessities.service;
this additionally simplifies the implementation by:
  * making BOOTFS from zfs-env-bootfs.service be the real, canonical,
    root dataset name, not just "whatever the first bootfs is",
    and only set it if we're ZFS-booting
  * zfs-{rollback,snapshot}-bootfs.service can use this instead of
    re-implementing it
  * having zfs-env-bootfs.service also set BOOTFSFLAGS
  * this means the sysroot.mount drop-in can be fixed text
  * zfs-nonroot-necessities.service can also be constant and always
    enabled, because it's conditioned on BOOTFS being set

There is no longer any code generated at run-time
(the sysroot.mount drop-in is an unavoidable gratuitous cp).

The flow of BOOTFS{,FLAGS} from zfs-env-bootfs.service to sysroot.mount
is not noted explicitly in dracut.zfs(7), because (a) at some point it's
just visual noise and (b) it's already ordered via d-p-m.s from z-i.t.

Backport-of: 3399a30ee0
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
This commit is contained in:
наб 2023-03-28 22:49:50 +02:00 committed by Tony Hutter
parent 33003ecc93
commit 18edf7a3ba
9 changed files with 54 additions and 76 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
contrib/dracut/90zfs/Makefile.am
View File

@ -15,6 +15,7 @@ pkgdracut_SCRIPTS = \
pkgdracut_DATA = \
zfs-env-bootfs.service \
zfs-nonroot-necessities.service \
zfs-snapshot-bootfs.service \
zfs-rollback-bootfs.service

3
contrib/dracut/90zfs/module-setup.sh.in
View File

@ -84,6 +84,9 @@ install() {
inst_simple "${moddir}/zfs-env-bootfs.service" "${systemdsystemunitdir}/zfs-env-bootfs.service"
systemctl -q --root "${initdir}" add-wants zfs-import.target zfs-env-bootfs.service
inst_simple "${moddir}/zfs-nonroot-necessities.service" "${systemdsystemunitdir}/zfs-nonroot-necessities.service"
systemctl -q --root "${initdir}" add-requires initrd-root-fs.target zfs-nonroot-necessities.service
for _service in \
"zfs-import-scan.service" \
"zfs-import-cache.service"; do

15
contrib/dracut/90zfs/zfs-env-bootfs.service.in
View File

@ -1,6 +1,5 @@
[Unit]
Description=Set BOOTFS environment for dracut
Documentation=man:zpool(8)
Description=Set BOOTFS and BOOTFSFLAGS environment variables for dracut
DefaultDependencies=no
After=zfs-import-cache.service
After=zfs-import-scan.service
@ -8,7 +7,17 @@ Before=zfs-import.target
[Service]
Type=oneshot
ExecStart=/bin/sh -c "exec systemctl set-environment BOOTFS=$(@sbindir@/zpool list -H -o bootfs | grep -m1 -vFx -)"
ExecStart=/bin/sh -c ' \
. /lib/dracut-zfs-lib.sh; \
decode_root_args || exit 0; \
[ "$root" = "zfs:AUTO" ] && root="$(@sbindir@/zpool list -H -o bootfs | grep -m1 -vFx -)"; \
rootflags="$(getarg rootflags=)"; \
case ",$rootflags," in \
*,zfsutil,*) ;; \
,,) rootflags=zfsutil ;; \
*) rootflags="zfsutil,$rootflags" ;; \
esac; \
exec systemctl set-environment BOOTFS="$root" BOOTFSFLAGS="$rootflags"'
[Install]
WantedBy=zfs-import.target

67
contrib/dracut/90zfs/zfs-generator.sh.in
View File

@ -14,81 +14,24 @@ GENERATOR_DIR="$1"
. /lib/dracut-zfs-lib.sh
decode_root_args || exit 0
[ -z "${rootflags}" ] && rootflags=$(getarg rootflags=)
case ",${rootflags}," in
*,zfsutil,*) ;;
,,) rootflags=zfsutil ;;
*) rootflags="zfsutil,${rootflags}" ;;
esac
[ -n "$debug" ] && echo "zfs-generator: writing extension for sysroot.mount to $GENERATOR_DIR/sysroot.mount.d/zfs-enhancement.conf" >> /dev/kmsg
mkdir -p "$GENERATOR_DIR"/sysroot.mount.d "$GENERATOR_DIR"/initrd-root-fs.target.requires "$GENERATOR_DIR"/dracut-pre-mount.service.d
mkdir -p "$GENERATOR_DIR"/sysroot.mount.d "$GENERATOR_DIR"/dracut-pre-mount.service.d
{
echo "[Unit]"
echo "Before=initrd-root-fs.target"
echo "After=zfs-import.target"
echo
echo "[Mount]"
if [ "${root}" = "zfs:AUTO" ]; then
echo "PassEnvironment=BOOTFS"
echo 'What=${BOOTFS}'
else
echo "What=${root}"
fi
echo "PassEnvironment=BOOTFS BOOTFSFLAGS"
echo 'What=${BOOTFS}'
echo "Type=zfs"
echo "Options=${rootflags}"
echo 'Options=${BOOTFSFLAGS}'
} > "$GENERATOR_DIR"/sysroot.mount.d/zfs-enhancement.conf
ln -fs ../sysroot.mount "$GENERATOR_DIR"/initrd-root-fs.target.requires/sysroot.mount
if [ "${root}" = "zfs:AUTO" ]; then
{
echo "[Unit]"
echo "Before=initrd-root-fs.target"
echo "After=sysroot.mount"
echo "DefaultDependencies=no"
echo
echo "[Service]"
echo "Type=oneshot"
echo "PassEnvironment=BOOTFS"
echo "ExecStart=/bin/sh -c '" ' \
. /lib/dracut-zfs-lib.sh; \
_zfs_nonroot_necessities_cb() { \
zfs mount | grep -m1 -q "^$1 " && return 0; \
echo "Mounting $1 on /sysroot$2"; \
mount -o zfsutil -t zfs "$1" "/sysroot$2"; \
}; \
for_relevant_root_children "${BOOTFS}" _zfs_nonroot_necessities_cb;' \
"'"
} > "$GENERATOR_DIR"/zfs-nonroot-necessities.service
ln -fs ../zfs-nonroot-necessities.service "$GENERATOR_DIR"/initrd-root-fs.target.requires/zfs-nonroot-necessities.service
else
# We can solve this statically at generation time, so do!
_zfs_generator_cb() {
dset="${1}"
mpnt="${2}"
unit="$(systemd-escape --suffix=mount -p "/sysroot${mpnt}")"
{
echo "[Unit]"
echo "Before=initrd-root-fs.target"
echo "After=sysroot.mount"
echo
echo "[Mount]"
echo "Where=/sysroot${mpnt}"
echo "What=${dset}"
echo "Type=zfs"
echo "Options=zfsutil"
} > "$GENERATOR_DIR/${unit}"
ln -fs ../"${unit}" "$GENERATOR_DIR"/initrd-root-fs.target.requires/"${unit}"
}
for_relevant_root_children "${root}" _zfs_generator_cb
fi
{
echo "[Unit]"
echo "After=zfs-import.target"

2
contrib/dracut/90zfs/zfs-lib.sh.in
View File

@ -38,7 +38,7 @@ mount_dataset() {
# for_relevant_root_children DATASET EXEC
# Runs "EXEC dataset mountpoint" for all children of DATASET that are needed for system bringup
# Used by zfs-generator.sh and friends, too!
# Used by zfs-nonroot-necessities.service and friends, too!
for_relevant_root_children() {
dataset="${1}"
exec="${2}"

20
contrib/dracut/90zfs/zfs-nonroot-necessities.service.in Normal file
View File

@ -0,0 +1,20 @@
[Unit]
Before=initrd-root-fs.target
After=sysroot.mount
DefaultDependencies=no
ConditionEnvironment=BOOTFS
[Service]
Type=oneshot
PassEnvironment=BOOTFS
ExecStart=/bin/sh -c ' \
. /lib/dracut-zfs-lib.sh; \
_zfs_nonroot_necessities_cb() { \
@sbindir@/zfs mount | grep -m1 -q "^$1 " && return 0; \
echo "Mounting $1 on /sysroot$2"; \
mount -o zfsutil -t zfs "$1" "/sysroot$2"; \
}; \
for_relevant_root_children "${BOOTFS}" _zfs_nonroot_necessities_cb'
[Install]
RequiredBy=initrd-root-fs.target

3
contrib/dracut/90zfs/zfs-rollback-bootfs.service.in
View File

@ -5,8 +5,9 @@ After=zfs-import.target dracut-pre-mount.service zfs-snapshot-bootfs.service
Before=dracut-mount.service
DefaultDependencies=no
ConditionKernelCommandLine=bootfs.rollback
ConditionEnvironment=BOOTFS
[Service]
Type=oneshot
ExecStart=/bin/sh -c '. /lib/dracut-zfs-lib.sh; decode_root_args || exit; [ "$root" = "zfs:AUTO" ] && root="$BOOTFS"; SNAPNAME="$(getarg bootfs.rollback)"; exec @sbindir@/zfs rollback -Rf "$root@${SNAPNAME:-%v}"'
ExecStart=/bin/sh -c '. /lib/dracut-lib.sh; SNAPNAME="$(getarg bootfs.rollback)"; exec @sbindir@/zfs rollback -Rf "$BOOTFS@${SNAPNAME:-%v}"'
RemainAfterExit=yes

3
contrib/dracut/90zfs/zfs-snapshot-bootfs.service.in
View File

@ -5,8 +5,9 @@ After=zfs-import.target dracut-pre-mount.service
Before=dracut-mount.service
DefaultDependencies=no
ConditionKernelCommandLine=bootfs.snapshot
ConditionEnvironment=BOOTFS
[Service]
Type=oneshot
ExecStart=-/bin/sh -c '. /lib/dracut-zfs-lib.sh; decode_root_args || exit; [ "$root" = "zfs:AUTO" ] && root="$BOOTFS"; SNAPNAME="$(getarg bootfs.snapshot)"; exec @sbindir@/zfs snapshot "$root@${SNAPNAME:-%v}"'
ExecStart=-/bin/sh -c '. /lib/dracut-lib.sh; SNAPNAME="$(getarg bootfs.snapshot)"; exec @sbindir@/zfs snapshot "$BOOTFS@${SNAPNAME:-%v}"'
RemainAfterExit=yes

16
man/man7/dracut.zfs.7
View File

@ -1,6 +1,6 @@
.\" SPDX-License-Identifier: 0BSD
.\"
.Dd April 4, 2022
.Dd March 28, 2023
.Dt DRACUT.ZFS 7
.Os
.
@ -28,13 +28,13 @@ zfs-import-scan.service \(da \(da | zfs-import-c
zfs-import.target \(-> dracut-pre-mount.service
| \(ua |
| dracut-zfs-generator |
| ____________________/|
| _____________________/|
|/ \(da
| sysroot.mount \(<-\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em dracut-zfs-generator
| | \(da |
| \(da sysroot-{usr,etc,lib,&c.}.mount |
| initrd-root-fs.target \(<-\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em or \(da
| | zfs-nonroot-necessities.service
| sysroot.mount \(<-\(em\(em\(em dracut-zfs-generator
| |
| \(da
| initrd-root-fs.target \(<-\(em zfs-nonroot-necessities.service
| | |
| \(da |
\(da dracut-mount.service |
zfs-snapshot-bootfs.service | |
@ -42,7 +42,7 @@ zfs-import-scan.service \(da \(da | zfs-import-c
\(da … |
zfs-rollback-bootfs.service | |
| \(da |
| sysroot-usr.mount \(<-\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em/
| /sysroot/{usr,etc,lib,&c.} \(<-\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em\(em/
| |
| \(da
| initrd-fs.target