Relatime is always turned on temporarily on ZFS root.

[crocket]

System information

Type	Version/Name
Distribution Name	Gentoo
Distribution Version	None
Linux Kernel	4.14.65-gentoo
Architecture	x86_64
ZFS Version	0.7.11-r0-gentoo
SPL Version	0.7.11-r0-gentoo

Describe the problem you're observing

I want to apply noatime to every single mount, but / is resisting my will.

$ findmnt | grep zfs
/                             os/ROOT/gentoo    zfs         rw,relatime,xattr,noacl
├─/home                       os/HOME           zfs         rw,noatime,xattr,noacl
├─/mnt/data                   user-data/data    zfs         rw,noatime,xattr,posixacl
├─/root                       os/HOME/root      zfs         rw,noatime,xattr,noacl
├─/usr/portage                os/GENTOO/portage zfs         rw,nosuid,noatime,xattr,noacl

$ cat /proc/mounts | grep zfs
os/ROOT/gentoo / zfs rw,relatime,xattr,noacl 0 0
os/HOME /home zfs rw,noatime,xattr,noacl 0 0
user-data/data /mnt/data zfs rw,noatime,xattr,posixacl 0 0
os/HOME/root /root zfs rw,noatime,xattr,noacl 0 0
os/GENTOO/portage /usr/portage zfs rw,nosuid,noatime,xattr,noacl 0 0

$ /sbin/zfs get all os/ROOT/gentoo | grep time
os/ROOT/gentoo  atime                 off                    inherited from os
os/ROOT/gentoo  relatime              on                     temporary

$ cat /etc/fstab
PARTUUID="e271ef53-7377-0545-9f0e-8467fafd1202" none swap sw 0 0
PARTUUID="d5179cfd-ea96-4183-8c0b-9ffc20a9b990" none swap sw 0 0
tmpfs /var/tmp/portage tmpfs size=14G,uid=portage,gid=portage,mode=775,noatime 0 0
tmpfs /tmp tmpfs size=8G,mode=1777,noatime 0 0
PARTUUID="7e95e77c-f08c-f34d-a2d3-9d540ff191c4" /boot btrfs rw,noatime,discard 0 0
PARTUUID="17485930-4257-41fc-bc1a-5921ea09c2a4" /boot/efi vfat rw,noatime,discard 0 0

$ /sbin/zfs list
NAME                           USED  AVAIL  REFER  MOUNTPOINT
os                            63.7G  46.7G    96K  none
os/GENTOO                     33.4G  46.7G    96K  none
os/GENTOO/portage             33.4G  46.7G  33.4G  /usr/portage
os/HOME                       20.9G  46.7G  19.8G  /home
os/HOME/root                  23.5M  46.7G  23.5M  /root
os/ROOT                       9.41G  46.7G    96K  none
os/ROOT/gentoo                9.41G  46.7G  9.41G  /
user-data                     1.23T  1.40T    96K  none
user-data/data                1.23T  1.40T  1.22T  /mnt/data

Describe how to reproduce the problem

Install root on a dataset, and set bootfs to that dataset. grub-mkconfig will take care of the rest.

[crocket]

I don't think it is a question. It is an issue that requires modification of zfs.

[rlaager]

I can reproduce this on Ubuntu 18.04 too. Unless we have some universal fix, I think the initramfs script should work around this.

[GregorKopka]

man zpool states:

When a file system is mounted, either through mount(8) for legacy mounts or the zfs mount command for normal file systems, its mount options are set according to its properties. The correlation between properties and mount options is as follows:

PROPERTY MOUNT OPTION
atime atime/noatime
canmount auto/noauto
devices dev/nodev
exec exec/noexec
readonly ro/rw
relatime relatime/norelatime
setuid suid/nosuid
xattr xattr/noxattr

what's happening is

# zfs create tank/test -o atime=off -o canmount=noauto -o readonly=on
# mkdir /tmp/test
# mount -o zfsutil -t zfs tank/test /tmp/test/
# mount | grep test
tank/test on /tmp/test type zfs (rw,relatime,xattr,noacl)

The mount options are set according to its properties isn't happening as advertised when mounting using mount(8). Also

# umount /tmp/test/
# zfs set canmount=off tank/test
# mount -t zfs tank/test /tmp/test/
# mount | grep test
tank/test on /tmp/test type zfs (rw,relatime,xattr,noacl)

Which means also

canmount=on|off|noauto
If this property is set to off, the file system cannot be mounted, and is ignored by zfs mount -a.

as stated in man zfs isn't enforced (which it should, at least that's what I expect when reading that sentence).

[bunder2015]

FWIW, I've seen this on gentoo as well. I had hacked around it with a local.d script and I don't remember what turns relatime on.

#!/bin/bash

# Disable relatime=temporary on pool rootfs
ROOTFS=$(zpool get -o value -H bootfs)

zfs set relatime=off $ROOTFS

[beren12]

I believe the summary for your issue is: it doesn't matter. If atime is off, relatime has no meaning, because it is also off.

[ghfields]

@kpande You are right. It acts as relatime=on. Confirmed on Ubuntu 18.04 rpool exhibiting the relatime temporary issue. Of course it returned to noatime after issuing "mount -o remount -o noatime /"

[rlaager]

Basically, we need to revive #7948, support the other mount options, and extend that to the initramfs.

[quicktrick]

I confirm the issue on Void Linux. I used the workaround suggested by @bunder2015 : I added to /etc/rc.local the following command:

zfs set relatime=off $(zpool get -o value -H bootfs)

[bghira]

i submitted a fix but no one wanted it:

index 23c07af9e86..9bf80e14599 100755
--- a/contrib/dracut/90zfs/zfs-lib.sh.in
+++ b/contrib/dracut/90zfs/zfs-lib.sh.in
@@ -74,14 +74,22 @@ import_pool() {
 # mount_dataset DATASET
 #   mounts the given zfs dataset.
 mount_dataset() {
-        dataset="${1}"
+    dataset="${1}"
     mountpoint="$(zfs get -H -o value mountpoint "${dataset}")"
-
+    mountopts="strictatime"
+    ATIME_OPTION=$(zfs get -H -o value -s default,local,inherited atime ${dataset})
+    if [ "${ATIME_OPTION}" = "off" ]; then
+        mountopts="noatime"
+    fi
+    RELATIME_OPTION=$(zfs get -H -o value -s default,local,inherited relatime ${dataset})
+    if [ "${RELATIME_OPTION}" = "on" ]; then
+        mountopts="relatime"
+    fi
     # We need zfsutil for non-legacy mounts and not for legacy mounts.
     if [ "${mountpoint}" = "legacy" ] ; then
-        mount -t zfs "${dataset}" "${NEWROOT}"
+        mount -t zfs -o ${mountopts} "${dataset}" "${NEWROOT}"
     else
-        mount -o zfsutil -t zfs "${dataset}" "${NEWROOT}"
+        mount -o zfsutil -t zfs -o ${mountopts} "${dataset}" "${NEWROOT}"
     fi
 
     return $?

correction: it was viewed as a good idea, but people asked for waaaayyyy too many out-of-scope changes, so I withdrew the PR and said anyone could take the work up who wanted / needed it fixed. I've been maintaining my own local patch for this purpose.

[bghira]

@rlaager assigned it to himself and then did nothing with it, must have forgotten.

[rlaager]

That patch looks reasonable.

1. I'm not sure why the -s default,local,inherited.
2. I'm not sure how the mounting in _mount_dataset_cb() fits into this. Does that need to be modified too?
3. Theoretically, we should support other mount options. The list is: zfs list -H -o atime,relatime,devices,exec,readonly,setuid,nbmand That said, I realize that at least exec,readonly,setuid are extremely unlikely to be anything but defaults on the root fs. Though if we are mounting children (see 2 above), that could be different.
4. This is for dracut. We need support in initramfs too. I'm in a position to test that piece, so I can handle that piece if dracut is done.

This is probably what you meant by the change requests?