zfs-mount ignores noauto for zvols in fstab

[gyakovlev]

System information

Type	Version/Name
Distribution Name	gentoo
Distribution Version	current
Linux Kernel	4.15.14-gentoo
Architecture	x86_64
ZFS Version	0.7.7-r0-gentoo
SPL Version	0.7.7-r0-gentoo

Describe the problem you're observing

zfs-mount initscript ignores noauto mount option for zvols

At this point I'm unsure why zfs-mount tries to handle zvols? Is there any kind of use-case I'm missing?
As it seems pretty much every distro out there should have their own subset of scripts/tools what handle regular block device fstab mounts.

I see 2 ways of dealing with the situation:

1. Remove zvol handling altogether. It's just regular block device and should be handled by existing toolset. It was around for decades and should handle all edge cases by now.
2. add an additional check for noauto field in fstab.

@loli10K mind if I ask for any comments on how will redhat6 handle it if we remove zvol handling from zfs-mount? will something else mount those volumes? my guess is yes, just want to confirm.

@everyoneelse any comments for other linux distros that use provided sysvinit scripts?

I only use gentoo, it will handle it just fine.

sidenote:
systemd services are fine atm.
every zvol fstab entry get's it's own service created by systemd-fstab-generator, and zfs-mount does not touch zvols at all.

Describe how to reproduce the problem

User has the following line in /etc/fstab

 # cat /etc/fstab
/dev/zvol/noauto/fs /noautofs any defaults,noauto 0 0	# should be filtered out but it's not

zfs-mount will mount it anyway

fsck "$dev" && mount "$mntpt"

All it takes to mount a filesystem marked with noauto is explicit mount call, exactly what initscript does.

Include any warning/errors/backtraces from the system logs

 # cat /etc/fstab
/dev/zvol/noauto/fs /noautofs any ro,noauto 0 0	# should be filtered out but it's not
/dev/zd1 /noautofs any ro,noauto 0 0	# should be filtered out but it's not

 # set -x
 # read_fstab "^/dev/(zd|zvol)" #that's how zfs-mount runs it
+ read_fstab '^/dev/(zd|zvol)'
+ local 'match=^/dev/(zd|zvol)'
+ local i var TMPFILE
++ env
++ grep --colour=auto '^FSTAB_'
++ sed 's,=.*,,'
+ unset
+ i=0
+ read -r fs mntpnt fstype opts
+ egrep --colour=auto -qE '^#|^$'
+ echo /dev/zvol/noauto/fs
+ echo /noautofs
+ egrep --colour=auto -qE '^none|^swap'
+ egrep --colour=auto -qE '^swap'
+ echo any
+ grep --colour=auto -qE '^/dev/(zd|zvol)'
+ echo '/dev/zvol/noauto/fs /noautofs any ro,noauto 0 0	# should be filtered out but it'\''s not'
+ eval export FSTAB_dev_0=/dev/zvol/noauto/fs
++ export FSTAB_dev_0=/dev/zvol/noauto/fs
++ FSTAB_dev_0=/dev/zvol/noauto/fs
++ printf '%b\n' /dev/zvol/noauto/fs
++ sed s,/,_,g
+ fs=_dev_zvol_noauto_fs
+ eval export FSTAB_0=/noautofs
++ export FSTAB_0=/noautofs
++ FSTAB_0=/noautofs
+ i=1
+ read -r fs mntpnt fstype opts
+ egrep --colour=auto -qE '^#|^$'
+ echo /dev/zd1
+ egrep --colour=auto -qE '^none|^swap'
+ echo /noautofs
+ egrep --colour=auto -qE '^swap'
+ echo any
+ grep --colour=auto -qE '^/dev/(zd|zvol)'
+ echo '/dev/zd1 /noautofs any defaults,noauto 0 0	# should be filtered out but it'\''s not'
+ eval export FSTAB_dev_1=/dev/zd1
++ export FSTAB_dev_1=/dev/zd1
++ FSTAB_dev_1=/dev/zd1
++ printf '%b\n' /dev/zd1
++ sed s,/,_,g
+ fs=_dev_zd1
+ eval export FSTAB_1=/noautofs
++ export FSTAB_1=/noautofs
++ FSTAB_1=/noautofs
+ i=2
+ read -r fs mntpnt fstype opts

 # env | grep FSTAB
FSTAB_1=/noautofs
FSTAB_0=/noautofs
FSTAB_dev_1=/dev/zd1
FSTAB_dev_0=/dev/zvol/noauto/fs

[gyakovlev]

taking closer look it seems that there are even more issues:

1. mountpoint=legacy datasets are mounted regardless of canmount=noauto property
2. mountpoint=legacy datasets are mounted regardless of fstab noauto
3. fsck being run for zvols regardless of fstab settings.

[stale]

This issue has been automatically marked as "stale" because it has not had any activity for a while. It will be closed in 90 days if no further activity occurs. Thank you for your contributions.

[omnivagant]

Still a number of issues here. I found that zfs-mount doesn't respect the sixth field in fstab entries being 0 or empty (which defaults to 0) and runs fsck anyway.