Unable to access snapshots on datasets listed in ZFS_INITRD_ADDITIONAL_DATASETS under .zfs/snapshot/...

[m-ueberall]

System information

Type	Version/Name
Distribution Name	Ubuntu
Distribution Version	20.04 LTS ("Focal")
Linux Kernel	5.4.0-65-generic
Architecture	x86_64
ZFS Version	2.0.1-1, 2.0.2-1
SPL Version	2.0.1-1, 2.0.2-1

Describe the problem you're observing

Accessing snapshots on datasets listed in ZFS_INITRD_ADDITIONAL_DATASETS under .zfs/snapshot/... is not possible; the only workaround is to explicitly mount them using "mount -zfs <snapshot> <directory>".
This does not affect the rpool/ROOT/ubuntu_XXXXXX dataset hierarchy (using zstd compression/encrypted) nor bpool/BOOT/ubuntu_XXXXXX (lz4 compression/unencrypted, mounted using zfs-import-bpool.service as adopted from the Root on ZFS tutorials for both Ubuntu, Debian).

(This looks similar to Issue #9461, but given that I get different error messages and use ZFS_INITRD_ADDITIONAL_DATASETS, this might warrant a separate issue.)

Describe how to reproduce the problem

Just try to access a snapshot on a dataset (either created locally or received from elsewhere) as described above.

Resulting errors differ (note that the second snapshot below has been created locally despite the error message; there are also "zfs-auto-snap" snapshots elsewhere which show the first error upon access, no identifiable pattern here):

[2021-02-03T11:06:08+0100] root@vserver17:/mirrored/gluster# ls -l .zfs/snapshot                                                       [rc:0/shlvl:1]
total 0
drwxrwxrwx 2 root root 2 2021-02-02 20:43:06 ./
drwxrwxrwx 1 root root 0 2021-02-02 20:35:42 ../
drwxrwxrwx 1 root root 0 2021-02-03 11:06:11 20201201-001/
drwxrwxrwx 1 root root 0 2021-02-03 11:06:11 zfs-auto-snap_hourly-2021-02-02-1943/
[2021-02-03T11:06:11+0100] root@vserver17:/mirrored/gluster# ls -l .zfs/snapshot/20201201-001/
ls: cannot access '.zfs/snapshot/20201201-001/': Too many levels of symbolic links
[2021-02-03T11:06:47+0100] root@vserver17:/mirrored/gluster# ls -l .zfs/snapshot/zfs-auto-snap_hourly-2021-02-02-1943/
ls: cannot access '.zfs/snapshot/zfs-auto-snap_hourly-2021-02-02-1943/.': Object is remote
ls: cannot access '.zfs/snapshot/zfs-auto-snap_hourly-2021-02-02-1943/..': Object is remote
total 0
d????????? ? ? ? ?                   ? ./
d????????? ? ? ? ?                   ? ../
[2021-02-03T11:06:53+0100] root@vserver17:/mirrored/gluster#

Include any warning/errors/backtraces from the system logs

(I don't see any.)

[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.

[m-ueberall]

Update: The first error message (Too many levels of symbolic links) is still reproducible on the same set of machines using current versions of both kernel and OpenZFS packages (directly built from this repository):

Type	Version/Name
Linux Kernel	5.14.0-1022-oem
ZFS Version	2.1.2-1
SPL Version	2.1.2-1

[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.

[m-ueberall]

Update: The first error message (Too many levels of symbolic links, see above) is still reproducible on Ubuntu 20.04 using the following packages on the same set of machines:

Package	Version	Repository
linux-image-5.15.0-66-generic	5.15.0-66.73~20.04.1	focal-proposed
libzfs5, libzfs5-devel, python3-pyzfs, zfs, zfs-dkms, zfs-initramfs	2.1.9-1	(built from this project)