kern/57583: zpool import will not find pools on disklabel partitions

[abs%absd.org@localhost]

>Number:         57583
>Category:       kern
>Synopsis:       zpool import will not find pools on disklabel partitions
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Aug 13 17:00:00 +0000 2023
>Originator:     David Brownlee
>Release:        netbsd-10
>Organization:
>Environment:
NetBSD forsaken.absd.org 10.0_BETA NetBSD 10.0_BETA (GENERIC) #0: Fri Aug  4 19:55:08 UTC 2023  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

>Description:
zpool import only appears to check top level devices - dk0, wd0 etc, not partitions.

I had a single partition zpool using latter part of a disk (wd3e) - I know this is generally discouraged but I needed the space to shuffle things around and I wanted to keep all the data on zfs.

Once created the zpool will happily persist, but if "zpool export"ed, it cannot be imported, unless a new directory is created which contains the necessary partition devices but not the zfs devices:

# zpool export onyx3

# zpool import onyx3
cannot import 'onyx3': no such pool available

# zpool import -d /dev onyx3
cannot import 'onyx3': no such pool available

# mkdir /tmp/dev ; ( cd /tmp/dev ; /dev/MAKEDEV wd3 ) ; zpool import -d /tmp/dev onyx3

# disklabel wd3| tail -6
5 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a: 419430400      2048       RAID                     # (Cyl.      2*- 416103*)
 c: 3907027120      2048     unused      0     0        # (Cyl.     2*- 3876020)
 d: 3907029168         0     unused      0     0        # (Cyl.      0 - 3876020)
 e: 3487596720 419432448        ccd                     # (Cyl. 416103*- 3876020)
>How-To-Repeat:
Try to import a zfs pool with one or more components on a disklabel partition
>Fix: