Re: Access FFS partition on GPT on ZVOL

[Staffan Thomén <staffan%shangtai.net@localhost>]

Being a curious person, and because this might let me avoid the zvol 
patch (and I now have a spare system to test these things on), I tried 
it too:

surtr# uname -a
NetBSD surtr 9.3 NetBSD 9.3 (GENERIC) #0: Thu Aug  4 15:30:37 UTC 2022 
mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

surtr# zfs create -V 1G tank/export

surtr# cat <<EOF>> /etc/iscsi/targets:
extent0         /dev/zvol/rdsk/tank/export      0               1024MB
target0=surtr.export    rw      extent0         0.0.0.0/0
EOF
surtr# /etc/rc.d/iscsi_target onestart

(initialize and create filesystem on windows client, add a file for good 
measure)

surtr# dmsetup create exportdm --table "0 1073741824 linear 
/dev/zvol/dsk/tank/export 0"

surtr# gpt -m 1073741824 -s 512 show /dev/mapper/rexportdm
    start     size  index  contents
        0        1         PMBR
        1        1         Pri GPT header
        2       32         Pri GPT table
       34    32734      1  GPT part - Windows reserved
    32768  2060288      2  GPT part - Windows basic data
  2093056     4063         Unused
  2097119       32         Sec GPT table
  2097151        1         Sec GPT header

gpt wouldn't let me show unless I specified -m and -s, perhaps 
setgeometry would make that work.

and then... no way of getting at the partitions that I could think of.

surtr# dkctl /dev/mapper/exportdm addwedge xxx 32768 2060288 NTFS
dkctl: /dev/mapper/exportdm: addwedge: Inappropriate ioctl for device

surtr# ccdconfig -c ccd0 0 /dev/mapper/exportdm 


ccdconfig: ioctl (CCDIOCSET): /dev/rccd0d: Invalid argument

Staffan