zpool split cannot open '/dev/sdc': Device or resource busy

[stroobandt]

My situation: I am running 0.6.0.65-0ubuntu1~precise1. I have a 3-way mirror with a filesystem tank/home that is mounted as /home with legacy. (Without legacy would not work, but that is a different bug.) So:

zfs list

NAME USED AVAIL REFER MOUNTPOINT
tank 369G 544G 30K /tank
tank/home 369G 544G 369G legacy

Problem:

zpool split tank backup /dev/sdc

always results in the following message:
cannot open '/dev/sdc': Device or resource busy

(I actually use /dev/by-id instead of /dev/sdc, but I left this out for clarity.)
Putting /dev/sdc offline works, but does not resolve this issue.
Manually umount /home does not work because device is busy.

[behlendorf]

This is likely because the device has been opened O_EXCL, this has slightly different behavior than on Solaris where it's just advisory. There are several other bugs like this which are being looked at.

[stroobandt]

Is there a convenient way to forcefully change this O_EXCL flag on the command line?
I find myself now using parted to delete partition tables in order to circumvent this...

[behlendorf]

This was fixed in 0.6.1 as a consequence of resolving the hot spares issues. See issue #250 commit 8128bd8.

[behlendo@centos-6-3-amd64 zfs]$ sudo zpool status -v
  pool: tank
 state: ONLINE
  scan: none requested
config:

        NAME            STATE     READ WRITE CKSUM
        tank            ONLINE       0     0     0
          mirror-0      ONLINE       0     0     0
            /tmp/vdev1  ONLINE       0     0     0
            /tmp/vdev2  ONLINE       0     0     0
            /tmp/vdev3  ONLINE       0     0     0

errors: No known data errors

[behlendo@centos-6-3-amd64 zfs]$ sudo zpool split tank backup /tmp/vdev3
[behlendo@centos-6-3-amd64 zfs]$ sudo zpool status -v
  pool: tank
 state: ONLINE
  scan: none requested
config:

        NAME            STATE     READ WRITE CKSUM
        tank            ONLINE       0     0     0
          mirror-0      ONLINE       0     0     0
            /tmp/vdev1  ONLINE       0     0     0
            /tmp/vdev2  ONLINE       0     0     0

errors: No known data errors
[behlendo@centos-6-3-amd64 zfs]$ sudo zpool import -d /tmp/
   pool: backup
     id: 13729394525721321345
  state: ONLINE
 action: The pool can be imported using its name or numeric identifier.
 config:

        backup        ONLINE
          /tmp/vdev3  ONLINE

[wq9578]

Same experience in current zfs-macOS-2.1.6-1 (maybe similar to moby/moby#24403).

A similar earlier attempt was, however, successful.

[user@host:~]% sudo zpool split testpool testpool3 /dev/disk2s1                              
cannot open '/dev/disk2s1': Resource busy
Unable to split testpool: Device list must include at most one disk from each mirror
[user@host:~]% sudo zpool split testpool testpool3 media-72A23CE3-[...]
cannot open '/private/var/run/disk/by-id/media-72A23CE3-[...]': Resource busy
Unable to split testpool: permission denied
[user@host:~]% zfs -V                       
zfs-macOS-2.1.6-1
zfs-kmod-2.1.6-1
[user@host:~]% brew info openzfs
==> openzfs: 2.1.6,432
https://openzfsonosx.org/
[...]