zfs mount doesn't support "-O" and "-v" options

[marcin-github]

zfs mount -a -v doesn't display progress of mounting filesystems.
"-O" is unknown option:

# zfs mount -v -O zserwerek/tmp
invalid option 'O'
usage:
        mount
        mount [-vO] [-o opts] <-a | filesystem>

For the property list, run: zfs set|get

For the delegated permission list, run: zfs allow|unallow

[schakrava]

I verified the overlay behavior in Solaris. When you mount -O, and the mountpoint for the dataset already mounted a different dataset, the command unmounts the currently mounted dataset and mounts the dataset in the command input. This is the default behavior in Linux, without requiring -O option. So my question is should we just remove this default feature from the man page?

[marcin-github]

Hmm, i've expected "-O" option allow me to mount dataset on non empty directory (without using mountpoint=legacy).

[schakrava]

I understand the problem now, i think.

# zfs create -o mountpoint=/data/fs1 zpool0/fs1
# touch /data/fs1/test.txt
# ls /data/fs1/
test.txt

so far so good. now create a new dataset with the same mountpoint

# zfs create zpool0/fs2
# zfs set mountpoint=/data/fs1 zpool0/fs2

still only fs1 should be mounted

# zfs mount
zpool0/fs1                      /data/fs1

now try to mount fs2

# zfs mount zpool0/fs2
cannot mount '/data/fs1': directory is not empty

lets try overlay mount

# zfs mount -O /data/fs2
invalid option 'O'
usage:
    mount
    mount [-vO] [-o opts] <-a | filesystem>

For the property list, run: zfs set|get

For the delegated permission list, run: zfs allow|unallow

Where as, the above does not fail in solaris and does what you expect. Are we on same page with problem description?

[marcin-github]

We are but i tried to mount dataset on non empty ext4 directory ( i didn't try mount on other zfs dataset). I didn't test it on solaris, i tried on freebsd. I didn't have to even use "-O" option to mount on non empty directory (tried ufs and zfs).

[dajhorn]

ZoL won't use a non-empty mount point by design. See the second bullet in issue #274.

[schakrava]

I've submitted a pull request for this. Hopefully, the consensus is to support the -O option.

[behlendorf]

Supporting -O which is in the man page and exactly preserves the Solaris behavior seems entirely appropriate to me. We could always diverge like FreeBSD did but I'd prefer not too. People familiar with Solaris have certain expectations about how zfs behaves as should try and honor that as much as possible.

@schakrava I've merged your patch as commit e18be9a

[marcin-github]

Works for me, many thanks for patch!