Updates on ZFS.

[Matt Olander]

Wow, that's impressive, Pawel. Nice work! We'll get to work testing :D

-matt

On Tue, Aug 10, 2010 at 1:03 PM, Pawel Jakub Dawidek <pjd at freebsd.org> wrote:
> Hi.
>
> For the past weeks I was working on getting recent ZFS to work. This is
> what I accomplished:
>
> 1. Fixed (implemented) onexit functionality that is now used by zfs
>   send/recv. This is based on device cloning in OpenSolaris, but I
>   manage to avoid using device cloning on FreeBSD and ended up using
>   cdevpriv, which is much less problematic.
>   This was the main reason ZFS in my tree didn't compile for quite a
>   while - I needed to find a way and time to implement it properly.
>
> 2. I manage to get ZVOLs to work again. Commit log for this change
>   should explain everything:
>
>   OpenSolaris switched to lazy creation of /dev/ entires for ZVOLs.
>   It creates /dev/ entries on VOP_LOOKUP() or VOP_READDIR().
>
>   This of course can't work this way on FreeBSD with GEOM, so we need
>   to create ZVOL providers where appropriate. I found the following
>   cases:
>   1. Pool first open (pool is loaded based on zpool/cache configuration
>      and is then opened for a first time on eg. zfs mount).
>   2. Pool import. It's not the same as 1.
>   3. ZVOL creation: zfs create -V<size> <zvol>.
>   4. Creation of ZVOL snapshot, this includes recursive snapshot
>      creation.
>
>   To make it work I had to fix LOR between the zfsdev_state_lock, the
>   GEOM topology lock and the spa_namespace_lock. They are now always
>   obtained in the following order:
>   1. zfsdev_state_lock
>   2. g_topology_lock
>   3. spa_namespace_lock
>   Also, we can't use taskqueue to scan for VDEVs as this introduces
>   deadlock (because there is no way to honour the order above).
>
>   This also allows to simplify vdev_geom.c quite a bit as it is no
>   longer a problem to taste ZVOL or ZVOL-based provider.
>
>   Update /etc/rc.d/zvol as there are no longer volinit and volfini
>   subcommands to zfs(8).
>
> 3. I integrated all the recent changes (including zfs diff and readonly
>   pools functionality). We are at v28 now and in sync with today's
>   OpenSolaris.
>
> 4. I fixed a handful of bugs.
>
> All in all, it compiles and at least basic functionality should work.
>
> --
> Pawel Jakub Dawidek                       http://www.wheelsystems.com
> pjd at FreeBSD.org                           http://www.FreeBSD.org
> FreeBSD committer                         Am I Evil? Yes, I Am!
>