[review request] zfsboot/zfsloader: support accessing filesystems within a pool

[John Baldwin]

On Saturday, April 14, 2012 1:35:35 pm Andriy Gapon wrote:
> on 14/04/2012 18:37 Andriy Gapon said the following:
> > 
> > I would like to ask for a review and/or testing of the following three patches:
> > http://people.freebsd.org/~avg/zfsboot.patches.diff
> > 
> > These patches add support for booting from an arbitrary filesystem of any
> > detected ZFS pool.  A filesystem could be selected in zfsboot and thus will
> > affectfrom where zfsloader would be loaded.  zfsboot passes information about
> > the boot pool and filesystem to zfsloader, which uses those for loaddev and
> > default value of currdev.  A different pool+filesystem could be selected in
> > zfsloader for booting kernel.  Also if vfs.root.mountfrom is not explicitly set
> > and is not derived from fstab, then it gets set to the selected boot filesystem.
> 
> A note for prospective testers: the patched loader expect to be started by the
> patched zfs boot as it passes an additional parameter for a filesystem guid.
> I should probably add some way to distinguish between the older and newer zfs
> boot blocks.  Maybe an extra bit in bootflags?  What do you think?

An extra bit (similar to existing flags for detecting PXE and CD booting)
sounds fine to me.  (Note, I'm only replying to the question, have not looked
at patches yet).

-- 
John Baldwin