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

[Andriy Gapon]

on 16/04/2012 16:56 John Baldwin said the following:
> 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).

I hope that you will :-)

We already have a flag for ZFS (KARGS_FLAGS_ZFS, 0x4).  So the new flag could be
named something ZFS-specific (as silly as KARGS_FLAGS_ZFS2) or something more
general such as KARGS_FLAGS_32_BYTES meaning that the total size of arguments
area is 32 bytes (as opposed to 24 previously).


-- 
Andriy Gapon