Re: gptzfsboot grew a lot after skein support was added; need knob to control bloat

On 28/1/17 1:35 am, Allan Jude wrote:
> On 2017-01-27 12:33, Shawn Webb wrote:
>> On Fri, Jan 27, 2017 at 12:30:17PM -0500, Allan Jude wrote:
>>> On 2017-01-27 12:05, Warner Losh wrote:
>>>> On Fri, Jan 27, 2017 at 12:34 AM, Toomas Soome <tsoome_at_me.com> wrote:
>>>>>> On 27. jaan 2017, at 1:40, Ngie Cooper (yaneurabeya) <yaneurabeya_at_gmail.com> wrote:
>>>>>>
>>>>>> Hi,
>>>>>>        I tried upgrading one of my workstations and unfortunately the freebsd-boot partition is too small (I follow manpage directions, exactly, and those seem to be too small as of 10.3-RELEASE timeframe), and I don???t have enough space or ability to resize the partition and make it bigger. So, I???m in need of a build knob to control the bloat, and/or having an alternative boot loader without geli/skein/crypto support compiled in. Would you be opposed to the work?
>>>>>> Thanks,
>>>>>> -Ngie
>>>>>
>>>>> I do agree that since the geli knob is already there, it may do. Of course we also can think of additional knobs, but there is an issue - it wont help just to exclude some files, the additional features also do sit in the code, so the replacement stubs will be needed, also testing them all over will take some time. And the preprocessor spaghetti really is nasty thing to deal with;)
>>>>>
>>>>> And then there is another issue (partly why I did the feature support in first place) - as the kernel does not block user from enabling the features, the user can end up facing non-bootable setup which is also not good, as user is using perfectly legal options, and still the whole thing is just rendered unusable???
>>>> I'm curious why you can't find the space for a bigger partition?
>>>> Almost all drives these days are partitioned with a little wasted
>>>> space, and that wasted space should be more than enough to cover us
>>>> here. Also, most drives have a swap partition that can be shrunk a
>>>> trivial amount to get space for this...
>>>>
>>>> Warner
>>>>
>>> I need to do some testing to make a recipe that works for it, but the
>>> other option is to use the ZFS bootcode area.
>>>
>>> ZFS it self, reserves something like 3.5 mb of space in the ZFS
>>> partition, for boot code. This is how we boot ZFS on MBR.
>>>
>>> It should be possible to use this on GPT as well, we just don't.
>> In the future, maybe it'd be a good idea for the installer to leave
>> more space (a few MB, perhaps?) between the freebsd-boot and
>> freebsd-swap partitions? At least, for ZFS installs.
>>
>> Thanks,
>>
> The PMBR code has a limitation for 536kb, and it all has to fit under
> the 640k barrier, so the current 512kb size is plenty. The issue is some
> people are upgrading from systems that were isntalled long ago, when
> 64kb or less was the default.
>
with 512K we can append a copy of FreeBSD1.0 on the end of the 
bootblock and leave us the option of bringing up a networked NFS based 
system for debugging.

maybe we could fall back to that after a crash...