Re: turning off COMPAT_386BSD_MBRPART in disklabel

[David Holland <dholland-tech%netbsd.org@localhost>]

On Mon, Jan 31, 2011 at 05:40:20PM +0100, Matthias Drochner wrote:
 > > PR 44496 notes that COMPAT_386BSD_MBRPART is still enabled in
 > > disklabel(8), even though it was turned off by default in the kernel
 > > early in 4.99.x. The PR also notes that it's not harmless to leave it
 > > on.
 > 
 > The PR rather leads to the conclusion that the support for
 > old Partition IDs in disklabel(8) is suboptimal.
 > Originally, the code did only consider a partition with the
 > old ID if no new one was found. This apparently got broken
 > when extended partition support was added years later.

Yeah, that's a valid point. I guess the question then is whether
fixing that will prevent any problematic cases from arising...  and
whether at this point it's worth worrying about.

I suspect very few commodity drives old enough to have been fdisk'd
with the old partition ID are still operable, and I suspect that
anyone who's got one that hasn't been updated already is qualified to
run fdisk... and there are very few cases where anyone would need to
run disklabel but not be able to run fdisk first. So I'd really be
inclined at this point to just disable the feature.

...also, it's not entirely clear to me what the code is supposed to be
doing if there are multiple NetBSD partitions; it looks as if what it
*will* do is use the label from the one it sees last and write the
same label to all of them.

blah, using both fdisk partitions and traditional labels on the same
disk has always been a pile of fail.

-- 
David A. Holland
dholland%netbsd.org@localhost