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On Sat, Oct 18, 2003 at 02:55:29AM -0400, Ted Unangst wrote:
> On Fri, 17 Oct 2003, Bill Studenmund wrote:
>=20
> > > one possible concern is that this approach is very ffs-centric.
> >=20
> > How so? i.e. who has this as a concern?
>=20
> let me elaborate.  personally, i think fs parameters should be entirely=
=20
> separate from the partition.

Ahhh...

> > The purpose of the ioctl is so that newfs and all the other file system=
=20
> > generators don't have to bother with a disklabel. They just know they h=
ave=20
> > a partition, and get/set info about it.
>=20
> there are only two pieces of information that i think matter at the=20
> partition level.  size and fs type.  size because it's an inherent=20
> property of the partition, independent of fs.  type because it saves the=
=20
> trouble of iterating around looking for magic numbers (and no false=20
> matches).
>=20
> anything else belongs in the file system itself (superblock).  if a fs=20
> exists, the superblock is obviously the definitive record and the=20
> "outside" information doesn't matter.  if no fs exists yet, the fs=20
> generator should be able to guess/generate/ask for sane values.
>=20
> you've convinced me you will need an ioctl to get/set all this extra info=
. =20
> you haven't convinced me this info should be stored outside the fs. :)
> for the record, i don't think this info belongs in the disklabel either. =
=20
> i think a better location for it all would be something like /etc/fstab=
=20
> (/etc/partitions perhaps) if you think it's important.

You're assuming you can find the superblock. The information is in the=20
disklabel specifically in case the primary superblock is damaged, so that=
=20
you can figure out where to find the secondary superblocks. I think I've=20
only needed this once or twice. But in those cases, I've needed it.

/etc/partitions is bad for two reasons. First, how do you use it to fix=20
the root file system? Second, disks can move around. How do you ensure=20
that the /etc/partitions info for a disk move with it?

Take care,

Bill

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