partition store type?

[Marcus Brinkmann]

Hi,

Neal and I thought a bit about partition fs and root file systems.
The root filesystem can't use the service of any partfs translator.
So it has to get the store in some different way.

One idea was to get GRUB to pass the blocklist to the root fs (and use the
remap store type in servers.boot).
Another idea is to link all bootstrapping filesystems with a libpartition
and let them use that to get the file list; this would still require a
naming scheme for partitions.

But then it occured to us that we can just use this naming scheme for
another store type, `partition', and link libstore to the libpartition.

Like this:
settrans /mnt /hurd/ext2fs partition:hd2/5

This would allow us to get partitions even with neither a partfs translator
in /dev, nor Mach support for partitions. It would not require any changes
in the store using filesystems (bootstrap or not) and it would allow the partfs
translator to provide a tree of storeio translated nodes like usermux does:

# showtrans /dev/hd0/5
/hurd/storeio partition:hd0/5

partition can be a straightforward extension of the device store: If there
is no partition name, just the device, like hd0 (or, let's say hd0s5 as long
as Mach provides those), it could forward the device store without
remapping. So the partition store type could be made the default (rather
than the device type) if we want.

At some point, we would have to change the default servers.boot (probably
kill the -T option or replace it with -Tpartition). When people start
to use a new mach with partition support ripped out, they will have to
pass something like root=hd0/5 in GRUB (or we could provide a compatible
parser which reads hd0s5 as hd0/5).

Marcus & Neal