Re: Changed names of logical disks on recent -CURRENT: part of logical disks not accessible now

On Dec 23, 2008, at 11:03 AM, gelraen wrote:

> 2008/12/23 Marcel Moolenaar <xcllnt_at_mac.com>:
>>
>>
>> I'm thinking about it. I have a couple of things
>> I need to do first, 7.1-RC2 being one of them...
>>
>
> I think, I can try to fix this if you give me couple advices (mostly
> about what code I should look and change)

All the code is under src/sys/geom/part.
o   g_part.c contains the high-level (abstract) code
     for partitioning.
o   g_part_mbr.c deals specifically with MBR.

> I spent some time in thinking about the best way to implement naming
> of extended partition.
> IMO, the only reasonable way is to sequentially numerate slices. So
> the result may look like this:
> ad0s3s1      ad0s3s2       ad0s3s3        ad0s3s4         
> ad0s3s5   ....

Well, the question is whether to expose the nesting
in the naming or use a flattened partition naming
scheme. Secondly, how generic do you want to make the
flattening.

With flattening, you have ad0sX, with X from 1 to many.
Without flattening you get ad0sX[sY...], with X and Y
from 1 to 4.

What you suggest is a partial flattening: adsXsY, with
X from 1 to 4 and Y from 1 to many.

The question of how generic you want to make it, relates
to having a BSD label under a MBR or a MBR under a GPT
and whether to flatten the namespace. As an example, you
can limit flattening for nested partitions of the same
type (i.e. same-scheme nesting).

> Main problem here is detecting which type of naming to use in  
> particilar case.

Exactly. This requires information exchange between level
X-1 to level X of the nesting. Such an exchange already
exists for example: the absolute sector offset of the
partition is passed from level X-1 to level X. So, it's
definitely doable.

In short: we just need to nail down what we're going to
fix, if we're going to fix anything, and understand the
consequences of our choice so that we can document it
or beter, avoid introducing new bugs in the process..

-- 
Marcel Moolenaar
xcllnt_at_mac.com