Re: [RFC] Separating out libata out of SCSI (finally)

["Greg Freemyer" <greg.freemyer@gmail.com>]

On Tue, Jun 24, 2008 at 10:42 AM, James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
> On Tue, 2008-06-24 at 11:30 +0300, Boaz Harrosh wrote:
>> James Bottomley wrote:
>> > On Mon, 2008-06-23 at 17:04 -0400, Greg Freemyer wrote:
>> >> I've seen a lot of end user complaints about libata only supporting
>> >> 15(14?) partitions.  Will that limit be moved back to the traditional
>> >> drivers/ide limit as part of this?
>> >
>> > Number of partitions is directly related to number of minors, so it
>> > can't be changed without a change in the allocation of major/minor space
>> > in sd ... that could only be done compatibly by permuting the space.
>> > The only other way to do it is incompatibly by changing major (again).
>> >
>> Could we do both? I mean use the legacy, up to 15, with the old major,
>> then use the new major for bigger then 15. Since user mode that knows
>> about more then 15 partitions is new, it'll know it needs to jump a major.
>
> Not simultaneously, which is the problem; you can't have two separate
> block devices for the same physical device unless you want aliasing
> issues in the page cache.
>
> It might be possible to add an extra device to give access to the
> missing partitions, but that would require a bit of re-engineering in
> gendisk (which is the in-kernel code to manage the partitions).
>
> What might be far more feasible is to set up udev to use kpartx to
> provide the missing partitions if it detects a partition table that has
> them ... of course, that requires a udev setup and most of the
> complaints about the lost partitions seem to come from non-udev systems.
>
> But .... if everyone (particularly the people with these problems) had
> udev, we could simply migrate to a new major with more partitions, get
> udev to fix it all up for us and everyone would be happy because no-one
> would even notice that we'd moved majors ...
>
> James

>From my limited perspective, every complaint I've seen was related to
OpenSUSE which I believe is a udev based distro, so addressing this
for the udev based distros would address that contingent of users.

Greg
-- 
Greg Freemyer
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
First 99 Days Litigation White Paper -
http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf

The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com