[linux-lvm] LVM non-bug: md10 and higher broken

[Heinz J . Mauelshagen]

On Mon, Feb 04, 2002 at 08:52:53AM -0000, William Blunn wrote:
> Doesn't seem to be a bug in LVM, but it seems that the problem is
> tickled when migrating from a multiple-MD-devices system to an LVM
> system.
> 
> LVM 1.0.1 / kernel 2.2.20
> 
> I am using /dev/md0 through /dev/md10 for my existing (non-LVM) system.
> 
> I put in additional disks, set them up on /dev/md11, and created a PV on
> /dev/md11.
> 
> When trying to create the VG, it wouldn't find the PV.
> 
> Suspiciously, /proc/partitions shows MD devices listed as
> 
>    ...
>    /dev/md8
>    /dev/md9
>    /dev/md:
>    /dev/md;
> 
> instead of what you would expect
> 
>    ...
>    /dev/md8
>    /dev/md9
>    /dev/md10
>    /dev/md11
> 
> i.e. (sloppily) implemented as translating the MD number into a single
> character instead of generating a (potentially multiple character)
> string of the decimal representation.
> 
> Swapping /dev/md0 with /dev/md11 makes it all work.
> 
> So I guess that LVM is accessing /proc/partitions and not seeing any MD
> devices 10 or higher.

Yes, it does.
BTW: we don't support 2.2 any longer :-(

> 
> That would make it a bug in the kernel, but since people are likely to
> come across it through LVM I thought it would be a good idea to mention
> it here.

Could you send a request to fix (or even better a fix ;-) for MD
/proc/partitions/supprt to linux-kernel at vger.kernel.org, please?

> 
> Does anyone know if anyone has made/submitted a (2.2) kernel fix for
> this?

No, don't know.

> 
> Another little snag is that the code for handling this is right next to
> where the LVM patch gets applied, so making a patch would likely (I
> guess) make the LVM patch not apply properly.

That's likely.

> 
> Bill
> 
> 
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-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen at Sistina.com                           +49 2626 141200
                                                       FAX 924446
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