[parted-devel] [patch] Use 'p' partition separator only when necessary

[Jim Meyering]

Phillip Susi wrote:
> On 3/11/2011 4:04 PM, Jim Meyering wrote:
>> Thanks for the patch.
>>
>> This sounds like a good change.
>> However, can you give a little more detail?
>> Does parted's current behavior induce failure in some other tool?
>> What's the motivation?
>>
>> And especially, can you write a test for it, or at least
>> outline a quick procedure for demonstrating how this changes
>> parted's behavior (in which case I'll write it)?
>
> It seems that the behavior was copied from dmraid, which decided a while
> back to start adding the 'p' always.  Debian and Ubuntu have been
> carrying a patch to reverse that change to both dmraid and parted.
> Initially I got that patch dropped in Ubuntu during the Natty
> development cycle because we want to avoid diverging from upstream, and
> if the base device name ends in a digit, then you NEED the 'p' or
> various tools get confused about what is the disk name and what is the
> partition name.
>
> This then lead me to gparted causing a problem.  It had code to handle
> dmraid devices specially from before libparted could, and it was
> invoking dmraid to create the partition devices, and explicitly telling
> it not to add the 'p'.  This meant that a duplicate partition device was
> created, without the 'p' in the name ( /dev/mapper/RAID1 and
> /dev/mapper/RAIDp1 ).  Having two devices for the same partition is very
> bad.  You can end up doing things like delete the partition while it is
> mounted and reuse its space in another partition, because the checks to
> see if the partition are mounted do not know about the duplicate device.
>
> After speaking with the gparted maintainer, he has provided a configure
> switch to disable the gparted dmraid handling code and leave it up to
> libparted, which solves the duplicate device problem.  During that
> discussion I also learned that the kpartx tool which some distributions
> use to create the partition devices instead of dmraid only adds the 'p'
> if the previous character is a digit.  Further discussion on mailing
> lists indicated that this is the correct behavior that Linux has used
> "since the dawn of time".

Can you give a reference to that discussion?