[parted-devel] [PATCH 2/6] libparted: handle busy extended partition

Petr Uzel petr.uzel at suse.cz
Tue Oct 16 12:38:19 UTC 2012


On Mon, Oct 15, 2012 at 10:11:16AM -0400, Phillip Susi wrote:
> On 10/15/2012 4:31 AM, Petr Uzel wrote:
> > When parted encounters busy partition during its loop for informing
> > the kernel about partition changes, it tries to compare geometry of
> > the to-be created partition with the geometry of the existing
> > partition (reported by the kernel). If these geometries match,
> > there is nothing more to do for parted.
> > 
> > However, this fails for msdos extended partitions, because kernel 
> > always reports size of extended partition to be 2s, no matter how 
> > big it actually is (to avoid having overlapping partitions in the 
> > kernel's representation of partition table). This makes the 
> > comparison of geometries to fail for extended partitions, so they 
> > need to be handled specially.
> 
> Isn't this a bit of a contrived case?  

It is not. In fact, one of our (SUSE) customers has been recently hit
by this. I don't know yet which program on the customers system caused
this (some hal* would be my guess).

> I mean in practice, an extended
> partition should never be in use.  IIRC, the only reason the kernel
> even creates the extended partition is to allow lilo to install itself
> there easily, outside of that, nobody ever opens them.

I agree nothing should ever open extended partition, but in reality
you can not guarantee that.

> What happens if the old partition was NOT an extended partition, but
> the new one is?  In other words, we are removing a primary partition
> and replacing it with a primary that starts in the same place?  Then
> wouldn't this change prevent parted from complaining that it couldn't
> make the change if the partition is in use?

Isn't this a bit of a contrived case? :)
No, really, good point - I'll try to reproduce this scenario and check
what can be done about it.

Thanks for the review,

Petr

-- 
Petr Uzel
IRC: ptr_uzl @ freenode
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