[Libguestfs] [PATCH v5 REBASE 0/4] virt-resize: add support for resizing logical

[Richard W.M. Jones]

On Wed, Jan 28, 2015 at 02:24:15PM +0800, Hu Tao wrote:
> On Wed, Dec 17, 2014 at 03:07:11PM +0800, Hu Tao wrote:
> > On Thu, Oct 30, 2014 at 10:46:52AM +0800, Hu Tao wrote:
> > > Hi Rich,
> > > 
> > > This is rebase of v5 series. Meanwhile, I found a bug when shrinking
> > > partitions, and the fix is incuded in this version (patch 2).
> > 
> > Hi,
> > 
> > When support to resizing logical partitions is enabled, there is a
> > problem about resizing the extended partition: whether the extended
> > partition is automatically resized (expanded or shrunk) by virt-resize
> > based on the resizing of logical partitions?
> > 
> > All the cases can be categorized as these two:
> > 
> > 1. user doesn't explictly resize the extended partition. In this case it
> >    seems reasonable to automatically expand the extended partition as well.
> > 
> > 2. user explictly resizes the extended partition. If the extended
> >    partition is resized as user requested, then we should deal with the
> >    conflicts about resizing extended partition and logical partitions,
> >    this is somewhat tricky in the current implementation; But if the
> >    extended partition is automatically resized, user will be confused as
> >    the resulting size may be what he/she expects.
> 
> s/may be/may not be/
> 
> I think the best choice is:
> 
> 1. If user doesn't explictly resize the extended partition, then any
>    resizing (expanding or shrinking) of logical partitions will cause
>    the automatical resizing of the extended partition.
> 
> 2. If user explictly resize the extended partition, then any confliction
>    between resizing of the extended partition and logical partitions
>    will raise an error.
> 
> To achieve this, the patchset needs to be refactored heavily. So I'd
> like to hear suggestions before starting refactor.

Part of the problem I have with the original patch set is really
nothing to do with this user input question.  It's that the patches
don't model properly how the extended partition and logical partitions
actually work.  There is one partition which is nominated as the
extended partition (EP), and then logical partitions (LP) live inside
that EP.  At the moment we just have a list of partitions and list of
LPs.

(The other part is that these are still high risk patches that are
likely to break virt-resize than do anything useful.  It would IMO be
better to discourage people from using logical partitions in the first
place, especially since a good alternative -- GPT -- exists.)

Rich.

-- 
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