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Re: [libvirt] [PATCH 1/2] resize: add virStorageVolResize() API



On Mon, Jan 30, 2012 at 08:23:36AM -0700, Eric Blake wrote:
> On 01/30/2012 07:28 AM, Daniel P. Berrange wrote:
> >>>> Why has this changed from 'unsigned long long' to just 'long long'.
> >>>
> >>> Because of VIR_STORAGE_VOL_RESIZE_DELTA and
> >>> VIR_STORAGE_VOL_RESIZE_SHRINK.  That is,
> >>>
> >>> virStorageVolResize(vol, -10 * 1024 * 1024, DELTA|SHRINK)
> >>>
> >>> is a valid call to shave off 10 MiB of data.
> >>
> >> Isn't that rather redundant. Either you need a negative size, or you
> >> need a SHRINK flag. If you have a shrink flag, then we don't need a
> >> signed int.
> > 
> > In fact since our existing  virDomainBlockResize API is already
> > using unsigned long long, I'd say we should do shrinkage solely
> > based off  the SHRINK flag, and *not* require a negative size
> > as well
> 
> Here's what I was envisioning:
> 
> set my size to an absolute of 10M, regardless of whether it was
> previously 5M or 15M:
> 
> virStorageVolResize(vol, 10*1024*1024, SHRINK)
> 
> set my size to an absolute of 10M, but only if it does not shrink:
> 
> virStorageVolResize(vol, 10*1024*1024, 0)
> 
> set my size to a relative of 10M larger
> 
> virStorageVolResize(vol, 10*1024*1024, DELTA)
> 
> set my size to a relative of 10M smaller, provided it was at least 10M
> to begin with:
> 
> virStorageVolResize(vol, -10*1024*1024, DELTA|SHRINK)
> 
> You are proposing that the negative sign should be implied by the
> combination of DELTA|SHRINK; I guess I can live with that, since the
> other three use cases still work as-is, and DELTA|SHRINK is the only
> point where a negative value makes sense (and therefore where implying
> the negative is okay).
> 
> Shall I go ahead and write the patch?

Yep, that would be good.

Daniel
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