Re: [GIT PULL] (xen) stable/for-jens-3.2 - blkback and blkfront patches for 3.2

Konrad Rzeszutek Wilk
2011-09-22T16:36:50Z

On Thu, Sep 22, 2011 at 09:05:17PM +1000, Li Dongyang wrote:
> On Thursday, September 22, 2011, Konrad Rzeszutek Wilk <
> konrad.wilk@oracle.com> wrote:
> > On Wed, Sep 21, 2011 at 11:17:32AM -0400, Christoph Hellwig wrote:
> >> On Wed, Sep 21, 2011 at 11:09:55AM -0400, Konrad Rzeszutek Wilk wrote:
> >> > Hey Jens,
> >> >
> >> > Please pull the following git tree in your 3.2 drivers tree:
> >> >
> >> > git pull git://oss.oracle.com/git/kwilk/xen.git stable/for-jens-3.2
> >> >
> >> > which has an exciting new feature - the discard ('feature-discard')
> >> > aka TRIM/UNMAP. Now they can be passed from the guest to the backend.
> >>
> >> What is the design of them? Do you provide the 'discard zeroes data'
> >> flag (mandatory for any kind of relible operation) and 'discard
> >
> > Hmm, not sure what that is. Is that REQ_SECURE, err BLKDEV_DISCARD_SECURE?
> > If so then not in this patchset - but it does not seem like it would
> dificult
> > to add that in? Li, what do you think?
> We deal the discard with 2 ways in the backend depend on what the guest is
> using:
> punch the hole on the image, to save some disk usage,
> or redirect the discard request to phy device.
> for the hole punching case, we are already DISCARD_SECURE,
> for the phy dev case, we could add the flag and pass it from blkfront to
> blkback, and yes
> That's not difficult, could be added later.

Li, could you implement it please - on top of the 'stable/for-jens-3.2' patch queue ?
If it would not be too much trouble of course.

> >
> >> granularity / alignment' tunables (very useful)?
> >
> > The discard granularity/alignment are certainly there. But they are just
> > one way (backend tells the guest what they are). Should they be
> > more tunable (frontend tells the backend what the values ought to be?)
> >
> Yes, plz tell more about tunable granularity and alignment, and we can add
> that later,
> Thanks a lot
> > Li, did I miss anything in my response?
> >