Re: [Qemu-block] [Qemu-devel] [PATCH v2] block: Turn on "unmap" in active commit

[Kevin Wolf]

Am 27.09.2016 um 13:04 hat Fam Zheng geschrieben:
> On Tue, 09/27 17:33, Fam Zheng wrote:
> > We already specified BDRV_O_UNMAP when opening images in 'qemu-img
> > commit', but didn't turn on the "unmap" in the active commit job. This
> > patch fixes that so that zeroed clusters in top image can be discarded
> > which is desired in the virt-sparsify use case, where a temporary
> > overlay is created and fstrim'ed before commiting back, to free space in
> > the original image.
> > 
> > This also enables it for block-commit.
> > 
> > Signed-off-by: Fam Zheng <address@hidden>
> > ---
> > v2: Add "unmap" to block-commit as well. [Kevin]
> > ---
> >  block/mirror.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/block/mirror.c b/block/mirror.c
> > index f9d1fec..8f6f506 100644
> > --- a/block/mirror.c
> > +++ b/block/mirror.c
> > @@ -1043,7 +1043,7 @@ void commit_active_start(const char *job_id, 
> > BlockDriverState *bs,
> >      mirror_start_job(job_id, bs, base, NULL, speed, 0, 0,
> >                       MIRROR_LEAVE_BACKING_CHAIN,
> >                       on_error, on_error, false, cb, opaque, &local_err,
> > -                     &commit_active_job_driver, false, base, 
> > auto_complete);
> > +                     &commit_active_job_driver, true, base, auto_complete);
> 
> I'm an idiot! I changed the wrong parameter (is_none_mode).

Actually, the idiotic part is having a function with eighteen
parameters. Not too surprising that someone confuses them sooner or
later...

Perhaps we could enable QAPI boxing for blockdev-mirror and then just
pass down a struct. Then we could have designated initialisers here in
commit_active_start() and it would be obvious if the wrong one is
changed.

Not something to do in this series, of course, just a general idea for
improvement.

Kevin