Re: [Qemu-devel] [PATCH v12 1/2] mirror: Rewrite mirror_iteration

[Jeff Cody]

On Feb 14, 2016 21:19, "Fam Zheng" <address@hidden> wrote:
>
> On Mon, 02/08 13:54, Max Reitz wrote:
> > On 07.02.2016 13:46, Fam Zheng wrote:
> > > On Sat, 02/06 14:24, Max Reitz wrote:
> > >> On 05.02.2016 03:00, Fam Zheng wrote:
> > >>> The "pnum < nb_sectors" condition in deciding whether to actually copy
> > >>> data is unnecessarily strict, and the qiov initialization is
> > >>> unnecessarily for bdrv_aio_write_zeroes and bdrv_aio_discard.
> > >>>
> > >>> Rewrite mirror_iteration to fix both flaws.
> > >>>
> > >>> The output of iotests 109 is updated because we now report the offset
> > >>> and len slightly differently in mirroring progress.
> > >>>
> > >>> Signed-off-by: Fam Zheng <address@hidden>
> > >>> ---
> > >>>  block/mirror.c             | 335 +++++++++++++++++++++++++++------------------
> > >>>  tests/qemu-iotests/109.out |  80 +++++------
> > >>>  trace-events               |   1 -
> > >>>  3 files changed, 243 insertions(+), 173 deletions(-)
> > >>>
> > >>> diff --git a/block/mirror.c b/block/mirror.c
> > >>> index 2c0edfa..48cd0b3 100644
> > >>> --- a/block/mirror.c
> > >>> +++ b/block/mirror.c
> > >>
> > >> [...]
> > >>
> > >>> @@ -449,16 +520,16 @@ static void coroutine_fn mirror_run(void *opaque)
> > >>>       */
> > >>>      bdrv_get_backing_filename(s->target, backing_filename,
> > >>>                                sizeof(backing_filename));
> > >>> -    if (backing_filename[0] && !s->target->backing) {
> > >>> -        ret = bdrv_get_info(s->target, &bdi);
> > >>> -        if (ret < 0) {
> > >>> -            goto immediate_exit;
> > >>> -        }
> > >>> -        if (s->granularity < bdi.cluster_size) {
> > >>> -            s->buf_size = MAX(s->buf_size, bdi.cluster_size);
> > >>> -            s->cow_bitmap = bitmap_new(length);
> > >>> -        }
> > >>> +    if (!bdrv_get_info(s->target, &bdi) && bdi.cluster_size) {
> > >>
> > >> This should be bdi.has_cluster_size...
> > >
> > > has_cluster_size is a member of ImageInfo not BlockDriverInfo, and is derived
> > > from (bdi.cluster_size != 0).
> >
> > You're right, my bad.
> >
> > >>> +        target_cluster_size = bdi.cluster_size;
> > >>
> > >> ...and maybe we want an explicit minimum of BDRV_SECTOR_SIZE here; but I
> > >> guess this is already assumed all over the block layer, so it may be
> > >> fine without.
> > >
> > > Okay, it doesn't hurt to add an assert here.
> >
> > I'd be happy to take the patch without, too (although I wouldn't decline
> > a follow-up adding an assertion).
> >
> > Reviewed-by: Max Reitz <address@hidden>
>
> Thanks! Shall we merge this now?
>
> Fam
>

I think so - I'll go ahead and apply it to my block branch, unless there are any objections.

Jeff